JPH0679759B2 - Vertical die casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a vertical die casting method.

[Conventional technology]

The vertical die casting method, which is a type of die casting method using a vertical sleeve and the molten metal casting method, has less air entrapment in the casting during casting, and the sleeve is a vertical type, so the slag rises upward in the sleeve. Since it is difficult to enter the cavity, it is used as a casting method with which a cast product with few defects and high strength can be obtained.

By the way, a general method of supplying molten metal into the sleeve during casting is to pump the molten metal from the melting furnace by a ladle regardless of whether the sleeve is horizontal or vertical. However, in such a method, the slag on the surface of the molten metal in the melting furnace may be pumped up simultaneously with the molten metal. In the case of a vertical sleeve, most of this slag floats up in the sleeve, but fine particles flow into the cavity before rising, and when trying to obtain a product of higher quality than the conventional product, there is no damage. There is a risk that Further, since the molten metal in the melting furnace is disturbed by the ladle, the oxidation of the molten metal is promoted and the components change. Further, when the molten metal is supplied into the sleeve, there is air in the sleeve, which causes oxidation of the molten metal and entrapment of air. Further, there is a problem that the ladle must be replaced with an appropriate size according to the weight of the product.

Several techniques have been developed to solve the above problems. For example, as a method of supplying molten metal without using a ladle, in order to prevent slag from being caught in the molten metal, the molten metal surface of the molten metal holding furnace is pressurized with air, an inert gas, etc. as in the low pressure casting method. A method of pushing up into a vertical sleeve is described in JP-A-56-19962. Further, in order to prevent air from being entrained in the molten metal, a method of depressurizing the inside of the cavity and the sleeve to replace the air in the sleeve and the cavity with a reactive gas is disclosed in JP-A-55-8
No. 382.

[Problems to be Solved by the Invention]

However, in the method of pushing up the molten metal into the sleeve with pressurized air, inert gas, etc., there is no concern that the slag will be mixed into the molten metal, but there is air remaining in the sleeve, so there is a risk of entraining air in the molten metal. There is. Further, the method using the reactive gas does not have a problem such as entrainment of air, but it cannot be said that the problem in supplying the molten metal has been solved.
Further, since a reactive gas is used, it causes a high cost. On the other hand, it is required that the amount of molten metal supplied into the sleeve is always constant.

That is, since the molten metal does not have high fluidity like water and solidifies with time, a difference occurs between the pressure applied to the molten metal in the sleeve and the pressure received at the corners of the cavity. This pressure loss depends on the amount of molten metal supplied into the sleeve, and unless this amount is always constant, a cast product of constant quality cannot be obtained.

The present invention involves entrapment of air and air in the molten metal, oxidation of the molten metal,
The present invention is intended to solve the problem of constant supply of the molten metal into the sleeve, and an object thereof is to provide a vertical die casting method capable of obtaining a product having no defects and excellent strength.

[Means for Solving the Problems]

The vertical die casting method of the present invention is a casting method using a vertical die casting device having a mold and a vertical sleeve, and a vertical sleeve is used as an opening / closing means for a communication path between the mold cavity and the vertical sleeve. A counter-tip for sealing, a plunger-tip for sealing the vertical sleeve, a runner extending obliquely upward from the melting furnace and connected to the vertical sleeve at a position higher than the cavity, and inside the vertical sleeve. Using a device equipped with an exhaust pipe, one end of which is connected to a decompression pump for decompressing, and the other end of which is open above the runner opening of the vertical sleeve, and the plunger tip is first placed in the vertical sleeve. The counter chip is disposed above the upper end of the exhaust pipe opening, and further in the vertical sleeve, the counter chip is connected to the cavity of the mold and the vertical slit. The counter chip is arranged so that the upper end surface of the counter chip is in a predetermined position with the communication path to the valve closed, and then the decompression pump is operated to decompress the inside of the vertical sleeve and the runner of the vertical sleeve. The molten metal is sucked into the vertical sleeve from the melting furnace within the range that exceeds the lower end of the opening and does not reach the lower end of the exhaust pipe opening, and then depressurizes to release the portion of the vertical sleeve that exceeds the lower end of the runner opening. By returning the molten metal to the melting furnace, a predetermined amount of molten metal corresponding to the internal volume of the vertical sleeve in the range from the predetermined position on the upper end surface of the counter-chip to the lower end of the runner opening is placed in the vertical sleeve. To supply.

In the method of the present invention, the inside of the vertical sleeve between the counter tip and the plunger tip is decompressed, and the molten metal is sucked up from the melting furnace and supplied into the vertical sleeve.
The tip and plunger tip must be able to seal the vertical sleeve with no clearance between them and the vertical sleeve. Therefore, it is preferable to use a plunger tip and a counter tip made of a copper-beryllium (Cu-Be) alloy.

The counter-chip also serves as the opening / closing means for the communication passage between the cavity of the mold and the vertical sleeve, without specially providing it. That is, when the upper surface of the counter-tip is located above the vertical sleeve opening of the communication passage, the vertical sleeve and the cavity between the counter-tip and the upper plunger tip are counter-counted at the lower portion of the vertical sleeve. Blocked by the tip.

The runway for sucking the molten metal from the melting furnace to the vertical sleeve is preferably kept warm by a heat insulating material such as ceramic so that the molten metal is not cooled.

Decompression degree ΔP (mmHg) required to suck up the molten metal into the vertical sleeve is determined by the height h (mm) from the molten metal surface in the melting furnace to the vertical sleeve opening of the runner and the density of the molten metal. When the molten metal is an alloy mainly composed of aluminum, it can be calculated by the following formula: ΔP (mmHg) = h (mm) /5.0. Therefore, if the pressure is reduced more than the degree of pressure reduction ΔP, the molten metal easily flows into the vertical sleeve. The height h from the surface of the melt to the opening of the sleeve of the melt may be selected as an appropriate value depending on the positional relationship between the casting apparatus and the melting furnace and the degree of pressure reduction.

Therefore, by operating a decompression pump (more specifically, for example, a vacuum pump) to decompress the inside of the vertical sleeve for an appropriately set time, and then release the decompression and release it to the atmosphere, the excess molten metal melts. Returning to the furnace, a predetermined amount of molten metal corresponding to the internal volume of the vertical sleeve ranging from a predetermined position on the upper end surface of the counter-chip to the lower end of the runner opening can be supplied into the vertical sleeve.

The runner should be properly tilted and attached to the vertical sleeve. When the angle between the runner and the vertical sleeve is greater than 70 °, it is difficult for the molten metal in the runner to return to the melting furnace when the depressurization is released. Since they are too close to each other and it is difficult to manufacture the device, it is preferable to set the angle to 30 ° to 70 °.

[Action]

In a casting method using a vertical die casting apparatus having a mold and a vertical sleeve, a communication path between a mold cavity and the vertical sleeve is closed, and an upper portion of the vertical sleeve is a plunger.
The inside of the vertical sleeve can be depressurized by sealing the lower part of the vertical sleeve with the tip with the counter-tip. Since the vertical sleeve is connected to the melting furnace by the runner, the molten metal can be sucked up into the vertical sleeve by depressurizing the inside of the vertical sleeve. Since one end of the exhaust pipe connected to the decompression pump is open at the other end above the vertical sleeve opening of the runner, the molten metal does not enter the exhaust pipe and the decompression pump.

The sleeve and runner are depressurized for a predetermined time at a predetermined degree of decompression, the molten metal is sucked up from the melting furnace into the vertical sleeve over the lower end of the runway opening of the sleeve, and then the depressurization is released. The molten metal in a portion beyond the lower end of the passage opening returns to the melting furnace through a passage that extends obliquely downward to the melting furnace, and then flows into the vertical sleeve from a predetermined position on the upper surface of the counter-chip to the opening of the passage. A predetermined amount of molten metal corresponding to the inner volume of the vertical sleeve in the range up to the lower end remains. afterwards,
Pressure casting is possible with a plunger tip and a counter tip.

〔Example〕

The present invention will be described in more detail with reference to the drawings by the following examples.

Example FIG. 1 shows an example of a vertical die casting apparatus used in the method of the present invention. The present apparatus has a mold 1 and a sleeve 2 which is substantially vertically incorporated in the mold 1, and the sleeve 2 communicates with a cavity 3 of the mold 1 and a gate 4. A counter chip 5 made of a copper-beryllium alloy for sealing the sleeve 2 is provided below the sleeve 2.
The tip 5 can slide up and down in the sleeve 2. A plunger tip 6 made of a copper-beryllium alloy for sealing the sleeve 2 is provided on the upper portion of the sleeve 2, and the plunger tip 6 can also slide up and down in the sleeve 2. The runner 7 has a lower end opening into the molten metal 9 of the melting furnace 8 and an upper end opening into the sleeve 2, forming an angle of about 60 ° with the sleeve 2. Further, one end of the sleeve 2 is connected to a vacuum pump (not shown) (a kind of pressure reducing pump, which is convenient for practical use because it is easy to use). The other end of the exhaust pipe 10 is located above the sleeve opening of the runner 7. It is open. In the figure, 11 is Noro.

The method of the present invention for casting using the vertical die casting apparatus of FIG. 1 will be described below with reference to FIG. 2 (see FIG. 1 in some cases). As shown in FIG. 2a), the plunger tip 6 is arranged above the upper end of the opening of the exhaust pipe 10, and the counter tip 5 is connected to the gate 4 (the cavity 3 of the mold 1 and the sleeve 2). Is placed so that the upper end surface of the counter-chip 5 is at a predetermined position, and then a vacuum pump (not shown) connected to one end of the exhaust pipe 10 is operated to move the sleeve. The inside of 2 is decompressed and the molten metal 9 is sucked up from the melting furnace 8. The molten metal 9 exceeds the lower end of the opening of the runner 7 of the sleeve 2 and the exhaust pipe 10
When the inside of the sleeve 2 is reached within the range where it does not reach the lower end of the opening, the pressure reduction is released. Then, as shown in FIG. 2 b), the molten metal 9 in the portion beyond the lower end of the opening of the runner 7 in the sleeve 2 returns to the melting furnace 8 and, as a result, from a predetermined position on the upper end surface of the counter-chip 5. A predetermined amount of molten metal 9 corresponding to the inner volume of the sleeve 2 up to the lower end of the opening of the runner 7 can be supplied into the sleeve 2.

Next, as shown in FIG. 3, the plunger tip 6 and the counter tip 5 are lowered, the gate 4 closed by the counter tip 5 is opened, the molten metal 9 is filled in the cavity 3, and the plunger is closed. Pressurize with tip 6 and counter-tip 5. After the molten metal 9 in the cavity 3 is cooled and solidified, the product is taken out.

Comparative Example A product was cast in the same manner as in Example except that the molten metal was supplied using a ladle.

Test Example The quality of the products of Examples and Comparative Examples was examined.

FIG. 4 shows the defective rate due to slurping. The defective casting rate of the cast product of the example was 0.7%, which was a lower value than the comparative example of 1%.

FIG. 5 shows the results of examining the blister occurrence rate in which the surface is swollen by the internal gas when the product is heated.
The blister generation rate of the example was 2.6%, which was considerably lower than 4.3% of the comparative example.

Also, after holding the molten metal (JIS AC8A) for 24 hours, Mg in the molten metal
The amount of (magnesium) reduction was investigated. Results are shown in FIG. In the example, the amount of Mg reduction in the molten metal is 0.15%, which is less than that of the comparative example.
It was much smaller than 25% and the composition of the alloy was stable.

〔The invention's effect〕

In the method of the present invention, as described above, the pressure in the vertical sleeve is reduced and the molten metal is sucked up into the sleeve and is gently supplied, so that entrapment of noro and entrainment of air in the molten metal are prevented and It is difficult to oxidize, and the gas in the molten metal easily escapes. Furthermore, since the molten metal in the melting furnace is not disturbed by the ladle, the oxidation of the molten metal is not promoted and the composition of the molten metal is stable. In particular, in the vertical sleeve, a predetermined amount of molten metal corresponding to the internal volume of the vertical sleeve in the range from a predetermined position on the upper surface of the counter-chip to the lower end of the runner opening, that is, always a constant and accurate amount. Since the molten metal can be supplied, the pressure inside the cavity during casting is always the same. As a result, a high-quality cast product with few defects and high strength can always be easily obtained.

Further, in the method of the present invention, the predetermined amount of molten metal can be easily changed, for example, by changing the setting position of the counter-chip, so that the amount of molten metal can be changed or the amount of molten metal can be finely adjusted according to the size of the product. It can be done easily.

Further, unlike the conventional method, since the ladle is not used, even if the weight of the product to be cast is changed, it is not necessary to replace the ladle, and the number of steps can be reduced.

Furthermore, since the pouring burr in the runner does not fall onto the mold, 1
Since it is not necessary to clean the mold surface for each shot, the number of steps can be reduced.

Furthermore, since the amount of molten metal supplied into the vertical sleeve can be controlled by setting the position of the counter-tip, casting can be automated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a vertical die casting device used in the embodiment, FIG. 2 a) is a schematic diagram showing a state during hot water supply of the vertical die casting device used in the embodiment, and FIG. 2 b) is used in the embodiment. FIG. 3 is a schematic view showing the state of the vertical die casting apparatus at the time of completion of hot water supply, FIG. 3 is a sectional view showing the state of the vertical die casting apparatus during pressure casting used in the embodiment, and FIG. FIG. 5 is a graph showing the defective rate of bite, FIG. 5 is a graph showing the blister occurrence rate of Examples and Comparative Examples, and FIG. 6 is a graph showing the amount of Mg reduction in molten metal of Examples and Comparative Examples. In the figure, 1 ... Mold, 2 ... Sleeve, 3 ... Cavity, 4 ... Gate, 5 ... Counter tip, 6 ... Plunger tip, 7 ... Runner, 8 ... Melting furnace, 9 ... Molten metal , 10 ... Exhaust pipe 11 ... Noro

Claims (1)

[Claims] 1. A casting method using a vertical die casting apparatus having a mold and a vertical sleeve, for opening and closing a communication path between a mold cavity and the vertical sleeve, and for sealing the vertical sleeve. Counter tip, plunger tip for sealing the vertical sleeve, runner extending obliquely upward from the melting furnace and connected to the vertical sleeve at a position higher than the cavity, and for depressurizing the vertical sleeve. A device provided with an exhaust pipe having one end connected to a decompression pump and the other end opening above the runner opening of the vertical sleeve is used. First, in the vertical sleeve, insert the plunger tip into the exhaust pipe opening. The counter chip is disposed above the upper end, and further in the vertical sleeve, the counter chip forms a communication path between the cavity of the mold and the vertical sleeve. In a closed state, and the counter-chip upper end surface is arranged at a predetermined position, and then the decompression pump is operated to decompress the inside of the vertical sleeve, and the bottom end of the runner opening of the vertical sleeve is crossed and The molten metal is sucked up from the melting furnace into the vertical sleeve within the range where it does not reach the lower end of the exhaust pipe opening, and then the depressurization is released to return the molten metal in the vertical sleeve beyond the lower end of the runner opening to the melting furnace. According to this, a predetermined amount of molten metal corresponding to the inner volume of the vertical sleeve in the range from the predetermined position on the upper end surface of the counter-chip to the lower end of the runner opening is supplied into the vertical sleeve. Vertical die casting method.