With the introduction of new high strength steels for new generation pipelines, there is a need for weld metal regions with matching strength and toughness.  It is well known that, maximization of acicular ferrite will lead to optimum combination of strength and toughness.  In the late 1980’s extensive research was performed by Evans and his co-workers through systematic variations of different substitutional element concentrations in a base Fe-C system.  However, there are no detailed guidelines for concentration limits that can be explored to maximize acicular ferrite.  Since experimental verifications are time consuming, a numerical optimization methodology was used in this work. 
A published weld metal microstructure model was coupled with commercial optimization software. The optimization software was designed to explore thousands of weld metal compositions that will maximize acicular ferrite. The concentrations of carbon, silicon, manganese, nickel, molybdenum and chromium were varied within a range from 0 to 2 wt.%.  In addition, the calculations were constrained to maintain a small amount of allotriomorphic ferrite to avoid the formation of grain boundary nucleated bainitic microstructure.  The calculations were performed for manual metal arc welding process with a heat input of 1 kJ/mm.  The inter-pass temperature was maintained at 200 °C.  The optimization calculations were started with different initial compositions.  The optimization software used a hybrid methodology that couples genetic algorithm and other stochastic techniques. 
Depending upon the initial composition, optimization calculations took different number of iterations to arrive at a weld metal composition with maximum acicular ferrite.  Interestingly, many sets of weld metal compositions with different carbon, silicon, manganese, chromium, molybdenum, and vanadium concentrations lead to maximum acicular ferrite.  This indicates that there exists wide range of weld metal composition that can be used for developing new pipeline welding consumables.