Most likely you need to use a modified form of the Rosenthal Equation to calculate the temperature profile adjacent to a weld during weld solidification. Several of the inputs for this equation are; weld arc efficiency factor, thermal conductivity and diffusivity of the parent metal, preheat, thickness, and heat input from welding.
One of the reference books that would help you is Welding Metallurgy by Sindo Kao. You might try a local University library.