自攻螺钉碳氮共渗黑色组织的产生及防止

对集装箱自攻螺钉在１８０ＫＷ无马弗网带炉机组上进行碳氮共渗后，出现渗层表面硬度分散的现象，进行金相分析，发现在离表面４０μｍ的范围内存在着点状黑色组织，导致渗层表面硬度偏低。检验证明点状黑色组织属孔洞，通过工艺试验找到可有效防止黑色组织产生的措施，使碳氮共渗表面硬度趋向集中并服从正态规律分布，使产品的质量更加稳定。

Dark Structure of Self-tapping Screw for Carbonitriding Process and Improvement

This paper deals with the dispersal phenomenon of surface hardness of screws which were carbonitrided in 180kW HT equi pment and used on container．From metallograph analysis，there is dark structure on the carbonitriding layer and it distributes under the surface for  40μm depth．This dark structure decreases the surface hardness of screw．Through HT technique test the normal structure and reasonable surface hardness has been obtained，the dark structure was avoided and the production quality was improved．