JP2000006210A - Wear-resistant part for plastic injection molder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive to realize an excellent fatigue strength and, at the same time, to improve the corrosion resistance and the wear resistance of a part by a method wherein the base of a part for a plastic injection molder is made of a nitrided steel and, at the same time, at the portion, to which both the corrosion resistance and the wear resistance are necessary, a cermet material is bonded to the base. SOLUTION: In a back flow valve for a plastic injection molder, an excellent corrosion- and wear-resistant ring-like cermet material 11 is coaxially bonded to one edge face of a tubular base 10. Further, the base 10 is made of a nitrided steel, the surface hardness of which can be improved by applying a nitriding treatment. Since the resultant case is thin and has an excellent toughness as compared with a hard cermet material, the case can fully stand against an injection force and consequently is suitable for the base material of the back flow valve. Further, this nitriding treatment is carried out after the bonding of the base 10 and the hard cermet material 11. On the other hand, as the wear-resistant material, for example, a Ni-B-Si-W-WC alloy is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wear-resistant part such as a screw head of a plastic injection molding machine and a check valve attached thereto.

[0002]

2. Description of the Related Art Generally, screw heads and check valves in a plastic injection molding machine are constantly in contact with a resin which is fed at high temperature and high pressure. Corrosion resistance and abrasion of the above components, which are caused by flame retardants and inorganic fillers added to resins for the purpose of improving performance, have become major problems. Further, in order to reduce the wall thickness of the engineering plastic product in order to reduce its weight, the molding pressure becomes higher and the strength of the check valve is required.

[0003] In view of the above, it has been proposed that the screw head, the check valve, or the spacer is made of ceramic having excellent corrosion resistance and wear resistance.

FIG. 7 is a view showing the configuration of the tip of a screw of an injection molding machine. In a casing 1, a screw 2 having a helical ridge 2a formed on the outer periphery is rotated and rotated by an axis. It is arranged to be movable in the direction.
A screw head 3 is fixed to the tip of the screw 2 by a screw, and a spacer 4 is interposed and fixed between the screw 2 and the screw head 3.

A small-diameter shaft portion 3a having a smaller diameter than the distal end portion is formed at an intermediate portion of the screw head 3, and a ring-shaped check valve 5 is fitted to the small-diameter shaft portion 3a. A radial gap is formed between the inner surface of the check ring 5 and the small-diameter shaft portion 3a, and moves along the small-diameter shaft portion 3a between the large-diameter portion of the screw head 3 and the spacer 4. It is possible. An axial groove 3b is formed in the large diameter portion of the screw head 3.

When the screw 2 retreats in the direction of arrow B while rotating in the direction of arrow A, the material to be injected in the gap between the screw 2 and the cylinder 1 is moved forward,
The space between the small-diameter shaft portion 3a of the screw head 3 and the inner surface of the check valve 5 and the axial groove 3b of the screw head 3 is filled with the space between the tip of the screw head and the tip of the cylinder. In this way, when the required amount of material to be injected corresponding to the volume of the injection molded product is filled at the tip of the cylinder, both the rotation and the retreat of the screw 2 are stopped.

[0007] Then, when the screw 2 is advanced next, the material to be injected filled in the tip of the cylinder is extruded from the nozzle 1a. On the other hand, at this time, the check ring 5 contacts the end face of the spacer 4, and the check ring 5 prevents the material to be injected from leaking to the outer peripheral side of the screw 2.

As described above, screw parts such as screws and check valves are constantly in contact with a high-temperature, high-pressure resin as a material to be molded, and the contact surfaces thereof are required to have wear resistance and corrosion resistance. When the workpiece is weighed and accumulated, the screw rotates and moves backward, but during this time, the check ring is pressed against the rear end face of the large-diameter portion of the screw head, so friction occurs between the check ring and the screw head. Then, wear occurs on both.

[0009]

SUMMARY OF THE INVENTION
It has been proposed to use ceramics in parts requiring abrasion resistance to improve the abrasion resistance. However,
Since the ceramics are inferior in toughness, there is a problem that the ceramics is damaged when an injection pressure acts, for example, during resin injection.

In view of the foregoing, it is an object of the present invention to provide a wear-resistant part for a plastic injection molding machine having excellent fatigue strength and excellent corrosion resistance and wear resistance and a long life.

[0011]

According to the present invention, a base of a part for a plastic injection molding machine is formed of nitrided steel, and a part of the part requiring corrosion resistance and wear resistance is provided with a cermet material on the base. It is characterized by being formed by joining.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1A is a longitudinal sectional side view of a check valve for a plastic injection molding machine according to the present invention, and FIG. 1B is a sectional view taken along line AA of FIG. A ring-shaped cermet material 11 having excellent corrosion resistance and abrasion resistance is joined to one end surface of the formed base 10 so as to have the same axis.

The base 10 is made of nitrided steel SACM645. The surface hardness of the nitrided steel can be improved by performing a nitriding treatment.
It is as thin as less than mm and has excellent toughness compared to hard cermet materials, so it can withstand injection pressure sufficiently and is suitable as a base material for check valves. Furthermore, the nitriding treatment has less deformation (strain) than the hardening method such as quenching,
The internal stress generated at the joint with the hard cermet material can be reduced, and this nitriding treatment is performed after joining the base and hard cermet, but only the surface layer of the base is cured without affecting the hard cermet. Therefore, it is suitable for joining with a hard cermit material.

On the other hand, Ni-B-
An Si-W-WC alloy was used. Ni-B-Si-W-
WC alloy is a double boride NiW that increases the strength and hardness of the alloy.
This is a cermet material which forms 2B2 and is solid-solution strengthened by the solid solution of Si in the Ni bond and has excellent corrosion resistance, wear resistance and strength.

In the case where a portion made of a cermet material having excellent corrosion resistance and abrasion resistance is formed in the above-mentioned check valve, the following procedure was carried out.

First, a raw material powder is added to a composition having excellent corrosion resistance and wear resistance (Ni-0.8 wt% B-3.6 wt% Si-30).
wt% W-29.6 wt% WC) and mixed and pulverized by a rotary ball mill. Table 1 shows the characteristics of the alloy powder.

[0018]

[Table 1] Therefore, molding is performed by a uniaxial pressure molding method (press molding method) using a die with the above alloy powder. That is, the mold is filled with the alloy powder, a pressurizing punch is inserted into the upper part of the mold, pressurization is performed at about 70 MPa, and then the molded body is taken out of the mold, and the pressure is 4 to 7 Pa using a vacuum furnace. , Temperature 1
Sintering is performed at 170 ° C. Then, the ring-shaped sintered member obtained by this sintering is bonded to the screw head side of the base 10 made of the above-described nitrided steel by using a Ni braze at a joining temperature of 9 mm.
Perform brazing at 30 ° C. Thereafter, a gas nitriding treatment is performed, and the outer diameter, the inner diameter, and the end face are ground to form a check valve.

When the check valve thus manufactured was incorporated into an injection molding machine and operated, the amount of wear on the screw head side end face was reduced to 1/3 of that of the conventional check valve made of SKD61. , The amount of wear other than that of the cermet material also decreased, and almost the same fatigue strength was obtained.

Further, in the above embodiment, the wear-resistant alloy and the base material are joined by brazing, but they can be joined by diffusion joining that does not require a brazing material. Further, in the above-described embodiment, the cermet material, which is a wear-resistant alloy, is joined to the end face of the base on the screw head side. However, as shown in FIG.
Alternatively, as shown in FIG. 3, cermet materials 11 may be joined to both ends of the base body 10, respectively.

On the other hand, as described above, the screw head for the injection molding machine is required to have abrasion resistance on the surface that comes into contact with the check valve and the surface that comes into contact with the inner diameter of the cylinder, and is preferably made of a hard material. The toughness is required for the threaded portion connected to.

Therefore, the screw head can also be formed as shown in FIG. That is, nitrided steel SAC
The base 12 is processed into a shape as shown in FIG. 4A using M645, and a Ni-B-Si-W-WC alloy is formed on the tip of the base 12 as shown in FIG. The ring-shaped cermet material 13 formed in the same manner as described above is fitted, brazed to each other using a Ni brazing material, and subjected to a gas nitriding treatment.
Is ground into a shape shown in FIG. 3C to a predetermined size to produce a screw head.

However, also in this case, the abrasion loss of the protruding portion is reduced to one third, the abrasion loss of portions other than the cermet portion is reduced, and the fatigue strength is lower than that of the conventional screw head material made of SKD61. Approximately the same was obtained.

In the above-described embodiment, the base and the wear-resistant alloy are joined by brazing. However, a brazing material is required, for example, simultaneous sintering of the cermet portion and joining to the base. It is also possible to adopt a bonding method that does not require.

FIGS. 5 and 6 are views showing another embodiment of the present invention. The outer peripheral surface of the small diameter shaft of the screw head is also formed of cermet material, or the entire head portion is formed of cermet material. It can also be configured.

In each of the above embodiments,
Although a material using a Ni-B-Si-W-WC alloy as the wear-resistant material is shown, as shown in Table 2, Ni-B-S
i-W alloy, Ni-B-Si-Mo-WC alloy, Ni-
A B-Si-Mo alloy or the like can also be used. Table 2 shows the composition of each alloy when applied to the check ring and the screw head.

[0027]

[Table 2]

[0028]

As described above, according to the present invention, a part of a plastic injection molding machine part which requires corrosion resistance and wear resistance is formed by bonding a cermet material to a substrate, so that the corrosion resistance and wear resistance of the above-mentioned part are improved. Not only wear and the like but also breakage and the like can be reliably prevented.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional side view of a check valve for a plastic injection molding machine according to the present invention, and FIG.
Sectional drawing which follows the A line.

FIGS. 2A and 2B are a longitudinal sectional side view and a sectional view taken along line BB, respectively, showing another embodiment of the present invention.

FIGS. 3A and 3B are a vertical sectional side view and a cross-sectional view taken along line CC, respectively, showing another embodiment of the present invention.

FIGS. 4A, 4B, and 4C are views showing a processing order of a screw head according to the present invention.

FIG. 5 is a diagram showing another embodiment of the present invention.

FIG. 6 is a diagram showing still another embodiment of the present invention.

FIG. 7 is a sectional view showing a screw head of a general plastic injection molding machine.

[Explanation of symbols]

 Reference Signs List 2 screw 3 screw head 3a small-diameter shaft portion 5 check valve 10, 12 base 11, 13 cermet material

Claims (7)

[Claims] The present invention is characterized in that a base of a part for a plastic injection molding machine is formed of nitrided steel, and a part of the part requiring corrosion resistance and wear resistance is formed by bonding a cermet material to the base. Features wear-resistant parts for plastic injection molding machines. 2. The wear-resistant part for a plastic injection molding machine according to claim 1, wherein the part for a plastic injection molding machine is a screw head. 3. The wear-resistant part for a plastic injection molding machine according to claim 1, wherein the part for a plastic injection molding machine is a check valve. 4. The wear-resistant part for a plastic injection molding machine according to claim 1, wherein the cermet material is a Ni-B-Si-W alloy. 5. The cermet material is Ni-B-Si-Mo-.
The wear-resistant part for a plastic injection molding machine according to any one of claims 1 to 3, wherein the wear-resistant part is a WC alloy. 6. The wear-resistant part for a plastic injection molding machine according to claim 1, wherein the cermet material is a Ni-B-Si-Mo alloy. 7. The cermet material is Ni-B-Si-WW.
The wear-resistant part for a plastic injection molding machine according to any one of claims 1 to 3, wherein the wear-resistant part is a C alloy.