Developing mathematical models to predict grain size and hardness of argon tungsten pulse current arc welded titanium alloy

Titanium (Ti–6Al–4V) alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio, such as transportable bridge girders, military vehicles, road tankers and railway transport systems. The frequently preferred welding process of titanium alloy is argon tungsten arc welding due to its comparatively easier applicability and better economy. In case of single pass welding of thinner section of this alloy, pulse current was found beneficial due to its advantages over the conventional continuous current process. Many considerations have come into the picture and one need to carefully balance various pulse current parameters to arrive at an optimum combination. Hence, in this investigation an attempt has been made to develop mathematical models to predict grain size and hardness of argon tungsten pulse current arc welded titanium alloy weldments. Four factors, five level, central composite, rotatable design matrix is used to optimize the required number of experiments. The mathematical models were developed by response surface method (RSM). The adequacy of the models was checked by ANOVA technique. By using the developed mathematical models, grain size and hardness of the joints can be predicted with 99% confidence level.