JPH0386363A - Method for squeezing molten metal - Google Patents

Abstract

PURPOSE:To efficiently manufacture a molten metal squeezed product with little defect by advancing a punch to the position near thick part under the unsolidified condition of the molten metal in a metallic mold and further advancing the punch under high pressure after solidifying the molten metal at the gate of the metallic mold. CONSTITUTION:After clamping a fixed mold 8 and movable mold (not shown in the figure) of the metallic mold M, the molten metal is filled up in a cavity 21 through a sprue 22. Successively, by advancing the punch 16, the molten metal is pressurized and cast. In the above molten metal squeezing method, the punch 16 is advanced to the position near the thick part T in the product under the unsolidified condition of the molten metal M. Then, the working pressure of the punch 16 is set to a lower force than the clamping force for the metallic mold M and gap in the molten metal at the thick part T is easily eliminated. Successively, after solidifying the molten metal at the gate 22a in the metallic mold M, the punch 16 is further advanced with great force. Then, the working pressure of punch 16 is set to a higher force than the mold clamping force for metallic mold M. By this method, the molten metal squeezing is executed with suitable pressure without being limited with the mold clamping force to obtain the casting product having little defect.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a molten metal forging method in which a molten metal filled in a mold is pressurized with a punch to obtain a casting with few internal defects.

(Prior art) The molten metal forging method is a pressure solidification method in which a molten or semi-molten metal material (hereinafter referred to as unsolidified) is placed in a mold and solidified by applying high compressive force to obtain the desired shape. A type of
It is a technology that is free from blowholes and sink marks, allows for the production of fine-structured products with high precision and high yield, and has been widely used.

(Problem to be Solved by the Invention) By the way, the molten metal forging method requires applying high pressure to the unsolidified metal material in the mold, but if this pressure is greater than the clamping force of the mold, This may cause the mold, which is composed of split molds, to separate or cause metal material to leak.
The amount of pressure that can be applied to the molten metal with a molten metal forging punch is limited by the amount of clamping force of the mold.

Additionally, in general, internal defects in castings often occur in the center of the thick part of the product, and proactively using molten metal forging near such areas is an effective way to obtain cast products with fewer defects. This is desirable.

This invention was made based on these circumstances, and it is possible to increase the degree of freedom in applying pressure to the molten metal by avoiding the restrictions imposed by the clamping force of the mold, and to pressurize the molten metal with an appropriate amount of pressure. The purpose of this invention is to obtain a cast product with fewer defects by pressurizing the molten metal at a position near the thick interior of the product, where internal defects are likely to occur.

(Means for Solving the Problem) In order to achieve this object, the present invention provides a molten metal forging method in which molten metal filled in a mold is pressurized with a punch, when the molten metal in the mold is in an unsolidified state. A first step in which the punch is advanced to a position near the thick part of the product, and a second step in which the punch is further advanced under large pressure after the molten metal in the weir of the mold has solidified, and the first step is as follows. In addition to setting the operating pressure of the punch to be lower than the clamping force of the mold,
The operating pressure of the punch in the second step is set to be greater than the clamping force of the mold.

(Function) According to this invention, since the punch is advanced to a position near the thick part of the product when the molten metal in the mold is in an unsolidified state, the operating pressure of the punch is small, and the mold is clamped. The tip of the punch can be positioned close to the thick part of the product with a pressure smaller than the force.

After the molten metal in the weir of the mold has solidified at this position, the punch is advanced further with great pressure, so at this point the surface of the molten metal in the mold has started to solidify, so the punch adds to the molten metal. As a result of the pressure being partially borne by the surface portion of the solidified molten metal, a pressing force greater than the mold clamping force can be applied to the molten metal with a punch without causing the above-mentioned problems.

Therefore, it is possible to avoid the restrictions imposed by the clamping force of the mold and increase the degree of freedom in applying pressure to the molten metal, making it possible to pressurize the molten metal at an appropriate pressure. By pressurizing the molten metal at a nearby location,
Cast products with fewer defects can be obtained.

(Example) The present invention will be explained below using a casting apparatus shown in the figure.
This casting apparatus is supplied with molten aluminum alloy by gravity casting.

First, the entire outline of the casting apparatus 1 will be explained with reference to FIGS. 1 and 2.

The casting apparatus 1 includes a base 2 framed with channel material, and two fixed platens 3 erected apart from each other on the base 2.
．． 4, and four guide rods 5 are horizontally suspended between these fixed platens 3.4.

A movable platen 6 is slidably fitted into these guide rods 5 and is configured to be movable forward and backward along the guide rods 5.

A fixed mold 8 is installed on the fixed platen 3 via a base plate 7, and the other fixed platen 4 has a hydraulic cylinder for opening and closing the mold (hereinafter referred to as a mold cylinder).
11 are installed.

A movable mold 13 is attached to the movable platen 6 via a base member 12, and a mold M is constituted by this movable mold 13 and the fixed fJ18.

The tip of the piston rod lla of the mold cylinder 11 mounted on the fixed platen 4 is connected to the movable platen 6 via a connecting fitting 6a.

The movable platen 6 is driven forward and backward toward the fixed platen 3 by the hydraulic pressure supplied to the mold cylinder 11, and by advancing the movable platen 6 toward the fixed platen 3, the movable mold 13 is fixed. Platen 3
The mold M is brought into a state in which molten metal can be poured by colliding with the fixed mold 8 installed in the movable platen 6.
By moving the movable mold 13 backward (moving toward the fixed platen 4 side), the movable mold 13 is separated from the fixed mold 8, and the product can be released from the gold mm.

As is clear from FIG. 1, a hydraulic cylinder for molten metal forging ( A molten metal forging cylinder 14 (hereinafter referred to as a molten forging cylinder) is fixed, and a molten metal forging punch (hereinafter simply referred to as a punch) is attached to the tip of a piston rod 14a of this molten forging cylinder 14.
16 is installed.

This punch 16 is formed as shown in FIG. 3 and fitted into a mold M.

That is, gold ffiM (FIG. 3 shows the fixed type 8)
includes a cavity 21, a sprue 22 and a weir 2 for product formation.
2a, a space 23 linearly connected from the lateral direction is formed in a cavity 21 formed in a horizontally elongated shape, and a half-split type bushing 24 is attached to the outer end of this space 23.

The punch 16 is made of heat-resistant steel and has a straight part Lea formed to have the same diameter and a tapered part 16 formed to have a small diameter at the tip.
b are formed linearly and integrally, and are installed almost in line with the center ring ○-○ of the cavity 21.

Casting using the mold M configured as described above is performed as follows.

First, with the mold M in an open state, the metal f is heated by a burner or the like.
After heating f1M appropriately, a mold release material containing graphite or the like is applied to the surface of the mold M.

Thereafter, the punch 16 is set in a predetermined position of the mold M (the position indicated by the solid line in FIG. 3).

At this time, the straight portion lea of the punch 16 is placed in the through hole 24a of the bush 24, and the tapered portion 18b projects into the cavity 21.

This prevents the molten aluminum alloy from leaking out from the through hole 24a when the molten aluminum alloy is poured into the cavity 21, and also allows the tip of the tapered portion 18b to be located near the thick wall portion T of the product inside the cavity 21. This is to reduce the distance traveled to reach the position.

Then, the mold cylinder 11 is operated to advance the movable platen 6, and the movable mold 13 is brought into contact with the fixed mold 8 to perform mold clamping. The fixed mold 8 is maintained in a pressed state with a predetermined pressing force by the cylinder 11, and this pressing force is referred to as mold clamping force in this specification.

Note that the mold clamping force can be applied not only by such a mold cylinder 11 but also by various known structures.

Thereafter, the mold M is filled with molten metal into the cavity 21 through the sprue 22 by gravity casting.

After the molten metal is cast into the gold ff1M, the punch 16 is
Operate as shown in FIG.

Time A may be 0 time A indicating the completion of casting of the molten metal.
．． At time B, after about 5 seconds have elapsed, the expansion operation of the melt forging cylinder 14 starts.

At this point B, the molten metal in the cavity 21 is in an unsolidified state and there is a space in the cavity 21 that is not filled with molten metal, so the stretching operation is performed at a low pressure for 2 to 3 seconds.

At time C after the stretching operation, the molten metal fills the cavity 21, so the pressure accompanying the stretching operation of the melt-forging cylinder 14 increases suddenly.

After time C, excess molten metal in the cavity 21 is drained from the sprue 2.
This is because the job of the punch 16 is to push the molten metal back to the 2nd side and crush the bubbles contained in the molten metal.

This pressurized state by the melt forging cylinder 14 is 0.
It continues for about 5 to 1.0 seconds and reaches a point.

From this point C to this point, the pressing force of the molten metal by the melt forging cylinder 14 is
(for example, 500 kg/c+
+2) Since this is the setting, there is no risk of separation of the mold M or leakage of molten metal.

The above steps from point A to point A correspond to the first step in the present invention.

After the point reaches the point E, the pressurizing force by the melt forging cylinder 14 remains equal to or slightly smaller than the mold clamping force and remains at 0.
．． Maintain for about 5 seconds.

Between this point and time E, the portion of the molten metal poured into the mold M that comes into contact with the mold M begins to solidify, and the solidification of the weir 22a of the mold M is completed. The punch 1
The tip of 6 is connected to the product thickness inside T as shown by the imaginary line in Fig. 3.
has reached a position near .

Therefore, after time E, the hydraulic pressure supplied to the melt forging cylinder 14 is increased to increase the pressurizing force by the melt forging cylinder 14, and a large pressure exceeding the mold clamping force (for example, 150
By operating the punch with a sand diameter of 2.5 to 3.0 kg/cm2), the molten metal can be pressurized at a pressure appropriate for molten metal forging (time point F).

Between time E and time F, the surface of the molten metal in the mold M has started to solidify as described above, so even if a large pressurizing force exceeding the mold clamping force is applied to the molten metal, the gold mm There is no risk of separation or leakage of molten metal.

As a result, the molten metal is forged with an appropriate pressure in the vicinity of the product thick-walled portion T, and defects in the cast product are efficiently eliminated.

After time F, after holding the punch 16 in the cold sand for about 45 to 60 seconds, the punch 16 is moved back and removed from the gold WM.
Open the mold M and take out the product.

As explained above, according to this embodiment, when the molten metal in the mold M is in an unsolidified state, the punch 1 can reach the thick part T of the product.
6 is advanced, the operating pressure of the punch 16 is small, and the tip of the punch 16 can be positioned close to the thick part T of the product with a pressure smaller than the mold clamping force.

Then, after the molten metal in the weir 22a of the mold M has solidified at this position, the punch 16 is further advanced with great pressure. As a result of the pressure applied to the molten metal being partially borne by the surface portion of the solidified molten metal, a pressing force greater than the mold clamping force can be applied to the molten metal by the punch 16 without causing the above-mentioned problems.

Therefore, it is possible to avoid the restrictions imposed by the clamping force of the mold M, increase the degree of freedom in applying pressure to the molten metal, and make it possible to pressurize the molten metal at an appropriate pressure. By pressurizing the molten metal near the portion T, a cast product with fewer defects can be obtained.

In addition, in the embodiment described above, a mask cylinder for a hydraulic brake is formed as a product, and in this case, the punch 16 is used to forge the molten metal and at the same time form the cylinder hole bottom of the brake master cylinder, which is the product. This has the advantage of reducing the number of post-processing steps in mask cylinder manufacturing.

In addition, in this embodiment, as explained above, the tip of the punch 16 is placed in advance in the cavity 21 and the molten metal is filled. However, the present invention is not limited to this, and the present invention is not limited to this. It is also possible to carry out the same procedure by later advancing the punch into the molten metal.

(Effects of the Invention) Since the present invention is configured as described above, it is possible to avoid the restriction caused by the clamping force of the mold, increase the degree of freedom in applying pressure to the molten metal, and pressurize the molten metal at an appropriate pressure. In addition, by pressurizing the molten metal at a position near the thick wall part of the product where internal defects are likely to occur, a cast product with fewer defects can be obtained.

[Brief explanation of drawings]

The drawings relate to an embodiment of the present invention, and FIG. 1 is an overall plan view of the casting device, FIG. 2 is a side view of the casting device, and FIG.
FIG. 4, which is a view taken along the line ■-■ in the figure, is a diagram showing changes in the pressing force of the punch. M: Mold, T: Product thick part, 8: Fixed mold, 11: Hydraulic cylinder for opening and closing the mold, 13: Movable mold, 14: Hydraulic cylinder for molten metal forging, 16: Punch, 21; Cavity, 22; Mouth, 22a; cough.

Claims (1)

[Scope of Claims] In a molten metal forging method in which molten metal filled in a mold is pressurized with a punch, the first step is to advance the punch to a position near a thick part of the product when the molten metal in the mold is in an unsolidified state. and a second step of advancing the punch further under high pressure after the molten metal in the weir of the mold solidifies, and the operating pressure of the punch in the first step is lower than the clamping force of the mold. and the operating pressure of the punch in the second step is set to be greater than the clamping force of the mold.