JPH0436557B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to a cubic boron nitride (hereinafter referred to as CBN) sintered composite used for cutting tools, etc., and more specifically, a plate-shaped CBN sintered composite having a predetermined composition on one or both sides. This invention relates to a CBN sintered composite that can be firmly brazed to the shank of a tool by closely adhering an alloy plate to the shank of a tool, and suppresses the occurrence of peeling. [Prior art] Conventionally, a cemented carbide substrate such as tungsten carbide (WC) is bonded to one or both sides of a CBN sintered composite to form a composite, which is then cut into a predetermined shape and used with tools such as drills and bits. There are commercially available tools with excellent cutting performance that are brazed to the tip of the shank. [Problems to be solved by the invention] However, the CBN sintered composite to be brazed is
Particularly when the tool is a small item or a small-diameter cutting tool, it must be made as thin as possible, but if it is made thinner by grinding, it may warp due to internal stress during manufacturing, thermal stress during brazing, etc. This may cause peeling or chipping, so sintered bodies sandwiched with cemented carbide or metal on both sides are not suitable for use as materials for drills.
Horizontal peeling is likely to occur in sintered bodies. Furthermore, the coefficient of thermal expansion of the cemented carbide mentioned above is much smaller than that of Fe, Ni, Cu, etc., but it is still larger than that of CBN sintered body.
In addition, the Young's modulus is large, and the temperature is high during cutting.
Since the temperature reaches 100 to 1000°C, the above-mentioned peeling phenomenon and a decrease in strength occur. Therefore, the conditions required for a composite of a CBN sintered body and a substrate are: (1) The bonding strength between the CBN sintered body and the substrate is high. (2) The difference in the coefficient of thermal expansion between the two is small, and the thermal stress generated between the two is suppressed.
Or, there should be no peeling or damage when used as a tool. (3) After brazing, maintain sufficient strength for tool use. (4) Possible to braze in the atmosphere. It is. The present inventors have conducted extensive research to obtain a CBN sintered composite that satisfies the above conditions. First, using known technology such as cemented carbide, Fe, Ni,
Using metal plates such as Co, Al, and Cu, we tried to fabricate CBN sintered composites with a sandwich structure using ultrahigh-pressure equipment commonly used by those skilled in the art, but most of them cracked or failed during the fabrication process. Horizontal peeling phenomenon occurred during brazing. In other words, it was shown that even if the metal is a soft metal, when joining the metal and CBN sintered body under ultra-high pressure, the thermal stress generated within the composite is large and can cause damage. Therefore, the joint strength when brazing is high,
When we created CBN sintered composites using alloy plates containing various proportions of Fe-Ni and Fe-Ni-Co, which have different thermal expansion properties, we found that using alloys with specific compositions caused peeling phenomena and cracks. We found that it was suppressed. JP-A-61-34108 uses Ni, Co, Fe, etc. or their alloys, but this is not intended to reduce thermal expansion, but to absorb thermal expansion. However, the technical idea is different from that of the present invention, and there is no description or suggestion of forming an alloy having the composition of the present invention. The present invention was developed based on the above knowledge, and does not cause warping or peeling during manufacturing, and can be easily brazed to the shank of a tool. do not
The purpose is to provide a CBN sintered composite. [Means for Solving the Problems] The present invention has been made to achieve the above object, and its gist is that a CBN sintered body containing 20 to 50 wt% of Ni and the balance mainly of Fe on one or both sides of the CBN sintered body. At normal temperature~
A CBN sintered composite formed by closely adhering alloy plates with an average linear expansion coefficient of 8×10 ^-6 1/°C or less at 500°C, or 20 to 50wt of Ni on one or both sides of the CBN sintered body.
%, Co30wt% or less, balance mainly Fe at room temperature ~
It is a CBN sintered composite made by closely adhering alloy plates with an average linear expansion coefficient of 8×10 ^-6 1/°C or less at 500°C. [Specific structure and operation of the invention] The present invention will be explained below. CBN sintered composite of the present invention (hereinafter referred to as composite)
As is well known, the CBN sintering raw material used in
CBN powder is used by adding metals such as Ni, Co, Al, etc., and ceramics such as oxides, nitrides, and carbides.
At this time, it may be sandwiched between disks made of highly rigid cemented carbide or cermet, and pre-formed using an ultra-high pressure device. In addition, as Fe-Ni or Fe-Ni-Co alloy, Fe is 20 to 50 wt%, the balance is Fe, or
In an alloy with Ni20~50wt%, Co30wt% or less remaining Fe,
In both cases, the average linear expansion coefficient from room temperature to 500℃ is 8×
10 ^-6 1/℃ or less is used. The above alloy has an average linear expansion coefficient of 8×10 ^-6 between room temperature and 500℃.
1/℃ or less, other metals such as Cr and Mo
may contain. This alloy is formed into an alloy plate. The appropriate thickness of this alloy plate is 0.1 to 0.5 mm. If the thickness exceeds 0.5 mm, the rigidity of the blade will decrease, impairing cutting performance, and if the thickness is less than 0.1 mm, it will be difficult to adjust the dimensions, which is undesirable. To explain an example of a method of making a CBN sintered composite using the above CBN sintering raw material and alloy plate, inside a NaCl sleeve with a graphite heater around it,
These are stacked in layers, and blocks made of ceramics or cemented carbide are placed above and below to prevent deformation and to obtain a flat composite.The blocks are then filled into an ultra-high pressure device and subjected to high temperature and pressure. to make a sintered composite. At this time, the temperature is 1300-1500℃,
Appropriate pressure is 30 to 50 Kb and time is 10 to 60 minutes. In this way, a composite A in which alloy plates 2 are attached to both sides of a CBN sintered body 1 as shown in FIG. 1, or an alloy plate 2 attached to one side of a CBN sintered body 1 as shown in FIG. A complex B is obtained, to which is attached. In addition, the melting point of the alloy plate is 1400-1500℃,
Since the sintering temperature of the CBN sintered body is lower than this, it is possible to join both directly, but as shown in Figures 3 and 4 for composites A' and B', there is At the same time as it absorbs the difference in expansion coefficient (due to its high melting point), the Fe alloy component increases during hot pressing (HP).
In order to prevent W, Mo, Ta, and Nb from diffusing into the CBN sintered body layer and deteriorating heat resistance and wear resistance,
A known method of interposing a metal 3 such as the like may also be used. The HP conditions differ depending on the selection of the binder that forms the CBN sintered body, but especially at high temperatures (>1400
°C), better results are obtained by interposing Ta or Mo. It is desirable to use a plate of Ta or Mo with a thickness of 50 μm to 0.2 mm. The thickness of these composites is not particularly limited in the case of a sandwich structure, but is 0.5 to 2.5 in the case of one-sided bonding.
mm, especially preferably 0.7 to 2.0 mm. If the thickness is less than 0.5 mm, the strength will be poor, and if it exceeds 2.5 mm, problems such as peeling will hardly occur even with conventional cemented carbide substrates, and the advantages of the present invention will be reduced. The composite A or A' having the above structure is mainly used for drilling, and after being cut into a predetermined shape, it is brazed to the tip of the shank 4 as shown in FIGS. 5a and 5b. This brazing can be easily performed in the atmosphere. In addition, the composite B or B' is brazed to various shanks such as the shank 4 of an end mill or the shank 4 of a cutting tool, as shown in FIGS. 6a, b, and 7. used as. The composites of the present invention do not warp or peel during manufacture, and cutting tools equipped with these composites do not peel off even though the composite parts are exposed to high temperatures during use. There's nothing to do. The reason for this is that, as mentioned above, the alloy plate used in the present invention is an Fe-based alloy with a coefficient of linear expansion of 8 x 10 ^-6 1/°C or less between room temperature and 500°C, so it can be firmly bonded to the shank. 500℃ for Fe-based alloys.
In the above conditions, the yield stress decreases rapidly, so
The difference in expansion coefficient between the sintered body and the alloy plate does not cause internal stress, and the
Since the average coefficient of linear expansion below 8×10 ^-6 1/°C is below, no breakage occurs due to internal stress. [Example] Next, the present invention will be explained with reference to Examples and Comparative Examples. Example 1 70wt% CBN powder and 20wt% TiC powder were placed in a NaCl sleeve with a graphite heater attached to the outer periphery.
%, 2.5g of powder mixed with 10wt% of Al powder was added to the thickness
0.2mm Ni25wt%, Co17wt%, remaining Fe (hereinafter Fe−
25Ni−17Co), and then filled with hexagonal boron nitride (hBN) and cemented carbide plates above and below, mounted on a normal ultra-high pressure device, and heated at 40Kb and 1300℃. A complex was prepared by processing for 1 hour. Approximately 0.1mm of the altered portion of the upper and lower surfaces of this complex
Scraped, diameter 26.0mm, CBN sintered body thickness 1.5mm,
A composite A plate was prepared with an alloy plate thickness of 0.1 mm and a total thickness of 1.7 mm. This complex includes horizontal cracks, warps,
No other defects were observed. Next, a 5 mm square material was cut out from the composite plate using a wire cut electric discharge machine, and as shown in FIG. 8, the material was silver-brazed to a cemented carbide square bar 11, and then ground on four sides and tested. Piece 12 was created. Both ends of this test piece 12 are connected to the support 1
3 and 13, and the material portion was pressed to measure the bending strength, and it broke at the brazed portion 14. The strength at that time was 25Kg/ ^mm2 . In addition, the above composite was cut into a predetermined shape and brazed to the shank 4 to make the drill shown in Fig. 5 a and b, and a hole was drilled in SKD11 hardened steel without any problem. I was able to drill it. Example 2 CBN 80wt%, TiN 14wt%, Al6wt% in a NaCl sleeve with a graphite heater attached to the outer periphery
2.0g of mixed powder of Fe-
With the alloy plate made of 29Ni−17Co facing down,
It was sandwiched between Zr thin plates, and filled with Al ₂ O ₃ plates and NaCl plugs placed above and below, respectively, and placed in an ultra-high pressure device and processed at 45kb and 1350℃ for 1 hour to create a composite. . Remove about 0.1mm of this outer skin,
A flat plate of composite B having a diameter of 26 mm, a thickness of 1.2 mm, and an alloy plate thickness of 0.1 mm was obtained. A 5 mm square material was cut out from this flat plate, and as shown in FIG. 9, it was brazed to a steel block 15 and its compressive shear strength was measured, and it broke at the brazed portion 14 at 30 kg/mm ² . Also, cut out a long thin strip of 20 x 3 mm, and
The end mills shown in Figures a and b were made by brazing and hardened to Rockwell hardness HR60.
I performed grooving on SKD11 and was able to cut it without any problems. Comparative Example 1 CBN lined with two types of commercially available cemented carbide
When the cemented carbide of the sintered composite was ground and the total thickness was adjusted to 1.2 mm, and this was attached to an end mill and used, one cracked in the CBN sintered part during grinding, and the other During brazing, separation occurred at the boundary between the CBN sintered body and the cemented carbide. Examples 3 to 5, Comparative Examples 2 to 4 The bending strength was measured in the same manner as in Example 1, except that the alloy plates were variously changed. The results are shown in Table 1.

[Table] Examples 6 to 8, Comparative Examples 5 to 7 The bending strength was the same as in Example 1, except that the alloy plates were variously changed and various metals were interposed between the alloy plates and the CBN sintered body. was measured. The results are shown in Table 2.

[Table] Examples 9 to 12, Comparative Examples 8 to 10 Example 2 except that various alloy plates were used and various metals were interposed between the alloy plate and the CBN sintered body.
The compressive shear strength was measured in the same manner. The results are shown in Table 3.

〔Effect of the invention〕

As described above, the CBN sintered composite according to the present invention can be firmly brazed to the shank of a tool, and the internal stress caused by temperature changes can be suppressed.
Excellent cutting tools can be made without peeling or condensation during composite manufacturing, brazing, or cutting.

[Brief explanation of drawings]

Figures 1 to 4 are side views showing an example of a composite according to the present invention. Figure 1 is a diagram in which alloy plates are attached to both sides of a CBN sintered body, and Figure 2 is a diagram in which alloy plates are attached to one side of a CBN sintered body. Figure 3 shows the installation on both sides with metal interposed at the boundary, Figure 4 shows the installation on one side and metal at the boundary, and Figures 5a and b are the views shown in Figure 1 or Figure 3. This shows an example of a drill made using the composite shown in Figure 3. Figure 5a is a side view, and Figure 5b is a side view.
6 is a view taken along the - line in FIG. Figure 6b is a side view of the end mill, Figure 6b is a view taken along the - line in Figure 6a, Figure 7 is a side view of the cutting tool, Figure 8 is a diagram showing how to measure bending strength, Figure 9 is a diagram showing compression shear force. FIG. 3 is a diagram showing a measurement method. 1... CBN sintered body, 2... Alloy plate, 3... Metal, A... Composite of sandwich structure, A'...
A composite with a sandwich structure with metal interposed between them, B...A composite with an alloy plate bonded on one side,
B'...A composite with an alloy plate on one side and a metal sandwiched between them.

Claims (1)

[Claims] 1. On one or both sides of a cubic boron nitride sintered body, a film containing 20 to 50 wt% Ni and the balance Fe at room temperature to
A cubic boron nitride sintered composite made by closely adhering alloy plates with an average linear expansion coefficient of 8×10 ^-6 1/°C or less at 500°C. 2 W between the alloy plate and the cubic boron nitride sintered body,
The cubic boron nitride sintered composite according to claim 1, which is closely adhered with a metal plate selected from Mo, Ta, and Nb interposed therebetween. 3. On one or both sides of the cubic boron nitride sintered body, the average linear expansion coefficient between room temperature and 500°C is 8x, mainly consisting of 20 to 50 wt% Ni, 30 wt% or less Co, and the balance Fe.
A cubic boron nitride sintered composite made by closely adhering alloy plates with a temperature of 10 ^-6 1/℃ or less. 4 W between the alloy plate and the cubic boron nitride sintered body,
The cubic boron nitride sintered composite according to claim 3, which is closely adhered with a metal plate selected from Mo, Ta, and Nb interposed therebetween.