Common defects of cast iron parts include: pores, sand sticking, sand inclusion, sand hole, expansion sand, cold barrier, insufficient pouring, shrinkage porosity, shrinkage cavity, lack of meat, sarcoma, etc. Why are there always defects in the lost wax casting process?
The gas does not escape in time before the molten metal is crusted, and thus the hole-like defects generated in the casting.
However, casting defects have always been a major problem that plagued foundry enterprises. Poor solutions to casting defects will affect the quality of castings. Various casting defects such as wear, scratches, blisters, pinholes, cracks, defects and deformations, reduced hardness, and damage occur in the process of producing machine tool parts, which increase the production cost of the enterprise.
Commonly used welding machines: currently on the market, welding repairs are used to repair defects, and generally there are the following types:
First, argon arc welding: aluminum alloy die castings are mostly welded with argon arc welding machines. Some mold manufacturing and repair manufacturers also use this welder to repair mold defects. Advantages: high welding repair efficiency and higher accuracy than electric welding machines. Disadvantages: Used for defect repair. When repairing small defects (pores, sand holes), there are traces on the edge of the molten pool (undercut phenomenon) due to excessive impact. Welded steel parts have hard spots. Due to thermal influence, thermal deformation is likely to occur when welding non-ferrous castings or thin-walled parts. Operational technical requirements are high.
Second, electric welding machine: the traditional method of welding and repairing cast iron and steel lost wax casting. Advantages: Repair major defects. Disadvantages: After welding, the hardness of the solder joints is too high, there are internal stresses, and cracks are easy to occur. Generally, annealing heat treatment is required to meet the processing requirements. In addition, due to the limitation of welding conditions, secondary defects such as pores and slag inclusion are prone to occur inside.
Cold welding machine: Imported foreign technology is introduced, and the special welding wire is cladding to the damaged part of the workpiece through the high heat energy generated by the micro-electric instantaneous discharge, and it is firmly welded to the original base material. After welding, it only needs to go through the post-treatment with little polishing.
Advantages: 1. No need to preheat, so there is no deformation, no blackening, undercut and residual stress, and no local annealing.
2. High efficiency and energy saving: Although only 1200W power, the welding repair speed and effect are several times that of the same 4000W.
3. Power supply: inverter power supply, energy saving and environmental protection, high efficiency, stable performance, light and smart machine
4. High repair accuracy: The thickness of the surfacing welding is from a few microns to a few millimeters, and only needs to be polished and polished. After the repair, the color difference is small or no color difference.
5. Environmental protection: There is no pollution in the working process.
6. Usability: It is easy for anyone to use, no operating license is required, and surfacing can also be carried out in places that are difficult to weld.
7. Economical: Repair immediately on site, improve production efficiency and save costs.