Effects of Rapid Induction Heating on Austenite Development in 0.55 wt pct Carbon Steels

Rapidly induction heated and quenched steels are utilized to achieve high strength for reduced weight applications. A dilatometer was used to rapidly heat four 0.55 wt pct carbon steel alloys at rates of 5, 50, and 500°C/s in order to study transformation to austenite during heating and to martensite during quenching. A pre-treatment was performed first, consisting of holding the samples at either 900°C or 1150°C for 30 minutes and quenching to martensite. The dilation data was used to determine austenite and martensite transformation temperatures. Additional samples were heated and quenched partially through austenite transformation. Metallography was used to illustrate the effects on carbide dissolution and austenite grain size.

From the tests it was found that rapid heating at 500°C/s as compared to 5°C/s increased the temperatures at which cementite precipitates in ferrite, increased the Ac₁ and Ac₃ temperatures, lowered the Ms temperature, and reduced the hardness.