JPH0714544B2 - High hardness material joining type tool - Google Patents

Description

TECHNICAL FIELD The present invention relates to various press tools such as forging, forging, and drawing, and other wear-resistant tools.

(Prior Art) A joining-type tool in which dissimilar metals are joined realizes characteristics that cannot be obtained by a single metal by utilizing the characteristics of each metal.

By the way, in order to manufacture a joining type tool consisting of a support part using a steel material excellent in toughness and a working part having high hardness, when joining the steel material and the cemented carbide directly by the solid phase diffusion matching method, Fe-Ni-based alloys, Fe-Cr-W-based alloys, etc. have been used as insert metals to intervene between steel materials and cemented carbides in order to suppress the formation of intermetallic compounds at the interface. .

In addition, after joining, heat treatment (quenching, tempering, etc.) is performed in order to give the supporting portion (steel material) a required strength.

(Problems to be Solved by the Invention) However, although a steel material can obtain necessary strength by heat treatment, it is difficult to obtain required strength with insert metal. Therefore, the tool life is often short in applications where high cyclic compressive strength is required.

Therefore, it is desirable that the following conditions be satisfied in the production of a joining type tool made of a steel material and a cemented carbide by solid phase diffusion joining.

a. Strength of insert metal The insert metal must have strength equal to or higher than the two metals to be joined.

b. Suppression of intermetallic compounds Do not generate brittle intermetallic compounds at the joint interface between the insert metal and both metals to be joined.

c. Heat treatment conditions Optimal heat treatment for steel materials is possible.

An object of the present invention is to provide a joining type tool made of a steel material and a cemented carbide having a cheaper joining.

(Means for Solving Problems) In the present invention, more stable joining conditions have been developed in solid phase diffusion joining of a steel material and a cemented carbide.

1) Cemented carbide is used as the insert metal.

2) In order to suppress intermetallic compounds, the composition (carbon content, etc.) of the cemented carbide as the insert metal was adjusted.

(Function) In the direct joining of alloy steels having additional elements such as Cr, W and Mo and ordinary cemented carbide, an intermetallic compound (presumably Fe ₃ W ₃ C) is easily formed at the joining interface. .

The mechanism of formation of this intermetallic compound has carbon content dependency, and if cemented carbide adjusted to an appropriate carbon content is used as an insert metal, direct joining of steel materials and cemented carbide is possible, and sufficient Bonding strength can be obtained. Also, a strong correlation with the temperature is recognized. Table 1 shows the presence or absence of the formation of intermetallic compounds under the temperature conditions of 1100 ° C. and 1150 ° C. in the combination of various alloy tool steels, high speed steels and the carbon content in cemented carbide. These 1100 ° C. and 1150 ° C. indicate the temperatures at the time of joining. (Note that heat treatment other than the joining treatment is not performed here.) In any case, the intermetallic compound is not formed at 1100 ° C, but is formed when the temperature further rises by 50 ° C. Therefore, the composition of the cemented carbide used as the insert metal must be selected according to the heat treatment temperature. The total amount of carbon in Table 1 indicates the total amount of carbon in the cemented carbide. Also, the holding time at 1000 ℃ and 1150 ℃ is 60
Minutes.

The presence or absence of the formation of intermetallic compounds on the joint surface is determined by cutting the tool in the direction perpendicular to the joint surface, polishing the cut surface to a mirror surface, etching with Murakami's reagent, and observing the composition with an optical microscope. Easy to check. If the intermetallic compound is formed on the joint surface, the intermetallic compound is deeply etched.

By the way, the mechanism of intermetallic compound formation in direct joining of alloy steel and cemented carbide is considered as follows. In general, alloy steel contains various additive elements such as Cr, Mo, W, and Co in addition to Fe and C, and these additive elements form carbides as M _x C _y type, and moreover, in the Fe base. It is in a solid solution state. Among various additive elements, Cr, Mo and the like have strong chemical bonding with carbon, while W has relatively weak bonding. Therefore, at the joining interface between the alloy steel and the cemented carbide, the carbon of WC, which is the cemented carbide component, is the solid solution Cr in the alloy steel
It is considered that unstable W is generated because it is absorbed by Mo or the like. It is considered that this W reacts with Fe and C in a more stable phase state to form an intermetallic compound Fe ₃ W ₃ C.

In order to suppress intermetallic compounds, as a method of compensating for the carbon shortage at the bonding interface, the cemented carbide is adjusted to a high carbon content,
It may be used as an insert metal. Although free carbon is generated in the cemented carbide with a high carbon composition, the free carbon near the bonding interface diffuses and disappears in the diffusion bonding process. In addition, insert metal (carbon content adjustment cemented carbide),
It is only necessary to have the minimum necessary thickness. For example, in the case of joining with alloy tool steel and high speed steel, 0.1 to 0.5 mm is sufficient, and if the thickness is more than this, non-diffused free carbon remains in the cemented carbide. The presence of residual free carbon means that there is non-diffused free carbon in the cemented carbide, which significantly reduces the strength of the base metal and is not preferable. Also,
If it is less than this, carbon cannot be sufficiently supplemented. in this way,
By using a cemented carbide as an insert metal with an adjusted carbon content, it becomes easy to join and combine with a steel material, the joint strength is improved, and heat treatment suitable for the steel material becomes possible.

(Example) A punch for cold forging shown in the drawing was produced and the tool life was examined. The punch is formed by joining a support portion 1 made of tool steel SKD11 and a processed portion 3 made of cemented carbide with a cemented carbide 2 as an insert metal having a high carbon content interposed therebetween. The cemented carbide 2 has a thickness of 0.1 mm. The cemented carbide of the working portion 3 is a cemented carbide having a large thermal expansion coefficient (WC75%, Co25%) 3b with a large thermal expansion coefficient and a cemented carbide having a large hardness and a small thermal expansion coefficient, which can be easily joined to the steel material of the supporting portion 1. (WC82%, Co18%) 3a are sequentially joined. On the other hand, the composition of cemented carbide 2 as insert metal (WC75%, Co25%, total carbon content 5.2%) is
For the heat treatment history during and after solid phase diffusion bonding (including bonding treatment, quenching of steel material, tempering treatment, hardened layer coating treatment and tool use), the above cemented carbide 3b and steel material 1 Select so that no intermetallic compound is formed on both joint surfaces of and. For solid solution diffusion bonding, capsule-type HIP diffusion bonding (temperature 1100 ° C, pressure 1000 kgf / cm ² , time 0.5 hour) is applied. The bonded punch is further coated with a hardened layer (not shown) made of TiC and TiN on the surface by CVD.
Next, quenching (1050 ° C x 40 minutes) is performed and tempering is performed at 200 ° C for 3 hours.

The cold forging punch thus produced was used to process the A material of the carbon steel S25C for machine structure. The results are shown in Table 2.

For comparison, the results obtained by punching for cold forging using high speed steel SKH9 are also shown. As is clear from Table 2, the punch tool life of this example was increased to several tens as compared with the comparative example.

In the processing part 3, it is easy to join the steel material of the support part 1,
It goes without saying that only the cemented carbide 3b having a large coefficient of thermal expansion may be used.

It is also possible to sequentially perform solid-phase diffusion bonding of two or more cemented carbides on the side not contacting the cemented carbide 2 as the insert metal in the processed portion 3 in the order of the coefficient of thermal expansion. As a result, a cemented carbide having a high hardness and a small thermal expansion coefficient is used at the tip of the machined portion 3, and a cemented carbide more suitable for joining is selected on the joining surface side to manufacture a joining type tool having excellent characteristics. .

Further, as the surface hardened layer of the bonded tool, generally, a single layer or multiple layers of various carbides, nitrides, carbonitrides, borides or silicides of transition metals and / or oxides of Al, Y, Zr, etc. Alternatively, multiple layers can be used.

(Effect of the invention) In the high hardness material joining type tool according to the present invention, by using cemented carbide for the insert metal, the joint compressive strength is dramatically improved and stabilized, and the tool life is extended.

Further, since the cemented carbide as the insert metal suitable for the steel material to be joined can be selected, it becomes possible to apply the optimum heat treatment to the steel material.

The solid phase diffusion bonding according to the present invention is applied to various plastic working tools such as various forging, forging, drawing, drawing, punching, bending and cutting, and cutting tools in general. Further, it can be applied to various fields as a machine part according to the application.

[Brief description of drawings]

The drawing is a plan view of a punch for cold forging. 1 ... Supporting part (steel material), 2 ... Cemented carbide as insert metal, 3,3a, 3b ... Machining part (cemented carbide).

Claims (3)

[Claims] 1. A machined portion made of a first cemented carbide, an intermediate portion made of an insert metal made of a second cemented carbide different from the first cemented carbide, and a supporting portion made of a steel material. Are sequentially joined, and both interfaces between the intermediate portion and the processed portion and the support portion are joined surfaces by solid-phase diffusion, and both joined surfaces have a high hardness material joining type tool having a composition containing no intermetallic compound. . 2. The high-hardness material-bonding tool according to claim 1, wherein the processed portion is composed of a plurality of processed portion portions made of different cemented carbides. The high hardness material joining type tool, wherein the parts are joined so that the coefficient of thermal expansion gradually decreases from the side in contact with the intermediate part. 3. A high-hardness material-bonded tool according to claim 1, wherein various transition metal carbides, nitrides, carbonitrides, borides or suicides and / or Al, Y, Zr are used. A high-hardness material-bonding tool characterized in that the surface is coated with a hardened layer composed of a single layer, multiple layers or multiple layers of oxides such as.