JPH0343113A - End mill made of tungsten carbide group cemented carbide - Google Patents

Abstract

PURPOSE:To prevent the occurrence of breaking or chipping by composing an end mill with WC group cemented carbide which is having the specific proportion of the jointed phase of Co group alloy and a hard dispersed phase substantially composed of WC, and in which the jointed phase contains the specific quantity of Cr and W and the remainder is composed of Co and an unavoidable impurity, and making the mean grain diameter of a WC grain a specific size. CONSTITUTION:An end mill is composed of WC group cemented carbide having a composition (weight percent hereinafter) in which the proportion of the jointed phase of Co group alloy and a hard dispersed phase substantially composed of WC is made 6-23% of the jointed phase and 77-94% of the hard dispersed phase, the jointed phase contains Cr of 1-15% and W of 5% or below, and the remainder is composed of Co and an unavoidable impurity, moreover a mean grain diameter of the hard dispersed phase (WC grain) is 0.5-2mum. High toughness and high strength can be provided by the hard dispersed phase, the occurrence of breaking or chipping can be eliminated even in cutting of high hardness steel or the like, and excellent cutting performance can be obtained for a considerable long period.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to an end mill made of tungsten carbide (hereinafter referred to as WC) Mi cemented carbide, which has high strength, high toughness, and excellent wear resistance. It is.

[Conventional technology]

Conventionally, end mills used as cutting tools are generally manufactured using WCC cemented carbide, and the ratio of the binder phase of the WCC cemented carbide and the Co-based alloy to the hard dispersed phase substantially consisting of WC is as follows: binder phase: 10 .5-16.5%.

Hard dispersed phase: 83.5-89.5%.

and the above bonded phase is V: 2.5-11.6%.

v55., with the remainder being Co and unavoidable impurities (wt%), and further solid-dissolved in the binder phase. is blended in the form of vanadium carbide (hereinafter referred to as VC) powder when blending the raw materials, decomposes during sintering, and solid-solves in the binder phase, thereby suppressing the growth of WC grains and, rather, making them finer. It is also well known that it is contained for the purpose of reducing the average particle size to less than 0.5 m, thereby increasing hardness and improving wear resistance.

[Problem to be solved by the invention]

However, in the above-mentioned conventional WCC cemented carbide end mill, the hardness increases due to the refinement of the WC grains due to the solid solution of component (1) in the binder phase, and the wear resistance improves. On the other hand, the toughness decreases, so if this is used for cutting high-hardness materials or high-feed cutting, breakage and chipping of the cutting edge are likely to occur due to lack of toughness and strength.
The current situation is that the service life is reached in a relatively short period of time.

[Means to solve the problem]

Therefore, from the above-mentioned viewpoints, the present inventors conducted research to develop an end mill made of WCC cemented carbide that has high toughness, high strength, and excellent wear resistance. , the ratio of the Co-based alloy binder phase and the hard dispersed phase substantially consisting of WC is: binder phase: 6 to 23%.

Hard dispersed phase: 77-94%.

and the above bonded phase is Cr: 1 to 15%, W: 5% or less.

When the WCC cemented carbide is composed of chromium carbide (hereinafter referred to as Cr3C2
) powder, chromium nitride (hereinafter referred to as CrN) powder,
Alternatively, Cr is blended in the form of chromium oxide (hereinafter referred to as Cr2O3) powder, decomposed during sintering, and dissolved as a solid solution in the binder phase.
The effect of this suppresses the growth of regular grains in the WC grains, and also prevents their dispersion, resulting in an average grain size of 0.5 to 211 Ja. Although it is coarser than the WC grains, which are refined to an average grain size of less than 0.5 grains due to the inclusion of the V component in the binder phase in hard alloy end mills, these relatively coarse WC grains provide high toughness. is ensured, and at the same time, the solid solution amount of the W component in the binder phase after sintering is suppressed to 5% or less, preventing a decrease in toughness due to W solid solution in the binder phase, making it suitable for use as an end mill. We have learned that this product prevents breakage and chipping when the product is used, and that it has high hardness equivalent to that of the conventional WCC cemented carbide end mill, and exhibits excellent cutting performance over a long period of time. I got it.

This invention was made based on the above knowledge, and Co7! The ratio of the binder phase of the alloy to the hard dispersed phase substantially consisting of WC is: binder phase: 6 to 23%.

Hard dispersed phase: 77-94%.

and the above bonded phase is C: 21-15%, W: 5% or less.

, with the remainder consisting of Co and unavoidable impurities, and furthermore, the hard dispersed phase (WC grains) has an average particle size of 0.5~
2I! This is a characteristic feature of the end mill made of WCC cemented carbide.

Next, the reason for limiting the conditions as described above in the end mill of the present invention will be explained.

(a) Ratio of binder phase and hard dispersed phase If the binder phase ratio is less than 6%, the proportion of WC, which essentially constitutes the hard dispersed phase, becomes too large, exceeding 94%, resulting in a decrease in toughness. On the other hand, if the proportion of the binder phase exceeds 23%, the proportion of WC becomes too small, less than 77%, and the wear resistance decreases. 23%, hard dispersed phase: 77
It was set at ~94%.

Note that preferably the binder phase: 8 to 12%, the hard dispersed phase: 8%
The ratio is preferably 8 to 92%.

(b) Content of Cr and W in the binder phase As mentioned above, the C3C2 powder and CrN powder used as raw material powder, as well as the Cr2O3 powder, decompose during sintering and solidify in the binder phase. This solid solution Cr suppresses abnormal grain growth and refinement of WC grains, maintains the average grain size in the range of 0.5 to 2 un, and ensures wear resistance and toughness. It has the effect of suppressing the solid solution amount of W in the binder phase to 5% or less, preferably 3% or less, and preventing the toughness of the binder phase from becoming low f. If Cr: is less than 1%, the desired effect will not be achieved, while if the content exceeds 15% of Cr in the binder phase, an abnormal phase will occur in the alloy. The content of C is determined to be 1 to 15% since the toughness is significantly reduced.The content of Cr is preferably 5 to 10%.

〔Example〕

Next, the end mill of the present invention will be specifically explained with reference to Examples.

As raw material powders, WC powder, Cr3C2 powder, CrN powder, Cr2O3 powder, and VC powder all have an average particle size within the range of 0.5 to 2 am, and the average particle size:
Co powder having a diameter of 1.3 nm was prepared, these raw material powders were blended in the proportions shown in Table 1, wet mixed in a ball mill for 72 hours, dried, and then press-molded into a green compact. The powder was heated to 1320 to 1450 in a vacuum atmosphere.
By sintering at a predetermined temperature within the range of °C and polishing, it is made of WCC cemented carbide having the same composition as shown in Table 1, and outer diameter: 6 m + * length: 50 m.
(hereinafter referred to as the present invention carbide end mill) 1 to 21. and conventional WC
C cemented carbide solid end mills (hereinafter referred to as conventional cemented carbide end mills) 1 to 5 were manufactured, respectively.

Next, regarding the various end mills obtained as a result,
The average grain size and Rockwell hardness (A scale) of the WC grains were measured, and the transverse rupture strength was also measured for the purpose of planning toughness and strength.
Hardness: HRCal), Cutting speed: 30m/sin
.

Feed: 0.02mm/blade, Depth of cut: 6mm.

A groove machining test on high hardness steel was conducted under the following conditions, and the cutting length until the wear width of the peripheral blade reached 0.4+am was measured. The results of these measurements are shown in Table 1.

〔Effect of the invention〕

As is clear from the results shown in Table 1, all of the carbide end mills 1 to 21 of the present invention exhibit an average particle size of WC 0.5 to 2, and as a result, high toughness and high strength are ensured. As a result, cutting tests have shown that even though the workpiece material is high-hardness steel, there is no breakage or chipping, and it shows excellent wear resistance, whereas conventional carbide end mills 1 to 5 all have fine WC grains and 0.5I1
As a result, the toughness and strength decreased, and in cutting tests, chipping occurred on the cutting edge in all cases, and the service life was reached in a relatively short period of time.

As mentioned above, the WCC cemented carbide end mill of the present invention has a binder phase with a C content of 1 to 15%, a W content of 5% or less, and an average grain size of substantially 0.5%. ~2 It has high toughness and high strength due to the hard dispersed phase composed of WC grains, and there is no breakage or chipping even when cutting high-hardness steel or high-feed cutting, making it an excellent material. It exhibits wear resistance and exhibits excellent cutting performance over an extremely long period of time.

Claims (1)

[Claims] (1) The ratio of the binder phase of the Co-based alloy and the hard dispersed phase consisting essentially of tungsten carbide is as follows: binder phase: 6 to 23%, hard dispersed phase: 77 to 94%. The binder phase contains Cr: 1 to 15%, W: 5% or less, with the remainder being Co and unavoidable impurities (in weight percent), and further carbonization of the hard dispersed phase. An end mill made of tungsten carbide-based cemented carbide in which the average grain size of tungsten grains is 0.5 to 2 μm.