JPS6257756A - Production of cylinder for injection molding machine - Google Patents

Abstract

PURPOSE:To obtain an excellent cylinder for an injection molding machine having high joint force between an outside cylinder and inside cylinder by pouring the melt of a high chromium cast iron into the hollow part of the outside cylinder, solidifying the melt, boring the central part of the solidified part and forming the bored part as the inside cylinder. CONSTITUTION:A carbon steel stock 1 is machined to form the outside cylinder 2 having a hollow cylindrical shape. The outside cylinder 2 is heated up to a high temp. region in a non-oxidizing atmosphere and is held at said temp. The melt of the high chromium cast iron is then poured into the hollow part of the outside cylinder 2 and is cooled together with the outside cylinder 2, by which the molten metal is solidified and a welded layer is formed at the boundary between the outside cylinder 2 and the high-chromium cast iron 3. The cylinder is further subjected to cutting and polishing or super finishing in a machining stage. The cylinder 4 clad with the inside cylinder 3a consisting of the high chromium cast iron via the welded layer on the inside surface of the outside cylinder 2 made of the carbon steel is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a cylinder for an injection molding machine.

[Prior art] Injection molding machines have been primarily used to manufacture plastic products, but in recent years they have also been used to mold corrosive plastics such as glass fiber-filled engineering plastics and fluororesin. It is also being used to mold engineering ceramics, which are in the spotlight.

Conventionally, cylinders made of nitrided steel have often been used as cylinders for injection molding machines, but due to the diversification of injection materials as mentioned in FFJ, cylinders made of nitrided steel are no longer able to provide sufficient life.

For this reason, recently, Ni or CO has been added to the inner peripheral surface of the cylinder body.
An injection molding machine cylinder coated with a base alloy has been developed.

Furthermore, the cylinder for an injection molding machine has a cylinder body made of an outer cylinder made of carbon steel, forged steel, nitrided steel, chromium molybdenum steel, or stainless steel, and a raised cylinder on the inner peripheral surface of the cylinder body. Some cylinders have a clad inner cylinder (for example, as shown in Japanese Patent Application No. 59-143148). Conventionally, the manufacturing method of this type of cylinder for an injection molding machine involves forming a hollow outer cylinder. After the hollow inner cylinder is fitted with the same inner peripheral surface by shrink fitting, the inner peripheral surface of the inner cylinder is machined so that the inner cylinder is clad on the outer cylinder.

FIG. 5 shows a conventional injection molding machine, and FIG. 6 shows the [i method] of a cylinder for a conventional injection molding machine.

In FIG. 5, 51 is a mold, 52 is a cylinder, 53 is a nozzle attached to the tip of the cylinder 52, and 54 is a cylinder 5.
A heater 55 is provided on the outer periphery of the cylinder 52, and a material input port 55 is provided on the rear outer periphery of the cylinder 52, and a hopper 56 is connected to this. Reference numeral 57 denotes a screw installed in the cylinder 52, the rear end of which is connected to a rotationally driven hydraulic cylinder 58, which is driven by a hydraulic motor 59.

In FIG. 6, reference numeral 61 indicates the material of the outer cylinder 62, which is made of carbon steel or the like, and is formed into a hollow cylindrical outer cylinder 62 by machining shown in 6a. Similarly, 62' is the material of the inner cylinder, which is made of high chromium cast iron or the like, and is machined through a heat treatment process (not shown). The inner peripheral surface of the outer cylinder 62 and the outer peripheral surface of the inner cylinder 62' are shrink-fitted 6b in a subsequent process.
It is processed with a shrink-fitting allowance that can generate shrink-fitting stress. Thus, the outer cylinder 62 and the inner cylinder 62' are shrink-fitted 6.
An integrated cylinder blank 60 is obtained in step b, and the inner circumferential surface of the intermediate blank 60, that is, the inner circumferential surface of the inner cylinder 62', has a finishing allowance 62'' corresponding to the subsequent machining process 6C.

In the machining process 6C, grinding or superfinishing is performed in addition to cutting, thereby producing a cylinder 63 in which the inner surface of the carbon steel outer cylinder 61 is clad with an inner cylinder 62' made of high chromium cast iron.

The cylinder 63 has a length of 900# and an outer diameter of 100m.

A typical example is an outer cylinder with an inner diameter of 45 mm and an inner cylinder with a thickness of 6.5 mm and an inner diameter of 32 m+.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional method for manufacturing cylinders for injection molding machines, cylinders with a narrow inner diameter and a long length are manufactured through heat treatment and shrink fitting processes. Also, shrink fitting may cause deformation of the cylinder, causing problems in subsequent machining processes.

More specifically, high-precision machining is required to obtain a uniform shrink-fit allowance over the axial rest of the outer and inner cylinders, but this process requires long hours of machining. There was a problem that it was necessary. In particular, since the inner cylinder is made of high-hardness, high-chromium cast iron, its machinability is low, and the heat treatment is also required, prolonging the machining time. Further, in the shrink fitting process, there are many difficulties involved in uniformly heating a long outer cylinder in the axial direction, accurately inserting the inner cylinder in hot conditions, and uniformly cooling the inner cylinder.

Further, as mentioned above, there is a problem in that machining of high-hardness materials is extremely difficult due to deformation of the cylinder during the manufacturing process.

The present invention solves these conventional problems,
It is an object of the present invention to provide an excellent method for manufacturing a cylinder for an injection molding machine that does not deform the cylinder and has a high bonding force between an outer cylinder and an inner cylinder.

[Means for Solving the Problems] In order to achieve the above object, the present invention has a cylinder body made of an outer cylinder made of carbon steel, forged steel, nitrided steel, chromium molybdenum steel, or stainless steel. In a cylinder for an injection molding machine whose inner peripheral surface is clad with an inner cylinder made of high chromium cast iron, the outer cylinder is held in a high temperature region in a non-oxidizing atmosphere, and then a high chromium cast iron is placed in the hollow part of the outer cylinder. After pouring the molten metal and cooling and solidifying it together with the outer cylinder to form a fused layer at the interface between the outer cylinder and the high chromium cast iron, a hole is drilled in the center of the solidified part to form an inner cylinder and an outer cylinder. It is designed to have a cladding.

[Function] With the above configuration, the present invention has the following effects. That is, the outer cylinder is heated to a high temperature range in a non-oxidizing atmosphere to maintain humidity, and then molten high chromium cast iron is poured into the hollow part of the outer cylinder, and cooled together with the outer cylinder to solidify the molten metal. A fusion layer is formed at the interface between the outer cylinder and the high chromium cast iron. At this time, the molten S temperature is higher than the outer cylinder temperature, the molten metal melts near the inner peripheral surface of the outer tube, and as solidification progresses, a fused layer is formed at the interface.

After that, a hole is drilled in the center of the solidified part of the high chromium cast iron by machining to create an inner cylinder with a fused layer on the outer circumferential surface and a machined surface on the inner circumferential surface. can get.

Therefore, according to the present invention, the complicated work for conventional shrink fitting can be omitted, the deformation of the cylinder material can be greatly reduced, the post-process machining can be facilitated, and the The machining time can be reduced. Furthermore, since the above-mentioned fusion layer is formed in the cylinder, the outer cylinder and the inner cylinder are integrated with high bonding force. In addition, since the inner cylinder is made of high chromium cast iron with excellent wear resistance, its lifespan can be significantly increased.

[Example] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention.

In FIG. 1, reference numeral 1 designates the material of the outer cylinder 2, which is made of 0.3% carbon steel, etc., and is machined into a hollow cylindrical shape by machining. Subsequently, in the process, the outer cylinder 2 is heated to a high temperature range in a non-oxidizing atmosphere to maintain the temperature, and then molten high chromium cast iron is poured into the hollow part of the outer cylinder 2 and cooled together with the outer cylinder 2. By solidifying the molten metal, a fused bamboo layer is formed at the interface between the outer cylinder 2 and the high chromium cast iron 3. 30 indicates a cylinder material, and a solidified part of high chromium cast iron 3 is formed in the hollow part of the outer part n2. Furthermore, in the machining process C, grinding or super finishing is performed along with cutting, thus forming a cylinder 4 in which an inner cylinder 3a made of high chromium cast iron is clad on the inner surface of an outer cylinder 2 made of carbon steel via a fusion layer. lJ! It will be built.

As a representative example, the cylinder length is 900#, the outer diameter is 100av, and the inner diameter is 45M, and the inner cylinder is 6.5# thick and the inner diameter is 32#.

Next, FIGS. 2 and 3 show the structure of the process shown in FIG. 1 in detail.

In Fig. 2, 2 indicates the outer cylinder after step a, and 1
0 is a heating furnace, 11 is a hearth of the heating furnace 10, and 12 is a furnace cover of the heating furnace 10, which is detachable from the heating furnace 10. A heating source is provided on the inner wall of the heating furnace 10, and 11 is a heating coil serving as the heating source. Vibrator 1 is installed on the furnace cover 12.
3 and a regulating valve 15 to supply an inert gas 14 to the heating furnace 1.
Introduce within 0. Reference numeral 16 denotes a relief vibrator attached to the furnace cover 12, which purges air etc. stagnant in the heating furnace 10 when the inert gas 14 is introduced into the heating furnace 10. In this way, it is possible to maintain the inside of the heating furnace 10 in a non-oxidizing atmosphere.

Note that as the inert gas 14, a stable rare gas such as argon is used.

The outer cylinder 2 is placed on a stand 18 placed on the hearth 17. It is installed perpendicularly to L and heats to a high temperature region of about 1000° C. in a non-oxidizing atmosphere by introducing an inert gas 14 and maintains the temperature.

In FIG. 3, a state in which high chromium cast iron 3 is poured into the hollow part of the outer cylinder 2 is shown.

In FIG. 3, the outer cylinder 2 in the heating furnace 10 has a diameter of approximately 100 mm.
The temperature is maintained by heating to a high temperature range of 0°C. Under this condition, the separately melted high chromium & 61 molten metal is heated to about 1500°C from the nozzle 19 into the hollow part of the outer cylinder 2 by the ladle 20. The molten metal is poured under the Note 4 temperature, and then cooled together with the outer cylinder 2 to solidify the molten metal. The stress is removed and its mechanical properties are improved, and the cylinder material 30 is then left to cool.

In this manner, heat transfer to the outer cylinder due to pouring of high chromium cast iron causes the vicinity of the inner circumferential surface of the outer cylinder to rise in temperature and melt, and as it cools and solidifies, a fused layer is formed at the interface between the two.

Heating the outer cylinder to approximately 1000°C in a non-oxidizing atmosphere and maintaining the temperature minimizes the difference between the amount of shrinkage during solidification and cooling of high chromium cast iron and the amount of shrinkage of the outer cylinder, and also achieves the above-mentioned This is to increase the internal activity in the vicinity of the interface of the outer cylinder, to prevent the depletion and melting of the CP, and to ensure the formation of a fused layer.

FIG. 4 shows a metallographic photograph (x 448) of a cylinder based on the above embodiment. Outer cylinder material is 03%C carbon steel.
The inner cylinder material is 3%027%Cr high chromium cast iron.

The outer cylinder structure has a ferrite and barley structure, and the inner cylinder structure has carbides dispersed in the martenreit and osdenite structure. Furthermore, it shows that a fused layer with a constant thickness is formed at the interface.
Moreover, the presence of an oxide layer in the outer cylinder cannot be detected.

Furthermore, according to the experimental data based on the above embodiment, the welding rate of the cross section at each position in the axial direction of the cylinder material 30 is 100%, and 50 to 70% near both ends of the cylinder material 30. It's showing. child)
The welding rate was defined as the ratio of the detected length to the interface circumference when the interface in each cross section was detected using a fluorescent penetrant test.

A3, the degree of curvature of the cylinder material with a length of 900M was about 0.5 μm at the center.

In addition, when a tensile test was conducted using a tensile test piece taken from the cylinder material 30, the tensile strength was approximately 38 kg/-, and the specimen broke at a position approximately 1 m away from the interface toward the higher chromium tjj iron side. The tensile strength of carbon steel is approximately 45Kg/NR
2. The tensile strength of high chromium cast iron is 40 to 50/mm2, and the tensile strength of the cylinder material is approximately 10% lower than that of high chromium cast iron.

As can be seen from the above experimental data, according to the manufacturing method of the present invention, a fused layer without an oxidized layer is formed at the interface between the inner cylinder and the high chromium cast iron, and is formed fairly uniformly in the axial direction. It has been found that since the adhesive layer has sufficient strength to fasten the two together, the inner cylinder does not rotate, move, or fall off due to operation of the injection molding machine.

Note that the aspect of the cylinder body used in the present invention is not limited to the carbon steel of the above-mentioned embodiments, but may be applied to an outer cylinder made of forged steel, nitrided steel, chromium molybdenum steel, or stainless steel. .

[Effects of the Invention] As is clear from the above embodiments, the present invention forms a clear fusion layer at the interface between the outer cylinder and high chromium cast iron, clads the inner cylinder with the outer cylinder, and It has excellent bonding strength, can sufficiently withstand the operating conditions of an injection molding machine, and can significantly extend its life.

Furthermore, it has great effects such as facilitating machining and shortening the overall machining time.

[Brief explanation of drawings]

Figure 1 is a process diagram of an embodiment of the present invention, Figures 2 and 3 are detailed explanatory diagrams of the same process, Figure 4 is a photograph of the metallographic structure of the same cylinder, and Figure 5 is a conventional injection molding process. The structural diagram of the molding machine and FIG. 6 are diagrams of the manufacturing process of the same cylinder. 2...Outer tube 3...High chromium cast iron 3a
... Inner cylinder Applicant: Kawasaki Heavy Industries, Ltd. Figure 1 Figure 2 Figure 3 Figure 5 IXI 5 et al. Figure 6

Claims (1)

[Claims] For injection molding machines in which the cylinder body is made of an outer cylinder made of carbon steel, forged steel, nitriding steel, chromium molybdenum steel, or stainless steel, and the inner peripheral surface of the cylinder body is clad with an inner cylinder made of high chromium cast iron. In the cylinder, the outer cylinder is held in a high temperature region in a non-oxidizing atmosphere, and then molten high chromium cast iron is poured into the hollow part of the outer cylinder, and is cooled and solidified together with the outer cylinder. A method for manufacturing a cylinder for an injection molding machine, characterized in that after a fused layer is formed at the interface with chromium cast iron, a hole is drilled in the center of the solidified part to form an inner cylinder and the outer cylinder is clad.