摘要
For some casting low-alloy steels,traditional quenching and tempering heat treatments can improve the strength;however,sometimes the ductility is not satisf ied.Therefore,some kind of effective heat treatment method seems necessary;one which could improve the ductility,but not seriously affect the strength.In this paper,the effect of inter-critical quenching(IQ)on the mechanical properties of casting low-alloy steel was studied.IQ was added between quenching and tempering heat treatment;and the microstructure and mechanical properties were compared to the same steel with the traditional quenching and tempering treatments.The experimental results show that the microstructure comprises small-size ferrite and martensite when the IQ is adopted;and that different temperatures can control the ferrite quantity and distribution,and,as a result,infl uence the mechanical properties.In the case of IQ,the tensile strength decreases just a little,but the ductility increases a lot;and the strength-ductility product(its value is the arithmetic product of elongation and tensile strength)increases by between 6%and 10%,which means the IQ heat treatment can improve comprehensive mechanical properties.
For some casting low-alloy steels, traditional quenching and tempering heat treatments can improve the strength; however, sometimes the ductility is not satisfied. Therefore, some kind of effective heat treatment method seems necessary; one which could improve the ductility, but not seriously affect the strength. In this paper, the effect of inter-critical quenching （IQ） on the mechanical properties of casting low-alloy steel was studied. IQ was added between quenching and tempering heat treatment; and the microstructure and mechanical properties were compared to the same steel with the traditional quenching and tempering treatments. The experimental results show that the microstructure comprises small-size ferrite and martensite when the IQ is adopted; and that different temperatures can control the ferrite quantity and distribution, and, as a result, influence the mechanical properties. In the case of IQ, the tensile strength decreases just a little, but the ductility increases a lot; and the strength-ductility product （its value is the arithmetic product of elongation and tensile strength） increases by between 6% and 10%, which means the IQ heat treatment can improve comprehensive mechanical properties.
