JP2785366B2 - Cermet cutting tool - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cermet cutting tool by vacuum sintering.

[Conventional technology]

A calcination in which double carbonitrides of Ti and one or more transition metals selected from the group consisting of Zr, Hf, V, Nb, Ta, and Mo are bonded with a bonding metal composed of one or both of Co and Ni. Since the cermet cutting tool, which is a bonding metal, has superior wear resistance and superior welding resistance to steel, which is the work material, compared to cemented carbide in which WC, TiC, Tac, etc. are bonded with an iron group metal, It is widely used as a cutting tool instead of cemented carbide.

In order to manufacture this cermet, the green compact of the raw material powder is vacuum-sintered in the same manner as other cemented carbides, and during the cooling process after the completion of sintering, the bonding metal just below the surface moves to the surface layer. This causes a phenomenon in which the surface layer becomes a layer in which the concentration of the binding metal is higher than that of the other portions, and a hardened layer in which the concentration of the binding metal is lower up to about 50 μm directly below the inner portion. Since the hardened layer has a lower concentration of the binding metal than the inside, the hardened layer is 10 to 50% harder than the inside and has excellent wear resistance. However, the thinner the concentration of the binding metal, the lower the fracture resistance. It is sufficient to grind and remove from the surface layer to the hardened layer. In particular, nitride is harder to grind than carbide, and it takes time to grind.

Sintered cutting tools include a P-class tool whose surface is ground to improve tool accuracy, and an M-class tool that is not ground at all or partially ground after being sintered. Grinding costs for sintered cutting tools account for a large proportion of manufacturing costs.
There is a strong demand in the market for inexpensive M-class tools that do not perform grinding.

For this reason, in order to manufacture a cermet cutting tool that can be used without sintering without a hardened layer, for example, after sintering is completed, cooling is performed at a cooling rate of 200 to 300 ° C min, and carbon, nitrogen in a cooling atmosphere is used. Alternatively, it is common practice to prevent the formation of a hardened layer by maintaining the oxygen potential at a predetermined value or more. However, in order to carry out such a production method, expensive high-purity CO ₂ + CO, H ₂ + CO ₂ , H ₂
Since it requires + CH ₄ , N gas, etc., and it is necessary to modify the cemented carbide sintering furnace so that the product can be rapidly cooled, there is a problem that the production cost is greatly increased.

[Problems to be solved by the invention]

An object of the present invention is to provide an inexpensive cermet cutting tool excellent in fracture resistance by solving the above-mentioned problems.

[Means for solving the problem]

The present invention provides a double carbonitride of one or more transition metals selected from the group consisting of Ti and W and Zr, Hf, V, Nb, Ta, and Mo, Co, Ni
A sintered alloy bonded with a bonding metal consisting of one or both of the following, wherein the surface layer has a higher concentration of the bonding metal on the surface than the other part, and the concentration of the bonding metal below the surface layer is lower than the inside In a cermet cutting tool having a hardened layer, a cermet cutting tool in which a surface layer and a hardened layer are removed on a rake surface with a width of 0.05 to 1 mm from a cutting edge and serving as a means for solving the problem.

[Action]

According to a detailed examination of the occurrence of chipping in the cermet cutting tool, it is very common that chipping occurs during intermittent cutting, and chipping caused by intermittent cutting causes cracks on the rake face side, which leads to chipping. Therefore, only the rake face of the cermet cutting tool needs to have improved fracture resistance.

In addition, in the case of chip grinding, the polishing of the side face is extremely costly, but the grinding of the rake face is easy and inexpensive.

Therefore, the surface produced at low cost by vacuum sintering has a surface layer having a higher concentration of the binding metal than other portions, and a hardened layer below the surface layer having a lower concentration of the binding metal than the inside. If the above-mentioned surface layer and only the hardened layer under the rake face are removed by grinding in the cermet cutting tool, a cermet cutting tool whose cutting edge has fracture resistance can be provided at low cost.

Also, the rake face part involved in cutting is almost equal to the length of the feed during cutting, so 0.05-
The most economical solution can be provided by removing the surface layer and the hardened layer for the 1 mm portion.

This removal processing may be performed by honing the cutting edge from the rake face side using a very common brush magnet for round honing of the cutting edge.

〔Example〕

Example 1 10 wt% of Co and 5 wt% of Ni were added to (Ti Ta W) (CN) powder, pulverized and mixed using an alcohol as a solvent with an attritor, and then dried and granulated using a spray drier. did. This powder is molded in a mold using a pressure of 1.5 ton / cm ² in TNMG.
It was molded into the shape of model number 160408R-UM. This green compact was sintered in a normal vacuum furnace at 1450 ° C. for 1 hour and vacuum cooled. Only the rake face of this sample is on one side using a surface grinder.
The surface layer and the hardened layer were removed by polishing each 0.1 mm.

 This sample was subjected to a cutting test under the following conditions.

Workpiece SCM435 grooved member (H _D = 250) holder MTJNR2525-33 cutting speed 100 m / min feed Ri 0.20 mm / rev cuts 1.0mm Cutting time 30 seconds results of the cutting test, nine cutting edge sample 100 cutting edge Lost. For comparison, for the sample polished only on the bottom, 8 out of 100 cutting edges
Two cutting edges were missing.

Example 2 A chip having a model number of TNMG160408N-UG was prepared in exactly the same manner as in Example 1, and the upper and lower surfaces were slightly polished 0.1 mm on each side (the cutting edge portion was not polished). Rake face only from cutting edge
The surface layer and the hardened layer were removed by polishing with a width of 0.12 mm (naturally, the surface layer of about 0.04 mm from the cutting edge was also removed on the flank side).

When a cutting test was performed on this sample under the same conditions as in Example 1, 12 out of 100 cutting edges were missing.

Polishing width on rake face is set to 0.03 mm for comparison
94 out of 100 cutting edges were missing.

〔The invention's effect〕

According to the present invention, an inexpensive cermet cutting tool having excellent fracture resistance can be provided.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B23B 27/14

Claims (1)

(57) [Claims] 1. A double carbonitride of at least one transition metal selected from the group consisting of Ti, W and Zr, Hf, V, Nb, Ta, Mo.
A sintered alloy bonded with a bonding metal consisting of one or both of Co and Ni, with a surface layer having a higher concentration of the bonding metal on the surface than other parts, and an internal concentration of the bonding metal below the surface layer. A cermet cutting tool having a thinner hardened layer, wherein the surface layer and the hardened layer are removed on the rake face with a width of 0.05 to 1 mm from the cutting edge.