JPS6369767A - Cutting tip and machining tool - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a cutting tip and a processing tool, and more particularly to a high-speed cutting tip and a ceramic tip having impact resistance, high toughness, high strength, and high hardness. It relates to wear-resistant machining tools such as rolls and dies.

Conventional technology and problems Conventionally, A1□03-TiC has been used as a material for high-speed cutting tools for steel and cast iron because it exhibits excellent wear resistance during high-speed cutting and has a small coefficient of friction with iron. Ceramic tools were put into practical use and became mainstream. However, A]20. - T i C has poor toughness and insufficient impact resistance, so it has the drawback of being easily damaged and cannot be used stably.

Therefore, in recent years, Si3N4 ceramics, which have excellent mechanical strength, high hardness, and impact resistance, have been attracting attention as cutting tools.
513N4 has problems such as poor wear resistance, severe wear, and low versatility, and high machining resistance and low productivity.

Means for Solving the Problems The present invention was made in view of the problems of the conventional cutting tips and machining tools mentioned above, and they have high toughness and high hardness, and are particularly suitable for cutting tools such as high-grade hammer iron and ductile cast iron. As a result of extensive research and testing using a variety of materials in order to develop materials suitable for cutting tools, alumina-zirconia-silicon carbide composite sintered bodies with high impact resistance, high strength, and high toughness were found to be suitable for this purpose. I found something suitable.

The cutting tip and processing tool made of the impact-resistant, high-strength, high-toughness alumina-zirconia-silicon carbide composite sintered body of the present invention are made of partially stabilized zirconia with an average grain size of 0.1 to 1.0 μm. 50% by volume; 3-40% by volume of silicon carbide whiskers with a diameter of 1 μm or less and an aspect ratio of 3-200
(However, the total amount of the silicon carbide whiskers and the zirconia is 55% by volume or less); the remainder is substantially composed of alumina.

Next, the reason for limiting the range of components of the impact-resistant, high-strength, high-toughness alumina-zirconia-silicon carbide composite sintered body will be described.

Partially stabilized zirconia powder is too stable if the particle size is less than 0.1 μm, and becomes too unstable if it exceeds 1.0 μm, neither of which contributes to strength improvement, so the particle size range is reduced to 0. .1 to 1.0 μm. If the amount is less than 5%, the effect of increasing toughness will not be significant, and if it exceeds 50%, the hardness will decrease, so the amount is set in the range of 5 to 50%.

When the aspect ratio of silicon carbide whiskers is less than 3, the effect of increasing toughness is insufficient, and when the aspect ratio exceeds 200, the effect of increasing toughness decreases, so the range is set to 3 to 200. If the diameter exceeds 1+n+n, the strength decreases, so the diameter was set to 1 mm or less. The amount of silicon carbide whiskers needs to be at least 3% or more in order to exhibit its effects, and if it exceeds 40%, the strength will decrease, so it should be in the range of 3 to 40%.

If the total amount of the zirconia and carbonized whiskers exceeds 55%, too much whisker or zirconia will be added, resulting in a decrease in toughness or hardness, so the total amount is set to 55% or less.

The product of the present invention has excellent toughness, high hardness, and wear resistance, as well as excellent heat resistance and corrosion resistance, so it can be used in a wide range of applications from low-speed to high-speed cutting of castings and steel that require these properties. Not only is it suitable for use as a cutting tip, but it also has excellent thermal shock resistance and oxidation resistance, so it can be used as a hot working tool that is exposed to high temperatures for a relatively long time. Specific examples of temperature rise during use include indexable inserts, cutters, drills, end mills, etc. used for turning, milling, and drilling, mainly for high-speed cutting, heavy cutting, and interrupted cutting. As a wear-resistant hot working tool that is exposed to high temperatures for a relatively long period of time, it can be widely applied to hot compression dies, hot extrusion punches, hot wire drawing rolls, hot forging dies, etc.

Example Examples of the present invention will be specifically described below.

Alumina powder 70% by volume, silicon carbide rice car 15
% and 15% partially stabilized zirconia.

Alumina powder has a purity of 99% or more, an average particle size of 0°7 μm,
It is in the γ type crystal form. Silicon carbide whiskers are β-type crystals, with a diameter of 0.8 μm and a length of 20 to 200 μm.
The aspect ratio is 20-200. Zirconia powder is 2
Partially stabilized zirconia with an average particle size of 0.2 μm stabilized with mol% (3.5% by weight) ittria.

This raw material was mixed with ethyl alcohol in a ball mill using an alumina container and an alumina ball.
After 4 hours of mixing, these mixed powders were dried.

This mixed powder was filled into a graphite mold and hot-pressed into a disk having a diameter of 50 mm and a thickness of 5.5 mm in an argon gas atmosphere. The hot pressing conditions were a temperature of 1500° C., a molding pressure of 300 kg/cm”, and a time of 1 hour.

From these sintered bodies, a 12.7mm x 4.76mm GIS was cut and ground using a diamond grindstone.
An indexable tip conforming to the standard 5NGN430 type was created. A cutting test was conducted using this chip using a lathe under the following cutting conditions.

For comparison, a cutting test was conducted using a commercially available A1□03-TiC ceramic tip under the same conditions. Cutting conditions: Rigid material: Tough cast iron (equivalent to FC30 material) Cylinder inner diameter: 95 mm x Length: 150 mm Cutting speed: 142 m /min feed 0, 35 mm/rpm depth of cut 0
．． 25mm Number of cuts: 250 Finish cutting of the inner circumferential surface of the cylinder liner is performed under the above cutting conditions, and the occurrence of chip breakage and changes in finished dimensions are measured to estimate the degree of chip wear and determine the life of the chip. It was judged whether it was good or bad.

The results of the cutting test are shown in Figure 1.

Furthermore, a bending test piece with a thickness of 3 mm x width of 4 mm x length of 40 mm, a hardness measurement test piece of 4 x 10 x 10 mm, and a fracture toughness test piece were taken from these sintered bodies, the surfaces were mirror-finished, and the following tests were conducted. (1) Bending test (2) Hardness test (3) Fracture toughness test The test results are shown in Table 1.

As a comparative example, a test was conducted under the same conditions using Al2O3-TiC ceramics used in conventional cutting tips.

Table 1 (1) Bending test The three-point bending test method specified in JIS R1601 (bending strength test method for fine ceramics) was used. A load was applied at a crosshead speed of 0.5 mm/min to one point in the center between two supporting points arranged at a distance of 30 mm to the test piece, and the maximum load until the test piece broke was measured.

(2) Hardness test Hardness measurement was performed using a Vickers hardness meter.

(3) Fracture toughness test In this test, toughness was evaluated by the indentation method using a Vickers hardness meter. The toughness was evaluated by determining the fracture toughness Kc. Fracture toughness Kc was calculated by Shinryo's formula.

As a result of the cutting test, no abnormality such as chipping of the four ceramic chips of the present invention was observed, and the dimensional changes were Q.
The chip size was within 1mm, there were no problems, and the finished surface was good, whereas the comparative amount of commercially available A1□01-'[7jC Ceramics chips had three out of four chips with processed numbers of 138, 196, A chip breakage occurred on the 248th chip. Only one piece had no damage, and the dimensional change was 0.
．． 13+n+++, which was slightly larger than the inventive product, indicating that the inventive ceramic chip exhibits good impact resistance and abrasion resistance, whereas the comparative product has relatively low toughness and thus has poor impact resistance. , the wear resistance is poor, and it is recognized that the life of the ceramic chip of the present invention is significantly improved.

Also, as is clear from Table 1 showing the test results using test pieces, the bending strength is 74 k for the comparative amount of Al2O3-TiC.
It shows an improved strength of 115.3 kg/mm2 compared to Kc of the comparative amount.
It is recognized that the hardness is 7.2 MPa1, which is significantly higher than 4.2 MPav'''i, and it has excellent toughness and impact resistance.
It is recognized that it exhibits high hardness almost equivalent to that of C ceramics and has excellent wear resistance.

Effect The ceramic ring cutting tip and processing tool of the present invention are not only suitable for cutting tips that are strong against impact, have high toughness, and excellent wear resistance, but also have excellent thermal shock resistance and oxidation resistance. It can also be applied to hot processing tools such as hot wire drawing rolls, and has a remarkable practical effect in that it can be used stably over a long period of time.

[Brief explanation of the drawing]

Claims (1)

[Claims] 5-50% by volume of partially stabilized zirconia with an average particle size of 0.1-1.0 μm; diameter of 1 μm or less, aspect ratio 3-2
00 silicon carbide whiskers 3 to 40% by volume (however, the total of the silicon carbide whiskers and the zirconia is 55% by volume or less); the remainder is essentially alumina.
A cutting tip and a machining tool comprising a zirconia-silicon carbide composite sintered body.