Factors affecting dimensional accuracy of precision castings

In general, the dimensional accuracy of precision castings is affected by many factors, such as casting structure, casting material, mold making, shell making, roasting, pouring and so on. Unreasonable setting and operation of any link will change the shrinkage rate of castings, resulting in deviation between the dimensional accuracy of castings and the requirements. The following factors can cause the accuracy of precision castings:

(1) Influence of casting structure: A. casting wall thickness, large shrinkage, thin casting wall and small shrinkage. b. Large free shrinkage and small hindered shrinkage.

(2) Influence of casting material: a. the higher the carbon content in the material, the smaller the linear shrinkage, and the lower the carbon content, the greater the linear shrinkage. b. The casting shrinkage of common materials is as follows: casting shrinkage k = (lm-lj) / LJ × 100%, LM is the cavity size and LJ is the casting size. K is affected by the following factors: wax mold K1, casting structure K2, alloy type K3 and pouring temperature K4.

Wax injection workshop

(3) The influence of mold making on the linear shrinkage of castings: a. the wax injection temperature, wax injection pressure and pressure holding time have the most obvious influence on the investment mold size, followed by the wax injection pressure. The pressure holding time has little influence on the final size of the investment mold after ensuring the investment mold molding. b. The linear shrinkage of wax (mold) is about 0.9-1.1%. c. When the investment mold is stored, it will further shrink, and its shrinkage value is about 10% of the total shrinkage, but after 12 hours of storage, the investment mold size is basically stable. d. The radial shrinkage of wax mold is only 30-40% of the shrinkage in the length direction. The influence of wax injection temperature on the free shrinkage is much greater than that on the hindered shrinkage (the best wax injection temperature is 57-59 ℃. The higher the temperature, the greater the shrinkage).

(4) Influence of shell making materials: Zircon sand, zircon powder, Shangdian sand and Shangdian powder are used. Because their expansion coefficient is small, it is only 4.6 × 10-6 / ℃, so it can be ignored.

(5) Influence of shell roasting: due to the small expansion coefficient of shell, when the shell temperature is 1150 ℃, it is only 0.053%, so it can also be ignored.

(6) Influence of pouring temperature: the higher the pouring temperature is, the greater the shrinkage is. The lower the pouring temperature is, the smaller the shrinkage is. Therefore, the pouring temperature should be appropriate.

Factory from long range

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 18902146189.


Post time: May-07-2022