1. The structure of the welded parts is relatively complex, the defects are located in the middle part, the cutting plane, uneven thickness, four walls are involved, and the stress after welding is not easy to eliminate, resulting in cracks, such as cracks between valve seats and between cylinder ports in the cylinder block. When welding these weldments, nickel base electrode (Z308) cold welding method shall be selected for repair.

2. When cold welding machine is used to repair defects located at the edge with small stress and defects on the cutting surface, such as cracks between cylinder head screw holes and water channel holes, cracks extending from water channel holes to the edge, nickel based electrode and copper based electrode arc cold welding method can be selected.

3 for the defects at the thin wall in the center of the non cutting surface, the stress is often difficult to eliminate, such as cracks in the water channel of the cylinder block or tamping the cylinder, it is best to use j506 carbon steel electrode for arc cold welding, repair plate method for arc cold welding, etc.

4 at the edge with wall thickness greater than 15mm, if cracks appear on the side wall of rear axle, Z208 electrode semi hot welding method or J422, j506 and other low carbon steel electrode arc cold welding method can be used.

5 for small parts with compact structure, if the defect occurs at places with large wall thickness, such as fracture at shaft sleeve hole or crack welding repair of balance arm of supporting trolley, welding rod, groove and continuous arc welding can be used.

6 the parts with high strength requirements must be repaired by mixed welding, that is, bolt reinforcement and steel plate reinforcement. The cracks of the diaphragm seat of the rear axle body shall be repaired by bolt reinforcement.