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Short-time tempering kinetics of quench hardened pearlitic steels

Johan Ahlström (Institutionen för material- och tillverkningsteknik, Materialteknologi) ; Krste Cvetkovski (Institutionen för material- och tillverkningsteknik, Materialteknologi) ; Birger Karlsson (Institutionen för material- och tillverkningsteknik, Materialteknologi) ; Ingo Siller
Conference proceedings ICTPMCS-2010, 31 May – 2 June 2010, Shanghai, China p. 6 pp. (2010)
[Konferensbidrag, refereegranskat]

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.

Nyckelord: Tempering kinetics, Laser heat treatment, Martensitic steel, Hollomon-Jaffe time-temperature parameter


Conference proceedings only published on conference CD.



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Denna post skapades 2010-11-10. Senast ändrad 2014-09-02.
CPL Pubid: 128835