''the Effect of Tempering Temperature on the Hardness of 420 Stainless Steel''

The effect of tempering temperature on the hardness and microstructure of 420 stainless steel has been experimentally studied. Samples of 420 stainless steel were Austenitized at 1000℃ for 75 min and quenched in 4.5 bar nitrogen. The as-quenched hardness was found to be 51.4 RC. The as-quenched steel was tempered at 204℃, 232℃, 260℃, 288℃, 302℃, 316℃, 343℃, 371℃ for 1 hour. A peak in the hardness was found at 288℃. These hardness variations are discussed in terms of the carbide development in the tempered 420 stainless steel.