Effects of Tempering Temperature on the Microstructure and Properties of HSLA Steel as Quenched and Tempered

The effect of tempering temperature on the mechanical property and microstructure of HSLA steel durng the quenched and tempered was researched by traditional mechanical testing equipment,OM and SEM.The results show that the microstructure of testing steel as hot rolling is ferrite+pearlite+a little bainite,and the characteristics of impact fracture is a brittle cleavage,and the microstructure after quenched and tempered is tempered sorbite + grainy carbide.The impact fracture belongs to gliding fracture with lots of dimple,and with the increase of tempering temperature,the proportions of fiber region and cut lips became bigger,the size and depth of the dimple increase,so the toughness and elongation increased,on the contrary,the yield strength and the tensile strength certainly decrease.The optimal process of this alloy is quenching at 930 ℃ and tempering at 650 ℃.