【摘要】 通过OM、SEM、示波冲击和落锤试验研究了高钢级X100管线钢的显微组织、冲击和落锤断裂性能。结果表明,终冷温度为400℃时,试验钢具有更好的显微组织、冲击韧性和落锤断裂性能。400℃终冷试验钢组织均匀,LB、GB和M/A组元细小,原始奥氏体被LB板条束分割细化;终冷温度提高至520℃,试验钢组织均匀性变差,GB和M/A组元粗化,LB对组织的分割细化作用减弱。落锤断裂过程中,原始奥氏体晶界(PAGB)、LB和AF改变裂纹扩展方向,提高止裂性能。冲击试验温度降低,400℃终冷试验钢冲击吸收能量(E)、裂纹形成能(E1)、韧性扩展能(E2)和脆性裂纹扩展能(E3)变化不大。表征材料韧脆倾向的-60℃冲击(E2+E3)/E1值为2.83,呈韧性断裂;520℃终冷试验钢E、E1、E2和E3逐渐降低,-60℃冲击(E2+E3)/E1值为0.95,呈脆性断裂。更多还原

【Abstract】 High grade X100 pipeline steel’s microstructure,impact fracture and drow weight tear test( DWTT) properties were investigated by OM,SEM,instrumented. impact test and DWTT test. The results indicate that the tested steel shows better toughness and DWTT properties with the 400 ℃ final cooling temperature. The test steel’s microstructure consists of fine lath bainite( LB),granular baintie( GB),acicular ferrite( AF) and martensite/austenite( M/A) constituents. Prior austenite grain is segmented and refined by LB lath. Final cooling temperature raises to 520 ℃,microstructure’s uniformity becomes worse,GB and M /A constituents coarsen,LB’s refining effect weakens. Crack propagation direction changes at prior austenite grain boundary( PAGB),LB and AF during the DWTT fracture process.With the reducing of impact test temperature,the 400 ℃ final cooling test steel’s impact energy( E),crack formation energy( E1),ductility fracture propagating energy( E2) and brittle fracture propagating energy( E3) change a little. The( E2+ E3) /E1 value which characterizes the materials’ ductile-brittle transition tendency at- 60 ℃ is 2. 83,taking on ductile fracture. When the final cooling temperature raises to520 ℃,the E,E1,E2,E3 decrease significantly,and the( E2+ E3) /E1 value at- 60 ℃ is 0. 95,taking on brittle fracture.更多还原