JP3260210B2 - Die casting injection sleeve and method of casting aluminum or aluminum alloy member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to aluminum (Al),
The present invention relates to an injection sleeve for die casting used for die-casting a molten metal such as an Al alloy and zinc (Zn).

[0002]

BACKGROUND ART Al, Al alloy, a molten metal, such as Zn were fed to an injection sleeve of the die casting apparatus, molten metal is injected into the die-casting mold at a high speed by a plunger tip, with the addition of high-pressure die-casting die in The solidification die-casting method is widely used in the manufacturing industry of automobiles, electric appliances and the like for the production of metal parts. The reason for this is that the time required to cast one product is significantly shorter than other casting methods, and the manufacturing cost is lower.

[0003] In the die casting method, die-casting equipment
The casting cycle, in which the molten metal is fed into the inside of the strike mold at a high flow rate and solidified, is completed in a very short time compared to other casting methods. , in particular in the injection sleeve and die-casting die, it is required material having heat shock resistance for excellent corrosion resistance and耐E <br/> b over John resistance and repeatedly subjected heating and cooling cycles to molten metal.

When casting Al or an Al alloy having a relatively high casting temperature, components such as an injection sleeve and a die casting mold are required to withstand extremely severe conditions. The material used is a material obtained by subjecting a hot die steel to heat treatment and further nitriding the surface.

[0005] In addition, there are considerable differences between the injection sleeve and the die casting mold in the conditions of contact with the molten metal. That is, when the temperature of the molten metal fed into the die casting mold decreases, the viscosity of the molten metal increases, and a part thereof is in a semi-solid state. Since products of tissue viscosity of the molten metal is increased or solidification phase is cast with or precipitates becomes inhomogeneous adversely affect the product properties, the injection sleeve it is necessary to avoid possible cooling of the molten metal, the other Daikasu
DOO mold should Ru that will be sufficiently cooled because at sites allowed to solidify molten metal therein.

[0006] The inner surface of the injection sleeve, especially the contact area near the lower part of the hot water supply port, comes into contact with the molten metal having a relatively high temperature, so that erosion is severe. The injection sleeve made of hot die steel is subjected to nitriding treatment. Even if it is used, its durability is short. However, no other remarkable material other than hot die steel has been found as a material for the injection sleeve.Hot die steel injection sleeves have been used while cooling the severely corroded parts as far as the injection sleeve allows. That is the current situation.

In addition, the plunger tip (a piston-like member whose surface is overlaid with a cormorroy alloy and whose inside is water-cooled) is rapidly moved in the injection sleeve to form a die.
Since the molten metal must be pressed into the casting mold in a short time, sufficient lubricity must be maintained between the inner surface of the injection sleeve and the plunger tip. Also in this respect, there is a problem with the injection sleeve of hot die steel, and it is necessary to supply about 10 ml of a lubricant obtained by mixing water or the like with carbon every time casting is performed. This lubricant is thermally decomposed into gas by the heat of the molten metal, and this gas is taken into the molten metal and causes pores to remain in the cast product.

In recent years, for the purpose of solving these problems, ceramics having essentially high corrosion resistance to molten metal and high thermal shock resistance due to a small coefficient of thermal expansion, for example, sialon disclosed in JP-A-63-72464. To
Japanese Patent Publication No. 60-2949 discloses an attempt to use silicon nitride for an injection sleeve for die casting.

[0009] However, the sleeve toughness and thermal shock resistance of these ceramic is sufficiently without be reinforced by fitting the ceramic sleeve to the metal cylinder, the thermal expansion coefficient (3 to 4 × 10 ^{- 6} / ° C.) thermal expansion coefficient of gold genus cylinder made (as in ^{SKD-61, 13~14 × 10 -6} /
° C.) than was hardly obtained reinforcing effect in significantly smaller since the working temperature range, or used condition limitations, there is a problem to be damaged by a mechanical shock or thermal shock during use, not put to practical use stages.

[0010] Soviet Powder Metal
lurgy and MetalCeramics N
o. 8 (44) P665-670, 1966 and Japanese Patent Application Laid-Open No. 62-196353 propose a cermet sintered body using a Mo-Ni double boride as a hard phase and a Ni-based alloy as a binder phase. . It is stated that if Cr is further added to the cermet sintered body of this system, the chemical corrosion resistance and oxidation resistance of the cermet sintered body are improved.

The present inventors have disclosed in Japanese Patent Application Laid-Open No. 63-143236.
A hard phase mainly composed of a Ni-Mo double boride, a Ni-W double boride or a Ni-Mo-W double boride;
We have proposed a cermet sintered body composed of a Ni-Mo based alloy and a metal binder phase, and show that the material has higher strength and hardness at high temperatures than WC-Co based cemented carbide. Was. Japanese Patent Application Laid-Open No. 1-131070 proposes a cermet sintered body of this type to which a carbide is added in order to improve the strength and hardness at high temperatures.

Further, the present inventors have disclosed in Japanese Patent Laid-Open No. 2-299.
In 740, a specific application of these sintered cermet, proposes die-casting die for die-casting a molten metal such as Al and Zn (which is cooled).

However, whether or not this type of cermet sintered body can be used as an injection sleeve for aluminum used under more severe conditions depends on whether this cermet sintered body is N
Since it contains a metal binder phase containing i as a main component, and this metal binder phase is relatively reactive with molten aluminum or the like and is considered to have low corrosion resistance, the adaptability when cooling is not effective was unknown.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to find a material capable of solving the above-mentioned problems and to provide an injection sleeve for die casting having excellent durability.

[0015]

The invention SUMMARY OF THE INVENTION has been made in order to achieve the above object, die casting injection sleeve of the invention, complex boride of Ni and Mo, complex boride of Ni and W, as well as Ni, from complex boride of Mo and W
A hard phase mainly composed of at least one selected from the group consisting of
A cylindrical cermet sintered body composed mainly of a metal binder phase composed of a Ni alloy in which Mo is dissolved in solid, and the content of the hard phase of the cermet sintered body is 50% by weight or more and 90% by weight or less. It is characterized by being.

The injection sleeve according to the present invention can be made of Mo, W, Ni, MoB, WB, or Mo as described in JP-A-63-143236 or JP-A-4-28840.
Ni-B alloy, double boride of Ni and Mo, double boride of Ni and W, Ta, Nb, Cr, Co, TaB ₂ , N
The required dimensions are obtained by mixing, pulverizing, molding, and sintering a cermet sintered body using powders such as bB ₂ , WC, and TiC as starting materials, followed by grinding with a diamond grindstone, electric discharge machining, and press-fitting into a metal cylinder. It is made by finishing to composition.

Among the components of these cermet sintered bodies,
Ta and Nb have the effect of increasing the strength, toughness and corrosion resistance of the cermet sintered body, Co has the effect of increasing the toughness and high-temperature strength of the cermet sintered body, and carbides such as WC and TiC are used for the cermet sintered body. Cr has the effect of increasing the strength and hardness, and Cr has the effect of increasing the oxidation resistance of the cermet sintered body. Preferred amounts of these components to be added to the raw materials are 8 to 15% by weight of Cr and Co, 2 to 8% by weight of Ta, 1 to 5% by weight of Nb, and 0.5 to 15% by weight of carbide.
It is. When the addition amount of these components is small, the effect of improving the material properties of the cermet sintered body is hardly obtained, and when too much is added, an undesirable phase is generated and the toughness of the cermet sintered body is reduced. Prone.

[0018] The organization of the cermet sintered body of this system, Fuku硼
Hard particles of the hard phase consisting of product is not a state of being surrounded by the metal bonding phase, the cross-sectional surface is a polygon
The average particle size of the crystal grains of the phase is, for example, about 5 μm, and the thickness of the metal binding phase separating the hard phase is usually 5 μm.
It is as follows.

In the injection sleeve for die casting of the present invention,
By using a cermet sintered body of a specific material, the service life of the injection sleeve is significantly prolonged without using cooling, as compared with the case of using an injection sleeve using conventional hot die steel. Further, by using the injection sleeve for die casting of the present invention, a desirable effect which was not initially expected can be obtained as described later, and the durability of the injection sleeve is excellent, and the quality of the product to be die-cast is remarkably improved. Be improved.

The hard phase of these double borides has excellent corrosion resistance to molten metal such as Al as compared with the metal bonded phase, while the metal bonded phase has lower corrosion resistance to the molten metal. . The reason why the amount of double boride contained in the cermet sintered body is 50% by weight or more is because the hard phase of double boride is contained in 50% by weight or more and SKD6 is contained.
This is because it has excellent corrosion resistance as compared with hot die steels such as 1 (JIS standard), and can significantly extend the service life of the injection sleeve. However, when the content of the hard phase composed of double boride of the cermet sintered body exceeds 90% by weight, the cermet sintered body becomes brittle and cracks are formed in the injection sleeve due to thermal shock when casting aluminum or the like. It is easy to occur.

Considering the corrosion resistance and high-temperature strength of the cermet sintered body that determines the service life of the injection sleeve, the content of the hard phase in the cermet sintered body is preferably Is 65% by weight
Not less than 80% by weight, more preferably not less than 70% by weight 8
0% by weight or less.

The metal bonding phase is a Ni alloy in which Mo or the like is mainly dissolved in Ni, and the hard phase of the double boride dissolves in the Ni alloy to some extent in a high temperature region where sintering is performed. The wettability between the hard phase composed of boride and the metal binding phase is good, and the interface strength between the hard phase and the metal binding phase when a cermet sintered body is formed is large.

If Mo is dissolved in the Ni alloy, the cermet sintered body has high corrosion resistance to the molten metal. However, if the content of Mo is too large, Mo which is not dissolved in the Ni alloy may precipitate as an intermetallic compound and deteriorate the material properties. Therefore, the amount of Mo dissolved in the Ni alloy is set to 10% by weight or more and 30% by weight or less, more preferably 15% by weight or more and 25% by weight or less. Strength of sintered body,
Hardness and corrosion resistance to the molten metal are ensured, and there is no generation of an intermetallic compound which causes deterioration of material properties due to the interaction of excess metal during sintering.

The weight percentage of the hard phase in the cermet sintered body is
It can be obtained by approximate calculation assuming that all boron components are incorporated in the double boride. In addition, by observing the cross section of the cermet sintered body with an SEM, the ratio of the area of the hard phase appearing on the surface is obtained. Can be calculated. The specific gravities of the hard phase and the metal binding phase vary to some extent depending on their chemical compositions, but are generally about volume% ≒ weight%.

Further, when such an injection sleeve made of a cermet sintered body is used for casting molten metal, carbon particles and Al oxides derived from a lubricant supplied to the injection sleeve in the early stage of its use cause the cermet to be oxidized. In addition to the wear of the metal binder phase on the surface of the sintered body, the metal binder phase is selectively eroded by a molten metal such as aluminum and eroded to a depth of about 1 μm. However, the depth of the erosion is shallow compared to the size of the hard phase particles,
The crystal grains of the hard phase do not fall off the surface of the cermet sintered body.

Thereafter, even if the casting of the molten metal is repeated,
Since the molten metal has a certain degree of viscosity and may not be easily wet with the hard phase on the surface, the erosion of the metal binder phase at a position recessed from the surface is remarkably slow, and it is excellent without cooling the injection sleeve. Shows durability.

Further, it has been recognized that the sliding between the plunger tip and the plunger tip at the operating temperature does not involve the metal bonding phase for the above-mentioned reason, and the sliding resistance of the injection sleeve is remarkably reduced. This is considered to be due to the fact that the hard phase of the cermet sintered body is a double boride.

When die casting of Al or an Al alloy is performed by using a conventional hot die steel injection sleeve, the heat conductivity of the hot die steel is considerably large and the hot die steel is partially cooled. At the contact surface with the injection sleeve, the temperature of the molten metal decreases and a part of the molten metal solidifies, causing a so-called broken chill layer in the casting structure of the cast product, which causes the mechanical properties of the cast product to deteriorate. I was

Further, when the temperature of the molten metal decreases, the viscosity of the molten metal necessarily increases, and the flow rate of the molten metal injected into the die casting mold decreases. As a result, the filling density of the molten metal in the corners of the die casting mold becomes small, the time required for pouring becomes longer, the cooling rate of the cast molten metal decreases, and the metal structure of the cast product becomes coarse. As a result, the material properties of the cast product were not as good as expected because of dendritic crystal structure.

Using the injection sleeve according to the invention,
Regarding these problems, the following remarkable improvement effects can be obtained. That is, the double boride constituting the hard phase of the cermet sintered body is characterized in that it is hardly wetted by the molten metal to be cast, and the position where the molten metal recedes from the surface when no pressure is applied to the molten metal. Is not in contact with the metal binding phase. When pressure is not applied to the molten metal, the molten metal is not in close contact with the entire surface of the injection sleeve, and the heat transfer area is small, so that the cooling of the molten metal introduced into the interior of the injection sleeve is difficult to progress. Can be

The heat conductivity (unit: cal / cm · sec · ° C.) of the hot die steel (SKD61) is 2
0.073 at 0 ° C and 0.073 at 600 ° C.
068, whereas in the example of the cermet sintered body used for the injection sleeve of the present invention, each is 0.032.
Because if that has become a 0.050, which is is difficult to proceed cooling of the molten metal from this point.

[0032] Thus, small molten metal temperature of high viscosity is injected at high speed inside the die-casting die, the die ranged pressure of the plunger tip to the corner of the die-casting die
The molten metal is filled into the casting mold without gaps, solidification is completed in a short time, and the amount of lubricant used can be reduced, so that the crystal structure of the cast product becomes fine and dense, Many problems associated with the use of conventional injection sleeves, such as residual layers and porosity, are simultaneously solved, and the properties of the cast product are significantly improved.

The injection sleeve does not need to be made entirely of this cermet sintered body. If the metal cylinder is fitted to the outer periphery of the cylindrical cermet sintered body by shrink fitting or the like, the injection sleeve can be made more inexpensive. The sleeve can be manufactured and shrink-fitted to apply a compressive stress from the outer periphery, so that the practical use strength of the sleeve can be further increased. In this case, the difference between the coefficient of thermal expansion of the cermet sintered body (8.5 to 9 × 10 ⁻⁶ / ° C.) and the coefficient of thermal expansion of the metal cylinder is determined by the aforementioned ceramic and metal.
Because not as large as the difference between, the reinforcing effect of the shrink fitting is sufficiently effective in operating temperature of the sleeve.

Further, since the hard phase of the double boride has excellent corrosion resistance to the molten metal, when hot erosion, that is, high temperature molten metal is fed into the injection sleeve,
The service life of the injection sleeve can be further improved by increasing the content of the hard phase in the portion that first comes into contact with the molten metal.

As a specific method for producing such an injection sleeve, for example, when a cylinder is formed by isostatic pressing, a surface of a part of a core mold is coated with a raw material powder having a high content of a hard phase. Then, a normal raw material powder is filled into a rubber mold and molded to obtain a molded body in which a coating layer having many hard phases is integrated with the inner surface side of the cylinder. Further, by applying a coating having a different hard phase content to the surface of the core mold a plurality of times, a sleeve having a hard phase content can be obtained.

At the portion where the cylindrical injection sleeve of the cermet sintered body comes into contact with the die-casting mold, the injection sleeve must be firmly pressed and fixed, and the corner is likely to be chipped. However, since this part loses heat to the side of the die-casting mold (which makes cooling effective), the erosion is moderate, and the content of the hard phase in this part is reduced to the content of other hard phases. By reducing the amount to be less than the amount, that is, by increasing the content of the metal bonding layer in this portion to increase the toughness, the problem of corner chipping can be avoided.

The injection sleeve of the present invention having such a configuration can also be manufactured by the above-described isostatic press, and a separately manufactured ring-shaped cermet sintered body may be diffusion-bonded. Also, as another expedient, a ring of hot die steel may be placed in this part.

In another preferred injection sleeve for die casting of the present invention , a cylindrical cermet sintered body is provided with a tapered portion on an outer periphery at an end portion in contact with a die casting mold ,
Metal cylinder is fitted with the tapered portion, the injection Three
At the other end of the probe, the cylindrical cermet sintered body is fixed so as not to come out <br/> by a metal ring attached to a metal circular cylinder.

[0039] By nearby contacting the die-casting die of the injection sleeve is shrink-fitted by the tapered section, to consist of all the inner surface sintered cermet of the injection sleeve to the portion which contacts the die-casting die of the injection sleeve Thus, good durability of the injection sleeve can be ensured. Further, when shrink-fitting with a metal having a higher coefficient of thermal expansion and a smaller Young's modulus than the cermet sintered body, the cylindrical cermet sintered body may partially protrude due to residual stress accompanying shrink-fitting.

[0040] Therefore, although the cylindrical sintered cermet there is a risk of missing corner exits from the injection sleeve, metal ring on the plunger tip side of the injection sleeve is threaded
It is attached by a stop or welding and has a cylindrical shape.
By preparative sintered body is fixed so as not come off, a cylindrical sintered cermet does not protrude from the metal cylinder, the risk of edge defects is eliminated. Further, if a longitudinal compressive stress is applied to the cermet sintered body having lower toughness than the metal material, the cylindrical cermet sintered body is further reinforced.

In the die casting apparatus incorporating the injection sleeve of the present invention, particularly favorable effects can be obtained when casting Al or an Al alloy. That is, when casting Al or an Al alloy, since the temperature of the molten metal supplied to the injection sleeve is as high as 650 ° C. to 720 ° C., the portion of the injection sleeve below the hot water supply port that comes into contact with the molten metal first is melted. Metals undergo severe erosion and thermal shock.

However, the injection sleeve of the present invention can withstand such severe conditions without cooling or the like and shows good durability. Thus, the temperature of the molten metal fed into the die casting mold can be kept at an appropriate temperature, and the molten metal is fed at high speed to every corner of the die casting mold and solidified in a short time, so the quality of the metal parts to be cast Is significantly improved.

[0043]

EXAMPLES Specific examples of the injection sleeve according to the invention will be described below, but the present invention the following exemplary I in Tsu <br/> limited constant of Lena are in the Examples.

Test Example 1 53% by weight of MoB, 7% by weight of WB, 33% by weight of Ni and 7% by weight of Mo were weighed, and ethyl alcohol was added as a dispersion medium to these powders, and the mixture was placed in a pot mill. After crushing and drying under reduced pressure, a cylinder molded by an isostatic press is sintered at 1300 ° C., sintered and ground to form a cylindrical cermet sintered body having an inner diameter of 60 mm, an outer diameter of 70 mm and a length of 250 mm. Body. The cermet sintered body sample produced simultaneously with the present cermet sintered body from the same raw material had a hard phase content of 72% by weight, a bending strength of 210 kg / mm ² , and a fracture toughness of 17 MN / m ^3/2 . .

A cylinder of hot die steel was shrink-fitted on the outer periphery of the cylindrical cermet sintered body to obtain an injection sleeve.
A hot water inlet having an inner diameter of about 50 mm was provided on the peripheral surface of the injection sleeve. As shown in the cross-sectional view of FIG. 1, this injection sleeve was assembled into a 250-ton die casting apparatus,
Die casting of an Al alloy (ADC12) was performed at a casting interval of 28 seconds. The cast product is 3mm x 30mm x 6
It is a flat plate with a groove of 0 mm.

In this test, the temperature of the molten Al alloy supplied was 680 ° C., and the amount of the supplied molten metal was about 70 ° C.
0 g / time, the injection speed was 2.5 m / min, the supply amount of the lubricant (water containing carbon) was 3 ml / time, and the water cooling of the lower part of the hot water supply port, which is performed by the conventional injection sleeve, was not performed.
Life of the injection sleeve is about 33 million times, this time
Then, the inside of the sleeve just below the hot water supply hole is dented by erosion,
Plunger tip movement is no longer smooth .

In FIG. 1, 1 is an injection sleeve, 2 is a cylindrical cermet sintered body, 3 is a metal cylinder, 4 is a die sleeve of hot die steel, 5 is a plunger tip, 6 is a die casting die, 7 Is a hot water outlet.

Test Example 2 Using an injection sleeve made of a conventional nitriding-treated hot die steel (SKD61), die casting was performed under the same conditions as in Example 1. However, in this example, casting was performed while water cooling was applied to the lower part of the hot water supply port.

The density of about 100 3 mm × 30 mm × 60 mm grooved flat plates die-cast in Test Examples 1 and 2 and the bending strength of the test pieces cut from these flat plates (assuming that the cast product does not elastically deform) Was measured, and the cumulative distribution of the density of the cast product was compared with the ratio of the test piece remaining without breaking when the bending stress was applied (remaining probability),
FIGS. 2 and 3 are graphs, respectively. From these graphs, by using the injection sleeve of the present invention,
It can be seen that the properties (density and flexural strength) of the cast product are significantly improved. The injection sleeve of Test Example 2 was unusable because the inside of the injection sleeve was eroded, and its service life was about 120,000 times.

Test Examples 3 to 10 In the same manner as in Test Example 1, an injection sleeve made of a cylindrical sintered cermet having the composition shown in Table 1 was prepared and subjected to a casting test. Table 1 also shows the content of the hard phase, the bending strength, the fracture toughness, and the service life of the injection sleeve of the cermet sintered body.

Test Example 11 Using a conventional hot die steel injection sleeve as described above, a casting test was performed without cooling the first part of the molten metal. 4
It took 200 times.

The reasons why the injection sleeve could not be used continuously were as described in Test Examples 3, 4, 6, 8, 9, 10, and 11.
In Example 5 and Example 7, cracks occurred in the injection sleeve when the casting was temporarily restarted after the casting was temporarily stopped.

FIG. 4 is a sectional view showing another example of the injection sleeve for die casting of the present invention. In FIG. 4, reference numeral 8 denotes a metal ring, 9 denotes a tapered portion, and 10 denotes welding. In this example, since a part of the cylindrical cermet sintered body does not come out of the metal cylinder by fitting and shrink fitting with the metal ring and the tapered portion, troubles such as corner chipping do not occur. No.

[0054]

[Table 1]

[0055]

According to the injection sleeve of the present invention, since the cermet sintered body has excellent corrosion resistance to molten metal and high strength at high temperatures, the service life of the injection sleeve can be greatly extended without cooling the hot metal. Can be. This effect is facilitated by shrink fitting of the metal cylinder. Furthermore, since the sliding resistance between the injection sleeve and the plunger tip is small, the amount of lubricant used to introduce air bubbles into the product can be significantly reduced.

Further, the cooling rate through the cermet sintered body constituting the injection sleeve is lower than that of the conventional hot die steel, and the cooling of the injection sleeve can be omitted, so that the temperature of the molten metal is adjusted to an appropriate temperature. The molten metal can be pressed all the way to the corners of the die casting mold while maintaining the appropriate temperature in a short time, and the cooling and solidification is completed in a short time.
Thus, these combined effects can significantly improve the properties of the die cast product.

Therefore, when the injection sleeve according to the present invention is used, the service life of the injection sleeve is extended, so that the operation rate of the die casting device can be increased, and the yield of the product is improved by reducing defects in the product to be cast. At the same time, the quality of the product is significantly improved. In the production of metal parts, since die casting is becoming more and more popular in the future, its industrial utility value is enormous.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a situation in which an injection sleeve for die casting of the present invention is attached to a die casting device.

FIG. 2 is a graph showing a cumulative frequency distribution of the density of a cast product obtained by using the injection sleeve for die casting of the present invention and a conventional injection sleeve for die casting.

FIG. 3 is a graph showing a probability of remaining bending strength of a cast product obtained by using the injection sleeve for die casting of the present invention and a conventional injection sleeve for die casting.

FIG. 4 is a sectional view showing another example of the injection sleeve for die casting of the present invention.

[Explanation of symbols]

 1: Injection sleeve 2: Cylindrical cermet sintered body 3: Metal cylinder 4: Hot die steel die sleeve 5: Plunger tip 6: Die casting mold 7: Hot water supply port 8: Metal ring 9: Tapered section 10 :welding

Claims (3)

(57) [Claims] 1. A double boride of Ni and Mo, Ni and W
And a hard phase mainly composed of one or more selected from the group consisting of double borides of Ni, Mo and W, and a metal binding phase composed of a Ni alloy in which Mo is mainly dissolved in Ni. An injection sleeve for die casting, comprising a cylindrical cermet sintered body to be produced, wherein the hard phase content of the cermet sintered body is 50% by weight or more and 90% by weight or less. 2. The injection sleeve for die casting according to claim 1, wherein a metal cylinder is fitted around the outer periphery of the cylindrical cermet sintered body. 3. A method of casting aluminum or aluminum alloy member, characterized by casting by claim 2 Symbol mounting die casting apparatus for die casting injection sleeve is incorporated in.