JP3113234B2 - Screw for injection molding machine and method of manufacturing the screw - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw of an injection molding machine for injection-molding Mg, a low melting point metal, and the like, and a method of manufacturing the screw.

[0002]

2. Description of the Related Art As for the forming of Mg alloys, the die casting method is widely used at present. However, as a new technique, an injection molding method has been attempted to improve the working environment and increase the forming efficiency. I have. By the way, in order to obtain a highly reliable Mg injection molding machine, the screw for the injection molding machine must be able to be used stably for a long time, and the following conditions are required.

[0003] 1) The material must have little erosion upon contact with molten Mg. 2) A material that has a high high-temperature hardness when heated to an injection molding temperature of 600 to 650 ° C. of molten Mg and is not easily damaged by abrasion. 3) The screw must be a material having high temperature strength that is not easily subjected to tempering softening even when it is heated at the above high temperature for a long time. That is, it is a necessary condition that the screw that comes into intense contact with the molten Mg has little melting damage (corrosion damage due to the molten Mg) and has excellent high-temperature strength and softening resistance during high-temperature heating. As a material having the above-mentioned characteristics, Fe-based tool steel such as JIS standard SKD61 shows almost stable performance.

[0004]

However, the above-mentioned tool steel is not necessarily sufficient in terms of high-temperature strength, and furthermore, it is affected by softening at high-temperature heating or by giving a shear force to solid Mg to melt it. In the process up to this point, there is a danger that abrasion may occur and the battery may be easily broken. Therefore, development of a material having a longer life is expected.

[0005] For example, Inconel (trade name, hereinafter the same) 718 is known as a material having excellent high-temperature strength. However, it is difficult to use as a screw material due to remarkable erosion by molten Mg. In addition, stellite (trade name, the same applies hereinafter) and other Co base materials generally used as a tool material and a valve material are materials having excellent high-temperature strength. Although it was found that the amount was small, there was a problem that it was difficult to use as a screw material because the toughness was slightly inferior and expensive.

As described above, it is difficult to satisfy all the conditions of erosion resistance, abrasion resistance and high-temperature strength with a single metal material, which makes injection molding of a Mg alloy material more difficult. . The present invention has been made in view of the above circumstances, and can not be used alone as a screw material, it is possible to use as a screw material by combining the above two types of materials,
As a result, it is an object of the present invention to provide a long-life screw that utilizes the advantages of each other.

[0007]

That is, in the screw of the present invention, the screw core is made of a heat-resistant Ni-based or Fe-based material, and a Co-based heat-resistant material is formed on the surface of the screw flight peak of the core. And a hard metal film is formed on the valley surface of the core material.

Further, the method for manufacturing a screw according to the present invention comprises:
The screw core is made of a heat-resistant material based on Ni or Fe, and C
o After lining the base heat-resistant material and forming a hard metal film on the valley surface of the core material, the hard metal film is subjected to film improvement treatment by fusing or hot isostatic pressing. Features.

The base material of the member to which the present invention is applied is represented by a Ni-based heat-resistant alloy represented by Inconel 718, Inconel 706, Inconel X-750 or Thyssen T2888 (trade name, manufactured by Thyssen). Most preferably, a heat-resistant alloy based on Fe is used. For example, when Inconel 718 is represented by a component ratio (% by weight), it is represented by NiCrMoFeAlTiNb + Ta remaining 19% 3% 19% 0.5% 0.9% 5.1%.

In the present invention, Mg is mainly used as the molten metal.
However, the present invention is not limited to this, and other examples include low melting point metals such as Zn, Pb, and Al.

The molten metal contact portion is coated with a Ni-based or Fe-based heat-resistant material by lining a Co-based heat-resistant material. Representative examples of the Co-based heat-resistant material include Stellite # 1, # 6, and # 12. Stellite # 6 is used as a screw lining material.
From the viewpoint of workability and abrasion resistance, the material has good compatibility and is a preferable material. In addition, as the Co-based heat-resistant alloy, a Co-based heat-resistant alloy such as Haynes Alloy (trade name) can be mentioned in addition to these stellite. As an example of these components (% by weight), Co: 40 to 65%, Cr:
20-30%, Mo: up to 6%, W: up to 15%, N
i: up to 3%, Fe: up to 3%, C: up to 3%.

Further, in the present invention, the surface treatment is made different between the peak and the valley of the flight of the screw. That is, the top of the flight is coated with a Co-based heat-resistant alloy in the same manner as described above, and the valley is coated with a hard metal film by hard chromium plating, chemical vapor deposition of TiC, or metal spraying of the Co-based heat-resistant alloy. Form. Further, it is desirable to perform a film improvement treatment on the metal film by fusing, HIP or the like.

[0013]

According to the present invention, the screw outer surface that comes into contact with the molten metal (for example, Mg) has little erosion at the peak,
It is covered with a high-temperature hardness Co-based heat-resistant material (such as stellite), and is covered with a hard metal film at the valley.
The erosion resistance and wear resistance are greatly improved. The base material of the member is made of a heat-resistant Ni-based or Fe-based material having excellent heat resistance, and the high-temperature strength of the screw is ensured by the base material. Therefore, according to the present invention, it is possible to satisfy all the conditions of erosion resistance, abrasion resistance, and high-temperature strength required as a screw of a molten metal such as Mg, and the life of a screw for an injection molding machine is greatly extended. .

Next, the effect of improving erosion resistance in the present invention will be described with reference to FIG. 2. The Co-based heat-resistant material (stellite) used as a coating material in the present invention is clearly different from other comparative materials. Excellent erosion resistance. In addition, it has been shown that inconel, which is one of the Ni-based heat-resistant materials used as the base material in the present invention, is significantly damaged by direct contact with molten Mg.

According to the present invention, a hard chromium plating, a deposited film of TiC or TiN or the like, and a hard metal coating such as a metal sprayed coating of a Co-based heat-resistant alloy of 1 mm or less are formed in the valleys of the screw flight. The screw base material can be prevented from being melted or abraded by Mg or other low melting point metal, and the screw can be manufactured at low cost. Furthermore, according to the production method of the present invention, the hard metal film formed in the valley of the screw flight is subjected to the film improvement treatment, so that the film is densified and the adhesion to the flight valley is also greatly improved. In addition, since the film thickness can be increased to the range of 1 to 2 mm, the durability of the film is also improved.

[0016]

EXAMPLES The following were manufactured and used as screws for the Mg injection molding machine. Screw: As shown in FIG. 1, only a flight crest of a screw core material 5 processed into a screw shape using Inconel 718 is formed with a lining 8 having a thickness of about 2 mm by a PTA welding method using a stellite alloy. At the valley of the flight, a hard metal coating 9 is formed by plasma spraying to form C.
After lining the alloy to a thickness of about 1.5 mm and fusing at about 1000 to 1100 ° C. in a heating furnace,
A screw which had been subjected to IP treatment and provided with a wear-resistant coating having excellent adhesion was produced.

With the above screw, Mg at a temperature of about 650 ° C.
Injection molding was tested in an actual machine. As a result, no erosion or abrasion occurred during long-term use, and excellent durability was exhibited. For comparison, ASTM A288 alloy, JI
S SKD61 A screw was composed of tool steel, and a similar actual machine test was performed on this screw that had been subjected to stellite lining. As a result, almost no erosion occurred in the screw. Was reduced by tempering softening, and was inferior in durability due to bending and deformation.

[0018]

As described above, according to the present invention, M
gSatisfies all requirements for erosion resistance, abrasion resistance, and high-temperature strength required for screws for injection molding machines.
It is possible to prevent damage such as shortening of life, breakage and breakage due to melting, and to provide a reliable injection molding machine of Mg or the like.

[Brief description of the drawings]

FIG. 1 is a front view of a screw showing one embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the amount of erosion of various materials by molten Mg and temperature.

[Explanation of symbols]

 5 Screw core material 8 Stellite lining 9 Hard metal coating

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-155410 (JP, A) JP-A-60-200937 (JP, A) JP-A-60-71406 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B29C 45/17 B29C 45/58-45/62 B22D 17/20 B32B 15/01 C23C 4 / 06,30 / 00

Claims (2)

(57) [Claims] 1. A screw core material for an injection molding machine is made of a heat-resistant material based on Ni or Fe, and a Co-based heat-resistant material is lined on a surface of a screw flight ridge of the core material to form a valley of the core material. Screw for injection molding machine characterized by forming a hard metal film on the part surface 2. A screw core material for an injection molding machine is made of a heat-resistant material based on Ni or Fe, and a Co-based heat-resistant material is lined on the surface of the screw flight ridge of the core material. A method for manufacturing a screw for an injection molding machine, comprising: forming a hard metal film on the surface of a valley portion of the steel and then performing a film improvement process on the hard metal film by fusing or hot isostatic pressing.