摘要
德国产压铸模具用钢ES 344ESR合金,经1010℃淬火和620℃回火后,压铸生产铸件8000件后,表面产生严重裂纹。通过成分分析、硬度测试、金相组织观察和扫描电镜断口及组织分析,发现合金反常失效主要来自两个方面的原因。一是合金热处理后,残余奥氏体含量比较多,使用后硬度(HRC28)过低,加上合金中的碳化物呈网状分布,降低了冲击韧性;二是由于变质剂或除气剂中的氯在高温时和水蒸气一道在应力的作用下产生了应力腐蚀。文章最后提出了相应的改进建议。
A ES-344ESR Germany alloy was quenched at 1010°C and tempered at 620°C, and then was machined into aluminum casting die. Just about 8000 parts was cast, many severe cracks have been found on the surface of the die. Many methods, including hardness testing, optical microscopy (OM), scanning electronics microscopy (SEM) and energy-dispersive X-ray analysis (EDX) are used to analyze the failure case. It is discovered that two major factors contribute to the failure. The first factor is that the heat-treated alloy contained too much retained austenite and dissolved in the casting process, which leads to a low hardness value of HRC28 of the failure die. Additionally, a net-like distributed carbides leads to a low impact toughness. The second major factor for the failure is that Chlorine in the melt reacted with ferrite and water vapor at high temperature (higher than 700°C ), which causes stress-corrosion. Suggestions are also provided to improve the properties of the alloy.
出处
《铸造》
EI
CAS
CSCD
北大核心
2005年第2期157-160,共4页
Foundry
