| 1. |
- Ahlström, Johan, 1969, et al.
(författare)
-
Short-time tempering kinetics of quench hardened pearlitic steels
- 2010
-
Ingår i: Conference proceedings ICTPMCS-2010, 31 May – 2 June 2010, Shanghai, China. ; , s. 6 pp-
-
Konferensbidrag (refereegranskat)abstract
- In many industrial processes such as welding, and operating environments like railway wheel/rail contact, certain material volumes are exposed to very short temperature pulses that endure for times of the order of 1 s or shorter. When pearlitic steel is exposed to temperatures above the effective austenitisation temperature, martensite forms upon rapid cooling. In the current work tempering of a martensitic carbon steel was performed, with a laser heat source to create short time top-hat temperature pulses, and also with conventional salt bath experiments for longer tempering times. Temperatures were varied in the range of 500 to 700°C, and times between 0.05 to 3000 s. It was found that the martensitic test samples showed a very rapid initial softening upon tempering. During the first 0.1 second the hardness decrease was measured to 35-55% in the tested temperature range. Thereafter the additional hardness decrease was limited to ~10-15% of the original hardness, even after 30 min of tempering. Thus the use of time-temperature models for predicting tempering properties, that relies on constant or linear dependence of the activation energy cannot be extrapolated to very short time processes.
|
|
| 2. |
- Lindwall, Greta, 1981-, et al.
(författare)
-
Coarsening investigations of precipitates in PM tool steel grades - an effect of nitrogen
- 2012
-
Ingår i: Berg- und Huttenmännische Monatshefte (BHM). - : Springer Science and Business Media LLC. - 0005-8912 .- 1613-7531. ; 157:11, s. 406-413
-
Tidskriftsartikel (refereegranskat)abstract
- We present experimental and theoretical comparisons of the coarsening rate for the MX(X=C, N or C+N) precipitate in five different tool steel grades produced by PowderMetallurgy (PM). The alloys contain different amounts of nitrogen and carbon; ranging fromhigh carbon/low nitrogen to high nitrogen/low carbon. Common for the grades is a highamount of precipitate forming alloying elements resulting in a high fraction of hard phase.Experimentally we have found out that the nitrogen rich precipitates coarsen slower, both forhigher and lower carbon content, than the carbon rich precipitates. Coarsening simulations areperformed utilizing the DICTRA software and an agreement between calculations andmeasurements can be concluded.
|
|
| 3. |
- Lindwall, Greta, 1981-, et al.
(författare)
-
Diffusion calculations as a tool for tool steel design
- 2009
-
Ingår i: Proceedings of the 8th International Tooling Conference, RWTH Aachen, Aachen, Germany. ; , s. 1063-1070
-
Konferensbidrag (refereegranskat)abstract
- Thermodynamic calculations have shown to be a powerful tool for predications of phasecompositions and phase fractions in steels. Coupling of thermodynamic and diffusion mobilitydatabases make diffusion calculations possible, and along with the accessibility of accurate anduser-friendly software on the market, the quality demands on kinetic data have increased.This work concerns development of multicomponent diffusion data for calculations applied todiffusion dependent processes, and focus is on alloy systems alloyed with Co. The possibility toevaluate diffusion data with the help of coarsening experiments and diffusion couples isinvestigated.
|
|
