JP2634236B2 - Sintered materials for tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a sintered material for a tool used in cutting or plastic working of a high hardness material such as hardened steel or cemented carbide, or a heat resistant alloy. About.

<Prior art> When machining hardened steel or a high-hardness material such as a nickel-base heat-resistant alloy or a cobalt-base heat-resistant alloy, a carbide powder of a high-melting point metal such as tungsten is generally mixed with an iron-based metal such as iron, cobalt or nickel. Sintered cemented carbide has been used.

In recent years, in addition to the above-mentioned cemented carbide being used not as a tool but as an object to be processed, and in order to meet strict requirements for processing conditions, sintered diamond and cubic boron nitride ( A device using a sintered body or the like has been developed. Sintered diamond is obtained by sintering diamond particles at a high temperature and high pressure using a cemented carbide as a binder, but is fundamentally unsuitable for processing steel or the like having a strong affinity for carbon.
In this regard, the CBN sintered body, which has the second highest hardness after diamond, has little reaction with iron-based metals, and therefore, in addition to high-hardness materials such as hardened steel and cemented carbide, nickel-based It is effective for processing heat-resistant alloys and cobalt-based heat-resistant alloys.

Most conventional CBN sintered bodies are obtained by mixing ceramics such as titanium carbide and titanium nitride as a binder with CBN powder and sintering them under high temperature and high pressure. As the binder, in addition to the above, silicon or zirconium carbide, silicon or zirconium nitride, an intermetallic compound of aluminum and titanium, an intermetallic compound of aluminum and zirconium, and the like are known.

<Problems to be Solved by the Invention> In the case of a tool using a conventional CBN sintered body, the hardness of the binder phase is reduced in a high-temperature region. The particles of CBN tend to fall off from the phase, which often leads to a decrease in wear resistance.
In addition, when such a tool is incorporated into a processing machine that performs automatic operation for a long time, the occurrence of sudden tool loss should be absolutely avoided in terms of damage to the processing machine and a decrease in equipment operation rate. However, this type of conventional CBN sintered body has not pursued high hardness but has sufficient toughness.

<Means for Solving the Problems> The present inventors have paid attention to partially stabilized zirconia (hereinafter, referred to as PSZ) having particularly high fracture toughness among ceramics, and have also focused on aluminum oxide (alumina: hereinafter, Al).
₂ O ₃ ) has the same room-temperature hardness as titanium nitride and titanium boride, etc., and also focuses on the fact that the hardness in the high-temperature state in the range of 600 to 800 ° C. is higher than these.
Various experiments were conducted to determine whether PSZ and Al ₂ O ₃ were effective as binders for CBN.

The present invention has been made based on the above experimental results, and the first sintered material for a tool according to the present invention has a particle size of 40 to 90% by volume of CBN and 5 to 55% by volume of PSZ. It is obtained by sintering powder and 1 to 10% by volume of at least one of aluminum (hereinafter referred to as Al) and titanium (hereinafter referred to as Ti).

Here, as the PSZ stabilizer, calcium oxide or the like may be employed in addition to yttrium oxide in some cases.

The second sintered material for a tool according to the present invention is 40 to 90% by volume of CBN particles, 5 to 55% by volume of ZrO ₂ particles and Al ₂ O ₃ particles. The ZrO _{2 in} this mixture
Of 10 to 30% by volume and 1 to 10% by volume of Al
And at least one of Ti and Ti.

In this case, a CBN powder, a mixture of ZrO ₂ powder and Al ₂ O ₃ powder, or a PSZ powder and at least one of Al and Ti are uniformly mixed and stirred. After that, this is charged into a container of high melting point material and hot isostatic pressing device (HI
P) or other ultra-high pressure generator, for example, pressurizing in the range of 40 to 60 kbar (hereinafter referred to as Kb)
By heating in the range of 1800 ° C. and maintaining this state for about 0.5 to 30 minutes, the sintered material for a tool of the present invention is obtained.

<Operation> CBN is a main component as a sintered material for tools. If the content is less than 40% by volume, it is difficult to reflect the hardness of CBN itself, and sufficient wear resistance cannot be obtained. Conversely, if this CBN exceeds 90% by volume, a part of the CBN undergoes a phase transition to a hexagonal crystal during sintering, and the sinterability deteriorates.

On the other hand, since PSZ or a mixture of ZrO ₂ and Al ₂ O ₃ exhibits properties as a binder for CBN, if these are less than 5% by volume, the amount of CBN in the sintered material for tools is relatively large. Too much, the sinterability deteriorates, leading to a decrease in wear resistance and toughness. Conversely, if this PSZ or mixture exceeds 55% by volume, CBN
Becomes relatively too small, and it becomes difficult to reflect the hardness of CBN itself in the sintered material for tools, which also leads to a decrease in wear resistance. Incidentally, improved toughness as the proportion of ZrO ₃ with respect for Al ₂ O ₃ general trend, the hardness of the more binding phase the proportion of Al ₂ O ₃ is increased conversely. From the above balance, Z against Al ₂ O ₃
It is desirable to keep rO ₂ in a proportion of 10 to 30% by volume.

Further, Al and Ti diffuse into the grain boundaries of CBN to form a dense sintered structure without voids, so that the toughness of the sintered material for tools is significantly improved. In this case, if these are less than 1% by volume, sufficient toughness cannot be obtained. On the other hand, when these contents exceed 10% by volume, they act to reduce the hardness of the binder phase, and thus the wear resistance deteriorates.

<Examples> CBN synthesized by a non-catalytic method and having a particle size in the range of 1 to 3 micrometers (hereinafter referred to as μm), and an average particle size prepared by adding 3 mol% of yttrium oxide to 0.3 μm.
m of PSZ and Al or Ti or Al and Ti having an average particle size of 0.1 μm.
Into a small planetary mill with tungsten carbide (hereinafter referred to as WC) based cemented carbide, and further promote the mixing of them with a total volume of 35% of these powders.
% Of methyl alcohol was added to the mill, covered and kneaded for 3 hours. Then, the lid of the mill was removed in an inert gas atmosphere, and the mill was heated to 120 ° C. to evaporate the methyl alcohol, and the kneaded raw material powder was dried.

On the other hand, a sodium chloride (hereinafter referred to as NaCl) powder granule is pressed into a cylindrical body having an inner diameter of 8 mm and a length of 10 mm. The lower lid is attached integrally, and a 20μm-thick zirconium foil is attached to the inner surface of the lower lid.
Prepare a plate on which a disc made of a base cemented carbide is placed.

Then, the raw material powder after completion of the drying is charged in the inert gas atmosphere onto the disk in the container body so as to have a thickness of 6 mm, and is compacted with a protruding rod. Place the same WC-based cemented carbide disk as
After stacking a 20μm thick zirconium foil on this,
The upper lid made of NaCl prepared in the same manner as above is fitted into the container main body, and the raw material powder is sealed in a container composed of the container main body, the lower lid, and the upper lid.

Next, the above-mentioned container was attached to the ultra-high pressure generator, and 50 Kb
The pressure was maintained at a temperature of 1650 ° C. for 30 minutes, and the raw material powder was sintered to obtain a cylindrical sintered material for a tool having a WC-based cemented carbide bonded to both ends. Then, the tool sintered material is cut out in a state where the discs are bonded together to finish a cutting edge for a cutting tool, and this is inserted into a square WC-based cemented carbide chip prepared in advance through a silver solder. And a rake angle of 0 °, a relief angle of 5 °, and a nose radius of curvature of 1 mm were prepared.

Using this tool, a cutting speed of 120 per minute was applied to a high carbon bearing steel (SUJ2) in the form of a round bar with a Rockwell hardness of 62.
After turning by a distance equivalent to a length of 100 meters with a cutting depth of 20 μm and a cutting speed of 30 μm per revolution of the spindle, the amount of wear on the flank of the cutting edge and the cutting edge The Vickers hardness of the CBN sintered material to be measured was measured by changing the ratio of each particle constituting the raw material powder. During this turning, cutting oil was sprayed and supplied.

Table 1 shows the results of these measurements. Incidentally, when a commercially available CBN sintered material using titanium nitride as a binder was used, the Vickers hardness was 2500 and the flank wear of the cutting edge was 40 μm. Was.

As is clear from the results shown in Table 1, those containing 65% by volume of CBN powder (sample numbers: 1-13 to 1-15) have a wear amount of the flank of the cutting edge of 36 to 37 μm. Since it was within the range and had good wear resistance, it was confirmed that the effect of increasing the toughness of the binder phase appeared. If the CBN powder is less than 40% by volume (Sample No. 1-1) or more than 90% by volume (Sample No. 1-22), the cutting edge is chipped. In the case where the powder particles are in the range of 40 to 90% by volume (sample numbers: 1-2 to 1-21), they can be subjected to turning without causing any chipping on the cutting edge.

Next, the CBN particles shown in Table 1 were composed of ZrO ₂ particles and Al ₂ O ₃ particles having an average particle diameter of 0.3 μm, respectively, and their volume ratio was 3: 7 (= ZrO ₂ : Al ₂ O ₃ ) and a mixture adjusted to Al or Ti or Al and Ti shown in Table 1 to prepare a CBN sintered material in the same manner as described above, and changing the ratio of each powder particle The wear amount of the flank of the cutting edge and the Vickers hardness of this CBN sintered material were measured.

 Table 2 shows the measurement results.

As is clear from Table 2, in the case of containing 65% by volume of CBN powder particles (sample numbers: 2-13 to 2-15), the wear amount of the flank of the cutting edge falls within the range of 34 to 35 μm. The high wear resistance confirmed that the effect of increasing the toughness of the binder phase appeared. Also, CBN powder is 40% by volume
Samples with less than (sample number: 2-1) or more than 90% by volume (sample number: 2-22) have chipped cutting edges,
In the case where the BN particles are in the range of 40 to 90% by volume (sample numbers: 2-2 to 2-21), the BN can be subjected to turning without causing any chipping.

<Effect of the Invention> According to the sintered material for a tool of the present invention, since a binder mainly composed of partially stabilized zirconia having high toughness or Al ₃ O ₃ having high hardness at high temperature is used, CBN retention is achieved. It is possible to provide a sintered material for a tool whose capability is improved as compared with the conventional one, the wear resistance can be improved, and chipping and chipping are reduced.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Isao Hirata 4-6-22, Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries, Ltd. Hiroshima Laboratory (72) Inventor, Fukushi Yasuda 2-5-2, Marunouchi, Chiyoda-ku, Tokyo No. 1 Inside Mitsubishi Heavy Industries, Ltd.

Claims (3)

(57) [Claims] 1 to 40% to 90% by volume of cubic boron nitride particles; 5 to 55% by volume of partially stabilized zirconia particles;
A sintered material for tools obtained by sintering 1 to 10% by volume of at least one of aluminum and titanium particles. 2. The sintered material for a tool according to claim 1, wherein the stabilizer for partially stabilized zirconia is yttrium oxide. 3. A mixture of 40 to 90% by volume of cubic boron nitride particles and 5 to 55% by volume of zirconium oxide particles and aluminum oxide particles, wherein the zirconium oxide occupies the mixture. Is a sintered material for a tool obtained by sintering 10 to 30% by volume of at least one of aluminum and titanium particles of 1 to 10% by volume.