JPH06277817A - Low pressure casting device - Google Patents

Abstract

PURPOSE:To prevent shrinkage cavity and microporosity without having a change in solidifying speed and weight increase by constituting the part having a large cavity thickness to a movable die, which is supported movably separated and formed from other die, and connecting the movable die to a pressurizing device. CONSTITUTION:The molten metal in holding furnace is poured into a cavity 5 in die through a stoke 6. The molten metal flows in the cavity 5 from a disk part 8 to a rim part 9, filling the cavity 5 by molten metal. When some fixed temp. is reached after molten metal is filled in the cavity 5, a pressurizing cylinder is operated, a movable die is pushed, locally pressurizing the molten metal in the cavity 5. By this method, the molten metal is subjected to locally pressurizing and feeding before solidification accordingly, a molten metal is fed at a place likely to generate shrinkage cavity, not causing shrinkage cavity. Also, when a microporosity is generated, it is crushed by pressurizing.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to low pressure casting equipment.

[0002]

2. Description of the Related Art Vehicle wheels made of light alloy are
It is cast by the low pressure casting method. More specifically, a cast aluminum wheel is formed by pushing low pressure aluminum molten metal into a cavity formed inside a mold (for example, an upper die, a lower die, and a horizontal die assembly) from a lower position and then cooling the die to open the die. Take out.

[0003]

However, in the conventional casting, shrinkage cavities and microporosity are apt to occur in the thick portion of the cavity, for example, the joint between the disk and the rim of the wheel. There was a problem that a decrease occurred.

In the low pressure casting method, in order to improve the strength, the die is water-cooled or cast in an inert atmosphere in order to refine the structure by increasing the solidification rate. As for shrinkage cavities, countermeasures are taken by changing the wall thickness distribution of the casting to be more appropriate for preventing shrinkage cavities, or by locally cooling and controlling the cooling rate of each part.

However, the conventional strength improvement and shrinkage cavity countermeasures have the following problems. First of all, when changing the solidification rate or performing local cooling, the temperature of other parts also changes,
Poor bathing and new casting defects will occur.
Further, when the wall thickness distribution of the casting is changed to achieve the directional solidification, there is a problem that the wall thickness is partially increased and the wheel weight is increased.

An object of the present invention is to provide a low pressure casting apparatus capable of preventing shrinkage cavities and microporosity without causing a change in solidification rate and an increase in weight.

[0007]

A low pressure casting apparatus according to the present invention for achieving the above object comprises the following apparatus. That is, of the mold that defines the casting cavity inside, the part that defines the portion with a large cavity thickness is formed separately from the other mold parts and movably supported to form a movable mold part, A low-pressure casting device in which a pressurizing device is connected to the movable mold part.

[0008]

The above-mentioned apparatus of the present invention constitutes a local pressure type low pressure casting apparatus. Conventionally, a mold part corresponding to a region where shrinkage cavities are likely to occur is made movable, and pressure is applied when the temperature reaches a certain temperature which is a process in which the molten metal solidifies. The pressurizing effect of the pressurization removes shrinkage cavities, and the pressurizing effect crushes the microporosity.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A low pressure casting apparatus according to a preferred embodiment of the present invention will be described below with reference to the drawings. In FIG.
The mold of the light alloy wheel 1 is a lower mold 2, an upper mold 3, and a horizontal mold 4.
And a cavity 5 is formed inside. The molten aluminum is pushed up and filled into the cavity 5 from below through the stalk 6 and the lower die gate 7. After the solidification, the mold is opened and the wheel 1 is taken out. The wheel 1 is composed of a disc 8 and a rim 9, and the joint portion between the disc 8 and the rim 9 and the disc boss portion 10 are thick, which is a portion where shrinkage cavities easily occur in the conventional method.

A portion of the die that is in contact with the thick portion of the wheel 1 is formed separately from the other die portions and is movably supported to form a movable die portion 11. Movable part 11
A pressure device, for example, a pressure cylinder 12, is connected to the. When the movable mold part 11 is pushed in the direction in which the thickness of the cavity is reduced by operating the pressurizing cylinder 12, the molten metal in the cavity is pressed and the part is pressurized.

In the case of a wheel, the movable mold part 11 is provided on the outer peripheral side of the joint between the disk 8 and the rim 9 and on the outer peripheral side of the boss 10.
Is provided. The movable die portion 11 on the outer peripheral side of the joint portion between the disk 8 and the rim 9 is movable in the wheel radial direction, and the movable die portion 11 on the outer peripheral side of the boss portion 10 is movable in the wheel axial direction. These movable mold parts 11 are provided by retracting from the wheel surface in the wheel thickness direction from the wheel thickness after casting (position of FIG. 2), and during casting of the wheel up to the wheel thickness surface after casting (of FIG. 3). Position) Pressed by the pressure cylinder 12.

Next, a low pressure casting method using the above apparatus will be described. That is, the molten metal in the molten metal holding furnace is poured into the cavity 5 in the mold via the stalk 6. Molten metal is cavity 5
The fluid flows from the disk 8 to the rim 9 and the cavity 5 is filled with the molten metal.

When the molten metal is filled in the cavity 5 and a certain molten metal temperature is reached (before solidification), the pressurizing cylinder 12 is operated to push the movable mold portion 11 to locally melt the molten metal in the cavity 5. Pressurize. In this case, until the molten metal reaches a certain temperature, as shown in FIG.
Is lowered from the regular shape position, and when the temperature of the molten metal drops to a certain temperature, the metal is pushed to the regular shape position as shown in FIG. After the molten metal solidifies, the mold is opened and the cast product is taken out of the mold.

In the above casting, since the molten metal is locally pressed and pressed before solidification, even if shrinkage cavities are generated, the molten metal is pushed there and the shrinkage cavities do not occur. Further, even if microporosity occurs, it is crushed by the pressure.

[0015]

According to the present invention, the following effects are obtained. I. Due to the effect of the riser through the movable mold part by the pressure device,
The occurrence of shrinkage cavities can be prevented. B. The microporosity can be crushed by the pressure effect, and the generation of minute holes (pinholes) when cutting can be suppressed. C. By locally pressing the feeder, the molten metal replenishment property to the thin-walled portion can be improved, and defective molten metal can be suppressed. D. The partial pressurization improves the strength of each part. E. Extra strength can be removed by improving strength, which is advantageous in reducing the weight of the wheel.

[Brief description of drawings]

FIG. 1 is a sectional view of a low pressure casting apparatus according to an embodiment of the present invention.

2 is a partial cross-sectional view of the apparatus of FIG. 1 during molten metal filling.

3 is a partial cross-sectional view of the apparatus of FIG. 1 after locally applying molten metal pressure.

[Explanation of symbols]

 1 Wheel 2 Lower Mold 3 Upper Mold 4 Horizontal Mold 5 Cavity 6 Stoke 7 Gate 8 Disc 9 Rim 10 Boss 11 Movable Mold 12 Pressure Cylinder

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area B22D 18/08 A

Claims (1)

[Claims] 1. A portion of a mold for defining a casting cavity inside, which defines a portion having a large cavity thickness,
A low-pressure casting apparatus, characterized in that it is dividedly formed from another mold part, movably supported to form a movable mold part, and a pressure device is connected to the movable mold part.