热镀锌高强钢点焊的电极磨损机理分析

Experimental study on electrode wear mechanism in resistance spot welding of high strength hot galvanization steels

关键词:  电极磨损  热镀锌高强钢  合金化  电阻点焊

Key words:  electrode wear  high strength hot galvanization steel  alloying  resistance spot welding

摘要:

热镀锌高强钢点焊的电极端面合金化作用机制复杂、电极磨损严重.进行磨损电极的元素成分与金相试验分析,研究电极端面合金化作用机制与微观组织演变规律,揭示其电极磨损机理.结果表明,在合金层中发现镀层中的Zn,Al元素,锌、铝与铜在不同温度与含量情况下形成不同相合金,使电极端面导电、导热能力变差,镀层中铝的存在是电极磨损严重的一个主要原因.电极端面的点蚀区域由于较高的温度与压力作用,很容易产生微裂纹,熔化的镀锌层金属元素沿微裂纹渗入电极内部,加速电极失效.电极再结晶区域发生组织再结晶,由柱状晶转变为等轴晶,使电极硬度降低,抗塑性变形能力变差.

Abstract:

Surface alloying mechanism on the electrode end face was complex and its wear was serious in welding of high strength hot galvanization steel.Elements composition and metallography experiment of the worn electrode were carried out to study the alloying on electrode end surface and microstructure evolvement.It was shown that the elements of Al, Zn etc were found in alloying layer.Different alloys were formed for different contents of Al, Zn at different temperatures, which decreased conductivity and heat conduction on electrode face.Al in coating was one of the main reasons that led to serious electrode wear.Pitting was grown obviously and micro cracks were produced at pitting region for higher temperature and pressure, the molten metal in coating penetrated into the electrode interior and accelerated electrode invalidation.The metal structure in recrystallization region was changed from columnar crystal to equiaxed crystal, which decreased hardness and anti-plastic deformation capability of electrode.