JPH0633183A - Fine-grained sintered hard alloy - Google Patents

Abstract

PURPOSE:To obtain a fine-grained sintered hard alloy used for solid end mill- drill, etc. CONSTITUTION:The hard phase of WC-base sintered hard alloy is composed of 80-95wt.% WC and 0.05-2.5wt.% of one or >=2 kinds among TaC, VC and Cr3C2, and the binding phase as the balance is composed of one or >=2 kinds among iron group metals, the average grain size of the hard phase is regulated to 0.7-1.0mum. Further, if necessary, the grain inhibitors are also controlled to 0.5-2.5% in the case of TaC and Cr3C2 and to about 0.05-0.1% in the case of VC because the extent of inhibiting effect and the extent of deterioration in strength are different according to the additive quantities of the inhibitors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cemented carbide used for solid end mills, drills and the like.

[0002]

[Prior Art] Like solid end mills and drills,
A cutting tool with a sharp cutting edge improves the strength of the cemented carbide itself, and in order to make the cutting edge a sharp edge, the finer the WC particles that form a hard phase, the more the WC particles are used.
Further, in order to achieve further miniaturization, a material in which a grain suppressor is doped into a cemented carbide to suppress grain growth during sintering accompanying miniaturization is usually used.

As a grain suppressor, Japanese Patent Publication No. 62-5694 is available.
It is known that V and Cr shown in No. 4 and the like are added in combination, and TaC is further added, and W used for them is known.
The average particle size of C is about 0.4 to 0.5 μm, which is fine. Since the hardness of the cemented carbide depends on the average interparticle distance of the binder phase due to the fine particles, the smaller the average interparticle distance, the harder it becomes. Therefore, when comparing the hardnesses of cemented carbides with the same amount of binder phase, the finer the grain size of the carbide, the smaller the distance between the carbides, and accordingly the average distance between the grains of the binder phase also becomes smaller and becomes harder.

Therefore, if the carbide grain size is made finer, the amount of binder phase can be increased in order to obtain the same hardness level, and the toughness of the alloy can be remarkably improved accordingly. By making fine particles in this way, the amount of binder phase can be increased and the toughness is greatly improved.

[0005]

However, the addition of the grain suppressor tends to cause segregation at grain boundaries, particularly in the case of VC, and deteriorates the strength of Co as a binder phase.
Also, since the average interparticle distance of the hard phase becomes smaller with the miniaturization, the total amount of the binding metal is increased to compensate.
When the amount of the bound metal increases, the tool life becomes stable, but on the other hand, it is more effective to reduce the amount of Co in terms of welding resistance, cutting speed, rigidity (especially flapping) and the like.

[0005]

[Means for solving the problem] Especially, if the cutting speed is increased to obtain a high-quality finished surface, the finished surface deteriorates due to welding, or chips are entrained from the welding and the cutting edge causes chipping or chipping. And often became unusable. Therefore, the present invention has been achieved by selecting an appropriate grain size (grain suppressor) and a grain suppressor amount in order to maximize the rigidity that is characteristic of cemented carbide.

[0006]

Therefore, in the present invention, the hard phase is changed to WC80-9.
5% by weight and at least one or more of TaC, VC and Cr3C2 of 0.05 to 2.5% by weight,
WC in which the remaining binder phase consists of one or more iron group metals
In the base cemented carbide, the average grain size of the hard phase is 0.7 to 1.
The feature is that the thickness is 0 μm. More preferably, even in the above grain suppressor, the suppressing effect and the degree of strength deterioration differ depending on the addition amount of the suppressing agent.
0.5 to 2.5% for C and Cr3C2, 0.05 for VC
It is more effective to suppress the content to about 0.1%.

Next, the reason for limiting the numerical values will be described. WC
Is less than 80%, the desired wear resistance cannot be obtained.
If the content exceeds 5%, the fracture tends to occur rather than the deterioration in toughness, so the content is set to 80 to 95%. TaC, VC, Cr3
C2 is added to suppress grain growth during sintering, but if the content of C2 is less than 0.05%, the effect is small.
If it is contained in excess of 0, the toughness is significantly deteriorated, so that
It was set to 05 to 2.5%. If the binder phase is less than 5%, the toughness is deteriorated, and if it exceeds 30%, the wear resistance is extremely deteriorated, so the content is set to 5 to 30%.

Next, if the average particle size of the hard phase exceeds 1.0 μm, the hardness becomes too soft and wear resistance deteriorates.
Further, if the amount of the binder phase is reduced in order to prevent the decrease in hardness, the toughness deteriorates and desired characteristics cannot be obtained. On the other hand, if it is less than 0.7 μm, the starting material is restricted in order to obtain the particle size, and the amount of the grain suppressor to be added must be increased more than necessary, so the grain size is set to 0.7 to 1.0 μm. Hereinafter, specific examples will be described.

[0009]

EXAMPLE Commercially available WC powder (average particle size 0.8 μm), T
aC (1.5 μm), VC (1.0 μm), Cr3
Using C2 (1.0 μm in the same) and Co powder (1.0 μm in the same), the components shown in Table 1 were mixed, and wet mixing and pulverization were performed. After that, it is molded into the shape of a test piece, 1350-14
It was made by sintering at a temperature of 00 ° C and grinding. The surface is wrapped and finished to a mirror surface, the hardness (HRA) and the transverse rupture strength (kg / mm ² ) are measured, and the results are also shown in Table 1.

[0010]

[Table 1] Sample No. WC TaC Cr3C2 VC Co Grain size Hardness Bending strength 1 bal-1.0 0.1 10.0 0.75 92.5 375 2 bal 0.5 1.0 0.1 10.0 0.7 92.8 350 Mei 3 bal-0.5 0.2 10.0 0.8 92.3 360 Example 4 bal 0.5 0.5 0.2 10.0 0.8 92.1 380 5 bal 1.5 0.5 0.1 10.0 0.9 91.5 390 Ratio 6 bal-1.0 0.1 10.0 0.6 93.2 300 Comparison 7 bal 0.5 1.0 0.1 10.0 0.6 93.2 310 Example 8 bal-1.0 0.1 15.0 0.6 91.0 350

Next, a very general end mill for cemented carbide of sample number 1, blade diameter 10 mm, 2 blades, right blade right twist,
The twist angle of the outer peripheral cutting edge was 25 °, and for comparison, a sample No. 6 having a fine WC grain size was also produced. Next, a cutting test was conducted on each of the five pieces under the following conditions. Cutting speed = 100m / min, feed per blade = 0.03mm
/ Blade, depth of cut = 10 mm, width of cut = 5 mm,
Work Material SCM440 After 2 m cutting, the maximum flank wear amount (mm) and the chipping occurrence rate were measured. The chipping occurrence rate is expressed as a 100-percentage by dividing the sum of the lengths of the cutting edges that are chipped by the sum of the lengths of all the cutting edges. The results are shown in Table 2.

[0012]

[Table 2] Sample No. Number of tests Chipping occurrence rate Maximum flank wear amount Inventive Example 1 1st line 1.5% 0.01 1 2nd line 1.0% 0.01 1 3rd line 0.6% 0.01 1 4th 2.0% 0.01 1 5th 1.2% 0.01 Comparative Example 6 1st 8.5% 0.015 6 2nd 13.5% 0.16 6 3rd 1.8% 0. 01 6 4th 5.9% 0.02 6 5th 15.3% 0.19

It can be seen from Table 2 that the end mill according to the present invention has a good balance of strength and hardness, and thus is extremely excellent in chipping occurrence rate showing wear resistance and wear resistance.

[0014]

The present invention is based on the particle size of WC-based cemented carbide,
By optimizing the amount of grain suppressor and Co, it was possible to make use of the high rigidity, which is a characteristic of cemented carbide, and to provide strength. Further, by optimizing the grain size, defects in the alloy microstructure such as grain growth are reduced, and a fine grain cemented carbide showing stable performance.

Claims (2)

[Claims] 1. A hard phase comprising WC of 80 to 95% by weight and Ta of
C, VC, Cr3C2 at least one kind or two or more kinds in the WC-based cemented carbide consisting of 0.05 to 2.5% by weight, the balance binder phase is made of one or more kinds of iron group metals, A fine cemented carbide, characterized in that the average grain size of the phases is 0.7 to 1.0 μm. 2. The fine cemented carbide according to claim 1, wherein
VC in the range of 0.05 to 0.1% by weight.