JPH0270051A - Formation of wear resistant structure of sliding part for injection molding machine - Google Patents

Abstract

PURPOSE:To obtain the wear resistant structure having excellent strength, wear resistance and durability by mixing and welding an Ni base and WC to the surface of the base material of the sliding part and welding the WC to the resultant base body layer, thereby forming the wear resistant layer nearly uniformly dispersed with the Ni base and the WC. CONSTITUTION:Powders of the Ni base and the WC are mixed and are welded by a plasma welding device 50 to the surface of the base material S of the sliding part such as ring valve of an injection molding machine to form the base body layer 10A. The mixing ratio of the Ni base and the WC of the above-mentioned powder is adequately about 7:3 by volume. The WC 15 sinks to the lower part and the upper part consists mostly of only the Ni base 14 in the base body layer 10A obtd. in such a manner by the difference in sp. gs. The WC is then plasma-welded to the above- mentioned base body layer 10A. The amt. of the WC to be welded at this time is preferably made equal to the amt. of the WC to be welded to the above-mentioned base body layer 10A. The WC is intruded into the above-mentioned Ni base 14 by this welding of the WC. The wear resistant layer 10 in which the WC 15 is nearly uniformly dispersed in the Ni base 14 as a whole is thus easily and surely formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming a wear-resistant structure in a sliding part that is prone to wear in an injection molding apparatus.

(Prior Art) In an injection molding device, for example, when charging the molding material, the front end face of the link heart and the rear end face of the screw head come into contact with each other, and since the screw head is rotating, they slide, and the sliding surfaces of both contact. wear due to friction occurs. In particular, if the molding material is a hard material such as ceramic, or if it contains glass filler, etc., the sliding parts of both parts will wear significantly, resulting in an extremely shortened screw life. ing.

As a means to solve such problems, for example,
As disclosed in Japanese Patent No. 2-68703, a structure has been proposed in which wear is prevented by thermally spraying an appropriate amount of tungsten carbide, which is a hard powder, on the contact surfaces of both parts.

Now, it is preferable that the tungsten carbide is thermally sprayed together with a nickel-based alloy having heat resistance and wear resistance by a plasma spraying method.

However, it has become clear that when these metal balata are mixed and thermally sprayed, the following problems occur.

That is, when a metal balater of tank sten carbide and a nickel-based alloy is mixed and sprayed, the specific gravity of both metals is 15.8 for tungsten carbide and 8.8 for nickel-based alloy.
9, as is clear from the enlarged cross-sectional view of the welding layer 40 shown in FIG. The tungsten carbide concentrates on the sides, and there is almost no tungsten carbide on the top of the weld layer, making it impossible to obtain a uniform weld layer. Therefore, such a welding layer 40
In this case, the upper and lower parts of the layer have different hardnesses, making it impossible to obtain a wear-resistant layer with a predetermined strength.

(Problems to be Solved by the Invention) Therefore, in view of the above situation, the present invention has been developed to provide a material that has strength based on a predetermined mixing ratio without having physical properties such as hardness different between the upper and lower parts of the layer. The object of the present invention is to provide a method for reliably forming a wear-resistant structure with excellent wear resistance and durability.

(Means for solving the problem) That is, the present invention relates to a method of forming a wear-resistant structure,
This method includes the steps of forming a base layer by welding a mixture of nickel base and tungsten carbide on the base material surface of the sliding part, and welding tungsten carbide to the base layer to form a nickel base and tank sten carbide layer. forming a wear-resistant layer in which the wear-resistant layers are almost uniformly dispersed.

(Example) The present invention will be described in detail below with reference to the attached drawings.
Figure 1 is a cross-sectional view of the main parts of an injection molding machine in which a wear-resistant layer is formed on the sliding parts of the screw head and link heart, Figure 2 is an enlarged cross-sectional view of the wear-resistant layer in Figure 1, and Figure 3 is a conventional FIG. 4 is a sectional view showing the step of forming the base layer in the method of the present invention, and FIG. 5 is a sectional view showing the step of forming the wear-resistant layer.

As shown in FIG. 1, a screw 12 is rotatably inserted into the heating cylinder 11 of the injection molding apparatus, and a screw head 20 is connected to the tip of the screw via a wear plate 13.
is screwed on. The screw head 20 has a large diameter portion 21 provided with a cutout passage 23 through which molten molding material passes, and a thin shaft portion 22 that is screwed onto the screw. Further, a link hartz 30 that comes into contact with the inner surface of the heating cylinder 11 is fitted onto the outer periphery of the thin shaft portion 22, and the link valve inner peripheral surface 3
1 and the thin shaft portion 22, a gap serving as a resin passage P is formed.

When charging (filling) with molten resin, the link hartz 30 is pushed forward by the resin feeding pressure, and the rear end 32 of the ring hartz and the front end 13a of the wear plate are pushed forward.
A gap is formed between them, and the resin passage P is opened and communicates with the notch passage 23.

At this time, the front end 33 of the link heart and the rear end surface 21a of the large diameter part of the screw head are in contact with each other, and since the screw 12 is rotating at the same time, the wear on these sliding parts becomes extremely large.

However, in this injection molding apparatus, wear-resistant layers 10 and 10 are formed on the rear end surface 21a of the large diameter portion of the screw head, which serves as a sliding portion, and on the front end surface 33 of the link heart, respectively.

This wear-resistant layer has a thickness of about 4 mm and is composed of a plasma-welded layer of metal parametries of nickel base and tungsten carbide.

In this wear-resistant layer 10, as can be seen from the enlarged cross-sectional view in FIG. It is welded and formed.

Figure 3 is a cross-sectional view of a conventional wear-resistant structure.
1 sinks below the nickel base 42, which has a low specific gravity, and a uniformly dispersed and mixed state cannot be obtained.

This wear-resistant layer 10 is formed by the method described below.

First, as shown in Fig. 4, a parata of nickel-based Ni and tungsten carbide WC is applied to the surface of the base material S, such as the front end face of the link valve that becomes the sliding part or the rear end face of the large diameter part of the screw head. The base layer 1 is mixed and welded using a known plasma welding apparatus 50 at a mixing ratio of 7 [nickel base] to 3 F tank stenker height (volume ratio).
0A is formed. In this example, rNimonic80AJ (trade name) was used as the nickel group.

As shown in the figure, in the base layer 10A formed here, due to the difference in specific gravity, the tungsten carbide 5 sinks into the lower part of the base layer 10A, and the upper part is almost nickel-based 14.
There are only two layers. This is similar to the conventional weld layer 40 illustrated in FIG.

Next, in the method of this invention, as shown in FIG. 5, the substrate formed in the above process! 1 Tungsten carbide WC is welded to the OA using the plasma welding device 50 as described above. The amount of tungsten carbide deposited at this time is preferably the same as the amount of tungsten carbide deposited in the step of forming the base layer.

Through this step, as shown in the figure, tungsten carbide 15 also enters the upper part of the base layer 10A, that is, into the nickel base 14 where almost no tungsten carbide was present, and as a whole, almost all tungsten carbide 15 or nickel base 14 is present. A uniformly distributed wear-resistant layer 10 is formed.

(Effects) As illustrated and explained above, according to the present invention, a wear-resistant layer in which nickel base and tungsten carbide are almost uniformly dispersed is easily and reliably welded to the surface of the base material of the sliding part of an injection molding device. It became possible to form. Therefore, a metal layer having a predetermined mixing ratio is formed over the entire layer, and a wear-resistant layer having desired hardness and stable physical properties such as wear resistance and durability can be formed. The effects of this invention are actually quite large.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the main parts of an injection molding machine in which a wear-resistant layer is formed on the sliding parts of the screw head and link heart, Figure 2 is an enlarged cross-sectional view of the wear-resistant layer in Figure 1, and Figure 3 is a , FIG. 4 is a sectional view showing the step of forming the base layer in the method of the present invention, and FIG. 5 is a sectional view showing the step of forming the wear-resistant layer. 10... Wear-resistant layer, IOA... Base layer, 14...
Nickel base, 15...Tungsten carbide, 20
...Screw head, 21a...Large diameter portion rear end surface, 3
0... Ring Harz, 33... Link Harz front end surface.

Claims (1)

[Claims] 1. A step of forming a base layer by welding a mixture of nickel base and tungsten carbide on the base material surface of the sliding part, and a step of welding tungsten carbide to the base layer to form the nickel base and tungsten carbide. 1. A method for forming a wear-resistant structure in a sliding part of an injection molding device, the method comprising the step of forming a wear-resistant layer in which a wear-resistant layer is almost uniformly dispersed. 2. The method for forming a wear-resistant structure in a sliding part of an injection molding apparatus according to claim 1, wherein the mixing ratio of nickel base and tungsten carbide in the base layer forming step is about 7:3 by volume.