JPH07205234A - Injection screw and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve wear resistance and to perform excellent durability by forming a cermet layer made of Ni-based self-fluxing alloy and TaC on an outer periphery of a crest of a screw. CONSTITUTION:A cermet layer 20 having a predetermined thickness is formed on an outer periphery of a crest 10 of an injection screw 18. The layer 20 is so formed as to cover the periphery of the crest 10 over a front surface, but not required on a side of the crest 10 and a trough 12. The layer 20 is formed of a composite material which contains Ni-based self-fluxing alloy containing Ni-Cr-B-Si as main ingredients and tantalum carbonate. The layer 20 is flame sprayed on the outer periphery of the screw 18 by a powder padding flame sprayer using a heat source of a gas burner or a plasma jet, etc., with mixed powder of the alloy powder and the TaC powder.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an injection screw used in an injection device in an injection molding machine for molding a resin material and the like, and a method for manufacturing the same.

[0002]

BACKGROUND ART In an injection molding machine for injection molding a resin material or the like to obtain a desired molded product, conventionally, an injection screw having a spiral mountain portion is inserted and arranged in a heating cylinder,
An injection device is used in which a molding material such as resin is mixed or plasticized based on the rotation and advance / retreat operation of the injection screw, and the mixture is injected from the nozzle at the tip of the heating cylinder into the molding cavity of the mold. .

By the way, the injection screw used in such an injection apparatus is generally made of heat-treated steel material (SACM645) or the like, and the surface of which is subjected to nitriding treatment or chrome plating treatment. Has been adopted. By performing the nitriding treatment or the chrome plating treatment, the hardness of the screw surface is increased and the abrasion resistance and durability of the injection screw can be improved.

However, even the injection screw which has been subjected to the above-mentioned surface treatment cannot obtain sufficient wear resistance and corrosion resistance depending on the type of molding material used, and in particular, the mountain portion contacting the inner surface of the heating cylinder. The outer peripheral surface was worn out in a short period of time, and the outer diameter of the screw was reduced, so that the durability was sometimes inferior. For example, polyethylene, polypropylene, A
Even with resin materials such as BS, titanium white (T
When a high hardness filler or additive such as iO ₂ ) is used, there is a problem that the surface of the screw is greatly worn and cannot be used for a long time.

[0005]

The present invention has been made in view of the circumstances as described above, and the problem to be solved is that abrasion resistance is improved and excellent durability is exhibited. To provide an injection screw and a manufacturing method thereof.

[0006]

In order to solve such a problem, the present invention provides an injection screw having a spiral mountain portion as described above, at least on the outer peripheral surface of the mountain portion, a Ni-based self-fluxing alloy and TaC (carbonization). That is, a cermet layer made of tantalum) is provided.

Further, according to the present invention, when such an injection screw is manufactured, a screw material having a spiral mountain portion is sprayed with a mixed powder of a Ni-based self-fluxing alloy and TaC, thereby producing the screw. A method of manufacturing an injection screw in which a cermet layer composed of a Ni-based self-fluxing alloy and TaC is formed on the outer peripheral surface of at least the mountain portion of the material is also a feature.

Further, according to the present invention, when manufacturing an injection screw according to such a method, first, a spiral groove is formed in a portion of a screw material where a mountain portion is formed, and a Ni base is formed in the groove. After forming a cermet layer composed of a Ni-based self-fluxing alloy and TaC by spraying a mixed powder of a soluble alloy and TaC, the screw material is cut to form a spiral valley between the formation parts of the cermet layer. It is also characterized by a method for manufacturing an injection screw in which the cermet layer forms a mountain portion provided on the outer peripheral surface by forming the above.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The material of the screw material for forming the injection screw according to the present invention is not particularly limited, but a steel material for mechanical structure such as SACM645 which has been conventionally used is used. Can be suitably adopted. Further, as the screw material, a material having a Rockwell hardness of about H _R C28 is desirable, whereby good durability can be obtained, and weldability to a cermet layer described later becomes good.

Then, a round bar-shaped screw material made of such a material is subjected to cutting and polishing, and as shown in FIG. 1, a spiral mountain portion 10 and a valley portion are formed on the outer peripheral surface. 12 is formed, a screw head side tip portion 14 and a spline shaft mounting side base end portion 16 are formed, and further an appropriate heat treatment or the like is added to form an injection screw 18. Will be done. The outer diameter of the injection screw 18, the shapes and sizes of the peaks 10 and the valleys 12 formed on the outer peripheral surface of the injection screw 18, the specific shapes of the distal end portion 14 and the proximal end portion 16, and the like are applicable. It is appropriately set according to the device, the molding material, and the like. In the illustrated injection screw 18, the screw head is screwed and fixed to the tip portion 14.

Moreover, in the injection screw 18, as shown in the enlarged sectional view of the main part in FIG. 2, the cermet layer 20 having a predetermined thickness is formed on at least the outer peripheral surface of the mountain portion 10. is there. In addition, this cermet layer 20
Need only be formed so as to cover at least the entire outer peripheral surface of the mountain portion 10, and the side surface of the mountain portion 10 and the valley portion 12
Need not always be formed.

Here, the cermet layer 20
In order to advantageously achieve the object of the present invention, Ni-Cr-B
It is composed of a composite material composed of a Ni-based self-fluxing alloy containing Si as a main component and TaC (tantalum carbide). For the cermet layer 20, for example, a mixed powder of Ni-based self-fluxing alloy powder and TaC powder, or a mixed powder of Ni-based self-fluxing alloy powder and TaC powder is used. It is advantageously formed by spraying the outer peripheral surface of the injection screw 18 with a powder overlay thermal spraying apparatus or the like that uses a heat source such as a plasma jet.

As the Ni-based self-fluxing alloy which is one of the constituents of the cermet layer 20, N is generally N.
In addition to i, Cr, B, and Si, those containing Fe, C, W, etc. as needed are used. In particular, Ni: about 64% by weight, Cr: 18.5 to 22.5% by weight, B : 0.80-
1.20% by weight, Si: 5.50 to 6.50% by weight, F
e: 6.50 to 8.50% by weight, C: 0.20 to 0.4
Those having a composition of 0% by weight and W: 1.50 to 2.50% by weight are preferably used from the viewpoint of high hardness and the like.

When the cermet layer 20 is formed by the build-up thermal spraying method using Ni-based self-fluxing alloy and TaC powder, the particle size of the Ni-based self-fluxing alloy powder is 180 μm.
m or less, particularly about 63 to 150 μm is preferable from the viewpoint of thermal spraying property, and the particle size of TaC powder is 3 μm.
It is preferable that the thickness is m or less, particularly about 2 to 3 μm, from the viewpoint of securing the dispersion effect in the Ni-based alloy and preventing concentration in the lower layer portion and the upper layer portion.

Furthermore, these Ni-based self-fluxing alloys and T
The mixing ratio of aC is, by volume, Ni-based self-fluxing alloy: TaC.
= 60-40%: 40-60%, especially 50%: 50% is preferable. Kashidashi, Ni-based self-fluxing alloy mixing ratio is 60%
If the mixing ratio of TaC is more than 40%, it is difficult to obtain sufficient hardness in the cermet layer 20 to be formed, and it becomes easy to wear. Less, TaC mixing ratio is 60%
This is because if the amount is larger, it is difficult to obtain sufficient toughness in the cermet layer 20 to be formed, and cracks or the like are likely to occur.

Furthermore, if the cermet layer 20 is too thin, it is difficult to exert a sufficient effect, and if it is too thick, manufacturability, cost efficiency, etc. are deteriorated.
Generally, it is desirable that the finished screw has a thickness of 0.9 to 1.2 mm.

By the way, the injection screw 18 in which the cermet layer 20 made of such a Ni-based self-fluxing alloy and TaC is formed on the outer peripheral surface of the mountain portion 10 is advantageously manufactured by the following method, for example. .

First, a round bar-shaped screw material formed of the steel material for machine structure as described above is prepared, and the screw material is cut to form a spiral shape in the portion where the mountain portion 10 is to be formed. To form a groove.

Next, a powder mixture of Ni-based self-fluxing alloy having the above-mentioned composition and particle size and TaC is sprayed into the concave groove of the screw material by a plasma powder overlay welding device or the like to perform overlay welding. By doing so, the cermet layer 20 is formed in the groove so as to fill the groove. It should be noted that the cermet layer 20 exhibits excellent adhesion to the screw material by the action of the Ni-based self-fluxing alloy, even if no special adhesion treatment is performed. In addition, such overlay welding is generally performed by rotating the screw material around the axis, moving the screw material in the axis direction at a predetermined speed, and spraying the screw material along the spiral groove.

Further, low-temperature annealing is performed at 580 to 600 ° C., the cermet layer 20 is subjected to post-treatment for reheating by heating, and then cutting processing is performed, whereby the cermet layer 20 is subjected to cutting.
The recessed groove portion welded to is left as a mountain portion, and other portions located between the recessed grooves are scraped off. Thereby,
The ridge portion 1 is formed by the concave groove portion to which the cermet layer 20 is welded.
0 is formed, and the valley 12 is formed by the portion other than the concave groove.
To form. By doing so, the cermet layer 20 is formed only on the outer peripheral surface of the mountain portion 10.

Then, after the peaks 10, valleys 12, screw head side tip portion 14, and mounting side base end portion 16 are formed, the surface is finished by polishing to obtain the intended injection screw 18. be able to.

According to such a manufacturing method, by spraying the mixed powder of the Ni-based self-fluxing alloy and TaC into the concave groove formed in the screw material, the cermet layer 20 is formed only on the outer peripheral surface of the mountain portion. Since it can be easily formed, it also has an advantage that unnecessary thermal spraying is suppressed and the amount of expensive TaC used is reduced.

In the injection screw 18 having the above-described structure, the cermet layer 20 formed on the outer peripheral surface of the mountain portion 10 is a composite in which TaC having high hardness is dispersed and mixed in the Ni-based alloy. It has a structure, has sufficient toughness and high hardness, and can exhibit excellent abrasion resistance, whereby excellent durability can be exhibited. Therefore, for example, when molding a resin material containing a coloring pigment such as titanium white (TiO ₂ ) or glass fiber, abrasion of the mountain portion 10 of the injection screw can be suppressed, and excellent durability can be exhibited. is there.

In the injection screw 18, abrasion on the outer peripheral surface of the mountain portion 10 contacting the inner peripheral surface of the heating cylinder due to a resin material or the like entering the gap between the mountain portion and the heating cylinder becomes a particular problem. As long as the cermet layer 20 is formed so as to cover at least the outer peripheral surface of the mountain portion, the effective effect of improving the wear resistance can be exhibited.

In order to more specifically clarify the present invention, representative examples of the present invention will be shown below, but the present invention is not limited by the above-mentioned specific description and the description of the following examples. Of course, it should not be construed as limiting.

For example, it is possible to form a cermet layer on the side surface of the crest portion of the injection screw and also on the trough portion, thereby improving the wear resistance and the corrosion resistance at those portions. it can. Further, by extending the cermet layer formed on the outer peripheral surface of the mountain portion to the corner (shoulder portion) between the outer peripheral surface of the mountain portion and the side surface thereof, the effect of preventing chipping of the cermet layer is also exhibited.

The injection screw according to the present invention can be manufactured by a method other than the above-mentioned manufacturing method. For example, after cutting a screw material to form peaks and valleys, at least the outer circumference of the peaks. It is also possible to form the cermet layer so as to cover the surface, and in particular, in the case where the cermet layer covers substantially the entire outer peripheral surface of the injection screw including the peaks and valleys, such a manufacturing method is preferable. Adopted by.

Although not listed one by one, the present invention can be carried out in a mode in which various changes, modifications, improvements, etc. are added based on the knowledge of those skilled in the art, and such an embodiment is the gist of the present invention. It goes without saying that all of them are included in the scope of the present invention without departing from the above.

[0029]

Example A round steel material (φ110 mm) of SACM645 was used as a screw material, and a material having a hardness of H _R C28 ± 2 was adopted by heat treatment of quenching and tempering. Then, the screw material is subjected to a cutting process to form a spiral groove in a portion where a mountain portion is to be formed, and then a powder mixture of Ni-based self-fluxing alloy powder and TaC powder is used to form a plasma powder. A cermet layer was formed in the groove by thermal spraying and overlay welding with a overlay welding device. Subsequently, low-temperature annealing is performed at 600 ° C., and then cutting and polishing are performed to form spiral valleys and the like, thereby forming spiral ridges having a cermet layer with a thickness of 1.0 mm on the outer peripheral surface. After being formed, and then subjected to a gas nitriding treatment, a target injection screw of 110 mmφ was obtained.

Here, as the Ni-based self-fluxing alloy, a powder having the composition and physical properties shown in Table 1 below is used, and as TaC, a powder having the physical properties shown in Table 2 below is used. Was used. And 5 of those powders
A cermet layer was formed by spraying the mixed powder at a volume ratio of 0:50.

[0031]

[Table 1]

[0032]

[Table 2]

When the hardness of the cermet layer of the injection screw obtained as described above was measured, a Vickers hardness of H _V 2100 was confirmed. Then, the injection screw was set in an injection device of a molding machine of 850 tons, and titanium white (Mohs hardness = 6 to
6.5, polypropylene or polyethylene containing H _V 600), was used for injection molding of ABS resin, the wear amount at the crest outer peripheral surface (measured by diameter at the crest) is, 0.07 mm in 3 months, It was confirmed to have an extremely excellent wear resistance, which was only 0.23 mm in 8 months. Also, during use,
No damage such as chipping of the cermet layer was observed.

By the way, the same screw material as in this embodiment was used, and the ridges and valleys were cut by the conventional method, respectively, and then nitrided at a treatment depth of 0.35 mm. Chrome-plated screws each having a hard chrome-plated surface with a plating layer thickness of 0.04 to 0.05 mm were manufactured as comparative examples. Furthermore, T
Using only Ni-based self-fluxing alloy powder that does not mix aC,
A Ni-based self-fluxing alloy welding screw in which the powder of the Ni-based self-fluxing alloy is sprayed on the outer peripheral surface of the mountain portion by the same method as in this example to form an alloy layer with a layer thickness of 1.0 mm is also compared. Produced as an example.

Then, the surface hardness of each injection screw as a comparative example was measured, and
It was set in an injection device of a molding machine of 50 tons and used for injection molding under the same conditions as in this example to measure the wear amount of the outer peripheral surface of the crest portion (measured by the diameter dimension of the crest portion). The results are shown in Table 3 below, and also from the test results of these comparative examples,
It is clear that the injection screw of this example has excellent hardness characteristics and wear resistance.

[0036]

[Table 3]

[0037]

As is apparent from the above description, in the injection screw having the structure according to the present invention, the toughness of the Ni-based self-fluxing alloy and the TaC in the cermet layer formed on the outer peripheral surface of the crest portion. The high hardness is well-balanced and the wear of the ridges is advantageously suppressed. Therefore, extremely excellent durability can be exhibited and stable performance is achieved for a long time. is there.

Further, according to the method of the present invention, the desired cermet layer can be easily formed with an appropriate mixing ratio of the Ni-based self-fluxing alloy and TaC, which results in excellent manufacturability and product quality. Stabilization can be advantageously achieved.

Moreover, if the mixed powder of the Ni-based self-fluxing alloy and TaC is sprayed into the concave groove provided in the portion where the mountain portion of the screw material is formed, the cermet layer is formed.
The sprayed part of the mixed powder is advantageously defined, and the cermet layer can be easily formed only on the outer peripheral surface of the crest part, which facilitates the formation of the cermet layer and prevents the spraying of unnecessary parts. Etc. can be effectively achieved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a specific example of an injection screw having a structure according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the injection screw shown in FIG.

[Explanation of symbols]

 10 mountain part 12 valley part 18 injection screw 20 cermet layer

Claims (3)

[Claims] 1. A heating cylinder of an injection device, which is inserted and arranged in a heating cylinder.
An injection screw having a spiral mountain portion, wherein a Ni-based self-fluxing alloy and T are formed on at least the outer peripheral surface of the mountain portion.
An injection screw having a cermet layer made of aC. 2. When manufacturing the injection screw according to claim 1, a portion for forming at least the ridge portion of the screw material by spraying a mixed powder of a Ni-based self-fluxing alloy and TaC onto the screw material. A method for producing an injection screw, comprising forming a cermet layer composed of a Ni-based self-fluxing alloy and TaC on the outer peripheral surface of. 3. A spiral groove is formed in a portion of the screw material where the peak is formed, and a mixed powder of a Ni-based self-fluxing alloy and TaC is sprayed into the groove,
After forming a cermet layer made of the Ni-based self-fluxing alloy and TaC, the screw material is cut to form a spiral valley between the cermet layer forming portions, thereby forming an outer peripheral surface of the cermet layer. The method for manufacturing an injection screw according to claim 2, wherein the ridge portion provided on the ridge is formed.