JPH02182802A - Method and device producing metallic sintered member - Google Patents

Abstract

PURPOSE:To produce the high-precision metallic sintered member at a low cost with the small-scale device by filling a plastic kneaded body consisting of raw metal powder, a water-soluble org. binder and water into a degassed metallic mold and heating and sintering the obtained formed product. CONSTITUTION:Raw metal powder (preferably water-atomized powder having about 1.0-20mu average particle diameter), a water-soluble org. binder and water are kneaded to prepare a plastic kneaded body. The kneaded body is charged into an extrusion cylinder 1-3 from a feed port 1-1, and filled into a degassed metallic mold 1-4 by an extrusion screw 1-2 to obtain a formed product of the combined kneaded body having a shape similar to the cavity. The formed body is cut by a cutting knife 1-12, and discharged from the mold 1-4 by an ejector pin 1-11. The discharged formed body is heated to remove the binder, and compacted by sintering. By this method, a thick metallic sintered member is semicontinuously produced with high precision by the small-scale device, and the cost is drastically reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for manufacturing a sintered metal member.

[Conventional technology]

In the field of materials such as metals and ceramics, there are many thick-walled members.

Among these, metal materials manufactured through melting and casting processes are manufactured by methods such as steel cutting and die forging. In addition, in the production of metal materials using ceramics and powder metallurgy methods, press molding and cold isostatic press molding (hereinafter referred to as CIP molding) are the main methods, and manufacturing by injection molding or extrusion molding has also been attempted in some cases. .

Problems to be solved by the invention C] Among the conventional techniques, the cutting process method starts with melting and casting, which inevitably increases manufacturing costs, and the more complex the shape of the product, the higher the processing cost. is also significantly higher. Additionally, die forging has limitations on the shapes that can be manufactured.

The CIP molding method uses a rubber mold, so
Press molding, which is not industrially viable due to low dimensional accuracy and low mass productivity, is a process in which the powder in the mold is pressurized with upper and lower punches, as shown in Figure 2. There is a limit to the shape, and it is not suitable for molding relatively complicated shapes. Furthermore, in extrusion molding, raw materials are continuously extruded from an extrusion die to form the product as shown in FIG. 3, so the product shape is limited to one with a constant cross-sectional shape in the length direction.

Furthermore, the injection molding method, which has been attracting attention in recent years, can mold products with relatively complex shapes, but there is a limit to the wall thickness that can be manufactured using this method, especially if the cavity space is wider than the nozzle diameter. Or, in the case of an article having a shape that does not exert squeezing or shearing action on the kneaded material in the flow direction of the kneaded material, the fourth
Jetting occurs in which the kneaded material ejects in a string shape as shown in the figure, and defects occur inside the molded product.

Even if molding were possible, thick-walled products require a large mold capacity, so it is inevitable that the injection mechanism would be larger and the mold clamping pressure would increase, making the molding machine very large and expensive.

In view of these problems, the present invention aims to provide a method and apparatus for producing thick-walled metal sintered parts having a relatively complicated shape by extrusion molding at low cost and with high precision using a smaller-scale apparatus. It is something.

[Means to solve the problem]

The present invention involves kneading raw metal powder, a water-soluble organic binder, and water to form a plastic kneaded body, and then placing the kneaded body in a mold that is directly connected to a cylinder and deaerated, and then extruded by the rotation of a screw. A metal sintering method is characterized in that after a molded body is obtained by joining a kneaded body with a shape similar to the cavity, the binder is removed from the molded body by heating, and the molded body is consolidated by sintering. This is a method for manufacturing a binding member.

Further, in the present invention, the kneaded body filled in the mold is mainly bonded by the adhesive force of the binder present on the surface of the kneaded body, and the raw metal powder is 50 μm thick, and the desired final product is formed. The invention is characterized by the use of one or more prealloy powders having a composition substantially corresponding to the composition of the present invention.

The apparatus for filling and molding the kneaded material into a mold consists of a cylinder, a screw that rotates within the cylinder and applies an extrusion force to the kneaded material, and a mold that is directly connected to the cylinder and has an opening/closing and degassing mechanism. It is characterized by becoming.

As a raw material powder, ensure uniform dispersion of the powder at the time of crosstalk,
Water atomized powder with a particle diameter of 50 μm or less is preferable in terms of ensuring the strength of the degreased body of the molded body and improving the sintered density. However, if the particles are too fine, it becomes difficult to remove the binder, so it is more desirable that the average particle size of the water atomized powder is 1.0 to 20 μm.

As a device for filling the kneaded material into a deaerated mold, a screw type extrusion molding machine with the extrusion die removed is used. As a result, the kneaded material becomes lumpy, and the filling into the mold becomes intermittent, giving a shearing effect to the kneaded material, creating a new surface on the surface of the kneaded material, and ensuring reliable bonding of the kneaded materials to each other. It will be done.

As described above, a particularly important point among the features of the present invention is that an extrusion die, which is normally attached to a screw type extrusion molding machine, is not attached to the extrusion molding machine, and the cylinder containing the screw is directly connected to the mold. The point is that a molding machine is used.

Another important point of the present invention is that when an extrusion molding machine such as the one described above is used and the screw is used to fill the mold directly from the cylinder, the kneaded material is affected by the shear stress during extrusion of the screw, and the kneaded material is absorbed by the mold. It is subject to shear stress due to discontinuity when filling.

The present invention has found that a plastic kneaded body made by kneading metal powder, a water-soluble organic binder, and water can be easily crimped under the above-mentioned shear stress at low pressure almost solely by the adhesive force of the binder. This was achieved based on results.

As explained above, since the kneading rods that are intermittently extruded from the extrusion molding machine of the present invention are bonded to each other by the bonding force of the binder, the kneading material remains substantially filled in the mold. No pressure is required.

For the final compression, pressure is applied by the extrusion force generated by the rotation of the screw after the kneaded material is filled into the mold, and a method of solidifying the kneaded material by heat is not used. Therefore, there is no limit to the filling speed into the mold.

Further, in order to make the kneaded bodies extruded into the mold more closely bonded to each other, it is necessary to keep the inside of the mold in a deaerated state.

The solidification mechanism of the compact basically utilizes the evaporation of moisture by degassing after the kneaded bodies are joined, and if further strength of the compact is required, the mold is heated after molding to remove moisture. You can.

Examples of product shapes suitable for the present invention include thick-walled products that are prone to molding defects such as jetting when injection molding is used, and products that cannot be shaped or have poor precision when using CIP molding.

〔Example〕

The present invention will be explained in detail with reference to examples and drawings.

A water atomized preliminary alloy powder having a composition equivalent to Al5rT15 was prepared. The average particle size is 45 μm and the C content is 1.
．． 5%, 0. The content was 2000 ppm. 0.3% of graphite powder was added to the powder, and mixed and pulverized using a dry attritor to give an average particle size of 15 μm.

Methylcellulose (Shin-Etsu Chemical 5M400) is added to this powder.
3%, water 8%, microcrystalline wax 2%
, stearic acid emulsion 1%, glycerin 0.7%
was added to prepare a preliminary kneaded body using a Henschel mixer, and then kneaded for 15 minutes using a kneader kneader to obtain a kneaded body.

This kneaded body was molded into a mold with an outer diameter of 25 Mφ and a helix angle of 30 @ lead 152 in a vacuum mold using the molding machine shown in Fig. 1.
A green molded body for an end mill between the two was obtained.

Fig. 1 shows the molding apparatus used in the embodiment of the present invention.
1-1 in the diagram is the raw material input port, 1-2 is the extrusion screw
1-3 indicates an extrusion cylinder, 1-4 a mold, 1-5 a parting line, and an undercut portion is formed by an angular pin l-6 and a slide core 1-7. The mold structure is similar to general plastic molds, with a mold opening/closing cylinder 1-8 opening and closing the mold, and an ejector cylinder 1-9 opening and closing the mold with an ejector plate 1-9.
10, the molded body is ejected from the mold by an ejector turbine 1-11. Before ejecting, a cutting step is performed in which the molded body is cut out using the cutting blade 1-12. The completion of filling molding is detected by a pressure sensor 1-13 installed inside the mold.

When the molded product obtained by the above apparatus was subjected to X-ray inspection and destructive inspection, no internal defects such as bubbles, cracks, and unpressed areas were found. The appearance was also normal.

This molded body was heated to 500°C in a hydrogen atmosphere, and
After holding for a time to remove the binder, the temperature was raised to 1220°C in a vacuum of 10' Torr, and sintering was performed by holding for 2 hours. The density of the sintered body was 8.21 g/att, which was approximately the true density, and no abnormalities were observed in the XM inspection, destructive inspection, and visual inspection.

Furthermore, the dimensional accuracy was within ±0.5% for each dimension, which was at the same level as other injection molded sintered parts.

As a comparison process, molding was performed using the same kneaded body and equipment as in the example without evacuation of the inside of the mold, and as a result of inspecting the molded body, no abnormality was observed in the appearance, but a destructive test was performed. However, bubbles and unbonded areas were confirmed.

Although the molded body was subjected to binder removal and sintering, the bubbles and unpressed areas observed in the molded body remained as defects.

Furthermore, using the same kneaded body and mold as in the example, molding was performed using a plunger type extrusion molding machine. The appearance of the obtained molded product showed many unbonded parts, xm
Many defects were also found through inspection and destructive testing.

Although this embodiment deals with the case where the raw material powder is high-speed tool steel, it goes without saying that the present invention is applicable not only to high-speed tool steel but also to stainless steel and other steels.

〔Effect of the invention〕

According to the present invention, thick-walled sintered metal parts, which conventional methods have many problems with in terms of quality, precision, and cost, can be manufactured semi-continuously using small-scale equipment.Moreover, due to the high precision, the manufacturing cost can be significantly reduced. This can be reduced and is of great industrial benefit.

Furthermore, there is a manufacturing apparatus for a metal sintered member according to the present invention.

Since a pressurizing mechanism is not substantially required, it is much more compact and can be manufactured at a lower cost than an injection molding machine or a CIP molding machine, and has great industrial value.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the molding apparatus according to the present invention, Fig. 2 is a sectional view of powder press molding, Fig. 3 is a sectional view of extrusion molding, and Fig. 4 is an example of jetting by injection molding. FIG. 1-1=raw material input port, 1-2: extrusion screw 1-3:
Extrusion cylinder, 1-4: Mold, 1-5: Parting line, 1-6: Angular bin, 1-7 = Slide core, 1-8: Mold opening/closing cylinder, 1-9: Ejector cylinder, 1- 10: Ejector plate, l-117
Engine turbine, 1-12: Cutting blade, 1-13: Pressure sensor Fig. 2/1 revised 2' U4: / Fig. 3 Fig. 4

Claims (1)

[Scope of Claims] 1. After kneading raw metal powder, a water-soluble organic binder, and water to form a plastic kneaded body, the kneaded body is directly connected to a cylinder and placed in a deaerated mold with a rotating screw. The molded body is filled with an extrusion force of A method for manufacturing a sintered metal member. 2. The method for manufacturing a metal sintered member according to claim 1, wherein the kneaded bodies filled in the mold are joined mainly by the adhesive force of the binder present on the surface of the kneaded bodies. 3. Production of a metal sintered member according to claim 1 or 2, characterized in that the raw metal powder has a diameter of 50 μm and uses one or more pre-alloyed powders that substantially match the composition of the desired final product. Method. 4. A device that fills a mold with a kneaded material obtained by kneading raw metal powder, a water-soluble organic binder, and water and molds the material, comprising a cylinder, a screw that rotates within the cylinder, and a cylinder that applies extrusion force to the kneaded material. 1. An apparatus for manufacturing a metal sintered member, comprising a mold having an opening/closing and degassing mechanism directly connected to the mold.