US Patent 7588837 Welding together low and high carbon steels

A weld joins a thin overlay of low carbon steel to a base that contains high carbon steel, at least at its surface along which the weld is formed. The weld may be effected by fusion (melting) or by solid-state diffusion. With either it creates a heat affected zone (HAZ) in the base around the weld. The HAZ contains enough austenite, and perhaps bainite as well, to render the HAZ relatively ductile and also crack resistant. Adjacent to the weld the HAZ has a hardness that does not exceed 58 HRC. The weld may be produced with a high energy beam or with resistance welding equipment.