Effect of tempering process on microstructure and mechanical properties of BJ890 steel
The microstructure and mechanical properties of BJ890 seamless pipe for boom were studied using optical microscope(OM),scanning electron microscope(SEM),electron backscatter diffraction(EBSD),transmission electron microscope(TEM),universal testing machine and impact testing machine.The results show that with the increase of tempering temperature,the martensite decomposes,the carbides precipitate,the strength decreases,and the toughness increases.The optimal quenching and tempering process for BJ890 steel is 920 ℃ quenching+620 ℃ tempering.Tempering at 620 ℃ within 60min,the grain size remains basically unchanged,and the grain size obviously increase after tempering for 120 min and the precipitation and growth of carbides were observed.With the increase of tempering time,the shape of carbides is gradually changing from"short rod shape"to"spherical shape".Moreover,the strength of the tested steel decreases and the impact toughness increases,but the change of impact toughness is not obvious after tempering for more than 60 min.The optimal heat treatment process is 920 ℃ for 14 min quenching,620 ℃ for 60 min tempering.The tensile strength is 1 025 MPa,the yield strength is 983 MPa,the elongation is 19.56％,the impact energy at-20 ℃ is 110 J,the impact energy at-40 ℃ is 69 J,the ductile-brittle transition temperature is-30.1 ℃ in ETT code,and the ductile-brittle transition temperature is-43.4 ℃ in AFTT code.
BJ890 steeltemperingcementitetoughnessductile-brittle transition temperature
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NSTL
万方数据
维普
