Nowadays, the precision casting industry is developing very rapidly in today's society. Of course, it is inseparable from the advantages of precision castings, such as: high dimensional accuracy, small surface roughness, suitable for castings with complex structures and shapes, etc. It is agreed that our designers are inseparable, and precision casting has design principles:

1. Fair wall thickness. Under the condition that the wall thickness of the casting is smaller, it should be as thin as possible, which can not only ensure that the molten metal has good mobility, but also avoid casting defects (such as shrinkage holes) caused by excessive shrinkage.

2. Uniform wall thickness. Means that the cooling rate of the wall thickness of each part is uniform. The inner partition wall is thin, and the surrounding walls should be thick. Purpose: reduce stress, deformation and cracking; prevent shrinkage holes in hot joints.

3. Transitional connection. Structural fillet: avoid the formation of hot joints; improve stress distribution; avoid sand damage and blisters. Uniform transfer: When the walls or ribs in different directions on the casting are transferred, avoid metal gathering (hot spots) and shrinkage holes. Use rounded corners, inclined planes, and cones for gradual transition. Purpose: to prevent stress concentration and cracking.

Fourth, the big plane is tilted. Purpose: Use filling and exhaust to check.

5. Reduce deformation. (Same as heat treatment) Symmetrical structure and additional reinforcement ribs.

Sixth, free contraction. Purpose: It is beneficial to reduce stress cracking and deformation caused by shrinkage stress.

The greater advantage of silica sol casting is that due to the high dimensional accuracy and surface finish of investment castings, the machining work can be reduced, but only a small amount of machining allowance can be left on the parts with higher requirements, even some castings Only the grinding and polishing allowance is left, and it can be used without mechanical processing. It can be seen that the use of investment casting methods can save a lot of machine tool equipment and processing man-hours, and greatly save metal raw materials.


The production process of silica sol precision casting is actually very complicated. First of all, the processing materials of silica sol precision casting must be clean, and must not be mixed with wood chips, grass chips, sand, iron filings and other sundries during use. The furnace lining must be tamped. , And the compactness is uniform. The newly built furnace lining must be sintered according to the process requirements and can be used after the sintering is completed.

A common problem encountered in the use of silica sol precision casting is that there are pores inside the product. For some parts with higher requirements, the pores inside the product are not allowed, so silica sol precision casting Porosity needs to be prevented during processing.

When silica sol precision casting is faced with relatively complex thin-walled castings, in order to effectively improve the air permeability of its precision casting shells, the vent holes can be effectively set directly higher during the processing, and the pouring should be set reasonably system.

In this way, silica sol precision casting can effectively prevent its pouring entrainment, which can facilitate the discharge of gas in the cavity. During the pouring process, the pouring temperature can be appropriately increased, and the distance of the pouring ladle nozzle can be kept as low as possible. The pouring speed also needs to be reduced.

Precision casting is now a very important processing technology, and its processing is inseparable from precision casting. However, we need to determine the pouring surface when pouring, so how to determine this position?

1. The important processing surface or the main processing surface of the precision casting is facing down or on the side: during pouring, the gas, slag in the molten metal and the sand in the mold will float up, which may cause pores, slag inclusion, and slag in the upper part of the casting. Defects such as blisters, and the possibility of defects in the lower part of the casting, the structure is denser.

a. The pouring position of the machine bed should have the guide rail face down to ensure the quality of this important working surface. The quality of the circumferential surface is relatively high, and the vertical pouring scheme can be used to make the circumferential surface on the side to ensure uniform quality.

2. The large plane of the precision casting is poured downward or inclined: due to the strong heat radiation of the hot molten metal to the upper part of the mold during pouring, the top surface of the sand mold will expand and arch or even crack, causing sand inclusions, sand holes, etc. on the large surface. defect. The large plane facing down or the method of inclined pouring can avoid the production casting defects of the large plane.

3. The thin wall of the precision casting is facing downwards, standing on the side or inclined: In order to prevent the thin wall of the casting from producing cold barriers and failing to pour defects, the thin wall with a larger area should be placed in the lower part of the casting, or placed on the side wall or Tilt position.

4. Most of the thickness of precision castings should be placed on the top or on the side of the parting surface. The main purpose is to facilitate the placement of risers in thick areas for feeding.

Stainless steel precision casting has good fluidity to a certain extent. Due to its small transition zone size, stainless steel precision casting has good mechanical properties during use, which can meet its fluidity to a certain extent and does not form bright crystals. Normal temperature It is 715~740℃. Stainless steel precision casting flat ingots have a high tendency of hot cracking, and the temperature of stainless steel precision casting is relatively low, generally at 680~735℃. In addition to temperature, you also need to pay attention to the following operations:

First, make the electrode of the required blank, and then use the electrode to corrode the mold body to form a cavity. Then use the casting method to cast wax to obtain the original wax mold. Brush the wax pattern with high temperature resistant liquid sand layer by layer. After the stainless steel precision casting has obtained a sufficient thickness, it is air-dried, and then heated to melt the internal wax mold and obtain a cavity consistent with the required blank. Then cast molten iron in the cavity, and peel off the shell after solidification to obtain a precision-manufactured finished product.

The precision steel casting process comes from silica sol casting. It has a complete set of advanced equipment and material composition detectors. The castings have high dimensional accuracy and good surface finish, which can avoid the reduction of mechanical processing and save materials and processing costs. Cooling during processing is a very important process:

1. When alloy steel castings are air-cooled, they should be scattered in a dry place;

2. After the workpiece is quenched, it should be tempered in time. The time interval should generally not exceed 4h. The carbon content (mass fraction of carbon) in the alloy steel castings used for the workpiece is low, and the shape of the workpiece is simple, and should not exceed 16h;

3. It can be cleaned, cryogenically treated or tempered after cooling to room temperature;

4. For welding assemblies composed of alloy steel castings, the time interval between welding and subsequent heat treatment should not exceed 4h.