JPS5813512B2 - Fukugo Ceramitsukukogu - Google Patents

Description

[Detailed Description of the Invention] So-called ceramic tools mainly composed of Al2O3 have superior mechanical properties at high temperatures compared to cemented carbide mainly composed of WC, cemented carbide mainly composed of TiC, and so-called cermets. Because of this, it is used as a tool material for high-speed cutting.

The disadvantage of Al2O3 ceramics is that they are brittle.

Therefore, it has been used in areas where heavy loads are not applied, such as finishing machining.

However, with recent advances in machine tools and changes in the working environment, the loads expected of ceramic tools are becoming more severe.

In other words, an increase in cutting speed, an increase in cutting cross-sectional area, and an increase in cutting edge temperature due to an increase in the use of water-soluble cutting oil.
There is a significant increase in stress and thermal shock on the cutting edge.

The current Al2O3-based ceramics have not been able to adequately meet these expected loads.

From this point of view, the present invention aims to provide a ceramic tool that can withstand even more severe loads.

The first feature of the present invention is that ceramic and cemented carbide are composited in layers.

Cemented carbide has high rigidity, heat resistance, and thermal conductivity, and is ideal as a base for such composite chips.

Heat resistance is required for bonding the base and ceramic, so diffusion bonding is used, or copper solder or a solder material with a higher melting point is used.

In this case, if the difference in coefficient of thermal expansion between the ceramic and the cemented carbide is large, deformation or destruction due to excessive thermal stress may occur.

The second feature of the present invention is that Sialon is used as the ceramic.

Sialon has many desirable characteristics as a cutting tool, such as being resistant to thermal shock, having high oxidation resistance, and having excellent weldability to steel.

However, the more important reason for using Sialon is that its coefficient of thermal expansion is lower than that of cemented carbide.

The thermal expansion coefficient of Al2O3 is 7.8 x 10-6 and WC-C
It is larger than (4.5-7)×10-6 of o alloy.

Therefore, if bonded at high temperature, tensile stress will be generated in Al2O3 upon cooling, resulting in destruction of Al2O3.

Sialon, on the other hand, is Si6-0.75xAl0.
It varies depending on the value of x in 67xOxN8-x, but it is 2.4x
It is approximately equal to or less than that of Si3N4, which has a coefficient of thermal expansion value of 10-6.

Therefore, compressive stress is generated in the ceramic when it is cooled, and this is preferable as a tool because it suppresses the propagation of cracks.

A third feature of the present invention is that shape and dimensional limitations are placed on the composite chip.

Basically, the combination of the ceramic part and the cemented carbide is preferably layered.

You can decide whether to serve it on one side or as a sandwich depending on the purpose.

It is not preferable to cover the entire surface of the cemented carbide with ceramic.

It is optional to provide a portion of the layered structure with unevenness in order to strengthen the bond between the ceramic and the cemented carbide.

The thickness of the ceramic part is preferably 1 mm or less, and in terms of performance,
From the viewpoint of manufacturing technology, the preferred thickness is around 0.5 mm; if the thickness is 1 mm or more, the effect as a composite chip will no longer be seen.

If the thickness of the underlying cemented carbide is too thin, not only will it not play a reinforcing role in terms of strength, but the composite chip will bend when cooled after bonding with the ceramic, leaving compressive residual stress in the ceramic part. Contrary to this intention, tensile residual stress is generated on the upper surface of the ceramic portion, which is undesirable.

From this point of view, it is necessary that the thickness of the base cemented carbide is at least 3 mm or more.

Example 1 Al2O3 powder 20, Si3N4 powder 79.5, Y2O
After thoroughly mixing the three powders at a ratio of 0.5 to 178
A sintered body of Sialon was prepared by hot pressing at 0° C. for 30 minutes at a load of 200 kg/cm 2 .

From this sintered body, 14×14× was cut using a diamond cutting machine.
A 0.5 mm thin section was cut out.

The above-mentioned Sia
Filled with a powder made by mixing lon raw powder and WC-Co at a weight ratio of 50':50, the whole was stacked and heated to 1500℃.
Hot pressing was carried out for 10 minutes under a load of 200 kg/cm2.

After cooling, this composite is 12.7 x 12.7 mm x 4.8 m.
It was ground into the shape of m.

Using this chip, SCM3 (11s=40) was cut for 15 minutes at a cutting speed of 350 m/min, depth of cut of 2 mm, and feed rate of 0.36 mm/rotation while applying water-soluble cutting oil.

The flank wear amount at this time was 0.3 mm. On the other hand, the ordinary Al2O3 fired chip broke in 3 minutes and became uncuttable.

In this respect, the present composite chip was found to have excellent thermal shock resistance.

Example 2 A fired body of Sialon was produced in the same manner as in Example 1 using a ratio of 45 Al2O3 powder, 54 Si3N4 powder, and 1 MgO powder.

From this sintered body, 14×14×O. A 2 mm thin section was cut out.

This thin piece was coated with the above mixed powder as a base, and further WC-10%C
o Layered on powder at 1500℃ x 20 minutes, 200kg/cm
2 pressure firing was performed.

When this composite was observed after cooling, it was found that the thickness of the Sialon layer was about 0.5 mm, and there was a continuous double-layered layer below which was composed mainly of WC-10% Co.

This composite was ground into a shape of 12.7 x 12.7 x 4.8 mm.

Using this tip, cut SK5 (Hs=38) at a cutting speed of 3
A continuous cutting test was conducted at 70 m/mm, depth of cut of 2 mm, and feed rate of 0.40 mm/rotation while applying water-soluble cutting oil, and the results shown in Table 1 were obtained.

The superiority of the thermal shock resistance of the invented product was proven.

Claims (1)

[Claims] 1 Si6-0.75xAl0.67 with a thickness of 1 mm or less
A ceramic whose maximum value of x is 6 in xOxN8-x,
A composite ceramic tool characterized by being formed by joining cemented carbide with a thickness of 3 mm or more in layers.