Study on methods to improve the impact toughness of steel 40XA

In this paper, methods of improving the toughness, eliminating the tempering embrittlement of steel 40XA (GOST 4543 -71) were used. The mechanical properties of this steel after conventional oil quenching followed by high temperature tempering with air cooling and with oil cooling after high temperature tempering were investigat- ed. Besides, a double quenching process consisting of a preliminary quenching from high temperature and a sec- ondary quenching with intermediate holding at sub-critical temperature was conducted. After this double quench- ing and high temperature tempering, the steel acquired mechanical properties (tensile strength, elongation and impact toughness) notably higher than the respective properties obtained by conventional heat treating. These research results can be applied to improve the mechanical properties of important details from this steel.