JPH0277536A - Production of high-carbon cobalt-base alloy member - Google Patents

Abstract

PURPOSE:To produce the title alloy member by sealing a powder of high-carbon cobalt-base alloy containing specific percentages of C and Co in a metallic capsule and subjecting the above to presintering and then to plastic working by means of hot extrusion method. CONSTITUTION:A high-carbon cobalt-base alloy having a composition which contains, by weight, 0.5-5.0% C and >=40% Co as principal components and in which proper components, such as Cr, Ni, W, Mo, V, Nb, Ti, and Fe, are added to the above components is pulverized to <= about 1000mu by an atomizing method. A cylindrical metallic capsule 1 made of soft steel, rustless steel, etc., is filled with the resulting alloy powder 2, evacuated and sealed, subjected to cold isostatic pressing to increase filling density to about 65-70%, and then preheated up to >= about 700 deg.C by means of induction heating. When the temp. of the powdery raw material 2 reaches about 1150-1200 deg.C by means of further induction heating, glass lubricant is allowed to adhere rapidly to the whole surface and the above powdered raw material 2 is charged into a hot extruding machine to undergo plastic working, and the metallic layer is removed by means of grinding, etc., by which the desired alloy member can be obtained.

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 in particular, a method of molding a member of a desired shape from the above alloy using powder metallurgy technology. Regarding how to.

<Conventional technology> Based on 15 to 5.0% by weight of CO and 40% by weight or more of Go, which is combined with Cr, Ni, W, Mo, V, N
High-carbon, cobalt-based alloys made by appropriately adding various components such as B, Ti, and Fe are attracting attention as materials for harsh 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> Generally, manufacturing methods such as welding or 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. In particular, in high carbon and cobalt-based alloys, eutectic carbides coarsely agglomerate during solidification and are unevenly dispersed in the matrix, making it impossible to fully utilize the properties of the metal. Since internal defects such as holes are likely to be present, 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 μl or less or relatively long pipes with a length of 1 m or more, and the work efficiency is low, and the casting method There are severe restrictions on the form of the product, such as being able to only manufacture thin-walled tubes.

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, and then this alloy powder is encapsulated in a metal capsule. The capsule is filled 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,
Components such as Ni, W, Mo, V, Nb, Ti, and Fe are appropriately selected and added.

The method of powdering is to disperse carbide finely and uniformly,
In order to make the crystal grains of the matrix finer, an atomization method that involves rapid cooling is suitable, and in particular, a gas atomization method that produces spherical powder is most suitable in order to increase the filling rate within the capsule. Its particle size increases the filling rate within the capsule,
In order to facilitate heating, it is desirable to mix up to about 1000 g of each type.

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. product or high carbon,
In the case of a cladding material made of a cobalt-based alloy and an ordinary metal, a suitable thickness of the metal used to constitute the cladding material is used for a part of the capsule wall or 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, carbides and crystal grains will become coarse, so heating and extrusion must be carried out as quickly as possible.

In order to help raise the temperature of the raw powder, it is desirable to perform cold isostatic pressing after filling it into capsules.By doing this, the packing density of the powder can be increased from 60-65% to 65-65%.
70%, improving thermal conductivity for pre-sintering.

Induction heating is the best way to rapidly heat the raw powder in the capsule to the extrusion temperature. However, even if the packing density of the powder raw material is increased as described above, it is difficult for the induced current to flow through the powder raw material. Therefore, prior to induction heating, the capsules are
It is necessary to pre-sinter the powder inside by heating to 00°C or higher.

When the capsule reaches a predetermined temperature by induction heating, glass lubricant is immediately applied to the entire surface of the capsule, and the capsule is loaded into a hot extruder and processed.

<Function> The powdered raw material filled in 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 the induction heating quickly raises the processing temperature. Warm and undergo hot extrusion processing.

As a result of the extremely rapid process from temperature rise to hot extrusion processing, 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, which were conventionally considered impossible to be processed by plastic processing.

<Example> As shown in Fig. 1, when a cylindrical metal capsule l is filled with high carbon, cobalt-based alloy powder 2 and hot extruded, a thin metal layer originating from the capsule l 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. You can get an alloy tube covered with. If necessary, remove the metal coating on the inner, outer, or both surfaces before use.

As shown in FIG. 3, when a cylindrical metal cuboid having a core 6 made of a suitable metal is filled with 1 alloy powder 8 and hot extruded, the outer surface is covered with a thin metal layer. You can get a cluttered bar.

Although the outer metal coating is removed, it is reinforced by the inner metal core to provide high mechanical strength.

As shown in FIG. 4, an alloy powder 1
1 and hot extrusion process, a clad tube whose outer surface is covered with a thin metal layer is obtained. High mechanical strength can be obtained by removing the metal coating on the outer surface or by reinforcing it with a metal layer originating from the inner cylinder IO.

As shown in FIG. 5, a thick outer cylinder 12 and a thin inner cylinder 13
When an alloy powder 14 is filled between the inner and outer cylinders of a double cylindrical metal capsule and hot extruded, a clad tube with a thin metal layer adhered to the inner surface is obtained. High mechanical strength can be obtained by removing the metal coating on the inner surface or by reinforcing it with a metal layer originating from the outer cylinder 12.

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 core originating from the core 15, 16 of the extrusion is removed by machining and the resulting hole surface is finished, a pot-shaped hole 20 is formed in the alloy part 19 as shown in FIG. However, it is possible to obtain an envelope for a twin-shaft extruder whose outer side is surrounded by a reinforced metal cylinder 21.

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 A capsule having the structure shown in the fourth figure is used.

Inside is a gas atomized powder of an alloy with the composition shown in Table 1 (
The average particle size was 1504). The specifications of the capsule are as follows.

Total length: 400m Outer cylinder: outer diameter 151m5, inner diameter 147mm, material 32
0C inner cylinder outer diameter 74m, inner diameter 40u, material STB^
24 Powder filling rate 62% The results of compressing the above capsule by cold isostatic press are as follows.

Total length 400-layer outer cylinder outer diameter 149μl, inner diameter 145m5 inner cylinder outer diameter 74
■Powder filling rate: 65% This was heated in an atmospheric furnace to 800℃, then induction heated to 1180℃, loaded into a hot extruder with a cylinder with an internal diameter of 160s, and extruded. Ta. The dimensions of the product, including the metal coating on the surface, are as follows.

Outer diameter: 58cm, border diameter: 42cm, inner diameter: 36cm.

Length: 3.7 m As shown in Table 1, Comparative Examples IA, IB and IC were manufactured from alloys having virtually the same composition as Example 1. Comparative example 1^
11 gas atomized alloy powder with an average particle size of 150μ
Molding was performed by hot pressing at 50° C. and 1000 Kg/c 2, Comparative Example 1B is a cast material, and Comparative Example IC is a thermally sprayed material.

Table 1 In the sintered alloy part of the product of Example 1, as shown in FIG. 8, carbide and matrix crystal grains did not grow much. On the other hand, in the case of the product of Comparative Example IA, even though the same raw material powder was sintered, carbides and matrix crystal grains grew long and thin, as shown in FIG. Furthermore, in the case of the products of Comparative Examples IB and Ic, the first
As shown in Figure O and Figure 11, it can be seen that the crystal grains are extremely coarse.

Next, when we compare their hardness, as shown in Table 1, the products of Example 1 and Comparative Example IA, 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 the 12th
As shown in the figure, the product of Example 1 is superior to the products of Comparative Examples IA, IB, and IC.

In addition, for comparison of wear resistance, an Okoshi type abrasion tester was used, SCM420 was used as the mating material, and a friction distance of 40
As shown in Figure 13, the results of measurements at layer 0 and final load of 6.3 g show that the product of Example 1 was significantly better than the products of Comparative Examples IA, 1B, and IC at any friction speed. Wear loss was less.

#For comparison of eating habits, 50% hydrochloric acid at 50°C,
Figure 14 (a) shows the results of immersion in 30% sulfuric acid at 50°C and 10% nitric acid at 50°C to determine the corrosion loss.
, (b) and (C), the results show that under any conditions, the product of Example 1 was superior to Comparative Examples IA, IB, and I.
Compared to product C, the weight loss due to corrosion was less.

Furthermore, as shown in Figure 15, 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 IA, IB, and IC. When considering the hardness of the material, it can be seen that the value of Example 1 is extremely high. In addition,
The symbols in FIG. 15 indicate the numbers of Examples or Comparative Examples.

Example 2 and Comparative Examples Capsules and cores having the structure shown in Figure 6 were used,
The inside was filled with gas atomized powder (average particle size: 150tz) of the alloy shown in Table 2. The specifications of the capsule are as follows.

Total length 690 layers 1 Outer cylinder outer diameter 207.5Bm, inner diameter 180■■, material S
O3:104 Core diameter 7411111X 2 pieces, material 5US304
Powder filling rate 63% The above capsule was heated as it was to 800°C in an atmospheric furnace without cold isostatic pressing, then induction heated to 1180°C, and loaded into a hot extruder having a cylinder with an inner diameter of 215mm. Then, extrusion processing was performed.

The dimensions of the extruded product are as follows.

Outer cylinder: Outer diameter: 5 mm, inner diameter: 90 sn, length: 2.5 m Core: diameter: 48 s + sx, 2 As shown in Table 2, alloys with the same composition as Example 2 and Fact 1, Comparative Examples 2A, 2B and 2C was manufactured. Comparative example 2A
The manufacturing method is the same as that of Comparative Example 1A, and Comparative Example 2B is a cast material, and Comparative Example 2C is a thermal sprayed material.

Table 2 As shown in Table 2, the product of Example 2 had the best hardness. Furthermore, as shown in Figure 15, the Charpy impact value, which indicates brittleness, was the same for the products of Example 2 as for Comparative Examples 28, 2B, and
It is found that the product of Example 2 is superior to the product of C, and if hardness is considered, the value of Example 2 is greater than that of these comparative examples.

Furthermore, as shown in Figure 16, the WJ microphotograph (400x magnification) shows that the metal part originating from the capsule 17 (upper part) and the sintered alloy part originating from the powder 18 (lower part) are completely separated. It was found that diffusion bonding between metals was achieved and that the bonding strength was excellent.

Example 3 and comparative example A capsule having the structure shown in the first diagram is used.

Inside is a gas atomized powder of an alloy with the composition shown in Table 3 (
The average particle size was 150 p). The specifications of the capsule are as follows.

Total length 400mm, outer diameter 149mm, inner diameter 147+s
m Material: 5zoc Powder filling rate: 65% The above capsule was compressed by cold isostatic press, and the results are as follows.

The total length is 398mm, the outer diameter is 149 layers, the inner diameter is 145mm, and the powder filling rate is 68%. After heating this in an atmosphere furnace to 800℃,
: Heated by induction and loaded into a hot extruder with a cylinder with an inner diameter of 1601 mm, and the outer diameter including the metal coating on the surface was 35 g.
11. An alloy rod with a length of 7.2 m was obtained.

For comparison, Comparative Example 3A was prepared using an alloy having virtually the same composition as Example 3, as shown in Table 3.

The preparation method is the same as that of Comparative Example IA.

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 in Example 3 is much better.

Example 4 and Comparative Examples Capsules having the structure shown in Figure 1 were used, and gas atomized powder (average particle size tsog) of an alloy having the composition shown in Table 4 was filled inside. The specifications of the capsule are as follows.

Total length 400mm, outer diameter 151mm, inner diameter 147ff
i Footwear material: 5zoc Powder filling rate: 65% The above capsule was compressed by cold isostatic press, and the results are as follows.

Total length: 198mm, outer diameter 149mm, inner diameter 145m
m Powder filling rate: 69% After heating this to 800°C in an atmosphere furnace, it was heated to 1°C in an induction furnace.
It was heated to 080°C and processed by a hot extruder with a cylinder with an inner diameter of 160 m, and an outer diameter of 60 m and a length of 2
．． A 5 m alloy rod was obtained.

For comparison, Comparative Example 4A was prepared using an alloy having virtually the same composition as Example 4, as shown in Table 4. The preparation method is the same as that of Comparative Example IA.

As is clear from Table 4 and Figure 15, the product of Example 4 is superior in hardness and slightly superior in brittleness to the product of Example 4. The product of Example 4 is much better.

Example 5 A capsule having the structure shown in Figure 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: 150p). The specifications of this capsule are as follows.

Total length 4 (10 lengths) Outer cylinder outer diameter 151m5, inner diameter 147mm, material 820C
Inner cylinder outer diameter 8511111, inner diameter 351, material 5US3
29 Jl Powder filling rate 65% The results of compression using the capsule cold isostatic press described above are as follows.

Total length: 400 m Outer cylinder outer diameter 149 l, inner diameter 145 m5 Inner cylinder outer diameter 85
Proverb: Inner diameter 35mm Powder filling rate 67% After heating this to 800°C in an atmosphere furnace, 1180°C
The product was heated by induction to a temperature of 100 cm and processed in a hot extruder having a cylinder with an inner diameter of 160 mm to obtain a product with the following dimensions.

The outer diameter is 48 mm, the boundary diameter is 38 mm, the inner diameter is 30 mm, and the length is 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 A capsule having the structure shown in Figure 5 was used, and gas atomized powder of an alloy having the composition shown in Table 5 (average particle size: 150 mm) was filled inside. The specifications of this capsule are as follows.

Total length: 50 holes I-hoto outer cylinder, outer diameter 207.5mm, inner diameter 140mm, Saiga S
US304 Inner cylinder Outer diameter 94I, Inner diameter 90mm, Material 520C Powder filling rate 65% When compressed using the capsule cold isostatic press described above, it becomes 0 order.

Total length 5001 Outer cylinder outer diameter 207.5mm, inner diameter 140am Inner cylinder outer diameter 96cm, inner diameter 92cm Powder filling rate 68% After heating this to 800℃ in an atmosphere furnace, it was heated to 1180℃.
The sample is heated by induction and processed in a hot extruder having a cylinder with an inner diameter of 2151 mm to obtain the primary dimensions.

Outer diameter: 148 m5, boundary diameter: 108 m5, inner diameter: 96 mm, length: 2.5 m As shown in Table 5 and Figure 15, extremely high hardness can be 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: 150p). The specifications of this capsule are as follows.

Total length 400■ Outer cylinder outer diameter 151au+, inner diameter 147m5, material 320
G inner cylinder outer diameter 73+sm, inner diameter 40mm, material SO3:
104 Powder filling rate 65% When the above capsule is compressed by cold isostatic pressing, it becomes as follows.

Total length 400 Seiho outer cylinder outer diameter 149mm, inner diameter 14Svm inner cylinder outer diameter 73
■Peng, inner diameter 40■■ Powder filling rate 69% After heating this to 800°C in an atmosphere furnace, it was heated to 1180°C.
The sample was heated by induction and processed in a hot extruder having a cylinder with an inner diameter of 160 mm to the following dimensions.

Outer diameter 60cm, border diameter 40cm, inner diameter 0cm, length 3.
0 m As shown in Table 5 and FIG. 15, extremely high hardness was obtained, and the brittleness also showed a value that was sufficient for practical use.

Table 5 <Effects of the Invention> As described above, in the prior art, high carbon, cobalt-based alloys cannot be subjected to hot plastic working and can only be used by casting or welding methods. According to this invention,
Plastic processing by hot extrusion became smooth and glossy, and various properties of the alloy were also improved. Therefore, it is not only possible to obtain small-diameter long rods and small-diameter long pipes made of high carbon and cobalt-based alloys, which were previously unobtainable, but also to economically produce steel and steel materials made from various ferrous and non-ferrous alloys. can be produced.

In particular, it is used as a cylinder for plastic extruders and injection molding machines that require corrosion and wear resistance as shown in Figure 7.
Products made of crat material with an inner periphery made of a high carbon, cobalt-based alloy and an outer periphery made of stainless steel have an extremely long life and can be manufactured economically.

[Brief explanation of the drawing]

FIG. 1 is an M 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 the fifth example of the capsule, FIG. 6 is a longitudinal and cross-sectional view of a sixth example of a capsule, FIG. 7 is a cross-sectional view of a product according to the invention using the capsule of FIG. 6, and FIG. 8 is a first embodiment of the product. Fig. 9 is a 3000 times enlarged structure diagram of the sintered alloy part, and FIG. 9 is a 3000 times enlarged structure diagram of the comparative example alloy. Fig. 1O is a 400x microphotograph showing the metallographic structure of another comparative example alloy, Fig. 11 is a 400x photomicrograph showing the metallographic structure of yet another comparative example alloy, and Fig. 12 is a photomicrograph showing the metallographic structure of another comparative example alloy. FIG. 13 is a temperature-hardness characteristic diagram of the sintered alloy according to the first embodiment of the present invention and a comparative example. FIG. 14u is a wear characteristic diagram of the sintered alloy according to the first embodiment of the present invention and the comparative example. Corrosion characteristic diagram of sintered alloy according to Example 1 and comparative example, 1st
Fig. 5 is a hardness-impact value characteristic diagram of the sintered alloys of each example and each comparative example, and Fig. 16 shows the structure of the boundary between the metal and sintered alloy of the crut material according to the second embodiment of the present invention. This is a 400x micrograph shown. Patent applicant Sanyo Special Steel Co., Ltd. Agent Tetsu Shimizu and 2 others
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Claims (1)

[Claims] (1) Powder a high carbon, cobalt-based alloy consisting essentially of 0.5 to 5.0% by weight of carbon and 40% by weight or more of cobalt with the addition of appropriate components, and encapsulate this powder in a metal capsule. A high-carbon, cobalt-based alloy member characterized in that the powder is heated to pre-sinter the powder in the capsule, and then induction heated to an extrusion temperature and plastic worked by hot extrusion. manufacturing method.