| 1. |
- Al-Saadi, Munir, et al.
(författare)
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A study of the static recrystallization behaviour of cast Alloy 825 after hot-compressions
- 2019
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596.
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Konferensbidrag (refereegranskat)abstract
- The static recrystallization behaviour of a columnar and equiaxed Alloy 825 material was studied on a Gleeble-3800 thermo-simulator by single-hit compression experiments. Deformation temperatures of 1000-1200 °C, a strain of up to 0.8, a strain rate of 1s-1, and relaxation times of 30, 180, and 300 s were selected as the deformation conditions to investigate the effects of the deformation parameters on the SRX behaviour. Furthermore, the influences of the initial grain structures on the SRX behaviors were studied. The microstructural evolution was studied using optical microscopy and EBSD. The EBSD measurements showed a relaxation time of 95 % for fractional recrystallization grains, ?95, in both structures, was less than 30 seconds at the deformation temperatures 1100 °C and 1200 °C. However, fewer than 95% of recrystallized grains recrystallized when the deformation temperature was lowered to 1000 °C. From the grain-boundary misorientation distribution in statically recrystallized samples, the fraction of high-angle grain boundaries decreased with an increasing deformation temperature from 1000 °C to 1200 °C for a given relaxation time. This was attributed to grain coarsening
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| 2. |
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| 3. |
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| 4. |
- Alekseeva, Ekaterina, et al.
(författare)
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Effect of Inclusions on the Corrosion Properties of the Nickel-Based Alloys 718 and EP718
- 2020
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 10:9
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Tidskriftsartikel (refereegranskat)abstract
- Inclusions in steels and alloys are known to lower the resistance to deformation, as well as to lower the mechanical, corrosion and other properties. Studies of inclusions in nickel-based alloys are important since these materials could suffer from corrosion degradation in harsh operational conditions. This, in fact, could lead to a pitting initiation around the inclusions. Two industrial Ni-based alloys (alloy 718 and EP718) were investigated to determine the harmful effects of different inclusions on the corrosion resistance of Ni-based alloys. Specifically, the inclusion characteristics (such as composition, morphology, size, number and location) were determined for inclusions collected on film filters after electrolytic extraction and dissolution of a metal matrix around different inclusions on surfaces of metal samples after electrolytic extraction (EE). It was found that both Ni-based alloys contain various inclusion types: carbides (large size NbTi-C and small multicomponent carbides), nitrides TiNb-N and sulphides (TiNb-S in EP718 alloy). The most harmful effects on the corrosion resistance of metal were detected around sulphides and small carbides containing Mo, W, Cr. Dissolution effects were also observed around large carbides and nitrides, especially around inclusions larger than 10 mu m. Moreover, the dissolution of a matrix around inclusions and clusters located on the grain boundaries were found to be 2.1-2.7 times larger compared to inclusions found inside of grains of the given alloy samples.
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| 5. |
- Bi, Yanyan, et al.
(författare)
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Evolution of Different Inclusions during Ladle Treatment and Continuous Casting of Stainless Steel
- 2013
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 53:12, s. 2099-2109
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Tidskriftsartikel (refereegranskat)abstract
- The inclusions and clusters in steel samples of two similar steel grades of high-silicon non-calcium treated (HSiNC) stainless steels were investigated and compared during ladle treatment and continuous casting. Samples of liquid steel and slag were taken at different stages of the ladle treatment and casting during two plant trials: Low Al steel (LAI) and High Al steel (HAI). After electrolytic extraction of the steel samples, characteristics of inclusions and clusters (such as morphology, composition, size and number) were investigated in three dimensions (3D) by SEM in combination with EDS. Moreover, the composition of typical inclusions and clusters was analyzed on a polished cross section of steel samples. Spherical (SP), irregular and regular (IR) inclusions and clusters (CL) were observed in the samples from both heats. It was found that the morphology and composition of inclusions and clusters in both heats were significantly changed during the ladle treatment and casting. Most of inclusions (44-98%) in a Low Al steel are MgO-CaO-SiO2-Al2O3 spherical inclusions. The compositions of IR inclusions and clusters in steel samples of a High Al steel were mostly MgO center dot Al2O3 spinet, but also the complex SP inclusions containing Al2O3-MgO-CaO-SiO2. In addition, phase stability diagram based on Darken's quadratic formalism and Redlich-Kister type polynomial was estimated for both heats at a non-infinite solution.
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| 6. |
- Bi, Yanyan, et al.
(författare)
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Investigations of inclusions in ferrochromium alloys
- 2014
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 41:10, s. 756-762
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Tidskriftsartikel (refereegranskat)abstract
- Ferrochromium alloys are commonly added during different stages of steelmaking processes according to the specific steel grade being produced. Depending upon the ferrochromium quality, the addition can also lead to a supply of deleterious inclusions to the liquid steel. Therefore, the number, size, morphology and composition of inclusions in LCFeCr and HCFeCr alloys were investigated. The alloy samples were first treated with electrolytic extraction, followed by filtration to gather the inclusions on a film filter. Thereafter, the characteristics of the inclusions and clusters were investigated in three dimensions by SEM in combination with energy dispersive spectroscopy. The results show that the main inclusion types found in LCFeCr alloys are different to those found in HCFeCr alloys. More specifically, the inclusions in LCFeCr alloys were found to consist of Si-Cr-O and Cr-O oxides as well as intermetallic Cr-Fe inclusions. Moreover, the inclusions in HCFeCr alloys were found to consist of Cr-Mn-S, Cr-C-N, Si-Al-Ca-Mg-O and Ca-O-P inclusions. Overall, the inclusions can be divided into two categories depending on the melting point. Furthermore, the possible transformation of different inclusions after their addition to the liquid steel is discussed.
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| 7. |
- Bi, Yanyan
(författare)
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Three Dimensional Determinations of Inclusions in Ferroalloys and Steel Samples
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As the requirements on material properties increase, there has been a demand on an additional knowledge on the effect of impurities in the ferroalloyson the steel cleanness. Thus, the number, morphology, size and composition of inclusions in sixdifferent ferroalloys (FeTi, FeNb, FeSi,SiMn, LC and HC FeCr) were investigatedin this study. This was done in three dimensions (3D) by using a SEM in combination with EDS after electrolytic extraction of the ferroalloy samples. Theresults show that thenon-metallic and metallic inclusions can besuccessfully analyzed on the surface of a film filterafter a separation of the inclusions from the matrix. Overall, the inclusions canbe divided into two categories depending on the melting point. Furthermore, the possible transformation of different kinds of inclusions after their addition to the liquid steel canalso be determined.The inclusions and clusters in steel samples of two similar steel grades of high-silicon non-calcium treated (HSiNC) stainless steels were also investigated and compared during ladle treatment and continuous casting. Samples of liquid steel and slag were taken at different stages of the ladle treatment and casting during two plant trials: a low Al steel (LAl) and a high Al steel (HAl). Spherical (SP), irregular and regular (IR) inclusions and clusters (CL) were observed in the samples from both heats. It wasfound that the morphology and composition of inclusions and clusters in both heats were significantly changed during the ladle treatment and casting. Most of inclusions (44-98%) in a low Al steel are MgO-CaO-SiO2-Al2O3spherical inclusions. The compositions of irregular and regularinclusions and clusters in steel samples of a high Al steel were mostly MgO·Al2O3spinel, but also complex sphericalinclusions containing Al2O3-MgO-CaO-SiO2. In addition, the phase stabilitydiagram based on Darken’s quadratic formalism and Redlich-Kister type polynomial was estimated for both heats at a non-infinite solution.It is known that clusters in liquid steel have a harmful effect on the casting process and the quality of the final steel product. Therefore, clusters of rare earth metals (REM) were investigated in steel samples of a S30185 stainless steel grade from a pilot trial (PT, 250 kg) and from an industrial heat (IH, 100 t). Samples were taken from the liquid steel at differentholding times after the addition of a mischmetal. The morphology, composition, number and size of clusters in PT and IH steel samples were analyzed and compared as a function of the holding time. It was found that typical clusters with regular and irregular inclusions were the main type of clusters (69%-98%) in all PT and IH steel samples. The composition of inclusions in clusters corresponded mostly to REM-oxides. The size of clusters that were observed in different samples varied mainly from 2 to 23 μm. In addition, the size and number of most clusters in PT are larger than those in IH samples.Largesize inclusions are recognized to be crucially harmful for the mechanical properties of steel products. Therefore, predictionsof the maximum size of Al2O3-CaO spherical inclusions in an Fe-10 mass% Ni alloy have been examined based on two dimensional (2D) and three dimensional (3D) investigations. The effects of the number of measurements and unit volume on the estimated 3D results were also investigated.
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| 8. |
- Bi, Yanyan, et al.
(författare)
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Three-dimensional determinations of the non-metallic inclusions in different ferroalloys
- 2014
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Konferensbidrag (refereegranskat)abstract
- Ferroalloys are commonly used in the steel industry to alloy or deoxidize the steel during the secondary steelmaking process before casting. Depending upon the ferroalloy quality, the addition can also lead to a supply of deleterious inclusions to the liquid steel. Thus, the number, morphology, size and composition of inclusions in six different ferroalloys (FeTi, FeNb, FeSi, SiMn LCFeCr and HCFeCr) were investigated. This was done in three dimensions (3D) by using SEM in combination with EDS after electrolytic extraction of the ferroalloy samples. Moreover, statistics of extreme values (SEV) were used to determine the largest size of inclusions.
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| 9. |
- Bi, Yanyan, et al.
(författare)
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Three Dimensional Evaluations of REM Clusters in Stainless Steel
- 2014
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 54:6, s. 1266-1273
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Tidskriftsartikel (refereegranskat)abstract
- It is known that clusters in liquid steel have a harmful effect on the casting process and the quality of the final steel product. In this study, clusters. of rare earth metals (REM) were investigated in steel samples of a S30185 stainless steel grade from a pilot trial (PT, 250 kg) and from an industrial heat (IH, 100 t). Samples were taken from the liquid steel at different holding times after the addition of mischmetal. Thereafter, REM clusters collected on film filters after electrolytic extraction and filtration were investigated in three dimensions (3D) by SEM in combination with EDS. The morphology, composition, number and size of clusters in PT and IH steel samples were analyzed and compared as a function of holding time. It was found that typical clusters with regular and irregular inclusions were the main type of clusters (69%-98%) in all PT and IH steel samples. The composition of inclusions in clusters corresponded mostly to REM-oxides. The size of clusters that were observed in different samples varied mainly from 2 to 23 mu m. In addition, the size and number of most clusters in PT are larger than those in IH samples. Furthermore, the formation mechanisms and evolution of different type of REM clusters were discussed in both PT and IH heats.
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| 10. |
- Bi, Yanyan, et al.
(författare)
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Three-dimensional investigations of inclusions in ferroalloys
- 2014
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 85:4, s. 659-669
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Tidskriftsartikel (refereegranskat)abstract
- As the requirements on material properties increase, there has been a demand on an additional knowledge on the effect of impurities in the ferroalloys on the properties. Thus, the number, morphology, size, and composition of inclusions in four different ferroalloys (FeTi, FeNb, FeSi, and SiMn) were investigated. This was done in three dimensions (3D) by using scanning electron microscopy in combination with energy dispersive spectroscopy after electrolytic extraction of the ferroalloy samples. The non-metallic and metallic inclusions were successfully analyzed on the surface of film filter. Thereafter, the particle size distribution was plotted for most of the non-metallic inclusions. The non-metallic inclusions were found to be REM oxides in FeTi, FeSi, and SiMn, Al2O3, Ti-Nb-S-O oxides in FeNb and silicon oxides in SiMn. Moreover, the intermetallic inclusions were found to be a Ti-Fe phase in FeTi, Ca-Si, and Fe-Si-Ti phases in FeSi and a Mn-Si phase in SiMn. In addition, the almost pure single metallic phases were found to be Ti in FeTi, Nb in FeNb, and Si in FeSi. As the requirements on material properties increase, the effect of impurities in ferroalloys on the steelmaking process is increasingly becoming more important. The characteristic of inclusions (morphology, number, size, and composition) in ferroalloys investigated in three-dimensional after electrolytic extraction is a good method for studying the evolution of inclusions during steelmaking.
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| 11. |
- Choi, Nuri, et al.
(författare)
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Influence of Manufacturing Conditions on Inclusion Characteristics and Mechanical Properties of FeCrNiMnCo Alloy
- 2020
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Three CoCrFeMnNi high-entropy alloys (HEAs) were produced by vacuum induction melting, induction melting under inert gas atmosphere, and melting under inert gas atmosphere followed by air exposure, respectively. The different manufacturing conditions for the three investigated alloys resulted in different levels and types of inclusions. The alloys melted under vacuum or inert gas contained Al2O3 inclusions formed by impurity Al, due to its high oxidation tendency. The molten alloy exposed in air showed an excessive oxidation. During oxidation of the molten alloy in air, impurity Al was initially oxidized, and fine MnCr2O4 inclusions were formed rather than pure Al2O3 inclusions. This difference was analyzed based on thermodynamic calculations. Specifically, the influence of impurity content on the inclusion characteristics was investigated for the three HEAs. Moreover, the inclusion characteristics were found to have an influence on mechanical properties of the alloys also. In air-exposed HEA, smaller inclusions were formed, resulting in a higher dislocation density at the matrix/inclusion interface and thus strengthening of the HEA. Thus, it is proposed that atmospheric conditions could be an important factor to control the inclusion characteristics and to form fine inclusion particles, which could improve the mechanical properties of HEAs.
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| 12. |
- Davydenko, Arkadiy, et al.
(författare)
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Characterization of Briquettes Used for Slag Foaming in the EAF during Stainless Steel Production
- 2014
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 86:2, s. 137-145
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Tidskriftsartikel (refereegranskat)abstract
- The modern sustainable stainless steel making industry is characterized by different factors such as an efficient utilization of energy in the Electric Arc Furnace (EAF) by a slag foaming practice and an utilization of waste products from its own production facilities. In this study, the foaming briquettes applied for a combined slag foaming and waste product reduction in the EAF are characterized. The recipes of the briquettes were made based on a literature review and previous experience. Afterwards, the composition and density of briquettes were estimated and compared to calculated data. Moreover, weight reduction experiments were made on a laboratory scale at temperatures up to 1500-°C in an argon atmosphere in order to characterize the products (metal, slag, and gas). Based on these results, the calculations were compared with experimental data. The following main results were found: (i) the density of briquettes can be successfully verified, (ii) briquettes have different mechanical properties depending on the materials used for production of briquettes, and (iii) the briquettes yield in different amounts of metal and gas. Moreover, it was found that light briquettes (without FeCr) produced almost double the amount of gas in comparison with heavy briquettes (containing FeCr); valuable metals can be recovered from briquettes, and recipes of briquettes can be optimized based on the amount of metal droplets in briquettes and the total utilization of carbon. This study is focused on a characterization of briquettes, which are used for slag foaming and waste product reduction in the Electric Arc Furnace (EAF) during the stainless steel production. The experimental data is compared with calculations according to the obtained results.
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| 13. |
- Davydenko, Arkadiy, et al.
(författare)
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Direct Reduction of Fe, Ni and Cr from Oxides of Waste Products Used in Briquettes for Slag Foaming in EAF
- 2019
-
Ingår i: Materials. - : MDPI. - 1996-1944. ; 12:20
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Tidskriftsartikel (refereegranskat)abstract
- Environmental aspects and the sustainable manufacturing of steels require producers to pay more and more attention to the efficient utilization of materials and waste products during steelmaking. This study is focused on the evaluation of possibilities for the recovery of metals (such as Fe, Ni and Cr) from waste products used for slag foaming in the Electric Arc Furnace (EAF) process. Two types of industrial briquettes were produced by mixing mill-scale from the hot rolling of stainless steels with anthracite and pet-coke, respectively. Thereafter, an assessment of the metal reduction processes in briquettes at high temperatures (1500 degrees C) was made by using laboratory thermo-gravimetric reduction experiments in an argon atmosphere. The amounts of metal, slag and gas obtained from the briquettes were estimated. In addition, the velocity and time for the removal of metal droplets from the liquid slag depending on the size of the metal droplets was estimated. It was found that up to 97% of metal droplets can be removed from the slag during the first 30 min. Moreover, results showed that most of the Cr, Ni and Fe (up to 93-100%) can be reduced from oxides of these metals in briquettes at 1500 degrees C. Moreover, the anthracite and pet-coke in the investigated briquettes have similar reduction capabilities. It was found that up to 330 kg of Fe, 28 kg of Ni and 66 kg of Cr per ton of added briquettes can be recovered from waste products by the industrial application of those briquettes for slag foaming in EAF.
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| 14. |
- Davydenko, Arkadiy, et al.
(författare)
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Investigation of Slag Foaming by Additions of Briquettes in the EAF during Stainless Steel Production
- 2015
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 86:2, s. 146-153
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Tidskriftsartikel (refereegranskat)abstract
- Nowadays, an effective application of energy required for stainless steel production in the electric arc furnace (EAF) by a slag foaming practice and recycling of waste products play two of the most significant roles for a sustainable steel production. In this study, briquettes were used to obtain a combined slag foaming and waste product reduction in the EAF process. Briquettes with different densities produced partly from waste products were tested in an industrial scale to study slag foaming in the EAF process during stainless steel production. The slag foaming tendency was determined based on visual estimations of slag foaming, evaluations of the slag density before and after addition of different briquettes, and by calculating a foaming index. The influence of the main parameters of briquettes (composition, density) and the furnace slag (composition, basicity, and, etc.) on slag foaming was studied. It was found that both heavy and light briquettes can be used for slag foaming. The heavy briquettes, with FeCr, produce about half the amount of gas compared to the light briquettes, without FeCr. The main part of the gas, >80%, was generated during the first 2-3min, Moreover, the highest slag foaming rate was obtained for slags with a basicity in the range of 1.31-1.49.
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| 15. |
- Davydenko, Arkadiy
(författare)
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Some aspects of recycling of rest products and slag foaming in the EAF during stainless steel production
- 2014
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An efficient stainless steel making industry is defined by different factors such as an efficient utilisation of energy in the Electric Arc Furnace (EAF). This requires a good by slag foaming practice and an utilisation of waste products from own production facilities. In the following study, briquettes applied for a combined slag foaming and waste product recycling in the EAF were investigated in both laboratory and industrial scales. More specifically, briquettes were characterised and used for slag foaming in the EAF. The recipes of the briquettes were made based on a literature review and previous experience. Afterwards, the composition and density of briquettes were defined and compared to calculated data. Moreover, weight reduction experiments were made on a laboratory scale at temperatures up to 1500°C in an argon atmosphere in order to characterise the products (metal, slag and gas) produced by briquettes. The calculations were also compared to experimental data. Thereafter, briquettes with different densities and pet-coke addition were tested on an industrial scale to study slag foaming in the EAF process during a stainless steel production. The slag foaming tendencies were determined based on visual estimations of slag foaming, determinations of the slag density before and after additions of different briquettes, and by calculating a foaming index. Moreover, the influence of the main parameters of the briquettes (composition, density) and the furnace slag (composition, basicity and etc.) on slag foaming was studied. Investigation of briquettes made on laboratory and industrial scales provided the following main results: the density of briquettes can successfully be verified, briquettes have different mechanical properties depending on the materials used for production of briquettes, briquettes yield different amounts of metal and gas. Moreover, it was found that the heavy briquettes (containing FeCr) produce about half the amount of gas compared to the light briquettes (without FeCr). The main part of the gas was generated during the first 2-3 min. Also, the valuable metals can be recovered from briquettes; recipes of briquettes can be optimized based on the amount of metal droplets in briquettes and the total utilisation of carbon. In addition, it was found that both heavy and light briquettes can be used for slag foaming. The highest slag foaming rate was obtained for slags with a basicity in the range of 1.31-1.49.
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| 16. |
- De Colle, Mattia, et al.
(författare)
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A Study of Treatment of Industrial Acidic Wastewaters with Stainless Steel Slags Using Pilot Trials
- 2021
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 14:17, s. 4806-
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Tidskriftsartikel (refereegranskat)abstract
- Different stainless steel slags have been successfully employed in previous experiments, for the treatment of industrial acidic wastewaters. Although, before this technology can be implemented on an industrial scale, upscaled pilot experiments need to be performed. In this study, the parameters of the upscale trials, such as the volume and mixing speeds, are firstly tested by dispersing a NaCl tracer in a water bath. Mixing time trials are used to maintain constant mixing conditions when the volumes are increased to 70, 80 and 90 L, compared to the 1 L laboratory trials. Subsequently, the parameters obtained are used in pH buffering trials, where stainless steel slags are used as reactants, replicating the methodology of previous studies. Compared to laboratory trials, the study found only a minor loss of efficiency. Specifically, in previous studies, 39 g/L of slag was needed to buffer the pH of the acidic wastewaters. To reach similar pH values within the same time span, upscaled trials found a ratio of 43 g/L and 44 g/L when 70 and 90 L are used, respectively. Therefore, when the kinetic conditions are controlled, the technology appears to be scalable to higher volumes. This is an important finding that hopefully promotes further investments in this technology.
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| 17. |
- De Colle, Mattia
(författare)
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Experimental studies to overcome the recycling barriers of stainless-steel and BOF slags
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents several studies aimed at improving the recycling of steel slag. The studies are based on a first evaluation of the state-of-the-artof the recycling applications both with respect to their possibilities and limitations. In addition, an analysis that highlights several properties of allkinds of ferrous slags, such as bulk chemical composition and common mineral phases, is presented to aid the discussion. Specifically, the studiespresented in this thesis cover two main topics: a new recycling application for stainless-steel slags and a theoretical study on the hydration offerropericlase, which is a mineral often present in basic oxygen furnace slags. Most of the studies presented in this thesis focus on the exploration of anew use of stainless-steel slags, aimed at increasing their recycling rate. In fact, this kind of materials are the most problematic slags to recycle, asmost are not viable for most of the state-of-the-art applications. Therefore, the potential to use them as a substitute for lime in the neutralization ofacidic waste waters is investigated. The studies cover a wide range of trials, from test performed at both laboratory and industrial scale with acidicwaste waters collected from stainless-steel plants, to more fundamental studies on the dissolution of slag minerals in acid environment. Overall,the substitution of lime with stainless-steel slags is proved to be successful both in terms of the obtained final pH values as well as in terms ofobtaining an efficient removal of metal ions dissolved in waters. In the last part of the thesis, a theoretical study on the hydration offerropericlase is conducted. This study proposes a possible technical solution to reduce the volumetric expansion of steel slags, which containhigh percentages of periclase. Specifically, it is seen that ferropericlase with high percentages of FeO adsorbs less water. Thus, they expand lesscompared to regular periclase. Therefore, the formation of such a phase during the solidification of slag can provide a higher volumetric stability,which is highly beneficial when the material later is employed in outdoors applications
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| 18. |
- De Colle, Mattia, et al.
(författare)
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Study of the Dissolution of Stainless-Steel Slag Minerals in Different Acid Environments to Promote Their Use for the Treatment of Acidic Wastewaters
- 2021
-
Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 11:24
-
Tidskriftsartikel (refereegranskat)abstract
- Several stainless-steel slags have been successfully employed in previous studies as substitutes for lime in the treatment of industrial acidic wastewaters. This study deepens the knowledge of such application, by analyzing the neutralizing capacity of different slags related to their mineral compositions. To do so, firstly the chemical and mineral compositions of all the slag samples are assessed. Then, 0.5 g, 1 g, 2 g of each slag and 0.25 g and 0.5 g of lime are used to neutralize 100 g of 0.1 M HCl or HNO3 solutions. After the has neutralization occurred, the solid residues are extracted and analyzed using XRD spectroscopy. Then, the solubility of the minerals is assessed and ranked, by comparing the XRD spectra of the residues with the obtained pH values. The results show that minerals such as dicalcium silicate and bredigite are highly soluble in the selected experimental conditions, while minerals such as merwinite and akermanite, only partially. Moreover, Al-rich slags seem to perform poorly due to the formation of hydroxides, which generate extra protons. However, when the weight of slag is adequately adjusted, Al-rich slags can increase the pH values to higher levels compared to the other studied slags.
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| 19. |
- De Colle, Mattia, et al.
(författare)
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Study of the Hydration Behavior of Synthetic Ferropericlase with LowIron Oxide Concentrations to Prevent Swelling in Steel Slags
- 2021
-
Ingår i: Journal of Sustainable Metallurgy. - : Springer Nature. - 2199-3831 .- 2199-3823.
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Tidskriftsartikel (refereegranskat)abstract
- Steel slags generally swell when subjected to water or humidity, which prevents proper recycling in the cement or asphaltindustries. The MgO and CaO phases in steel slags are responsible for this phenomenon, as both minerals easily absorb waterto form their respective hydroxides. MgO is often present in steel slags in a solid solution with several oxides, constitutingthe so-called RO phase. This study investigates the hydration rate of an RO phase consisting of FeO and MgO called ferropericlase.The material was synthesized in a laboratory furnace by sintering a FeO–MgO powder mixture with varying initialFeO contents (approximately 10, 15, and 20 wt%). Thereafter, electron probe micro-analyzer (EPMA) and X-ray diffraction(XRD) spectroscopies were used to characterize the structure of the samples, which were mainly composed of ferropericlaseand an exsolution of magnesioferrite. Also, Mössbauer spectra showed that the total ferrous iron proportion (Fe2+/ΣFe) ofthe sintered samples was in the range of 0.55–0.72. To measure the hydration behavior, the samples in powder form werecured in an autoclave at an H2Opartial pressure of 2 atm. Thereafter, thermal gravimetric analysis (TGA) was performed tomeasure the amount of water absorbed during the autoclave curing from the mass drop associated with the dehydration ofthe hydroxide. The study found a linear correlation between the initial FeO content and the weight loss after TGA, with areduction down to 6% in the sample with an initial FeO content of 20 wt% content compared to pure MgO.
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| 20. |
- De Colle, Mattia, 1989-, et al.
(författare)
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The Use of High-Alloyed EAF Slag for the Neutralization of On-Site Produced Acidic Wastewater: The First Step Towards a Zero-Waste Stainless-Steel Production Process
- 2019
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 9:19
-
Tidskriftsartikel (refereegranskat)abstract
- Recycling of steelmaking slags has well-established applications, such as their use in cement, asphalt, or fertilizer industries. Although in some cases, such as the electric arc furnace (EAF) high-alloyed stainless-steel production, the slag’s high metal content prevents its use in such applications. This forces companies to accumulate it as waste. Using concepts such dematerialization, waste management, industrial symbiosis, and circular economy, the article drafts a conceptual framework on the best route to solving the landfilling issue, aiming at a zero-waste process re-design. An experimental part follows, with an investigation of the use of landfill slag as a substitute of limestone for the neutralization of acidic wastewater, produced by the rinsing of steel after the pickling process. Neutralization of acidic wastewater with both lime and slag samples was performed with two different methods. Two out of four slag samples tested proved their possible use, reaching desired pH values compared to lime neutralizations. Moreover, the clean waters resulting from the neutralizations with the use of both lime and slag were tested. In terms of hazardous element concentrations, neutralization with slag yielded similar results to lime. The results of these trials show that slag is a potential substitute of lime for the neutralization of acidic wastewater.
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| 21. |
- Doostmohammadi, Hamid, et al.
(författare)
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A Comparison of a Two-Dimensional and a Three-Dimensional Method for Inclusion Determinations in Tool Steel
- 2010
-
Ingår i: STEEL RES INT. - : Wiley. - 1611-3683. ; 81:5, s. 398-406
-
Tidskriftsartikel (refereegranskat)abstract
- To produce clean commercial tool steel the non-metallic inclusions characteristics have to be known, since they influence the mechanical properties of steel. In this work, inclusion characteristics in steel samples from plant trials were studied. The samples were collected in the steel plant according the two following methods: (a) 2D investigations of inclusions by a cross sectional method and (b) 3D investigations of inclusions collected on a film filter after electrolytic extraction. More specifically, the chemical composition, morphology, number and size distribution of inclusions in tool steel samples taken from ladle during melt treatment were determined by both methods. In both methods SEM equipped with EDS was used for compositional analysis of inclusions. In addition, in the cross sectional method an automated detection program called 'INCAFeature' was used to collect more statistics of non-metallic inclusions. The composition of inclusions larger than 5 mu m was found to contain 49% CaO based on the results from both methods. However, for smaller inclusions it was found that the accuracy of the 2D method was less than that of the 3D method due to the influence of the metal matrix on the results. In addition, it was found that a critical inclusion size of 4 mu m could be defined for the 3D method, above which the standard deviation in composition determination was very low.
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| 22. |
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| 23. |
- Doostmohammadi, Hamid, et al.
(författare)
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Use of Computational Thermodynamic Calculations in Studying the Slag/Steel Equilibrium during Vacuum Degassing
- 2010
-
Ingår i: STEEL RES INT. - : Wiley. - 1611-3683. ; 81:1, s. 31-39
-
Tidskriftsartikel (refereegranskat)abstract
- The effectiveness of a ladle refining process for production of tool steel with focus on the top slag is studied using computational thermodynamic calculations. The theoretical assessment was based on compositional data of steel and slag samples collected during trials in a plant equipped with a 65-t EAF, a ladle furnace and a vacuum degasser The calculation of slag-metal equilibrium during ladle treatment was performed for top slag excluding (Case A) and including (Case B) slag carryover and deoxidation products. The predictions showed that slag carryover and deoxidation products in the ladle significantly affect the composition of the top slag. Thus, these conditions must be taken into consideration when predicting the actual top slag composition. It was also found that it is possible to predict the final aluminium and sulphur content in steel based on the same calculation approach.
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| 24. |
- Du, Hongying, et al.
(författare)
-
Assessment of Chip Breakability during Turning of Stainless Steels Based on Weight Distributions of Chips
- 2020
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 10:5
-
Tidskriftsartikel (refereegranskat)abstract
- Currently, the available evaluation methods for determining the chip breakability in the industry are mainly based on subjective visual assessment of the chip formation by an operator during machining or on chips that were collected after the tests. However, in many cases, these methods cannot give us accurate quantitative differences for evaluation of the chip breakability of similar steel grades and similar sets of machining parameters. Thus, more sensitive methods are required to obtain more detailed information. In this study, a new method for the objective assessment of chip breakability based on quantitative determination of the weight distribution of chips (WDC) was tested and applied during machining of stainless steels without Ca treatment (316L) and with Ca treatment (316L + Ca). The obtained results show great consistencies and the reliability of this method. By using the WDC method, significant quantitative differences were obtained by the evaluation of chips, which were collected during the machining process of these two similar grades of steel at various cutting parameters, while, visually, these chips look very similar. More specifically, it was found that the Ca treatment of steel can improve the chip breakability of 316L + Ca steel in 80% of cutting trials, since a fraction of small light chips (Type I) from this steel increased and a fraction of large heavy chips (Type III) decreased accordingly. Moreover, the WDCs that were obtained at different cutting parameters were determined and compared in this study. The obtained results can be used for the optimization of chip breakability of each steel at different cutting parameters. The positive effect of Ca treatment of stainless steel was discussed in this study based on consideration of the modification of different non-metallic inclusions and their effect on the chip breakability during machining.
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| 25. |
- Du, Hongying, et al.
(författare)
-
Characterization of non-metallic inclusions in low-alloyed steels by using PDA/OES and off-line investigation methods
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The characteristics of non-metallic inclusions(NMIs)in low-alloyed steel samples taken during ladle treatment beforeand after Ca-treatment were evaluated by using the Pulse Distribution AnalysisOptical Emission Spectroscopy (PDA/OES)method,INCA-Feature investigationsof inclusions on polished surfacesof steel samples, and three-dimensional investigations of NMIs after electrolytic extraction (EE) ofsteel samples. The investigation results of NMIs by using different methodswere compared.The PDA/OES resultsshow a clear tendency of achange in the average composition and quantity of NMIs during the ladle treatment, whichcorrelated well with the resultsobtainedfrom the other two methods. Overall, it was found that theapplication of the PDA/OES method is appropriate to enablea fast on-lineevaluation of inclusioncompositionsand their behaviors during steelmaking. This, in turn,provides the means for establishing an on-linecontrol and correction of technological operations of the ladle treatment to implement necessary modification of NMIsin order to improve the cleanliness of steelsand to avoid clogging problemsduring casting.
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| 26. |
- Du, Hongying, et al.
(författare)
-
Characterization of Nonmetallic Inclusions in Low-Alloyed Steels Using Pulse Distribution Analysis Optical Emission Spectroscopy and Offline Investigation Methods
- 2021
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 92:11, s. 2100223-
-
Tidskriftsartikel (refereegranskat)abstract
- The characteristics of nonmetallic inclusions (NMIs) in low-alloyed steel samples taken during ladle treatment before and after Ca treatment are evaluated using the pulse distribution analysis optical emission spectroscopy (PDA/OES) method, INCA-Feature investigations of inclusions on a polished surface of steel samples, and 3D investigations of NMIs after electrolytic extraction (EE) of steel samples. The investigation results of NMIs using the different methods were compared. The PDA/OES results show a clear tendency of a change in the average composition and quantity of NMIs during ladle treatment, which correlates well with the results obtained from the other two methods. Overall, it is found that the application of the PDA/OES method is appropriate to enable a fast online evaluation of inclusion compositions and their behaviors during steelmaking. This, in turn, provides the means for establishing an online control and correction of technological operations of the ladle treatment to implement necessary modification of NMIs to improve the cleanliness of steels and avoid clogging problems during casting.
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| 27. |
- Du, Hongying, 1991-
(författare)
-
Evaluations of Non-metallic Inclusionsin Ca-treated Steels and Their Effect on the Machinability
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent decades, a considerable development of steel with respect to the performance of steel has taken place, which also has resulted in large challenges to process these steel grades. Therefore, it is essential to make suitable modifications of non-metallic inclusions (NMI) in the steelmaking process and to have a good control of its characteristics to meet the target mechanical properties and to obtain a good machinability. Based on a case of 316L stainless steel trials with a calcium modification to improve the machinability of steel, the influence and contribution of different NMIs on the machinability were discussed. First, based on the Thermo-Calc calculation results with respect to the appropriate range of Ca additions, steel is produced by an additional Ca treatment at the end of the ladle treatment. In order to evaluate non-metallic inclusions and their influence on machinability tests, steel samples were collected from rolled bars produced by the conventional production route (316R) and an experimental trial with Ca treatment (316Ca). The metal chips generated during the machining test were also collected for the evaluation of chip breakability and NMIs characteristics after machining. In addition, the Electrolytic extraction (EE) technology is used to extract NMIs from steel and chip samples. Then, a three-dimensional (3-D) study is performed on the inclusions collected on a membrane filter using a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The morphology, size, number, frequency, and composition of non-metallic inclusions are studied. Four main types of inclusions were found in the 316Ca steel: Type I (elongated MnS), Type II (oxy-sulfides with hard oxide cores), Type III (soft elongated oxides), and Type IV (hard undeformed oxides).The results show that the morphologies of NMIs in stainless steel chips were significantly changed after cutting. Overall, three different main shapes of NMIs were found: i) Group I having similar shapes, ii) Group II stretched inclusions having very thin film-like (Group II-a) and fractured stretched morphologies (Group II-b), and iii) Group III brittlely fractured inclusions. The total areas of MnS and SO inclusions in the secondary deformation zone of the chips were significantly increased (by up to 2-3 times) compared to that of the reference steel sample before the cutting test. It was found that the morphologies of NMIs during machining depend on the location in chips, the workpiece material, as well as the applied cutting speed. This results in different temperatures and metal matrix deformation degrees during machining. In addition, the chip breakability and chip tool contact length of the reference steel and the experimental steel were evaluated and compared with the characteristics of NMIs in the two steels. A new weight-measurement-based method was developed. The results show that the 316Ca steel generally has a better machinability compared to the reference 316R steel. However, the chip-tool contact length results show that the modification of NMIs for machinability improvements is only beneficial in some machining processes. The 316R steel was preferred at low cutting speeds, whereas the 316Ca steel was preferred at high cutting speeds. The different characteristics of NMI in the various cutting conditions and materials lead to different behaviors and functions of NMI during processing. Finally, the possible application of PDA/OES in the steelmaking process was also evaluated. This online survey method developed in the industry during recent years provides a high possibility for implementing a rapid screening of the NMI content and shows the potential of establishing an online control of NMI during the processing of steel.
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| 28. |
- Du, Hongying, et al.
(författare)
-
Influence of non-metallic inclusions in 316L stainless steels on machining using different cutting speeds
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This research focuses on providing a detailed characteristic of non-metallic inclusions (NMIs) in 316L stainless steels with and without Ca treatment after machining using different cutting speeds. The electrolytic extraction (EE) technique was used for three-dimensional determinations of the inclusion characteristics. Quantitative data from the fragile non-metallic inclusions (such as size, surface area, number) in chips obtained from different cutting speeds and materials were determined. The morphologies of NMIs in the chip samples were quite different compared to the original inclusions in the stainless steel samples before machining. It was proved that the deformation degree of soft inclusions such as MnS and CaO-SiO2-Al2O3-MgO-TiOx is dependent on the cutting speed as well as the temperatures and deformation degrees of the metal matrix during machining. The total surface areas of MnS inclusions increase from 2.8 to 3.8 times compared to the original total areas with an increased cutting speed. The total surface areas of soft oxide inclusions also increase from 1.1 to 3.5 times compared to the original total areas. In addition, the tool-chip contact lengths were also measured on the rake face of the tool, and the results were compared to the determined characteristics of the observed inclusions. It was found2that the modification of NMIs by Ca treatment in 316L stainless steels is preferred for high cutting speeds.
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| 29. |
- Du, Hongying, et al.
(författare)
-
Influence of Non-metallic Inclusions in 316L Stainless Steels on Machining Using Different Cutting Speeds
- 2021
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 61:9, s. 2426-2434
-
Tidskriftsartikel (refereegranskat)abstract
- This research focuses on providing a detailed characteristic of non-metallic inclusions (NM's) in 316L stainless steels with and without Ca treatment after machining using different cutting speeds. The electrolytic extraction (EE) technique was used for three-dimensional determinations of the inclusion characteristics. Quantitative data from the fragile non-metallic inclusions (such as size, surface area, number) in chips obtained from different cutting speeds and materials were determined. The morphologies of NMIs in the chip samples were quite different compared to the original inclusions in the stainless steel samples before machining. It was proved that the deformation degree of soft inclusions such as MnS and CaO-SiO2-Al2O3-MgO-TiOx is dependent on the cutting speed as well as the temperatures and deformation degrees of the metal matrix during machining. The total surface areas of MnS inclusions increase from 2.8 to 3.8 times compared to the original total areas with an increased cutting speed. The total surface areas of soft oxide inclusions also increase from 1.1 to 3.5 times compared to the original total areas. In addition, the tool-chip contact lengths were also measured on the rake face of the tool, and the results were compared to the determined characteristics of the observed inclusions. It was found that the modification of NMIs by Ca treatment in 316L stainless steels is preferred for high cutting speeds.
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| 30. |
- Du, Hongying, et al.
(författare)
-
Modification of Non-Metallic Inclusions in Stainless Steel by Addition of CaSi
- 2019
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- The focus of this study involved comparative investigations of non-metallic inclusions in 316L stainless steel bars without and with Ca treatments. The inclusions were extracted by using electrolytic extraction (EE). After that, the characteristics of the inclusions, such as morphology, size, number, and composition, were investigated by using a scanning electron microscope (SEM) in combination with an energy dispersive X-ray spectroscopy (EDS). The following four types of inclusions were observed in 316L steels: (1) Elongated MnS (Type I), (2) MnS with hard oxide cores (Type II), (3) Undeformed irregular oxides (Type III), and (4) Elongated oxides with a hard oxide core (Type IV). In the reference sample, only a small amount of the Type III oxides (Al2O3-MgO-MnO-TiOx) existed. However, in Ca-treated 316L steel, about 46% of the observed inclusions were oxide inclusions (Types III and IV) correlated to gehlenite and to a mixture of gehlenite and anorthite, which are favorable for the machinability of steel. Furthermore, untransformed oxide cores (Al2O3-MgO-MnO) were also found in the inclusions of Type IV. The mechanism leading to different morphologies of oxide inclusions is also discussed.
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| 31. |
- Du, Hongying, 1991-, et al.
(författare)
-
Three-Dimensional Investigations of Non-Metallic Inclusions in Stainless Steels Before and After Machining
-
Ingår i: ISIJ International. - 0915-1559 .- 1347-5460.
-
Tidskriftsartikel (refereegranskat)abstract
- The focus of this study is to investigate non-metallic inclusions (NMIs) in stainless steels before (in steel samples) and after machining (in steel chips). In this study, the electrolytic extraction (EE) technique was used to extract non-metallic inclusions from steel samples. This makes it possible to investigate NMIs on film filters as three-dimensional objects by using SEM. The characteristics of NMIs in steel and chips have been systematically investigated and compared. Based on the results, it was found that the morphology of NMIs was significantly changed after machining. Overall, three different main shapes of NMIs were found: 1) a similar shape, 2) a stretched shape, and 3) a brittlely fractured shape. Furthermore, the degree of deformation of MnS and soft oxide NMIs in different zones of the chips depends on the distances from the contact zone of the tool and the chip. The total areas of MnS and soft oxides in the secondary deformation zone were increased by up to 2-3 times compared to that of the reference steel sample. This study also shows the advantages of the EE method in investigating NMIs in chips compared to using the conventional two-dimensional investigations of NMIs on the polished metal surface.
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| 32. |
- Du, Hongying, et al.
(författare)
-
Three-dimensional Investigations of Non-metallic Inclusions in Stainless Steels before and after Machining
- 2021
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 61:9, s. 2416-2425
-
Tidskriftsartikel (refereegranskat)abstract
- The focus of this study is to investigate non-metallic inclusions (NMIs) in stainless steels before (in steel samples) and after machining (in steel chips). In this study, the electrolytic extraction (EE) technique was used to extract non-metallic inclusions from steel samples. This makes it possible to investigate NMIs on film filters as three-dimensional objects by using SEM. The characteristics of NMIs in steel and chips have been systematically investigated and compared. Based on the results, it was found that the morphology of NMIs was significantly changed after machining. Overall, three different main shapes of NMIs were found: 1) a similar shape, 2) a stretched shape, and 3) a brittlely fractured shape. Furthermore, the degree of deformation of MnS and soft oxide NMIs in different zones of the chips depends on the distances from the contact zone of the tool and the chip. The total areas of MnS and soft oxides in the secondary deformation zone were increased by up to 2-3 times compared to that of the reference steel sample. This study also shows the advantages of the EE method in investigating NMIs in chips compared to using the conventional two-dimensional investigations of NMIs on the polished metal surface.
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| 33. |
- Du, Hongying, et al.
(författare)
-
Using chip weight distribution as a method to define chip breakability during machining
- 2018
-
Ingår i: Proceedings 8th Swedish Production Symposium (SPS). - : Elsevier BV. ; 25, s. 309-315
-
Konferensbidrag (refereegranskat)abstract
- Nowadays, the existing evaluation methods of chip breakability in industry are based on subjective visual evaluations of the chip formation during cutting or on a chip chart made after the tests. However, more sensitive methods are needed to provide more in-depth information. Thus, this study proposes a method to better evaluate the chip breakability. Based on a systematically study using the weight distribution measurement method, the results show that a great consistency and reliability to evaluate the chip breakability can be obtained. Overall, it is an objective, available and precise method to be applied in the academic and industrial research. (C) 2018 The Authors. Published by Elsevier B.V.
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| 34. |
- Ericsson, Ola
(författare)
-
An Experimental Study of a Liquid Steel Sampling Process
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the steelmaking process samples are taken from the liquid steel, mainly to assess the chemical composition of the steel. Recently, methods for rapid determination of inclusion characteristics (size and composition) have progressed to the level where they can be implemented in process control. Inclusions in steel can have either good or detrimental effects depending on their characteristics (size, number, composition and morphology). Thereby, by determination of the inclusion characteristics during the steelmaking process it is possible to steer the inclusion characteristics in order to increase the quality of the steel. However, in order to successfully implement these methods it is critical that the samples taken from the liquid steel represent the inclusion characteristics in the liquid steel at the sampling moment. The purpose of this study is to investigate the changes in inclusion characteristics during the liquid steel sampling process. Experimental studies were carried out at steel plants to measure filling velocity and solidification rate in real industrial samples. The sampling conditions for three sample geometries and two slag protection types were determined. Furthermore, the dispersion of the total oxygen content in the samples was evaluated as a function of sample geometry and type of slag protection. In addition, the effects of cooling rate as well as oxygen and sulfur content on the inclusion characteristics were investigated in laboratory and industrial samples. Possibilities to separate primary (existing in the liquid steel at sampling moment) and secondary (formed during cooling and solidification) inclusions depending on size and composition were investigated. Finally, in order to evaluate the homogeneity and representative of the industrial samples the dispersion of inclusion characteristics in different zones and layers of the samples were investigated. It was concluded that the type of slag protection has a significant effect on the filling velocity and the sampling repeatability. Furthermore, that the thickness of the samples is the main controlling factor for the solidification rate. It was shown that top slag can contaminate the samples. Therefore, the choice of slag protection type is critical to obtain representative samples. It was shown that the cooling rate has a significant effect on the number of secondary precipitated inclusions. However, the number of primary inclusions was almost constant and independent on the cooling rate. In most cases it is possible to roughly separate the secondary and primary oxide inclusions based on the particle size distributions. However, in high-sulfur steels a significant amount of sulfides precipitate heterogeneously during cooling and solidification. This makes separation of secondary and primary inclusions very difficult. Moreover, the secondary sulfides which precipitate heterogeneously significantly change the characteristics (size, composition and morphology) of primary inclusions. The study revealed that both secondary and primary inclusions are heterogeneously dispersed in the industrial samples. In general, the middle zone of the surface layer is recommended for investigation of primary inclusions.
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| 35. |
- Ericsson, Ola, 1984-
(författare)
-
An Experimental Study of Liquid Steel Sampling
- 2009
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sampling of liquid steel to control the steel making process is very important in the steel industry. However, there are numerous types of disposable samplers and no united standard for sampling. The goal in this study is to investigate the effect of slag protection type and sample geometry on sampling parameters and sample homogeneity. Three sample geometries were selected: i) Björneborg ii) Lollipop with a 6 mm thickness and iii) Lollipop with a 12 mm thickness. These sample geometries have been tested with two types of slag protection: metal-cap-protection and argon-protection. The filling velocity and solidification rate of steel samples have been experimentally measured during plant trials. The sample homogeneity with respect to total oxygen content and inclusion size distribution has been determined in different parts of the samples. The study shows that argon-protected samplers have lower, more even, filling velocities (0.19±0.09 m/s) compared to metal-cap-protected samplers (1.28±2.23 m/s). The solidification rate measurements of the different samplers show that the 6 mm thick Lollipop has the highest solidification rate (99~105 °C/s). Measurements of total oxygen content in argon-protected samples showed little variation between different zones of the samples. However, metal-cap-protected samples contained much higher total oxygen contents. Light optical microscope studies showed that the increase in total oxygen content was probably caused by entrapment of top slag during sampling. Furthermore, it was found that the contamination of top slag in the metal samples increased with a decreased sample weight. Determination of inclusion size distribution in argon-protected Lollipop samples showed that a larger number of primary inclusions are found in the top part compared to the middle and the bottom part of the samples.
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| 36. |
|
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| 37. |
- Ericsson, Ola, et al.
(författare)
-
Changes in inclusion characteristics during sampling of liquid steel
- 2012
-
Ingår i: Ironmaking & Steelmaking. - 0301-9233. ; 39:1, s. 67-75
-
Tidskriftsartikel (refereegranskat)abstract
- In order to improve the process control during the steelmaking process, it is essential to obtain knowledge, as well as interpret information, on the characteristics of non-metallic inclusions in liquid steel samples. The purpose of the present study is to evaluate the effect of different sampling conditions on the inclusion characteristics. The changes in number, size and composition of primary inclusions due to the precipitation of secondary inclusions are studied. This is investigated in laboratory scale samples from an Fe-10 mass-%Ni alloy as well as industrial steel samples with varying contents of oxygen and sulphur. The results show that in most cases, the inclusion population can be separated, using a size condition, into primary (>= 0.6 mu m) and secondary (< 0.6 mu m) inclusions. Overall, the Lollipop sample with a 6 mm thickness can be recommended, because most of the secondary inclusions in low sulphur steels can be removed from the total particle size distribution. However, during sampling of liquid steel containing high levels of sulphur, a significant amount of sulphides precipitate heterogeneously onto primary inclusions, making it impossible to use size or morphology to separate the population. Finally, the numbers of secondary inclusions in the steel samples were found to increase significantly with an increased sample cooling rate. However, the number of primary inclusions was found to be almost constant and independent of the sample cooling rate.
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| 38. |
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| 39. |
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| 40. |
- Ericsson, Ola, et al.
(författare)
-
Effect of Slag Protection System and Sample Geometry on Homogeneity of Total Oxygen Content in Samples from Liquid Steel
- 2011
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 82:3, s. 222-229
-
Tidskriftsartikel (refereegranskat)abstract
- Many kinds of disposable samplers are available for sampling of liquid steel during steelmaking. Depending on slag protection, they can be divided into two main groups: metal-cap-protected and argon-protected samplers. For high quality steels, a correct determination of inclusion characteristics in metal samples is important for an improved process control. This paper seeks to investigate the effect of slag protection system, and sample geometry, on deviation and total content of oxygen within samples from the ladle treatment of liquid duplex stainless steel. The homogeneity with respect to total oxygen content was determined for different zones in the body, pin and inlet part of Bjorneborg and Lollipop (6 and 12mm thickness) samples. The results showed low, and stable, contents of oxygen in the argon-protected samples. However, the total oxygen content, and deviation of oxygen, in metal-cap-protected samples was much higher, especially in the body part of the samples. Finally, it was found that the oxygen content heterogeneity in the metal-cap-protected samples increased with a decreased sample weight. Based on the obtained results, the 6mm thick Lollipop sample with argon-protection is recommended for determination of total oxygen content and oxide inclusion characteristics.
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| 41. |
- Ericsson, Ola, et al.
(författare)
-
Experimental study of parameters for liquid steel sampling
- 2010
-
Ingår i: Steel Grips - Journal of Steel and Related Materials. - 1611-4442 .- 1866-8453. ; 8, s. 115-124
-
Tidskriftsartikel (refereegranskat)abstract
- Sampling of liquid steel to control the steel making process is very important in the steel industry. However, numerous types of disposable samplers are available and no united standard for sampling exists today. The goal in this study is to investigate the effect of slag protection type and sample geometry on sampling parameters such as filling velocity and solidification rate. Three sample geometries were selected: i) Björneborg, ii) 6 mm thick Lollipop, and iii)12 mm thick Lollipop. These have been tested with two types of slag protection: metal-cap protection and argon protection. The filling velocity and solidification rate of steel samples, which are very important for inclusion characteristics and sample quality, have been experimentally measured during plant trials. The study shows that argon protected samples have lower, more even, filling velocities (0.19 ± 0.09 m/s) compared to metal-cap protected samples (1.77 - 2.08 m/s). Solidification rate results for a 304L stainless steel show that the 6 mm thick Lollipop sample solidifies at a rate of about 100 °C/s while the Björneborg and the 12 mm thick Lollipop sample solidifies at a rate of about 20 °C/s.
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| 42. |
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| 43. |
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| 44. |
- Gorkusha, Dmitry, et al.
(författare)
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Characterization of Non-metallic Inclusions and Clusters during Production of Low-carbon IF Steel
- 2020
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 60:12, s. 2819-2828
-
Tidskriftsartikel (refereegranskat)abstract
- One of the quality criteria for Interstitial Fee (IF) steels is the metal purity with respect to non-metallic inclusions (NMI), which are harmful for the plastic properties of the material. Furthermore, they cause a formation of surface defects in flat rolled products and reduce the rate of steel casting due to nozzle clogging. This article presents the results of a study of the content, composition, size and morphology of non-metallic inclusions and clusters in steel samples taken during ladle treatment, casting as well as from slabs and steel sheets after rolling of IF steel. The characteristics of NMI and clusters were determined by using conventional two-dimensional quantitative metallographic investigations of polished sections of steel samples (2D method), electrolytic extraction (EE method) of samples followed by investigations of inclusions and clusters by using scanning electron microscopy and energy dispersive spectroscopy and fractional gas analysis (FGA method). By using EE method, different types of inclusions and clusters, their formation, growth and behavior during different stages of IF steel production were studied. The results obtained by the EE method agreed well with the results of the quantitative determination of oxide NMI by using the FGA method. The method of fractional gas analysis shows the dynamics of changes in the content of various types of oxide non-metallic inclusions during ladle treatment and casting of steel. The obtained results can be used to analyze the causes of the formation of harmful NMI in the metal and to optimize ladle treatment of IF steel grades.
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| 45. |
- Gorkusha, D. V., et al.
(författare)
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Content modification of different types of nonmetallic inclusions during low-carbon if steel ladle treatment
- 2019
-
Ingår i: Izvestiya Ferrous Metallurgy. - : National University of Science and Technology MISIS. - 0368-0797 .- 2410-2091. ; 62:5, s. 345-352
-
Tidskriftsartikel (refereegranskat)abstract
- Development of advanced materials for the automotive industry allows us to produce a lighter body without losing strength characteristics of the structure. It became possible by the creation and subsequent introduction into the production of such steel grades as IF (Interstitial Free)-steel with no interstitial solute atoms to strain the solid iron lattice and IF-BH (Bake Hardening)-steel with hardening during hot drying. The article provides a brief overview of the history of the emergence of IF steel and the current situation in the production of it in Russia. One of the quality criteria for steels of IF grades is purity of the metal by non-metallic inclusions (NMI), which negatively affect the plastic properties of the material, lead to the formation of surface defects of flat rolled products and reduce the manufacturability due to a decrease in the casting speed of steel, as they cause overgrowing of steel casting nozzles. The article presents investigation results of the content, composition, size and morphology of non-metallic inclusions (NMI) in the metal samples taken at all stages of ladle treatment and casting of IF steel grade production using quantitative metallographic analysis, electrochemical dissolution (ED) followed by X-ray microanalysis of isolated inclusions, Auger electron spectroscopy and fractional gas analysis (FGA). As a result of the analysis of inclusions in the studied samples using a scanning electron microscope, according to morphological features, five characteristic types of inclusions were identified, which reduce the performance properties and strength characteristics of the materials produced from them. Results of the analysis of nonmetallic inclusions in metal samples obtained by the ED method are in good agreement with the results of the determination of oxide nonmetallic inclusions by the FGA method. The method of fractional gas analysis shows the dynamics of changes in the content of various types of oxide nonmetallic inclusions during the secondary (ladle) treatment of steel. It is shown that application of the FGA me thod allows to make analysis of causes of the harmful NMI formation in the metal and to correct operations at ladle treatment.
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| 46. |
- GUO, SHUO, 1987-
(författare)
-
Evaluation of Non-Metallic Inclusions after Deformation and Their Effect on the Machinability of Steel
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The presence of non-metallic inclusions (NMIs) have critical effects on both the mechanical properties and machinability of steels. In the present thesis, one focus is to study the characteristics of deformed sulfides (MnS) for a stainless steel (3R65) and a tool steel (42CrMo4). Three groups of MnS inclusions were detected in the samples taken after deformation of the steel: i) type RS (sulfides with a Rod-like geometry), ii) type PS (sulphides with a plate-like geometry) and iii) type OS (oxy-sulfides). Here, the elongated inclusions present in both stainless and tool steels were studied more in detail using SEM to determine the tendency for the inclusions to break. The results showed that three types of elongated MnS inclusions could be identified, namely UU, UB and BB. Here, ‘U’ represents the unbroken edge(s) of inclusion and ‘B’ represents the broken edge(s) of an inclusion. The presence of these three types of inclusions in samples collected both before and after a heat treatment was studied and the results showed that the heat treatment had a very small effect on the morphologies of the elongated MnS inclusions for both stainless steels (containing <0.1 mass % C) and tool steels (containing 0.42 mass % C). In the second part of the thesis, the characteristics of chips after machining of a 157REM Ce-treated steel and a 157C reference steel was studied. Furthermore, the effect of the NMIs on the chip breakability during machining was determined. The results show that a Ce modification of a 157C steel transforms the NMIs from large size elongated inclusions to small size inclusion with a spherical shape. This leads to an improved machinability of 157C steels. In addition, a newly developed weight distribution of chips (WDC) method, based on the chip weight measurements, was used to determine the tendencies for breaking of chips. The results of this investigation showed that the chips that were obtained from the machining of 157C and the 157REM steels could be classified into the following three types: i) type I chips (with a geometry containing one arc) and having a weight of less than 0.08 g, ii) type II chips (with a geometry containing two arcs) and having weights between 0.08 g and 0.15 g, and iii) type III chips (with a geometry containing three or more arcs) and having weights larger than 0.15 g. From industrial experience, it is known that a high amount of small type I chips will lead to a good chip breakability. The results from the machining test show that the fraction of type I chips from machining of the 157REM steel (65 %) is smaller than from machining of the 157C reference steel (80 %) when using a lower feed rate of 0.4 mm/rev. However, when using a higher feed rate of 0.5 mm/rev, 40 % of the chips belong to type I small chips for the 157REM steel and 14 % for the 157C steel. Based on the conditions used in this study and the obtained results, the following is clear in order to reach the best machinability: i) it is most advantageous to use the 157C steel when using a lower feed rate of 0.4 mm/rev and ii) it is most advantageous to use the 157REM steel when using a higher feed rate of 0.5 mm/rev.
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| 47. |
- Guo, Shuo, et al.
(författare)
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Evaluation of Sulfide Inclusions before and after Deformation of Steel by Using the Electrolytic Extraction Method
- 2021
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- The characteristics of elongated MnS have a critical effect on fatigue anisotropy and all mechanical anisotropies. A comparative investigation of nonmetallic inclusions in both stainless steels and tool steels has been carried out in this study. The inclusion characteristics were investigated using electrolytic extraction (EE) followed by scanning electron microscopy combined with energy-dispersive spectroscopy (SEM-EDS). Overall, three types of MnS inclusions (type I (regular), type II (irregular) and type III (Rod)) were found in tool steels in as-cast samples, which had not been heat-treated. Furthermore, three types of MnS inclusions (Rod-like sulfide (RS), Plate-like sulfide (PS) and Oxysulfide (OS)) were found in samples taken after rolling. Based on the breakability of the elongated MnS, three types of inclusions, Type UU, UB and BB, where U represents the undamaged or unbroken edge of an inclusion and B represents the fragment or broken edge of an inclusion, were studied in both stainless steels and tool steels both before and after additional heat treatment. The effect of heat treatment and dissolving the metal layer during the EE process is also discussed. The results show that both processes have a limited effect on the breakability of inclusions in steels with carbon contents <0.42 mass%.
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| 48. |
- Guo, Shuo, et al.
(författare)
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Evaluation of the chip breakability after machining of Bearing steels based on Weight Distribution Methods
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that a modification of non-metallic inclusions (NMIs) to create especially many smaller inclusions is an important way to improve the machinability of steels. The main focus of this study is the use of a REMs element (Ce) in the liquid steel to modify the NMIs, in order to improve the chip breakability and thereby the machining performance. In evaluating the success of this procedure, a newly developed evaluation method to determine the chip breakability based on chip measurements, which is called the method of weight distribution of chips (WDC), was used. Two similar steel grades were studied, where one was REM treated and the other was a reference. The chips obtained in this study during machining of these two steel grades were classified into three types: i) type I chips having the shape of one arc and a weight of less than 0.08 g, ii) type II chips having the shape of two arcs and weighing between 0.08 g and 0.15 g, and iii) type III chips having a shape consisting of more than three arcs and weights larger than 0.15 g. In order to get the best chip breakability which is good for a fast machining, as many as possible of the chips should be small type I chips. The results show that at a lower feed rate (fn = 0.4 mm/rev), 80 % of chips belong to type I small chips for the reference 157C steel and 65 % of chips belong to type I small chips for the modified 157REM steel. At a higher feed rate (fn = 0.5 mm/rev), the fraction of type I chips is 14 % but it is 40 % in the Ce treated steel grade. Thus, at the lower feed rate the reference 157C steel resulted in the best machinability, but at the higher feed rate, the Ce-treated 157REM steel resulted in the best machinability. This is due to a lower feed rate of 0.4 mm/rev and a lower temperature in the local cutting zone the presence of many MnS inclusions in the reference steel is beneficial to obtain a good chip breakability. However, at the higher feed rate of 0.5 mm/rev and the higher temperature in the local cutting zone, the MnS Inclusions become too soft while the undeformed Ce-containing inclusions remain hard, which enables them to contribute to an improved chip breakability.
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| 49. |
- Hu, X., et al.
(författare)
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Utilization of fly ash and waste lime from pulp and paper mills in the Argon Oxygen Decarburization process
- 2020
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Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 261
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Tidskriftsartikel (refereegranskat)abstract
- Fly ash and waste lime are solid wastes generated in pulp and paper mills. Due to high CaO contents, these secondary lime materials can be potentially utilized in the steelmaking process to partially replace primary lime. In this study, fly ash and waste lime from Swedish pulp and paper mills were made into briquettes and for the first time utilized as slag formers to replace primary lime in a pilot-scale Argon Oxygen Decarburization (AOD) stainless steelmaking process. The purpose was to evaluate how these CaO-containing materials could affect the AOD process and the steel quality. The results show that the S, P and CaO contents in the fly ash and waste lime are important concerns for metallurgical application. Firstly, due to lower CaO contents (61.5% CaO in fly ash and 90.6% CaO in waste lime versus 95.2% CaO in primary lime), utilization of these secondary lime materials could lead to higher slag amounts in the AOD converter. Secondly, due to higher S and P contents (0.40% S and 0.26% P2O5 in fly ash, 0.11% S and 0.75% P2O5 in waste lime versus 0.08% S and 0.01% P2O5 in primary lime), utilization of these secondary lime materials could increase the S and P contents in the steel. The S content in the steel can be controlled during the reduction and desulfurization stages; however, the P content in the steel increases with an increased use of these secondary lime materials. Thirdly, the metallurgical performance of fly ash and waste lime is as good as primary lime when considering the aspects that: (a) utilization of fly ash and waste lime doesn't have negative effects on the decarburization stage nor on the reduction stage during the AOD process; and (b) fly ash and waste lime are as efficient desulfurization agents as primary lime. In future industrial applications, the alkali content and the variations of chemical compositions (especially with respect to S, P and CaO) of these secondary lime materials need to be carefully controlled to ensure a sound metallurgical operation.
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| 50. |
- Janis, Diana, et al.
(författare)
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A Study of Cluster Characteristics in Liquid Stainless Steel and in a Clogged Nozzle
- 2015
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Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 86:11, s. 1271-1278
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Tidskriftsartikel (refereegranskat)abstract
- Clusters of Al2O3 inclusions in a liquid stainless steel (18/8) and in a clogged ZrO2 nozzle after casting were studied during a pilot plant trial. Samples were taken from the melt at different holding times after an addition of 0.1 mass% Al. The characteristics (composition, size, number, and morphology) of clusters and clustered inclusions in the steel samples and in the clogged nozzle were investigated after electrolytic extraction and etching by using SEM. It was found that the Al2O3 inclusions in the clusters are transformed from a spherical into irregular and regular (with sharp edges) shape during the holding time. Most of the inclusions in the clusters (>80%) after a 6 min holding time are regular inclusions, which have sharp edges and flat faces. The size of the inclusions in clusters in the melt increased on average from 1.0 μm at a 1 min to 5.2 μm at a 12 min holding time. While the sizes of different types of inclusions in the clogged nozzle correspond to those present in the liquid steel at respective time, the frequency of spherical inclusions in the clogged nozzle is about 2–4 times larger (particularly near the nozzle wall) compared to that in the melt. Growth and transformation of Al2O3 clusters in the liquid steel at different holding times after an addition of Al and during casting were considered based on the obtained results.
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