X80钢的热处理组织和性能研究

Study on Heat Treatment Microstructure and Mechanical Properties of X80 Steel

利用组织分析、力学性能试验、断口分析等手段,对X80钢的热处理组织和性能进行了研究。结果表明,950℃加热可以使X80钢获得细小、均匀的奥氏体晶粒,适合作为X80钢的淬火温度;在550℃、600℃回火时,X80钢的组织为贝氏体铁素体(BF)+粒状贝氏体(GB),部分铁素体板条合并宽化,部分粒状贝氏体内部亚板条界开始合并消失,粒状贝氏体内部M/A组元颗粒呈球状存在,表现出一定的回火稳定性;650℃回火后,X80钢的组织为粒状贝氏体+准多边形铁素体组织,原贝氏体铁素体板条合并,形成更为细小的粒状贝氏体晶粒,使其表现出良好的强韧性配合;700℃回火后,X80钢的组织以准多边形铁素体(QF)为主,导致屈服强度的严重下降,M/A组元在准多边形铁素体晶粒边界聚集、长大,使该钢表现出较差的低温韧性。

The heat treatment microstructure and properties of X80 steel were analyzed by means of structure analysis,mechanical properties test and fracture analysis.The results showed fine and well-proportioned austenitic grain is obtained,when X80 steel is heated at 950 ℃,950 ℃ is applicable quenching temperature for X80 steel.The microstructure of X80 steel is bainite ferrite（BF） ＋ granular bainite（GB） when steel is tempered at 550 ℃ and 600 ℃,partial ferrite laths in BF merge and broaden,the interior sub-lath boundary in GB begin to merge and disappear,and the M/A constituent（a mixture of martensite plus retained austenite） in GB is orbicular,at the two tempering temperature the X80 steel shows a certain degree of tempering stability.The microstructure of X80 steel is GB ＋ quasi-polygonal ferrite（QF） after 650 ℃ tempering,the original BF laths merge to form smaller GB crystal grains,it is the reason that the steel shows good combination of strength and toughness.The microstructure of X80 steel is mainly QF after 700 ℃ tempering,which can cause serious reduction of yield strength.The M/A constituent assemble and grow up in the grain boundary of QF,which cause worse low-temperature toughness for X80 steel.