How to repair casting defects

The most fundamental way to solve shrinkage defects in castings is "thermal balance". The method is:
(1) Rapid solidification is carried out in the thick areas and hot spots formed by the machine tool casting structure, artificially causing a basic balance of the temperature field everywhere in the machine tool casting. Internal and external cold iron is used, and zircon sand, chromite sand or special coatings with large heat storage are used locally.
(2) Reasonable process design. The inner runner is located at the opposite wall of the machine tool casting, and is often numerous and scattered. The molten metal that enters the thick wall at the earliest is solidified first, and the thin wall is solidified later, so that uniform solidification is basically achieved everywhere. For machine tool castings with uniform wall thickness, use multiple gates and vents. There are many internal sprues, which are dispersed and evenly distributed to balance the overall heat. The air outlets are thin and numerous, which means the exhaust is smooth and plays a role in heat dissipation.
(3) Change the position of the gate
(4) Choose modeling materials with large heat storage, which is extremely important for producing anti-wear products using lost foam! Chromite sand replaces quartz sand and other sand types with small heat storage, which will achieve good results, and the micro-shock after pouring will be even better!
(5) Low temperature and fast burning, open pouring system. Fill the mold with molten metal quickly, smoothly and evenly. This depends on circumstances.
(6) Ductile iron machine tool molds have high strength, surface hardness ≧90, and sand box rigidity, which is beneficial to eliminating shrinkage porosity.
(7) When a riser is needed, move the hot riser first and leave the hot section. If the riser is placed on a hot section, the size of the riser will be enlarged, resulting in "hot heating". If it is not done well, not only will shrinkage and porosity be difficult to remove, but concentrated shrinkage cavities will also occur, which will also reduce the process yield.
(8) Both the tilted placement of the mold and alloying will benefit. Eliminating shrinkage and porosity defects in machine tool castings is a complex understanding and implementation process. "Thermal balance" should be used as the basic principle to scientifically analyze the castings, formulate a reasonable process plan, select appropriate molding materials, tooling, and operate correctly and standardize. Then the shrinkage and porosity defects of any machine tool castings can be solved.
Due to the influence of many factors, defects such as pores, pinholes, slag inclusions, cracks, and pits often occur. Commonly used repair equipment is argon arc welding machine, resistance welding machine, cold welding machine, etc. Casting defects that do not require high quality and appearance can be repaired with high-heat, fast welding machines such as argon arc welding machines. However, in the field of repairing defects in precision castings, due to the strong influence of argon welding heat, repairs may cause deformation of the casting, reduced hardness, blisters, local annealing, cracking, pinholes, wear, scratches, undercuts, or insufficient bonding force and internal defects. Secondary defects such as stress damage. The cold welding machine just overcomes the above shortcomings. Its main advantages are that the heat affected area is small, the casting does not need to be preheated, and cold welding is repaired at room temperature, so there is no deformation, undercut and residual stress, no local annealing, and no change in the metal of the casting. Organization status. Therefore, the cold welding machine is suitable for repairing surface defects of precision castings. The repair range of cold welding is Φ1.5-Φ1.2mm, a process of repeated melting and accumulation of welding repair points. In the process of repairing large-area defects, repair efficiency is the only factor restricting its widespread application. For large defects, the combined application of traditional welding repair technology and casting defect repair machines is recommended. But sometimes we don't have many defects, so we don't need to invest a lot of money. We can repair them with some repair agents, which is convenient and simple. For example, for iron materials, we can use (Jinsucheng) JS902 to repair them. If it is not used up, you can put it away for later use. This can save costs for our manufacturers, allow our foundry manufacturers to invest more funds in improving the quality of the products themselves, and allow users to create more wealth.