JPH0140911B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface treatment of a screw for a synthetic resin molding machine.

Resin molding machines and extruders for molding, extruding, and producing films of synthetic resins have a cylinder and a screw as a pair. While transporting the resin pellets to be molded, the screw serves many purposes and functions, such as heating, kneading, plasticizing, accumulating and adjusting extrusion pressure, and regulating the amount of extrusion.

During use of the screw, the flight of the screw comes into contact with the cylinder, and due to this contact, the screw generates frictional heat, and depending on the resin used, it gets into the heated parts of the screw and cylinder, causing carbonization or burning, resulting in black color and Discolors to reddish brown. This discolored resin appears in the form of spots or streaks on the molded resin or film, significantly reducing the commercial value.

The object of the present invention is to prevent discoloration caused by resin burning, which appears in the form of spots or streaks on resins and films.

It has been found that resin burning can be avoided if local heat generation at the contact area between the screw and the cylinder is prevented.

Therefore, the present inventors have developed metal carbides, oxides, nitrides, borides, etc., which have a small coefficient of friction with metals.
We considered covering the surface of sculilite with silicides, sulfides, etc. And as a method, carbides, oxides, nitrides of the above metals are added to the low melting point alloy powder,
By blending powders of one or more of borides, silicides, and sulfides, and then using a powder overlay welding machine, the blended powder is passed through a flame and overlaid onto the surface of the screw light, thereby forming the metal. It is possible to expose a large amount of metal carbides, oxides, nitrides, borides, silicides, sulfides, etc. on the surface, which have a small coefficient of friction with the cylinder.As a result, the heat generated by contact between the cylinder and the screw is minimized. The present invention was achieved by discovering that resin burning can be prevented.

That is, the present invention provides powder of one or more metal oxides, carbides, nitrides, borides, silicides, and sulfides, which have a small coefficient of friction with metal, on the flight surface of a screw for a synthetic resin molding machine. ,
Powder overlay welding is performed on a mixture with an alloy powder with a lower melting point than this, and only the alloy with a lower melting point is melted on the flight surface, and the above oxides, carbides, nitrides, borides, silicides, and sulfides are not melted. The present invention relates to a surface treatment method for screws, which is characterized in that the screws are uniformly dispersed.

Metal oxides, carbides, nitrides, borides, which have a small coefficient of friction with the metal used in the present invention,
Examples of silicides and sulfides include the following. In other words, oxides include alumina, titania, chromia, etc., carbides include tungsten carbide, niobium carbide, titanium carbide, etc., nitrides include boron nitride, titanium nitride, etc., and borides include boron carbide and borides. Titanium, etc., and silicates include zirconium silicate,
Examples of sulfides include silicon nitride, molybdenum disulfide, and vanadium sulfide.

These have high melting points of over 2000°C.

On the other hand, as a low melting point alloy, the melting point is approximately 950 ~
Ni-Cr-B-Si system, Co-Ni-Cr in the range of 1100℃
In addition to self-fusing alloy powders for thermal spraying such as -B-Si series and Co-Ni-Cr-Fe-B-Si- series, JIS Z3261B Ag 1
Examples include silver solder of ~8A, phosphorous solder of JIS Z3264B Cu P1~5, and solder specified in JIS Z3282, but the oxides, carbides, nitrides, borides, silicides, and sulfides used Any material can be used as long as it has a melting point lower than the melting temperature and does not cause chemical reactions or eutectic reactions during the welding process. Depending on the heat source used and the welding method, iron powder or stainless steel powder may also be used. Available for use.

The mixing ratio of the low-melting point alloy powder and oxides, carbides, nitrides, borides, silicides, and sulfides used in the present invention can be varied from 10 to 90% by volume, but the processability and friction coefficient can be reduced. It is preferable that the proportion of the low melting point alloy powder is 10 to 60% by volume.

Also, low melting point alloy powders, oxides, carbides,
80 for each powder of nitride, boride, silicide, and sulfide
Any powder having a particle size of 280 mesh or more is sufficient, and the particle size can be selected so that it can be fed to the powder supply device of the powder overlay machine, and powder of around 280 mesh is generally used. Further, the overlay welding machine may use any heat source such as flame, plasma, or arc, but the required condition is that it is capable of overlaying with powder.

The method of the present invention will be explained using FIGS. 1 and 2.

Figure 1 shows an overview of a screw for a resin molding machine.
FIG. 2 is an enlarged cross-section of the screw flight part, where 110 shows the base, 111 the rising part of the screw, and 112 the top surface of the flight.

In the present invention, as described above, as a means for reducing the contact resistance between the screw and the cylinder in a resin molding machine or a film molding machine and preventing the occurrence of burns,
It is characterized by covering the flight surface with metal oxides, carbides, nitrides, borides, silicides, sulfides, etc. that have a low coefficient of friction with metals. Methods such as CVD, PVD, and brazing can be considered for this method, but in this method, oxides, carbides, nitrides, and Powders such as compounds, silicides, and sulfides are blended and overlaid on the screw light part.
A large amount of the oxides, carbides, nitrides, borides, silicides, sulfides, etc. having a low coefficient of friction, which are fixed to the alloy with a low melting point, are exposed on the surface of the flight.

As mentioned above, the melting points of both powders are more than twice as different, and by utilizing this difference in melting point, a type of metal oxide, carbide, nitride, boride, silicide, or sulfide can be added to the self-fusing alloy powder. Alternatively, by blending two or more types and overlaying using a powder overlay welding machine, only the self-fusing alloy is melted, and one or two of the blended oxides, carbides, nitrides, borides, silicides, and sulfides are melted. The seeds are dispersed unmolten into the matrix of the self-fusing alloy. By grinding these welded films, particles of metal oxides, carbides, nitrides, borides, silicides, and sulfides, which have a low coefficient of friction with metal, are uniformly distributed on the surface of the screw flight surface. distributed. This results in
It is now possible to prevent resin burning that occurs with conventional stellite, nitriding, and carburizing treatments.

Example 1 FIG. 1 shows a screw for an injection molding machine. Although this product satisfies the specifications in terms of performance and capacity in resin molding, resin burning occurred during the specific resin molding (vinyl chloride). Figure 3 is the second
The flight surface 112 shown in the figure is processed to leave 10% of the flight width at each end 1126, and a groove 220 with a depth of 1 mm and a side surface of 1R is provided. Attach this screw to a jig that can rotate freely, and after preheating the screw to 300℃,
Base self-fusing alloy (C=0.2%, Si=3.5%, Cr=18
%, B=3%, Fe=25%, Mo=6, Co=40%,
Mix 25Vol% + SiN75Vol% powder (approximately 270 meshes) with Ni (remaining) and overlay into the groove 220 by powder overlay welding using an oxy-acetylene flame, and after cooling, reach the specified dimensions. processed. When this was incorporated into an injection molding machine and vinyl chloride resin was molded, good results were obtained with no resin burning. FIG. 4 shows a screw light that has been machined to a predetermined size after overlaying 230 in the groove 220.

Example 2 A screw having the same shape as that shown in Fig. 1 was used for about 5 years, and the flight part was worn out and the initial design performance was no longer achieved. Therefore, Ni-based self-fusing alloy powder (Cr = 12%, B = 2.5%, Si = 3.5%, C = 0.5%,
Fe=2%, Co=0.5%, balance Ni) and TiC50Vol%
It was mixed and overlaid using a plasma flame overlay method in the same manner as in Example 1, and it was installed in the same machine and used for about one year, but no particular wear was observed.

Example 3 During ABS resin molding in a bend injection molding machine,
Black spots appeared on the molded product, so I polished off the outer diameter of the flight of the screw by 0.5 mm (one side) and applied boron carbide: chromium oxide: Ni-based self-fusing alloy (Cr = 15%, B = 3) to this area. %, Si=4%, C
≒0.5%, Fe=3%, Co=1%, balance Ni) 4:
Powder blended at a weight ratio of 3:3 (approximately 280 mesh particles each) is overlaid by approximately 1.0 mm using an oxy-acetylene flame powder overlay machine and processed to the specified size.
When ABS resin was molded again, good results were obtained with no seizure of the resin.

[Brief explanation of drawings]

Fig. 1 is a general view of a screw for a resin molding machine, Fig. 2 is an enlarged cross-sectional view of the screw flight part, and Figs. 3 and 4 are cross-sectional views for explaining the method of the present invention. .

Claims (1)

[Claims] 1 The flight surface of the screw for synthetic resin molding machines is coated with metal oxides, which have a small coefficient of friction with metals.
A mixture of one or more powders of carbides, nitrides, borides, silicides, and sulfides and an alloy powder with a lower melting point is powder overlay welded, and only the alloy with a lower melting point is melted on the flight surface. and the above oxides, carbides, nitrides, borides, silicides,
A method for surface treatment of screws, characterized in that sulfides are uniformly dispersed without being melted.