Numerical Modelling of the High Speed Resistance Welding Process

High Speed Resistance Welding (HSRW) is a high volume welding technique for three-piece can body production using tin-plated steel with linear weld speeds of up to 115m.min^-1. At present can manufacturers predominantly use weld settings for their equipment that have an historic rather than scientific basis and they frequently return on-spec batches of steel as unweldable. The purpose of this body of work is to provide a better definition of weldability and to elaborate upon current understanding of the weld formation mechanism. Due to the nature of the process, complete understanding of weld evolution is hampered by the impossibility of measuring the exact physical phenomena taking place. This paper describes an attempt to mathematically model HSRW using a Finite Element model that sequentially couples a transient electro-thermal model (Joule heating, conduction and melting/solidification) to the elasto-plastic deformation taking place during the process arising from both applied loads and induced thermal stresses. Heat generation is an integral part of the HSRW process as high heating rates are necessary to achieve temperatures whereby solid state bonding of the steel can take place; erratic heat generation causes defect formation, poorer weld quality and thus reduces production efficiency. Validation of the model is attempted by matching the experimentally measured re-melted tin zone (a fairly robust measurement used in industry which indicates the position that the 232 degree Celsius isotherm reached on the post-weld surface of the can body) to simulations results. Conclusions are formed on defect origination and evolution, as well as a weldability theory linking process parameters to acceptable weld formation and phase changes.

FE Mesh                                                 Voltage Field

   Total Energy Input                          Maximum Temperature