RELATION BETWEEN EQUIVALENT CONTACT RESIS TANCE AND RESISTANCE SEAM WELDABILITY FOR BEVERAGE CANS

Welded cans for beverages amount to over 1 million cans/year and take an important role in the field of steel package industry. Under the in tense competition among other materials, can cost reduction and high p roductivity, which usually lead to the worse weldability must be over come steadily. Until recently, several authors reported that the stati c electric contant resistance between welded materials strongly influe nced weldability. However, the static contact resistance could not be the index of the dynamic high speed welding. The weldability using hig h speed seam welder was hardly experimented and discussed quantitative ly because the dynamic electric resistance could not be divided into t he contact resistance and the bulk resistance. In this report, the eff ects of the main parameters on weldability, namely tin coating weight, steel thickness and welding speed, were investigated in connection wi th the equivalent contact resistance by subtracting the calculated bul k resistance from the measured total resistance during high speed weld ing It made clear that the contact length between material and electro de correlates with the available welding current range. The weldabilit y deteriorated with the decrease of tin coating weight and the decreas e of steel thickness because of the increased contact resistance and w ith the increase of welding speed because of the increased discontinui ty of HAZ pattern.