JPH02224863A - Casting apparatus - Google Patents

Abstract

PURPOSE:To prevent involution of oxide in molten metal into a casting product and to obtain the casting product having high quality by setting a ceramic filter at intermediate part in a stoke and positioning the molten metal surface level in the stoke before and after casting to the same height as the upper surface of the filter. CONSTITUTION:The ceramic filter 21 is set to higher position in the stoke 5 than the molten metal surface level 23 in a holding furnace 24. At the time of returning back the molten metal in the stoke 5 to the holding furnace 24 after the casting completes, even if the molten metal surface level in the holding furnace 24 varies, the pressures at the holding furnace 24 side and a metallic mold side are controlled with a computer so that the molten metal surface 22 in the stoke 5 positions at almost the same height as the upper surface 22 of the filter. Then, the involution of the oxide returned to the stoke 5 at upper part from the filter 22, partially while sticking to inner wall of the stoke 5, into the molten metal is prevented.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention uses a pressure difference between the mold side and the furnace side to filter oxides and impurities from the molten metal when the molten metal in the furnace is poured into the mold. The present invention relates to a casting device that prevents entrainment into cast products and produces high-quality castings.

(Prior art) As a method to prevent oxides of molten metal from being involved in cast products, there is a method to prevent the oxides themselves from being generated in the furnace using an inert gas, or to prevent the oxides from being generated in the furnace as shown in A commonly used method is to install gold 1I425 in the sprue 26 of the stalk 20, or to install a filter 21 at the lower end of the stalk 20 as shown in FIG. 6 to capture oxides.

(Problems to be Solved by the Invention) A method of suppressing the generation of oxides by spraying an inert gas onto the surface of the molten metal in the stalk is a method for preventing the generation of oxides in the mold cavity. Although it is one of the effective means of preventing oxide entrainment, special equipment is required to recover the inert gas and spray it onto the hot metal surface, and although it is suitable for casting products with high added value, The drawback was that it was not compatible with general mass-produced castings that were relatively inexpensive. In addition, it is widely used to filter oxides by installing a wire mesh at the sprue of the mold cavity or by installing a filter at the lower end of the stalk. However, if the wire mesh is not properly installed, the wire mesh may get caught in the mold cavity along with the molten metal, resulting in a decrease in quality. In addition, the method of installing a filter at the lower end of the stalk is effective in filtering oxides from the molten metal in the holding furnace, but the oxides that are generated above the filter, especially those that adhere to the inner wall of the stalk, return to the stalk. The drawback was that it was not effective against molten metal mixed with.

(Means for Solving the Problems) The present invention solves the above-mentioned conventional drawbacks, prevents oxides of molten metal from being involved in cast products, and provides high-quality cast products. That is, a ceramic filter is installed at a position higher than the molten metal level in the furnace on the mold sprue side on the inner surface of the stalk of a casting device that casts the molten metal in the furnace into the mold through a stalk that communicates between the furnace and the mold. Equipped with a pressure control device that keeps the top surface of the ceramic filter and the molten metal level in the stalk almost the same before and after casting, even if the molten metal level changes in the holding furnace. In particular, this prevents the oxide of the molten metal that has adhered to the inner wall and then returned to the stalk from being drawn into the mold cavity. Further, the thickness of the stalk used is preferably 10 to 55 m, the diameter of the rolling hole ball is Φ1 to 8 mm, and the porosity is preferably 70% or more.

(Example) As shown in FIG. 2, the casting machine used in the present invention has molds 2 and 3 and a holding furnace 6 installed in pressure vessels 4 and 7, and the pressure between the front pressure vessels 4 and 7 is This is a casting device that uses the difference to cast the molten metal in the furnace 6 into the mold cavity 1 via the stalk 5 that communicates the furnace 6 and the mold 2. Third
After pressurizing the inside of the prepressure vessel to about 8.0 kgf/ad as shown in FIG. 4 using the pressure control device having the configuration shown in the figure, the mold side is linearly moved 7.0 kgf/ad for about 20 seconds. Okgf/a
Pressure is reduced to d and the pressure difference between the front pressure vessels 1. Using Okgf/-, molten metal was poured into the cavity of the mold from the holding furnace side through the stalk. At this time, as shown in Figure 1, the inside of the stalk had a thickness of 30 mm, a pore diameter of 5 mm, and a porosity of 8.
A 0% ceramic filter 21 was installed at a position higher than the molten metal surface 23 in the holding furnace 24. When the molten metal in the stoke 5 is returned to the holding furnace 24 after casting is completed, even if the molten metal surface in the holding furnace 24 changes, the height of the molten metal surface 22 in the stoke before and after casting is set to the top surface of the filter. The pressure on the holding furnace 24 side and the mold side was controlled by a computer so that the pressure was almost the same as that of the holding furnace 24 side, and the entrainment of oxides that had returned to the stalk 5 while adhering to the inner wall of the stalk 5 above the filter 22 was also prevented. It is something.

Fifty test pieces were cut from each of the products cast by the casting device of the present invention and those made by the conventional casting device with a wire mesh attached to the sprue of the cavity and a ceramic filter installed at the lower end of the stalk, and a physical tensile test was conducted. I did it. As a result, when the wire mesh of the conventional casting machine was used, there were 3 relatively large foreign objects caught in the wire, 3 small foreign objects caught in the wire mesh, and 1 wire mesh mixed into the cast product. In addition, in the case of a casting machine in which a filter was attached to the lower end of the stalk, there were two cases where large foreign matter was entangled and three cases where minute foreign matter was entangled. On the other hand, among the 50 cast products produced by the present casting apparatus, the number of products that had foreign matter entrapped in them was reduced to three, and these were also very small. Comparing the mechanical properties of a cast product produced by the casting machine of the present invention with a conventional casting machine in which a wire mesh is installed at the cavity sprue and a ceramic filter is attached to the lower end of the stalk, it is found that the mechanical properties of a cast product without foreign matter being entrapped are found. No difference was observed in the results, but when the entrainment was large, it was about 80% compared to normal, and when the entrainment was small, it was about 9%.
The mechanical properties were reduced to 0%, and the cast product according to the present invention was able to have stable mechanical properties.

The reason why we specified the thickness of the ceramic filter to be 10 to 55 mm, the pore sphere diameter to Φ1 to 8 mm, and the porosity to be 70% or more is that if the thickness is 551 or more, the pore sphere diameter is Φ1 mm or less, and the porosity is 70% or less. , the pressure loss when pouring from the furnace through the stalk into the mold cavity becomes large, reducing the pressurizing effect and causing internal defects such as cavities.
This is because there is no change in the filtration effect of the target oxide. Furthermore, if the thickness is less than 10 mm and the diameter of the pore sphere is more than Φ8III), this will result in a decrease in the filtration performance of the ceramic filter for foreign matter including oxides, such as a decrease in the capture efficiency of minute oxides. Therefore, it is limited to the above range.

(Effect of the invention) By installing a ceramic filter in the middle of the stalk in the casting method of the present invention and making the surface of the molten metal in the stalk the same height as the top surface of the filter before and after casting, the molten metal flows inside the stalk while adhering to the inner wall of the stalk. Entrainment of returned oxides is also reduced, making it possible to produce cast products with mechanical properties close to those originally possessed by metals, with less variation and stable quality.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the installation position and molten metal height of the ceramic filter of the present invention, Fig. 2 is a diagram showing the casting apparatus used in the embodiment of the present invention, and Fig. 3 is a diagram of the pressure control circuit. Figure 4 is a diagram showing the relationship between pressure and time during casting. Figure 5 is a diagram showing a conventional casting device with a wire mesh attached to the mold cavity sprue. Figure 6 is a diagram showing a ceramic filter. 1 is a diagram showing a conventional casting apparatus equipped with a. Mold cavity 2: Lower mold 3: Upper mold 4: Mold side pressure vessel 5 Nistalk 6: Holding furnace 7: Holding furnace side pressure vessel
15: Electromagnetic switching valve 16: Pilot pressure type pressure regulating valve 17: Electropneumatic proportional valve 18: Mold side pressure line 19: Furnace side pressure line 21: Ceramic filter 22 Molten metal surface in the tank 23: Molten metal surface in the holding furnace 24: Holding furnace 25: Wire mesh
26: Cavity sprue section Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) Either or both of a holding furnace or melting furnace (hereinafter referred to as a furnace) and a casting mold or a metal mold (hereinafter referred to as a mold),
A casting device that is installed in an airtight container and casts the molten metal in the furnace into the mold via a stalk that communicates the furnace and mold by a pressure difference between the furnace side and the mold side. Equipped with a ceramic filter installed at a position higher than the molten metal level in the furnace on the internal mold sprue side, and a pressure control device that keeps the molten metal level in the stalk almost the same, the molten metal in the furnace can be adjusted depending on the number of casting shots, etc. A casting device characterized in that even if the height of the molten metal changes, the height of the molten metal in the stoke and the top surface of the filter are made almost the same before and after casting. (2) The thickness of the ceramic filter is 10 to 55 mm,
The casting apparatus according to claim 1, wherein the diameter of the pore sphere is Φ1 to 8 mm and the porosity is 70% or more.