JPH0711049B2 - Cemented carbide and manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to improvement of P-based cemented carbide. In particular, it relates to expanding the range of applications of rolling tools.

[Prior Art] A cemented carbide having a hard phase composed of tungsten carbide and a B-1 type solid solution has been put to practical use in various applications because of its excellent wear resistance and impact resistance. Especially, in WC-TiC-Ta (Nb) C-Co system, T
The alloy to which a small amount of iN is added can be refined in the B-1 type solid solution phase as compared with the above cemented carbide by the addition of nitrogen, and is used for applications requiring higher toughness. Conventionally, B-
Type 1 solid solutions include binary or quaternary solid solutions (WTi)
C, (WTiTaNb) C, was used and is shown in the quasi-ternary phase diagram of WC-TiC-third hard material group (TaC NbC). It was used with a composition close to the solid solubility limit of the HCP phase in the FCC phase. This also has the effect of allowing the used WC to remain in the sintered body in its original state without causing a solid solution reaction, making it easier to adjust the particle size distribution. That is, the WC phase having a relatively coarse grain size is used to balance the performance such as mechanical impact and plastic deformation accompanying the refinement of the B-1 type solid solution by the coarse graining of WC.

[Problems to be Solved by the Invention] As described above, the conventional P-based cemented carbide has a coarse grain size of 4 to 8 microns.
WC and a fine B-1 type solid solution having a size of 1 to 2 μm were bonded with Co, and the same was true when TiN was added.
However, due to the recent high-speed, high-efficiency cutting, problems such as chipping are likely to occur as a drawback of this series of alloys in that the wear resistance is insufficient and the cutting surface roughness is inferior to minute cutting.

[Means for Solving Problems] When the composition of the alloy is the same, the wear resistance of the alloy is determined by the composition of the B-1 type solid solution, and the wear resistance improves as the W content in the B-1 type solid solution decreases. . Further, the roughness of the cutting surface correlates with the grain size of the alloy, and is generally taken when relatively coarse grains are used, and a similar tendency has been confirmed for chipping in fine cutting. Therefore, it is necessary to reduce the W content in the B-1 type solid solution so that both WC and the B-1 type solid solution are refined and grain-sized to a certain extent.

As a result of various studies on a method of reducing the W content in the B-1 type solid solution to improve wear resistance, even if the method of adding Ti is changed, it will be in an equilibrium state due to diffusion during sintering and will be constant. When a nitride is added to the B-1 type solid solution, the solid solution of W can be suppressed and the composition of the B-1 type solid solution can be adjusted.
Particularly, as a nitride, TiN and TaN have a great effect. Further, the above-mentioned nitride is also effective in miniaturizing the B-1 type solid solution.

Although WC is adjusted by the average particle size of the starting material, the particle size distribution becomes a problem and it is difficult to make it uniform. Therefore, it is necessary to adjust the particle size finely with the solidification of WC in the B-1 type solid solution.
They found that the WC particles disappeared to make the particles uniform.

[Operation] As described above, according to the present invention, the hard phase 80 is composed of titanium carbide 6 to 11%, titanium nitride 1 to 10%, tantalum carbide and / or tantalum nitride and / or niobium carbide 6 to 12%, and the balance is tungsten carbide. ~ 95%, binder phase consisting of iron group metal 5
The average grain size in the sintered body of the cemented carbide consisting of ~ 20% (hereinafter referred to as weight percent) is the tungsten carbide phase (α
Phase) 1.5 micron or less, B-1 type solid solution (β phase) 2 micron or less, and the particle size adjustment is to make the particles fine and uniform by WC solid solution in the B-1 type solid solution. It is a characteristic method for producing a cemented carbide.

The composition of the cemented carbide according to the present invention is limited for the following reasons.

1) If the TiC content is less than 6%, the effect on crater resistance is small, and if it exceeds 12%, the toughness is significantly impaired.

2) The amount of TiN added is an essential additive that determines the Ti / W ratio in the B-1 type solid solution. If it is less than 1%, its effect is small, and if it exceeds 10%, the toughness is significantly impaired. ,
It was set to 1 to 10%.

3) The addition amount of TaC, TaN, and NbC is less than 6%, the effect of suppressing grain is small, and the addition amount of more than 12% has no significant effect.

4) The addition amount of the iron group metal is less than 5%, sufficient toughness cannot be obtained, and if it exceeds 20%, plastic deformation resistance and wear resistance are deteriorated.

5) The grain size of the WC phase was set to 1.5 microns or less because the cutting surface roughness deteriorates when the grain size of the sintered body exceeds 1.5 microns.

6) The grain size of the B-1 type solid solution phase is set to 2 μm or less because if the grain size in the sintered body exceeds 2 μm, it is a more brittle phase than the WC phase and the strength deteriorates and chipping easily occurs. However, 1.5 micron or less is desirable.

7) In the WC-TiC-TaC system, the WC solid solution in the B-1 type solid solution is almost WC / TiC = 70/30 regardless of the amount of TaC. However, when TiN is added to a part of this system, this ratio changes the W content, as shown in Fig. 2, resulting in a Ti-rich composition. This composition is almost constant regardless of the starting material. For example, when a WC / TiC solid solution is used, it becomes oversaturated from the equilibrium state, so WC precipitates during sintering, and WC, TiC
Absorbs WC when used alone or in an unsaturated state. In this state, when WC is coarse-grained, in order to measure the stability during sintering, it is easier to control the WC particle size by preparing and adjusting a solid solution called triple carbide or double carbide beforehand. It was However, when pulverizing WC, fine powder of WC produced by mixing or the like is taken into the B-1 type solid solution during sintering, and it is effective for achieving uniform grain size. Hereinafter, the present invention will be described in detail based on examples.

[Example] 71WC-10TiC-10TaC-9Co was compounded to have a composition. The raw materials used for blending were commercially available WC powders (average particle size 1.0 μm and
5.0 μm), TiC powder (1.0 μm), TiN powder (1.0 μm)
m), DC powder (WC / TiC = 70/30 1.5 μm), DC powder (WC / TiC = 50/50 1.0 μm), and a solid solution of WC-TiC-TiN using the above powder. did. WC / TiC solid solution
/ TiN = 6/3/1 WC / TiC / TiN = 4/4/2 were blended, dried, and subjected to solution treatment at 1600 ° C for 2 hours in N atmosphere to adjust the particle size, and the average particle size 0.8 A μm powder was prepared.

These powders were mixed in various ways as shown in Table 1. After the completion of the mixing, after drying, a throw away tip of TEE433 was press-molded, sintered at 1400 ° C. for 1 hr in vacuum, and then processed into a predetermined shape.

Further, in order to confirm changes in physical properties and microstructure, the chips were polished and wrapped, and then hardness and fracture toughness values were measured. The results are also shown together. The grain size was measured by observing the structure with an electron microscope and observing the photograph. The measurement results of Inventive Example 1 and Comparative Example 10 are that the invention 1 has an average particle size of the WC phase of 1.05 μm and the B-1 type solid solution is 0.91 μm, and Comparative Example 10 has an average particle size of the WC phase of 4.0 μm. The B-1 type solid solution was coarse, 2.5 μm. Furthermore, in order to confirm cutting performance, the following specifications were performed.

Cutting speed 150m / min Feed 0.08mm / blade Depth of cut 1.0mm Work material SUS304 Tip shape TEE433 Cutter shape φ63 3 blades Life standard VB = 0.2mm Cutting time (min) The results are also shown in Table 1. .

From the results shown in Table 1, the relationship between hardness and fracture toughness value varies to some extent depending on the difference in WC grain size, but in these cutting tests, the effect of grain size appears, and the comparative examples show chipping during the early to middle stages of use. However, in the example of the present invention, a longer life is achieved by normal wear. The roughness of the cutting surface is also good.

[Effects of the Invention] In P-based cemented carbide, the average grain size in the sintered body is adjusted to be 1.5 μm or less in the tungsten carbide phase (α phase) by adjusting the addition of a nitride in the sintered body and the manufacturing method.
We have developed a cemented carbide with excellent chipping resistance and wear resistance in micro-cutting, etc. by making the mold solid solution phase (β phase) finer than 1 micron.

[Brief description of drawings]

Figure 1 shows the quasi-ternary phase diagram of WC-TiC-TaC, and Figure 2 shows WC.
-TiCN-TaC quasi-ternary phase diagram is shown.

Claims (2)

[Claims] 1. Titanium carbide 6 to 11%, titanium nitride 1 to 10
%, Tantalum carbide and / or tantalum nitride and / or niobium carbide 6-12% remaining, hard phase 80-95% made of tungsten carbide, binder phase 5-20% (hereinafter weight percent) made of iron group metal A cemented carbide, characterized in that, in a hard alloy, the average grain size in a sintered body is a tungsten carbide phase (α phase) of 1.5 microns or less and a B-1 type solid solution (β phase) of 2 microns or less. 2. Titanium carbide 6 to 11%, titanium nitride 1 to 10
%, Tantalum carbide and / or tantalum nitride and / or niobium carbide 6 to 12% remaining, tungsten carbide hard phase 80 to 95%, iron group metal binder phase 5 to 20% (above weight percent) A method for producing a cemented carbide, characterized in that the grain size of the hard alloy is adjusted by WC solid solution in a B-1 type solid solution.