TWI Industrial Member Report Summary 582/1996
During flux-based arc welding, chemical reactions occur between the molten metal, flux and the gas phase. The extent of reaction depends on the compositions of the filler metal, flux, parent material and gas phase present, and on the reaction temperature and time. These reactions will determine the weld metal composition, and ultimately, microstructure and properties.
In essence, the main reactions occurring during welding are the same as during primary and secondary steelmaking, albeit at a higher temperature and over a much shorter period of time. This study has sought to extend the steelmaking approach to modelling of weld metal composition.
As an initial basis to a model, the chemical reactions considered were limited to those involving weld metal and flux; further, to indicate whether or not the major reactions could be successfully predicted, attention was concentrated on the Mn and Si equilibria. In particular this work studied application of a thermo-dynamic approach, the 'Kapoor-Frohberg model', used in steelmaking to calculate oxide activities in slag, as the basis for prediction of weld metal Mn and Si contents. Trial welds were carried out using the manual metal arc process with a variety of plate and electrode compositions, to provide data to test the model. Different reaction temperatures were examined to ascertain the most appropriate equilibrium temperature.
- To develop a method of predicting weld metal Mn and Si contents using input variables of consumable and parent plate compositions.