JPS639009B2 - - Google Patents

Description

[Detailed description of the invention]

Cubic boron nitride has the second highest hardness among materials after diamond, and also has good thermal conductivity.It also has no affinity with iron-based metals, which is the problem with diamond, and is extremely stable chemically. Therefore, it is expected to be used as a cutting tool for difficult-to-cut iron-based materials. In addition, with recent advances in ultra-high pressure sintering technology, cubic boron nitride, which is made by adding metal or ceramics to cubic boron nitride powder and sintering it, has been applied to tools, and its use is steadily increasing. It has been pointed out that the problem with this metal-bonded sintered compact is that under cutting conditions where the cutting edge is exposed to high temperatures, the strength of the cutting edge decreases due to the softening of the bonded metal, resulting in a significant deterioration in its performance. ing. On the other hand, when using a tool made of a cubic boron nitride sintered body of a ceramic matrix bonded with ceramics, the defects observed in the above-mentioned sintered body tool bonded with a metal were almost solved. There is a risk that the cubic boron nitride particles will fall off during cutting because the bonding force between the particles and the ceramic particles is not sufficient, and depending on the composition of the ceramic, the cubic boron nitride sintered body may There is also the risk of it becoming brittle. The present invention was made to solve the above problems, and when the tool is actually used, it has excellent wear resistance, heat resistance, and chipping resistance. This is an important condition, and the purpose of the present invention is to provide a tool that does not cause sudden breakage of the cutting edge, especially when the cubic boron nitride sintered tool is used in an automatic operation machine that emphasizes productivity. The purpose is to The present invention uses a Ti.Zr.Hf.Ta.Si nitride ceramic as a matrix of cubic boron nitride.
AlN powder is added to a seed or a mixed powder of two or more kinds, a mutual solid solution powder, or a mutual compound powder, and further a mixed powder of one or more kinds of Al.Fe.Co.Ni and a mutual compound powder are added to form a matrix part. This is a cubic boron nitride sintered tool for cutting that is made entirely of nitride-based ceramics and has excellent wear resistance, heat resistance, and chipping resistance. As mentioned above, Ti.Zr.Hf.Ta.Si nitride powder
The main reason for using a cubic boron nitride matrix containing AlN powder and Al.Fe.Co.Ni powder is when cutting highly hard and difficult-to-cut materials (H _R C50 or higher). The temperature of the cutting edge is
The temperature may rise to around 1200℃, and when cutting high-hardness materials intermittently, large mechanical shock stress is repeatedly applied to the tool. The performance of the tool as a tool is highly dependent on the composition of the matrix. Therefore, the characteristics required for the matrix composition are of course wear resistance and heat resistance, but when using tools for interrupted cutting as described above, particularly excellent thermal shock resistance and chipping resistance are required. It is also necessary that each particle of the matrix component is strongly bonded to the cubic boron nitride particles to firmly hold the cubic boron nitride particles. Based on the above points of view, as a result of numerous tests and studies using various test materials, Ti.Zr was found to be a matrix material that satisfies the characteristics of matrix components.
It has been found that adding AlN to ceramics containing Hf.Ta.Si nitride alone or in combination is particularly effective in improving matrix properties. The proportion of one or more of the above-mentioned ceramics mixed powder, mutual compound powder, or mutual solid solution powder in the cubic boron nitride sintered body is determined within the range of 69 to 15% by volume. If it exceeds 69 volume%, the hardness of the cubic boron nitride sintered body will decrease, that is, the wear resistance of the cubic boron nitride sintered body will decrease, and conversely, if it is less than 15 volume%, the cubic boron nitride sintered body will have a lower hardness. The dispersion of ceramics between crystalline boron nitride particles becomes non-uniform, and the toughness of the sintered body is significantly deteriorated. The reason for adding AlN is that AlN acts as a sintering aid to strengthen the bond between the cubic boron nitride particles and the above-mentioned ceramics during sintering. The crystalline boron nitride sintered body is extremely dense and has toughness. A good sintered body can be obtained when the amount of AlN added is in the range of 1 to 20% by volume, but if it is less than 1%, the degree of bonding between the cubic boron nitride particles and the ceramic particles of the matrix becomes insufficient. If it exceeds 20%, the degree of bonding between the cubic boron nitride particles and the ceramic particles serving as the matrix is sufficient, but the strength of the matrix portion decreases, which is not preferable. By the way, there is 1 of Al.Fe.Ni.Co in the matrix.
The purpose of adding seeds or mixed powders of two or more types, and mutual compound powders in an amount of 1 to 15% by volume is that under the sintering conditions described below, these molten metals will be mixed between cubic boron nitride particles or cubic boron nitride particles. - It is infiltrated between matrix particles and between matrix particles to ensure hydrostatic properties, and at the same time acts as a back conversion prevention material for cubic boron nitride, contributing to obtaining a dense and good sintered body. It is in. However, if the amount of these metal powders added is less than 1% by volume in the sintered body, the sinterability will deteriorate and pores will occur frequently, making it impossible to obtain a good sintered body. If it exceeds 15% by volume, the sinterability will be good, but it is not preferable because it will adversely affect the wear resistance and heat resistance of the sintered body. Hereinafter, the present invention will be explained by giving specific examples. Although a belt type device was used as the ultravoltage high temperature generator used to sinter the cubic boron nitride sintered tool of the present invention, any device that can withstand the generation of the desired pressure and temperature may be used. The type does not matter. As the material to be filled between the particles of the cubic boron nitride powder, the above-mentioned ceramic matrix material and metal powder are added and thoroughly mixed in a ball mill, and then used as a raw material powder. The raw materials prepared in advance in this way are filled into a reaction vessel, and a sintering reaction is carried out under ultra-high pressure and high temperature. This sintering reaction takes place at a temperature of about 1300-1500℃ and
A pressure of 60 kilobar was maintained for at least 15 minutes. The resulting sintered body was a cubic boron nitride sintered body that was dense, had high hardness, and was rich in chipping resistance, thermal shock resistance, and wear resistance. A throw-away chip was made using this sintered body, and various cutting tests were conducted using this sample, and the results were extremely excellent. Examples will be described below. Example 1 60% by volume of cubic boron nitride powder with an average particle size of 5μ and 10% by volume of TiN powder with an average particle size of 2μ, average particle size
10% by volume of TaN powder with 2μ, AlN powder with average particle size of 2μ
10% by volume, 7% by volume of Al powder of 350 mesh or less,
A mixed powder consisting of 3% by volume of Co powder of 350 mesh or less was mixed and stirred in a ball mill for about 50 hours to obtain a raw material powder. The raw material powder was filled into a reaction vessel and then heated to 55 kilobar. Under pressure and temperature conditions of 1400℃,
It was held for about 20 minutes, and then the pressure was removed simultaneously with cooling. This results in a microvits hardness of 3100Kg/
A hard and dense sintered body having a hardness of mm ² was obtained. Using this sintered body, we created an SNG433 throw-away chip and created a slotted groove for SKD11.
An interrupted cutting test was conducted on a workpiece material (JISG4404 alloy steel D11 class, H _R c60) by wet turning at a cutting speed of 70 m/min, depth of cut of 0.5 mm, and feed per revolution of 0.15 mm. As a result, the above test was carried out 10 times for 10 minutes each, and none of the chips showed any defects such as chipping or chipping, and the wear was normal. Example 2 Samples from sample 1 to sample 7 were sintered using the raw material powders shown in Table 1 in the proportions shown in the table using an ultra-high pressure and high temperature generator under the conditions shown in the table. In addition, the hardness of each sample sintered body is shown in the same table.

[Table] Throw-away chips were made from cubic boron nitride sintered bodies of various compositions according to the table above, and the same tests as in Example 1 were conducted, but all samples (throw-away chips) failed. Good results were obtained, showing normal wear and no problems such as chipping.

Claims (1)

[Claims] 1 Contains 30 to 70% by volume of cubic boron nitride powder with an average particle size of 20μ or less, the remainder being Ti, Zr, Hf,
Mixed powder of one or more kinds of Ta, Si nitrides, mutual solid solution powder or mutual compound powder and 1 to 20 volume % of AlN powder at 69 to 15 volume %,
A cubic boron nitride sintered body for cutting tools, which is sintered by adding 1 to 15% by volume of a mixed powder of one or more of Al, Fe, Co, and Ni and a mutual compound powder.