Precision casting: the process of precision casting

Precision castings include precision castings, precision carbon steel castings and precision stainless steel castings. Heat treatment of precision castings Due to the different uses of precision castings, there are many heat treatments, which can be basically divided into two categories. One is that the microstructure does not change or should not be changed after heat treatment, and the other is that the basic microstructure will change. The heat treatment procedure is mainly used to eliminate the internal stress, which is caused by the different cooling conditions and conditions in the stainless steel casting process. Microstructure, strength and other mechanical properties, etc. No significant change due to heat treatment. For the second heat treatment, the base organization has undergone significant changes, which can be roughly divided into five categories: 1. Softening annealing: its main purpose is to decompose carbides, reduce its hardness and improve its workability. For ductile iron, the purpose is to obtain more ferrite structure. 2. Normalizing: The main purpose is to obtain pearlite and sorbite structure and improve the mechanical properties of stainless steel castings. 3. Quenching treatment: mainly to obtain higher hardness or wear strength, and at the same time to achieve very high surface wear resistance. 4. Surface hardening treatment: mainly to obtain surface hardening layer and high surface wear resistance. 5. Precipitation hardening treatment: The main reason is to obtain high strength without drastic changes in elongation. Manufacturing process of precision castings; ①Process design Design molds or drawings according to samples, and use CAE simulation casting software to design casting systems. Modeling: Make 3D models of products according to samples or drawings, and use this 3D drawings to make aluminum or steel molds. Wax injection: Mix the liquid wax and solid wax into a paste wax paste, inject the wax paste into the metal mold with a wax injection gun, and take out the wax mold after cooling. ②Loading wax: heat the stainless steel welding knife, and weld the wax mold on the door pole according to the requirements of the process design. ③Paste: Dip the wax sheet group into a can containing water glass and other paint, and apply the paint. 4. Sandblasting: Spray quartz sand on the wax coated with paint, then immerse it in a hardening tank filled with ammonium chloride, magnesium chloride and other materials, then dry, and then proceed to the next layer of operation. This process is repeated about 6 times to complete. ⑤ Dewaxing: Put the hardened wax group on the surface coating into a lost wax tank, heat it with steam, so that the wax dissolves and peels off, leaving a sand shell. Bake Template: Put the precision casting template in the oven to increase its strength. ⑥ Pouring: Melt the raw materials in the intermediate frequency electric furnace, add metal elements, and raise the temperature of the molten steel to about 1600 ° C. After the chemical analysis before the furnace is qualified, pour the molten steel into the mold shell through the ladle, fill the mold cavity with the molten steel, cool it, and then pour the molten steel into the mold shell. Sampling inspection after release. ⑦ Shelling: Vibration to remove the sand on the surface of the casting. ⑧ Cutting: The casting is cut from the casting rod with an oxygen-acetylene flame. ⑨ Grinding: Grind the pouring riser with a grinder; grind the damaged surface with a grinder. Heat treatment: The castings are subjected to heat treatment such as normalizing, annealing, quenching and tempering, induction hardening, carburizing, and nitriding according to material requirements. ⑩Precision casting processing: According to the requirements of the drawings, use CNC machine tools for metal processing. Precision casting inspection: use tensile testing machine, impact testing machine, hardness tester and other testing equipment to test the mechanical properties of the test bar; use X-ray, ultrasonic, magnetic particle testing and other testing equipment to perform non-destructive testing on samples; use three coordinates, measuring tools, calipers, etc. The inspection tool performs dimensional inspection of the product.