JPH0438829B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method of manufacturing a member made of a high carbon, cobalt-based alloy, and particularly to a method of molding a member of a desired shape from the alloy using powder metallurgy technology. <Conventional technology> Based on 0.5 to 5.0% by weight of C and 40% by weight or more of Co, this is combined with Cr, Ni, W, Mo, V, Nb, Ti, Fe.
High-carbon, cobalt-based alloys prepared by appropriately adding various components such as 1-2-2-3 are attracting attention as materials for severe applications because they have excellent high-temperature hardness, wear resistance, and corrosion resistance. However, this type of material has high deformation resistance and poor toughness, so it has been thought that plastic working is impossible. Therefore, conventionally, desired members have been manufactured by welding methods such as overlaying or thermal spraying, or by casting methods. <Problems to be Solved by the Invention> In general, manufacturing methods such as welding and casting can only produce products in a state where the molten material remains solidified, so internal defects may be present during solidification or the structure may be non-uniform. As a result, the properties of the metal cannot be fully demonstrated. In particular, in high-carbon, cobalt-based alloys, eutectic carbides coarsely aggregate during solidification and are unevenly dispersed in the matrix.
Since internal defects such as pores are likely to coexist, the quality characteristics of the alloy, such as wear resistance, corrosion resistance, and high temperature hardness, are all extremely low. In addition, with the welding method, it is extremely difficult to weld the inner surface of relatively thin pipes with an inner diameter of 70 mm or less or relatively long pipes with a length of 1 m or more, and the work efficiency is low, and the casting method is difficult to weld the inner surface of relatively thin pipes with an inner diameter of 70 mm or less or relatively long pipes with a length of 1 m or more. The form of the product is severely restricted, such as not being able to manufacture it. This invention aims to solve the above-mentioned quality problems of products caused by melting and solidification, alleviate constraints imposed by the form of manufactured products, and increase productivity. <Means for Solving the Problems> In the present invention, first, an alloy whose basic components are 0.5 to 5.0% by weight of carbon and 40% by weight or more of cobalt is powdered. Next, this alloy powder is filled into a metal capsule and sealed, and then heated to pre-sinter the alloy powder inside the capsule. Then, this is further heated by induction heating, loaded into a hot extruder, and subjected to plastic working by extrusion. Here, the composition of 0.5 to 5.0% by weight of carbon and 40% by weight or more of cobalt is based on the composition of well-known high carbon, cobalt-based alloys, and as is also well-known, Cr, Ni, W, Mo, V , Nb, Ti, Fe, and other components are appropriately selected and added. As a powdering method, an atomization method that involves rapid cooling is appropriate so that the carbide is finely and uniformly dispersed and the crystal grains of the matrix are also made fine. The gas atomization method that produces powder is optimal. In order to increase the filling rate in the capsule and facilitate heating, it is desirable to mix various types of particles with a particle size of about 1000 μm or less. As the capsule, any metal that is easy to work with, including mild steel and rust-free steel, can be used. If the product is a rod or tube consisting solely of high carbon, cobalt-based alloys, a cylindrical or double cylindrical thin-walled capsule is used. If the product is a cladding material of a high carbon, cobalt-based alloy and an ordinary metal, the appropriate thickness of the metal used to form the cladding material is used as part of the capsule wall or in the core. Once the powder raw material is filled into the capsule, the capsule is sealed and the inside is evacuated if necessary. Hot extrusion is carried out after heating the powder raw material in the capsule to 1150 to 1200°C. At this time, if the powder raw material is left at an appropriate temperature for a long time, the carbides and crystal grains will become coarse, so heating and extrusion processing must be carried out as quickly as possible. In order to help raise the temperature of the raw material powder, it is desirable to perform cold isostatic pressing after filling it into capsules. By doing this, the packing density of the powder is
Increases from 60-65% to 65-70%, improving thermal conductivity for pre-sintering. Induction heating is the best way to rapidly heat the raw powder inside the capsule to the extrusion temperature. but,
In powder raw materials, even if the packing density is increased as described above, induced current does not easily flow therein. Therefore, prior to induction heating, the capsules are heated to over 700℃,
It is necessary to pre-sinter the powder inside. Once the capsule reaches a certain temperature through induction heating, immediately apply glass lubricant to the entire surface.
Load into a hot extruder and process. <Function> The powder raw material filled into the capsule is compressed by cold isostatic pressing as necessary to increase the packing density, the pre-sintering makes it easier for induced current to flow, and induction heating quickly lowers the processing temperature. The temperature is raised to
undergoes hot extrusion processing. In this way, the process from temperature elevation to hot extrusion progresses extremely quickly, and as a result, the growth of carbides and matrix grains constituting the alloy is suppressed.
For this reason, hot extrusion processing is now possible even for high carbon, cobalt-based alloys that were conventionally thought to be impossible to plastically work. <Example> As shown in FIG. 1, when a cylindrical metal capsule 1 is filled with high carbon, cobalt-based alloy powder 2 and hot extruded, a thin metal layer originating from the capsule 1 is A coated alloy bar is obtained. The metal coating is removed by grinding, etc. before use. As shown in FIG. 2, when filling an alloy powder 5 between the inner and outer cylinders of a double cylindrical capsule consisting of an outer cylinder 3 and an inner cylinder 4 and hot extruding it, a thin metal layer is formed on the inner and outer surfaces. An alloy tube is obtained. If necessary, remove the metal coating on the inner, outer, or both surfaces before use. As shown in FIG. 3, when a cylindrical metal capsule 7 having a core 6 made of a suitable metal is filled with alloy powder 8 and hot extruded, the outer surface is covered with a thin metal layer. You will get ivy clad rods.
Although it is used by removing the metal coating on the outer surface, it is reinforced by the inner metal core to achieve high mechanical strength. As shown in FIG. 4, when an alloy powder 11 is filled between the inner and outer cylinders of a double cylindrical metal capsule consisting of a thin outer cylinder 9 and a thick inner cylinder 10, and this is hot extruded, , a clad tube is obtained whose outer surface is covered with a thin metal layer. Although it is used after removing the metal coating on the outer surface, it is reinforced by the metal layer originating from the inner cylinder 10, so that high mechanical strength can be obtained. As shown in FIG. 5, when an alloy powder 14 is filled between the inner and outer cylinders of a double-cylindrical metal capsule consisting of a thick-walled outer cylinder 12 and a thin-walled inner cylinder 13, and this is hot-extruded, , a clad tube with a thin metal layer adhered to its inner surface is obtained. Although it is used after removing the metal coating on the inner surface, it is reinforced by the metal layer originating from the outer cylinder 12, so that high mechanical strength can be obtained. As shown in FIG. 6, an alloy powder 18 is filled into a thick metal capsule 17 having cylindrical cores 15 and 16 of the same diameter made of a suitable metal, and then hot extruded. When the cores originating from the cores 15 and 16 of the extruded product are removed by machining and the resulting hole surface is finished, as shown in FIG. It is possible to obtain an envelope for a twin-shaft extruder, which has the following structure and is surrounded by a reinforcing metal cylinder 21 on the outside. Next, the properties of examples in which the present invention was applied to high carbon, cobalt-based alloys of various compositions will be explained. Example 1 and Comparative Example Using a capsule having the structure shown in the fourth diagram,
The interior was filled with gas atomized powder (average particle size 150μ) of an alloy having the composition shown in Table 1. The specifications of the capsule are as follows. Total length: 400 mm Outer cylinder: outer diameter 151 mm, inner diameter: 147 mm, material: S20C Inner cylinder: outer diameter: 74 mm, inner diameter: 40 mm, material: STBA24 Powder filling rate: 62% The results of compressing the above capsule using a cold isostatic press are as follows. Total length 400mm Outer cylinder 149mm outer diameter, 145mm inner diameter Inner cylinder 74mm outer diameter, 40mm inner diameter Powder filling rate 65% This was heated to 800℃ in an atmosphere furnace and then heated to 1180℃.
The sample was heated by induction and loaded into a hot extruder having a cylinder with an inner diameter of 160 mm to carry out extrusion processing. The dimensions of the product, including the metal coating on the surface, are as follows. Outer diameter 58mm, border diameter 42mm, inner diameter 34mm, length 3.7
m As shown in Table 1, Comparative Examples 1A, 1B, and 1C were manufactured with alloys having virtually the same composition as Example 1. Comparative example 1A is a gas atomized alloy powder with an average particle size of 150μ and molded by hot pressing at 1150°C and 1000 kg/ ^cm2 , comparative example 1B is a cast material, and comparative example 1C is a cast material.
is a thermal spray material.

[Table] As shown in FIG. 8, in the sintered alloy part of the product of Example 1, carbide and matrix crystal grains did not grow much. On the other hand, in the case of the product of Comparative Example 1A, even though the same raw material powder was sintered, as shown in FIG. 9, carbides and matrix crystal grains grew long and thin. Furthermore, comparative examples
In the case of products 1B and 1C, as shown in FIGS. 10 and 11, respectively, it can be seen that the crystal grains are extremely coarse. Next, when comparing the hardness, as shown in Table 1, the products of Example 1 and Comparative Example 1A, which employ the powder metallurgy method, are significantly superior, and among them, Example 1 is superior. There is. When we investigated the change in hardness at high temperatures, we found that as shown in Figure 12,
The product of Example 1 outperforms the products of Comparative Examples 1A, 1B and 1C. In addition, for comparison of wear resistance, the results were measured using an Okoshi type abrasion tester using SCM420 as the mating material, a friction distance of 400 m, and a final load of 6.3 kg.
As shown in FIG. 13, at any friction speed, the product of Example 1 had significantly less wear loss than the products of Comparative Examples 1A, 1B, and 1C. In addition, for comparison of corrosion resistance, the results of immersion in 50% hydrochloric acid at 50°C, 30% sulfuric acid at 50°C, and 10% nitric acid at 50°C to determine the corrosion weight loss are shown in Figure 14 a, b, and c, respectively. Shown below. These results show that under any conditions, the product of Example 1 is superior to Comparative Examples 1A, 1B and
Compared to the 1C product, there was less weight loss due to corrosion.
Furthermore, the results of a Charpy impact test to compare brittleness showed that the product of Example 1 had superior values compared to the products of Comparative Examples 1A, 1B, and 1C, as shown in Figure 15. When the hardness of the material is also considered, it can be seen that the value of Example 1 is extremely high. Note that the symbols in Fig. 15 are as follows:
Indicates the number of the example or comparative example. Example 2 and Comparative Example Capsules and cores having the structure shown in Figure 6 were used, and the inside was filled with gas atomized powder (average particle size: 150 μm) of the alloy shown in Table 2. The specifications of the capsule are as follows. Total length: 690mm Outer cylinder: External diameter: 207.5mm, Inner diameter: 180mm, Material: SUS304 Core: Diameter: 74mm x 2, Material: SUS304 Powder filling rate: 63% The above capsule was heated to 800℃ in an atmospheric furnace without cold isostatic pressing. And this
The mixture was heated by induction to 1180°C and loaded into a hot extruder having a cylinder with an inner diameter of 215 mm for extrusion processing.
The dimensions of the extruded product are as follows. Outer cylinder: outer diameter 115 mm, inner diameter 90 mm, length 2.5 m Core: diameter 48 mm x 2 As shown in Table 2, Comparative Examples 2A, 2B, and 2C were manufactured using alloys with virtually the same composition as Example 2. . The manufacturing method of Comparative Example 2A is the same as Comparative Example 1A, and
2B is a cast material, and Comparative Example 2C is a thermal sprayed material.

[Table] As shown in Table 2, the product of Example 2 had the best hardness. In addition, as shown in Fig. 15, the product of Example 2 is superior to the products of Comparative Examples 2A, 2B, and 2C in terms of the Shapey impact value, which indicates brittleness. It turns out that the value is great. Furthermore, the findings in the micrograph (400x) show that the first
As shown in Figure 6, the metal part originating from the capsule 17 (upper part) and the sintered alloy part originating from the powder 18 (lower part) are completely diffusion bonded between the metals, resulting in excellent bonding strength. It was found that it had. Example 3 and Comparative Example Using a capsule having the structure shown in the first diagram,
The interior was filled with gas atomized powder (average particle size 150μ) of an alloy having the composition shown in Table 3. The specifications of the capsule are as follows. Total length: 400 mm, outer diameter: 149 mm, inner diameter: 147 mm Material: S20C Powder filling rate: 65% The results of compressing the above capsule using a cold isostatic press are as follows. Total length 398mm, outer diameter 149mm, inner diameter 145mm Powder filling rate 68% After heating this to 800℃ in an atmospheric furnace, it was heated to 1180℃.
The alloy rod was induction heated and loaded into a hot extruder having a cylinder with an inner diameter of 160 mm to obtain an alloy rod with an outer diameter of 35 mm and a length of 7.2 m including a metal coating on the surface. For comparison, as shown in Table 3, Example 3
Comparative Example 3A was prepared using an alloy having virtually the same composition as that of Comparative Example 3A.
The preparation method is the same as Comparative Example 1A.

[Table] As is clear from Table 3 and Figure 15, the product of Example 3 is superior in hardness, and the product of Example 3 is slightly superior in brittleness. The product of Example 3 is significantly superior. Example 4 and Comparative Example Using a capsule having the structure shown in the first diagram,
The interior was filled with gas atomized powder (average particle size 150μ) of an alloy having the composition shown in Table 4. The specifications of the capsule are as follows. Total length: 400 mm, outer diameter: 151 mm, inner diameter: 147 mm Material: S20C Powder filling rate: 65% The results of compressing the above capsule using a cold isostatic press are as follows. Total length 398mm, outer diameter 149mm, inner diameter 145mm Powder filling rate 69% This was heated to 800℃ in an atmosphere furnace, then heated to 1080℃ in an induction furnace, and processed using a hot extruder with a cylinder with an inner diameter of 160mm. An alloy rod with an outer diameter of 60 mm and a length of 2.5 m was obtained. For comparison, as shown in Table 4, Example 4
Comparative Example 4A was prepared using an alloy having virtually the same composition as that of Comparative Example 4A.
The preparation method is the same as Comparative Example 1A.

[Table] As is clear from Table 4 and Figure 15, the product of Example 4 is superior in hardness, and the product of Example 4 is slightly superior in brittleness. The product of Example 4 is much better. Example 5 Using a capsule having the structure shown in the fourth diagram,
The interior was filled with gas atomized powder (average particle size 150μ) of an alloy having the composition shown in Table 5. The specifications of this capsule are as follows. Total length: 400 mm Outer cylinder: Outer diameter: 151 mm, inner diameter: 147 mm, material: S20C Inner cylinder: Outer diameter: 85 mm, inner diameter: 35 mm, material: SUS329J1 Powder filling rate: 65% The results of compressing the above capsule using cold isostatic press are as follows. Total length 400mm Outer cylinder 149mm outer diameter, 145mm inner diameter Inner cylinder 85mm outer diameter, 35mm inner diameter Powder filling rate 67% After heating this to 800℃ in an atmospheric furnace, it was heated to 1180℃.
The product was heated by induction and processed in a hot extruder having a cylinder with an inner diameter of 160 mm to obtain a product with the following dimensions. Outer diameter: 48 mm, boundary diameter: 38 mm, inner diameter: 30 mm, length: 6.0 m As is clear from Table 5 and Figure 15, its hardness is extremely high and its toughness is also excellent. Example 6 Using a capsule having the structure shown in Figure 5,
The interior was filled with gas atomized powder (average particle size 150μ) of an alloy having the composition shown in Table 5. The specifications of this capsule are as follows. Total length 500mm Outer cylinder Outer diameter 207.5mm, inner diameter 140mm, material SUS304 Inner cylinder Outer diameter 94mm, inner diameter 90mm, material S20C Powder filling rate 65% When the above capsule is compressed using a cold isostatic press, it becomes as follows. Total length 500mm Outer cylinder 207.5mm outer diameter, 140mm inner diameter Inner cylinder 96mm outer diameter, 92mm inner diameter Powder filling rate 68% This was heated to 800℃ in an atmosphere furnace and then heated to 1180℃.
by induction heating and processed in a hot extruder having a cylinder with an internal diameter of 215 mm to the following dimensions: Outer diameter 148mm, border diameter 108mm, inner diameter 96mm, length 2.5
m As shown in Table 5 and FIG. 15, extremely high hardness is obtained. Example 7 A capsule having the structure shown in FIG. 4 was used, and the inside was filled with gas atomized powder of an alloy having the composition shown in Table 5 (average particle size: 150 μm). The specifications of this capsule are as follows. Total length: 400mm Outer cylinder: Outer diameter: 151mm, inner diameter: 147mm, material: S20C Inner cylinder: Outer diameter: 73mm, inner diameter: 40mm, material: SUS304 Powder filling rate: 65% When the above capsule is compressed using a cold isostatic press, it becomes as follows. Total length 400mm Outer cylinder 149mm outer diameter, 145mm inner diameter Inner cylinder 73mm outer diameter, 40mm inner diameter Powder filling rate 69% After heating this to 800℃ in an atmospheric furnace, it was heated to 1180℃.
It is heated by induction and processed in a hot extruder having a cylinder with an internal diameter of 160 mm to the following dimensions: Outer diameter: 60 mm, boundary diameter: 40 mm, inner diameter: 30 mm, length: 3.0 m. As shown in Table 5 and Figure 15, extremely high hardness was obtained, and the brittleness was also at a level suitable for practical use.

[Table] <Effects of the Invention> As described above, in the prior art, high carbon, cobalt-based alloys cannot be hot plastic worked and can only be used by casting or welding methods. According to this invention, plastic working by hot extrusion becomes possible, and various properties of the alloy are also improved. Therefore, not only can long thin rods and long tubes of high carbon and cobalt-based alloys, which were previously unavailable, be obtained, but also clad materials with various ferrous and non-ferrous alloys can be produced economically. be able to. In particular, cylinders for plastic extruders and injection molding machines that require corrosion and wear resistance, as shown in Figure 7, have an inner periphery made of high carbon, cobalt-based alloy, and an outer periphery made of rust-free steel. Products made from hardened cladding materials have an extremely long life and can be manufactured economically.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view and a cross-sectional view of a first example of a capsule used in the present invention, FIG. 2 is a vertical cross-sectional view and a cross-sectional view of a second example of a capsule, and FIG. FIG. 4 is a vertical cross-sectional view and a cross-sectional view of the fourth example of the capsule;
FIG. 5 is a vertical cross-sectional view and a cross-sectional view of a fifth example of a capsule, FIG. 6 is a vertical cross-sectional view and a cross-sectional view of a sixth example of a capsule, and FIG. A cross-sectional view of the product according to this invention, FIG. 8 is a 3000 times enlarged structure diagram of the sintered alloy part according to the first embodiment,
Figure 9 is a 3000 times enlarged microstructure diagram of the comparative example alloy.
Figure 10 shows the metal structure of another comparative example alloy 400
Fig. 11 is a 400x micrograph showing the metal structure of another comparative example alloy, Fig. 12 is a temperature-hardness characteristic line of the sintered alloy according to the first embodiment of the present invention and the comparative example. Fig. 13 is a wear characteristic curve of the sintered alloy according to the first embodiment of the present invention and a comparative example, and Fig. 14 is a corrosion characteristic curve of the sintered alloy according to the first embodiment of the present invention and a comparative example. Figure 15 is a hardness-impact value characteristic diagram of the sintered alloys of each example and each comparative example, and Figure 16 is the boundary between the metal of the cladding material and the sintered alloy according to the second embodiment of the present invention. This is a 400x micrograph showing the structure of the cell.

Claims (1)

[Claims] 1. Powder a high carbon, cobalt-based alloy made up of 0.5 to 5.0% by weight of carbon and 40% by weight or more of cobalt and adding appropriate components to it, encapsulate this powder in a metal capsule, and then heat it. A method for producing a high-carbon, cobalt-based alloy member, which comprises pre-sintering the powder in the capsule, followed by induction heating to an extrusion temperature and plastic working by hot extrusion.