热处理对大截面LS8铸钢组织和性能的影响

Effect of heat treatment on microstructure and properties of LS8 cast steel with large section

对自主研发的LS8铸钢大截面试样采用完全淬火+高温回火(QT)、亚温淬火+高温回火(LT)和完全淬火+亚温淬火+高温回火(QLT)3种不同工艺进行热处理,分析了热处理工艺对大截面试样组织和力学性能的影响。结果表明,经QLT工艺处理后大截面试样心部的低温冲击性能最好,满足API Spec 8C要求。显微组织观察及冲击断口形貌分析结果表明,低温冲击性能的提高与亚温淬火后组织中弥散分布的细小铁素体有关。

Large section LS8 cast steel was treated with three types of heat treatment processes, i. e. complete quenching ＋ high-temperature tempering （ QT）, subcritical quenching ＋ high-temperature tempering （LT） and complete quenching ＋ subcritical quenching ＋ high- temperature tempering （QLT） ,respectively. Effect of heat treatment process on microstructure and mechanical properties of the large section sample was analyzed. The results show that the low-temperature impact property at the core of the large section sample is the best when with QLT treatment, which can meet the requirements of API Spec 8C standard. The results of microstructure observation and fracture morphology analysis indicate that the improvment of low-temperature impact property is relevant to fine and dispersive ferrite in the mierostructure by subcritical quenching.