Calculating the Susceptibility of Carbon Steels to Solidification Cracking During Welding

Existing experimental results of weldability tests show the susceptibility of carbon steels to solidification cracking varies significantly with the C content. To analyze the effect of the C content on the susceptibility, equilibrium solidification of binary Fe-C alloys was assumed as an approximation in view of the rapid diffusion of the interstitial solute C in Fe. First, the curve of the equilibrium freezing temperature range vs. the C content was plotted and compared with the experimental results, but the agreement was not good. Then, the susceptibility index, i.e., |dT/d(f_S)^1/2| near (f_S)^1/2 = 1 (T: temperature; f_S: fraction solid) recently proposed for Al alloys was tried. The curve of the susceptibility index vs. the C content was calculated. The curve agreed well with the experimental results of crack susceptibility tests of carbon steels in welding.