JP2002161319A - Cylinder for molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder for a molding machine with a superior workability and economical efficiency as well as a superior wear resistance and corrosion resistance, by increasing volume occupation rate of hard particles in a lining layer. SOLUTION: The cylinder for the molding machine, which is provided with the lining layer containing a wear resistant and corrosion resistant alloy on the inner surface of the hollow and cylindrical base material, is characterized by that granulated grains consisting of hard particles bonded by metal are dispersed in the lining layer. The granulated grain has a higher specific gravity than that of the wear resistant and corrosion resistant alloy, and has a spherical shape with an average diameter of 30-300 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder having a composite structure in which a lining layer is formed on the inner surface of a hollow cylindrical cylinder base material, which is mainly used for a plastic molding machine.

[0002]

2. Description of the Related Art A cylinder for a molding machine used for molding a plastic product or the like is a hollow cylindrical cylinder base material made of steel in order to prevent corrosion caused by a resin or an additive added to the resin during hot molding. A lining layer made of an alloy having abrasion resistance and corrosion resistance (hereinafter, referred to as a wear-resistant and corrosion-resistant alloy) is formed on the inner surface of the substrate. As a method for forming a lining layer made of a wear-resistant and corrosion-resistant alloy on the inner surface of the cylinder base material, a centrifugal casting method, a hot isostatic sintering method, a shrink fitting method, or the like is adopted.

As a wear-resistant and corrosion-resistant alloy forming a lining layer, a nickel-based alloy, a cobalt-based alloy or the like is used. In addition, tungsten carbide (WC) and niobium carbide (Nb) which are hard particles are added to these wear-resistant and corrosion-resistant alloys.
A lining layer further improved in wear resistance by dispersing C), titanium carbide (TiC) or the like by a centrifugal casting method has also been proposed.

For example, Japanese Patent Application Laid-Open No. Hei 7-290186 discloses that, in terms of% by weight, tungsten carbide: 30 to 45%, nickel + cobalt: 35 to 50%, molybdenum: 1% or less, chromium: 10% or less, boron: 1 ~ 3%, silicon: 1 ~
3%, manganese: 2% or less, iron: 8 to 25%, carbon: 1
% Of tungsten carbide composite lining material for centrifugal casting. According to the publication, tungsten carbide is composed of spherical powder having an average particle diameter of 6 to 12 μm, and the volume ratio of tungsten carbide in the lining layer is 25 to 45.
% Of the molding machine cylinder lining material. Further, it is described that the shape of tungsten carbide is changed from a pulverized square shape to a spherical shape, thereby preventing a mating material from being damaged by metal friction.

FIG. 3 is a conventional example, and shows a structure photograph in which single particles of tungsten carbide having a square shape as hard particles are dispersed in a nickel-based wear-resistant and corrosion-resistant alloy by 30% by volume. The lining layer on the inner peripheral surface of the cylinder is formed with a certain machining allowance in anticipation of casting defects or the like generated on the inner peripheral surface of the lining layer during centrifugal casting. afterwards,
Unnecessary inner diameter portions of the lining layer are removed by machining to have a predetermined inner diameter.

[0006]

A conventional cylinder for molding machines in which 30 to 45% by volume of hard particles are dispersed in an abrasion-resistant and corrosion-resistant alloy has good abrasion resistance. In applications where molding conditions are more stringent, such as molding of difficult-to-mold materials to which glass fibers or the like are added, further improvement in wear resistance has been required. for that purpose,
It is sufficient to increase the content of the hard particles, and as one means, it is conceivable to increase the particle size of the hard particles. However, in this case, there is a problem that the inner diameter processing becomes difficult, and a long time is required for the processing, and the economic efficiency is deteriorated. Accordingly, an object of the present invention is to provide a cylinder for a molding machine which is excellent in wear resistance and corrosion resistance by increasing the volume ratio of hard particles in a lining layer, and is excellent in workability and economy.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a cylinder for a molding machine in which a lining layer containing a wear-resistant and corrosion-resistant alloy is formed on the inner surface of a hollow cylindrical cylinder base material. Characterized in that the granulated powder bound by the above is dispersed. The present invention is characterized in that the granulated powder has a higher specific gravity than the wear-resistant and corrosion-resistant alloy. The granulated powder is a spherical particle having an average particle diameter of 30 to 300 μm. The volume ratio of the granulated powder in the lining layer is 50 to 70%. The difference of the volume ratio of the granulated powder in the lining layer in the axial direction is within 10%. The granulated powder is characterized by containing tungsten carbide powder as hard particles. The granulated powder is characterized by combining tungsten carbide powder with cobalt. The wear-resistant and corrosion-resistant alloy is made of a nickel-based alloy. The granulated powder is dispersed in the lining layer by a centrifugal casting method.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, granulated powder in which hard particles are firmly bound with a metal as a binder is dispersed in a lining layer containing a wear-resistant and corrosion-resistant alloy. In the granulated powder in which the hard particles are bonded with a metal as a binder, simple hard particles are uniformly dispersed in the granulated powder in advance. As the metal serving as the binder, a metal having a high melting point that does not dissolve in the molten metal of the wear-resistant and corrosion-resistant alloy is used. Further, the specific gravity of the granulated powder is made larger than the specific gravity of the wear-resistant and corrosion-resistant alloy. If the granulated powder thus configured is added to the abrasion-resistant and corrosion-resistant alloy melt forming the lining layer and subjected to centrifugal casting, the centrifugal force causes the granulated powder of the present invention to become an inner peripheral surface of the cylinder base material. It is filled unevenly on the side (deep part of the lining layer). As a result, hard particles hardly exist in the machining allowance on the inner peripheral surface of the lining layer, and the inner diameter can be easily processed. After processing, the hard particles in the granulated powder are uniformly and densely dispersed in the lining layer. It will be in the state of having done.

[0009] The shape of the granulated powder of the present invention is preferably spherical. When the granulated powder is spherical, it is possible to prevent the mating material from being damaged by friction between the cylinder and a molding material such as a plastic resin or a screw. Further, when the horn-like granulated powder is to be dispersed densely in the wear-resistant and corrosion-resistant alloy by the centrifugal casting method, the horn-shaped granulated powder is likely to be in a crosslinked state. If this cross-linking occurs on the surface of the lining layer, a portion where only the alloy matrix is distributed tends to occur on the surface of the lining layer. It is considered that the wear resistance of the lining layer is lowered because the alloy matrix of the crosslinked portion is softer than the hard particles and is preferentially worn by contact with the resin. On the other hand, when the granulated powder is made spherical, the granulated powder can be uniformly dispersed in the lining layer, so that the rate of occurrence of the above-mentioned crosslinking decreases.

[0010] Further, as for the effect of making the granulated powder spheroid, it is considered that casting defects occur less when the granulated powder is made spherical than when it is square. The reason is that when the wear-resistant and corrosion-resistant alloy solidifies after centrifugal casting, solidification starts from the boundary side of the cylinder base material. When changing from a liquid to a solid, shrinkage occurs and casting defects (shrinkage cavities) occur around the granulated powder, but since the inner surface side of the wear-resistant and corrosion-resistant alloy is still liquid, this liquid phase Becomes hot water and fills this defective part. However, when the granulated powder is angular, the centrifugal casting tends to cause the angular granulated powder to be dense without gaps.
For this reason, it becomes difficult for the molten metal of the wear-resistant and corrosion-resistant alloy to enter between the granulated powders in which the horn-shaped granulated powders are densely packed, so that casting defects are likely to occur. On the other hand, if the granulated powder is spherical, even if the granulated powder is densely packed with the wear-resistant and corrosion-resistant alloy, a gap is always formed between the granulated powders. Is reliably performed, so that casting defects do not occur. In addition, when the hard particles are angular, since there is a corner, in consideration of the wettability with the wear-resistant and corrosion-resistant alloy, it becomes difficult for the molten metal of the wear-resistant and corrosion-resistant alloy to exceed the corner, and more casting defects occur. It is thought that it becomes easy to do.

The granulated powder of the present invention has an average particle size of 30 to
Preferably it is 300 μm. Average particle size is 30μm
If it is smaller, the granulated powder cannot be densely dispersed in the lining layer. If the average particle size is larger than 300 μm, the gap between the granulated powder and the granulated powder in the lining layer becomes too large, resulting in wear resistance and corrosion resistance. This is because the ratio of the area where only the alloy matrix is exposed on the surface tends to increase, and as a result, the wear resistance and corrosion resistance deteriorate. Desirably, the average particle size of the granulated powder dispersed in the lining layer is 50 to 150 μm.

The hard particles constituting the granulated powder include tungsten carbide, titanium carbide, niobium carbide, vanadium carbide, carbide of molybdenum, boride or silicide of tungsten or molybdenum, or a mixture of one or more of these. Hard particles can be used. Then, these hard particles are combined with a metal such as cobalt as a binder to form granulated powder. The content of a metal such as cobalt as a binder in the granulated powder is preferably 5 to 10% by weight. In the present invention, it is desirable to include tungsten carbide powder as hard particles. When tungsten carbide hard particles are used, the tungsten carbide particles have extremely good wettability with nickel. Therefore, when a wear-resistant and corrosion-resistant alloy made of a nickel-based alloy is used as the lining layer, this nickel-based alloy is centrifugally cast. Granulated powder containing tungsten carbide is well dispersed in the wear and corrosion resistant alloy.

In order to produce a granulated powder in which hard particles are bonded with a metal, for example, when the hard particles are tungsten carbide particles, a tungsten carbide powder having an average particle size of 1 to 10 μm is added to a cobalt as a binder. And a high melting point metal powder (average particle size of 0.5 to 10 μm), a solvent and the like are added and mixed, and a green material having a predetermined average particle size is obtained using a spray granulator or a swing granulator. Produce flour. Subsequently, by sintering and classifying the green powder, it is possible to produce a granulated powder in which the tungsten carbide fine powder is firmly bound by a metal such as cobalt and is spherical. When the content of tungsten carbide in the granulated powder is 94% by weight and the content of cobalt as a binder is 6% by weight, the specific gravity of the granulated powder is 14.8. The granulated powder is 1.5 from the specific gravity of nickel-based abrasion and corrosion resistant alloy of about 8
More than twice as large and spherical, and the average particle size is 30 to 30
If a powder having a thickness of 0 μm is used, the granulated powder can be densely and uniformly filled in the wear-resistant and corrosion-resistant alloy by a centrifugal casting method.

In the present invention, the volume ratio of the granulated powder in the lining layer of the finished cylinder product is 50 to 7%.
It is preferably 0%. If the volume ratio of the granulated powder contained in the lining layer is less than 50%, the wear resistance of the lining layer is not significantly improved as compared with the conventional cylinder,
If it exceeds 70%, production becomes practically difficult. More preferably, the volume ratio of the granulated powder in the lining layer is 55 to 55.
It is better to be 65%. In addition, in order to ensure the performance and reliability of the product, it is desirable that the difference in the volume ratio of the granulated powder in the lining layer in the axial direction is uniformly dispersed within 10%.

[0015]

EXAMPLES (Example 1) Granulated powder (ultra-hard WC-Co powder) was prepared by combining 94% by weight of tungsten carbide particles having an average particle diameter of 5 μm with 6% by weight of cobalt as a binder. The granulated powder was spherical particles having an average particle diameter of 80 μm, and the specific gravity was 14.9. Further, as a wear-resistant and corrosion-resistant alloy, a nickel-based alloy (C: 0.1% by weight, Si:
1.0%, Mn: 1.0%, Cr: 7.5%, B: 2.
9%, Co: 10.0%, Ni: balance) were produced in a high-frequency furnace. The specific gravity of this nickel-based wear-resistant corrosion-resistant alloy was 8.0. When the temperature of the molten nickel-based wear-resistant and corrosion-resistant alloy reached 1200 ° C., 36% by volume of the granulated powder was added to the molten metal.

Subsequently, a hollow cylindrical base material made of chromium molybdenum steel was heated while being set in a horizontal centrifugal casting machine. After the cylinder base material is heated to 1200 ° C., the molten metal of the nickel-based wear-resistant and corrosion-resistant alloy to which the above-mentioned granulated powder is added is poured into the inner surface of the cylinder base material, and the nickel-based wear-resistant alloy is encapsulated by centrifugal casting. A lining layer in which granulated powder was densely dispersed in the corrosion resistant alloy was formed. The size of the cylinder material manufactured by this centrifugal casting method is 110
mm × 30 mm inner diameter × 1500 mm length.

In the manufactured cylinder material, the vicinity of the inner diameter portion where the granulated powder was not dispersed in the nickel-based wear-resistant and corrosion-resistant alloy was removed by BTA processing. Next, the hard layer, in which the granulated powder is filled by centrifugal separation into the nickel-based wear-resistant and corrosion-resistant alloy, is subjected to honing to finish the lining layer in which the granulated powder of a predetermined thickness is densely filled. Was. The thickness of the lining layer of the finished cylinder is 1.9m
m, the volume ratio of the granulated powder composed of WC-Co in the lining layer was 61%. FIG. 1 shows a micrograph of the lining layer at this time. As is clear from FIG. 1, it was confirmed that the granulated powder in the lining layer was densely dispersed in a state where the spherical shape was maintained.

Example 2 A sample (Example of the present invention) was prepared from the lining layer of the cylinder for a molding machine manufactured in Example 1, and the wear resistance was evaluated by an abrasive wear test. Conditions for the abrasive wear resistance test were as follows: SiC emery paper: # 400, rotation speed: 350 rpm, pressing force: 3
N, test time: 3 minutes.

For comparison with the molding machine cylinder of the present invention, the same abrasion resistance was evaluated for Comparative Examples 1 and 2. In Comparative Example 1, a sample was prepared from a lining layer in which 5% by volume of niobium carbide (NbC) sintered particles were dispersed in a nickel-based alloy. In Comparative Example 2, a sample was prepared from a lining layer in which 30% by volume of tungsten carbide particles were dispersed in a nickel-based alloy. Comparative Example 2 is the same as the conventional example shown in FIG.

FIG. 2 shows the results of the above-described abrasive wear resistance test. As is apparent from FIG. 2, the cylinder for molding machine according to the present invention has a weight loss of 1.3 mg / cm 2, the comparative example 2 has a weight loss of 8.4 mg / cm 2, and the present invention is comparative example 2 It was found that the abrasion resistance was improved by a factor of 5 or more as compared with.

In the above description, the molding machine cylinder of the present invention is used for molding a plastic resin. However, the present invention is also applicable to a molding machine cylinder for MIM and plastic magnets. Can be.

[0022]

The present invention described above has the following effects. (1) Abrasion resistance can be further improved as compared with a conventional molding machine cylinder having a lining layer in which hard particles are dispersed. (2) In the present invention, since the granulated powder having a relatively large average particle diameter, which is formed by bonding superhard particles with metal and spheroidized, is densely dispersed in the lining layer, the volume ratio of the granulated powder in the lining layer is high. Even if it is as high as 50 to 70%, a non-hard alloy layer in which granulated powder is not dispersed can be formed in the inner diameter portion of the lining layer. It becomes easier as compared with the case where it is performed.

[Brief description of the drawings]

FIG. 1 is a micrograph (100 magnification) showing the structure of a lining layer of a cylinder for a molding machine of the present invention.

FIG. 2 is a graph showing the results of an abrasive wear resistance test of molding machine cylinders according to the present invention and comparative examples.

FIG. 3 is a micrograph (magnification: 100) showing a structure of a lining layer in which conventional hard particles are dispersed.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) // C22C 29/02 C22C 29/02 CD 32/00 32/00 N

Claims (9)

[Claims] 1. A molding machine cylinder in which a lining layer containing an abrasion-resistant and corrosion-resistant alloy is formed on the inner surface of a hollow cylinder-shaped cylinder base material, wherein granulated powder in which hard particles are bonded to a metal is dispersed in the lining layer. A molding machine cylinder. 2. The molding machine cylinder according to claim 1, wherein the granulated powder has a higher specific gravity than the wear-resistant and corrosion-resistant alloy. 3. The granulated powder is a spherical particle having an average particle diameter of 30 to 300 μm.
A cylinder for a molding machine according to item 1. 4. The molding machine cylinder according to claim 1, wherein the volume ratio of the granulated powder in the lining layer is 50 to 70%. 5. The molding machine cylinder according to claim 1, wherein the difference in the volume ratio of the granulated powder occupying the lining layer in the axial direction is within 10%. 6. The granulated powder contains tungsten carbide powder as hard particles.
The cylinder for a molding machine according to any one of the above. 7. The cylinder for a molding machine according to claim 1, wherein the granulated powder is obtained by binding tungsten carbide powder with cobalt. 8. The molding machine cylinder according to claim 1, wherein the wear-resistant and corrosion-resistant alloy is made of a nickel-based alloy. 9. The method according to claim 1, wherein the granulated powder is dispersed in the lining layer by a centrifugal casting method.
The cylinder for a molding machine according to any one of the above.