Heat balance is the most fundamental point to solve the shrinkage defect of the casting in the support casting factory. The method is as follows:
(1) The bracket casting is customized at the thickness hot spot formed by the casting structure of the machine tool, the rapid solidification is carried out, which artificially causes the basic balance of the temperature field of all parts of the machine tool casting. Internal external cold iron is used, staggered quartz sand with large heat storage capacity, chromite sand special coating are used locally.
(2) Reasonable process design. The inner sprue is located at the relative thin wall of the machine tool casting, which is more more scattered in several hours. The first liquid metal entering the thick wall solidifies first, the thin wall solidifies later, so that all parts basically reach equilibrium solidification. For machine tool castings with uniform wall thickness, multiple internal sprues air outlets are used. There are many internal sprues, which are distributed distributed evenly, so that the whole heat is balanced. The air outlet hole is thin many, which means the exhaust is unobstructed plays the role of heat dissipation.
(3) Changing the position of the sprue
(4) It is very important to use EPC to produce anti-wear products! If chromite sand is used instead of quartz sand other sand with small heat storage, good results will be obtained, microseism is better after pouring!
(5) Low temperature fast firing, open gating system. Make the liquid metal fill the mold quickly, stably evenly. It depends on the circumstances.
(6) The machine tool mould of nodular cast iron has large strength, surface hardness ≥ 90, large rigidity of sand box, which is beneficial to eliminate shrinkage porosity.
(7) When a riser is required, the hot riser is moved first leaves the hot junction. If the riser is placed on the hot spot, the riser size will be increased to form "hot heating". If , only the shrinkage porosity is difficult to remove, but also the concentrated shrinkage cavity will be produced, the process yield will be reduced.
(8) The inclined placement alloying of the mold all benefit. It is a complex process to eliminate the shrinkage defects of machine tool castings. Based on the principle of "heat balance", we should make a scientific analysis of the female castings, work out a reasonable process plan, appropriate molding materials, tooling, correct operation standardization. Then any shrinkage defect of machine tool casting can be solved.
Due to the influence of many factors, defects such as pores, pinholes, slag inclusions, cracks pits often appear. The commonly used repair equipment is argon arc welding machine, resistance welding machine, cold welding machine, etc. For casting defects with low quality appearance requirements, the welding machine with high heat output high speed can be used to repair. However, in the field of precision casting defect repair, due to the great influence of argon welding heat, secondary defects such as casting deformation, hardness reduction, sand hole, local annealing, cracking, pinhole, wear, scratch, undercut, insufficient binding force internal stress damage will be caused during repair. The cold welding machine just overcomes the above shortcomings. Its advantages mainly lie in the small heat affected area, the casting does need preheating, cold welding repair at room temperature, so there is no deformation, undercut residual stress, local annealing will occur, the metal structure state of the casting will be changed. Therefore, cold welding machine is suitable for repairing surface defects of precision castings. The repair range of cold welding is 1.5-1.2mm, which is the process of repeated melting accumulation. In the process of repairing large area defects, the repair efficiency is the only factor restricting its wide application. For large defects, the composite application of traditional welding repair process casting defect repair machine is recommended. But sometimes we don't have a lot of defects, so we don't need to invest a lot of cost. We can repair them with some repairing agents, which is convenient simple. For example, for iron materials, we can repair them with js902, use them later if they can't be used up, so that we can save costs for our manufacturers, let our foundry manufacturers put more resources Gold is invested in improving the quality of products making users create more wealth.