JP2737677B2 - Nitrogen-containing sintered hard alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrogen-containing sintered hard alloy, and more particularly to a cutting tool which is extremely excellent in thermal shock resistance, has excellent wear resistance and strength, and can be used for wet cutting. It relates to a nitrogen-containing sintered hard alloy.

[0002]

2. Description of the Related Art A sintered hard alloy containing nitrogen in which a carbon nitride or the like containing Ti as a main component is used as a hard phase and bonded with a metal composed of Ni and Co has already been put into practical use as a cutting tool. This nitrogen-containing sintered hard alloy has a remarkably fine hard phase compared to a conventional sintered hard alloy not containing nitrogen.
It has been widely used as a cutting tool along with a so-called cemented carbide containing C as a main component. However, in this nitrogen-containing sintered hard alloy, the thermal conductivity of the carbonitride of Ti, which is the main component, is significantly smaller than the thermal conductivity of WC, which is the main component of the cemented carbide. The thermal conductivity of the hard alloy is about の of that of the cemented carbide, and the coefficient of thermal expansion also depends on the characteristic value of the main component. For example, the resistance to thermal shock is reduced. For this reason, cutting under particularly severe conditions of thermal shock, such as milling and cutting of square bars with a lathe, and wet copying where the depth of cut fluctuates greatly, compared to coated cemented carbide, etc. The current situation was low reliability. To solve such a problem, for example, JP-A-2-15139 and JP-A-5-9646 disclose tough cermets.

A nitrogen-containing sintered hard alloy is disclosed in
As disclosed in, for example, Japanese Patent Application Publication No. 51201, a hard phase particle has a so-called cored double structure, and a core portion in which Ti and N are enriched, and W and Mo are enriched and N is poor. It is formed with the peripheral part. When such an alloy having a double structure is subjected to X-ray diffraction measurement (Cu-Kα ray), as shown in FIG. 3, peaks from the same diffraction plane having the same B1 structure are separated into two and detected. Here, the peak with a high intensity on the low angle side of the diffraction angle is that of the peripheral portion, and the peak with a low intensity on the high angle side is that of the core.

[0004]

However, the cermets disclosed in any of the above publications have improved wear resistance and toughness, but have insufficient fracture resistance as compared with coated cemented carbide. In addition, thermal shock resistance, particularly thermal cracking, and sudden loss due to crack propagation caused by both thermal shock and mechanical shock are likely to occur, and sufficient reliability cannot be obtained. Then, the present inventors have conducted detailed research on the analysis of cutting phenomena such as temperature distribution in various cutting and the arrangement of material components in a tool, and as a result, have reached the present invention. The present invention is a cutting tool nitrogen for cutting tools that can be used with high reliability without applying a surface coating, even in machining under severe thermal shock conditions that could only be used with conventional expensive coated cemented carbide. It is an object of the present invention to provide a sintered hard alloy.

[0005]

Means for Solving the Problems The ratio of the core portion (black core) of the core structure of the hard phase particles is set to be within a certain range in which the alloy surface portion is equal to or larger than the alloy inside, and the tool performance, In particular, they have found that wear resistance can be significantly improved, and have reached the present invention. That is, the nitrogen-containing sintered hard alloy of the present invention is a carbide, nitride, carbonitride or a carbide of Ti and at least one transition metal other than Ti selected from Groups 4a, 5a and 6a of the periodic table. 75 to 95% by weight of a hard phase composed of at least one of the following composite carbonitrides, 5 to 25% by weight of a binder phase containing Ni, Co and unavoidable impurities, and a peak of the B1 structure in X-ray diffraction measurement. In a nitrogen-containing sintered hard alloy where two types are detected,
Among the peaks from the same diffraction plane of the two B1 structures in X-ray diffraction, the intensity of the small intensity peak detected on the high angle side of the diffraction angle is I _s , and the intensity of the high intensity peak detected on the low angle side of the diffraction angle. strength of the I _L, I at the alloy surface portion
_S / the peak intensity ratio represented by I _L I _H, 1m alloys
The peak intensity ratio represented by I _S / I _L inside or m is I _H / I _N when the I _N, the nitrogen-containing sintered hard, characterized in that it is 0.5 to 3.0 Alloy. The hard phase in the present invention has a wear resistance of less than 75% by weight,
The plastic deformation resistance is remarkably reduced, and if it exceeds 95% by weight, strength and toughness are insufficient, which is not preferable. I _H / I of the present invention
_{If N} is less than 0.5, the abrasion resistance is insufficient, and if it exceeds 3.0, the desired thermal shock resistance cannot be obtained. In the present invention, not only the hard phase having the B1 structure but also the WC phase may be present inside.

[0006]

According to the present invention, when a core having a cored structure is increased on the surface, this part is essentially excellent in abrasive wear resistance, heat resistance, and chemical stability, so that the wear resistance can be increased. The peripheral portion of the cored structure with high strength can be increased, the tool strength can be improved, and a high-performance tool as a whole can be obtained. However, if the number of the cores is too large, the strength of the surface portion is reduced.

[0007] The alloy of the present invention is obtained by wet mixing desired raw materials, embossing, and vacuuming to 1400 in a nitrogen atmosphere.
After sintering at about 1700 ° C., it can be prepared by gradually cooling in a decarburized and denitrified atmosphere.

Hereinafter, the present invention will be described in more detail with reference to Examples, but is not intended to limit the present invention.

【Example】

(Example 1) The outer part of the cored structure having an average particle size of 2 μm looks pure white in a reflection electron microscope image and the core part looks pure black (Ti _0.85 Ta _0.05 Nb _0.04 W _0.06 ) (C
_0.55 N _0.45 ) Powder, WC powder of 0.7 μm, Ni powder and Co powder of 1.5 μm, 45% by weight, 40% by weight, 7% by weight, and 8% by weight, respectively, are wet-mixed and then pressed. After molding and degassing at 1200 ° C. in a vacuum of 10 ⁻² Torr, a nitrogen gas partial pressure is 1490 at a pressure of 20 to 50 Torr.
After sintering at 2.5 ° C / min for 1 hour in vacuum,
Sample 1 was prepared. Intensity ratio I _H determined from the diffraction curve from (220) plane of Cu-K [alpha line B1 structure of X-ray on the surface lapping surface of the sample 1 is 0.1, the intensity ratio I _N at 1mm inside from the surface 0.18, I _H / I _N = 0.56
(See FIG. 1). 35% by weight of TiCN, 4% by weight of TaC, 2% by weight of NbC, 44% by weight of WC, 7% by weight of Ni, and 8% by weight of Co were blended so as to have the same alloy composition as Sample 1, and sintered under the same conditions as Sample 1 to prepare Sample 2, Also,
A mixture of 46% by weight of TiCN, 8% by weight of TaC, 8% by weight of Mo ₂ C, 20% by weight of WC, 6% by weight of Ni, and 12% by weight of Co was mixed and sintered under the same conditions as Sample 1 to prepare Sample 3, which was the same as Samples 1 and 2. Each of the embossed compacts is nitrogen partial pressure
Sinter at 1430 ° C with Torr, CO partial pressure 200 Torr
After cooling at r, Samples 4 and 5 were prepared, respectively.

Further, (Ti _0.87 Nb) having an average particle size of 2 μm
_0.07 W _0.06 ) (C _0.5 N _0.5 ) powder, and 85 wt% and 7 wt% of 1.5 μm Ni powder and Co powder, respectively.
After wet mixing 8% by weight, embossing is performed, and 10 ⁻² Torr is applied.
After degassing at 1200 ° C in a vacuum, partial pressure of nitrogen gas is 15T
After sintering at 1480 ° C for 1 hour at vacuum or vacuum (10 ^-5 T
orr) in ultra-slow cooling (0.5 to 5 ° C./min) to prepare Sample 6, which is also slowly cooled in CO ₂ 5 Torr (5 to 10 ° C.).
/ Min) to prepare Sample 7, quenched in N ₂ (100 To
rr, 10 to 50 ° C / min) to prepare Sample 8. Ti
35% by weight of CN, 6% by weight of NbC, 44% by weight of WC, N
Sample 6, containing 8% by weight of i and 7% by weight of Co,
Sintered under the same conditions as in Samples 7, 8
1 was prepared. A mixture of 56% by weight of TiCN, 8% by weight of NbC, 8% by weight of Mo ₂ C, 10% by weight of WC, 10% by weight of Ni, and 8% by weight of Co was sintered under the same conditions as Samples 1 and 4 to obtain Samples 12 and 13, respectively. After preparation, each I _H / I _N was determined, and the tool shape CNMG4
No. 32 was prepared and subjected to the following cutting tests for abrasion resistance evaluation and thermal shock resistance evaluation, and the obtained results are shown in Table 1 and FIG. Samples 2, 9, 10, and 11 have WC inside the alloy structure.
Was precipitated.

Wear resistance cutting test Tool shape SNMG432 Work material SCM435 (H _B = 240) Round bar Cutting speed 200 m / min Feed 0.3 mm / rev. Depth of cut 1.5mm Cutting oil Water soluble Cutting time 10 minutes Judgment Flank wear width V _B (mm) Thermal shock resistant cutting test Work material SCM435 (H _B = 220) Round bar Cutting speed 250m / min Feed 0.23mm / rev . Cutting depth fluctuates from 2.0 to 0.2 mm Cutting oil Water-soluble Cutting time 15 minutes Judgment Number of missing cutting edges in 20 cutting edges (pieces)

[0011]

[Table 1]

[0012]

As described above, according to the present invention, as a cutting tool, cutting under particularly severe conditions of thermal shock, for example, milling or cutting of a square bar by a lathe, or wet copying in which the cutting depth greatly varies. The present invention has an effect that a highly reliable nitrogen-containing sintered hard alloy can be provided without a coating in a machining area, such as cutting, where a conventionally expensive coated cemented carbide tool could not be used.

[Brief description of the drawings]

FIG. 1 shows (a) a surface portion of a sample 1 in an embodiment,
(B) It is a diffraction curve of the inside X-ray Cu-Kα ray.

FIG. 2 shows (a) a surface portion of Sample 2 in the embodiment;
(B) It is a diffraction curve of the inside X-ray Cu-Kα ray.

FIG. 3 is a diffraction curve from a B1 structure (220) plane which is a typical conventional cermet of X-ray Cu-Kα rays of a nitrogen-containing sintered hard alloy having a cored double structure.

Claims (1)

(57) [Claims] 1. Ti and 4a, 5a, 6a group of the periodic table
Charcoal of at least one transition metal excluding Ti selected from
, Nitride, carbonitride or composite carbonitride of these
75 to 95% by weight of a hard phase comprising at least one of
%, The binder phase containing Ni and Co and unavoidable impurities is
5 to 25% by weight, and the peak of the B1 structure is determined by X-ray diffraction measurement.
In a nitrogen-containing sintered hard alloy where two types of cracks are detected,
From the same diffraction plane of two B1 structures in X-ray diffraction measurement
Intensity of small peak detected at high angle side of diffraction angle at peak
To I_S, A strong intensity peak detected on the lower angle side of the diffraction angle
The strength of the_LAnd I at the alloy surface_S/ I _LRepresented by
The peak intensity ratio_H, I within 1 mm of the alloy
_S/ I_LThe peak intensity ratio represented by_NI when
_H/ I_NIs 0.5 or more and 3.0 or less.
Nitrogen-containing sintered hard alloy.