高强度钢制轴类零件加工制造中开裂原因分析与工艺改进

用超高强度钢制造的飞机起落架上的轴类零件，在机械加工过程中(镀铬层磨削中)经常出现表面开裂现象，裂纹特征基本相同。通过金相检验和显微硬度分析，发现零件在镀铬磨削过程中，次表面组织和显微硬度均发生了变化；对铬层实际厚度和除氢效果以及磨削过程进行分析，零件两端在磨削过程中均承受较高的拉应力，开裂属氢脆和应力腐蚀所致。控制镀层厚度和磨削参数，以及增加磨后回火工序等措施，大大降低了零件的报废率，取得了较好的经济效益。

ANALYSIS OF CRACKING RESULTED DURING MACHINING AXLE PINS FOR AIRCRAFT LANDING GEARS AND TECHNIQUE IMPROVEMENT PROCESS IMPROVEMENT

Due to the force bearing purpose on aircraft landing gears, axle pins are typically made with ultra high strength steel in design. It is necessary for these parts processing by heat treatment, surface treatment and grinding treatment, etc. Usually the cracks were founded during grinding as the last processing, and the characteristics were also mainly same. The metallograph examination showed that the subsurface microstructure and microhardness were changed during grinding. The analysis for the practical thicknes of Cr layer, dehydrogen and grinding processing were made. The results revealed that the cracks resulted from hydrogen embitterment and stress corrosion as a result of higher tensile stress. Finally some measures such as controlling the thickness of plating and gringding parameters, adding to temperaion processing, etc. were made, which reduced waste product rate and increased a better economic benefit on a great extent.