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对Gcr15、CrWMn、T12等钢种高温淬火产生的显微裂纹进行观察分析,测定显微裂纹对机械性能的影响。结果发现三种钢均产生较多的显微裂纹,其长度可能接近马氏体针的长度。如果预淬火中产生了显微裂纹,则无论是长时间回火,还是重新低温淬火均不能消除,并且对冲击韧性(a_k)产生明显的影响。扫描断口观察表明,晶界显微裂纹具有更大的危险性。高温预处理中,避免显微裂纹的办法是采取贝氏体淬火或索氏体化处理,采取Ms以上中断冷却立即带温回火也能取得满意的结果。
The microscopic cracks caused by high temperature quenching of Gcr15, CrWMn and T12 steel were observed and analyzed, and the influence of microcrack on the mechanical properties was also measured. The results showed that all three kinds of steel produce more micro-cracks, the length of which may be close to the length of the martensite needle. If pre-quenching produces micro-cracks, neither long-term tempering nor re-low-temperature quenching can be eliminated and the impact toughness (a_k) is significantly affected. Scanning fracture observations show that the grain boundary microcracks have a greater risk. High temperature pretreatment, to avoid the micro-crack method is to take bainite quenching or sorbite treatment, to take more than Ms immediate cooling with tempering cooling can also get satisfactory results.