ZQ400-! -5Z reducer shell material is gray cast iron, gray cast iron solderability is poor, there are problems during welding: cast iron in the welding repair, due to the burning of silicon, while the welding is only local heating, the surrounding cold metal heat, Cooling is too rapid and the formation of 'white mouth' is aggravated. Therefore, white mouth becomes a serious problem in the welding process of cast iron; in the course of heating and cooling, a large internal stress is generated due to a volume change, often making the weld or Cracking of the base metal around the weld is another problem. Considering that the fracture belongs to the corner, the thickness is only 30mm and the length is less than 100mm (see). This is beneficial for welding. When the welding heat, it can swell freely and the internal stress is not very large. We used a hand-soldering welding process that was effective, difficult, and practical, using old piston rings as welding wires.
The fractures are scrubbed with caustic water, scrubbed with gasoline, and the remaining oil contamination is removed with a gas welding flame. Incombustible impurities are brushed with a steel brush to expose the metal surface.
Before welding, shovel the required 60-degree groove shape with a spatula and carefully grind it with an angle-wise grinding wheel. The shape of the bottom of the groove excavated by the shovel should be rounded (see); the angle of the groove is as small as possible, and the base metal is melted. The amount is reduced as much as possible to reduce the welding stress and the carbon, sulfur content in the weld and prevent cracking.
In order to prevent the molten iron from flowing when welding, the weld should be placed on a horizontal plane, surrounded by yellow mud or refractory material around the edges of the groove, and then welded to obtain a better shape.
The old piston ring of the welding material is used as welding wire and borax as flux; the acetylene torch is adjusted to a neutral flame and the weld is heated to a red hot state and sprinkled with borax; after the borax is melted uniformly, the base metal is partially melted and then melted into the piston. The ring metal, while adding some pressure on the piston ring, ensures that the filled piston ring metal and the base metal are well combined.
Then the entire weld seam is continuously welded; the welding speed is better, but if it is too fast, the welding is not firm and the edges are undercut.
During the welding process, the welding flame should always cover the molten pool while the flame swings back and forth to the pool. Always use a welding wire to gently stir the bath so that the slag can be removed at any time. Weld reshaping should be completed at the end of welding to reduce the difficulty of repairing the plane after repair. At this time, be sure to make the metal in the reshaping part reach the molten state, and then use the welding wire to flatten on the plane until it is satisfied. As the weld is long, it should be welded for a while.
Immediately after welding, the weldment is buried in pre-prepared lime and kept cool until it is cooled to room temperature before the weld is repaired.
Because the weld metallurgical structure is good, the processing performance is good, the average temperature of the substrate is low, and the deformation is small, so it can weld a good effect; because it is easy to remove slag, there are few inclusions and pores in the weld. This simple, low-cost welding process is often used to repair damaged cast iron parts at our plant and has achieved very good economic benefits.