Repair of welded components

1. In addition to commonly used nail openers, what other methods can remove damaged or rusted screws? Two methods are mainly introduced here.

① If the installed screw will not be damaged when heated, you can use an oxygen-acetylene torch to heat the nut and its assembly until it is red hot, and then quickly water quench it to facilitate the removal of the screw. This process may require several heating , Cold quenching cycle process.

② If the screw groove, nut or alveolar is damaged or lost, you can place a nut on the upper part (or remaining part) of the screw head, tighten the nut, and then use any welding method to fill the inside of the nut and screw with metal. This will connect the nut to the remaining part of the screw, and then place a wrench or pliers on the nut to quickly pull out the screw. Adopting this method is beneficial to provide a new grip point and can use heat to tighten the screws. The residual part of the fixing screws is removed by welding, as shown in Figure 4.

2. If there is a worn crankshaft, what is the best way to repair and reinforce it by welding?

When repairing a worn crankshaft, MIG welding, flux-cored gas welding or argon tungsten arc welding can be used. However, in order to obtain a satisfactory surfacing weld bead shape, the following four requirements must be paid attention to.

① Make the direction of the surfacing weld bead parallel to the axis of the crankshaft.

② First build up a weld bead on the lower part of the crankshaft, and then rotate the crankshaft 180° to build up the next weld bead, which can balance the welding stress and significantly eliminate welding thermal deformation. It should be noted that sequential surfacing on the first weld pass will cause the crankshaft to warp. The surfacing process is suitable for repairing and welding the roller crankshaft.

③ 30%-50% of the deposited metal overlap must be maintained between the two weld beads to ensure the smooth surface of the weld bead during machining after welding repair.

④ When manual arc welding and flux-cored wire gas shielded welding are used, brushes or cutting methods must be used to clean the residual flux between the weld beads.

In addition to the above crankshaft repair method, it is also possible to add a surfacing weld bead at every 90° position of the crankshaft to further reduce welding distortion. In the repair of bronze or copper parts, adding brazing metal is more advantageous in eliminating stress and deformation than using surfacing. The schematic diagram of repairing a worn crankshaft by welding is shown in Figure 5.

3. If there is a steel bearing part stuck in the equipment and you don't want to scrap the equipment, how should the welding method be used to remove the bearing?

First, a weld bead is welded on the inner surface of the bearing, and the diameter of the bearing is reduced by the tensile force of the weld bead, and the heat of the welding process should make the bearing move. A pipe with a diameter of 10cm will shrink the pipe diameter by 1.2mm if the inner surface is covered with weld beads.

4. The structure of oil tank or ship plate often has cracks, how to prevent it?

The solution is to first drill a small hole at the end of the crack to help disperse the stress at the end in a larger range, and then weld a series of multi-pass welds with different lengths to increase the strength of the steel plate at the front of the crack.