4330锻件低温冲击功低的分析

Analysis of the low temperature Charpy impact of 4330 forgings

4330缸体锻件经过低温冲击检验后,发现检验结果不稳定,部分锻件的冲击试验数据远低于技术标准要求。材料形成沿晶断裂的原因一般与过热、过烧、晶界微量有害杂质元素偏聚、二类回火脆性等因素有关。本试验只针对锻件进行金相检验和扫描电镜组织分析。分析结果表明,粗晶区的Cr、Mn、Mo含量明显高于细晶区,尤其是Mn含量高出较多。结合冲击性能检验结果分析,枝晶组织的形貌对冲击性能的影响较明显,枝晶小、枝晶条带轻微和枝晶网细小对冲击性能的影响程度小,反之则影响较大。

After the low-temperature impact test of cylinder block forging 4330,it was found that the test results were unstable,and the impact test datas of some forgings were far below the technical standard requirements. The reasons for intergranular fracture were generally related to overheating,overburning,trace impurity segregation at the grain boundary and two types of temper brittleness. The metallographic examination and scanning electron microscope(SEM)analysis of the forgings were carried out. The results showed that the contents of Cr,Mn and Mo in the coarse grain region were obviously higher than those in the fine grain region,especially the Mn content was higher. According to the analysis of the impact test results,the influence of dendrite morphology on the impact properties was obvious. And the less obvious dendrite,slight dendrite strip and small dendrite mesh had a little influence on the impact properties. Otherwise,the influence was larger.