Stainless steel precision casting is a low-cut or no-cut casting process. It is an excellent process technology in the foundry industry and has a wide range of applications. Stainless steel precision casting or investment casting, silica sol process. It is a casting process with little or no cutting, and an excellent process technology in the foundry industry. It can be seen that the use of investment casting method can greatly save machine tool equipment and processing man-hours, and greatly save metal raw materials. Another advantage of the stainless steel precision casting method is that it can cast complex castings of various alloys, especially high-temperature alloy castings. For example, the blade of a jet engine, its streamlined profile and cooling cavity, can hardly be formed by machining technology. Production with investment casting process can not only achieve mass production, ensure the consistency of castings, but also avoid the stress concentration of residual knife marks after machining.
The main problems of the shell making process of stainless steel precision casting are as follows:
1. The quality stability of composite shell castings is worse than that of water glass, but far inferior to silica sol shell.
2. Mid-temperature wax cannot be used for composite shells. Medium temperature wax cannot be dewaxed with hot water.
3. Since the composite shell uses high-priced zircon powder as the surface layer, the shell cost is 4.5 times that of the water glass shell. If the back layer uses mullite sand powder, the cost of the shell is the same as that of the silica sol shell. There is little difference, and its low cost is not obvious.
4. Because the back layer retains the water glass binder, the overall high temperature strength and creep resistance of the shell are lower than that of the silica sol shell, and the dimensional accuracy and shape tolerance of the cast castings are not as good as the silica sol shell.
5. The air permeability is not as good as the water glass type shell and the silica sol type shell. The high temperature strength of the type shell is not as good as the silica sol type shell, which is easy to cause waste.
There is still room for improvement in stainless steel precision casting. We can refer to the following two aspects:
1. Improvement methods and cost optimization
Using fused silica or quartz powder instead of zircon powder can ensure product quality and effectively reduce costs; use quick-drying silica sol to make the shell to shorten the production cycle.
2. Existing problems
The cost of making the shell and the selected wax mold material is relatively high, the power consumption during production is large, and the equipment investment is also large, so the cost is high, and the production cycle is significantly longer than that of the water glass shell and the composite shell process.
Stainless steel precision casting is a very important casting process in the production and processing of stainless steel castings. If you do not pay attention to the processing details during the production process, it is easy to affect the product quality. Therefore, the stainless steel precision casting process should be mastered in certain details during operation to ensure the product quality.
1. In order to facilitate the removal of castings and draw-out molds, the casting gradient of stainless steel precision casting castings should be appropriately larger than that of sand castings, generally 30%-50% larger, and tend to be pressed against the metal mold when the casting shrinks. The surface of the casting should be given a larger slope.
2. Due to the fast heat dissipation of metal molds, the smaller wall thickness of stainless steel precision casting should be larger than that of sand casting castings. Various casting alloys and castings of different sizes have smaller wall thicknesses.
3. In order to prevent white holes during stainless steel precision casting, in addition to technological measures, the wall thickness must not be too thin. For aluminum alloy and magnesium alloy metal mold castings, the casting fillet should not be less than 3-4m.
4. The thickness of the inner wall and inner rib of stainless steel precision casting castings should generally be 0.6-0.7 of the thickness of the connected outer wall. Otherwise, because the inner wall (rib) cools slowly, cracks will occur at the junction of the inner and outer walls when the casting shrinks.
There are many types of castings, and the application fields are also very wide, not only involving mechanical products, but also very common in life. After casting production and processing, this step is generally carried out. So what are the commonly used correction methods?
The correction of castings is divided into free correction and mold correction, both of which are very commonly used. Among them, the correction is to place the casting on a flat plate or a special simple fetal membrane and beat it with a hammer until the size and shape meet the requirements. This correction method is mostly used in small and medium-sized pieces. If it is a large casting, it needs to be completed on the corresponding correction equipment, and must be equipped with a suitable correction mold, so it is also called mold correction. Before correcting, it is necessary to master the deformation law of the casting, and then place the casting in a molding die with matching size and shape, and use the selected pressure to correct the casting as a whole on the selected straightening machine. During the overall correction, use lifting equipment or manipulators to load or take out the castings into the correction mold to obtain high-precision castings.