JPS5942067B2 - Tough tungsten carbide-based cemented carbide for cutting tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tungsten carbide (hereinafter referred to as WC) cemented carbide having excellent toughness and particularly suitable for use as a cutting tool.

Conventionally, titanium carbide (hereinafter referred to as Ti), which has high hardness and excellent welding resistance and oxidation resistance, has been added to WC-Co cemented carbide.
(hereinafter referred to as TaC), niobium carbide (hereinafter referred to as NbC), and vanadium carbide (hereinafter referred to as NbC).
One or two transition metal carbides such as (hereinafter referred to as VC)
A WCC cemented carbide has been proposed in which heat resistance and wear resistance are improved by adding more than one species.

When this conventional WCC cemented carbide is used as a cutting tool, especially for cutting steel, it has excellent crater wear resistance (wear resistance on the rake face of the cutting edge) and flank resistance against the high heat generated during cutting. Since it exhibits abrasion resistance (wear resistance on the flank surface of the cutting edge), its cutting life is further extended.

In this way, conventional WCC containing the above transition metal carbide
Although cemented carbide has excellent wear and heat resistance, the hard and brittle nature of the transition metal carbide reduces its strength, impact resistance, and thermal shock resistance. Currently, these properties do not show satisfactory cutting performance when used for high-speed cutting that requires toughness, high-feed cutting, deep-cut cutting, and other heavy-duty cutting.

This invention solves the above-mentioned problems with conventional WC-co type cemented carbides, and provides both properties of wear resistance, which are originally contradictory properties, as well as impact resistance and thermal shock resistance, We are proposing a WCC cemented carbide that has excellent cutting properties, and in terms of volume percentage (all figures below indicate capacity ratio), it contains Co: 4 to 13%, TiC, TaC, NbC, and VC. In a WC-based cemented carbide for cutting tools having a composition consisting of one or more of these: 10 to 60%, the remainder being WC and unavoidable impurities, the WC forming the dispersed phase is The average particle size of the solid solution carbide that forms the dispersed phase must be 0.7 μ or less and no particles with a particle size of 1 μ or less exist. It is characterized by providing excellent toughness (high strength, as well as excellent impact resistance and thermal shock resistance).

Therefore, the WCC cemented carbide of the present invention has a structure consisting of a dispersed phase of WC and solid solution carbide, and a binder phase of CO.

Next, in the WCC cemented carbide of the present invention, the reason why the composition range and the particle size of WC and solid solution carbide are limited as described above will be explained.

(a) C.

If the content is less than 4φ, the desired toughness (impact resistance) cannot be secured, while if the content exceeds 13 mm, the wear resistance will decrease. It has been designated as Section 13.

(b) TiC, TaC, NbC, and VC If the content is less than 10%, the desired excellent wear resistance and heat resistance cannot be ensured, while if the content exceeds 60%, the toughness deteriorates. Since it causes deterioration, its content is set at 10 to 60%.

(C) Particle size of solid solution carbides Solid solution carbides include TiC, TaC, NbC, and VC.
or one or more of these transition metal carbides and WC, and the extremely hard properties of these solid solution carbides give the alloy excellent wear resistance and heat resistance. However, if the average particle size exceeds 0.7, the effect of fine dispersion will not be fully exerted, and the toughness will deteriorate, and if there are particles with a particle size exceeding 1μ, this will cause fracture. Since this becomes a starting point and causes a decrease in strength, the average particle size must be 0.7μ or less, and there must be no particle size exceeding 1μ.

(d) Particle size of WC Even if the average particle size and maximum particle size of the solid solution carbide are limited as described above, there are cases where the average particle size of WC exceeds 3 μ and the maximum particle size exceeds 5 μ. If this happens, the toughness improvement effect of the above-mentioned fine solid solution carbide will be impaired, so the average particle size should be set to 3μ or less,
In addition, it must be ensured that particles with a particle size exceeding 5 μm do not exist.

Next, a WCC cemented carbide example of the present invention will be specifically explained.

Examples Carbide powder and Co powder having the average particle diameters shown in Table 1 were prepared, and these raw material powders were
After blending with the composition shown in the table and pulverizing and mixing in a ball mill, it was formed into a green compact at a pressure of 1.5 ton/i, and then baked in a vacuum at a temperature of 1400°C for 1 hour. By bonding, the cemented carbide 1 of the present invention has substantially the same composition as the blended composition, and the dispersed phase is composed of WC and solid solution carbide, while the binder phase is composed of Co.
-8 and comparative cemented carbides 1-3 were produced, respectively.

In addition, in Comparative Cemented Carbide Alloys 1 to 3, the particle size of WC and/or solid solution carbide is outside the range of the present invention.

]3 Next, the average grain size and maximum grain size of WC and solid solution carbide were measured for the resulting cemented carbides 1 to 8 of the present invention and comparative cemented carbide 1 to 3, and the Rockwell hardness A was measured. scale) and transverse rupture strength, and from this, 5NP432 (chamfer honing:
A cutting tip with a shape of 0.16 mm (25°) was cut out, work material: SNCM-8 (hardness: HB270), cutting speed: 150 m/min.

Feed: 0.45 mm/rev, depth of cut: 1.
High-speed continuous cutting test under the conditions of 5mm1 Cutting time: 10m1111, Work material: SNCM-8 (hardness: HB220), Cutting speed: 120m/m chips, Feed: 0.3mm/rev, Depth of cut: 3rIL1rt1 Cutting time: 2m1n.

In the above high-speed continuous cutting test, the flank wear width and rake face wear depth of the cutting edge were measured. The number of cutting edges with defects on the cutting edge was measured.

The results of these measurements are shown in Table 2.

From the results shown in Table 2, the cemented carbide alloys 1 to 8 of the present invention are:
All of them have high hardness and toughness, and show excellent wear resistance and impact resistance (thermal shock resistance) in all cutting tests, whereas Comparative Cemented Carbide 1 to 3 have conventional WC
It is clear that all of them, including the comparative cemented carbide equivalent to C cemented carbide, are inferior in toughness and therefore do not exhibit sufficiently satisfactory cutting performance in any of the cutting tests.

As mentioned above, the WCC cemented carbide of the present invention has excellent toughness and high hardness, and also has wear resistance, impact resistance,
Since it has excellent thermal shock resistance, it exhibits excellent cutting performance especially when used as a cutting tool for high-speed cutting or heavy cutting that requires these properties.

Claims (1)

[Claims] I Co: 4 to 13%, one or more of titanium carbide, tanker carbide, niobium carbide, and vanadium carbide: 10 to 60%, tungsten carbide and unavoidable impurities: the remainder, from In a tungsten carbide-based cemented carbide having a composition (volume % or more), the tungsten carbide serving as the dispersed phase has an average particle size of 3μ or less, and there is no grain size exceeding 5μ, and the tungsten carbide serving as the dispersed phase A tough tungsten carbide-based cemented carbide for cutting tools, characterized in that the solid solution carbide has an average grain size of 0.7 μm or less and no grain size exceeding 1 μm exists.