A low-pressure investment casting process

Abstract

The invention discloses a low-pressure fusible mold precise casting process. Sand boxes are laminated on a shaping steel plate; a combined shell is positioned in a center hole of the shaping steel plate; a gap is plugged by an asbestos rope; clay sand is adopted to fix at the outer periphery of a sprue cup; the sand boxes are fully filled and flatly scraped by dry sand; the shaping steel plate is lifted and placed on a lifting steel plate for fixing; the lifting steel plate is lifted and fixed on a low-pressure casting machine worktable; a pressing steel plate covers the top of the sand boxes for pressing; an insulation furnace is pushed to a working position for hoisting until an upper port of a liquid rising pipe and a lower port of a sprue cup shell are in butt joint for realizing sealing; compressed gas is led in a gas-phase space of the insulation furnace; molten metal at the bottom of the insulation furnace ascends along with the liquid rising pipe to enter a cavity of the combined shell; the molten metal in a thin-wall product cavity is condensed under pressure for gas release, and flows back; and then, the shifting, the pressing, the lifting and the sand falling are performed. The process molds thin-wall products at high temperature, and is low in cost, high in efficiency and few in defects.

Description

technical field [0001] The invention relates to a casting process, in particular to a low-pressure investment precision casting process, which belongs to the technical field of metal casting. Background technique [0002] Investment casting is also known as lost wax casting. The production process of lost wax casting is to coat several layers of refractory material on the surface of the wax mold. After it is hardened and dried, the wax mold is melted to form a shell, and then baked to shape. , and then pouring, and castings are obtained after cooling. Since the obtained castings have high dimensional accuracy and surface finish, it is also called investment precision casting. [0003] Low-pressure casting is a method of filling the cavity with liquid metal under pressure to form a casting. The process of low-pressure casting is as follows: dry compressed air is introduced into the closed holding furnace, and the molten metal in the holding furnace rises along the liquid ri...

AI Technical Summary

Problems solved by technology

However, this method has the following disadvantages: (1) Generally, investment casting shells are poured at a higher temperature of the shell itself, so that the filling of the thin-walled shell can be ensured.

(2) This process needs to consume a large amount of resin sand, and the price of resin sand is relatively expensive, which increases the production cost

(3) It takes a long time for resin sand to solidify, which affects production efficiency

⑷When the alloy liquid passes through the resin sand, the resin will be heated, and a large amount of gas will be generated. After the gas enters the cavity, part of it will not be discharged in time and enter the casting, resulting in the formation of pore defects in the casting.

(5) Long-term baking of the resin sand near the gate will easily consume the resin and lead to the collapse of the molding sand. The collapsed molding sand will enter the low-pressure casting holding furnace through the riser pipe. When pouring again, the molding sand in the furnace will enter the subsequent pouring Inside the casting, there are defects such as sand holes in the casting

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