KR20050048984A - Method for surface modification of castings by circular vibration infiltration - Google Patents

Abstract

Disclosed is a method for surface modification of castings by circular vibration infiltration. The method of the present invention comprises the steps of: preparing a mold comprising a burnout model, a granular alloying agent applied to the burnout model in all directions, a flask into which the burnout model is charged, and a dry yarn filled between the flask inner surface and the burnout model Wow; Injecting molten metal into the burnout model; It characterized by oscillating the mold injected with the molten metal. According to the present invention, since it is not necessary to pressurize the molten metal and inject the high temperature, and preheat the warming of the granular alloying agent, the process is easy, and problems such as increasing the casting thickness and the void ratio of the alloying agent coating layer are solved, which is practical. Is improved so that surface modification occurs over the entire surface of the casting.

Description

Method for surface modification of castings by circular vibration infiltration

The present invention relates to a method for surface modification of castings by original oscillation infiltration, and more particularly, to a method for surface modification of castings by original oscillation infiltration using vanishing model casting.

Although surface modification using a molten-mold reaction for modifying the casting surface by using the phenomenon that the coated alloy element is diffused into the molten metal has been noticed for a long time and many studies have been conducted, but its practical use is very few. This is because of the problem of reproducibility and high alloying due to unstable dispersion of alloying elements.

In order to solve this problem, a metal coating casting method using an infiltration method in a melt-molding reaction has been developed.

1A and 1B are schematic views for explaining a metal coating casting method in which the infiltration method is applied to a conventional melt-casting reaction.

Referring to FIG. 1A, a mold is formed using a furan resin or the like and has a hollow mold 11 having a cavity inside thereof, and a granular alloying agent applied to the inner wall of the hard mold 11. 12) is made. In the case of cast iron castings or cast steel castings, the granular alloying agent 912 is formed by mixing an aggregate such as a ferrochrome powder or a ferroboron powder with an alcohol solvent such as phenolic resin, cellulose, vinyl acetate, or the like, and a surface that is infiltrated. It consists of a granular metal forming a modified layer.

Referring to FIG. 1B, the burnout model 21 is adopted in place of the magnetic mold having the cavity shown in FIG. 1A, and the granular alloying agent 22 is applied to a predetermined region outside the burnt model 21. FIG.

In addition, there are a method of infiltration by a vertical uniaxial or horizontal uniaxial vibration and a method using a pressure infiltration.

However, in the case of the immersion method by uniaxial vibration, since the uniaxial linear vibration only vibrates in one direction, it is effective only on the surface modification of a specific part. Therefore, the infiltration effect is insignificant depending on the position of the granular alloying agent. . In the case of using the pressure immersion method, the preheat insulation device and the pressure casting device of the layer to be immersed need to be improved in order to improve the infiltration effect. Thus, the casting method shown in FIGS. 1A and 1B appears to be most useful at present.

On the other hand, in the combination of the granular alloying agent coating layer and the burnout model, in order to obtain a surface modification layer having a sufficient thickness, the molten metal must be injected at a temperature considerably higher than the normal injection temperature, and the casting thickness and the porosity of the alloying agent coating layer are greatly increased. Because of this, there are many difficult problems of lowering the size accuracy, lowering the product recovery rate and applying the alloying agent. Therefore, there is a need for the search for auxiliary means that can obtain practically excellent invasiveness.

Accordingly, the technical problem to be achieved by the present invention is to provide a method for surface modification of castings by circular vibration infiltration which can obtain practically excellent infiltration properties.

The surface modification method of the casting by the original oscillation infiltration according to the present invention for achieving the above technical problem is: a granular alloying agent comprising a loss model, aggregate and granular metal applied to the loss model in all directions; Providing a mold comprising a flask into which the disappearance model to which a granular alloying agent is applied is charged, and a dry yarn filled between the flask inner surface and the disappearance model to which the granular alloying agent is applied; Injecting molten metal into the disappearance model; And oscillating the mold into which the molten metal is injected.

Hereinafter, with reference to the accompanying Figure 2, a preferred embodiment of the present invention will be described in detail.

Figure 2 is a schematic diagram for explaining the surface modification method of the casting according to the present invention.

First, a loss model 110 is made of a polystyrene foam (EPS; Expandable Polystyrene) or polymethyl methacrylate (PMMA), which is a raw material such as styrofoam, and molded into the same shape as a casting product to be manufactured using a mold. . And the granular alloying agent 120 is apply | coated to the loss | disappearance model 110 in all directions. As described above, the granular alloying agent 120 includes an aggregate, a granular metal that is infiltrated to form a surface modification layer, and a caking additive. Next, the burnt-out model 11 to which the granular alloying agent 120 was applied was charged to the flask 130, and dried between the inner surface of the flask 130 and the burnt-out model 110 to which the granular alloying agent 120 was applied. The mold 100 is prepared by filling the 140.

Next, an unbalance weight type exciter (not shown) is installed in the mold 100.

Subsequently, when the molten metal is injected into the vanishing model 110, the vanishing model 110 is vaporized by the heat of the molten metal and discharged into the dry sand 140, and a casting having the same shape as the vanishing model 110 is cast. At this time, the granular alloying agent 120 applied omnidirectionally to the vanishing model 110 is infiltrated, that is, changed into a liquid phase by the molten metal, and the liquid metal penetrates through the gap between the aggregates. Form a surface modification layer. At this time, while casting is cast by the molten metal and the granular alloying agent is infiltrated, the imbalance induction shaker is operated to oscillate the mold into which the molten metal is injected.

When the molten metal is injected, the equilibrium condition equation of the pressure formed by the gas between the molten metal pressure, the surface tension of the molten metal and the granular alloying agent aggregate is represented by Equation 1 below.

Where d is the gap between aggregates of the granular alloying agent, h is the height of the melt, Is the density of the melt, g is the acceleration of gravity, P is the pressure formed by the gas between the granular alloying aggregate, and T is the surface tension of the melt.

Infiltration occurs well in Equation 1 when the value on the left side is greater than the value on the right side. That is, when the shape of the molten metal and the characteristics of the layer to be immersed (granulated alloying agent) are constant, the greater the molten metal, the better the infiltration occurs.

Thus, the unbalanced exciter vibrates the mold to increase the melt pressure. At this time, the vibration of the exciter is transmitted to the mold, but since the phase change and the damping of the vibration amount are transmitted to the molten metal, relative vibration occurs between the mold and the molten metal. As a result, the relative excitation force, that is, the difference between the excitation force of the mold and the And the equilibrium condition of Equation 1 is expressed by Equation 2 below.

Since the left side needs to be larger than the right side in order for the infiltration to occur well, the difference between the excitation force of the mold and the excitation force of the molten metal, which can be easily generated from Equation 2 Is expressed as in Equation 3.

That is, in the present invention, the temperature problem of the melt and the problem of the size of the casting thickness and the porosity of the alloying agent coating layer are solved by increasing the momentum by applying the original vibration to the melt rather than the uniaxial vibration. Then, by applying the granular alloying agent to the vanishing model in all directions and imparting a circular vibration, the effect of surface modification is generated on the entire surface of the casting, not just a specific part.

The unbalanced exciter can be given additional vibration if the two unbalanced weights are rotated in the same direction, and linear vibrations are given to the mold in different directions.

As described above, according to the present invention, by applying the original vibration to the molten metal to increase the momentum, it is not necessary to pressurize and inject the molten metal, and to preheat and insulate the granular alloying agent. Problems such as increasing the porosity are solved and practical.

In addition, the infiltration effect is enhanced to cause surface modification over the entire surface of the casting.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

1A and 1B are schematic views for explaining a metal coating casting method in which the infiltration method is applied to a conventional molten metal casting reaction;

Figure 2 is a schematic diagram for explaining the surface modification method of the casting according to the present invention.

Claims (4)

A flask comprising a burnout model, an aggregate and a granular metal, coated with a granular alloying agent applied to the vanishing model in all directions, a flask into which the burnt-out model with the granular alloying agent is applied, and the inner surface of the flask and the granular alloying agent are coated. Providing a mold comprising a dry yarn filled between the lost model; Injecting molten metal into the disappearance model; The surface modification method of the casting by the original oscillation infiltration, characterized in that for oscillating the mold in which the molten metal is injected. The method for surface modification of a casting by oscillation of a primary vibration according to claim 1, wherein an exciter is installed in the mold to oscillate. 3. The method of claim 2, wherein the excitation group is an unbalanced excitation excitation group. 4. The difference between the excitation force of the mold and the excitation force of the molten metal according to claim 2 or 3 The method of modifying the surface of the casting by the oscillating oscillation, characterized in that the mold is circular motion so that the following equation. (Mathematical formula) Where d is the gap between aggregates of the granular alloying agent, h is the height of the molten metal, Is the density of the melt, g is the acceleration of gravity, P is the pressure formed by the gas between the granular alloying aggregate, and T is the surface tension of the melt.