For repairing large holes in iron castings, welding can be used. First, a suitable welding material, such as cast iron welding rod, is selected, filled into the hole, and heat-treated to make it integrate with the original cast iron. This method can effectively repair large holes, but attention should be paid to the control of welding process and heat treatment to avoid new cracks or deformation. In addition, adhesive repair can also be used. Choose high-strength adhesive to bond the broken cast iron together. This method is suitable for small holes or complicated shapes, but attention should be paid to selecting suitable adhesives and ensuring the cleanliness of the bonding surface and sufficient bonding strength. In addition, filling and repairing methods can also be adopted. Use a special cast iron repair material, fill it in the hole, and then polish it to make it smooth and consistent with the surrounding cast iron surface. This method is suitable for small holes and high surface requirements.