JPH0271915A - Endmill - Google Patents

Abstract

PURPOSE:To eliminate any loss and breakage of an endmill and problem for the restric tion on its manufacturing in relation to a diameter by forming a rotation center part with super hard alloy with toughness and coaxially arranging on its outside circumfer ence, more than one cermet layers each of which includes more content of hard phase as it is positioned more outside. CONSTITUTION:A central part 1a is made of super hard alloy rich in toughness and Young's modulus with the composition of, for example, WC 94.5wt.%, Co 5.5wt.%, and more than one cermet layers 1b are arranged and its most outside circumferential layer is composed of the mixture of carbide and nitride belonging to IVa, Va, VIa group metal on a periodic table and/or 75-97wt.% of hard phase consisting of carbide and nitride and 3-25wt.% of combined metal phase consisting of at least Ni and/or Co and unavoidable impurities. In this case, for example, a bottom edge 2, an outside circumferential edge 3 and twisted grooves 4 are made by grinding after sintering both a reserved sintered metal of super hard alloy and the cylindrical reserved sintered metal of the cermet matching therewith simultaneously at high temperature so as to generate a diffused layer on the connected interface part of both metals. The cermet 1b is not used in the final layer because its toughness becomes poor with less than 3wt.% of combined metal content and its wear resistance is reduced when it is beyond 25wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an end mill used for planar processing of steel materials.

[Conventional technology]

Conventional technology for end mills includes those made entirely of a single material such as high-speed steel, cemented carbide, or cermet;
It is generally known that a hard film of Ti compound or the like is applied to the surface of these materials by a chemical vapor deposition method or the like. There are also indexable end mills in which the cutting edge is formed of a chip and is detachably attached.

[Problem to be solved by the invention]

The final performance requirements for end mills for flat and side surface machining are (a) good machined surface roughness, (b) good machining accuracy with less so-called collapse, and (c) long life. be.

Ranking the constituent materials of end mills in terms of machined surface roughness, from the viewpoint of compatibility with the steel being the workpiece, is cermet, cemented carbide, and high-speed steel.

In terms of machining accuracy, from the perspective of Young's modulus, ■Cemented carbide, ■Cermet, ■High speed steel, and the lifespan regarding wear, from the perspective of material hardness, ■Cermet, ■Cemented carbide, ■High speed steel. Ranked II [i] of steel.

As can be seen, cermet is highly suitable as an en[mill material]. However, on the other hand, it has a major weakness: it is fragile and easily damaged. For this reason, end mills made of a single material, cermet, are avoided especially when the diameter to length ratio is small, and the end mills that are put into practical use are not cermet end mills, but instead are made of high-speed steel or cemented carbide base material. Many of them are coated with a super-hard film made of a compound or the like to compensate for the weaknesses of the base material. However, this coating film also has problems such as being easily peeled off and its effectiveness being reduced by half after re-grinding.

In addition, when using a cermet tip with an indexable end mill, the base material (
However, there is a limit to the tool diameter that can be converted into a 7-way throw.

The present invention has been made in view of the above, and an object thereof is to provide an end mill that takes advantage of the characteristics of cermet and at the same time eliminates the problems of manufacturing limitations due to defects, folds, and diameter.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an end mill material in which the center of rotation is made of a tough cemented carbide, and the outer periphery of the end mill material has one cermet layer in which the content of the hard phase increases as the outer layer increases. Or two or more layers are arranged coaxially, and
The respective material layers are integrated into a composite structure via heat diffusion layers of mutual components formed at the respective bonding interfaces.

Then, chip discharge grooves and cutting blades are formed on the end mill material to produce a completed end mill.

The cermet used for the outermost layer of the end mill material is
For the reasons described below, the hard phase consisting of a mixture of carbides and nitrides and/or carbonitrides of metals from groups Na, Va, and Vla of the periodic table is 75 to 97% by weight, and contains at least Ni and/or Co and unavoidable impurities. It is preferable that the binder metal phase has a composition of 3 to 25% by weight.

[Effect]

If a strong cemented carbide with high toughness and Young's modulus is used in the center of the end mill material, the lack of rigidity of the cermet will be compensated for, and the behavior of the end mill due to cutting force will be reduced. For example, W
Composition of C94.5wt%, Co 5.5wt%, transverse rupture strength 205 kg/ta 2, Young's modulus 63X10'
If a cemented carbide with a kg/fi2 is used as the core material, the rigidity will be greatly improved compared to an end mill made of a cermet Hayabusa material with a low Young's modulus (cermet's Young's modulus is high (even 45xlO3 kg/m"). Falling and vibration during machining are reduced.

On the other hand, the center part of the end mill, which is not involved much in cutting, has weak requirements for wear resistance and welding resistance, so even if cemented carbide is used, the cutting performance will not be affected.

In addition, the outer periphery of the end mill is made of cermet mainly consisting of a hard phase such as TiC, TiN, TaC, TaN, etc., which exhibits the excellent wear resistance and adhesion resistance that are the characteristics of cermet. Since the effect continues afterward, the performance requirements regarding machined surface roughness and service life are fully satisfied.

In addition, each of the coaxially arranged material layers is so firmly bonded to each other that they are considered to be the same material through the heat diffusion layer formed at the joint interface. Also, abnormal wear of the joint interface does not occur.

Here, the properties of the cermet used for the outer periphery can be utilized even if the bonding metal phase contains a small amount of ordinary additives such as A1 or Zr, but if the content of the bonding metal is less than 3wL%, the toughness will deteriorate. There is a risk of chipping, etc., making it unsuitable for end mill applications.

Furthermore, if the amount exceeds 25-t%, the abrasion resistance decreases, making it difficult to meet the requirements for durability. This is why we have indicated the preferred content of bound metal phase for the final layer cermet.

For reference, the results of a comparative experiment on the amount of deflection using a round bar with an outer diameter of 8 mm were as follows.

In the experiment, the material was cantilevered with a protrusion of 50 mm and a load was applied. As for the comparison material, the product of the present invention has a composition of -C94.5% (this is the same below in terms of weight ratio), Co 5.5%, diameter is 6.5%, TiC 33%, TiN on the outer periphery of the core.
i3%, TaC12%, Mo, C10%, WCl5%,
The rest Ni, G.

Composite cermet layer with the composition of cermet 1
- The product is a single product of ZERMEYT with the above composition, and the ultrafine grain alloy is an IJT product with a composition of 87% WC and 13% Co.

[Example] FIGS. 1 and 2 show an example of the end mill of the present invention. This end mill 1 is made by grinding the end mill material 1' shown in FIG. 3 and finishing it with a two-sided type gluing having a bottom force 2, an outer circumferential edge 3, and a undulating groove 4 along the outer circumferential edge.

In the end mill material 1' shown in FIG. 3, the central portion 1a is made of a tough cemented carbide, the outer peripheral portion 1b is made of cermet, and both are integrally bonded together by thermal diffusion bonding.

Such compositing can be realized by the following 90-fold method. One of the methods is to take the above-mentioned combination of materials as an example. First, a cylindrical pre-sintered crystal (lightly sintered at a low temperature) is prepared using a cemented carbide containing 94.5 wL% of WC and 5.5 wt% of Co. Then, cylindrical pre-sintered crystals of cermet are made to fit these. Then, these are simultaneously sintered at high temperature to form a diffusion layer of cobalt, carbon, etc. at the bonding interface between the two.

In addition, the second method is to form the outermost layer Thermeso 1 to 1 without pre-sintering and directly sinter it, and at this time thermal expansion +B!
This is a way to make life come true.

Below, detailed examples will be described.

A spiral end mill with two black blades as shown in Fig. 1 with an outer diameter of 8 rin - 1 effective blade length of 15 m and a total length of 55 + n was manufactured by processing the material t4 used in the comparison experiment of flexible bamboo.
Ta.

Next, these three types of end mills were subjected to cutting under the following conditions.

Work material: 5C) l 435 u, 300 Cutting conditions:
Cutting speed V-100m/min, feed rate F = 20
0 am/min, sending star r = 0.05u/rev
, depth of cut Ad=5 mm, 1 inch (1-05 Cao Qian, dry cutting) Through this experiment, the machining time until the wear amount reached 0.15 tm and the finished surface roughness were investigated, and the results are shown in the table below.

[Effects] As described above, according to the present invention, the excellent properties of cermet in terms of wear resistance and welding resistance can be used to solve the problem of lack of rigidity found in cermet solid end mills. The problem of chipping and breakage caused by this is reduced to 1-. In addition, it is possible to maintain the cutting life even when cutting at twice the speed of conventional methods, and the finished surface consistency is also sufficiently improved, resulting in stable end mill processing.
It is possible to obtain the effects of increasing the height, increasing the hardness, and simplifying the final polishing in the post-process. In addition, since it can be processed in the same way as solid crystal made of a single material, small-diameter products can be easily manufactured without any manufacturing restrictions.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an example of an end mill invented by Mr.
FIG. 2 is a front view thereof, and FIG. 3 is a perspective view of the end mill material used in the exemplary end mill. 1... End mill, 2... Potential power, 3
......Peripheral blade, 4...Thread groove, 1'... End mill material, 1a... Central part made of J-toughness cemented carbide, 1
b...Outer periphery made of cermet. Patent applicant Sumitomo Electric Industries Co., Ltd. Agent Fumi Kamata

Claims (2)

[Claims] (1) The center of rotation is formed of a tough cemented carbide, and one or more cermet layers are arranged coaxially around the outer periphery, and the content of the hard phase increases as the outer layer increases. The material layer of the end mill is formed by forming a cutting discharge groove and a cutting blade on the end mill material, which has an integrally composite structure through a heat diffusion layer of each component formed at each joint interface. (2) A hard phase consisting of a mixture of carbides and nitrides and/or carbonitrides of metals from groups IVa, Va, and VIa of the periodic table is 75
2. The end mill according to claim 1, wherein a cermet having a composition of 3 to 25 weight % of a binder metal phase consisting of at least Ni and/or Co and unavoidable impurities is used for the outermost layer of the end mill material.