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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。
The self-developed LS8 cast steel large cross-section specimens were tested by three different processes: complete quenching + high temperature tempering (QT), sub-temperature quenching + high temperature tempering (LT) and complete quenching + sub-temperature quenching + high temperature tempering (QLT) After heat treatment, the effect of heat treatment on the microstructure and mechanical properties of large cross-section specimens was analyzed. The results show that the core of the large cross-section sample after QLT treatment has the best low-temperature impact performance and meets the requirements of API Spec 8C. The results of microstructure observation and impact fracture analysis show that the improvement of low temperature impact properties is related to the fine ferrite distributed diffusely in the microstructure after sub-temperature quenching.