JP2000290757A - Alloy for joining cemented carbide and composite material thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the excellent joining strength with WC-Co or WC-Ni cemented carbide by allowing an alloy to contain C, W and Fe by respectively specified ratios, one or two kinds of Co and Ni by a specified ratio or above, and the balance inevitable impurities. SOLUTION: This alloy contains, by mass, 0.6 to 2.3% C, 9.3 to 34.7% W, >30 to 80% Fe and one or two kinds of Co and Ni by >=1.0%. Furthermore, it preferably contains Si and Mn by <=3%. A composite material in which cemented carbide and the alloy for joining are joined, or, furthermore, cemented carbide, the alloy for joining and steel are joined is obtd. As to the cemented carbide contg. WC as hard grains, and in which this is bonded with a bonding phase composed of Fe, Co, Ni and the alloys thereof, for obtaining a structure which does not contain a η phase or free carbon embrittling the alloy, the strict control of the content of each constituting element including C is needed. Furthermore, the incorporation of Fe has the effect of improving its hot workability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloy used as a cemented carbide useful as a wear-resistant tool or a cutting tool and a composite material thereof.

[0002]

2. Description of the Related Art Cemented carbides, in which hard particles such as carbides and nitrides are combined with a soft binder phase, have excellent hardness and wear resistance, and are used for plastic working tools such as cutting tools, rolls, and punches. It is also useful as a drilling tool for civil engineering and mining. However, hardmetals are difficult and expensive to process, and have low toughness and are easily broken. As a method to overcome this limitation, brazing and joining a base material such as steel, which is inexpensive and excellent in workability, to a cemented carbide,
It is used as a composite material by a mechanical fixing method such as screwing, shrink fitting, and clamping.

[0003] In the case of using a mechanical fixing method such as screwing, shrink-fitting, clamping, etc., it is necessary to perform processing for fixing hard metal which is difficult to process. It is inevitable that there will be restrictions on applications. Further, in the brazing material, cracks may occur in the brazing material or the cemented carbide due to internal stress based on the difference in thermal expansion coefficient between the brazing material, the cemented carbide and the base material. Further, since a material having a lower melting point than either the cemented carbide or the base material is used as the brazing material, there is a problem that the heat resistance is low and the strength of the entire composite material is reduced.

[0004] In order to avoid the above-mentioned problems caused by using the brazing material, it is conceivable that the cemented carbide and the base material are directly bonded by diffusion bonding. But in this case,
For example, when a WC-Co cemented carbide, which is the most typical cemented carbide, and a steel are diffusion-bonded, a thermal stress due to a large difference in thermal expansion is generated as in the case of the brazing, and a diffusion layer is formed. However, there is a problem that a sound joining portion cannot be obtained because a brittle phase is generated. Also in the case of joining a WC-Ni-based cemented carbide and steel, it is difficult to obtain a sound joint by diffusion bonding, as described above.

In order to solve the above-mentioned problem, the present inventor has previously described, as Japanese Patent Application No. 10-3969, mainly C:
A cemented carbide alloy containing 1.0 to 2.3% by mass, W15.5 to 34.7% by mass, and the balance being at least one of Co and Ni and a composite material thereof have been proposed.

According to the proposal, a WC-Co based cemented carbide,
It is possible to provide a joining alloy capable of guaranteeing excellent joining strength without generating an embrittlement phase in a joined portion even when joined with a WC-Ni-based cemented carbide. Further, by joining the joining alloy to the cemented carbide, a composite material having excellent joining strength can be provided. The joining alloy portion of this composite material is formed by known machining, heat treatment, electric discharge machining,
Welding is possible, increasing the usefulness of cemented carbide members.
Further, by joining the cemented carbide and the tough steel using the joining alloy as an intermediate layer, it is possible to provide an inexpensive and highly reliable cemented carbide-steel composite having excellent joining strength. it can.

However, since the proposed alloy has poor plastic workability and is difficult to hot work, it can only be supplied as a cast material or a powder sintered material, and the supply form is limited.

[0008]

The problem to be solved by the present invention is to provide a WC-Co based cemented carbide, WC-Ni
Excellent joining strength can be guaranteed even when joining with a series cemented carbide, and it has ductility that can withstand plastic working such as hot forging, so it has a large degree of freedom in supply form, and an inexpensive joining alloy can be used. To provide. In addition, a highly reliable composite of the joining alloy and the cemented carbide, or a cemented carbide of an inexpensive and highly reliable cemented carbide having excellent strength and function-the joining alloy-steel To provide materials.

[0009]

In order to solve the above-mentioned problems, the cemented carbide alloy according to the present invention comprises: (1) C: 0.6 to 2.3% by mass as an alloy component;
W: 9.3 to 34.7% by mass, Fe: More than 30% by mass and 80% by mass or less, containing 1.0% by mass or more of one or two of Co and Ni and the balance consisting of unavoidable impurities. It is characterized by the following. (2) In addition to the above alloy components, Si: 3% by mass
And Mn: 3% by mass or less. (3) In addition to the above-mentioned alloy component (1) or (2), further contains any one or more of Cr, Mo, V, Nb, Ti, Zr, and Ta in an amount of 10% by mass or less. It is characterized by.

Further, the composite material of the present invention is: (4) a composite material in which a cemented carbide and a joining alloy are joined to form an integral structure, wherein the joining alloy is as described in (1) to (1) above;
(3) The cemented carbide according to any one of (3). (5) In a cemented carbide and a joining alloy, and a composite material in which the joining alloy and steel are joined to form an integral structure, the joining alloy is any one of the above (1) to (3). It is the alloy for cemented carbide described.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention mainly uses W as hard particles.
In order to obtain a sound structure free of η phase or free carbon which makes the alloy embrittled in a cemented carbide containing C and a bonding phase composed of Fe, Co, Ni and their alloys, It is based on the finding that the strict control of the content of each constituent element, including the first, is necessary, and that the content of Fe is effective for improving the hot workability of the alloy.

That is, a sound cemented carbide is composed of hard particles and a highly ductile binder phase (γ) such as Co or Ni. When the hard particles are WC, the amount of bound carbon is 6.13% by mass. For example, in a WC-16% by mass Co-based cemented carbide, when the amount of bound carbon is 6.06 to 6.3% by mass, WC + is used.
γ is two phases. However, the amount of bound carbon is 6.06% by mass.
If it is less than η, an η phase is formed and the alloy is embrittled. On the other hand, if the amount of bonded carbon exceeds 6.3% by mass, free carbon is generated and the cemented carbide is also embrittled.

When a cemented carbide and another metal are joined together, at the joining temperature, the C potential of the metal joined to the cemented carbide (referred to as a joining metal) is changed to the bonding phase (γ) of the cemented carbide.
If it is lower than that of C, diffusion of C from the cemented carbide into the joining metal occurs, and the C content in the binder phase of the cemented carbide decreases.
As a result, an η phase is formed in the binder phase, and the bonding interface of the cemented carbide becomes brittle. Similarly, a decrease in the Co content in the binder phase of the cemented carbide also promotes the formation of the η phase. If the C potential of the joining metal is higher than that of cemented carbide,
Free carbon is generated at the joining interface of the cemented carbide, causing the joining interface to become brittle.

The present invention seeks to obtain a sound joint by minimizing a change in the content of C and Co or Ni at the joint interface during joining. Cemented carbides targeted by the present invention are mainly WC as hard particles.
Shall be included. Part of the WC is Cr, Mo, N
It may be substituted with one or more of carbides or nitrides of b, Ti, Zr and Ta. Also, the binder phase in the cemented carbide is mainly composed of one of Co and Ni and their alloys, and contains the hard particle constituent elements in the cemented carbide in an amount equilibrium therewith. .

Next, the reason why the chemical composition of the alloy for cemented carbide according to the present invention is limited will be described. The joining alloy of the present invention and the cemented carbide are joined by diffusion. At this time, if the bonding temperature is lower than 1000 ° C., bonding cannot be performed, or a long heating time and a large pressure are required for bonding, which is not preferable. On the other hand, when the temperature exceeds 1300 ° C., a liquid phase is formed in the cemented carbide, and the deformation of the alloy is increased, which is not preferable.

Therefore, the temperature at which diffusion bonding can be substantially performed is 10
Equilibrium with the binder phase in the cemented carbide at 00 to 1300 ° C. so that C is not deposited in the binder layer or η phase is not generated due to lack of the binder layer metal. The alloy contains C: 0.6 to 2.3 as an alloy component.
% By mass, W: 9.3 to 34.7% by mass, Fe: Over 30% by mass and 80 or less, and an alloy containing 1.0% by mass or more of one or two of Co and Ni.

If the C content is less than 0.6% by mass or the W content exceeds 34.7% by mass, an η phase is formed at the joint interface of the cemented carbide, and the joint is weakened. On the other hand, if the C content exceeds 2.3% by mass or the W content is less than 9.3% by mass, free carbon is generated at the joining interface of the cemented carbide to make the joint weak. It is preferable that the content ratio of C and W is approximately 1: 15.3 to 16.5 as an equivalent of WC. Further, the content as WC is preferably from 10 to 37% by mass.

Fe is added in order to increase the strength of the alloy and to improve the hot and cold workability. However, Fe is an element that strengthens the tendency of the η phase to form at the bonding interface of the cemented carbide, and if the Fe content exceeds 80% by mass, the bonding interface of the cemented carbide becomes brittle, so the upper limit of the Fe content is 80%. %. Co and Ni are added to suppress generation of the η phase by Fe. for that purpose,
It is necessary to contain 1.0% by mass or more of any one or two of Co and Ni.

Si and Mn are added for deoxidizing the molten alloy. The cemented carbide alloy of the present invention is a cast product,
It is offered as a hot-worked product and also as an alloy powder. In particular, the addition of Si and Mn is extremely effective in preventing a pouring nozzle from being clogged, which often occurs when an alloy powder is produced directly from a molten metal. In order to exhibit the above effects without impairing the spirit of the present invention, 3% by mass or less of Si and 3% by mass or less of Mn can be added.

Part of WC in the cemented carbide to be joined is C
When one or more of carbides or nitrides of r, Mo, V, Nb, Ti, Zr, and Ta are substituted, the joining alloy of the present invention is made of Cr, Mo, V, Nb, Ti, Zr. Any one or more of Ta and Ta may be contained in a total amount of 10% by mass or less. When these elements are contained in a large amount exceeding 10% by mass, the alloy becomes brittle and a sound joining cannot be performed. Therefore, the upper limit of the content is set to 10% by mass.

The cemented carbide alloy of the present invention is supplied as a cast slab melted and cast by a usual alloy melting method, and the cast slab is subjected to plastic working such as hot forging and hot extrusion. And supplied in the required shape. It is also supplied as powder produced by atomization or mechanical pulverization and a sintered body of the powder. Other, Fe, Co, N
The mixed powder of i, W, C, etc. is also supplied as a green compact or a sintered body of the mixed powder. Further, the bonding intermediate layer can be formed by plating, sputtering, or vapor deposition.

The joining alloy of the present invention is machined as required to obtain a required shape, and then the cemented carbide and the joining surface are arranged in contact with each other.
A composite material of a cemented carbide and a bonding alloy can be obtained by heating at a temperature of 000 to 1300 ° C. or by performing diffusion bonding by applying pressure after heating. Also, a composite material in which the cemented carbide and the steel are connected can be obtained by laminating and assembling the cemented carbide, the joining alloy, and the steel in this order, and pressing and heating in the same manner as described above.

Instead of the above uniaxial pressing and heating, a laminated assembly of a cemented carbide and a joining alloy of the present invention or a laminated assembly of a cemented carbide, a joining alloy of the present invention and steel is inserted into a capsule. -A stronger composite material can be obtained by sealing and performing high-temperature hydrostatic pressure treatment with a HIP device.

Further, the cemented carbide and the joining alloy of the present invention are joined by the above-mentioned method, and then the joining alloy and steel are joined by a known joining method such as welding, pressure welding, diffusion joining, etc. It can also be a material.

When the joining alloy of the present invention is supplied as a powder, a cemented carbide and a joining alloy, or a composite of a cemented carbide, a joining alloy and steel is obtained by performing the high-temperature hydrostatic pressure treatment described above. be able to. Further, during or after press forming of the cemented carbide powder, the cemented carbide powder compact is laminated on the cemented carbide powder compact to form a joint alloy powder compact of the present invention, and then sintered to form a cemented carbide-joint. Alloy composites can also be formed.

[0026]

EXAMPLE Each alloy shown in Table 1 was melted using an induction furnace.
It was a 5 kg ingot.

[0027]

[Table 1]

[0028] From a quarter of the diameter of the ingot to a diameter of 6 m
m, cut out a 110 mm long hot tensile test piece,
It was subjected to a hot tensile test. The hot tensile test was conducted at a grip interval of the test piece of 90 mm, a tensile speed of 50 mm / sec at 1150 ° C., the distance between the grips at the time of breaking was measured, and the elongation until breaking was calculated. It is shown as elongation. From this result, it can be seen that the hotter elongation is larger in the sample containing more Fe.

[0029]

[Table 2]

The ingot (average outer diameter mm) is 1
It was heated to 150 ° C. and forged by heat into a round bar having a diameter of 45 mm with 10 heats. Table 2 shows the results as forging results. In Comparative Examples 4 to 6, cracks occurred and forging was impossible (Comparative Example 4,
5) or Zack cracking occurred, making it impossible to remove flaws (Comparative Example 6), and none of them could be forged to the target dimensions. In Comparative Examples 1 to 3 containing Fe, the forgeability was slightly improved, but it was necessary to repeatedly remove flaws, and forging was extremely difficult. On the other hand, in the example, the forging could be performed to the target size by the strong working without any trouble.

A sample having a diameter of 10 mm and a length of 60 mm was cut out from the forged sample, and a tensile test piece having a parallel portion of 20 mm and a gauge length of 10 mm was manufactured and subjected to a tensile test at room temperature. Table 3 shows the results. Table 3 shows the results of producing a tensile test piece similar to the above from a quarter of the diameter of the ingot and conducting a tensile test at room temperature. According to Table 3, it is found that the proof stress and the tensile strength increase with an increase in the Fe content, and the ductility such as elongation and drawing also improves. Each of the examples has excellent 0.2% proof stress and tensile strength, and also has high values of elongation and drawing.

[0032]

[Table 3]

A round bar of a joining alloy having a diameter of 20 mm and a length of 15 mm was cut out from a sample and an ingot forged to a diameter of 25 mm. In addition, WC-13 with a diameter of 20 mm and a length of 15 mm
A mass% Co cemented carbide round bar was prepared. The joined alloy round bar and the WC-13 mass% Co cemented carbide round bar were inserted into a mild steel capsule with their end faces in contact with each other, degassed and sealed, and then heated at a temperature of 1150 ° C. and pressure by a HIP device. 12
A hot isostatic pressure treatment of 00 kgf / cm ² and a holding time of 3 hr was performed. By the hot isostatic pressure treatment, it was recognized that the joined alloy round bar and the WC-13 mass% Co cemented carbide round bar were tightly joined at the contact end face to form a sound composite material. .

From the composite material, a flexural test piece having a thickness of 3.0 mm, a width of 5.0 mm, and a length of 30 mm having a joint surface at the center of the length was prepared. A three-point bending test was performed by applying a concentrated load in the vertical direction. As a result, as shown in Table 4, in Examples 1 to 6, none of the joints broke at the joints, and also showed a strength with no practical problem in the transverse rupture strength, and a sound joint was performed. Showed that.

[0035]

[Table 4]

From the ingot and the forged material of Example 1 shown in Table 1, a joining alloy disk having a diameter of 12 mm and a thickness of 3 mm was cut out. Also, a WC-13 mass% Co cemented carbide round bar having a diameter of 12 mm and a length of 50 mm and a steel round bar having a diameter of 12 mm and a length of 50 mm corresponding to JIS SKD11 were prepared. A cemented carbide round bar, a bonding alloy disk, and a steel round bar are laminated in this order, and the respective end faces are closely assembled and assembled. The assembled body is inserted into a mild steel capsule, decompressed and sealed, and 1200 kgf / h by a HIP device.
A high-temperature hydrostatic pressure treatment of 1200 ° C. × 3 hr was performed in cm ² . By turning, a bending test piece having a diameter of 8 mm and a length of 100 mm was obtained. It was recognized that all the joints of the bending test pieces were tightly joined to form a sound composite material.

For the bending test piece, the distance between supporting points was 80.
mm, and a concentrated load was applied to the joint to perform a three-point bending test. The results showed that the bending test piece did not break at the joint and showed a breaking stress of 698 MPa or more, indicating that sound joining was performed.

As is clear from the above experimental results, the composite material of the cemented carbide and the cemented alloy and the composite material of the cemented carbide and the steel joined by using the cemented carbide alloy of the present invention are practical. Shows sufficient bonding strength.

[0039]

As described above, according to the present invention, even when joined with a WC-Co-based cemented carbide or a WC-Ni-based cemented carbide, an embrittlement phase is not generated at the joint. Excellent joining strength can be guaranteed, and a joining alloy excellent in hot workability and mechanical properties can be provided. Further, by joining the joining alloy with a cemented carbide,
A composite material having excellent joining strength and mechanical strength can be provided. The joining alloy portion of this composite material can be subjected to known hot plastic working, machining, heat treatment, electric discharge machining, and welding, thereby increasing the usefulness of the cemented carbide member. By joining a cemented carbide and tough steel using the joining alloy of the present invention as an intermediate layer, it is possible to provide an inexpensive and highly reliable cemented carbide-steel composite having excellent joining strength. it can.

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Claims (5)

[Claims] 1. As alloy components, C: 0.6 to 2.3% by mass, W: 9.3 to 34.7% by mass, Fe: 30% by mass.
Over 80% by mass, one of Co and Ni
An alloy for cemented cemented carbide, characterized in that the alloy contains at least 1.0% by mass of one or more kinds and the balance consists of unavoidable impurities. 2. In addition to the above alloy components, Si:
2. The cemented carbide according to claim 1, wherein the alloy contains 3% by mass or less and Mn: 3% by mass or less. 3. In addition to the above alloy components, Cr,
The alloy for cemented cemented carbide according to any one of claims 1 and 2, wherein one or more of Mo, V, Nb, Ti, Zr, and Ta are contained in an amount of 10 mass% or less. . 4. The cemented carbide according to claim 1, wherein the cemented carbide and the joining alloy are joined together to form an integral structure. A composite material comprising: 5. A cemented carbide and a joining alloy, and a composite material in which the joining alloy and steel are joined to form an integral structure, wherein the joining alloy is any one of claims 1 to 3. A composite material characterized in that it is a cemented carbide alloy of the above.