JP2000038637A - End mill made of surface-coated cemented carbide in which substrate has high toughness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated super hard end mill in which a substrate has high toughness while maintaining the excellent wear resistance of the substrate. SOLUTION: This end mill is obtd. by physically vapor-depositing the surface of a substrate composed of cemented carbide showing a structure in which hard dispersion phase occupy 70 to 93 area%, and the balance bonding phases essentially consisting of Co with inevitable impurities by structural observation by an electron microscope, in which the hard dispersion phase is composed of coated WC obtd. by wholly coating and/or partially coating WC with a thin layer of (V, W, Cr) C, also, the average particle size is <=1.0 μm, and, furthermore the contents of Co, Cr and V are controlled to 5 to 13% Co, 0.2 to 2% Cr and 0.05 to 0.3% V with a hard coating layer of a single layer of one kind among a TiC layer, a TiN layer, a TiCN layer, a (Ti, Al) C layer, a (Ti, Al) N layer and a (Ti, Al) CN layer or double layers of >= two kinds thereamong by the average layer thickness of 0.5 to 6 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end mill made of a surface-coated cemented carbide (hereinafter simply referred to as a coated cemented carbide end mill) whose toughness is remarkably improved while maintaining excellent wear resistance of a substrate. Things.

[0002]

2. Description of the Related Art Conventionally, coated carbide end mills are generally
As illustrated in a schematic front view in FIG. 3, it is composed of a cutting edge portion and a shank portion in which a peripheral edge having a sharp edge is formed,
It is well known that it is used for shoulder milling and grooving of carbon steel and die steel. In the coated cemented carbide end mill, as shown in the schematic diagram of the structure observation by an electron microscope in FIG. 2, the base constituting the hard dispersed phase occupies 70 to 93 area%, and the remainder is Co.
Shows a structure composed of a binder phase mainly composed of: (a) tungsten carbide (hereinafter, referred to as WC);
(B) Precipitated composite carbide of V, W, and Cr precipitated in the binder phase during the cooling process during sintering [hereinafter, referred to as (V, W, Cr) C], comprising (a) and (b) , And all have an average particle diameter of 1.0 μm or less due to the action of the V component, and further contain Co, Cr, and V in weight% (hereinafter, referred to as
(% Simply indicates weight%), Co: 5 to 13%, C
r: 0.2 to 2%, V: 0.05 to 0.3%, which is composed of a WC-based cemented carbide (hereinafter referred to as a cemented carbide) and has a surface of The hard coating layer physically deposited with an average layer thickness of ６6 μm comprises
A TiC layer, a nitride (hereinafter TiN) layer,
And a carbonitride (hereinafter referred to as TiCN) layer,
Composite carbide layer of i and Al [hereinafter referred to as (Ti, Al) C] layer, composite nitride [hereinafter referred to as (Ti, Al) N]
It is also known to consist of a single layer or a composite layer of two or more of a layer and a composite carbonitride [hereinafter, referred to as (Ti, Al) CN] layer.

[0003]

On the other hand, in recent years, there has been a strong demand for labor saving and energy saving for cutting, and with this, cutting tends to be heavy cutting such as high cutting and high feed. In the case of conventional coated carbide end mills, if this is used for cutting at a higher cutting depth or higher feed, chipping due to insufficient toughness of the base in this part is likely to occur, especially on the outer peripheral edge, and it will be relatively short. At present, the service life is reached.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoint, paying attention to the above-mentioned conventional coated carbide end mill, research was carried out to improve the toughness of the outer edge with a sharp edge in particular, without impairing the excellent wear resistance of the base constituting the end mill. As a result, the sintering of the substrate constituting the above-mentioned conventional coated carbide end mill (hereinafter referred to as “conventional substrate”) was performed in the range of “0.01 to 0.01”.
In a vacuum atmosphere of 0.1 torr, temperature: 1350-14
After holding at 80 ° C. for 1 to 2 hours, the furnace is cooled to at least 1200 ° C. (the cooling rate in this case is about 10 ° C./min). .1
In a vacuum atmosphere of torr, temperature: 1350-1480 ° C
After holding for 1 to 2 hours, the atmosphere is changed to 50 to 150 kg / cm.
^After changing to a pressurized atmosphere of ² and keeping in this pressurized atmosphere for 15 to 60 minutes, at least
/ Quenching at a cooling rate of / min ", (V, W, Cr) C precipitates in the binder phase at the time of cooling and independently forms a hard dispersed phase in the cemented carbide of the conventional substrate. By changing the vacuum atmosphere to a pressurized atmosphere as described above, by rapidly cooling after maintaining the pressurized atmosphere for a predetermined time,
As schematically shown in FIG. 1 by microscopic observation of the structure by an electron microscope, (V, W, Cr) C is deposited on the surface of the WC as a thin coating layer and / or a partially coating thin layer to form a coating WC. No precipitation occurs in the binder phase. Thus, the precipitation ratio of (V, W, Cr) C is almost the same as in the conventional substrate, and (V, W, Cr) C is present in the binder phase.
Cemented carbide with no precipitation of (V, W, Cr) in the binder phase
While maintaining excellent wear resistance equivalent to that of the above-described conventional substrate cemented carbide in which C is dispersed and precipitated, the substrate has higher toughness than this, and therefore, the substrate of the coated carbide end mill is coated with this cemented carbide. If it is configured, even if it is used for heavy cutting such as high cutting and high feed, especially since the outer peripheral edge of the base has excellent toughness, there is no occurrence of chipping, etc.
The research results show that excellent cutting performance will be exhibited over a long period of time.

The present invention has been made on the basis of the above-mentioned research results. According to the structure observation by an electron microscope, the hard dispersed phase occupies 70 to 93% by area, and the remainder consists of the binder phase mainly composed of Co. Shows the following structure, the hard dispersed phase,
A coated WC in which WC is entirely and / or partially coated with a thin layer of (V, W, Cr) C;
m, less than or equal to Co, Cr, and V
Content of Co: 5 to 13%, Cr: 0.2 to 2%,
V: 0.05 to 0.3%, a TiC layer, a TiN layer, and a TiCN layer
Layers, further (Ti, Al) C layer, (Ti, Al) N layer,
And a hard coating layer composed of a single layer of the (Ti, Al) CN layer or a multi-layer of two or more layers of 0.5 to 6 μm.
The characteristic feature is a coated carbide end mill having a substrate having high toughness, which is formed by physical vapor deposition with an average layer thickness of.

Next, in the coated cemented carbide end mill of the present invention, the composition of the cemented carbide and the coated WC
The reason why the average particle size of the hard dispersed phase composed of and the average layer thickness of the hard coating layer are limited as described above will be described. (A) Composition (a) Ratio of Hard Dispersed Phase (Coated WC) If the ratio is less than 70 area%, desired excellent wear resistance cannot be secured, while the ratio is 93 area%.
If it exceeds, the ratio of the binder phase becomes relatively too small,
Since the strength suddenly decreases, the ratio is set to 70 to 93 area%, preferably 83 to 90 area%.

(B) Content of Co The Co component has the effect of improving sinterability and forming a binder phase to improve strength. However, if its content is less than 5%, a sufficient strength improving effect is not obtained. When the content exceeds 13%, a sharp decrease in wear resistance cannot be avoided. Therefore, the content is set to 5 to 13%, preferably 6 to 10%.

(C) Cr content As described above, the Cr component is deposited on the surface of the WC as a thin layer entirely coated and / or a thin layer partially coated thereon (V, W, C)
r) Forming C to improve wear resistance and dissolving in the binder phase to improve heat resistance,
If the content is less than 0.2%, a desired improvement effect on the above-mentioned effect cannot be obtained. On the other hand, if the content exceeds 2%, the solid solution ratio in the binder phase becomes too high, and the strength is reduced. Therefore, the content is determined to be 0.2 to 2%, preferably 0.3 to 1%.

(D) Content of V In the V component, (V, W, Cr) C is also formed to improve wear resistance, and also forms a solid solution in the binder phase to form a solid solution during sintering. Although the coating WC has an effect of suppressing the grain growth, if the content is less than 0.05%, the hard (V,
Not only is it difficult to form (W, Cr) C, but even when the average particle size of the WC powder as the raw material powder is 1.0 μm or less, the coated WC exceeds 1.0 μm due to grain growth during sintering. Since the average particle size is reached, the desired strength cannot be secured and the occurrence of breakage cannot be suppressed. On the other hand, if the content exceeds 0.3%, the strength of the binder phase itself decreases. The content is determined to be 0.05 to 0.3%, desirably 0.1 to 0.2%, since breakage easily occurs.

(E) Average particle size of coated WC The average particle size of the coated WC constituting the hard dispersed phase is adjusted by the average particle size and the V content of the WC powder as a raw material powder as described above. When the particle size exceeds 1.0 μm, the strength is significantly reduced due to coarsening of the hard dispersed phase particles. Therefore, the average particle size is set to 1.0 μm or less.

(F) Average Layer Thickness of Hard Coating Layer If the average layer thickness is less than 0.5 μm, the desired excellent wear resistance cannot be secured, while the average layer thickness is 6 μm.
If it exceeds m, chipping (small chipping) will occur on the outer peripheral edge, which will shorten the service life, so the average layer thickness is set to 0.5 to 6 μm, preferably 1 to 3 μm.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the coated carbide end mill of the present invention will be specifically described with reference to examples. As raw material powders, WC powders each having an average particle size of 0.8 μm;
A 5 μm VC powder, a 2.3 μm Cr ₃ C ₂ powder, and a 1.2 μm Co powder were prepared, and these raw material powders were blended into a predetermined composition, and wet-mixed with a ball mill for 72 hours using acetone. After drying under reduced pressure, further adding a wax and a solvent and mixing for 1 hour, the extruded press was used to form a long molded body having a diameter of 13 mm. After maintaining at a predetermined temperature in the range of 1350 to 1480 ° C. for 1.5 hours in a vacuum atmosphere of 0.055 torr, the atmosphere was reduced to a pressure of 60 kgf / cm.
^After changing to the pressurized atmosphere of No. ² and holding in this pressurized atmosphere for 25 minutes, sintering is performed at a predetermined cooling rate within a range of 50 to 100 ° C./min under a rapid cooling condition up to 1200 ° C., so that the cemented carbide is removed. A long sintered material having a diameter of 11 mm was manufactured.
The contents of the o, Cr, and V components were measured, and the arbitrary cross section was measured with a transmission electron microscope and an energy dispersive X
Observation was performed using a line spectrometer, and after confirming that the hard dispersed phase was composed of the coated WC, the average particle size was measured, and the ratio was calculated by an image analyzer. The results are shown in Table 1. The results of measurement and calculation are shown, and the outer peripheral blade diameter (edge diameter) is 10 m by grinding from the long sintered material.
m, helix angle: 45 °, two-flute square end mill bases (end mill bases of the present invention) A to H were manufactured, respectively. For the purpose of comparison, the sintering conditions were set to 0.05 torr.
r in a vacuum atmosphere at a predetermined temperature in the range of 1350 to 1480 ° C. for 1.5 hours, followed by furnace cooling (120 ° C. in this case).
End mill substrates (conventional end mill substrates) a to h as shown in Table 2 were produced under the same conditions except that the cooling rate to 0 ° C. was about 10 ° C./min).

Next, the above-mentioned end mill substrates A to A of the present invention are described.
A hard coating layer having the composition and the average layer thickness shown in Tables 3 and 4 is formed on the surface of the H and the conventional end mill substrates a to h using an ion plating method, which is a kind of physical vapor deposition method, under normal conditions. The coated carbide end mill 1 of the present invention
-8 and conventional coated carbide end mills 1-8, respectively.

For the coated carbide end mills 1 to 8 of the present invention and the conventional coated carbide end mills 1 to 8 obtained as a result, work material: S45C, cutting speed: 120 m / min, feed per tooth: 0.08 mm / Blade, depth of cut: 15 mm, width of cut: 1 mm, type: down cut, cutting length: 30 m, wet high-feed cutting test of carbon steel under the following conditions, work material: S45C, cutting speed: 100 m / min, feed per tooth: 0.04 mm / tooth, depth of cut: 15 mm, width of cut: 1.6 mm, type: down cut, cut length: 30 m, wet high cut test of carbon steel under the following conditions: The operation was performed on ten end mills, and the state of occurrence of defects at the outer peripheral edge was observed. In this case, even if one defect occurred on the outer peripheral edge, it was considered that a defect occurred. Tables 3 and 4 show the measurement results.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

From the results shown in Tables 3 and 4, all of the coated cemented carbide end mills 1 to 8 of the present invention have a base (hard alloy) composed of (V, W, Cr) C of WC. And (V, W, Cr) C are dispersed and dispersed in the binder phase. Compared with conventional coated carbide end mills 1 to 8 composed of a substrate having the same abrasion resistance, showing a much stronger toughness,
It is apparent that the occurrence of chipping of the outer peripheral edge is extremely small even in heavy cutting such as high cutting and high feed, and excellent cutting performance is exhibited over a long period of time. As described above, the coated cemented carbide end mill of the present invention has a substrate having high toughness, and therefore, of course, can be cut under ordinary conditions.
Even in heavy cutting such as high depth of cut and high feed where high toughness is required, the occurrence of chipping on the outer peripheral edge is extremely small and stable cutting is possible. It can respond to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a structure observation result by an electron microscope of a cemented carbide substrate constituting a coated cemented carbide end mill of the present invention.

FIG. 2 is a schematic view showing a structure observation result by an electron microscope of a cemented carbide substrate constituting a conventional coated cemented carbide end mill.

FIG. 3 is a schematic front view showing a coated carbide end mill.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Teruyoshi Tanase 1511 Furamagi, Ishishita-cho, Yuki-gun, Ibaraki Pref. Mitsubishi Materials Corporation Tsukuba Works (72) Inventor Taketo Sasama 1-10 Takanodai, Funabashi-shi, Chiba -6 F term (reference) 4K029 AA04 BA54 BA55 BA58 BA60 BB02 BC02 BD05 4K044 AA09 AB10 BA18 BB02 BC01 CA13

Claims (1)

[Claims] 1. Structure observation by an electron microscope shows a structure in which the hard dispersed phase occupies 70 to 93% by area, and the rest is composed of a binder phase mainly composed of Co. A coated tungsten carbide coated entirely and / or partially with a thin layer of a precipitated composite carbide of W and Cr;
It has an average particle size of not more than μm, and further contains Co, Cr and V in weight%, Co: 5-13%, Cr: 0.2-2%, V: 0.05-0. 3%, on the surface of a substrate made of a tungsten carbide-based cemented carbide, a Ti carbide layer, a nitride layer, and a carbonitride layer, and a Ti and Al composite carbide layer, a composite nitride layer, and a composite A surface coating having a high toughness on a substrate, which is obtained by physical vapor deposition of a hard coating layer composed of one type of carbonitride layer or two or more types of multiple layers with an average layer thickness of 0.5 to 6 μm. End mill made of cemented carbide.