Process for producing nodular cast iron camshafts by means of iron-mold clamped sand molds

Abstract

The invention discloses a process for producing nodular cast iron camshafts by means of iron-mold clamped sand molds. A specialized iron mold for gray cast iron casting is adopted, and a specialized casting frame is manufactured, the specialized iron mold is placed on the specialized casting frame, and a double-side horizontal sand ejecting molding machine is used for producing coated sand molds;a ceramic filter sheet and a glass fiber filter screen are placed in each sand mold, and the left sand mold and the right sand mold are bonded into a complete sand mold; the sand molds are placed in the middle of the iron mold one by one, and the sand molds are accurately embedded into a cavity of the iron mold; and iron water subjected to the spheroidization treatment is poured according to eachsand mold, and then castings are separated. By adopting the process, the production efficiency is greatly improved, the process yield is greatly increased, and the process cost is reduced; the defectrates of product size, shrinkage porosity, bending, shrinkage holes, slag inclusion, air holes, sand holes, cold shuts, mismatches and box expansion are eliminated, the disqualification of the metallographic structure is avoided, and the disqualification of mechanical performance is avoided; and the energy conservation and emission reduction are realized, and the production cost is reduced.

Description

technical field [0001] The invention relates to a process for producing a nodular cast iron camshaft by clamping a sand mold with an iron mold, in particular to a casting process for a nodular cast iron camshaft of an automobile engine. Background technique [0002] The traditional nodular cast iron automobile camshaft casting process includes iron mold sand-covering process, shell mold buried steel shot process, shell mold process and wet clay sand process. The iron mold has a large investment and no flexibility, and cannot adapt to the production of small and medium batch products of various varieties. The casting residual stress is large, and stress relief annealing is required. The production cost is high. When the casting is cooled, the sand mold has no concession, and the product is easy to break or produce hidden cracks. If it is too thin, the heat absorption capacity of the iron mold is large, the molten iron cools quickly, it is easy to be cold shut, the shape is in...

AI Technical Summary

Problems solved by technology

[0002] The traditional nodular cast iron automobile camshaft casting process includes iron mold sand-covering process, shell mold buried steel shot process, shell mold process and wet clay sand process. The iron mold has a large investment and no flexibility, and cannot adapt to the production of small and medium batch products of various varieties. The casting residual stress is large, and stress relief annealing is required. The production cost is high. When the casting is cooled, the sand mold has no concession, and the product is easy to break or produce hidden cracks. If it is too thin, the heat absorption capacity of the iron mold is large, the molten iron cools quickly, it is easy to be cold shut, the shape is incomplete, the surface is easy to produce cementite, the metallographic structure is unqualified, it is difficult to process, the fluidity of the molten iron is poor, impurities are not easy to float, and slag inclusions are easy to occur , air holes, sand holes, cavity exhaust is not smooth, easy to produce air holes; the shell-type embedded steel shot process means that the shell mold is made and buried in the steel shot for pouring. The use of steel shot and the recovery system of this process require a lot of investment, and the process is complicated. The control is difficult, the labor intensity is high, and the operation is difficult. The overflowing molten iron is easy to stick to a large number of steel shots, the steel shot is worn out, the shell is thin, and the product is easy to bend. When the steel shot is separated from the molding sand, a large amount of dust is generated, causing air pollution; The shell molding process means that after the shell molding is made, it is poured directly on a flat surface. The shell molding is thick, the sand consumption is large, the riser is large, the process yield is low, the cooling is slow, the structure is coarse, the strength and elongation are low, and the molding sand is produced at high temperature. Phase change, easy cracking of the shell type, excessive length and size of the product, easy bending, poor shell rigidity, easy shrinkage of the product, poor air permeability of the sand mold, easy generation of pores, cold shut, large gas generation of the sand mold, causing air pollution; wet clay Sand process: The sand mold strength of this process is low, the length and dimension of the product are out of tolerance, easy to bend, the sand mold is easy to crack, the product is deformed, the shape is incomplete, the air permeability of the sand mold is poor, easy to produce air holes, cold shut, the local sand of the sand mold is easy to peel off, and sand holes are easy to occur , the surface is rough, sand mold positioning is difficult, easy to make mistakes and expand the box, the sand mold has a large heat absorption capacity, the molten iron cools quickly, it is easy to be cold, the shape is incomplete, the surface is easy to produce cementite, the metallographic structure is unqualified, difficult to process, molten iron Poor fluidity, impurities are not easy to float up, slag inclusions, air holes, sand holes are easy to occur, the technology is backward, and the product quality cannot be effectively controlled

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