托板螺钉镦挤成形热处理方案

针对飞机装配大量使用的托板螺钉的镦挤成形工艺,根据其冷镦丝材的材料特性和紧固件行业经验,确定经济、高效的回火预先热处理+回火最终热处理的初步热处理方案。为验证加工工艺的可靠性,根据产品安装和使用情况进行楔负载拉力试验,并对试验结果进行过程能力分析,结果证明:初步热处理方案存在质量隐患,产品的过程能力指数Cpk <0.67。对有质量隐患的产品进行理化试验分析后,证明原有热处理方案的流线和晶粒不均匀是产品不满足质量要求的主要原因。改用低温退火预先热处理工艺和镦挤成形后淬火+回火工艺,再进行楔负载拉力试验和金相检查,结果表明,过程能力指数Cpk>1.67,产品制造流程满足使用要求,加工的产品质量稳定。

Heat treatment scheme for support plate screw formed by upsetting

The support plate screws formed by upsetting process are widely used in aircraft assembly. Therefore,according to the material characteristics of cold upsetting wire and the experience of fastener industry,the cost-efficient preliminary heat treatment scheme of preheat treatment of tempering + final heat treatment of tempering was determined. In order to verify the reliability of processing technology,the wedge load tension test was conducted according to the installation and use of product,and the process capability analysis of the test results was conducted. The result proves that the preliminary heat treatment scheme has potential quality hazards with the product process capability index Cpk < 0. 67. After the physical and chemical test and analysis on the products with potential quality problems,it is proved that the uneven streamlines and grains of the original heat treatment scheme are the main reason why the products do not meet the quality requirements. Furthermore,the pre-heat treatment process of annealing at low temperature and the process of quenching + tempering after upsetting was adopted,and then the wedge load tension test and the metallographic examination were carried out to verify the process capability index Cpk > 1. 67. Thus,the product manufacturing process meets the use requirements,and the quality of processed product is stable.