| 1. |
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| 2. |
- Hedström, Peter, et al.
(författare)
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Elastic strain evolution and ε-martensite formation in individual austenite grains during in situ loading of a metastable stainless steel
- 2008
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Ingår i: Materials letters (General ed.). - : Elsevier BV. - 0167-577X .- 1873-4979. ; 62:2, s. 338-340
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Tidskriftsartikel (refereegranskat)abstract
- The (hcp) ε-martensite formation and the elastic strain evolution of individual (fcc) austenite grains in metastable austenitic stainless steel AISI 301 has been investigated during in situ tensile loading up to 5% applied strain. The experiment was conducted using high-energy X-rays and the 3DXRD technique, enabling studies of individual grains embedded in the bulk of the steel. Out of the 47 probed austenite grains, one could be coupled with the formation of ε-martensite, using the reported orientation relationship between the two phases. The formation of ε-martensite occurred in the austenite grain with the highest Schmid factor for the active {111}b12¯1N slip system.
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| 3. |
- Hedström, Peter, et al.
(författare)
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Evolution of residual strains in metastable austenitic stainless steels and the accompanying strain induced martensitic transformation
- 2006
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Ingår i: Residual Stresses VII. - Uetikon-Zuerich : Trans Tech Publications Inc.. - 0878494146 ; 524-525, s. 818-826
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Konferensbidrag (refereegranskat)abstract
- The deformation behavior of metastable austenitic stainless steel AISI 301, suffering different initial cold rolling reduction, has been investigated during uniaxial tensile loading. In situ highenergy x-ray diffraction was employed to characterize the residual strain evolution and the strain induced martensitic transformation. Moreover, the 3DXRD technique was employed to characterize the deformation behavior of individual austenite grains during elastic and early plastic deformation. The cold rolling reduction was found to induce compressive residual strains in the austenite along rolling direction and balancing tensile residual strains in the -martensite. The opposite residual strain state was found in the transverse direction. The residual strain states of five individual austenite grains in the bulk of a sample suffering 2% cold rolling reduction was found to be divergent. The difference among the grains, considering both the residual strains and the evolution of these, could not be solely explained by elastic and plastic anisotropy. The strain states of the five austenite grains are also a consequence of the local neighborhood. Introduction The metastable austenitic stainless steels partially transform from the soft and ductile austenite to the hard and brittle martensite during deformation. This deformation induced martensitic transformation provides a compos...
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| 4. |
- Hedström, Peter, et al.
(författare)
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Stepwise transformation behavior of the strain-induced martensitic transformation in a metastable stainless steel
- 2007
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Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 56:3, s. 213-216
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Tidskriftsartikel (refereegranskat)abstract
- In situ high-energy X-ray diffraction during tensile loading has been used to investigate the evolution of lattice strains and the accompanying strain-induced martensitic transformation in cold-rolled sheets of a metastable stainless steel. At high applied strains the transformation to α-martensite occurs in stepwise bursts. These stepwise transformation events are correlated with stepwise increased lattice strains and peak broadening in the austenite phase. The stepwise transformation arises from growth of α-martensite embryos by autocatalytic transformation.
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| 5. |
- Knutsson, Axel, et al.
(författare)
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Reverse martensitic transformation and resulting microstructure in a cold rolled metastable austenitic stainless steel
- 2008
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 79:6, s. 433-439
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Tidskriftsartikel (refereegranskat)abstract
- The reverse martensitic transformation in cold-rolled metastable austenitic stainless steel has been investigated via heat treatments performed for various temperatures and times. The microstructural evolution was evaluated by differential scanning calorimetry, X-ray diffraction and microscopy. Upon heat treatment, both diffusionless and diffusion-controlled mechanisms determine the final microstructure. The diffusion reversion from α′-martensite to austenite was found to be activated at about 450°C and the shear reversion is activated at higher temperatures with Af′ ∼600°C. The resulting microstructure for isothermal heat treatment at 650°C was austenitic, which inherits the α′-martensite lath morphology and is highly faulted. For isothermal heat treatments at temperatures above 700°C the faulted austenite was able to recrystallize and new austenite grains with a low defect density were formed. In addition, carbo-nitride precipitation was observed for samples heat treated at these temperatures, which leads to an increasing Ms-temperature and new α′-martensite formation upon cooling.
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| 6. |
- Terner, Mark, et al.
(författare)
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Residual stress evolution during decomposition of Ti(1-x)Al (x)N coatings using high-energy x-rays
- 2006
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Ingår i: RESIDUAL STRESSES VII. - : Transtec Publications; 1999. ; 524-525, s. 619-624, s. 619-624
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Konferensbidrag (refereegranskat)abstract
- Residual stresses and microstructural changes during phase separation in Ti33Al67N coatings were examined using microfocused high energy x-rays from a synchrotron source. The transmission geometry allowed simultaneous acquisition of x-ray diffraction data over 360 degrees and revealed that the decomposition at elevated temperatures occurred anisotropically, initiating preferentially along the film plane. The as-deposited compressive residual stress in the film plane first relaxed with annealing, before dramatically increasing concurrently with the initial stage of phase separation where metastable, nm-scale c-AlN platelets precipitated along the film direction. These findings were further supported from SAXS analyses.
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| 7. |
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| 8. |
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| 9. |
- Hedayati, Ali, 1984-, et al.
(författare)
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Effect of Cold Work Percent on Mechanical Properties of AISI 304L Stainless Steel
- 2009
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Konferensbidrag (refereegranskat)abstract
- This article investigates the effect of various degrees of plastic deformation introduced by cold rolling at zero temperature on the mechanical properties of AISI 304L stainless steel. microstructural and ferromagnetic studies were also conducted. The material was evaluated up to 90% reduction in thickness. For this purpose, magnetic measurements, optical metallography, hardness and Tensile test, were used. Results show that by increasing the amount of rolling strain, transformation of austenite to martensite generally increases. The regime of this increase depends on the amount of the plastic deformation and temperature. The tensile strength and hardness were found to increase with the increase of cold rolling percentage (%CR) up to 90%.The results indicate that the formation of strain-induced martensite evidently led to a significant strengthening of the steel.
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| 10. |
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| 11. |
- da Silva, Melina, 1978, et al.
(författare)
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A comparison of thermal stability in nanocrystalline Ni- and Co-based materials
- 2005
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Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 96:09, s. 1009-1014
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Tidskriftsartikel (refereegranskat)abstract
- In this paper the microstructural development upon annealing of nanocrystalline Ni- and Co-based electrodeposits is described. New investigations on Ni, Ni - Fe, and Co-P are compared with previous results on Ni, Co, and Ni -P in terms of microstructural changes and stabilizing mechanisms. The conclusions are: pure nanocrystalline Ni and Co are stabilized by impurities in the grain boundaries. In the case of Co, also an allotropic phase transformation influences the occurrence of abnormal grain growth. Alloying and/or adding solutes is found to increase thermal stability. While in Ni-20 at.% Fe the ordering transformation is expected to be the reason for stabilization, in strongly segregating systems (Ni -P and Co-P) the stabilizing effect is the decrease in grain boundary energy due to solute segregation. After precipitation, Zener pinning still hinders grain boundary migration, but not sufficient to stabilize the nanocrystalline structure.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Borck, Øyvind, 1971, et al.
(författare)
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Adsorption of Methanol on Aluminum Oxide: A Density Functional Study
- 2003
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Ingår i: ATB-Metallurgie. - 0365-7302. ; 43, s. 342-
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Konferensbidrag (refereegranskat)abstract
- Theoretical calculations based on density functional theory have made significant contributions to our understanding of metal oxides, their surfaces, and the binding of molecules at these surfaces. In this paper we investigate the binding of methanol at the alpha-Al2O3(0001) surface using first-principles density functional theory. We calculate the molecular adsorption energy of methanol to be E^g_ads=1.03 eV/molecule. Taking the methanol-methanol interaction into account, we obtain the adsorption energy E_ads=1.01 eV/molecule. Our calculations indicate that methanol adsorbs chemically by donating electron charge from the methanol oxygen to the surface aluminum. We find that the surface atomic structure changes upon adsorption, most notably the spacing between the outermost Al and O layers changes from 0.11 Angstrom to 0.33 Angstrom.
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| 17. |
- Andersson, Joel, 1981-, et al.
(författare)
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Hot Cracking of Allvac 718Plus, Alloy 718 and Waspaloy at Varestraint Testing
- 2008
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Ingår i: 4th International Symposium on Aerospace Materials and Manufacturing Processes. - Montreal : Canadian Institute of Mining, Metallurgy and Petroleum. - 9781617386169 ; , s. 401-413, s. 401-413
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Konferensbidrag (refereegranskat)abstract
- Varestraint testing together with DSC and SEM-EDX analyses have been performed as means of investigating the hot cracking susceptibility of Allvac 718Plus, alloy 718 and Waspaloy. The solidification sequences in Allvac 718Plus and alloy 718 were very similar to each other starting by an initial solidification of the gamma phase, gamma/MC reaction at around 1260°C and then finally ending the sequence by gamma/Laves eutectic reaction at around 1150°C. Waspaloy had the same solidification sequence, except no Laves phase formation takes place, and solidification started at a somewhat higher temperature as compared to alloy 718 and the solidification sequence ends by a gamma/MC reaction at around 1245°C. The total amount of hot cracking in Waspaloy was shown to be much less than that in alloy 718 and in Allvac 718Plus which is believed to be related to the presence of the Laves eutectic in the latter two alloys with corresponding larger solidification ranges. Hot cracking of 718Plus is slightly less than in 718.
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| 18. |
- Choquet, Isabelle, 1965-, et al.
(författare)
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Clogging and lump formation during atmospheric plasma spraying with powder injection downstream the plasma gun
- 2007
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 16:4, s. 512-523
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to numerically and experimentally investigate lump formation during atmospheric plasma spraying with powder injection downstream the plasma gun exit. A first set of investigations was focused on the location and orientation of the powder port injector. It turned out impossible to keep the coating quality while avoiding lumps by simply moving the powder injector. A new geometry of the powder port ring holder was designed and optimized to prevent nozzle clogging, and lump formation using a gas screen. This solution was successfully tested for applications with Ni-5wt.%Al and ZrO2-7wt.%Y2O3 powders used in production. The possible secondary effect of plasma jet shrouding by the gas screen, and its consequence on powder particles prior to impact was also studied.
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| 19. |
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| 20. |
- Nordström, Michael, et al.
(författare)
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An appearance-based measure of surface defects
- 2009
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Ingår i: International Journal of Material Forming. - : Springer Science and Business Media LLC. - 1960-6206 .- 1960-6214. ; 2:2, s. 83-91
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Tidskriftsartikel (refereegranskat)
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| 21. |
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| 22. |
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| 23. |
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| 24. |
- Larsson, Mikael, et al.
(författare)
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Improved energy and material efficiency using new tools for global optimisation of residue material flows
- 2006
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 3:2, s. 127-137
-
Tidskriftsartikel (refereegranskat)abstract
- Residue materials generated in the metallurgical industry have gained an increasing importance, both from the points of view of energy and material supply. A joint process integration model for the integrated steel plant system is developed and used in this paper. It takes into account both residue materials and energy recirculation for the system. The potential for increased recirculation and the effect on the system from an environmental point of view is presented, and implementations and practical experiences are discussed. The model developed can serve as a benchmark for different steelmaking operations and constitute a basis for the continuous work involved in material, energy, environment or economic analyses for the steel production system.
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| 25. |
- Anderberg, Staffan, 1981-, et al.
(författare)
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A survey of metal working companies’ readiness for process planning performance measurements
- 2009
-
Ingår i: IEEE International Conference on Industrial Engineering and Engineering Management, IEEM 8-11 sep, 2009, Hong-Kong. - 9781424448708 ; , s. 1910-1914
-
Konferensbidrag (refereegranskat)abstract
- The paper presents an investigation regarding the potential and the readiness for implementing performance indicators and performance measurement systems of the process planning work for metal working companies. The paper is based on a questionnaire survey distributed to process planners in the Swedish metal working industry. The main outcome of the investigation is a foundation for understanding the implementation of performance measures of the process planning work for CNC machining. The survey revealed a few strengths and short comings in the studied companies.
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| 26. |
- Dugic, Izudin, 1962-, et al.
(författare)
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The Influence of Inoculation on the Metal Expansion Penetration With Respect to the Primary and Eutectic Solidification
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The mechanism of metal expansion penetration of grey cast iron components is dependent on both solidification anomalies at the metal – mould interface and the inclination of the sand mould to permit the metal liquid to penetrate between the sand grains. The present work utilizes the latest development of primary austenite inoculation in combination with classic eutectic inoculation to limit the metallurgical contribution to metal expansion penetration. A solid shell containing the primary austenite dendrite network constitutes the barrier between the liquid metal and mould interface. Inoculants of both the primaryand eutectic phase control the permeability of the dendrite network.
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| 27. |
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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
- Ericsson, Mikael, 1975-, et al.
(författare)
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Three-dimensional simulation of robot path and heat transfer of a TIG-welded part with complex geometry
- 2002
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Ingår i: 11th International Conferences on Computer Technology in Welding. - : Society of Manufacturing Engineers, North American Manufacturing Research Institution. ; , s. 309-316
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The application of commercial software (OLP) packages for robot simulation, and programming, use interactive computer graphics, provide powerful tools for creating welding paths off-line. By the use of such software, problems of robot reach, accessibility, collision and timing can be eliminated during the planning stage. This paper describes how such software can be integrated with a numerical model that predicts temperature-time histories in the solid material. The objective of this integration is to develop a tool for the engineer where robot trajectories and process parameters can be optimized on parts with complex geometry. Such a tool would decrease the number of weld trials, increase productivity and reduce costs. Assumptions and principles behind the modeling techniques are presented together with experimental evaluation of the correlation between modeled and measured temperatures.
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| 34. |
- Fredriksson, Hasse, 1939-, et al.
(författare)
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Thoughts about the Initial Solidification Process during Continuous Casting of Steel
- 2002
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Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 31, s. 292-297
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The initial solidification during continuous casting is very important for the surface quality of the strand. Oscillation marks are formed by the movement of the mould. One mainly distinguishes between two different types of marks, namely folding marks and overflow marks. The formation of these can be described by the heat flow and the surface tension balance. A theoretical analysis outlining the most important parameters controlling the formation of these marks is presented. A metallographic analysis of the formation was also performed. The theory and observations have been used to analyse the effect of casting speed and oscillation frequency on the formation of different types of marks. It is shown that a meniscus is formed at the top of the growing shell. The maximum height of the meniscus determines the ideal distance between the marks. The mould frequency is related to this height. A frequency that is far from ideal causes overflow marks and folding marks with macrosegregation and cracks. The distance between the marks is, in such cases, not constant. The depth of the marks is calculated from the heat flow and the surface tension balance.
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| 35. |
- Heralic, Almir, 1981-, et al.
(författare)
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Control Design for Automation of Robotized Laser Metal-Wire Deposition
- 2008
-
Ingår i: Proceedings of the 17th IFAC World Congress. - : International Federation of Automatic Control. ; , s. 14785-14791
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper a novel approach towards automation of robotized laser metal-wire deposition (RLMwD) is described. The RLMwD technique is being developed at University West in cooperation with Swedish industry for solid freeform fabrication of fully dense metal structures. The process utilizes robotized fibre laser welding and metal wire filler material, together with a layered manufacturing method, to create metal structures directly from a CAD drawing. The RLMwD process can also be used for repair or modification of existing components. This paper faces the challenge of designing a control system for maintaining stable process variables, such as a constant layer height and a stable component temperature, during the entire manufacturing process. Several problems are identified and discussed in the paper, e.g. the difficulty of obtaining the bead height in the weld pool environment. The case study is a repair application for stamping tools, where worn out trim edges are to be repaired. Issues regarding the control design, system identification, and the practical implementation of this application are discussed.
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| 36. |
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| 37. |
- Jaradeh, Majed, et al.
(författare)
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Method Developed for Quantitative Assessment of Inclusions in Aluminium Billets
- 2007
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Ingår i: LIGHT METALS 2007. - : Minerals, Metals & Materials Society. - 9780873396592 ; , s. 679-684
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Konferensbidrag (refereegranskat)abstract
- A technique, based on sodium hydroxide hot macro etching, has been developed to deep etch non-metallic inclusions in a way that makes them visible on a macro scale. The distribution of inclusions in transverse sections along DC-cast aluminium billets could thus be studied. The technique has obvious advantages over other common analysis methods in giving a macroscopic spatial distribution of inclusions in a relatively simple way. The paper describes the development of the new technique and some applications. An analysis was made of how different inclusions behave during prolonged strong etching. Light optical microscopy, TEM and SEM/EDX have been used to identify specific inclusions.
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| 38. |
- Jaradeh, Majed, et al.
(författare)
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Solidification Studies of Automotive Heat Exchanger Materials
- 2006
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Ingår i: JOM. - : Springer Science and Business Media LLC. - 1047-4838 .- 1543-1851. ; 58:11, s. 56-61
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Tidskriftsartikel (refereegranskat)abstract
- Modifications of the aluminum alloy AA 3003 have been studied to improve and tailor its properties for applications in automotive heat exchangers. Laboratory techniques have been applied to simulate industrial direct-chill casting, and some basic solidification studies have been conducted. The results are coupled to structures observed in industrial-size ingots and discussed in terms of structure-property relations.
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| 39. |
- Jiang, Janna, 1978-, et al.
(författare)
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Microindentation and Inverse Analysis to Characterize Elastic-Plastic Properties for Thermal Sprayed Ti2AlC and NiCoCrAlY
- 2009
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Ingår i: Journal of thermal spray technology (Print). - : Springer. - 1059-9630 .- 1544-1016. ; 18:2, s. 194-200
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Tidskriftsartikel (refereegranskat)abstract
- Elastic-plastic material properties for HVOF sprayed Ti2AlC (sprayed with Maxthal 211 powder) and plasma sprayed NiCoCrAlY coatings were investigated using modeling and experimental Berkovich microindentation. Optical microstructure evaluations were also performed. The theories of Hertz, Oliver and Pharr were combined with finite element analysis for extracting the material properties. Empirically based material models for both thermal sprayed Ti2AlC and NiCoCrAlY coatings are proposed.
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| 40. |
- Jönsson, Pär, et al.
(författare)
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Focus on clean steel within Jernkontoret's Research - an overview
- 2008
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Ingår i: Revue de métallurgie (Imprimé). - : EDP Sciences. - 0035-1563 .- 1156-3141. ; 105:6, s. 317-326, s. 317-326+III
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Tidskriftsartikel (refereegranskat)abstract
- Some highlights from the Jernkontoret Research with focus on the modeling work of the lost decade are presented. First the concept of a fundamental mathematical model is discussed. Thereafter, a short review of growth and separation models based on fundamental modeling of ladles is presented. Then, recent modeling efforts within Jernkontoret's Research are highlighted.
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| 41. |
- Karasev, Andrey V., et al.
(författare)
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Nitride Precipitation on Particles in Fe-10 mass % Ni Alloy Deoxidized with Ti, M (M=Mg, Zr and Ce) and Ti/M
- 2009
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 49:2, s. 229-238
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Tidskriftsartikel (refereegranskat)abstract
- The precipitation of nitrides on deoxidation particles in an Fe-10mass%Ni alloy containing 30 similar to 130 ppm O and 14 similar to 22 ppm N has been studied in the experiments where an alloy was deoxidized with Ti, M (M=Mg, Zr and Ce) and Ti/M at 1600 degrees C and then cooled to 1200 degrees C, followed by holding for 0 and 60 min before quenching. The total number of particles above 0.1 mu m remains almost constant except in Ti deoxidation, but the proportion of cubic particles which correspond to nitrides and oxide-nitrides increases during holding at 1200 degrees C in Ti, Zr, Ti/Mg and Ti/Zr deoxidations. In 0.05% (initial amount) Ti deoxidation, the number of TiN and TiN+TiOx particles increases during holding. In 0.03%Ti/0.1%Mg deoxidation, the number of TiOx-TiN particles decreases and the number of MgO-TiN and MgO-Ti(O, N) particles increases during holding due to the reduction of TiOx with soluble Mg. In 0.03%Ti/0.04%Zr deoxidation, the number of ZrO2 particles significantly decreases during holding due to the precipitation of TiN and ZrN on Zr oxides and formation of Zr(O, N)-Ti(O, N) particles. In the cases of Ti/0.08%Zr and Ti/0.12%Ce deoxidations, most of particles at 0 and 60 min of holding are ZrO2 and Zr(O, N) and Ce2O3 oxides, respectively, because the FeO-TiOx oxide in particles is reduced completely by dissolved Zr and Ce.
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| 42. |
- Källgren, Therese, et al.
(författare)
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Microstructure and temperature development in copper welded by the FSW-process
- 2003
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Ingår i: 4th International Symposium on FSW, Park City, USA, April, 2003.
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Konferensbidrag (refereegranskat)abstract
- The use of Copper canisters with cast iron inserts is one of the proposed methods for long time deposition of nuclear fuel waste. The joining of the lid and possibly the base of the canister can be performed with Friction Stir Welding (FSW). A thorough understanding of the microstructure development in these welds is of major importance, since defects must be avoided. The microstructure and hardness profiles were investigated for two FSW conditions, at the beginning of the weld when there are essentially cold conditions, and when the steady state is reached. In cold welds the features of the nugget are very similar to that observed when FSW-joining aluminium. However, when the welding conditions reach the steady state, the nugget gets wider and the hardness is lower than in the cold weld. Electron Back Scatter Diffraction (EBSD) visualisation has been used to determine the grain size distribution of, twins and misorientation within grains. The orientation maps show a fine uniform equiaxed grain structure. There is no major misorientation within the grains in the nugget or at the root, but 25 mm from the weld centre the misorientation is large. This confirms that this area lies within the Thermal Mechanical Affected Zone (TMAZ) and is partially recrystallised. The root has many more annealing twins than the nugget. This indicates that the nugget has experienced deformation after recrystallisation. A model has been used to correlate heat flow to the grain size and the hardness distributions.
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| 43. |
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| 44. |
- Markocsan, Nicolaie, 1967-, et al.
(författare)
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Thermal spraying in Europe’s Nordic region
- 2007
-
Ingår i: Journal of thermal spray technology (Print). - : Springer. - 1059-9630 .- 1544-1016. ; 16:4, s. 463-464
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Tidskriftsartikel (refereegranskat)
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| 45. |
- Storck, Joakim, et al.
(författare)
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Assessment of Best Scheduling Practice in Continuous Casting and Hot Rolling of Stainless Steel Strip by System Dynamics Simulation
- 2007
-
Ingår i: Sheet Metal 2007. - : Trans Tech Publications Inc.. - 9780878494378 ; 344, s. 897-904
-
Konferensbidrag (refereegranskat)abstract
- A rapid flow of materials with little intermediate buffering between steel mill and hot strip mill has many benefits. One is energy savings due to raised charging temperature in the reheat furnaces of the hot strip mill. Another is that tied capital is freed up, thereby improving mill economy. Still, it is not unusual that average lead-time is in the order of days, or even weeks.The aim of the present work was to show how lead-times from casting to rolling could be improved by changes in the scheduling function. A System Dynamics model of a stainless steel strip production facility with continuous caster and hot rolling mill was created. The model was used to study the dynamics of the system in response to changes in parameters that defined the scheduling configuration.More frequent schedule updating generally resulted in less work in process (WIP) and shorter lead times from casting to rolling, with resulting higher charging temperatures. The amount of oscillation in the system was also reduced. More frequent work roll changes were required when scheduling frequency increased, resulting in an increased fraction of setup time in relation to total processing time. Therefore, a development towards increased scheduling frequency may have to be complemented by efforts to reduce changeover times.The conclusion was that dynamic scheduling routines with frequent schedule updating result in better overall performance of the system due to lower WIP and better heat utilization. Dynamic scheduling routines with frequent updates make the system respond better to changes in the system and give better overall performance. The result is lower WIP, increased energy efficiency and less oscillation in the system.
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| 46. |
- Thunman, Mikael, et al.
(författare)
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Study on the formation of open-eye and slag entrainment in gas stirred ladle
- 2007
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 78:12, s. 849-856
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory experiments were carried out to study the phenomena related to open-eye formation in ladle treatment. Ga-In-Sn alloy with a melting temperature of 283 K was used to simulate the liquid steel, while MgCl2-Glycerol(87%) solution as well as HCl solution were used to simulate the ladle slag. No open-eye was formed at lower gas flow rates, but, occurred when gas flow reached a critical rate. This critical gas flow rate was found to depend significantly on the height of the top liquid. No noticeable amount of top liquid was observed in any of the samples taken from the metal bulk during gas stirring. To confirm this aspect, samples of slag-metal interface were taken around the open-eye in an industrial gas stirred steel ladle. No entrapped slag droplet was found in the solidified steel within the region between the interface and 2 cm from the interface. The accordance of the laboratory and industrial results suggests that the entrainment of slag into the steel bulk around the open-eye cannot be considered as the major contribution to inclusion formation.
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| 47. |
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| 48. |
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| 49. |
- Wiklund, Daniel, 1970-
(författare)
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Tribology of stamping : the influence of designed steel sheet surface topography on friction
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tribology is the science of friction, wear, and lubrication; the interaction of surfaces in relative motion. The tribological conditions in sheet metal forming influences the flow of material in forming operations, the strain distributions of sheet material, extent of wear, and thereby the quality of products. The purpose of the thesis is to increase the knowledge of why and how sheet surface topography influence the frictional response in stamping, to characterise the geometrical properties, and make results applicable for industry. The frictional response of different surface topographies have been measured in a Bending Under Tension test under mixed lubricated conditions. The studied materials have been stainless steel sheets and uncoated and coated carbon steel sheets. The results did show the influence of roughness, skewness, and anisotropy of surface topography. The findings could be explained by the theory of pad bearings. A new functional 3D parameter (Sq>0) was developed for pressing performance that is sensitive to the effects of roughness and skewness. The texture-aspect ratio parameter (Str) was found to be correlated to the anisotropical behaviour of the frictional response. The results are very tangible and mean increased control of stamping operations. An initial step was taken to introduce more advanced tribological models in FE simulation of sheet metal forming operations. The aim is to decrease the trial-and-error time in the design process of dies and tools. A friction model considering surface topography (Sq>0), sliding velocity, lubricant viscosity, and apparent pressure, was successfully implemented. Simulations of a part were evaluated with real stamping tryouts. The results did show the potential of improving the precision in forming simulations with more advanced tribological models. Finally, theory and characterisation methods of active micro-oil pockets in the contact zone of tool and sheet were investigated. The real contact area was shown to be the critical feature to determine. Therefore, two topographical methods and one microscope-imaging processing technique were studied, but no method was found to be viable. However, the experimental results did not confirm the importance of microoil pockets in mixed lubricated regime.
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- Dugic, Izudin, 1962-
(författare)
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Metal Expansion Penetration on Concave Casting Surfaces of Cylinder Heads Cast in Grey Cast Iron
- 2009
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Konferensbidrag (refereegranskat)abstract
- Cylinder heads have an extremely complex shape with large areas of concave casting surfaces. The concave casting surfaces are often associated with metal expansion penetration problems or other surface defects, e. g. surface shrinkage. The defects cause high production costs due to component rejection and increased fettling time. This report presents an investigation of the microstructure in grey cast iron close to the sand-metal interface affected by metal penetration in a complex shaped casting. The dominant penetration defect observed in the cylinder heads was expansion penetration. Even pre-solidification penetration and sand crack defects were observed. The microstructure found in the non penetrated areas is typical for solidification of grey iron cast in sand moulds.
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