铝热焊接不锈钢包钢复合材料接头界面组织研究

Microstructures of stainless steel clad steel composite materials welded by exothermic welding

以一种新型接地网材料——不锈钢包钢复合材料为被焊母材,采用市售、进口以及自主研发的三种铝热焊粉,实施铝热焊接,对接头界面组织及其形成机理进行了系统研究。结果表明,三种焊粉焊接接头界面组织结构类似,接头界面形成Cu(s,s)/Cu(s,s)+Fe(s,s)/Fe(s,s)的过渡组织界面,Cu基体内存在粒状、离散分布的富Fe相,其形成机理为钢在铝热焊粉反应后生成的高温铜液作用下熔化,随后在原子溶解、扩散共同作用下形成。铝热焊粉中添加活性剂粉末可以有效净化铜液,提高铜液流动性,有利于气体排出从而消除气孔缺陷。添加萤石粉、硅钡钙等造渣剂则可显著增强造渣、排渣作用。

Three kinds of exothermic welding powders such as commercial powders,imported powders and self-developed powders were used to join the stainless steel clad steel materials which have broad application prospects in grounding grid. The microstructure of the joint and its formation mechanism were studied. The results showed that the stainless steel clad steel joints welded by the three kinds of exothermic welding powders show the similar microstructure characteristics. The obvious diffusion zone was found at Cu/steel interface. The typical interfacial structures in welded joint are Cu( s,s)/Cu( s,s) + Fe( s,s)/Fe( s,s) and the granular Fe-rich phase discretely distributes in the Cu( s,s)matrix. The formation of joint microstructure attributes to the dissolving and diffusing of steel into the molten copper after the exothermic chemical reaction. The results also revealed that the addition of active agents into exothermic powders plays an important role in purifying the joints and improves the followability of molted copper,which leads to the sound joint without pores and defects. On other hand,the addition of fluorite and SiG aB a powders can obviously enhance the slag removal function during chemical reaction process.