JP2002059251A - Die bush for die casting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die bush for a die casting machine having excellent heat resistance, corrosion resistance, wear resistance and galling resistance and providing a long service life. SOLUTION: The die bush is provided with a complex structure and constituted of an inner cylinder 11, an outer cylinder 12 and a jacket 13 for water cooling. The inner cylinder 11 is made of a cermet containing Ni as the base and further including Mo, B and Si, and its thickness is <=1.5 mm. The outer cylinder 11 is made of a carbon steel for structural carbon steel (S48C). The jacket 13 for water cooling is made of a steel pipe and fitted so as to cover the outer periphery of the outer cylinder 12. On the inner peripheral surface of the water-cooling jacket 13, a plurality of grooves 14 where the cooling water flows are formed in the circumference direction. The inner cylinder 11 is joined to the inside of the outer cylinder 12 by a method such as the HIP method, brazing method or diffusion junction method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a sprue bush which is mounted on a sprue of a mold and serves as a passage for a molten metal in a die casting machine used for casting of an aluminum alloy or a magnesium alloy.

[0002]

2. Description of the Related Art FIG. 5 shows a structure near a gate of a die of a die casting machine. In the figure, 1 is a gate bush, 2 is a fixed mold, and 3 is a movable mold.

The fixed mold 2 is held on the front surface of the fixed die plate 4. The injection sleeve 5 is a fixed die plate 4
Is mounted so as to penetrate the center portion thereof.
The gate bush 1 is detachably attached to the gate section of the fixed mold 2. The front end of the sprue bush 1 opens toward the cavity 9 of the mold, and the rear end is connected to the front end of the injection sleeve 5. Conventionally, alloy tool steel such as SKD61 (JIS) is widely used for the sprue bush 1.

[0004] After the molten metal is introduced into the injection sleeve 5, it is pushed forward (to the mold side) by the plunger tip 6, and is filled into the cavity 9 through the sprue bush 1. When the plunger tip 6 is driven, a short time before the plunger tip 6 reaches the sprue bush 1, the forward speed of the plunger tip 6 is increased, and the molten metal is quickly filled in the cavity 9. After filling the molten metal, the injection power of the plunger tip 6 is increased to apply pressure to the molten metal in the cavity 9. After the molten metal filled in the cavity 9 is cooled and solidified, the mold is opened and the molded product is taken out. Next, the mold is closed again, and the next casting operation is performed.

[0005] By repeating the above casting operation, the following phenomenon occurs in the sprue bush: (a) The wear between the plunger tip and the plunger tip that slides at high speed causes the gap between the sprue bush and the plunger tip. The clearance increases, and the molten metal enters the clearance; (b) In particular, when casting aluminum molten metal, the above-mentioned clearance increases due to erosion (corrosion) of the sprue bush due to contact with the molten metal. (C) When the sprue bush is overheated, the clearance increases and the melt enters therein. (D) When the sprue bush is deformed by the pressure at the time of casting, the clearance is increased. Increases, and the molten metal enters therein.

As described above, when the molten metal that has entered the clearance adheres to the inner peripheral surface of the molten metal bush or the outer peripheral surface of the plunger tip and solidifies, a galling occurs on the sliding surface. Or the plunger tip becomes prematurely unusable.

[0007] The occurrence of such galling not only increases the labor and expendable supplies cost of the operator, but also has a problem that the productivity of the apparatus is greatly reduced because the replacement of the injection sleeve takes a particularly long time. Was.

Further, when the heat retaining performance of the mold and the sprue bush is increased, the fluidity of the molten metal is increased, and the molten metal is more easily run. And the productivity was worsened.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional sprue bush, and an object of the present invention is to provide excellent wear resistance and galling resistance.
It is to provide a sprue bush with a long service life.

[0010]

A sprue bush for a die casting machine according to the present invention is a sprue bush for a die casting machine which is detachably mounted on a sprue of a die and has a heat conductivity of 30 W / (m · K). An outer cylinder made of the above steel,
An inner cylinder attached to the inner peripheral surface of the outer cylinder and made of Ni-B-Si-Mo-based or Ni-B-Si-Mo-C-based cermet and having a thickness of 0.1 mm or more and 1.5 mm or less; Water cooling means provided on the outer cylinder.

Conventional alloy tool steel (for example, SKD61)
The drawbacks of the sprue bush are that the sliding surface lacks abrasion resistance and galling resistance in addition to lack of corrosion resistance to molten aluminum. Therefore, in the present invention,
The sprue bush is composed of a composite structure composed of an inner cylinder, an outer cylinder and a water cooling jacket, and the inner cylinder is composed of the above-mentioned Ni-based cermet, so that the inner peripheral surface has heat resistance, corrosion resistance, galling resistance and resistance to heat. Has improved abrasion.
However, the above-mentioned Ni-based cermet does not have sufficient high-temperature strength, so that a single-layer structure cannot withstand high casting pressure. Therefore, the outer cylinder is made of steel having excellent rigidity and high-temperature strength, thereby ensuring high-temperature strength as a whole. As described above, according to the sprue bush of the present invention, a long life can be realized.

Further, a water cooling means is provided on the outer cylinder,
By setting the thickness of the inner cylinder to 1.5 mm or less,
While preventing the overheating of the sprue bush by the molten metal filled in the mold through the sprue bush, ensuring the cooling performance for the molten metal after filling the cavity,
Productivity can be increased. The thickness of the inner cylinder is
If it is 0.1 mm or more, the above effects can be obtained.

In order to ensure the cooling performance, it is preferable that the heat conductivity of the outer cylinder is high, and the heat conductivity is 30 W
/ (M · K) or more is suitable, and the outer cylinder and the inner cylinder can secure cooling performance higher than that of the conventional SKD61 single-layer sprue sleeve.

The inner cylinder is provided on the inner peripheral surface of the outer cylinder.
For example, bonding can be performed by any of the HIP method, brazing method, and diffusion bonding method.

[0015]

FIG. 1 shows an example of a sprue bush for a die casting machine according to the present invention. In the figure, 11 is an inner cylinder, 1
2 denotes an outer cylinder, 13 denotes a water cooling jacket (water cooling means).

The sprue bush has a composite structure and includes an inner cylinder 11, an outer cylinder 12, and a water cooling jacket 13. In this example, the inner cylinder 11 is made of a cermet containing Ni, Mo, B and Si,
Its inner diameter is 70 mm and its thickness is 1.5 mm. The above cermet is excellent in heat resistance, corrosion resistance to molten aluminum, galling resistance and abrasion resistance of a sliding surface. The outer cylinder 11 is made of carbon steel for machine structure (S48C), and has an outer diameter of 88 mm and a thickness of 8.25 mm. The water cooling jacket 13 is made of steel pipe and is attached so as to cover the outer periphery of the outer cylinder 12. A plurality of grooves 14 are formed on the inner peripheral surface of the water cooling jacket 13 in the circumferential direction. By flowing cooling water into the groove 14, the outer cylinder 12 can be cooled from its outer peripheral surface.

Next, a method of manufacturing the sprue bush will be described.

(A) As shown in FIG. 2, carbon steel S48C for machine structure was machined to produce an outer cylinder equivalent portion 12a.

(B) As shown in FIG. 3, carbon steel S25C for machine structure was machined to produce a core 16.

(C) Si: 4.6 wt%, B: 3.1 w
A raw material powder for sintering was prepared by melting a material having a composition consisting of t%, Mo: 20 wt%, and Ni: balance, followed by water atomization.

(D) As shown in FIG.
The bottom plate 17 was fixed to the bottom of 2a by welding, and then the core 16 was inserted inside the outer cylinder equivalent portion 12a, and the cores were aligned, and then the core 16 was fixed.

(E) The gap 11a between the outer cylinder equivalent portion 12a and the core 16 was filled with the above-mentioned raw material powder, and then a lid 18 was attached to the upper end surface by welding, degassed, and then sealed.

(F) The assembly completed as described above was housed in a HIP device and subjected to HIP processing at a temperature of 1030 ° C. for 3 hours.

(G) After the completion of the HIP processing, the core 16 was removed by machining, and then the end face and the inner and outer peripheries were machined to predetermined dimensions and shapes.

(H) Finally, a water-cooling jacket 13 was shrink-fitted to the outside of the outer cylinder 12 and then attached by welding the ends.

In order to confirm the performance of the sprue bush according to the present invention, the sprue bush manufactured by the above method is mounted on a cold chamber type die casting machine (mold clamping force: 500 ton).
n), and a casting test of an aluminum alloy was performed.

The casting conditions were as follows: Casting raw material: ADC12 Melt temperature: 600 ° C. Lubricant: Oil type Lubrication method: Drop on plunger tip Plunger tip: SKD61 quenched material (HRC45).

For comparison, a conventional sprue bush (hereinafter referred to as a conventional product) having a single-layer structure made of SKD61 and having an inner peripheral surface subjected to nitriding treatment is used under the same conditions and under the same conditions. An alloy casting test was performed.

As a result, when the sprue bush according to the present invention is used, seizure or melting of the molten metal does not occur.
The change in clearance between the plunger tip and the plunger tip due to abrasion or galling has been reduced to about half that of the conventional product. Specifically, after the casting of 40,000 shots, the change in the inner diameter of the sprue bush was compared. When the sprue bush according to the present invention was used, an increase of 0.10 mm was recognized, When using the conventional product,
An increase of 0.21 mm was observed.

The service life of the conventional sprue bush is about 5-7.
In contrast to 10,000 shots, the service life of the sprue bush according to the present invention was about three times that of about 200,000 shots.
Also, the life of the mating plunger tip was extended to about twice (about 30,000 shots) when the sprue bush according to the present invention was used, as compared with the case where the conventional sprue bush was used. The production cost of the sprue bush according to the present invention was about twice that of the conventional product.

Further, for comparison, the inner cylinder (Ni-B-Si
A sprue bush in which the thickness of -Mo cermet) was increased to 2.5 mm was compared with the sprue bush according to the present invention (inner cylinder thickness: 1.5 mm) in terms of the cycle time of casting. As a result, it was confirmed that when the sprue bush according to the present invention was used, the cycle time was shortened by about 5% and the life of the sprue bush was improved by about 10% as compared with this comparative material.

The inner cylinder 11 is made of the Ni shown in the above example.
Instead of the -B-Si-Mo cermet, Ni-B-
Si-Mo-C cermet (for example, C: 0.1 w
t%, Si: 4.6 wt%, B: 3.1 wt%, Mo:
Even if it is manufactured with 20 wt% (Ni: balance), the same effect can be obtained.

As a method of joining the inner cylinder 11 inside the outer cylinder 12, instead of the HIP method shown in the above example,
Brazing or diffusion bonding can be used.

[0034]

The sprue bush for a die-casting machine according to the present invention is excellent in wear resistance and galling resistance, and has corrosion resistance to molten metal, so that it has a longer service life than conventional sprue bushes made of alloy tool steel. It has. Therefore,
By using the sprue bush of the present invention, the productivity of the die casting machine can be greatly improved.

Further, since the sprue bush for a die casting machine of the present invention has a two-layer structure comprising an inner cylinder and an outer cylinder, the mold is filled in a mold by appropriately setting the thickness of the inner cylinder. Thus, the cooling performance for the molten metal can be ensured.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the structure of a sprue bush according to the present invention.

FIG. 2 is a diagram illustrating a method for manufacturing a sprue bush according to the present invention.

FIG. 3 is a diagram illustrating a method of manufacturing a sprue bush according to the present invention.

FIG. 4 is a diagram illustrating a method of manufacturing a sprue bush according to the present invention.

FIG. 5 is a view for explaining a gate bush of the die casting machine and a structure around the gate bush.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Gate bush, 2 ... Fixed die, 3 ... Moving die, 4 ... Fixed die plate, 5 ... Injection sleeve, 6 ... Plunger chip, 9 ... Cavity , 11 ... inner cylinder, 12 ... outer cylinder, 13 ... water cooling jacket (water cooling means), 14 ... groove, 16 ... core, 17 ... bottom plate 18 ... lid .

Claims (3)

[Claims] 1. A sprue bush for a die casting machine which is detachably mounted on a sprue of a die, an outer cylinder made of steel having a thermal conductivity of 30 W / (m · K) or more, and an inner periphery of the outer cylinder. It is attached to the surface and is made of a Ni-B-Si-Mo-based or Ni-B-Si-Mo-C-based cermet and has a thickness of 0.1 mm or more and 1.5 mm or less. A spout bush for a die casting machine, comprising: a water cooling means; 2. The inner cylinder has an HI on an inner peripheral surface of the outer cylinder.
2. The sprue bush for a die casting machine according to claim 1, wherein the sprue is joined by any one of a P method, a brazing method, and a diffusion bonding method. 3. The sprue bush for a die casting machine according to claim 1, wherein the water cooling means is a water cooling jacket attached so as to cover an outer periphery of the outer cylinder.