| 1. |
- Farooq, Muhammad, et al.
(författare)
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Influence of long time ageing on ductility and toughness in the stainless steel 310 in the presence of banded microstructure
- 2012
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Ingår i: La Metallurgia Italiana. - 0026-0843. ; 104:11-12, s. 33-38
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Tidskriftsartikel (refereegranskat)abstract
- During service at elevated temperatures extensive formation of particles can take place that can have a dramatic influence on mechanical properties. Precipitation of sigma-phase and M23C6-carbides have been studied both experimentally and with thermodynamic modelling for 25Cr20Ni austenitic stainless steels (AISI 310) at 800 degrees C for up to 5000 h. Previous work has demonstrated that the modelling could describe the nucleation and growth satisfactory. After long term ageing the particles form bands in the microstructure. In the present paper the influence of these bands on ductility and toughness at room temperature is analysed. For this purpose previously developed models for ductility and toughness are utilised. Model values for banded and non-banded microstructures have been generated for casts of 310 in fine and coarse grained conditions with 0.04 and 0.12%N The model values show that in the coarse grained condition, no reduction in ductility and toughness can be expected in the banded microstructure. In the fine grained condition a modest reduction is predicted.
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| 2. |
- Luks, T., et al.
(författare)
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Contact stress distribution and roll surface temperatures in the roll gap analyzed with different sensors
- 2014
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Ingår i: La Metallurgia Italiana. - : Associazione Italiana di Metallurgia. - 0026-0843. ; 106:1, s. 19-25
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the contact stresses and temperatures during hot and cold rolling have been measured. A work roll containing three different sensors was used for the measurements. There were two contact devices for directly measuring forces and one temperature sensor. One sensor was the "ROLLSURF" sensor. Results obtained with this sensor have been presented earlier [1-3], The measurement principle is based on deformation measurements with strain gauges which were placed on an internal cradle-type roll insert. The second sensor was a friction pin sensor. The forces on the top of the pin were measured by three axis piezoelectric-transducers. The pin sensor was mounted inside the work roll opposite to the ROLLSURF sensor. The third sensor was a thermocouple placed next to the pin sensor. The temperatures were measured very close to the roll surface. The surface boundary conditions including the heat flux and surface temperatures were computed using inverse modelling calculations developed at Brno University of Technology. The main task of this paper is to show a comparison of the contact forces and contact length measured with the strain-gauge sensor and the pin-sensor.
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| 3. |
- Sjögren, B., et al.
(författare)
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Test of electromagnetic, non-destructive method for determining material properties in steel
- 2014
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Ingår i: La Metallurgia Italiana. - : Associazione Italiana di Metallurgia. - 0026-0843. ; 106:10, s. 23-27
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Tidskriftsartikel (refereegranskat)abstract
- This study, in the area of non-destructive testing and measuring technology, shows that it is possible to inspect and determine the mechanical properties and micro structure of a material using electro-magnetic technique. The goal has been to on-line determine material properties like residual stress distributions, variations in tensile strength and fatigue strength in a material. In the project the latest in materials inspection using electro-magnetic methods combined with statistic modelling is used. The project has shown that these new methods can non-destructively determine the mechanical properties of a material or a machine detail. It is believed that this measuring technique has a clear place in industry.
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| 4. |
- Sjölander, Emma, 1981-, et al.
(författare)
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The influence of natural ageing on the artificial ageing response of Al-Si-Cu-Mg casting alloys
- 2012
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Ingår i: La Metallurgia Italiana. - Milano : Associazione Italiana di Metallurgia. - 0026-0843. ; 11-12, s. 39-43
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Tidskriftsartikel (refereegranskat)abstract
- The T6 heat treatment is commonly used to increase the strength of gravity cast Al-Si components containing Cu and/or Mg. The artificial ageing response is known to be affected by the thermal history, such as solution treatment, quench rate, natural ageing and heating rate to the artificial ageing temperature. The influence of natural ageing on the artificial ageing response was investigated for three alloys; Al-8Si-0.4Mg, Al-7Si-3Cu and Al-8Si-3Cu-0.4Mg. Natural ageing had a strong influence on the ageing response of the Al-Si-Mg alloy in the underaged condition and the strength increase was strongly reduced. Despite this, the time to peak yield strength as well as its magnitude were not strongly affected by natural ageing. No clear influence of natural ageing was observed for the Al-Si-Cu alloy. For the Al-Si-Cu-Mg alloy the ageing response seems to depend on the natural ageing time. Natural ageing of 3 weeks shifted the peak yield strength to shorter ageing times and its magnitude was decreased a little compared to direct ageing after quench. Natural ageing of 1 day gave the least beneficial properties after artificial ageing.
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| 5. |
- Vitos, Levente, et al.
(författare)
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Stainless Steel Alloys from First-principles Theory
- 2012
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Ingår i: La Metallurgia Italiana. - 0026-0843. ; :5, s. 19-27
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Tidskriftsartikel (refereegranskat)abstract
- Gaining an accurate description of materials obviously requires the most advanced atomic-scale techniques from both experimental and theoretical areas. In spite of the vast number of available techniques, however; the experimental study of the atomic-scale properties and phenomena even in simple solids is rather difficult. In steels the challenges become more complex due to the interplay between the structural, chemical and magnetic effects. On the other hand, advanced computational methods based on density functional theory ensure a proper platform for studying the fundamental properties of steel materials from first-principles. Our group at the Royal Institute of Technology in Stockholm has an international position in developing and applying computational codes for such applications. Using our ab initio tools, we have presented an insight to the electronic and magnetic structure, and micromechanical properties of austenitic stainless steel alloys. In the present contribution, we review the most important developments within the ab initio quantum-mechanics-aided steel design with special emphasis on the role of magnetism on the fundamental properties of alloy steels.
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