【摘要】 采用微观组织观察和准静态拉伸试验分析了冷速对X80管线钢的淬火双相组织及其应变硬化行为的影响.结果表明:X80管线钢通过淬火热处理获得铁素体+贝氏体的双相组织;随着冷速的降低,铁素体体积分数增加,强度降低,均匀伸长率增加;当铁素体体积分数不小于5.27%时,应变硬化指数与材料的均匀伸长率正相关,与屈强比负相关;当铁素体体积分数达到22.80%时,加工硬化率经历先快、后慢的两个下降阶段,后一阶段推迟了颈缩变形;淬火组织中的贝氏体随着冷速的降低,形貌由板条状转变为粒状,并生成了MA组元,通过位错强化、第二相强化机制的转换保证加工硬化性能,提高了均匀塑性变形能力.更多还原

【Abstract】 In the investigation,the microstructural observation and quasistatic tension experiments of X80 pipeline steel were conducted so as to reveal the effects of the cooling rate on its quenched dual-phase microstructure formation and strain-hardening behavior.The results show that(1)a dual-phase microstructure including ferrite and bainite is obtained after X80 pipeline steel is quenched;(2)the ferrite volume fraction and the uniform elongation increase with the decrease of the cooling rate while the strength decreases;(3)when the ferrite volume fraction is not less than5.27%,the strain-hardening exponent has a positive correlation with the uniform elongation but a negative correlation with the yield ratio;(4)when the ferrite volume fraction reaches up to 22.80%,the work-hardening rate decreases with a fast stage and then a slow stage,and the latter stage delays the necking point;and(5)with the decrease of the cooling rate,the lath-like bainite in the quenched microstructure turns to be granular and MA phase forms,simultaneously,the strain-hardening performance of the quenched microstructure is guaranteed and the uniform plastic deformation ability is improved by means of the conversion of the dislocation strengthening to the second phase strengthening.更多还原