| 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. |
- 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
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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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| 5. |
- 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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| 6. |
- 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
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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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| 7. |
- Du, Hongying, et al.
(författare)
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Modification of Non-Metallic Inclusions in Stainless Steel by Addition of CaSi
- 2019
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 9:1
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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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| 8. |
- Du, Hongying, et al.
(författare)
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Using chip weight distribution as a method to define chip breakability during machining
- 2018
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Ingår i: Proceedings 8th Swedish Production Symposium (SPS). - : Elsevier BV. ; 25, s. 309-315
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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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| 9. |
- 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
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Ingår i: Izvestiya Ferrous Metallurgy. - : National University of Science and Technology MISIS. - 0368-0797 .- 2410-2091. ; 62:5, s. 345-352
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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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| 10. |
- 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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| 11. |
- Janis, Diana, et al.
(författare)
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Evaluation of Inclusion Characteristics in Low-Alloyed Steels by Mainly Using the PDA/OES Method
- 2015
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Ingår i: ISIJ International. - : IRON STEEL INST JAPAN KEIDANREN KAIKAN. - 0915-1559 .- 1347-5460. ; 55:10, s. 2173-2181
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Tidskriftsartikel (refereegranskat)abstract
- The characteristics of non-metallic inclusions (such as number, size and volume fraction) in liquid steel samples taken during ladle treatment and casting of industrial heats of two low-alloyed Ca-treated steel grades were evaluated by using the Pulse Distribution Analysis with Optical Emission Spectroscopy (PDA/OES) method. These results were compared to data obtained by Scanning Electron Microscope observations of inclusions after electrolytic extraction from steel samples (the EE method). It was found that the PDA/OES method can be used for a relative estimation of the homogeneity of the distribution of non-metallic inclusions in steel samples. Bottom and middle parts of the steel samples showed more homogeneous results with respect to the characteristics of the investigated Al2O3, CaO-Al2O3 and CaO-Al2O3-CaS inclusions. The numbers of inclusions in the size ranges 2.0-5.7 mu m and 1.4-5.7 mu m in samples taken before and after a Ca addition, respectively, showed a relatively good agreement between both methods. Furthermore, the calculated volume fractions for inclusions in the size range 2-13 mu m obtained by the PDA/OES method agreed satisfactorily well with those obtained from the EE method. Finally, the minimum sizes of inclusions in steel samples, which can reliably be detected by the PDA/OES method, were estimated for steels with different concentrations of Al in steel and Al2O3 in inclusions.
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| 12. |
- Jarnerud, Tova, et al.
(författare)
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Briquetting of wastes from pulp and paper industries by using AOD converter slag as binders for application in metallurgy
- 2019
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 12:18
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Tidskriftsartikel (refereegranskat)abstract
- A number of carbon-rich (containing up to 47 wt% C) and lime-rich (containing up to 96 wt% of CaO-compounds) waste products from the pulp and paper industries can be used in iron and steel industry as fuels and slag formers for various metallurgical processes such as blast furnaces (BF), cupola furnaces (CF), argon oxygen decarburization (AOD) converters and electric arc furnaces (EAF). In most cases, these wastes consist of different size powders. In order to facilitate loading, transportation and charging of these powder wastes, briquetting is required. In this study, a pulverized AOD slag was tested as a binder component for briquetting of CaO-containing wastes (such as mesa, lime mud and fly ash) from pulp and paper industries. Moreover, mechanical testing of the possibilities for loading, transportation and unloading operations were done, specifically drop test trials were done for briquettes with different chemical compositions and treatments such as heating and storage. The results showed that an addition of 10-20% of AOD slag as a binder component followed by heat-treatment at 850 °C significantly improved the mechanical properties of the CaO-containing briquettes. An application of these briquettes will significantly reduce the consumption of natural resources (such as nature lime) in the metallurgical processes. Moreover, it can reduce the landfill area of wastes from pulp and paper industries, which is important from an environmental point-of-view.
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| 13. |
- Jarnerud, Tova, 1976-
(författare)
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Utilization of recovered lime-containing materials from pulp and paper industries as slag formers in stainless steel production
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, major efforts have been made to develop a more circular economy. The desire to reuse, remanufacture and recycle materials are important for the development towards a sustainable society. An extended lifespan of materials helps to reduce the amount of waste kept in landfills, as well as to reduce the extraction of natural resources. Pulp and paper and steel industries are two of the largest export industrial sectors in Sweden. It is well known that the pulp and paper industries also generates large amounts of organic and inorganic wastes, of which a significant part is kept in landfills. Year by year deposit of wastes in landfills is becoming more difficult to handle and expensive due to stronger regulations and requirements regarding the environment. During Electric Arc Furnace (EAF) and Argon Oxygen Decarburization (AOD) stainless steelmaking operations, burnt lime (primary lime) is charged together with other slag forming materials in the furnace or converter to attain a specific basicity of the slag and to achieve purification from unwanted elements by chemical reactions in the steel.However, a number of CaO-containing wastes from pulp/paper mills can be used as slag formers in steelmaking processes to replace the currently used burnt natural lime, since the use of this primary lime does not conform with the closing the loop idea that is being prioritized in modern society. This thesis presents results from preliminary experiments for examining the replacement of primary lime with secondary lime from pulp and paper production waste as slag formers in EAF and AOD converters. The obtained results showed a possibility of using up to 30% CaO from secondary lime as a replacement for primary lime in the EAF. Furthermore, the amount of ferrosilicon alloys additions can be decreased by up to 3kg/ton of steel. For the AOD process the use of secondary lime doesn´t have any negative effects on the decarburization process and reduction process. Furthermore, it has similar desulphurization functions as the primary lime. However, the phosphorus content in the metal was slightly increased. Thus, the replacement ratio of secondary lime will be limited by the acceptable phosphorus level in the final steel due to higher phosphorus content in wastes from pulp and paper mills compared to that in primary lime. Moreover, it was revealed during this study that slags from AOD converters can be used as binding agents for briquetting of these secondary lime materials. These results shows that waste/by products from two major industries can be used to make metallurgical briquettes, uniting two major industrial sectors in a circular symbiosis towards a more sustainable future.
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| 14. |
- Karasev, Andrey, et al.
(författare)
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Characterization of non-metallic inclusions in corrosion -resistance nickel - Based EP718 and 718 alloys by using electrolytic extraction method
- 2019
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Ingår i: E3S Web of Conferences. - : EDP Sciences. - 2267-1242.
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Konferensbidrag (refereegranskat)abstract
- It is known that non-metallic inclusions (NMI) that are formed during steel production and heat treatment can significantly affect the properties of final steel products. Therefore, it is very important to be able to determine the content of harmful NMI in steels. Nickel-based alloys are widely used in the oil and gas recovery industry, due to a good combination of strength and corrosion properties. Earlier studies have shown that the corrosion properties in immersion test and electrochemical tests for Ni-based EP718 alloys are slightly lower than that for 718 alloys. The focus in this study was the influence of different NMI on the corrosion resistance of these alloys. The characteristics of inclusions (such as size, morphology, and chemical composition) were analysed by using the electrolytic extraction method followed by three-dimensional investigations using SEM in combination with EDS. It was found that some non-metallic inclusions in EP718 alloys significantly reduce its corrosion resistance. It was also shown that a primary dissolution of the metal matrix occurs around certain inclusions during electrolytic extraction. Based on obtained results, the corrosion active non-metallic inclusions can be determined in these Nickel-base alloys and some recommendations for optimization of their production technology can be formulated.
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| 15. |
- Karasev, Andrey, et al.
(författare)
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Estimation of non-metallic inclusions in industrial Ni based alloys 825
- 2017
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 88:4
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that inclusions affect the properties of the steel and other alloys. The importance of understanding the behavior of the inclusions during production can never be overstated. This study has examined the main types of big size (>10μm) inclusions that exist in Ni-based Alloy at the end of ladle treatment and after casting during industrial production of Ni based Alloys 825. Sources, mechanisms of formation and behavior of different type large size inclusions in Alloy 825 are discussed based on 2 and 3D investigations of inclusion characteristics (such as, morphology, composition, size, and number) and thermodynamic considerations. The large size inclusions found can be divided in spherical (Type I and II) inclusions and in clusters (Type III-V). Type I-A inclusions (Al2O3-CaO-MgO) originate from the slag. Type I-B inclusions and Type II inclusions consist of CaO-Al2O3-MgO and Al2O3-TiO2-CaO, respectively. Both types originate from the FeTi70R alloy. Type III clusters (Al2O3-MgO-CaO) are formed during an Al deoxidation of the Ni-based alloy. Type IV clusters (Al2O3-TiO2-CaO) formed from small inclusions, which are precipitated in local zones which contain high Ti and Al levels. These clusters are transformed to Type III clusters over time in the ladle. Finally, Type V clusters are typical TiN clusters.
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| 16. |
- Kellner, Hans E. O., et al.
(författare)
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Effect of additions of FeTi70R alloy on inclusion characteristics in Fe-40Ni-20Cr steels
- 2015
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Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - : Chinese Society for Metals. ; , s. 797-800
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Konferensbidrag (refereegranskat)abstract
- It is well known that ferroalloys, which are used for alloying of different steels, contain different harmful non-metallic inclusions and impurities. As this can significantly affect the cleanliness of the steel (especially in production of high quality alloy steels), it is important to know what happens when ferroalloys are added to the melt. In this work, characteristics of non-metallic inclusions (such as composition, size and number) were investigated in the commercially produced FeTi70R ferroalloy (∼70% Ti), which is used in the steelmaking industry for deoxidation and alloying of different steel grades. It was found that this FeTi alloy contains some amount of complex oxides, which sizes can reach 50 - 150μm. A composition analysis of these complex inclusions showed that they contain mostly CaO (about 70%-98%) and TiOx-SiO2 (about 2%-28%). These large size inclusions can significantly decrease the cleanliness of the cast steels (especially by addition of FeTi alloys for a final correction of the steel composition before casting) and their final mechanical properties. Processes of transformation of these and other non-metallic inclusions, which are present in the FeTi70R ferroalloy, were investigated after immersion of this ferroalloy into a melt of a Fe or a Fe-40Ni-20Cr steel. Moreover, the non-metallic inclusions were investigated in samples taken at different moments during the industrial production of a Fe-40Ni-20Cr steel alloyed with the FeTi70R ferroalloy. The inclusions existing during the production were then compared to those that evolved during the immersion of a FeTi70 alloy in the Fe-40Ni-20Cr melt. This helps to understand what type of inclusions that formed when FeTi70R alloys are added to a Fe-40Ni-20Cr melt and to estimate the harmful effect of these non-metallic inclusions on the quality of this steel grade during commercial production.
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| 17. |
- Kellner, Hans E O, et al.
(författare)
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Evolution of Non-Metallic Inclusions from FeTi70R Alloys during Alloying of Fe-40Ni-20Cr Steels
- 2016
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Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X.
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the composition, size, and number of large non-metallic inclusions (>20μm) are investigated in a commercial refined FeTi70R alloy, which is used for deoxidation and alloying of different industrial high-quality steels. It is found that this ferroalloy contains different complex oxide inclusions, which sizes vary from 20 to 260μm. These different complex inclusions contain mostly CaO, SiO2, and TiOx. When adding FeTi70R alloy in the steel during the final stage of ladle treatment, these large size inclusions can significantly decrease the cleanliness and mechanical properties of steel. Therefore, the evolution and behavior of these inclusions after addition of this ferroalloy into the liquid iron or Fe-40Ni-20Cr steel are investigated in laboratory experiments. In addition, the results from the laboratory scale experiments are compared to results obtained from industrial heats using Alloy 825. A consideration of the evolution mechanism of large inclusions after an addition of a FeTi70R alloy helps to understand their behavior in the melt. It also helps to estimate their possible harmful effects on the quality of this steel grade during commercial production.
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| 18. |
- Kellner, Hans, 1989-, et al.
(författare)
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Effect of the Stirring Mode on the Behavior of Al2O3–MgO Particles and Clusters during Ladle Treatment of Ni-based Alloy 825
- 2017
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Ingår i: Steel Research International. - Weinheim : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 87
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that inclusions affect the properties of alloys. Therefore, the importance of understanding what inclusions exist and how they behave cannot be overstated. This study has examined the behavior of Al2O3–MgO particles and clusters in the melt during the ladle treatment of Alloy 825, who is a Ni-based Alloy. The effect of different stirring directions of electromagnetic stirring in combination with gas stirring is discussed based on three-dimensional investigations of the clustered particles. More specifically, the composition, size, and number of particles and clusters are determined after electrolytic extraction of metal samples by using SEM in combination with EDS. The results show that the agglomeration of Al2O3–MgO particles in the melt is faster for an upward induction stirring combined with a gas stirring in comparison to a downward stirring combined with a gas stirring. However, the total removal of clusters from the melt is more effective when using a downward induction stirring compared to when using an upward induction stirring, especially for large size clusters (>11.2 mm). The effect of the different stirring modes on the behavior of the Al2O3–MgO particles and clusters in the melt for the ladle treatment experiments agree with the theoretical predictions based on Stokes’, Brownian, and Turbulent collisions.
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| 19. |
- Kellner, Hans, 1989-, et al.
(författare)
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Investigations of TiN Particles and Clusters during Ladle Treatments of Ni-based Alloy 825 using Different Stirring Modes
- 2017
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Ingår i: ISIJ International. - 0915-1559 .- 1347-5460. ; 58:2
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Tidskriftsartikel (refereegranskat)abstract
- Today, Titanium is often used in steelmaking not only for deoxidation but also for micro-alloying and alloying for a wide range of steel grades. Therefore, many studies are focused on investigations on the formation and behavior of Ti-containing non-metallic inclusions (such as oxides, nitrides and carbides) during production of different Ti-containing steels and their effect on final steel properties. This study has examined the behavior of TiN clusters and particles in the melt during the ladle treatment of Alloy 825 containing up to 1.2wt% of Ti. The industrial trials were performed at the end of the ladle treatment by using argon gas in combination with electromagnetic stirring using an upwards or a downwards stirring direction. Metal samples were taken before and after ladle treatment to enable three-dimensional investigations of non-metallic inclusions and clusters. The composition, size and number of particles and clusters were determined after electrolytic extraction of the metal samples by using SEM in combination with EDS. It was found that agglomerations of TiN clusters and particles in the melt are faster during an upwards stirring in comparison to a downwards stirring. However, the removal of clusters from the melt is more effective when using a downwards stirring direction compared to when using an upwards stirring in dombination with gas stirring. It was also found that the Turbulent collision is the dominant factor for the agglomeration of TiN particles in the melt.
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| 20. |
- Kellner, Hans, 1989-
(författare)
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Study of Non-metallic Inclusion in Alloy 825
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that inclusions affect the properties of steels and alloys. Therefore, it is important to understand what type of inclusions that exist and how they behave and especially with a focus on large size inclusions. Thus, the large size non-metallic inclusions in ferroalloy FeTi70R were investigated in two dimensions (2D) by using scanning electron microscopy (SEM) in combination with an energy dispersive technique (EDS). It was found that the FeTi70R ferroalloy contain complex oxide inclusions consisting mostly of CaO, SiO2 and TiOx. Furthermore, experimental trials were performed to investigate how these inclusions behaved when entering a melt. More specifically, a comparison between pure Fe and an Alloy 825 grade were made. These results determined the parameters effect on the transformation of the inclusions in the melt.The large size non-metallic inclusions in Alloy 825 during the ladle treatment were investigated during industrial trials by using both two dimensional (2D) and three dimensional (3D) microscopic investigations. The results showed that inclusions consisted of spherical oxides and clusters made up of oxides and nitrides. Further investigations found that the spherical inclusions were transformed from existing NMI in the FeTi70R ferroalloy and slag particles. As for the clusters, they originate from deoxidation products. Furthermore, small inclusions precipitated in the local zones around the added FeTi70R ferroalloy and titanium nitrides. Investigations also found that only Al2O3-MgO and TiN clusters exist after casting.Industrial trials were performed during the last period of the ladle treatment and using a combined electromagnetic (EMS) and gas (GS) stirring. The purpose to investigate the effect of different EMS directions on the agglomeration and on the removal of Al2O3-MgO and TiN clusters. The investigations were then performed in 3D after an electrolytic extraction of the metal samples. The results show that electromagnetic stirring in the upwards direction is best for the agglomeration of the Al2O3-MgO and TiN clusters. However, electromagnetic stirring in the downwards direction is more effective to remove clusters from the melt. This is in agreement with the theoretical predictions based on Stokes’, Brownian and Turbulent collisions. Also, the calculations showed that for Al2O3-MgO clusters with sizes <20 μm the Turbulent collision is the defining factor for agglomeration. However, both Stokes’ and Turbulent collisions are dominant for larger inclusions. For the TiN clusters, turbulent collisions is the dominant factor.Further investigations with more heats and stirring modes were done by using 2D microscopic investigations. More specifically, the number, size, composition and morphology of different inclusions were determined by using SEM in combination with EDS and Inca Feature analyses. The results show that the EMS in downwards direction with a 0.04 m3 min-1 gas flow rate promotes a general removal of Al2O3-MgO and TiN inclusions. Furthermore, that the upwards EMS direction promotes a drastically increase of inclusions having an equivalent size smaller than 11.2 μm. Moreover, the stirring with a 0.02 m3 min-1 gas flow rate has a better removal rate for both downwards and upwards stirring directions compared to the stirring with a 0.04 m3 min-1 gas flow rate. However, no influence on the inclusion composition and morphology could be seen from the different stirring modes.
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| 21. |
- Kellner, Hans, et al.
(författare)
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TiN Particles and Clusters during Ladle Treatments of Ni-based Alloy 825 using Different Stirring Modes
- 2018
-
Ingår i: ISIJ International. - : IRON STEEL INST JAPAN KEIDANREN KAIKAN. - 0915-1559 .- 1347-5460. ; 58:2, s. 292-298
-
Tidskriftsartikel (refereegranskat)abstract
- Today, titanium is often used in steelmaking not only for deoxidation but also for micro-alloying and alloying for a wide range of steel grades. Therefore, many studies are focused on investigations on the formation and behavior of Ti-containing non-metallic inclusions (such as oxides, nitrides and carbides) during production of different Ti-containing steels and their effect on final steel properties. This study has examined the behavior of TiN clusters and particles in the melt during the ladle treatment of Alloy 825 containing up to 1.2 wt% of Ti. The industrial trials were performed at the end of the ladle treatment by using argon gas in combination with electromagnetic stirring using an upwards or a downwards stirring direction. Metal samples were taken before and after ladle treatment to enable three-dimensional investigations of non-metallic inclusions and clusters. The composition, size and number of particles and clusters were determined after electrolytic extraction of the metal samples by using SEM in combination with EDS. It was found that agglomerations of TiN clusters and particles in the melt are faster during an upwards stirring in comparison to a downwards stirring. However, the removal of clusters from the melt is more effective when using a downwards stirring direction compared to when using an upwards stirring in combination with gas stirring. It was also found that the Turbulent collision is the dominant factor for the agglomeration of TiN particles in the melt.
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| 22. |
- Nabeel, Muhammad, 1987-
(författare)
-
A study of micro-particles in the dust and melt at different stages of iron and steelmaking
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The dust particles generated due to mechanical wear of iron ore pellets and clusters formed in molten stainless steel alloyed with rare earth metals (REM) are considered in this study. Firstly, the influence of the characteristics of iron ore pellets, applied load on a pellet bed and partial reduction of the pellets on the size distribution of the generated dust was investigated. Secondly, REM clusters are investigated to evaluate the size distribution of the clusters. Also, an extreme value distribution (EVD) analysis has been applied for the observed REM clusters.The large sized pellets showed 10-20% higher wear rate than small sized pellets during wear in a planetary mill. Moreover, an increase of ~67% was observed in the friction and dust generation in the pellet bed as the applied load increased from 1 to 3 kg. Also, it was observed that a higher friction in the pellet bed can lead to an increased amount of airborne particles. The mechanical wear experiments of pellets reduced at 500 °C (P500) and 850 °C (P850) showed that P500 pellets exhibit ~16-35% higher wear rate than unreduced pellets. For the P850 pellets, the wear is inhibited by formation of a metallic layer at the outer surface of the pellets. The mechanism of dust generation has been explained using the obtained results.A reliable cluster size distribution of REM clusters was obtained by improving the observation method and it was used to explicate the formation and growth mechanism of REM clusters. The results show that the growth of clusters is governed by different types of collisions depending on the size of the clusters. For EVD analysis three different size parameters were considered. Moreover, using the maximum length of clusters results in a better correlation of EVD regression lines compared to other size parameters. Moreover, a comparison of predicted and observed maximum lengths of clusters showed that further work is required for the application of EVD analyses for REM clusters.
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| 23. |
- Nabeel, Muhammad, et al.
(författare)
-
Characteristics of iron ore pellets and their influence on dust generation due to wear
- 2015
-
Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - : Chinese Society for Metals. ; , s. 966-969
-
Konferensbidrag (refereegranskat)abstract
- In the blast furnace process flue dust is generated, which ends up in the off-gases. This results in a loss of valuable raw materials and an increased energy need per produced ton of hot metal. The flue dust also have adverse effects on the environment. Thus, this study is focused on the investigation of the mechanical wear of iron ore pellets. The influence of pellet characteristics, such as size, weight, density and hardness, on the wear mechanism has been investigated. It has been observed that pellets with larger size show a higher wear rate as compared to small sized pellets. Moreover, the dust generated during wear experiments has been analyzed to obtain particle size distributions.
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| 24. |
- Nabeel, Muhammad, et al.
(författare)
-
Characterization of Dust Generated during Mechanical Wear of Partially Reduced Iron Ore Pellets
- 2017
-
Ingår i: Steel Research International. - : WILEY-V C H VERLAG GMBH. - 1611-3683 .- 1869-344X. ; 88:9
-
Tidskriftsartikel (refereegranskat)abstract
- During reduction in a blast furnace (BF), the iron ore pellets undergo structural changes, which facilitate dust generation due to the mechanical wear/disintegration of the pellets. The generated dust decreases the permeability and productivity of the BF process. Thus, this study investigates the mechanical wear of iron ore pellets reduced at 500 degrees C (P500) and 850 degrees C (P850) and compares the results to the wear of unreduced pellets (P25). Moreover, the dust generated during the wear experiments is also characterized. It is found that pellets reduced at 500 degrees C exhibit a approximate to 16-35% higher wear rate than reference unreduced pellets. For the pellets reduced at 850 degrees C, the mechanical wear is inhibited by a formation of a metallic layer at the outer surface of the pellets. Further, the dust generated due to mechanical wear of reduced pellets contain 3-6 times higher amount of coarse particles (>20m) as compared to the dust from unreduced pellets. The obtained results are explained on the basis of the structural changes, which take place during the reduction of pellets.
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| 25. |
- Nabeel, Muhammad, et al.
(författare)
-
Characterization of Inclusions in 3rd Generation Advanced High-Strength Steels
- 2019
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 50:4, s. 1674-1685
-
Tidskriftsartikel (refereegranskat)abstract
- Samples taken from laboratory-produced 3rd generation advanced high-strength steels, solidified at a low cooling rate, have been investigated to study the characteristics of non-metallic inclusions. Two steels, containing 2 and 5 pct Mn content, were produced for this purpose. A higher number of total inclusions were observed in 5 pct Mn steel. The four main types of inclusions observed were Al2O3, AlN, MnS, and AlSiMn-oxide. These classes were divided into subclasses according to variations in their chemistry. The major subclasses of AlN inclusions are either plate-like or regular in shape and have different size distributions. Thermodynamic calculations suggest that plate-like AlN inclusions are formed at the initial stage of solidification, while faceted/regular-shaped inclusions are precipitated toward the end of solidification. Moreover, it was found that the size of nitride inclusions is related to their N content. This phenomenon is discussed from the viewpoint of nucleation theory.
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| 26. |
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| 27. |
- Nabeel, M., et al.
(författare)
-
Characterization of inclusions in high-Mn steel using two-dimensional and three-dimensional methods
- 2019
-
Ingår i: Iron & Steel Technology. - : Association for Iron & Steel Technology. - 1547-0423. ; 16:7, s. 74-82
-
Tidskriftsartikel (refereegranskat)abstract
- The characteristics of inclusions in high-manganese steel samples from laboratory-scale experiments were investigated. This was done by two-dimensional and three-dimensional methods. In the two-dimensional investigations, inclusions on polished cross-sections were observed by using automatic scanning electron microscopy analysis. For the three-dimensional investigations, inclusions collected on a film filter after electrolytic extraction were observed. It was found that electrolytic extraction could be successfully applied to high-manganese steels. Further, automatic analysis, which is a common practice in steel industry, has limitations for the detection and classification of nitride inclusions, whereas it was possible to detect nitrides using the three-dimensional method.
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| 28. |
- Nabeel, Muhammad, et al.
(författare)
-
Evaluation of Dust Generation during Mechanical Wear of Iron Ore Pellets
- 2016
-
Ingår i: ISIJ International. - 0915-1559 .- 1347-5460. ; 56:6, s. 960-966
-
Tidskriftsartikel (refereegranskat)abstract
- Iron ore pellets undergo mechanical wear during handling, transportation and use in a blast furnace. This results in a loss of valuable raw materials and causes environmental problems in form of dust in off-gases from a blast furnace. Thus, this study is focused on the investigation of the mechanical wear of iron ore pellets and the dust formation. The characteristics of industrial pellets (such as size, weight, density and hardness) have been investigated. Moreover, the influence of pellet characteristics on the wear mechanism (sliding/abrasion and impact/collisions wear) and the characteristics of generated dust have been investigated. It was observed that the size of pellets can influence the wear rate under the given experimental conditions. The pellets with larger size (13.5 < d(eq) < 15.0 mm) showed 10-20% higher wear rate as compared to small sized pellets (9.5 < d(eq) < 12.50 mm). SEM studies of the dust generated during wear experiments inferred that larger contribution of impact/collisions in wear of pellets is the reason for the higher wear rate of large size pellets. Further, a relationship between the critical diameter of dust particles, which can be removed with off-gases from the blast furnace, and the velocity of off-gases in top part of blast furnace was developed.
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| 29. |
- Nabeel, Muhammad, et al.
(författare)
-
Formation and Growth Mechanism of Clusters in Liquid REM-alloyed Stainless Steels
- 2015
-
Ingår i: ISIJ International. - 0915-1559 .- 1347-5460. ; 55:11, s. 2358-2364
-
Tidskriftsartikel (refereegranskat)abstract
- REM-oxide clusters extracted from 253MA stainless steel grade samples from a pilot trial were investigated using a 2%TEA electrolyte. The samples were taken from liquid steel at different holding times after an addition of an appropriate amount of mischmetal. Thereafter, SEM in combination with EDS was deployed for three dimensional (3D) investigations of the characteristics of the extracted REM-oxide clusters. A reliable cluster size distribution (CSD) was obtained by improving the observation method and it was used to explicate the formation and growth mechanism of REM-oxide clusters. A correlation between morphology of clusters and their growth rate was found. This was used to divide the clusters into two different groups, which form and grow in accordance to different mechanisms. The results also show that the growth of clusters is governed by different types of collisions dependent up on size of the clusters. It has been concluded that for REM-oxide clusters turbulent collisions are the main controlling mode for the growth rate.
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| 30. |
- Nabeel, Muhammad, et al.
(författare)
-
Friction Forces and Mechanical Dust Generation in an Iron Ore Pellet Bed Subjected to Varied Applied Loads
- 2017
-
Ingår i: ISIJ International. - : IRON STEEL INST JAPAN KEIDANREN KAIKAN. - 0915-1559 .- 1347-5460. ; 57:4, s. 656-664
-
Tidskriftsartikel (refereegranskat)abstract
- Iron ore pellets degrade and generate dust during transportation and handling as well as during the iron making process. This leads to material losses and effects the process efficiency in a negative manner. In order, to reduce the generation of dust it is important to understand the influence of process parameters on the dust formation. An experimental setup was used to measure the dust generation and friction forces caused by abrasion of iron ore pellets in a closed pack bed. A varied load of 1 to 3 kg was applied on the pellet bed but at a constant air flow rate to capture the airborne dust particles. It was observed that an increase of similar to 67% is observed in the friction and the dust generation in the bed as the applied load increased from 1 to 3 kg. Moreover, the evaluation of the particle size distribution of the generated dust showed that a higher friction in the pellet bed can lead to an increased amount of airborne particles. Moreover, it has been shown that in an air flow the morphology and the orientation of dust particles can influence the air velocity required to transport the particles upwards.
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| 31. |
- Roos, Erik, et al.
(författare)
-
Effect of Si and Ce Contents on the Nozzle Clogging in a REM Alloyed Stainless Steel
- 2015
-
Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 86:11, s. 1279-1288
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of the cerium and silicon contents on the castability of a REM-alloyed stainless steel was investigated by using pilot scale experiments. The trials were carried out with three different silicon concentrations: i) low (LSi; Si < 0.5%); ii) middle (MSi; Si approximate to 0.8-1.4%); and iii) high (HSi; Si approximate to 1.5-1.9%). During the casting, the liquid steel was teemed out through a zirconia nozzle located at the bottom of the furnace. The results showed that the nozzle clogging did drastically increase with increasing concentrations of Si and Ce up to levels larger than the critical contents (>= 1.5% Si and >= 0.05% Ce) in the cast HSi steel. In addition, the Ce content in a cast steel was found to increase linearly with an increased concentration of Si, due to the determinant effect of the Si content on an initial content of O in the melt before an addition of mischmetal. Finally, it was found that the concentration of insoluble Ce (Ce-insol.) determines the amount of inclusions and clusters in steel samples. Overall, soluble Ce concentrations larger than 250 ppm were found to be an important reason for fast nozzle clogging during casting.
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| 32. |
- Sidorova, Elena, et al.
(författare)
-
Modification of Non-Metallic Inclusions in Oil-Pipeline Steels by Ca-Treatment
- 2019
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 9:4
-
Tidskriftsartikel (refereegranskat)abstract
- Corrosion rate in different steel grades (including oilfield pipeline steels) is determined by the presence of non-metallic inclusions (NMI) in steels. Specifically, the effect of different inclusions on the quality of steels depends on their characteristics such as size, number, morphology, composition, and physical properties, as well as their location in the steel matrix. Therefore, the optimization and control of NMI in steels are very important today to obtain an improvement of the material properties of the final steel products. It is well known that a Ca-treatment of liquid steels in ladle before casting is an effective method for modification of non-metallic inclusions for improvement of the steel properties. Therefore, the NMI characteristics were evaluated in industrial steel samples of low carbon Ca-treated steel used for production of oil-pipelines. An electrolytic extraction technique was used for extraction of NMI from the steel samples followed by three-dimensional investigations of different inclusions and clusters by using SEM in combination with EDS. Moreover, the number and compositions of corrosion active non-metallic inclusions were estimated in hot rolled steel samples from two different heats. Finally, the corrosion resistance of these steels can be discussed depending on the characteristics of non-metallic inclusions present in the steel.
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| 33. |
- Sjöqvist Persson, Eva, 1962-, et al.
(författare)
-
Studies of three dimension inclusions from ESR remelted and conventional steel
- 2017
-
Ingår i: LMPC 2017, Liquid Metal Processing and Casting Conference, TMS, USA, Philadelphia, USA, 10-13 September 2017.. - TMA, USA.
-
Konferensbidrag (refereegranskat)
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| 34. |
- Wang, Yong, et al.
(författare)
-
An Investigation of Non-Metallic Inclusions in Different Ferroalloys using Electrolytic Extraction
- 2019
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 9:6
-
Tidskriftsartikel (refereegranskat)abstract
- Ferroalloys are integral constituents of the steelmaking process, since non-metallic inclusions (NMIs) from ferroalloys significantly influence the transformation of inclusions present in liquid steel or they are directly involved in casted steel. In this study, the characteristics of inclusions (such as the number, morphology, size, and composition) in different industrial ferroalloys (FeV, FeMo, FeB, and FeCr) were investigated using the electrolytic extraction (EE) technique. After extraction from the ferroalloy samples and filtration of the solution, the inclusions were investigated on a film filter. The three-dimensional (3D) investigations were conducted using a scanning electron microscopy in combination with energy dispersive spectroscopy (SEM-EDS). The characteristics of inclusions observed in the ferroalloys were compared with previous results and discussed with respect to their possible behaviors in the melt and their effects on the quality of the cast steels. The particle size distributions and floatation distances were plotted for the main inclusion types. The results showed that the most harmful inclusions in the ferroalloys investigated are the following: pure Al2O3 and high Al2O3-containing inclusions in FeV alloys; pure SiO2 and high SiO2-containing inclusions in FeMo alloys; Al2O3 and SiO2-containing inclusions in FeB alloys; and MnO-Cr2O3, Al2O3, and Cr2O3-based inclusions in FeCr alloys.
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| 35. |
- Xuan, Changji, et al.
(författare)
-
Evaluation of Agglomeration Mechanisms of Non-metallic Inclusions and Cluster Characteristics Produced by Ti/Al Complex Deoxidation in Fe-10mass% Ni Alloy
- 2016
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 56:7, s. 1204-1209
-
Tidskriftsartikel (refereegranskat)abstract
- The characteristics of non-metallic single inclusions and clusters formed in a Fe-10mass% Ni alloy deoxidized with Ti, Al and Ti/AI were investigated. Laboratory experiments were performed, and samples were taken after deoxidation. The composition, number and size of the single inclusions and clusters in the samples were determined using SEM in combination with EDX. The agglomeration mechanism and collision rates of inclusions and clusters were considered in the Al and Ti/AI deoxidation experiments. The obtained results showed that the number and average size of clusters in all samples of the complex Ti/AI experiment are drastically smaller than those in the Al experiment. The Brownian, Stokes' and turbulent collisions between particle-particle in clusters, particle-cluster and cluster-cluster were evaluated to determine the cluster formation in the different deoxidation experiments depending on the holding time.
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| 36. |
|
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| 37. |
- Yang, Annika Fang, et al.
(författare)
-
Behavior of metal droplets in slags during desulphurization of hot metal
- 2015
-
Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - : Chinese Society for Metals. ; , s. 80-83
-
Konferensbidrag (refereegranskat)abstract
- An intensive desulphurization of hot metal can result in significant additional losses of iron in the slag. These iron losses during desulphurization of hot metal can reach a value of 1.5%-2.5% of the total amount of processed hot metal. The majority of the iron losses are present in the slag in form of different iron droplets. Therefore, the knowledge of the formation and behavior of these droplets in slags can help to significantly decrease the iron losses during desulphurization of hot metal. The characteristics of different iron droplets such as the morphology, number, size, composition and solidification structure were investigated in industrial slag samples taken from a ladle after desulphurization of hot metal. It was found that different morphologies of iron droplets in slag depend on the mechanism for the dispersion of the hot metal droplets into the slag, the characteristics of slag (amount, viscosity, melting temperature, etc.) as well as some technological parameters (mode and intensity of injection of reagents for desulphurization, stirring rate of hot metal in the ladle, etc.). The main mechanisms for involving of different metal droplets into the slag and their behavior during desulphurization process are discussed based on the obtained characteristics of the metal droplets.
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| 38. |
- Yang, Annika Fang, et al.
(författare)
-
Characterization of Metal Droplets in Slag after Desulfurization of Hot Metal
- 2015
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 55:3, s. 570-577
-
Tidskriftsartikel (refereegranskat)abstract
- Iron losses in slag during an intensive desulfurization of hot metal can reach 0.6-1.1% from the total amount of processed hot metal. The characteristics of different metal droplets (such as morphology, number, size, composition and solidification structure) in industrial slag samples after desulfurization were investigated using SEM. All metal droplets in the slag were classified into three groups according to morphology: Type A - spherical/oval; Type B - spherical/irregular; Type C - irregular. Thereafter, some mechanisms for involving of different metal droplets into the slag during desulfurization process were studied based on obtained characteristics of metal droplets. Moreover, a possibility to remove those metal droplets from the liquid slag was estimated based on Stokes law. In addition, the effect of some parameters (such as slag viscosity and size of different metal droplets in this slag) on the possibility to reduce the iron losses during desulfurization of hot metal was considered.
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| 39. |
- Yang, Annika Fang, et al.
(författare)
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Effect of Nepheline Syenite on Iron Losses in Slags during Desulphurization of Hot Metal
- 2015
-
Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X.
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of injection of nepheline syenite (NS) together with CaC2 and C on the iron losses in form of metal droplets in a slag during desulphurization of hot metal is investigated in industrial trials. The characteristics of different metal droplets (such as morphology, number, size and composition) in slags of trials without and with injection of a NS are investigated using SEM. All metal droplets in the slag are classified into three groups according to morphology: Type A-spherical/oval; Type B-spherical/irregular; Type C-irregular. It is found that the addition of NS influences the compositions of hot metal, slag and metal droplets in slag. As a result, the amount (area fraction) and size of metal droplets decreased for Type A and B and increased significantly for Type C droplets present in the slag. The effect of injection of nepheline syenite together with CaC2 and C on the iron losses in form of metal droplets in a slag during desulphurization of hot metal is investigated in industrial trials. The characteristics and behavior of different metal droplets in slags of trials without and with injection of a nepheline syenite are investigated.
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| 40. |
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| 41. |
|
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| 42. |
- Yoshioka, Takanori
(författare)
-
Parameters influencing inclusion compositions in Al-killed steel melts during a secondary refining process
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study was carried out to clarify the factors influencing the evolution of inclusions in Al-killed steel melts during a secondary refining process. First, a case-hardening steel was the subject of study to understand the factors influencing the inclusion compositions in the steel melt. During the LF process, inclusions were transformed from the Al2O3 phase, which was the primary deoxidation product, to both MgO·Al2O3 and CaO-Al2O3-MgOliq phases simultaneously. This composition transition during the LF process occurred by composition evolutions toward thermodynamically stable phases. After the RH process, the inclusion compositions primarily consisted of the Al2O3 and CaO-Al2O3 phases. MgO·Al2O3 inclusions were removed, while the CaO-Al2O3 inclusions remained during the RH process. This behavior can be understood in terms of the interfacial properties of the oxide phases in a steel melt. The detected Al2O3 inclusions were considered to be generated by reoxidation during the RH treatment. Thus, it was confirmed that the equilibrium states, removal, and generation of inclusions determine the inclusion compositions in an Al-killed steel melt during an LF-RH refining process. Subsequently, the effect of high Al contents in a steel melt on the change in inclusion compositions during the LF-RH process was studied. Due to the high Al content in the steel melt, the thermodynamic driving forces for Al2O3 modification became lower than those in ordinary Al-killed steels. Therefore, the degree of inclusion evolution was restricted. This contributed to the low CaO contents in the inclusions. Due to the low CaO contents, the removability of the inclusions remained high throughout the LF-RH process. According to thermodynamic calculations, the low T.O contents in this steel grade are due to the low insoluble O contents. This can be explained by the fast removal of inclusions. Because the inclusions were removed smoothly, the CaO content in the inclusions was lower than that in the thermodynamically stable phase. In addition, a study was carried out to understand the formation and behavior of the CaS phase in an Al-killed high-S steel during the LF-RH process without Ca-treatment. In the initial stage of the LF process, a CaS phase was formed on the existing inclusions by a reaction between Ca and S. As the desulfurization of the steel melt progressed, the CaS phase started to be transformed into a CaO phase in the inclusions, which resulted in the formation of CaO-Al2O3-CaS inclusions. After desulfurization of the steel melt, the Al2O3 phase in the inclusions was transformed to the CaO-Al2O3liq phase without being hindered by a CaS phase. During the following RH process, the addition of FeS increased the activity of S, which then reacted with both CaO in the inclusions and with Ca, forming a CaS phase. Consequently, the majority of the inclusions consisted of the Al2O3-CaS phase. Thus, a CaS formation during the LF-RH process without Ca-treatment progresses under the thermodynamic driving forces of the following two reactions: the reaction between CaO in the inclusions and S and the reaction between Ca and S. Due to the formation of a CaS phase during the RH process, inclusions in the high S steel melt were covered by a CaS phase, which is difficult to remove from steel melts. Therefore, the castability of the high S steels can be deteriorated by the CaS inclusions, even without using Ca-treatment. In summary, it can be concluded that the removal of inclusions, generation, and composition evolution should be considered in order to control the inclusion compositions in Al-killed steel melts. In addition, steel components, such as Al and S, are important to monitor to control the inclusion evolution during secondary refining processes.
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| 43. |
- Yoshioka, Takanori, et al.
(författare)
-
The Effect of a High Al Content on the Variation of the Total Oxygen Content in the Steel Melt during a Secondary Refining Process
- 2018
-
Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 89:2
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to clarify the mechanism of low total oxygen (T.O) contents in high-Al containing steel grades. Steel samples are taken from a ladle during an LF-RH process, and the compositions of both the steels and inclusions are determined. According to thermodynamic considerations, the low T.O contents of high Al steel grades are due to the low insoluble oxygen contents. Due to the high Al contents in a steel melt, thermodynamic driving forces of the Al2O3 modification are lower than those in ordinary Al-killed steels. Both the low thermodynamic driving force of the Al2O3 modification and the inclusion removal from the melts contribute to the low CaO contents in inclusions in high-Al steel melts. The contact angles of inclusions in high Al steel melts are higher than 90 degrees due to the low CaO content in inclusions. Therefore, the removal tendency of inclusions in high Al steel melts is kept high throughout an LF-RH process. Due to this high removal tendency, the T.O contents in high Al steel melts decreases remarkably during an LF refining process. Thereafter, they decrease further during the following RH treatment.
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| 44. |
- Yoshioka, Takanori, et al.
(författare)
-
The effect of a sulfur addition on the formation and behavior of cas inclusions during a secondary refining process without using a Ca-treatment
- 2018
-
Ingår i: International Symposium on Materials Processing Fundamentals, 2018. - Cham : Springer International Publishing. - 9783319721309 ; , s. 3-13
-
Konferensbidrag (refereegranskat)abstract
- This study aimed to elucidate the effect of a sulfur addition on the formation and behavior of CaS inclusions in steel melts during a secondary refining process without a Ca-treatment. Samples were taken during production for two different steel grades, namely a low-S steel (S = 0.005%) and a high-S steel (S = 0.055%). Thereafter, the inclusion characteristics were determined using an SEM combined with an EDS. The results show that the CaO content in the inclusions decreased and the CaS content increased after a sulfur addition during an RH process for the high-S steel. Furthermore, CaS-covered inclusions were frequently detected in the high-S steel samples after the S addition. Thermodynamic calculations were also performed to compare the CaS formation behavior in the two steels. The results showed that a CaS phase can thermodynamically be formed in the high-S steel melt even without a Ca-treatment. Also, it was indicated that a CaS phase can be formed in two ways, namely a reaction between Ca and S and a reaction between CaO in inclusions and S. From the viewpoint of interfacial features, inclusions covered by a CaS phase are thought to possess low contact angles to steel melts. Therefore, CaS-covered inclusions tend to remain in a steel melt. According to the results of this study, CaS inclusions can be formed and deteriorate the castability of high-S containing steels even without a Ca-treatment.
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| 45. |
- Ånmark, Niclas, 1987-, et al.
(författare)
-
Effect of different inclusions on mechanical properties and machinability of 20NiCrMo carburizing steels
- 2015
-
Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - Beijing : Chinese Society for Metals. ; , s. 805-808
-
Konferensbidrag (refereegranskat)abstract
- In modern steelmaking, carburizing steels are often used for production of automotive components with elevated levels of toughness and fatigue strength. This study is focused on the link between the characteristics of non-metallic inclusions in the steel and the machinability of the given steel grades. For this purpose, inclusion characteristics (such as composition, number, size, morphology etc.) in steel samples were determined by common two-dimensional (2D) observations of inclusions on polished metal surface of samples as well as by three-dimensional (3D) investigations of inclusions after electrolytic extraction from steel samples. The inclusion characteristics were investigated in the three types of 20NiCrMo carburizing steel grades: Steel A - reference steel (410ppm S) having a common level of mechanical properties and machinability, Steel B - steel grade (having 340ppm S) with an improved machinability due to the Ca-treatment and modification of MnS inclusions and Steel C - clean steel grade (40ppm S) having a small amount of inclusions and a higher fatigue strength. It was found that the number of inclusions in Steel B is smaller than that in Steel A and that the inclusion composition is different. At the same time, the estimated machinability (tool life) of the Ca-treated steel was superior to that of the reference steel. However, the significant decrease of the number of inclusions in the clean steel (Steel C) resulted in a lower machinability in comparison to the reference steel grade.
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| 46. |
- Ånmark, Niclas, 1987-
(författare)
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Inclusion Characteristics and Their Link to Tool wear in Metal Cutting of Clean Steels Suitable for Automotive Applications
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis covers some aspects of hard part turning of carburised steels using a poly‑crystalline cubic boron nitride (PCBN) cutting tool during fine machining. The emphasis is on the influence of the steel cleanliness and the characteristics of non‑metallic inclusions in the workpiece on the active wear mechanisms of the cutting tool. Four carburising steel grades suitable for automotive applications were included, including one that was Ca‑treated.A superior tool life was obtained when turning the Ca-treated steel. The superior machinability is associated with the deposition of lubricating (Mn,Ca)S and (CaO)x-Al2O3-S slag layers, which are formed on the rake face of the cutting tool during machining. Moreover, the transfer of work material to the rake face crater is characteristic in hard part turning of clean steels. It can be because of the lack of sulfides that protect the cutting edge when turning machinability treated steels. This corresponds to the more pronounced crater wear caused by the low‑sulfur steels than that of the steels with higher sulfur contents. It was also concluded that the composition of the non‑metallic inclusions in the Ca‑treated steel is a more important factor than the inclusion number and size, in hard part turning using a PCBN cutting tool. Also, a 3D analysis after electrolytic extraction was found to give a more precise characterisation of non‑metallic inclusions than the conventional 2D analysis by SEM‑EDS. In turn, better correlations to machinability and mechanical properties can be obtained. Hence, the use of this technique is beneficial for future material development.Finally, the challenge for future metallurgy is to manufacture high‑performance steels with improved combined properties of mechanical strength and machinability.
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| 47. |
- Ånmark, Niclas, 1987-
(författare)
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Steel characteristics and their link to chip breaking and tool wear in metal cutting
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The vision of this thesis is to study how it is possible to obtain optimised workpieces during metal cutting processes in industry. Specifically, the work is aimed to increase the understanding between the steel characteristics and their link to the chip breaking and tool wear during metal cutting. The emphasis is on the influence of the cleanliness and the characteristics of non-metallic inclusions in the workpiece on the machinability of carburising steel grades. The machinability of a case hardening steel is improved by a M-treatment (additions of Ca). Also, the improved machinability of the M-steels offers an attractive potential to save money which makes it possible to reduce the tooling costs with up to 50%. The improved machinability of Ca-treated steels is correlated to the formation of lubricating slag layers consisting of Ca-enriched sulfide inclusions and oxy-sulfide inclusions, which are formed on the rake face during the machining operation. It is proposed that the formations of slag layers from the workpiece constituents are essential to minimise the chemical degradation of the tool edge due to a contact with the chip. During this process, sulfur minimises the material transfer from the chip flow, whilst Ca-treated impurities have a stabilising effect on the protective deposits made of slag layers.Since there is a remaining industrial need to increase the production rate, whilst maintaining a high quality of the finished parts, the future production will continue to require extreme demands on the quality of workpieces. If the emphasis is focused on the workpiece, it should be possible to obtain a robust manufacturing process. Therefore, the challenge for future steel metallurgists is to develop high performance grades with optimised combined properties.
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| 48. |
- Ånmark, Niclas, 1987-, et al.
(författare)
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The Effect of Different Non-Metallic Inclusions on the Machinability of Steel
- 2015
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Ingår i: Materials. - Basel, Schweiz : MDPI AG. - 1996-1944. ; 8:2, s. 751-783
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Tidskriftsartikel (refereegranskat)abstract
- Considerable research has been conducted over recent decades on the role of non-metallic inclusions and their link to the machinability of different steels. The present work reviews the mechanisms of steel fractures during different mechanical machining operations and the behavior of various non-metallic inclusions in a cutting zone. More specifically, the effects of composition, size, number and morphology of inclusions on machinability factors (such as cutting tool wear, power consumption, etc.) are discussed and summarized. Finally, some methods for modification of non-metallic inclusions in the liquid steel are considered to obtain a desired balance between mechanical properties and machinability of various steel grades.
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| 49. |
- Ånmark, Niclas, 1987-, et al.
(författare)
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The effect of inclusion composition on tool wear in hard part turning using PCBN cutting tools
- 2015
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 334, s. 13-22
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Tidskriftsartikel (refereegranskat)abstract
- This work reports on hard part turning of carburizing steels using a PCBN cutting tool in fine machining. Emphasis is on the link between composition of the inclusions in work material and wear mechanisms of the cutting tool. A Ca-treated machinability improved 20NiCrMo steel was included together with three other carburizing steels with different inclusion characteristics.Machining tests were conducted to examine cutting tool life and its balance between excessive flank wear or crater wear. The wear mechanisms were examined using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and a secondary electron (SE) detector.The longest tool life was obtained when cutting the Ca-treated steel. The improved machinability is linked to the deposition of complex (Mn,Ca)S and (Ca,Al)(O,S) protective slag layers that form on the rake face of the cutting tool during machining. Cutting in this steel also resulted in a typical ridge formation in the tool edge crater. Transfer of workpiece material to the rake face crater is characteristic in hard part turning of steel with high cleanliness. This is suggested to be related to the lack of the sulphides that lubricate conventional machinability treated steels, and that the crater wear of low-sulphur steel is more pronounced than for steels with higher sulphur content.
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