Methods and technological problems of improving the quality of stainless steel precision casting

Stainless steel precision casting first makes the electrode of the required blank, and then uses the electrode corrosion mold to form a cavity. Then cast wax by casting method to obtain the original wax mold. Brush the wax mold with high temperature resistant liquid sand layer by layer. After the stainless steel precision casting obtains sufficient thickness, it is dried, and then heated to melt the internal wax mold and obtain the cavity consistent with the required blank. Then the molten iron is cast in the mold cavity, and the shell is stripped off after curing, so as to obtain the finished product of precision manufacturing.

Stainless steel precision casting process is simply to use fusible materials. The product can be made into fusible model, which is coated with several layers of special refractory coatings. After hardening and drying to form an integral mold shell, the model is melted from the mold shell with hot water or steam. The dimensional accuracy of stainless steel precision casting is high, and the process of investment casting of products is complex. In this way, there are many factors that directly affect the dimensional accuracy of castings, such as the linear change of mold shell in the process of heating and cooling, the shrinkage rate of alloy and the deformation of castings in the process of solidification.

Casting Manifold

 I Methods to improve the quality of stainless steel precision casting:

1. Process planning: strictly control the process. Before closing the box, ensure that the appearance and sand core are in a warm state. During pouring, ensure the fluidity of liquid steel. For places with rough and damaged appearance, use alcohol-based zircon powder coating for brushing and ignition baking to lubricate the appearance of the mold.

2. Mold planning: the surface treatment list of stainless steel castings starts from the mold, and the surface of the mold is cleaned, that is, the surface is wiped with sandpaper and brushed with nitro paint. For castings with high precision, metal or plastic molds are selected to improve the surface smoothness of the mold.

3. Fillet planning: in order to avoid white mouth during stainless steel forging, in addition to adopting technical measures, it is necessary to make the wall thickness not too thin. When the wall thickness is more than 15mm, the fillet is selected at the corner of the casting forged with metal mold;

4. Wall thickness planning: due to the rapid heat dissipation of metal mold, the small wall thickness of stainless steel forging should be larger than that of sand mold forging castings, and various forging alloys Forging small wall thickness of different sizes;

5. Polishing plan: remove the flash and burr during the polishing process, and polish the uneven part of the external surface to avoid excessive lubrication. The castings after heat treatment shall be polished and polished. The particle size of steel shot is 0.85 ~ 1.4mm, the hardness is HRC40-50, and the large hardness error is ± HRC3 0

6. Material planning: raw materials are used. Zirconium sand resin sand is used for appearance and core making. The mesh number is 75-150. Thermosetting resin is selected. The mixed and rolled sand has high fire resistance, smooth appearance, good collapsibility and simple sand falling.

 Stainless Steel Elbow

II Problems of stainless steel precision casting shell making process:

1. Because the water glass adhesive is retained in the back layer, the overall high temperature strength of the shell The creep resistance is lower than that of silica sol shell, and the dimensional accuracy and shape and position tolerance of cast castings are lower than that of silica sol shell.

2. The air permeability is not as good as that of sodium silicate shell or silica sol shell. The high temperature strength of the shell is not as good as that of silica sol shell, which is easy to cause waste.

3. The quality stability of composite shell casting is better than that of sodium silicate, but it is far less than that of silica sol shell.

4. The composite shell cannot use medium temperature wax. Medium temperature wax cannot be dewaxed with hot water.

5. The cost of composite shell is 4.5 times higher than that of sodium silicate shell because the expensive zircon powder is used as the surface layer. If the back layer adopts mullite sand powder, the cost of composite shell is almost the same as that of silica sol shell, and its advantage of low cost is not obvious.

 

The alloy shrinkage of stainless steel precision casting and the deformation of its castings in the process of stainless steel precision casting. Although the dimensional accuracy of ordinary investment castings is relatively high, it still needs to be improved in order to achieve consistency. The casting size and surface quality of stainless steel precision casting are higher than other casting methods, and are more complex than other casting methods. The castings that are resistant to high temperature and not easy to process in the process of use can be directly cast by investment casting.

Discussion with engineer

Hebei Junya Precision Machinery Co., Ltd., founded in 2017, is a high-tech enterprise integrating product design, mold development, casting, processing, surface treatment, testing and inspection and sales services. The factory covers an area of 5000 square meters and is located in Huanghua economic and Technological Development Zone, Hebei Province. The company has superior geographical location and convenient transportation. After years of development, the company has introduced advanced production equipment and management experience in various industries, and trained dozens of excellent professional R & D and technical talents.

At present, the company has more than 100 employees and more than 20 technical and R & D personnel. The company’s main products are stainless steel cast pipe fittings, quick connectors, ball valves, check valves, precision accessories, marine hardware, cast auto parts, etc. The product material is mainly 304 304L 316 316L CF8M WCB 1.4408, etc. The company officially passed ISO9000 certification in 2020 and is actively preparing for TS16949 quality system certification. With its good product quality and reputation, the company has become more and more prominent in the international market, with partners all over the world.

In 2020, the export volume accounted for more than 70% of the total sales, and has established long-term and stable cooperative relations with many enterprises in Europe, the United States and Japan. The company always adheres to the business philosophy of heart, innovation and ingenuity. Based on the principle of seeking development from R & D, meeting opportunities in development, building trust in opportunities and consolidating contacts in trust, we look forward to cooperating with you. For details, please contact 18902146089.


Post time: May-07-2022