The higher the carbon content, welding worse, the greater the sensitivity to crack.Cast iron crack mainly due to: in the welding process, due to uneven heating, the weldment have a great tensile stress. In the following 400 ℃, iron substantially no plasticity. When the tensile stress is greater than the tensile strength of the material, it will crack. Therefore must be preheated before welding. Control of the weld cooling rate. Extension of the fusion zone red hot time. Graphite can fully precipitated
