【摘要】 用Gleeble-1500热/力模拟机测试了X60、X65、X70钢铸坯的高温延塑性,并进行对比研究。通过扫描电镜、金相显微镜对断口形貌及组织进行分析,得出主要结论:高温脆性区(Tl~1 300℃)钢的延塑性主要受碳含量多少的影响,相比较X70的塑性较好;高温高塑性区(1100~1 300℃)由于试验应变速率小于10-2/s时,该区域不存在脆化,3个钢种塑性均很好;在塑性槽高温端(900~1100℃),由于低熔点硫化物等析出,弱化晶界,另外动态再结晶发生温度的不同,导致两个钢种塑性的明显差别;塑性槽两相区(700~900℃)先共析铁素体的出现是3个钢种塑性很低的共同原因,MnS和钛可以促进铁素体在晶内和晶界同时生成,750℃以下,3个钢种延塑性均有所提高,X65塑性恢复较快。更多还原

【Abstract】 The present paper studied and compared the high temperature ductility of slabs of pipeline steels X60,X65 and X70 by means of a thermodynamic simulator Gleeble-1500 and analyzed their fractography and metallic phase tissue by SEM and optical microscope.The conclusions derived from the above-mentioned analysis is as follows: in the high temperrature brittle zone(Tl~1 300 ℃) the ductility of the steel is primarily affected by carbon content in steel and X70 shows better ductility in comparison with that of other two steels;and in the high temperature-high ductility zone(1 100～1 300 ℃) the ductilities of all three steels are excellent because no brittlement occurs in the zone when the strain rate in the experiment is less than 10-2/s;and at the upper side of the ductility trough(900～1 100 ℃)precipitation of the low melting point sulfide,weakening of the grain boundary and difference of the dynamic recrystallization temperatures lead to obvious difference of ductilities of two steels;and in the dual-phase zone of the ductility trough(700～900 ℃)occurrence of the precipitated proeutectoid ferrite is assumed to be the primary cause to the extra-ordinary low ductilities of all three steels and existence of MnS and Ti can promote formation of ferrite in the crystal interior and at the grain boundary simultaneously;and at 750 ℃ below the ductilities of all three steels are improved,and the ductility of steel X65 recovers faster.更多还原