JP2000202607A - Plunger sleeve for die casting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plunger sleeve, in which the heat retaining property and the heat-shock resistance to molten metal are provided and the damage caused by the overheat at the dropping part of molten metal is hardly developed. SOLUTION: This plunger sleeve for die casting machine is provided with a complex structure and constituted with a metal-made outer cylinder part 11 and an alloy steel-made inner cylinder part 19 provided with eroding restance to the molten metal. The thermal conductivity at 300 deg.C of the outer cylinder part 11 is 25-52 W/(m.K). The thermal conductivity at 300 deg.C of the inner cylinder part 19 is 10-25 W/(m.K) and the thickness thereof is 1-5 mm. The outer cylinder part 11 and the inner cylinder part 19 are mutually and metallurgically joined. Desirably, the inner cylinder part 19 is constituted with a precipitation hardening type stainless steel of SUS630 or SUS631 (JIS G 4305), and the nitriding treatment is applied on the inner diameter surface thereof.

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 or magnesium alloy.

[0002]

2. Description of the Related Art Conventionally, in a die casting machine, a plunger sleeve serving as both a molten metal receiver and a pressurizing cylinder is provided with S
Alloy tool steel for hot dies such as KD61 (JIS G 4404) has been used.

[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 cooled in a short time. In particular, the molten metal in contact with the inner surface of the plunger sleeve starts to solidify. Therefore, there is a problem that the molten metal solidifies immediately after the molten metal is injected from the plunger sleeve and injected into the mold, thereby causing product defects such as poor running of the molten metal and a hot water boundary. 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 poor running of the molten metal, a hot water boundary, and poor filling occur.

In order to solve such a problem, a plunger sleeve having a composite structure in which a ceramic inner cylinder is fitted into a steel or metal outer cylinder has been developed. JP-A-2-179346, JP-A-5-038563).

[0005] Since these ceramic inner cylinders have low thermal conductivity (about 20 W / (m · K)), they are excellent in heat retention for molten metal and hardly cause the above-mentioned problems. Therefore,
The defective rate of the die-cast product can be reduced. Further, since the ceramic inner cylinder portion has excellent corrosion resistance to the molten aluminum, erosion hardly occurs at the falling portion of the molten metal.

However, the ceramic inner cylinder portion has a problem that a large thermal stress is generated by the contact of the molten metal due to the above-mentioned property of low thermal conductivity, which causes an instantaneous breakage.

In order to solve this problem, improvements such as providing a stress relaxation layer between a ceramic inner cylinder and a steel outer cylinder have been made (Japanese Patent Laid-Open No. 5-050204). Effect has not been obtained. This is a result of the basic properties of ceramics, which have low thermal conductivity, poor toughness, and low reliability with respect to strength.
At present, no effective countermeasures have been found.

[0008] Another disadvantage of the plunger sleeve using the ceramic inner cylinder is that it is difficult to perform the cutting process and must rely on the grinding process with low processing efficiency. This is a factor that increases the sleeve manufacturing cost.

In order to compensate for the drawbacks of the plunger sleeve using the ceramic inner cylinder portion, alloy steel having a relatively high thermal conductivity is applied to the inner cylinder portion and heat conduction is performed to the outer cylinder portion. Alloy steel with a relatively low modulus (eg, SUS630,
This is a plunger sleeve having a two-layer structure using SUS631) (Japanese Patent Application No. 10-109408).

[0010] However, this plunger sleeve is superior to the conventional single-layer plunger sleeve of SKD61 in heat retention, but since the effect of the heat retention is slow to appear, the plunger sleeve is used between the filling of the molten metal and the injection. (2-4 seconds) not enough heat retention.

Therefore, the reason why the heat retention between the filling and the injection of the molten metal is enhanced is to use alloy steel (for example, SUS630, SUS630, which has corrosion resistance to the molten metal and low thermal conductivity).
SUS631) (Japanese Patent Application No. 10-107758). Since the plunger sleeve is excellent in heat retention between the filling and injection of the molten metal, product defects such as poor running of the molten metal, hot water boundary, and poor filling are unlikely to occur. Therefore, the defect rate of the die-cast product can be reduced.

[0012] However, this plunger sleeve also has the disadvantage that the temperature of the falling portion of the molten metal becomes too high, and damage is likely to occur in that portion. In particular, the amount of molten metal charged to the inner volume of the plunger sleeve (hereinafter, referred to as
When the “filling rate” is large, this phenomenon becomes remarkable and shortens the life of the plunger sleeve.

[0013] Therefore, it has been developed to suppress the overheating of the temperature of the falling part of the molten metal while securing the heat retention from the filling of the molten metal to the injection, while providing corrosion resistance to the molten metal and a thermal conductivity. Relatively low alloy steel (for example, SU
S630 and SUS631) are used for the inner cylinder, and a double-layered plunger sleeve is used for the outer cylinder using alloy steel having a relatively high thermal conductivity (Japanese Patent Application No. 10-107756).

This plunger sleeve is excellent in the heat retaining property for the molten metal in a relatively short time (2 to 4 seconds) from when the plunger sleeve is filled with the molten metal until it is injected. Temperature gradually decreases. Therefore, it is possible to prevent the temperature of the plunger sleeve from excessively rising while securing the heat retaining effect. In this plunger sleeve, it is important that the thickness of the inner cylinder portion having a relatively low thermal conductivity is important. If it is too thin, the temperature will decrease before injection, and if it is too thick, the plunger sleeve temperature will rise too much. There's a problem.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the conventional plunger sleeve for a die casting machine, and an object of the present invention is to provide a plunger sleeve for a die casting machine having a two-layer structure. It is an object of the present invention to provide a plunger sleeve which has heat retention and thermal shock resistance to a molten metal, and is less likely to be damaged by overheating in a falling portion of the molten metal.

[0016]

According to the present invention, there is provided a plunger sleeve for a die-casting machine, comprising an outer cylindrical portion made of a metal material having a thermal conductivity at 300 ° C. of 25 W / (m · K) or more and 52 W / (m · K) or less. And an alloy steel having a corrosion resistance to a molten metal, a thermal conductivity at 300 ° C. of 10 W / (m · K) or more and 25 W / (m · K) or less, and a thickness of 1
mm or more and 5 mm or less, and an inner cylinder part metallurgically joined to the outer cylinder part.

Preferably, the inner cylindrical portion is made of SUS630
Or SUS631 (JIS G4305, 1991)
And a nitriding treatment is applied to the inner diameter surface thereof.

[0018] Alternatively, the inner cylinder portion may be C: 0.1 to
0.5 wt%, Si: 3 to 7 wt%, Ni: 5 to 18 w
t%, Cr: 0.5 to 8 wt%, the balance being composed of an alloy steel substantially composed of Fe, and the inner diameter surface thereof is subjected to nitriding treatment.

More preferably, the inner diameter of the inner cylinder portion is
It is composed of a diffusion layer of metal carbide, metal nitride and nitrogen.

In the plunger sleeve for a die casting machine of the present invention, the thickness of the inner cylindrical portion made of an alloy steel having a relatively low thermal conductivity is set in an appropriate range, so that the heat retaining property and the heat resistance to the molten metal are maintained. In addition to having impact properties, damage due to overheating is less likely to occur in the falling part of the molten metal.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Example 1) A plunger sleeve for a die-casting machine having a two-layer structure in which an inner cylindrical portion is made of an alloy steel having corrosion resistance to a molten metal and having a relatively low thermal conductivity according to the following procedure. Created. In addition, in order to perform a comparative test (described later) of the heat retaining performance of the plunger sleeve, as shown in Table 1, samples were prepared by changing the thickness of the inner cylindrical portion at six levels from 1 mm to 6 mm.

(A) First, the outer cylinder portion 11 is connected to the SCM440
It was manufactured by machining using the dimensions shown in FIG. 1 using (JIS G 4105). The outer diameter of the outer cylinder portion 11 before finishing is 125 mm, and the inner diameter is a value D1 (tolerance: +0.1 to +0.2 mm) of six levels shown in Table 1. Also,
The thermal conductivity of SCM440 at 300 ° C. is 41.8 W
/ (M · K).

(B) Next, the columnar member 12 (the portion which will later become the inner cylindrical portion) is SUS630 subjected to solution treatment.
Using JIS G 4305, it was manufactured by machining with the dimensions shown in FIG. The outer diameter of the columnar member 12 is a value D1 (tolerance: -0.1 to 0) of six levels shown in Table 1.
mm). Table 1 Dimensions of each sample −−−−−−−−−−−−−−−−−−−−−−−− Sample Target thickness of the inner cylinder part Inner diameter of the outer cylinder part No. T (mm) D1 (mm)----------------------------------------------------------------------------------------------------------------------------------------------- 0.0 84 6 6.0 86 (c) As shown in FIG. Part 11 is housed therein, and further, a cylindrical member 12
Was inserted.

(2) As shown in FIG.
After covering the lid 3 with the lid 14, the gap between the HIP enclosing can 13 and the lid 14 was sealed by welding. Note that a vacuum pipe 15 is attached to the lid 14 in advance.

(E) While the evacuation was being performed, the evacuation pipe 15 was crushed and sealed by welding.

(F) HIP device (Hot isostatic pressing device)
The whole was heated to 1100 ° C. under 1000 atm, and the outer cylinder 11 and the cylindrical member 12 were integrally joined.

(G) After the HIP, the encapsulating can 13 for HIP was cut and removed, and then machined into the shape shown in FIG. 5 to form the inner cylindrical portion 19 and finish the outer cylindrical portion 11.

(H) The inner surface of the inner cylinder portion 19 was subjected to a nitriding treatment. At this time, by adjusting the nitriding temperature and the holding time, the age hardening of the SUS630 material forming the inner cylindrical portion 19 was also performed at the same time. The Vickers hardness Hv of the surface subjected to the nitriding treatment was about 1,000.

(I) Finally, the inner surface of the inner cylindrical portion 19 was subjected to honing to complete the plunger sleeve.

Prior to the nitriding treatment (h), carbonization is performed on the inner surface of the inner cylindrical portion 19 to diffuse carbon, and preferably, thereafter, quenching is performed to form granular carbides, and then the nitriding treatment is performed. , The hardness of the surface can be further increased. Thereby, wear resistance can be further improved.

(Example 2) (a) First, the outer cylinder portion 11 is connected to the SCM440 (JIS G).
4105), and was manufactured by machining with dimensions shown in FIG. The outer diameter of the outer cylinder portion 11 before finishing is 1
25 mm, inner diameter 80 mm (tolerance: +0.1 to +0.
2 mm).

(B) Next, the columnar member 12 (the portion which will later become the inner cylinder) is made of SUS630 subjected to solution treatment.
Using JIS G 4305, it was manufactured by machining with the dimensions shown in FIG. The outer diameter of the cylindrical member 12 is 80 mm (tolerance: -0.1 to 0 mm).

(C) After the surfaces of the outer cylindrical portion 11 and the cylindrical member 12 are degreased and the cylindrical member 12 is inserted into the outer cylindrical portion 11, the boundary between the outer cylindrical portion 11 and the cylindrical member 12 at both end surfaces. Was sealed by electron beam welding.

(2) Then, the whole is heated to 1100 at 1000 atm by using a HIP device (hot isostatic pressing device).
C., and the outer cylinder part 11 and the cylindrical member 12 were integrally joined.

(E) Next, the inner cylinder 19 was formed and the outer cylinder 11 was finished by machining the shape shown in FIG.

(G) The inner surface of the inner cylinder portion 19 was subjected to a nitriding treatment. At this time, by adjusting the nitriding temperature and the holding time, the age hardening of the SUS630 material constituting the inner cylindrical portion was simultaneously performed. The Vickers hardness Hv of the nitrified surface was about 1000.

(H) Finally, the inner surface of the inner cylindrical portion 19 was subjected to honing to complete the plunger sleeve.

(Example 3) (a) First, the outer cylindrical portion 11 is set to the size shown in FIG.
It was manufactured by machining using 440 (JIS G4105). The outer diameter of the outer cylinder portion 11 before finishing is 12
5 mm, inner diameter is 80 mm (tolerance: +0.1 to +0.2
mm).

(B) Next, the columnar member 12 (the part which will later become the inner cylinder) is prepared by adding 0.4 wt% of C and 5 wt% of Si.
%, Ni: 11% by weight, Cr: 6% by weight, and the balance was substantially Fe, and was manufactured by machining with dimensions shown in FIG. 7 using a forged material having a low thermal conductivity. The outer diameter of the cylindrical member 12 is 80 mm (tolerance:-
0.1 to 0 mm).

Thereafter, a plunger sleeve was manufactured in the same procedure as that shown in Example 1 above. At this time, the hardness Hv of the surface of the inner cylindrical portion after the nitriding treatment was 920.

(Results of Measuring Temperature of Molten Metal) Six types of plunger sleeves (sample Nos. 1 to 6) manufactured under the conditions of Example 1 described above and having different inner tube thicknesses (T).
Was incorporated into a cold-chamber die-casting machine to mold an aluminum alloy, and the temperature change of the molten metal after filling the plunger sleeve was measured.

FIG. 9 shows the result. FIG. 9 also shows, for comparison, the measurement results of the melt temperature when a plunger sleeve having a conventional structure is used. The plunger sleeve having the conventional structure used for comparison is a single layer of SUS630 (sample No.
11), SKD61 single layer (sample No. 12), inner tube part is SKD61 with 2.3 mm thickness and outer tube part is SUS63
0 (sample No. 13), and the inner cylinder part is SKD61 having a thickness of 1.0 mm and the outer cylinder part is SU
S630 (sample No. 1)
4).

From the results of measuring the temperature of the molten metal after filling shown in FIG. 9, the temperature of the molten metal between the filling and the injection of the molten metal (2 to 4 seconds) is determined by the comparison sample 13 (inner cylinder: SK).
D61, 2.3 mm thick), and the temperature of the molten metal after injection (after 4 seconds) is lower than the comparative sample 14 (inner cylinder: SKD61, 1.0 mm thick). The thing was a proper structure.

As a result, it was found that when the thickness of the inner cylindrical portion made of SUS630 is 1 mm or more and 5 mm or less, it falls within the above-mentioned appropriate range.

These plunger sleeves have an excellent heat retaining effect on the molten metal when the molten metal is filled, and have excellent cooling properties after injection, so that the temperature of the plunger sleeve does not rise too much, and it is compared with the conventional one. Long life.

(Results of Life Test etc.) Of the plunger sleeve samples shown in Example 1 above, sample No. 3
(Inner cylinder: SUS630, thickness 2.5mm, outer cylinder: S
CM440) and sample No. for comparison. 11 (S
US630 single layer) and sample No. 13 (Inner cylinder: SK
D61, thickness 2.3 mm, outer cylinder: SUS630)
It was mounted on a cold chamber die casting machine, and the motor housing was cast from an aluminum alloy. The conditions for die casting are as follows: material used: ADC 12, hot water temperature: 670 ° C., filling rate (ratio of molten metal in plunger sleeve): 45%.

As a result, the period until the plunger sleeve becomes unusable due to damage to the molten metal dropping portion is determined by the sample No. In 3, the number was about 160,000 shots. On the other hand, the sample No. 11 is approximately 130,000 shots, In 13 it was about 140,000 shots. Therefore, the sample No. No. 3 is sample No. Sample No. 11 has a longer life by about 20% than Sample No. 11. About 1 compared to 13
4% longer service life.

The percentage of non-defective products is determined by the sample No. 1
2% compared to Sample No. 1. 8% better than 13.

As described above, the plunger sleeve according to the present invention (Sample No. 3) showed a longer life than the single-layer plunger sleeve of SUS630 (Sample No. 11) because of the plunger sleeve itself. It is presumed to be caused by the difference in the amount of temperature rise.

That is, when the ultimate temperature of the plunger sleeve near the molten metal dropping portion was measured, it was 240 ° C. in the plunger sleeve according to the present invention, whereas it was SUS.
The temperature was 350 ° C. for the 630 single-layer plunger sleeve. It is considered that the SUS630 single-layer plunger sleeve has a higher temperature by about 100 ° C. than the plunger sleeve of the present invention, so that it easily reacts with the poured aluminum melt, so that the damage is accelerated. On the other hand, the plunger sleeve of the present invention is considered to have excellent heat dissipation and a long life because a material having low thermal conductivity is used only for the inner cylindrical portion.

Further, the temperature of the filled aluminum melt in the plunger sleeve (temperature 2 seconds after the start of filling)
Is that the plunger sleeve of the present invention is about 20 ° C. higher than the conventional plunger sleeve having a two-layer structure (sample No. 13) and is excellent in the heat retaining property for the filled molten metal, so that the yield rate is improved. Conceivable.

[0052]

The plunger sleeve of the present invention has corrosion resistance to the molten metal, has excellent heat retention for the filled molten metal, and has excellent heat radiation after injection of the molten metal. As a result, as compared with the plunger sleeve having the conventional structure, the life is longer and the yield of the product is higher.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a manufacturing process of a plunger sleeve based on the present invention.

FIG. 2 is a diagram illustrating an example of a manufacturing process of a plunger sleeve according to the present invention.

FIG. 3 is a diagram illustrating an example of a manufacturing process of a plunger sleeve based on the present invention.

FIG. 4 is a diagram illustrating an example of a manufacturing process of the plunger sleeve according to the present invention.

FIG. 5 is a diagram illustrating an example of a manufacturing process of the plunger sleeve according to the present invention.

FIG. 6 is a view for explaining another example of the manufacturing process of the plunger sleeve based on the present invention.

FIG. 7 is a view for explaining another example of the manufacturing process of the plunger sleeve according to the present invention.

FIG. 8 is a view for explaining another example of the manufacturing process of the plunger sleeve based on the present invention.

FIG. 9 is a diagram showing a measurement result of a molten metal temperature after the plunger sleeve is filled with the molten metal.

[Explanation of symbols]

 11 ... outer cylinder part, 12 ... cylindrical member, 13 ... sealing can for HIP, 14 ... lid, 15 ... vacuum pipe, 19 ... inner cylinder part.

Claims (4)

[Claims] 1. A thermal conductivity at 300 ° C. of 25 W /
An outer cylindrical portion made of a metal material having a value of not less than (mK) and not more than 52 W / (mK); and having corrosion resistance to molten metal, and having a thermal conductivity of not less than 10 W / (mK) and not more than 25 W / (m) at 300 ° C. · An inner cylinder part which is made of the following alloy steel, has a thickness of 1 mm or more and 5 mm or less, and is metallurgically joined to the outer cylinder part. Plunger sleeve. 2. The method according to claim 1, wherein the inner cylinder is SUS630 or SU.
The plunger sleeve for a die casting machine according to claim 1, wherein the plunger sleeve is a precipitation hardening stainless steel of S631 (JISG 4305), the inner surface of which is subjected to nitriding treatment. 3. The inner cylinder portion has a C content of 0.1 to 0.5 wt.
%, Si: 3 to 7 wt%, Ni: 5 to 18 wt%, C
The plunger sleeve for a die casting machine according to claim 1, wherein r: 0.5 to 8 wt%, alloy steel substantially consisting of Fe, the inner surface of which is subjected to nitriding treatment. . 4. The plunger for a die casting machine according to claim 2, wherein the inner cylindrical portion has an inner diameter surface formed of a diffusion layer of metal carbide, metal nitride and nitrogen. sleeve.