A roasting method for promoting the removal of mold residual carbon

Abstract

The invention discloses a roasting method for promoting removal of residual carbon from a casting mould. The roasting method comprises the following steps that (a) the casting mould subjected to dewaxing is placed on a bracket device in an inverted mode, a roasting program of a furnace body, a working mode of a rotating device and a working mode of an air blowing device are set on a control panel,and the roasting program of the furnace body and the working mode of the rotating device which are set on the control panel are started; (b) when the casting mould is roasted to 530-580 DEG C, the working mode of the air blowing device set on the control panel is started, the air blowing device is used for continuously and directionally conveying oxygen-enriched air to a mould cavity of the casting mould for 30-60 minutes, and the air blowing device continuously performs dust blowing operation on the casting mould for 3-5 minutes; (c) when the roasting temperature of the casting mould is raised to 700-720 DEG C, the casting mould is kept the temperature for 2-3 hours, and the temperature is adjusted to the required one according to the structural characteristics of the casting mould; and(d) the working mode of the rotating device is changed so as to change the rotating state of the bracket device. According to the roasting method for promoting removal of the residual carbon from thecasting mould, roasting of the casting mould can be thorough, and harmful influences of the residual carbon on the casting quality can be eliminated.

Description

technical field [0001] The invention specifically relates to a roasting method for promoting the removal of residual carbon in a mold. Background technique [0002] At present, gold, silver, and copper jewelry are mainly produced by gypsum lost-wax casting process. The basic process is: making wax molds --- planting wax trees --- making plaster molds --- melting metal materials --- pouring - Clean up. Among them, the production of gypsum casting is a very critical process in the whole process, which mainly includes the following links: mixing gypsum slurry, pouring the slurry into the casting cylinder, standing the casting cylinder to make the gypsum slurry solidify and strengthen, casting The mold is put into the steam furnace for steam dewaxing or directly put into the roasting furnace for roasting and dewaxing, the mold is put into the roasting furnace for roasting, and the mold is adjusted to the required temperature for casting. The task of mold making is to clearly a...

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Problems solved by technology

[0004] (2) When oxygen is dissolved in the molten metal or copper oxide appears, carbon will react with oxygen or copper oxide after pouring to form CO or CO 2 Gas, sometimes when the reaction is particularly violent, can cause local instantaneous micro-explosions, resulting in pores or trachoma defects in castings

[0005] (3) The existence of residual carbon pollutes the molten metal, deteriorates its recycling performance, and makes casting production fall into a vicious circle

However, there are defects in the structural design of the existing mold roasting furnace, and the effect in eliminating the residual carbon of the mold is not good.

In terms of the structure of the gating system, the connection method of castings--inner runner--sprue--gate cup is adopted. There is no special exhaust system, which is not conducive to the furnace gas entering the mold during roasting. cavity, which is not conducive to the exhaust in the mold during pouring

In terms of the structure of the roasting furnace, most of the roasting furnaces are ordinary box-type resistance furnaces, and the temperature uniformity in the furnace is poor. The molds near the furnace door and in the center of the furnace often have residual carbon problems due to insufficient roasting, which further increases The temperature will cause the risk of burning other parts of the mold

In addition, when placing the mold, two layers are generally placed, the upper mold is directly pressed on the top surface of the lower mold, and the air convection is poor.

In order to improve and reduce the residual carbon in the mold, it is necessary to extend the roasting time in the high temperature stage, which not only increases energy consumption, but also reduces production efficiency, and the effect is not good

Some enterprises half-open the furnace door to introduce fresh air into the furnace when roasting to a high temperature, but the effect of this approach is also limited, because fresh air is not easy to enter the mold cavity, and the oxygen concentration in the air is low. Therefore, the combustion-supporting effect on the residual carbon in the cavity is not good. On the contrary, the open furnace door aggravates the unevenness of the temperature in the furnace, and the resistance wire in the furnace is easy to oxidize, which shortens the service life.

Sometimes in production, in order to improve the quality of mold roasting, the mold that has been roasted to a high temperature is taken out of the furnace, and the mold cavity is sucked with a vacuum cleaner to reduce the residual carbon and ash in the cavity, but this method There are typical problems, firstly, when the high-temperature mold is taken out and placed in the air for suction operation, it is easy to cause rapid cooling of the mold and uneven temperature, causing shrinkage stress in the mold to cause cracking, and secondly, it is easy to be damaged during suction The surface of the sprue cup is prone to sand hole defects during pouring

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