Estimating the cooling rates of a spot welding nugget in stainless steel

Cooling rates at different areas of a spot welded nugget in a 1Cr18Ni9Ti stainless steel material were investigated based on the rapid solidification theory and Furer-Wunderlin secondary dendrite arm spacing (SDAS) model. In the calculation of the cooling rates by using a SDAS method, only the diffusion of carbon atoms, which spread rapidly as a solute element in the solid phase, was considered. The experimental results show that the SDAS values in a 1Cr18Ni9Ti spot welded nugget exhibited significant variation even for those on the same primary dendrite axis. The estimated cooling rate from the nugget edge to nugget center decreased from an order of magnitude 105 to 104 K/s.