JP2000343196A - Plunger sleeve for die cast machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plunger sleeve structure which is superior in warmth retaining property against a molten metal, and rarely causes deposition of the molten metal right below the molten metal pouring port. SOLUTION: This plunger sleeve has a cylindrical shape, and is connected to a mold at the front end side (the left end side in Figure), and a plunger chip is inserted into the sleeve from the rear end side (the right end side in Figure). An outer cylinder 11 is composed of a precipitation hardening stainless steel SUS630, and is metallurgically connected to the outside of an inner cylinder 12 by a hot isostatic pressing method (HIP). The inner cylinder 12 is composed of a hot mold alloy tool steel SKD61, and nitriding treatment is applied to the inner face of the steel after quenching and tempering. On the connecting face of the inner cylinder 12 and the outer cylinder 11, a step is provided at the middle in an axial direction. Thickness of the inner cylinder 12 on the rearward side of the step is thicker than that on the forward side. A molten metal pouring port 13 is formed at the thick wall part on the rearward side of the step.

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 plunger sleeve which serves as both a molten metal receiver and a pressure cylinder in a die casting machine for aluminum alloys or magnesium alloys.

[0002]

2. Description of the Related Art Conventionally, alloy tool steel for hot dies such as SKD61 (JIS G 4404) has been used for a plunger sleeve which also serves as a molten metal receiver and a pressure cylinder in a die casting machine.

[0003] Such an alloy tool steel for a hot die has a relatively high thermal conductivity of 29 W / (m · K), so that the molten metal (molten metal) filled in the plunger sleeve is rapidly cooled. In particular, the molten metal that has come into contact with the inner surface of the plunger sleeve starts to solidify in a short time. Therefore, there is a problem that the molten metal is immediately solidified after being injected from the plunger sleeve and injected into the mold, thereby causing a product defect due to poor running of the molten metal, entrainment of the heat insulating chill layer, and the like. In particular, when manufacturing a thin-walled molded product with a small amount of molten metal, there is a tendency that many product defects such as a hot water boundary and a poor running of the molten metal occur.

In order to solve such a problem, a plunger sleeve having a composite structure with improved heat retention and thermal shock resistance has been developed (for example, Japanese Patent Application No. 10-109408,
Japanese Patent Application No. 11-073079). The plunger sleeve has a composite structure, and has excellent wear resistance and heat check resistance, and is an alloy tool steel for a hot die (for example, SKD).
8, SKD61), and the outer cylinder part is made of precipitation hardening stainless steel (for example, SUS630, SUS631) having relatively low thermal conductivity and excellent thermal shock resistance. These plunger sleeves
Because of its excellent heat retention properties against molten metal, product defects such as hot water, poor run-out and entrainment of a heat insulating chill layer are unlikely to occur, and the effect of reducing the defective rate of die-cast products has been recognized.

However, in the above-mentioned plunger sleeve,
Molten metal adheres to the inner surface of the plunger sleeve to reduce the inner diameter, and as a result, the plunger tip does not move in a short time. This is because the temperature of the inner cylinder is too high, especially immediately below the melt inlet, as the outer cylinder having a relatively low thermal conductivity increases the heat retention of the plunger sleeve. This is because welding to the inner surface of the plunger sleeve becomes easy.

For this reason, it is necessary to frequently cut off the welded metal from the inner surface of the plunger sleeve, so that the downtime of the die casting machine is lengthened, which has been a factor of reducing productivity.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional plunger sleeve for a die-casting machine. It is another object of the present invention to provide a structure of a plunger sleeve in which welding of a molten metal directly under a molten metal injection port does not easily occur.

[0008]

A plunger sleeve for a die casting machine according to the present invention has a cylindrical shape, is connected to a mold at a front end side, a plunger tip is inserted from a rear end side, and a plunger sleeve near a rear end is provided. A plunger sleeve for a die casting machine having a molten metal inlet formed on a side surface,
An inner cylindrical portion made of an alloy tool steel for a hot die, and a heat conductivity at 300 ° C. of 10 W / (m · K) or more and 25 W / (m ·
K) The following alloy steel is composed of an outer cylinder part which is metallurgically joined to the outside of the inner cylinder part, and a joint surface between the inner cylinder part and the outer cylinder part has a step in the middle in the axial direction. The thickness of the inner cylindrical portion is formed so as to be thicker on the rear side than the step compared with the front side, and the molten metal inlet is formed on the rear side relative to the step. It is characterized by.

According to the plunger sleeve of the present invention, the thickness of the outer cylindrical portion (relatively low in thermal conductivity) is reduced immediately below and around the molten metal inlet, so that heat is radiated in the above-mentioned portion. Without being hindered, overheating on the inner surface of the plunger sleeve can be prevented. As a result, the speed at which the molten metal adheres to the inner surface of the plunger sleeve in the above portion can be reduced.

[0010] Further, in a portion closer to the mold than the above-mentioned portion, the thickness of the outer cylindrical portion is thicker, so that a heat retaining effect by the outer cylindrical portion can be obtained. Therefore, the plunger sleeve of the present invention is generally superior in the heat retaining property to the molten metal as compared with the plunger sleeve entirely made of the alloy tool steel for hot dies. As a result, according to the plunger sleeve of the present invention, product defects such as a hot water boundary, poor hot water running, and the involvement of a heat insulating chill layer are less likely to occur.

The outer cylinder may be provided only from the middle to the front of the plunger sleeve in the axial direction, and the inner cylinder may be exposed to the outer peripheral surface at the rear. In that case, the plunger sleeve for a die casting machine of the present invention has an inner cylindrical portion made of an alloy tool steel for a hot die and a heat conductivity at 300 ° C. of 10 W / (m · K) or more and 25 W / (m · K). It is made of the following alloy steel, and is composed of an outer cylinder part metallurgically bonded to the outside of the inner cylinder part, and the inner cylinder part has a step in the middle of the outer peripheral surface in the axial direction, The wall thickness of the cylindrical portion is formed so as to be thicker on the rear side than this step compared with the front side, and the outer cylindrical portion covers the outside of the inner cylindrical portion only on the front side of the step, The melt inlet is
It is formed behind the step.

Preferably, the inner cylindrical portion is made of an alloy tool steel SKD61 or SKD8 (JIS G44) for hot dies.
04, 1983).

Preferably, the outer cylinder portion is made of a precipitation hardening stainless steel SUS630 or SUS631 (JIS
G4303, 1991).

Alternatively, the outer cylinder portion may have a C: 0.1 to
0.5 wt%, Si: 3 to 7 wt%, Mn: 0.1 to
1.0 wt%, Ni: 5 to 18 wt%, Cr: 0.5 to
8 wt%, the balance being composed of alloy steel substantially composed of Fe.

Preferably, after quenching and tempering the surface of the inner cylindrical portion, a nitriding treatment is performed.

[0016] Preferably, the thickness of the inner cylindrical portion is 1 mm or more and 5 mm or less on the front side of the step.

When the inner cylinder and the outer cylinder are metallurgically joined, for example, a hot isostatic pressing method, a brazing method, or a diffusion joining method can be applied.

[0018]

FIG. 1 shows an example of the structure of a plunger sleeve according to the present invention.

The plunger sleeve has a substantially cylindrical shape, and is connected to a mold (not shown) at the front end (left end in the figure), and from the rear end (right end in the figure). (Not shown) is inserted. A molten metal inlet 13 is formed on a side surface near the rear end of the plunger sleeve.

The outer cylinder 11 is made of precipitation hardening stainless steel S
It is made of US630 and is metallurgically joined to the outside of the inner cylinder portion 12 by hot isostatic pressing (HIP). The inner cylinder part 12 is made of an alloy tool steel SKD61 for a hot die,
The inner surface is subjected to a nitriding treatment after quenching and tempering. The joint surface between the inner cylinder portion 12 and the outer cylinder portion 11 has a step in the middle in the axial direction, and the thickness of the inner cylinder portion 12 is greater behind the step than on the front side. The molten metal inlet 13 is formed in a thick portion on the rear side of the step.

Next, a method of manufacturing the plunger sleeve shown in FIG. 1 will be described.

(A) The outer cylinder part 11 (the part to be finished later into the outer cylinder part) is manufactured by machining using SUS630. FIG. 2 shows the shape.

(B) The inner cylinder portion 12 (the portion to be finished later as the inner cylinder portion) is manufactured by machining using the SKD61. FIG. 3 shows the shape.

(C) As shown in FIG. 4, the inner cylinder 12 is inserted into the outer cylinder 11.

(D) As shown in FIG. 5, the entire outer cylinder 11 and inner cylinder 12 are housed in a can 15. The lid 16 is attached to the upper part of the can body 15 by welding, and the inside of the can body 15 is sealed. Note that a vacuum pipe 17 is attached to the lid 16.

(E) The inside of the can 15 is evacuated through the evacuation pipe 17. When a predetermined degree of vacuum is reached, the evacuation pipe 17 is crushed while continuing the evacuation, and is sealed by welding.

(F) Using a hot isostatic press (HIP), the outer cylinder 11 is integrally joined to the inner cylinder 12 by heating to 1050 ° C. under 1000 atm.

(G) The can body 15 is removed by cutting. Further, the integrated outer cylinder portion 11 and inner cylinder portion 12 are machined, and a molten metal injection port 13 (FIG. 1) is formed to form a plunger sleeve. However, extra space is left on the inner peripheral surface as a grinding allowance.

(H) The inner peripheral surface is subjected to quenching and tempering to harden the inner peripheral surface.

(I) The inner peripheral surface is finished by grinding to finish the plunger sleeve as shown in FIG.

(G) Further, the inner peripheral surface is subjected to nitriding treatment to complete the plunger sleeve.

In order to confirm the effects of the plunger sleeve according to the present invention, the plunger sleeve manufactured by the above method is mounted on a cold-chamber die-casting machine, and a personal computer case (1 mm thick) is formed using an aluminum alloy. Was manufactured. As a result, the plunger sleeve (SUS6
The following advantages were observed in comparison with the case where the inner cylinder portion 12 made of SKD61 was thinly joined with a uniform thickness to the outer cylinder portion 11 made of 30.

(A) The disadvantage of the plunger sleeve having the conventional structure, that is, the welding of the molten metal at the lower portion of the molten metal injection port in a relatively short time, whereby the phenomenon that the plunger tip does not move is prevented. Work stability was improved.

(B) The work of shaving off the metal deposited at the lower part of the molten metal injection port is not required, thereby reducing the loss time and improving the productivity of the die casting process.

(C) As a result of the elimination of product defects occurring before and after the above-mentioned loss time, the product defect rate is reduced as compared with the case where a plunger sleeve having a conventional structure is used.
It decreased by about 50%.

(D) The life of the plunger sleeve itself was not different from that of the conventional structure.

[Brief description of the drawings]

FIG. 1 is a view showing an example of the structure of a plunger sleeve according to the present invention.

FIG. 2 is a diagram showing a shape of a portion corresponding to an outer cylinder in a process of manufacturing a plunger sleeve according to the present invention.

FIG. 3 is a view showing a shape of a portion corresponding to an inner cylindrical portion in a step of manufacturing a plunger sleeve according to the present invention.

FIG. 4 is a view showing a state in which an inner cylindrical portion is inserted into an outer cylindrical portion in a step of manufacturing a plunger sleeve according to the present invention.

FIG. 5 is a view showing a state in which an outer tube and an inner tube are accommodated in a can for performing HIP processing in a step of manufacturing a plunger sleeve according to the present invention.

[Explanation of symbols]

 11 ... outer cylinder part (part to be finished later as outer cylinder part), 12 ... inner cylinder part (part to be finished later as inner cylinder part), 13 ... molten metal inlet, 15 ... can body , 16 ... lid, 17 ... pipe for evacuation.

Claims (8)

[Claims] 1. A plunger sleeve for a die-casting machine having a cylindrical shape, connected to a mold at a front end side, a plunger tip inserted from a rear end side, and a molten metal injection port formed on a side surface near a rear end. An inner cylindrical portion made of an alloy tool steel for a hot die, and a heat conductivity at 300 ° C. of 10 W / (m · K) or more 2
An outer cylinder portion made of an alloy steel of 5 W / (m · K) or less and metallurgically joined to the outside of the inner cylinder portion, and a joint surface between the inner cylinder portion and the outer cylinder portion is a shaft. A step in the middle of the direction, the thickness of the inner cylindrical portion is formed so as to be thicker on the rear side than this step as compared with the front side, and the melt injection port is on the rear side than the step A plunger sleeve for a die casting machine, which is formed. 2. A plunger sleeve for a die-casting machine having a cylindrical shape, connected to a mold at a front end side, a plunger tip inserted from a rear end side, and a molten metal inlet formed on a side surface near a rear end. An inner cylindrical portion made of an alloy tool steel for a hot die, and a heat conductivity at 300 ° C. of 10 W / (m · K) or more 2
An outer cylinder portion made of an alloy steel of 5 W / (m · K) or less and metallurgically bonded to the outside of the inner cylinder portion, and the inner cylinder portion has an outer peripheral surface at an intermediate portion in the axial direction. A step is formed, and the thickness of the inner cylindrical portion is formed so as to be thicker on the rear side than the step and on the front side, and the outer cylindrical portion is formed on the inner cylinder only on the front side of the step. A plunger sleeve for a die casting machine, wherein an outside of the portion is covered, and the molten metal injection port is formed on a rear side of the step. 3. The SKD61 or SKD
The plunger sleeve for a die casting machine according to claim 1 or 2, wherein 4. The outer cylinder portion is made of SUS630 or SU
The plunger sleeve for a die casting machine according to claim 1, wherein the plunger sleeve is S631. 5. The outer cylinder part has a C content of 0.1 to 0.5 wt.
%, Si: 3 to 7 wt%, Mn: 0.1 to 1.0 wt%
%, Ni: 5 to 18 wt%, Cr: 0.5 to 8 wt%,
The plunger sleeve for a die casting machine according to claim 1 or 2, wherein the remainder is made of an alloy steel substantially made of Fe. 6. The plunger sleeve for a die casting machine according to claim 1, wherein the inner cylindrical portion is subjected to a nitriding treatment after quenching and tempering on a surface thereof. 7. The plunger sleeve for a die casting machine according to claim 1, wherein a thickness of the inner cylindrical portion is 1 mm or more and 5 mm or less on a front side of the step. 8. The method according to claim 1, wherein the inner cylinder and the outer cylinder are joined to each other by hot isostatic pressing, brazing, or diffusion joining. Plunger sleeve for die casting machine.