JPH0218942B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure casting method capable of casting high quality products free of cavity defects.

Conventionally, in pressure casting methods such as die casting methods and high-pressure solidification methods, the gases present in the mold cavity and the gases generated due to the rapid combustion or evaporation of the mold release agent applied to the cavity during casting. The presence of gas holes and/or pinholes caused by entrainment, as well as the presence of shrinkage cavities caused by solidification shrinkage of the molten metal, often had a negative impact on the reliability and use of the product.

In particular, when products obtained by pressure casting are used as parts of fluid equipment or pressure equipment, gas holes cause short circuits between passage holes, making the product impossible to use. Furthermore, as light metals such as aluminum and magnesium and their alloys are increasingly used to reduce the weight of equipment, there is an increasing need to thoroughly remove these blowholes, particularly gas holes.

As a countermeasure against this blowhole, when manufacturing products with boss parts with large changes in wall thickness, such as rocker arms and valve housings, using the pressure casting method,
A method has been considered in which a pressurizing plunger is used to fill the product cavity with molten metal, and a pressurizing pin separate from the pressurizing plunger is used to pressurize the thick boss portion of the product before the molten metal solidifies. According to this method, new molten metal can be replenished with new molten metal into the shrinkage cavities generated by the solidification of the molten metal, thereby making it possible to eliminate the shrinkage cavities as well as crushing gas holes caused by gas caught in the molten metal to some extent. You can get pretty good quality products.

However, although the above method has few problems with small parts, the reality is that it is difficult to completely eliminate gas holes when casting large parts.

In order to reduce the occurrence of blowholes, it is considered that the amount of gas present in the cavity should be reduced as much as possible.

The present invention has been made based on the above knowledge, and in the conventional pressure casting method using a pressure pin, by devising the operation of the pressure pin, the gas existing in the product cavity can be removed as much as possible. The objective is to cast high-quality products without blowholes or other cavities.

According to the present invention, in order to cast a product having a boss portion with a large change in wall thickness without forming a cavity defect, the present invention uses a pressurization method that includes a step of locally pressurizing the thick wall portion with a pressurizing pin in addition to the pressurizing plunger. In the pressure casting method, a step of causing the pressure pin to protrude into the product cavity, a step of casting the molten metal into the product cavity with a pressure plunger, and a step in which the molten metal reaches the vicinity of the tip of the pressure pin during the casting. A pressure casting method that includes a step of retracting a pressure pin in synchronization with the intrusion speed of the molten metal at the time when the molten metal enters the product cavity, and a step of protruding the pressure pin to apply pressure after filling the molten metal into the product cavity and before the molten metal solidifies. It is achieved by doing so.

Next, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a schematic diagram showing the main parts of a vertical die-casting machine using pressure pins, and FIGS. 2 to 5 are enlarged views of part A in FIG. It shows the movement of the pin and molten metal.

In FIG. 1, 1 is the upper mold, 2 is the lower mold,
A product cavity 3 in the shape of a rocker arm is defined by the upper mold 1 and the lower mold 2. This upper mold 1
Sleeves 4 and 5 are attached to the lower die 2 and the lower die 2, respectively, and a pressure plunger 6 and a counter plunger 7 are slidably inserted into the sleeves 4 and 5. A pouring port 8 is provided in a part of the sleeve 4, and the molten metal is poured into the space defined by the sleeve 4 and the counter plunger 7 from the pouring port 8. Further, a fixed casting pin 9 and a movable pressing pin 10 are arranged in a thick wall portion of the product cavity 3 to face each other.

Next, the operation of the vertical die casting apparatus shown in FIG. 1 will be explained.

A product cavity 3 is defined by bringing the upper mold 1 and the lower mold 2 together and clamping them together. At this time, the pressure pin 10 is in a position protruding into the product cavity 3 as shown in FIG. 2, and the pressure plunger 6 is in the first position.
It has been pulled up to the position shown in the figure. Next, the counter plunger 7 is raised by a drive source (not shown) to a position where it closes the gate 11 leading to the product cavity 3. This counter plunger 7
A spout 8 is inserted into the space defined by the sleeve 4 and the sleeve 4.
Pour in a predetermined amount of molten metal using a karahishiyaku (12). The state at this time (excluding the pressure pin 10) is shown in FIG. By allowing it to stand for a while, impurities such as slag will float upwards, leaving only clean molten metal below.

Next, the counter plunger 7 is lowered and the gate 11 is lowered.
By opening it, the molten metal is gently introduced into the product cavity 3. The introduction of the molten metal into the product cavity 3 is carried out using only the weight of the molten metal or while applying light pressure using the pressure plunger 6 so as not to involve the air in the cavity.

When the molten metal 13 is introduced to position B shown in FIG. 2, that is, near the tip of the pressure pin 10 protruding into the product cavity 3, the filling speed of the molten metal 13 is synchronized by a signal from a synchronizer (not shown). to pull up the pressure pin 10 (FIGS. 3 and 4).
At this time, shortly before the molten metal 13 reaches point B, pressurization is performed by the pressurizing plunger 6 or the pressurizing force is increased. As conceptually shown in Figs. 2 to 4, the amount of air is smaller than the conventional one due to the protruding pressure pin 10, so there is less air entrainment and the blowhole 14 is also smaller. Become.

Thereafter, before the molten metal 13 solidifies, the pressure pin 10 is again projected to pressurize the molten metal 13. Due to the pressure applied by the pressure pin 10, the blow hole 14 is almost completely crushed and disappears.

After the molten metal 13 has solidified, the pressure plunger 6 and the pressure pin 10 are pulled up. After that, the mold is opened and the product is taken out using a commonly known method.

The present invention has been described above with reference to the drawings. According to the present invention, the amount of air that is drawn in is reduced by at least the protrusion of the pressure pin 10, so that a high-quality product without blowholes can be obtained. A rocker arm was actually manufactured from an aluminum alloy in accordance with the pressure casting method of the present invention using the apparatus shown in FIG. 1, but no shrinkage cavities or blowholes were observed in the resulting product.

Further, according to the present invention, there is almost no need to change the main structure of the pressure casting device that uses a pressure pin in addition to the pressure plunger, and it is only necessary to simply add a part of the mechanism that controls the operation of the pressure pin. Therefore, higher quality products can be obtained at almost the same cost as before.

In addition, in the examples, the rigid die casting method was explained as an example of the pressure casting method, but the low pressure casting method,
Of course, similar effects can be obtained by high-pressure coagulation.

Further, in the embodiment, the pressure pin was made to protrude from the beginning, but this may be done at any time before the molten metal enters the product cavity.

Furthermore, it goes without saying that the scope of the present invention includes changes in the configuration without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the main parts of a vertical die-casting machine used in carrying out the present invention, and FIGS.
The figure is an enlarged view of part A in FIG. 1, and shows the movements of the pressure pin and the molten metal in each process according to the present invention. 1... Upper die, 2... Lower die, 3... Product cavity, 4... Sleeve, 5... Sleeve, 6... Pressure plunger, 7... Counter plunger, 8...
...Pouring spout, 9... Fixed casting pin, 10... Pressure pin, 11... Gate, 12... Hishiyaku.

Claims (1)

[Claims] 1. In a pressure casting method that includes a process of locally pressurizing the thick wall part with a pressure pin in addition to a pressure plunger, in order to cast a product having a boss part with a large change in wall thickness without blowhole defects, pre-casting pressure is applied. A process in which a pressure pin is made to protrude into the product cavity, a process in which molten metal is cast into the product cavity using a pressure plunger,
During the casting process, when the molten metal reaches the vicinity of the tip of the pressure pin, the pressure pin is moved back in synchronization with the intrusion speed of the molten metal, and after the molten metal is filled into the product cavity and before the molten metal solidifies, the pressure pin is A pressure casting method comprising the step of protruding and applying pressure.