Under the intense competition among many packages, the welded can such as beverage can, food can and aerosol can occupies a dominant position owing to the rational manufucturing process of resistance seam welding. However, the seam welding process itself is further needed to increase the welding speed to improve the productivity without increasing the steel thickness and also the coating weight. To overcome this subject, the authors investigated the effect of main parameters on weldability and established two-dimensional model for calculation in the former reports. As a result, it was exemplified the importance of the current path length during welding at the interfaces.
The above result reminds us that the actual welding machine has a pair of different size electrode, therefore the current path length is considered to be different. The differencially coated tinplate sheet was prepared to change the current path length at the interfaces. Incidentally, tin free steel was prepared to change the current path lengths at the interfaces by pre-pressing of welding part. The same model was applied to compare the culculation results of the differentially coated tinplate with that of equally coated one. Finally, the calculation proved the results that the heat balance between two interfaces is very important and the weldability can be improved by the balance of current path lengths by decreasing the tin coating weight of upper side.
