JP2001107166A - Alloy for joining cemented carbide and its composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an alloy for joining free from the generation of an embrittled phase on the joint boundary when joined with a WC-(Co, Ni) series cemented carbide, also low in residual stress generated on the joint part and good in fracture roughness and to provide a composite material thereof. SOLUTION: This alloy contains, as alloy components, by mass, 0.6 to <2.0% C, 9.3 to <15.5% W, and the balance one or two kinds of Co and Ni with inevitable impurities. The alloy may contain <=30% Fe, <=3% Si and <=3% Mn. Moreover, the same may contain one or two kinds or more among Cr, Mo, V, Nb, Ti, Zr and Ta by <=10%. By using this alloy as an alloy for joining, a composite material of a cemented carbide with the alloy for joining and a cemented carbide-steel composite material having excellent mechanical properties can be obtained.

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 flexible binder phase, have excellent hardness and wear resistance, and are used for plastic working of cutting tools, rolls, punches, etc. It is useful as a tool and 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. In addition, in the brazing material, because of the internal stress based on the difference in the coefficient of thermal expansion between the brazing material, the cemented carbide and the base material,
The brazing material or cemented carbide may crack. 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. Similarly, in the case of joining a WC-Ni-based cemented carbide and steel, it is difficult to obtain a sound joint by diffusion joining.

In order to solve the above-mentioned problems, the present inventor has previously described Japanese Patent Application Nos. 10-3969 and 11-11.
No. 100075 proposed an alloy for cemented carbide and its composite material. According to the proposal, WC-Co cemented carbide,
Even when joined with a WC-Ni cemented carbide, it does not form an embrittlement phase at the joint, guarantees excellent joining strength, and has ductility that can withstand plastic working such as hot forging. Therefore, it is possible to provide an inexpensive joining alloy having a high degree of freedom.

[0006] The joining alloy portion of the composite material according to the proposal is:
Known machining, heat treatment, electric discharge machining, and welding can be performed, and the utility of the cemented carbide member is increased. 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 cemented carbide-steel composite having excellent joining strength.

[0007]

However, when the proposed alloy is joined to a WC-Co cemented carbide, a WC-Ni cemented carbide, or the like, the formation of an embrittlement phase such as an η phase at the joint portion. Thus, although fracture strength can be prevented, the fracture strength is high, but there is a problem that the fracture toughness is low due to the generation of residual stress due to the difference in thermal expansion.

[0008] Therefore, an object of the present invention is to provide a WC-Co cemented carbide and a WC-Ni cemented carbide without causing an embrittlement phase at the joint interface and remaining at the joint. An object of the present invention is to provide a joining alloy having a lower stress and a higher fracture toughness than conventional alloys. In addition, a highly reliable composite of a joining alloy and a cemented carbide, or an inexpensive and highly reliable cemented carbide having excellent strength and function—a joining alloy—
It is to provide a cemented carbide alloy of steel.

[0009]

Means for Solving the Problems To solve the above problems, the cemented carbide alloy of the present invention comprises: (1) As an alloying component, C: 0.6% by mass or more and less than 2.0% by mass; W: contains 9.3% by mass or more and less than 15.5% by mass, and is characterized by being composed of one or more of Co and Ni and the inevitable impurities. (2) As alloy components, C: 0.6% by mass or more and less than 2.0% by mass, W: 9.3% by mass or more and less than 15.5% by mass,
Fe: not more than 30% by mass, and the balance consists of one or two of Co and Ni and unavoidable impurities. (3) In the cemented carbide alloy according to any one of the above (1) or (2), in addition to the above alloy components, any of Si: 3% by mass or less and Mn: 3% by mass or less. Or one or two of them. (4) In the cemented carbide according to any one of (1) to (3), in addition to the above alloy components, further, among Cr, Mo, V, Nb, Ti, Zr, and Ta, It is characterized by containing 10% by mass or less of any one type or two or more types.

Further, the composite material of the present invention is: (5) In a composite material in which a cemented carbide and a joining alloy are joined to form an integral structure, the joining alloy is one of the above (1) to (1).
(4) The alloy for cemented carbide according to any one of (4). (6) In a cemented carbide and a joining alloy, and in a composite material in which the joining alloy and steel are joined to form an integral structure, the joining alloy is any one of (1) to (4). Characterized in that it is an alloy for cemented carbide.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, it is essential to prevent the occurrence of an η phase at a joint interface in order to obtain a highly reliable joint when cemented carbide and another metal are joined. In addition to the knowledge, it has been made based on the knowledge that it is necessary to reduce the residual stress generated at the joint in order to secure mechanical stability and reliability after joining.

The alloy for cemented carbide according to the present invention has an alloy composition that suppresses a change in the chemical composition of the binder phase γ in the cemented carbide to be joined during the diffusion reaction at the joining temperature. The alloy composition is selected to reduce Young's modulus and increase toughness. Thereby, the residual stress caused by the difference in the coefficient of thermal expansion between the joining alloy and the cemented carbide can be kept low, and the reliability of the mechanical properties is improved. Furthermore, since the joining alloy is relatively rich in ductility, cold plastic working such as cold drawing can be performed.

According to the present invention, a hard metal mainly containing WC as a hard particle, which is bound by a bonding phase composed of Co, Ni or an alloy thereof, does not contain an η phase or free carbon which embrittles the alloy. It is necessary to strictly control the content of each constituent element including C in order to obtain a sound structure, and furthermore, the finding that Fe is effective in improving the hot workability of the alloy. based on.

That is, a sound cemented carbide consists 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 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.

[0016] The cemented carbide alloy of the present invention has a chemical composition adjusted so as to minimize the change in the C and Co or Ni contents at the joint interface during joining.
The cemented carbide targeted by the present invention mainly contains W as hard particles.
C, but a part of the WC is Cr, Mo,
Nb, Ti, Zr and Ta carbides or nitrides 1
It may be substituted with more than one species. 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 cemented carbide for use in 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, as alloy components, C: 0.6% by mass or more and less than 2.0% by mass, W: 9.3% by mass or more and less than 15.5% by mass, and the balance of one or more of Co and Ni.
It consisted of species and inevitable impurities. C and W
Is about 1: 15.3 to 1 as an equivalent of WC.
Preferably, it is 6.5. The content as WC is preferably set to 10 to 15% by mass.

Fe can be added to the joining alloy of the present invention in order to increase the strength of the alloy and improve the hot 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 increases the Young's modulus of the alloy and lowers the toughness and ductility of the composite. Therefore, in the alloy of the present invention, the upper limit of the Fe content is 30 mass%. %.

The cemented carbide alloy of the present invention comprises a cast product,
It is offered as hot-worked and cold-worked products as well as 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. Any one or two of Si: 3% by mass or less and Mn: 3% by mass or less can be added in order to exhibit the above effects without impairing the spirit of the present invention.

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 alloy for cemented cemented carbide 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 hot working such as hot forging or hot extrusion. And it is subjected to cold working such as cold rolling and cold drawing to be supplied in a required shape. It is also supplied as powder produced by atomization or mechanical pulverization and a sintered body of the powder. In addition, it is also supplied as a compact made of a mixed powder of Fe, Co, Ni, W, C and the like, or as a sintered body of the mixed powder. Further, as a method of forming the bonding intermediate layer,
Plating, sputtering, and vapor deposition can be used.

The joining alloy of the present invention is subjected to processing such as hot working, cold working, cutting, or the like as required to obtain a required shape, and then the joining alloy and the cemented carbide are joined to each other. The surfaces are placed in contact with each other, and pressure is applied
The composite material of the cemented carbide and the joining alloy can be obtained by performing diffusion bonding by heating at a temperature of 00 to 1300 ° C. or by applying pressure after heating. Further, a cemented carbide, a joining alloy of the present invention, and steel are laminated and assembled in this order, and then pressurized and heated in the same manner as described above to obtain a composite material in which the cemented carbide and steel are connected.

Instead of the above uniaxial pressing and heating, a laminated assembly of a cemented carbide and the joining alloy of the present invention, or a cemented carbide,
A stronger composite material can be obtained by inserting and sealing the laminated assembly of the joining alloy and steel of the present invention into a capsule and subjecting the assembly to high-temperature hydrostatic pressure treatment by a HIP device. Further, the cemented carbide and the joining alloy of the present invention are joined by the above-described method, and then the joining alloy and steel are joined by a known joining method such as welding, pressure welding, or diffusion joining to form a composite material. You can also.

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]

6 m in diameter from the (diameter D) / 4 part of the ingot
m, cut out a 110 mm long hot tensile test piece,
It was subjected to a hot tensile test. The hot tensile test was performed by gripping a test piece at a grip interval of 90 mm and at 1150 ° C. at a tensile speed of 50 mm / sec. The elongation to break was calculated by measuring the distance between the grips at the time of break, and is shown in Table 2 as hot elongation.

[0029]

[Table 2]

The ingot (outer diameter after shaving: 78 mm) was heated to 1200 ° C. and forged into a round bar having a diameter of 45 mm by 10 heats. As a result, in the example, the forging could be performed to the target size by the strong working without any trouble or by adding the hot scratching process. 8 on the round bar
After heating at 50 ° C. × 1 hr, annealing was performed at 15 ° C./hr in a furnace to obtain a 45φ annealing material. Furthermore, it is forged into a round bar with an outer diameter of 10 mm by spring forging, and 850 ° C x 1 hr.
After the heating, annealing was performed at 15 ° C./hr in a furnace to obtain a 10φ annealing material.

The annealed material is cold drawn at a reduction ratio of 5% or less per one step, and the total reduction ratio at which cold drawing can be performed without any trouble is determined. did. The results are shown in Table 2 as a cold drawing rate.

A sample having a diameter of 10 mm and a length of 60 mm was cut out from the D / 4 part of the 45φ annealed material, and the parallel part 2 was cut out.
Tensile test specimens having a length of 0 mm and a gauge length of 10 mm were produced and subjected to a tensile test at room temperature to examine Young's modulus and tensile strength characteristics. The results are shown in Table 3 as room temperature tensile test results of the forged annealed material. The diameter of the ingot is 1
A tensile test piece similar to the above was produced from the / 4 portion, and the result of a tensile test at room temperature is shown in Table 3 as a tensile test result of the cast material.

[0033]

[Table 3]

From the ingot, a diameter of 20 mm and a length of 15 mm
Was cut out. In addition, a WC-13 mass% Co cemented carbide round bar having a diameter of 20 mm and a length of 15 mm was prepared. After inserting the joined alloy round bar and the WC-13 mass% Co cemented carbide round bar into a mild steel capsule with their end faces in contact with each other, degassing and sealing, the temperature is set to 1100 ° C. and pressure by a HIP device. 117.7MPa (1200kgf
/ Cm ² ) and a hot isostatic pressure treatment for a retention time of 3 hours. 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 bending 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, the distance between the fulcrums was set to 20 mm, and the thickness of the joint was measured. A three-point bending test was performed by applying a concentrated load in the vertical direction. Table 4 shows the results.

[0036]

[Table 4]

From the forged material of Example 1 shown in Table 1,
A 3 mm thick alloy alloy disc 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 JIS SK having a diameter of 12 mm and a length of 50 mm are used.
A steel round bar equivalent to D11 was prepared. A cemented carbide round bar, a joining alloy disk, and a steel round bar are laminated in this order, and each end face is closely assembled and assembled. The assembled body is inserted into a mild steel capsule, decompressed and sealed, and heated to 1100 ° C. by a HIP device. Pressure 117.7
A hot isostatic pressure treatment was performed at a pressure of 1200 kgf / cm ^{2 for 3} hours. 8 diameter by turning and grinding
A bending test piece of mm × 100 mm in length was obtained. It was recognized that all the joints of the bending test pieces were tightly joined to form a sound composite material. The flexural test piece was subjected to a three-point bending test by applying a concentrated load to the joint portion while setting the distance between fulcrums to 80 mm. Table 4 shows the results.

As is clear from the above experimental results, the cemented carbide alloy of the present invention has excellent hot workability and cold workability, a low Young's modulus, The composite material and the composite material of the cemented carbide and the steel joined using the present bonding alloy show practically sufficient bonding strength.

[0039]

As described above, the cemented carbide alloy of the present invention is excellent in hot workability and cold workability, so that it can be easily formed into a required shape as a joint alloy.
Further, the cemented carbide for cemented carbide of the present invention does not generate an embrittlement phase at the joint even when joined with a WC-Co-based cemented carbide or a WC-Ni-based cemented carbide, and has a low Young's modulus. Therefore, since the residual stress generated in the joint is low, 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 the 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.

Claims (6)

[Claims] 1. An alloying component containing C: 0.6% by mass or more and less than 2.0% by mass, W: 9.3% by mass or more and less than 15.5% by mass, and the balance of any one of Co and Ni Or an alloy for joining cemented carbide, comprising two or more unavoidable impurities. 2. The alloy composition contains C: 0.6% by mass or more and less than 2.0% by mass, W: 9.3% by mass or more and less than 15.5% by mass, and Fe: 30% by mass or less, with the balance being the balance. An alloy for cemented carbide joining, comprising one or two of Co and Ni and unavoidable impurities. 3. In addition to the above alloy components, Si:
The cemented carbide according to claim 1, further comprising one or more of 3% by mass or less and Mn: 3% by mass or less. 4. In addition to the above alloy components, Cr,
The alloy for cemented cemented carbide according to any one of claims 1 to 3, wherein one or more of Mo, V, Nb, Ti, Zr, and Ta are contained in an amount of 10 mass% or less. . 5. A composite material in which a cemented carbide and a joining alloy are joined to form an integral structure, wherein the joining alloy is the cemented carbide joining alloy according to any one of claims 1 to 4. A composite material characterized in that: 6. A cemented carbide and a joining alloy, and a composite material in which the joining alloy and steel are joined to form an integrated structure, wherein the joining alloy is any one of claims 1 to 4. A composite material characterized by being a cemented carbide alloy.