The Effects of Heating Rate and Cold Work on the Development of Dual-Phase Steel Microstructures

Abstract:

The effects of heating rate and prior cold work on the development of dual-phase steel microstructures in three low carbon steels were evaluated with samples processed on a Gleeble 3500 thermomechanical processing simulator. The nominally 0.2 wt pct carbon steels included a plain carbon steel and modified alloys incorporating higher manganese contents, boron additions, and microalloy additions. Each alloy was prepared with two different cold rolled reductions. Heating rates from 1 to 1000 ^oC/s were selected to span the rates typically experienced in conventional furnace heat treating up to rates for induction heating. Critical transformation temperatures were obtained from dilatometric curves. Dual-Phase microstructures after heat treatment with different heating rates were compared. Transformation temperatures decreased with an increase in cold work and increased with an increase in heating rate. The steels with higher manganese and carbon additions exhibited lower Ac₃ values across all heating rates and the steels with higher silicon higher Ac₁ temperatures across all heating rates. Ac₁ increased less than Ac₃ with increasing heating rate. The increase in transformation temperatures between 100 and 1000 °C/s was smaller than values exhibited over other increments in heating rate, and decreased in one steel; contributing factors were identified for this behavior.

• Periodical: Advanced Materials Research (Volume 922)
• Pages: 755-760
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.922.755
• Online since: May 2014
• Authors: L.S. Thomas*, David K. Matlock, John G. Speer
• Keywords: Austenitization, Dual Phase Steel, Heating Rate, Recrystallization

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