めっき鋼板のスポット溶接性

Abstract

This report is concerned with the weldability, especially the characteristic of the nugget formation in the spot welding of metal plated steel. The factors which determine the characteristic of the nugget formation are as follows, i) the melting point of plated material, ii) the surface condition of plated material and base material.In case of one side plated steel, the influence of the melting point of plated material on the characteristic of the nugget formation depends upon the combination of the plated film; that is, the plated sides face to face or the plated sides face with electrodes. For instance, in case of the plated sides face with electrodes, the plated film with 800°C melting point doesn't melt during welding because electrode is cooled by water. In case of the plated sides face to face, the same film melts because interface is the nugget formation area. As a result, the current density during welding depends upon the combination of the plated film.In case of the both side plated steel, the nugget formation is more difficult than that in one side plated steel.In addition, nugget formation is also influenced by the surface condition of the plated material. In case of the base material, the same tendency is obtained. This surface condition means the amount of oxides on the surface of the plated material or the base material. For instance, the increasing of the amount of oxides means the increase of the resistivity, and thus current path is restricted. As a result, the nugget is easily formed.