JPH0777688B2 - Cermet drill with excellent fracture resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has excellent fracture resistance, excellent wear resistance and welding resistance, and in particular, high surface finish accuracy can be obtained even in high feed cutting. And a cermet drill that has an extremely long service life.

[Conventional technology]

Conventionally, as a drill, generally, for example, a solid drill shown in a front view (a) and a front view (b) in FIG. 1 is known, and these drills are made of high-speed steel or tungsten carbide (hereinafter Manufactured from base cemented carbide.

[Problems to be solved by the invention]

However, when these drills are used for high-feed cutting, for example, high-speed steel drills show only a very short service life due to lack of wear resistance, and WC-based cemented carbide drills Although it has sufficient wear resistance, it has a problem with the welding resistance to the work material, so that the accuracy of the finished surface deteriorates in a relatively short time and only a short service life is exhibited.

[Means for solving problems]

Therefore, from the viewpoints described above, the inventors of the present invention have conducted research to develop a drill that exhibits excellent cutting performance even in high-feed cutting over a long period of time. ,% Represents weight%), and one or more of carbides of W, Mo, Ta, and Nb (hereinafter, respectively represented by WC, Mo ₂ C, TaC, and NbC) as a hard dispersed phase forming component: 8 ~ 20%, Co and / or Ni as binder phase forming component: 20 to 26%, Nitride with carbide of Ti as hard disperse phase forming component, or carbonitride ketane (hereinafter referred to as TiC, TiN, TiCN) : rest, a composition, as well as the hardness: Rockwell hardness a scale (H _R a) is less than 88 to 91, an average particle diameter of the hard dispersion phase: 0.5 to 1 [mu] m, when a cermet comprising having, this cermet Is
Hardness of ordinary cermet: H _{R A} 91.5 or more and average particle size of hard dispersed phase: 2 μm or more, relatively low hardness and composed of fine hard dispersed phase Therefore, the cermet drill of this result shows excellent wear resistance and welding resistance without causing defects even when it is used for high feed cutting, and exerts a high finished area accuracy for a remarkably long time. That is the result of the research.

The present invention was made based on the above-mentioned research results, and the reasons why the compounding composition, hardness, and average particle diameter of the hard dispersed phase are limited as described above will be described below.

(1) The composition of WC, Mo ₂ C, TaC, and NbC are all TiC and Ti during sintering.
Compound carbonitride as a hard dispersed phase by reacting with N, or TiCN, that is, (Ti, M) CN (however,
M forms one or more of W, Mo, Ta, and Nb), improves the thermal shock resistance of the hard dispersed phase, and thus suppresses the occurrence of cracks, and prevents the occurrence of chipping due to these cracks. Although it has a function of preventing, if the proportion is less than 8%, a hard dispersed phase having desired excellent thermal shock resistance cannot be formed, while if the proportion exceeds 20%, the hardness of the hard dispersed phase becomes high. Since it will decrease, the ratio is set to 8 to 20%.

Further, Co and Ni have the effects of improving the sinterability and forming the binder phase to improve the strength, but their proportion is
If it is less than 20%, the desired strength-improving effect cannot be obtained, and the hardness becomes H _R A91 or higher, and as a result, defects tend to occur, while if the ratio exceeds 26%, H _R A becomes 88. Since the above hardness cannot be ensured and the wear resistance is deteriorated, the ratio is set to 20 to 26%.

(2) Hardness If the hardness is less than H _R A88, the desired wear resistance cannot be secured, while if the hardness is more than H _R A91, the fracture resistance tends to decrease. Hardness H _R A88 ~ 91
Specified as less than.

(3) Average particle size of hard dispersed phase Cermet having an average particle size of less than 0.5 μm is difficult to manufacture by the current technology, while if the average particle size exceeds 1 μm, thermal shock resistance tends to decrease. Appearing, cracks are likely to occur, chipping occurs due to the cracks, and wear is promoted. Therefore, the average particle size is set to 0.5 to 1 μm.

〔Example〕

Next, the cermet drill of the present invention will be specifically described with reference to Examples.

As raw material powders, TiC powder, Tin powder, TiCN powder, WC powder, Mo ₂ C powder, TaC powder, and NbC powder, each having a predetermined average particle size within the range of 0.5 to 1.7 μm, and all 1.5 μm Prepare Co powder and Ni powder having an average particle size of, and mix these raw material powders with the compounding compositions shown in Tables 1 and 2, respectively, mix under normal conditions, press-mold,
Sintered to form a cermet material with dimensions of outer diameter: 11.5 mm x length: 95 mm, and from this cermet material, outer diameter: 10.5 m
m × length: The cermet-made drill of the present invention as a solid drill by polishing to a dimension of 89 mm (hereinafter,
Inventive drill) 1-9 and comparative shark TT drills (hereinafter, referred to as comparative drills) 1 to 7 were manufactured.

In addition, all the comparative drills 1 to 7 have a blended composition, hardness,
And one of the average particle sizes of the hard dispersed phase (second, third
(Marked with * in the table) is outside the scope of this invention.

For comparison purposes, high-speed steel (JIS SKH-55) drills and WC-based cemented carbide drills were prepared as conventional drills 1 and 2.

Then, for the drills 1 to 9 of the present invention, the comparative drills 1 to 7, and the conventional drills 1 and 2 obtained as a result, while measuring the average particle size of the hard dispersed phase of the cermet constituting the drills, and the hardness, material of workpiece: carbon steel (S45C, hardness: H _B 160), the workpiece shape: plate thickness 15 mm, cutting speed: 60 m / min, feed: 0.2 m / rev, format:. wet, High feed piercing cutting test of steel plate material under the condition of 3500
The wear depth of the front edge of the drill and the margin after the drilling was measured. Table 3 shows the progress of these measurements.

〔The invention's effect〕

From the results shown in Tables 1 to 3, the present drills 1 to 9
It is clear that each of them has excellent cutting performance over the conventional drills 1 and 2 over a long period of time.

On the other hand, as seen in comparative drills 1 to 7,
It is clear that if either the hardness or the average particle size of the hard dispersed phase deviates from the scope of the present invention, the desired cutting characteristics are not exhibited.

As described above, the cermet drill of the present invention has excellent fracture resistance, and is composed of a cermet that is also excellent in wear resistance and welding resistance, so that high surface finish accuracy is achieved even in high feed cutting. It has industrially useful properties such as exhibiting remarkably long term.

[Brief description of drawings]

1A and 1B are a front view and a front view of a solid drill as an example of a drill.

Claims (1)

[Claims] 1. At least 1% by weight of carbides of W, Mo, Ta and Nb as hard dispersed phase forming components: 8 to 20%, and Co and / or Ni: 20 to 20% as binder phase forming components. 26%, Ti carbide and nitride as hard disperse phase forming component, or carbonitride: balance, compounding composition, and hardness: Rockwell hardness (A scale) 88 to less than 91, hard disperse phase A cermet-made drill with excellent fracture resistance, which is characterized by comprising a cermet having an average particle diameter of 0.5 to 1 μm.