回火保温时间对A-100钢力学性能和组织的影响

采用力学性能测试、显微组织观察和断口失效分析等方法研究了回火保温时间对淬火+深冷处理后的A-100超高强度钢组织和力学性能的影响。结果表明,A-100超高强度钢482 ℃回火时在板条马氏体晶界上会析出逆转变奥氏体,马氏体周围析出M₂C型碳化物,且随回火保温时间增加,逆转变奥氏体数量增多、分散更均匀,马氏体晶粒尺寸有所增大;回火保温时间从5 h增加到8 h,规定塑性延伸强度从1890 MPa降低到1728 MPa,下降约8.57%;抗拉强度从2045 MPa降低到1988 MPa,下降约2.78%;而断裂韧性却从98.75 MPa·m^1/2上升到114.3 MPa·m^1/2,增加约15.74%。增加回火保温时间,冲击断口的韧窝区面积降低,平均韧窝区面积约占总断口面积由回火保温5 h的86.2%降到回火保温8 h的70.1%。

Effect of tempering time on mechanical properties and microstructure of A-100 steel

Effect of tempering time on microstructure and mechanical properties of A-100 ultra-high strength steel after quenching+cryotreatment was studied by means of mechanical properties test,microstructure observation and fracture failure analysis.The results show that,when the A-100 steel tempered at 482℃,the reversed austenite is precipitated at the grain boundary of lath martensite,and M2 C-type carbide is precipitated around martensite.With the increase of tempering time,the amount of reversed austenite increases and disperses more uniformly,and the grain size of the martensite increases.With the increase of tempering time from 5 h to 8 h,the proof strength,plastic extension decreases from 1890 MPa to 1728 MPa;the tensile strength decreases from 2045 MPa to 1988 MPa,decreasing by about 8.57%and 2.78%respectively.However,the fracture toughness increases from 98.75 MPa·m^1/2to 114.3 MPa·m^1/2,increasing by about15.74%.When increasing tempering time,the dimple area of impact fracture decreases,and the average dimple area accounts for roughly is86.2%of the total area after tempering for 5 h,while decreasing by about 70.1%when tempering for 8 h.