JP2737676B2 - 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 due to a factor of three. For this reason, cutting under severe thermal shock conditions, such as milling and turning of square bars,
In addition, in the current situation, the reliability is lower than that of a coated cemented carbide or the like in wet copying in which the depth of cut greatly varies. To solve such a problem, see, for example,
JP-A-15139 and JP-A-5-9646 propose 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), a peak from the same diffraction plane having the same B1 structure is 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]

In the above-mentioned alloy having a double structure, the composition and structure of the alloy surface are reduced by reducing the proportion of the core in the cored structure, increasing the abundance ratio of the structure in the peripheral part, and increasing the composition fluctuation. It has been found that setting the crystal strain within a certain range can significantly improve wear resistance, thermal shock resistance, and toughness, and have reached the present invention. That is, the nitrogen-containing sintered hard alloy of the present invention comprises Ti and a carbide of at least one transition metal except Ti selected from Groups 4a, 5a and 6a of the periodic table;
75 to 95% by weight of a hard phase comprising at least one kind of nitride, carbonitride or composite carbonitride thereof;
5 to 2 binder phases containing Ni and Co and unavoidable impurities
5% by weight, and the peak of the B1 structure was 2 in the X-ray diffraction measurement.
In the detected nitrogen-containing sintered hard alloy, half of the X-ray diffraction peak of the larger intensity peak detected on the low angle side among the peaks from the same diffraction plane of the two B1 structures in the X-ray diffraction measurement Price range (hereinafter, half price range)
Is a nitrogen-containing sintered hard alloy characterized in that the half width measured at the alloy surface is 60% or more and less than 80% of the half width measured at 1 mm or more inside the alloy. 60%
If it is less than 80%, the plastic deformation resistance is poor, and if it is 80% or more, the thermal shock resistance is insufficient, which is not preferable. In the present invention, not only the hard phase having the B1 structure but also a WC phase may be present inside.

[0006]

According to the present invention, when the composition fluctuation and crystal distortion at the peripheral portion of the cored structure are made smaller than those inside the alloy,
Since the plastic deformation resistance of this portion is excellent, the creep strength can be increased, the tool strength can be improved, and a high-performance tool as a whole can be obtained. However, if it is too small, the effect of strengthening the matching strain in metallurgy cannot be expected, and the toughness and thermal shock resistance become insufficient.

The alloy of the present invention can be prepared by wet-mixing desired raw materials, sintering from about 1400 to 1700 ° C. in a nitrogen atmosphere under vacuum, and then gradually cooling in a decarburizing and denitrifying atmosphere. it can.

[0008]

The present invention will be described in more detail with reference to the following examples, which are not intended to limit the present invention. (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, the same WC powder of 0.7 μm, the Ni powder and the Co powder of 1.5 μm, 48 wt%, 37 wt%, 5 wt% and 10 wt%, respectively, after wet mixing,
After embossing and degassing at 1200 ° C. in a vacuum of 10 ⁻² Torr, the nitrogen gas is 155 at a partial pressure of 20 to 70 Torr.
After sintering at 0 ° C. for 1 hour, it was cooled in CO ₂ to prepare Sample 1. The half-value width (hereinafter, referred to as the half-value width) of the peak having the higher intensity of the diffraction curve from the (220) plane of the X-ray Cu-Kα ray B1 structure of Sample 1 is 0.1 mm from the surface. 26 degrees, 0.16 degrees and 62% on the surface wrapping surface
(See FIG. 1). TiCN 37% by weight, TaC 5% by weight, Nb so as to have the same alloy composition as Sample 1.
C2 wt%, WC41 wt%, Ni5 wt%, Co10
% By weight, and sintered under the same conditions as in Sample 1 to prepare Sample 2, and 42% by weight of TiCN, 10% by weight of TaC, 8% by weight of Mo ₂ C, 22% by weight of WC, 6% by weight of Ni, and 12% by weight of Co. Then, sintering was performed under the same conditions as in Sample 1 to prepare Sample 3, and the same embossed compact as in Samples 1 and 2 was sintered at 1450 ° C. under a partial pressure of nitrogen of 7 Torr, and a CO partial pressure of 1
After cooling at 80 Torr, Sample 4 and Sample 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 83 wt% and 9 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 1000 ° C. in a vacuum, the temperature was raised to 1200 ° C. in Ar 10 Torr, and the nitrogen gas partial pressure was 5 Torr.
After sintering at 1450 ° C. for 1 hour, sample 6 was prepared by ultra-slow cooling (0.5 to 5 ° C./min) in 10 Torr of CO ₂ , and slowly cooled in a vacuum (3 to 10 ° C./min) ) To prepare sample 7, which is quenched in Ar (200 Torr, 10-50 ° C /
Min) to prepare Sample 8. Next, 39% by weight of TiCN, 6% by weight of NbC, 40% by weight of WC, 8% by weight of Ni,
The mixture containing 7% by weight of Co was sintered under the same conditions as Samples 6, 7, and 8 to obtain Samples 9, 10, and 11, respectively.
Samples 12 and 13 were prepared by sintering 59% by weight of TiCN, 8% by weight of NbC, 5% by weight of Mo ₂ C, 10% by weight of WC, 10% by weight of Ni and 8% by weight of Co under the same conditions as Samples 1 and 4. , Each (half width at the surface) / (half width at the inside) is measured, and the tool shape C
Table 1 shows the results of preparing NMG432 and subjecting it to the following cutting test for evaluating thermal shock resistance. Samples 1, 2, 9, 10,
In No. 11, WC was precipitated inside the alloy structure.

[0010] Abrasion cutting test tool shape SNMG432 workpiece SCM435 (H _B = 240) Round bar Cutting speed 180 m / min Feed 0.36 mm / rev. Depth of cut 1.5mm Cutting oil Water soluble Cutting time 10min 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 0.20mm / rev . Cutting depth fluctuates from 2.5 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.

Claims (1)

(57) [Claims] Claims: 1. A method for producing a material comprising at least one of carbides, carbonitrides or composite carbonitrides of Ti and at least one transition metal excluding Ti selected from groups 4a, 5a and 6a of the periodic table. 75-95% by weight of the hard phase
5 to 2 bonded phases containing i and Co and unavoidable impurities
5% by weight, and the peak of the B1 structure was 2 in the X-ray diffraction measurement.
In the type of nitrogen-containing sintered hard alloy detected, the peak with the larger intensity detected on the low angle side among the peaks from the same diffraction plane of the two B1 structures in the X-ray diffraction measurement is measured at the alloy surface. A nitrogen-containing sintered hard alloy, wherein the half-value width of the X-ray diffraction peak to be measured is at least 60% and less than 80% of the half-value width of the X-ray diffraction peak measured within 1 mm or more inside the alloy.