JPS6246513B2 - - Google Patents

Description

[Detailed description of the invention]

This invention has excellent abrasion resistance, thermal shock resistance,
The present invention relates to a sialon-based ceramic material that has high-temperature strength and exhibits excellent cutting performance when used as a cutting tool for high-speed cutting of steel and cast iron, which especially require these properties. In recent years, various research and development efforts have been made to enable high-speed cutting of steel and cast iron, and in particular, the transition to high-speed cutting of these work materials has been attempted from the standpoint of both increasing the rigidity of machine tools and improving cutting tool materials. This goal is steadily being achieved, and one of the current goals is stable cutting at high cutting speeds of 300 to 600 m/min. The above-mentioned high cutting speed of 300 to 600 m/min is achieved by using aluminum oxide, which exhibits excellent oxidation resistance against the heat generated during high-speed cutting, has low chemical reactivity with Fe, and has a small coefficient of friction. Al ₂ O ₃ containing (hereinafter referred to as Al ₂ O ₃ ) as the main component
This was established on the premise that ceramic materials would be used as cutting tools, and that this could be achieved by improving machine tools to enable high-speed cutting. However, since the Al ₂ O ₃ ceramic materials mentioned above do not have sufficient thermal shock resistance and mechanical strength at high temperatures, they are used as cutting tools, especially when cutting steel at high speeds of 300 to 600 m/min. At present, when used at high speeds, stable cutting performance cannot be achieved due to the fact that machine tools have not yet been sufficiently improved. On the other hand, it has a small coefficient of thermal expansion, has excellent thermal shock resistance, and has excellent mechanical strength at high temperatures, and has a composition in which Si is replaced with Al and N is replaced with O in the Si ₃ N ₄ lattice. formula:
A ceramic material consisting of sialon (also referred to as β or β' sialon) represented by Si _6-Z Al _Z O _Z N _8-Z (where O
_Y2O3 ), magnesium oxide (hereinafter referred to _as MgO), silicon oxide (hereinafter referred to as _SiO2 ), aluminum nitride (hereinafter referred to as AlN), titanium oxide (hereinafter referred to as
_TiO2 ), zirconium oxide (hereinafter referred to as _ZrO2 ), and hafnium oxide (hereinafter referred to as _HfO2 )
Attempts have also been made to use sialon-based ceramic materials containing 1 to 30% by weight of one or more of the above as cutting tools for high-speed cutting of steel and cast iron. Ceramic materials have high reactivity with Fe, which causes severe wear, especially during high-speed cutting of steel.
As a cutting tool, it has extremely low versatility. Therefore, from the above-mentioned viewpoints, the present inventors have discovered that although the tool has excellent thermal shock resistance and high-temperature strength, when used as a cutting tool especially for high-speed cutting of steel, it suffers from severe wear and cannot be put to practical use. As a result of focusing on conventional sialon ceramic materials and conducting research to impart excellent wear resistance to them, we found that Ti
and W composite carbonitride solid solution (hereinafter referred to as (Ti,W)CN
), the Sialon type has excellent wear resistance and toughness while retaining the excellent thermal shock resistance and high temperature strength provided by Sialon. They have found that when ceramic materials are used as cutting tools, they exhibit excellent cutting performance over a long period of time, not only in cast iron but also in high-speed cutting of steel. Therefore, this invention was made based on the above knowledge, and contains (Ti, W)CN: 10 to 70% by weight, and further contains Y ₂ O ₃ as necessary. , MgO, SiO ₂ , AlN, TiO ₂ , ZrO ₂ , and HfO ₂ (including AlN component, but other components are metal oxides, so these are collectively referred to as metal oxides hereafter). 1 type or 2 or more types: 1
~30%, with the remainder consisting of Sialon and unavoidable impurities.It has excellent wear resistance, thermal shock resistance, high temperature strength, and toughness, especially for high-speed cutting of steel and cast iron where these properties are required. The sialon ceramic material is characterized by its excellent cutting performance over a long period of time when used as a cutting tool. Next, the reason for limiting the component composition range as described above in the sialon ceramic material of the present invention will be explained. (a) (Ti, W)CN This component exists in a ceramic material in the form of a discontinuous phase or a continuous phase, and has the effect of imparting excellent wear resistance and toughness to the ceramic material. If its content is less than 10%, the desired wear resistance and toughness cannot be achieved;
Since the thermal shock resistance of the ceramic material deteriorates if the content exceeds 10% to 70%. Note that this (Ti, W)CN component is
It has a two-phase structure consisting of a carbonitride phase with a high proportion of Ti and a metal phase whose main component is W, and is expressed by the composition formula: (Ti _x , W _1-x )C _y N _z If 0.2≦x≦0.7, 0.05≦y≦0.70, 0.15≦z≦, respectively
0.70, 0.3≦x+y≦0.85 is desirable. In other words, if the value of x is less than 0.2, the amount of carbonitride phase whose main component is Ti is too small to ensure the desired excellent wear resistance.
If the x value exceeds 0.7, the amount of the metal phase containing W as a main component will be too small, resulting in a decrease in toughness, so the x value is set to 0.3 to 0.7. Furthermore, when the y value is less than 0.05, the formation of carbonitride phase is small and the nitride phase appears, deteriorating the wear resistance. On the other hand, when the y value exceeds 0.7, the carbide phase tends to be formed. The y value was set to 0.05 to 0.70 since this may cause toughness deterioration. Regarding the value of z, nitrogen has the effect of reducing the particle size of the carbonitride phase and suppressing the reaction with the workpiece material to improve wear resistance, so if the value is less than 0.15, carbonitriding will occur. The particle size of the physical phase becomes coarser and a carbide phase is also formed, resulting in a decrease in toughness.On the other hand, it is impossible for the z value to exceed 0.70, since the upper limit of the x value is 0.70. 0.15~ from point
Set to 0.70. Furthermore, if the value of x+y is less than 0.3, the amount of carbonitride phase is too small to ensure the desired wear resistance, while if the value of x+y exceeds 0.85, conversely, the amount of metal phase is too small to achieve the desired wear resistance. Since it is not possible to ensure the toughness of
It should be between 0.30 and 0.85. (b) Metal oxides These components have the effect of improving sinterability, making it possible to produce dense ceramic materials even by ordinary sintering methods, and thereby further improving toughness and strength. , is included as necessary when these characteristics are required, but the content is 1%
If it is less than the desired effect, the desired effect cannot be obtained;
If the content exceeds 30%, wear resistance deteriorates, so the content was set at 1 to 30%. (c) Unavoidable impurities Unavoidable impurities include Fe, Ca, Na, Co, Ni,
Contains one or more of Mn, Cr, etc., but the total amount of these unavoidable impurities is 5.
%, it will not have any adverse effect on the properties of the ceramic material. Furthermore, the ceramic material of the present invention has a composition formula formed by solid solution preparation of Si ₃ N ₄ powder, Al ₂ O ₃ powder, and AlN powder as raw material powders:
Si _6-z Al _z O _z N _8-z (however, O<z≦4.3) SiAlON powder, for the purpose of forming SiAlON during sintering, Si ₃ N ₄ which is the constituent powder of SiAlON
powder, Al ₂ O ₃ powder, and AlN powder, as well as various compositions (compositional formula: Ti _x , W _1-x )C _y N _z x, y,
and different values of z) with (Ti,
W) Prepare CN powder and various metal oxide powders, mix these raw material powders to a predetermined composition, mix thoroughly using a ball mill or vibration mill, and then press using a hydrostatic press or mechanical press. The purpose is to form the green compact into a green compact, then to sinter the green compact in vacuum or in an atmospheric gas, or to hot press it, and if necessary, to more reliably densify it after sintering. It can be manufactured by applying hot isostatic pressing (HIP) treatment. Next, the ceramic material of the present invention will be specifically explained using examples. Example First, TiC powder with an average particle size of 1.5 μm, TiN powder with an average particle size of 1.5 μm, and TiN powder with an average particle size of 1.5 μm are all commercially available.
Prepare 1.0 μm W powder, mix these powders into a predetermined composition, dry mix them, and then apply pressure:
In a nitrogen atmosphere of 5.0 mmHg, heat and hold at a temperature of 1500°C to solidify, coarsely crush after cooling, and then crush in a ball mill, each of the first
Composition shown in the table and average particle size for each:
Seven types of (Ti, W)CN powders with a diameter of 1.0 μm were prepared. Similarly, both commercially available average particle size: 1.3
Si ₃ N ₄ powder with a diameter of 0.7 μm, Al ₂ O ₃ powder with a diameter of 1.5 μm, and AlN powder with a diameter of 1.5 μm were prepared, these powders were blended into a predetermined composition, and after dry mixing, the pressure was 760 mmHg. In a nitrogen atmosphere, temperature:
It is heated and maintained at 1550℃ to form a solid solution, and after cooling, it is coarsely crushed.
By subsequent grinding, the composition formula:
A SiAlON powder having an average particle size of 1.0 μm and having Si ₃ Al ₃ O ₃ N ₅ was prepared. Next, the above-mentioned various (Ti, W) CN powders and Sialon powders were mixed with separately prepared Y ₂ O ₃ powder, MgO powder, and MgO powder each having an average particle size of 0.8 μm.
It was used as a raw material powder together with SiO ₂ powder, AlN powder, TiO ₂ powder, ZrO ₂ powder, and HfO ₂ powder, and these raw material powders were blended into the composition shown in Table 1 and placed in an Al ₂ O ₃ ball mill. After wet mixing for 48 hours, drying, and hot-pressing using a graphite mold at a temperature of 1550°C for 20 minutes, the ceramic of the present invention having substantially the same composition as the blended composition was obtained. Materials 1 to 10 and comparative ceramic material 1 not containing (Ti, W)CN
were manufactured respectively. In addition, instead of the above-mentioned hot press method, the mixed powder is molded into a green compact using a mechanical press at a pressure of 1 ton/ ^cm2 , and the green compact is heated in a nitrogen atmosphere at a temperature of 1600 to 1750°C. The ceramic material of the present invention was produced under the same manufacturing conditions except that a normal sintering method consisting of sintering under conditions of holding for 2 hours was applied.

[Table] Comparative ceramic materials 11 to 21 and Comparative Ceramic Material 2, which also does not contain (Ti, W)CN, were manufactured. Next, the Vickers hardness and transverse rupture strength of the resulting ceramic materials 1 to 21 of the present invention and comparative ceramic materials 1 and 2 were measured, and a cutting chip of the SNGN432 type according to the CIS standard was formed from the results. Work material: SNCM-8 (hardness: H _B
220), Cutting speed: 300m/min, Depth of cut: 2mm,
Steel high-speed continuous cutting test under the conditions of feed: 0.45 mm/rev., work material: FC-25 (hardness: H _B 180), cutting speed: 400 m/min, depth of cut: 2 mm, feed:
A cast iron high-speed continuous cutting test was conducted under the condition of 0.45 mm/rev., and the life time was measured based on the flank wear width of the cutting edge: 0.4 mm. These measurement results are also shown in Table 1. From the results shown in Table 1, ceramic materials 1 to 21 of the present invention all have excellent wear resistance, thermal shock resistance, and high temperature strength, and therefore exhibit long cutting life in high-speed cutting of steel and cast iron. That is clear. On the other hand, (Ti,W)CN
Comparative ceramic material 1, which does not contain components, that is, corresponds to conventional sialon ceramic materials,
Although No. 2 has thermal shock resistance and high-temperature strength, it has poor wear resistance, so its cutting life is extremely short. As mentioned above, the sialon ceramic material of the present invention has excellent wear resistance, thermal shock resistance, and high-temperature strength, so it can be used not only for high-speed cutting of steel, which especially requires these properties.
When used as a cutting tool for high-speed cutting of cast iron,
It exhibits excellent cutting performance over an extremely long period of time.

Claims (1)

[Claims] 1. A sialon-based ceramic material for a cutting tool, characterized in that it contains 10 to 70% by weight of a composite carbonitride solid solution of Ti and W, with the remainder consisting of sialon and unavoidable impurities. 2 Composite carbonitride solid solution of Ti and W: Contains 10 to 70% by weight, and further contains one or two of yttrium oxide, magnesium oxide, silicon oxide, aluminum nitride, titanium oxide, zirconium oxide, and hafnium oxide. A sialon-based ceramic material for a cutting tool, characterized in that it contains 1 to 30% by weight of sialon or more, with the remainder consisting of sialon and unavoidable impurities.