Casting process of a ductile iron box casting

Abstract

The invention discloses a casting technology for a ductile iron box body. The casting technology comprises the following steps: coated sand preparation, outer mold and mud core manufacturing, mold closing, smelting, pouring and sand cleaning, wherein mold closing is to close an outer mold and a mud core to form a sand mold, lock the sand mold in a sand box by a locking device and fill a cavity between the sand box and the sand mold with steel shots until the steel shots completely cover the sand mold. According to the casting technology, the steel shots filled between the sand box and the sand mold apply pressure to the sand mold by utilizing the self weight, thus the phenomena of deformation and thermal expansion generated in the pouring resistance process of the sand mold are effectively prevented; the heat transmission coefficient of the steel shots is large, and molten iron in a cast can be rapidly cooled, thus the tendencies of the cast of shrinkage porosity and shrinkage cavity are reduced; meanwhile, the steel shots also have the thermal insulation action in an interval between the sand box and the sand mold, and the cast cannot have the chill structure phenomenon due to too fast cooling speed, thus the qualified rate of the cast is greatly increased; and as the steel shots can be repeatedly used, the production cost can be greatly lowered.

Description

technical field [0001] The invention belongs to the technical field of casting technology of ductile iron box castings, and in particular relates to a casting process of ductile iron box castings with complex structures and large wall thickness differences. Background technique [0002] Ductile iron box castings generally have a relatively complex box structure. For box structures that do not require high surface quality, sand molds are usually made by resin sand molding technology, and then cast by one mold with multiple pieces. For high surface quality requirements, For castings that need to withstand high pressure, it is not allowed to repair any defects such as shrinkage porosity, shrinkage cavity and white hole. This kind of ductile iron box castings must be produced with fully coated sand, that is, both the shape and the core Coated sand production. [0003] The structure of the box body is complex, the wall thickness varies greatly, the wall thickness of the main bod...

AI Technical Summary

Problems solved by technology

[0003] The structure of the box body is complicated, the wall thickness varies greatly, the wall thickness of the main body is small (5mm), and the wall thickness of the part is large (up to 35mm or more). For such a box body casting, due to the large volume and light weight, the sand-iron ratio is large and the production cost is high. Increase

Some foundries add resin sand or green sand molds outside the coated sand mold to fix the coated sand mold, and at the same time, it is used to increase the thermal strength of the coated sand mold, reducing cracking or casting products during sand casting. Deformation; some foundries increase the heat resistance of the sand mold by adding coatings to the coated sand mold and the clay core, or increase the thickness of the coated sand sand mold to improve the thermal deformation resistance of the sand mold during the pouring process; some foundries directly Green sand casting is used, but due to the large difference in wall thickness, casting defects are difficult to solve, resulting in a high scrap rate

[0004] At present, the commonly used process is difficult to greatly improve the production efficiency, casting quality and production cost when producing box castings with complex structures and large wall thickness differences.