Short-time tempering kinetics of quench hardened pearlitic steels
Paper i proceeding, 2010

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.

Martensitic steel

Laser heat treatment

Tempering kinetics

Hollomon-Jaffe time-temperature parameter

Författare

Johan Ahlström

Chalmers, Material- och tillverkningsteknik, Materialteknologi

Krste Cvetkovski

Chalmers, Material- och tillverkningsteknik, Materialteknologi

Birger Karlsson

Chalmers, Material- och tillverkningsteknik, Materialteknologi

Ingo Siller

Conference proceedings ICTPMCS-2010, 31 May – 2 June 2010, Shanghai, China

6 pp-

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