Effect of Tempering Temperature on Microstructure, Texture and Mechanical Properties of a High Strength Steel

2. Experimental

The chemical composition of the steel is given in Table 1. The steel was industrially hot rolled to a thickness of 25 mm. Samples were again hot rolled at a temperature of 1100°C to 5 mm from the initial thickness in a laboratory rolling mill. The specimen was deformed 10% in each pass and rolling direction was kept strictly unidirectional. After each pass, the sample was kept back into the furnace to re-attain the rolling temperature.

Samples of 150 x 150 mm cross section were cut and subjected to heat-treatment for modifying the microstructures and mechanical properties. For getting different quenched and tempered martensite phase, samples from the hot rolled plates were austenitised at 910°C and held at this temperature for 12 minutes followed by quenching in oil to get a fully martensitic phase. The austenitisation temperature has been taken from the previous heat treatment studies on this steel (Jena et al., 2010). The plates were then immediately tempered at temperatures of 200, 300, 400, 500, 600°C for 24 minutes followed by cooling to room temperature in air. Austenitizing and tempering were carried out in a neutral atmosphere furnace.