Precision investment casting water glass binder shell CO2 gas hardening technology

Abstract

The invention relates to a precision investment casting water glass binder shell CO2 gas hardening technology which comprises the following steps of: (1) placing a shell to be hardened in a fully-sealed hardening chamber; (2) starting a vacuum pump to keep the sealed chamber in a vacuum state; (3) introducing CO2 gas into the hardening chamber and starting a fast dehumidifying system so that a coating layer on the shell surface is subjected to chemical reaction and physical dehydration effect together with the CO2 gas to finish the hardening of the shell; and (4) closing a CO2 gas inlet valve and starting a sucking pump to suck the CO2 in the hardening chamber back to a storage tank for circular use. Compared with the traditional technology, the technology provided by the invention has the advantages: 1, the hardening operation environment is good, harmful substances are not discharged in roasting, and thus the technology is an environmentally-friendly production technology; 2, the hardening effect is good, and the phenomenon of halfway hardening of the shell is avoided; and 3, the consumption of CO2 gas is low, and the material cost of the shell hardening agent is reduced.

Description

Technical field [0001] The invention belongs to the technical field of investment precision casting, and relates to a hardening method for investment casting water glass binder shells, and specifically is a investment precision casting water glass binder shell CO 2 Gas hardening process. Background technique [0002] In the production of investment precision casting, when water glass is used as a binder to make the shell, the hardening process must be used to obtain the wet strength of the shell. The hardening effect of the shell affects the quality and production efficiency of the product, which is very important in this process. And key processes. When the sodium silicate investment casting process was introduced to China in the late 1950s, 20% ammonium chloride aqueous solution was used as the hardener. In the 1970s, my country developed crystalline aluminum chloride and polyaluminum chloride. As hardeners for aqueous solutions such as magnesium chloride, calcium chloride, etc...

AI Technical Summary

Problems solved by technology

When saturated ammonium chloride aqueous solution is used as the hardening agent, the hardening reaction will precipitate a large amount of NH from the hardening tank 3 Ammonia gas destroys the air environment in the shell workshop and makes it unbearable for operators; when crystalline aluminum chloride aqueous solution is used as a hardening agent, although no ammonia gas is precipitated, the acidity of the solution is very high, and the pH value reaches 1.5 to 2 , the volatilized gas in the hardening tank will continuously corrode the metal components in the workshop, the workers are constantly exposed to the acid hardening solution during operation, and the hardening agent dripping on the ground is continuously discharged, etc., which are harmful

[0017] 2. Harmful emissions will be produced during shell roasting

The hardening of the shell is carried out by soaking in the hardening agent. When the hardening reaction process of shell making is completed, the hardening reaction products and many hardeners, namely chloride salts, will remain in the shell. When the shell is dewaxed, it enters the roasting furnace When roasting, the roasting temperature reaches 900°C. At this time, a large amount of chlorine salt will volatilize from the shell, which will seriously corrode the heating element in the furnace. When it escapes from the furnace, it will also damage the workshop environment. If it is discharged into the atmosphere from the chimney, its Chloride will seriously exceed the discharge standard, and cumbersome treatment must be carried out to achieve safe discharge

[0018] Therefore, although the investment casting water glass binder precision casting process is an advanced casting forming process, if the shell making process does not fundamentally innovate the hardener and hardening method, it will hinder the wide application of this process.

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