JPH1161316A - Cutting tool made of cemented carbide, excellent in breaking resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting tool made of cemented carbide, exhibiting superior machinability over along period and excellent in breaking resistance. SOLUTION: The cutting tool made of cemented carbide is constituted of a tungsten-carbide-base cemented carbide which has a composition consisting of, by weight, 5 to 16% of a binding phase composed essentially of Co, 5 to 40% of a first dispersed phase composed of a compound with NaCl type crystal structure, and the balance a second dispersed phase composed essentially of tungsten carbide with inevitable, impurities and in which the above second dispersed phase has a structure where superfine grains of Co alloy having <=100 nm grain size are dispersedly distributed in a WC matrix.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent chipping resistance, and therefore has a problem such as chipping or chipping (small chipping) of a cutting edge even when intermittent cutting of steel or the like is performed under high cutting or high feed conditions. The present invention relates to a cemented carbide cutting tool (hereinafter, referred to as a cemented carbide tool) that exhibits excellent cutting performance for a long time without generation.

[0002]

2. Description of the Related Art Conventionally, in general, a cemented carbide tool has a binder phase containing Co as a main component in% by weight (hereinafter,% means% by weight):
5 to 16%, a first dispersed phase composed of a NaCl-type crystal structure compound: 5 to 40%, the remainder being substantially composed of a second dispersed phase composed of tungsten carbide (hereinafter referred to as WC) and unavoidable impurities. Wherein the NaCl-type crystal structure compound is composed of a carbide, nitride, and carbonitride of a metal of Groups 4a, 5a, and 6a of the periodic table, and two kinds thereof. It is also well-known that the solid solution is composed of one or more of the above solid solutions. Further, it is also known that these carbide tools are used for continuous cutting and interrupted cutting of steel, cast iron, and the like. I have.

[0003]

On the other hand, in recent years, the performance of cutting machines has been remarkably improved, and there has been a strong demand for labor saving in cutting. Accordingly, cutting has been speeded up, and cutting conditions such as cutting and feeding have been required. However, when the above-mentioned conventional carbide tools are used for intermittent cutting, especially when cutting and feeding are increased, the cutting edge is liable to be chipped or chipped. At present, the service life is reached in a relatively short time.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above viewpoint, paying attention to the above-mentioned conventional carbide tools,
As a result of conducting research to improve the fracture resistance, in the production of conventional carbide tools, WC powder and Co powder, which have been used as raw material powders, are basically replaced by oxidized powders mixed at a predetermined ratio. Tungsten (hereinafter referred to as WO ₃ )
Distilled water in which, for example, cobalt nitrate as a Co source is dissolved is added as a solvent to the powder and the carbon powder, mixed and dried.
When a composite powder composed of WC and Co is produced as a raw material powder by performing a reduction treatment under the condition of holding for a minute and performing a carbonization process at a temperature of 1000 ° C. for 60 minutes in a hydrogen atmosphere, for example, as a raw material powder. The second dispersed phase of the dispersed phase of the cemented carbide constituting the cemented carbide tool is an alloy containing Co as a main component and having a particle size of 100 nm or less in a WC base material (hereinafter referred to as a Co-based alloy). ) Has a structure in which the ultrafine particles are dispersed and distributed, and as a result, the second dispersed phase has a particle size of 100 nm or less in the WC matrix.
In a cemented carbide cutting tool having a structure in which ultrafine particles of an o-based alloy are dispersed and distributed, compared to a conventional cemented carbide tool in which the cemented carbide has the same binder phase content, the cemented carbide has a binder phase between the dispersed phases. In addition to the fact that it becomes even finer including most of the existing binder phase, even when performing intermittent cutting under heavy cutting conditions such as high cutting and high feed, chipping and chipping etc. The research results showed that excellent cutting performance would be exhibited without any occurrence.

The present invention has been made based on the results of the above research, and has a binder phase containing Co as a main component:
16%, a first dispersed phase composed of a NaCl-type crystal structure compound: 5 to 40%, the remainder having a composition composed of a second dispersed phase mainly composed of WC and unavoidable impurities, and The disperse phase is characterized by a cemented carbide tool having excellent fracture resistance, comprising a cemented carbide having a structure in which ultrafine particles of a Co-based alloy having a particle size of 100 nm or less are dispersed and distributed on a WC substrate. Things.

In the cemented carbide tool of the present invention, the cemented carbide constituting the cemented carbide is set to have a binder phase content of 5 to 16%. If the content is less than 5%, the cemented carbide is required for a cemented carbide tool. The desired strength and toughness cannot be ensured, while if the content exceeds 16%, the abrasion resistance rapidly decreases, preferably from 8 to 12%. The first dispersed phase composed of a NaCl-type crystal structure compound is contained for the purpose of improving heat resistance and abrasion resistance. Therefore, if the content is less than 5%, the desired heat resistance can be obtained. On the other hand, if the content exceeds 40%, the strength, impact resistance, and thermal shock resistance all show a clear tendency to decrease. 5-40% content, desired Is properly are as defined and 10% to 25%. Further, the particle size and distribution density of the ultrafine particles dispersed and distributed in the second dispersed phase also containing WC as the main component are determined by the tungsten oxide powder and carbon It is controlled by adjusting the average particle size of the powder, and the conditions of the reduction treatment and the carbonization treatment.
When ultrafine particles exceeding nm are present, the hardness is reduced and abrasion resistance is inevitably reduced. Therefore, the particle size of the ultrafine particles is set to 100 nm or less.

[0007]

Next, the cemented carbide tool of the present invention will be specifically described with reference to examples. First, average particle size: 3.0
μm WO ₃ powder, 0.4 μm carbon powder, and a predetermined amount of cobalt nitrate [Co (NO ₃ ) ₂ .6] as a solvent.
H ₂ O] is dissolved in distilled water, and the WO ₃ powder, the carbon powder, and the solvent are charged into a ball mill at a predetermined mixing ratio, wet-mixed for 72 hours, dried, and then dried in a nitrogen atmosphere. The composition and the average particle size shown in Table 1 are obtained by performing a reduction treatment under the condition of holding at 1050 ° C. for 30 minutes and a subsequent carbonization treatment under the condition of holding at 1000 ° C. for 60 minutes in a hydrogen atmosphere. Composite powders A to F composed of WC and Co were produced as raw material powders.

Further, as raw material powders,
TiC having a predetermined average particle size in the range of ~ 4.0 µm
Powder, TaC powder, NbC powder, ZrC powder, (Ti,
W) C powder, (Ta, Nb) C powder, TiCN powder,
(Ti, W) CN powder, (Ti, W, Ta) CN powder,
And TiN powder were prepared, and these raw material powders were blended with each of the above composite powders A to F at a ratio shown in Table 2, wet-mixed and pulverized with a ball mill for 72 hours, dried, and then dried at 1 ton / cm. ^The compact is pressed into a green compact at a pressure of ^{2 and} the compact is sintered in vacuum at a predetermined temperature in the range of 1380 to 1480 ° C. for one hour to obtain a throwaway alloy of ISO standard SPGN120308. Carbide tools 1 to 15 of the present invention each having a chip shape were manufactured. Further, for the purpose of comparison, as the raw material powder, instead of the above composite powders A to F, an average particle diameter: 3.0 μm
Conventional WC tools 1 to 15 were respectively manufactured under the same conditions except that WC powder and Co powder of 1.2 μm were used, and these raw material powders were blended in the blending composition shown in Table 3.

The Rockwell hardness (A scale) of each of the resulting carbide tools was measured.
X-ray micro analyzer (EPMA)
The ratio (component composition) of the binder phase containing Co as the main component, the first dispersed phase composed of the NaCl-type crystal structure compound, and the second dispersed phase containing WC as the main component is measured, and the transmission is further performed. Using a scanning electron microscope (TEM), the presence or absence of ultrafine particles in the second dispersed phase is observed at a magnification of 350,000 times, and if ultrafine particles are present, the maximum particle size is measured and constituted. The main component was determined using an energy dispersive X-ray spectrometer (EDS).

[0010] Further, regarding the above-mentioned various carbide tools, work material: SCM440 (hardness: HB220), cutting speed: 120 m / min, feed: 0.3 mm / tooth, cutting depth: 2.5 mm, cutting time: 30 min., Wet wet high depth milling test of steel under the following conditions: Work material: square material of SNCM439 (hardness: HB270), cutting speed: 100 m / min, feed: 0.425 mm / rev, depth of cut: 3 0.0 mm, cutting time: 10 minutes, a dry high-cut intermittent cutting test of steel was performed, and the flank wear width of the cutting edge was measured. Tables 4 and 5 show the results of these measurements.
It was shown to.

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

[Table 3]

[0014]

[Table 4]

[0015]

[Table 5]

[0016]

From the results shown in Tables 4 and 5, the carbide tools 1 to 15 of the present invention show almost the same values in hardness and binder phase content as the conventional carbide tools 1 to 15, Particle size dispersed and distributed in the second dispersed phase mainly composed of WC: 100
The presence of ultra-fine particles made of a Co-based alloy having a diameter of 10 nm or less shows excellent fracture resistance despite high cutting depth in any interrupted cutting. It is clear that No. 15 causes chipping and chipping of the cutting edge due to lack of chipping resistance, resulting in a relatively short service life. As described above, the cemented carbide tool of the present invention has excellent fracture resistance,
Even when performing intermittent cutting under heavy cutting conditions such as high feed and high depth of cut as well as continuous cutting, the cutting edge will exhibit excellent cutting performance for a long time without chipping or chipping. Thus, it is possible to sufficiently and satisfactorily cope with labor saving and energy saving of cutting.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 29/02 C22C 29/02 A

Claims (1)

[Claims] A binder phase containing Co as a main component: 5 to 16%, and a first dispersed phase comprising a NaCl-type crystal structure compound: 5 to 4% by weight.
0%, the balance being composed of a second dispersed phase mainly composed of tungsten carbide and unavoidable impurities, and the second dispersed phase is formed on a base of tungsten carbide by 100n.
A cemented carbide cutting tool having excellent fracture resistance, comprising a tungsten carbide-based cemented carbide having a structure in which ultrafine particles of a Co-based alloy having a particle size of not more than m are dispersed and distributed.