JPS6219397B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire drawing composite die with excellent performance and a method for manufacturing the same.

A conventional wire-based composite die is known to have a structure in which the outer periphery of a diamond sintered body using Co as a binder is surrounded by a WC-Co alloy (Japanese Unexamined Patent Publication No. 50-26746), and is commercially available. has been done.

The inventors conducted wire drawing tests on various materials using the diamond sintered die. As a result, it was found that the life of the die was significantly reduced under severe conditions where the tensile strength of the wire was high and the drawing speed was high, or when the wire was made of an iron group metal.

Therefore, the present inventors investigated the cause of this. As a result, when the tensile strength of the wire is high and the wire drawing speed is high, the temperature of the diamond particles increases due to frictional heat, and due to Co, which is the catalyst metal of diamond, near the bonding part of the diamond particles,
It is thought that due to deterioration of the bond between diamond particles, or due to the difference in thermal expansion between diamond and Co, tensile stress was generated in the diamond bond when the temperature rose, causing it to break and accelerate wear of the die. Furthermore, when drawing iron group metals, since diamond and iron group metals have good affinity, it was thought that the diamonds would react and the amount of wear would increase.

The present inventors have conducted repeated research in order to improve these drawbacks. As a result, it was concluded that high-pressure phase type boron nitride, especially cubic boron nitride (CubicBN, abbreviated as CBN) sintered body should be used instead of diamond sintered body. In other words, CBN is a hard substance second only to diamond, and has little reactivity with iron group metals at high temperatures, and sintered bodies made from CBN using an appropriate binder compensate for the drawbacks of diamond sintered bodies. It was thought that it could be done.

Therefore, we prototyped a wire drawing die with a structure in which a CBN sintered body was surrounded by a WC-Co alloy, but when a suitable binder such as TiN and Al alloy or Al ₂ O ₃ was used, the temperature of the CBN sintered body was 1100℃ to 1300℃. Although sintering is possible at a low temperature of °C, at this temperature, the WC-Co alloy does not generate a liquid phase, so the bonding with the sintered body is poor, and the WC
- Cracks occurred in the Co support. Therefore, the sintering temperature was raised to the point where the liquid phase of WC-Co appeared, and CBN was sintered and bonded to the WC-Co alloy support. As a result, the interface between the CBN sintered body and the WC-Co alloy support was bonded, there were no cracks in the WC-Co support, and the sintered body had high hardness, but the CBN sintered body was very brittle. It was not possible to fully demonstrate its performance as a body. The reason for this is that the sintering temperature was too high, so during sintering, CBN and the binder or CBN and the eutectic melt of WC-Co reacted, producing boride at the CBN grain boundaries.
It was thought that this may be due to the brittleness of this bolide.

Therefore, the present inventors investigated materials that can be bonded even at low temperatures, and found that (MoW)C is an iron group metal,
In particular, we discovered that (MoW) C-based cermet, which is an alloy bonded with Ni and Co, satisfies the above characteristics.
This has led to the present invention. That is, as shown in Fig. 1, the results of differential thermal measurement when the stamped bodies of (MoW) C-based cermet and WC-based cermet were heated are shown. , a liquid phase appears at a low temperature of about 130°C, so even if the CBN sintered body is sintered at a temperature that does not deteriorate its performance, a liquid phase will appear and the sintered body and (MoW) C-based cermet will not bond together. to strengthen it. In addition, at this time, the CBN sintered body and CBN
Bolite generation is observed at the interface between the sintered body and the (MoW) C-based cermet, but since the temperature is lower than when using WC-based cermet, the amount generated is small and does not become brittle, which improves the performance of the CBN sintered body. was able to fully demonstrate. If the performance of the CBN sintered body deteriorates when the liquid phase in the support penetrates into the sintered body, Zr.
It is possible to insert a metal foil of Group A or Group A such as Hf.Nb.Ta.

Furthermore, (Mo/W)C-based cermets have higher strength at high temperatures than WC-based cermets, and the amount of strain required to break is large, so they do not break even when ultra-high pressure is applied during sintering. It can be used and is excellent as a support for dice. Note that (MoW) C-based cermet has almost the same properties as WC-Co in other properties such as transverse rupture strength, thermal conductivity, thermal expansion coefficient, corrosion resistance, and oxidation resistance.

One of the present inventions is a CBN sintered body for wire drawing dies, in which the outer periphery of the CBN sintered body is surrounded by a cermet in which carbide crystals in the form of C, whose main component is molybdenum (MoW), are bonded with iron group metals. Regarding.
Another aspect of the present invention relates to a method for manufacturing the CBN sintered body for dies, which includes a pre-sintered ring in which molybdenum-based (MoW) C-type carbide crystals are bonded with an iron group metal. CBN powder or a mixed powder of CBN and a binder is filled into a shaped cermet, and the CBN is sintered at a stable temperature and pressure, and the CBN sintered body is brought into close contact with the cermet. This article relates to a method for manufacturing CBN sintered bodies for wire drawing dies.

(Mo/W) in the cermet used in the present invention
The carbide crystal represented by the form C has an atomic volume ratio of Mo to W of 1:1 or more;
Fe, Co, Ni, or an alloy thereof is added as a binder to form a sintered body. The amount of bonding metal in the cermet is selected to provide the desired stiffness and toughness, preferably in the composition range of 5 to 40% by volume of the entire cermet. This cermet is sintered at a temperature of about 1200°C or more and 1450°C or less in vacuum or in an inert gas or reducing gas atmosphere. In this pre-sintered ring-shaped cermet,
CBN powder or a mixed powder of CBN and binder is filled and sintered under ultra-high pressure and high temperature, but the pressure and temperature range at this time is within the range where CBN is thermodynamically stable, so it is usually , hot press at a temperature of approximately 1100℃ or higher and a pressure of 40kd or higher.

Note that (Mo・W)C used in the present invention has a lower specific gravity than WC, and in terms of raw material price, Mo is lower than W.
(Mo・W)C is about half cheaper than WC for the same volume, and since the raw material price of W has been rising rapidly in recent years, this is also a major advantage of the present invention. There is one.

Examples will be described below.

Example 1 A sintered body having an outer diameter of 10 mm, an inner diameter of 2 mm, and a height of 4 mm was prepared from a (Mo ₉ Wi) C--10 wt% Co, 10 wt% Ni alloy. This sintered body was filled with a mixed powder of 80% by volume of CBN and a binder, and thin plates of cermet having the same composition as the above-mentioned (Mo ₉ , W)C—Co, Ni alloy were placed above and below. As a binding material for CBN,
A mixed powder of TiN and Al was used. Using an ultra-high pressure and high temperature device, the pressure was first raised to 50kd, then electricity was started, the temperature was raised to 1230°C, and the temperature was maintained for 10 minutes. When the sample was taken out after the temperature and pressure were lowered, the appearance was clean with good dimensional accuracy. In addition, the sintered body part was in complete contact with the (MoW) C-Co, Ni alloy. A hole was made by laser processing in this sintered body part, and a wire drawing die for a wire diameter of 0.5 mm was created. . When the inner surface of this die hole was lap-finished, it showed a beautiful surface with no defects.

On the other hand, when the same operation was performed on a WC-15 wt% Co alloy, cracks were observed in the cemented carbide support when it was taken out after hot pressing.

Example 2 (Mo ₇ W ₃ ) C-15 wt% Co, 5 wt% Ni alloy with a diameter of 2 mm in the center of a cylinder with an outer diameter of 8 mm and a thickness of 3 mm.
A sintered body with holes 2 mm deep was created. This was filled with 90% by volume of mixed powder of CBN, TiN, and Al, and the top was plugged with Mo having an outer diameter of 3 mm. This was sintered under the same conditions as in Example 1 using an ultra-high pressure device. The obtained sintered body has no cracks and has a diameter of about 2
mm, thickness 1.5mm CBN sintered body part is (MoW)C-
It was completely adhered to the Co and Ni alloys.

The WC-15 wt% Co alloy was sintered under the same conditions as the (MoW) C-Co/Ni alloy, except that the sintering temperature was increased to 1350°C. The obtained sintered body has no cracks,
The CBN sintered body was completely adhered to the WC-Co alloy. When these two types of sintered bodies were processed into a die with a hole diameter of 0.2 mm and a steel cord drawing test was performed, the die of the (Mo/W)C-Co/Ni support of the present invention was 3 tons. While it was possible to draw wire,
The die with WC-Co support could only draw 0.1t. As a result of examining the products of both sintered bodies by X-ray diffraction, it was found that most of the products of the (MoW)C-CoNi support were CBN and intermetallic compounds of TiN and Al. The one with WC-Co support is CBN
The liquid phase of WC-Co penetrates into the sintered body, and a large amount of
Borite of Co and W was generated.

Example 3 (Mo ₈ W ₂ ) C-15 wt% Co, 10 wt% Ni alloy with a diameter of 3 in the center of a cylinder with an outer diameter of 8 mm and a thickness of 6 mm.
A sintered body with holes of 4 mm in length and 4 mm in depth was prepared. Fill this with CBN powder and attach the upper part with an outer diameter of 5 mm.
I plugged it with Mo. This was sintered under the same conditions as in Example 1 using an ultra-high pressure device. The obtained sintered body is bonded with Ni and Co, and (MoW)C-Co・
It was strongly bonded to Ni. In order to compare with the one according to the present invention, a WC-20 wt% Co alloy of the same shape was used and sintered under the same conditions, but it was not sintered because the temperature was below the liquid phase appearance temperature of WC-Co. Therefore, by increasing the sintering temperature to 1400°C, a uniform sintered body could be obtained. When we performed X-ray diffraction on both of these, only a small amount of boride was detected on the (Mo/W)C-CoNi support.
Large amounts of Co and W borides were detected on the WC-Co support. Next, these sintered bodies are made with a hole diameter of 0.6 mm.
Processed into dice. When we conducted a W wire drawing test with this, we found that the die with the C—Co/Ni support could draw 3.0 tons of wire, whereas the WC—Co
The supporting die had a drawing capacity of 1.0 t.

Example 4 (Mo ₅ W ₅ )C-15% by weight Co alloy, outer diameter 14
A sintered body was prepared by making a hole with an inner diameter of 5 mm in a cylinder with a diameter of 12 mm and a height of 12 mm. In this, 40% by volume CBN and Al ₂ O ₃
A Ta foil was inserted between the two to prevent direct contact between the mixed powder and the (MoW)C-Co alloy, and the gap was plugged with Ni.
This was sintered at 1200°C using an ultra-high pressure device.

After lowering the temperature and pressure, we examined the sintered body and found that the sintered body was firmly bonded to (Mo/W)C-Co through the Ta foil.
It was joined to the support.

[Brief explanation of the drawing]

Figure 1 shows (Mo ₉ W ₁ )C-Co Ni alloy and WC.
- This shows the results of differential thermal measurement when a stamped Co alloy body was heated in a vacuum. The temperature at which an endothermic reaction is observed indicates the temperature at which each liquid phase appears. In the figure, A is (Mo ₉ W ₁ )C-10% by weight Co, 10% by weight Ni, and B is WC-15% by weight Co.

Claims (1)

[Claims] 1. A wire drawing die in which the outer periphery of a high-pressure phase type boron nitride sintered body is surrounded by a cermet in which C-type carbide crystals mainly composed of molybdenum (MoW) are bonded with an iron group metal. sintered body. 2 The hard compound phase of cermet is (Mo・W)C _x
The sintered body for a wire drawing die according to claim 1, wherein x is in the range of 0.8 to 0.98. 3. The sintered body for a wire drawing die according to claim 1 or 2, wherein the high-pressure phase boron nitride is cubic boron nitride. 4. High-pressure phase boron nitride powder or high-pressure phase boron nitride is bonded to a pre-sintered ring-shaped cermet made of carbide crystals of (Mo/W)C, whose main component is molybdenum, bonded with iron group metals. A sintering method for wire drawing dies characterized by filling a mixed powder of the material and sintering high-pressure phase boron nitride under ultra-high pressure and high temperature, and also bringing the high-pressure phase boron nitride sintered body into close contact with cermet. How the body is manufactured. 5 The hard compound phase of cermet is (Mo・W)C _x
5. The method for producing a sintered body for wire drawing dies according to claim 4, wherein x is in the range of 0.8 to 0.98. 6. The method for producing a sintered body for a wire drawing die according to claim 4 or 5, wherein the high-pressure phase boron nitride is cubic boron nitride.