Manabu Mizumoto

Development of Stainless Steel Welding Wire for Galvanized Steel Sheets

Galvanized steel sheets are widely-used in the construction and automobile industries to provide structural members with high corrosion resistance. When galvanized sheets are welded, zinc near a weld molten pool evaporates. As a result, the corrosion resistance is deteriorated and repair coating treatment is required after welding. The use of austenitic stainless steel welding materials with suitable ductility and high corrosion resistance appears to be beneficial. However, the conventional welding materials have such problems that zinc liquation cracking is likely to occur in the weld metal, a lot of welding spatter is generated and solidified slag is difficult to remove from the weld bead. To solve these problems, an austenitic stainless steel flux-cored wire was developed. Susceptibility to zinc liquation cracking was improved by increasing the ferrite content in the weld metal through the adjustment of Ni and Cr contents. The problems of the removal of solidified slag and the generation of welding spatter were solved by reducing the TiO2 content in flux to a level lower than that for a commercial wire. Thus, the weld appearance was improved, making repair coating treatment after welding unnecessary. The joints welded by the newly-developed welding material exhibited suitable mechanical properties and satisfactory corrosion resistance evaluated by salt spray testing.