溶融Zn-6mass%Al-3mass%Mg合金めっき鋼板のスポット溶接電極寿命に及ぼす溶接電流波形の影響

摘要

Hot-Dip Zn-6mass%Al-3mass%Mg alloy coated steel sheets (ZAM) have superior corrosion resistance. In the assembling process of automotive parts or structural members, spot welding is widely used. Although, short or insufficient electrode life in the spot welding of the hot-dip Zn or Zn alloy coated steel sheet is one of the major issue. To improve the electrode life in spot welding of ZAM, a direct-current inverter spot welder was examined instead of single-phase alternating current spot welder. The results are as follows. (1) By using a direct-current inverter spot welder for ZAM, the optimum welding range is expanded. (2) Since a direct-current inverter spot welder can make the heat generation even with low electric current density due to a continuous electrifying, a nugget with enough size in diameter can be obtained by using the worn electrode. Therefore the spot welding electrode life in ZAM is vastly improved by a direct-current inverter spot welder.%溶融Zn-6mass%Al-3mass%Mg合金めっき鋼板（以下，ZAM鋼板と記す）は，優れた耐食性を有しており，自動車，建材分野を中心として，幅広い用途に適用されている。自動車部品や住宅構造部材などの組立てにおいてはスポット溶接が多用されているが，めっき鋼板はめっきを施していない鋼板に比べてスポット溶接時の電極寿命が短いなどの問題があるため，適正な溶接条件を把握する必要がある。ZAM鋼板は，一般的な亜鉛めっき鋼板と比べてめっき層の融点が低く，めっき層中にAlを含有することから，適正なスポット溶接条件を見出すために，これまで種々の報告がなされている。