降低铸铁件残余应力的研究及在机床床身上的应用

昵称54482731 2018-04-19

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摘要：床身铸件因残余应力释放而导致的变形，严重影响其尺寸精度。本研究采用盲孔法测量灰铸铁、球墨铸铁应力框试样的残余应力，研究了碳当量、打箱温度、振动时效、热时效等对机床床身用灰铸铁、球墨铸铁件残余应力的影响，获得降低铸铁件残余应力的技术措施并应用于机床床身。研究表明：适当提高碳当量和降低打箱温度均有利于降低铸态灰铸铁、球墨铸铁件的残余应力，推荐灰铸铁和球墨铸铁的碳当量分别为3.65%~3.85%和4.40%~4.60%、打箱温度低于300℃；“阶梯式升温降温法”热时效能显著降低残余应力，时效后HT300灰铸铁和QT600-3球墨铸铁试样的残余应力分别低于20MPa和50MPa，振动时效能降低残余应力，但其效果不及热时效。

关键词:床身铸件；残余应力；碳当量；打箱温度；热时效；振动时效

Study on Reducing the Residual Stress ofIron Casting and

theApplication in Machine Tool Lathe Bed

WEI Dong-hai,LI Ke-rui,WUXian-long,LI Tong,ZHAO Huai-pu

(Zhengzhou Research Institute ofMechanical Engineering，Zhengzhou450001，Henan)Abstract:Deformation of lathe bed casting caused by the residual stress releasing seriously influences thedimension precision.The residual stress of gray iron and ductile iron stress frames were measured with blind holemethod in this study.The effect of carbon equivalent,shakeout temperature,vibration aging,heat aging on residualstresss ofgray iron and ductile iron castings used for machine tool lathe bed was studied.The results show that highercarbon equivalent and lower shakeout temperature both can reduce the residual stress ofas-cast gray iron and ductileiron.The recommended carbon equivalent ofgray iron and ductile iron respectively is3.65~3.85%and4.40~4.60%.The shakeouttemperature shouldbe below300℃.The“Multistep temperature rising/falling”heat aging treatment cansignificantly reduce the residual stress.The residual stress of HT300gray iron and QT600-3ductile iron castingsrespectively is below20MPa and50MPa after the heat aging.Vibration aging can reduce the residual stress,but theeffect is less than heat aging.

Key words:lathe bed casting；residual stress；carbon equivalent；shakeouttemperature；heat aging；vibration aging

床身是机床的关键零部件，其尺寸精度及精度保持性是影响机床加工精度及其稳定性的重要因素，床身的重力、残余应力、装配应力及地脚螺栓布局优化等均对其精度保持有较大的影响，其中床身铸件在服役过程中因残余应力随时间的释放而导致的变形，对其尺寸精度及精度保持性的影响最为显著。目前国内铸铁件的残余应力普遍较高且变化幅度大，多为50~250MPa，因残余应力过高所引起铸件的开裂问题也是铸造行业的共性技术问题[1-2]，图1是某HT300灰铸铁床身铸件开裂的实例，表1是该铸件的残余应力测量结果，其最大残余应力高达254.7MPa。应力框试样的粗杆和细杆为刚性连接，能够代表床身铸件进行残余应力的试验研究，本工作采用中频感应电炉熔炼、树脂砂铸造工艺，浇注了不同碳当量的灰铸铁、球墨铸铁应力框铸件，并测量不同打箱温度下、热时效前后、振动时效前后灰铸铁和球墨铸铁件的残余应力，获得大量残余应力数据，系统地研究了碳当量、打箱温度、热时效、振动时效等对铸铁件残余应力的影响及降低残余应力的技术方法，使灰铸铁、球墨铸铁床身铸件的残余应力分别低于20MPa和50MPa，以减小铸件变形，防止开裂[3]。