Table 1 shows the chemical composition of
the steel used in investigation. The plate was cut into dimensions
of 20mm×50mm×1.2 mm.After grinding with emery
paper (#2000),the steels were HTGN heat-treated using a pressure
changeable furnace in an atmosphere containing 98.07 kPa
nitrogen gas at 1050 ◦C and 1100 ◦C,followed by water quenching.