JP2580168B2 - Nitrogen-containing tungsten carbide based sintered alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention has a high fracture toughness value and is excellent in strength, abrasion resistance, heat crack resistance, heat shock resistance, oxidation resistance and fracture resistance. Sintered bonding metal, and more particularly to a nitrogen-containing tungsten carbide based sintered metal suitable for wear-resistant tool parts or cutting tool parts.

(Prior Art) Conventionally, as a tungsten carbide-based sintered bond, a nitrogen-free tungsten carbide-based bonded metal represented by a WC-Co alloy or a WC-TiC-TaC-Co alloy has been put to practical use. However, as the demand for higher efficiency in the market increases, there arises a problem that the nitrogen-free tungsten carbide-based sintered binder having a short life is used in applications involving mechanical strength and thermal fatigue resistance. To solve this problem, a large number of nitrogen-containing tungsten carbide-based bonded metals have been proposed.

Representative examples of nitrogen-containing tungsten carbide-based bonded gold include Japanese Patent Publication No. 59-52951 and Japanese Patent Application Laid-Open No. 60-264.
There is No. 7 publication.

(Problems to be Solved by the Invention) Japanese Patent Publication No. 59-52951 discloses a hard solution composed of a B1 type solid solution of WC and one or two carbon nitrides selected from Ti, W and Ta, Nb. In a cemented carbide composed of a phase and a binder phase composed of Fe metal mainly composed of Co, the components of the hard phase are converted into (TiC + TiN) / (TiC + WC + TiN) ratios as carbides and nitrides of Ti and W, and the volume ratio Is in the range of 0.40 to 0.80, and the B1 type solid solution is converted to TiN / (TiC + TiN) ratio or (TiW) N / (TiW) C + (TiW) N ratio, and N in the weight ratio of 0.1 to 0.6 WC is contained in the whole alloy
20 to 80% by weight, 2 to 20% by weight of one or two selected from Ta and Nb in the total alloy, and 7 to 20% by volume of the binder phase mainly composed of Co in the final alloy And that the B1 type solid solution hard phase described herein has an average particle size of 2 μm or less.

Japanese Patent Publication No. 59-52951 discloses that the nitrogen content in a hard phase composed of WC and a B1 type solid solution is controlled within a certain range by setting the (TiC + TiN) / (TiC + WC + TiN) ratio and the nitrogen content in the B1 type solid solution within a certain range. This is a cemented carbide that is superior in wear resistance, toughness, and heat crack resistance during high-speed cutting compared to tungsten carbide-based bonded metal that does not contain tungsten carbide. However, Japanese Patent Publication No. 59-5295
Because the alloy of No. 1 utilizes the grain growth suppressing effect of the B1 type solid solution by nitrogen content, which is conventionally known,
Contains a lot of submicron ultra-fine B1 type solid solution,
There is a problem that the particle size distribution of the B1 type solid solution cannot be made uniform, so that the fracture toughness value is low, and the fracture resistance and wear resistance cannot be sufficiently exhibited.

JP-A-60-110838 discloses a hard phase composition (W, Ti, Ta, Nb) (Cx) in a cemented carbide composed of a hard phase composed of WC and B1 type solid solution and a binder phase of Fe group metal. , Ny), WC is 55% or more and 75% or less by volume%, and TiC is 15% or more and 35%
% Or less, TaC or TaNbC is 5% or more and 25% or less, and x +
y ≧ 1, 0.005 ≦ y ≦ 0.05, and the binding metal is 10% by volume
This is a cemented carbide containing nitrogen in an amount of 18% by volume or less. The alloy disclosed in Japanese Patent Application Laid-Open No. Sho 60-110838 has a structure in which nitrogen is contained to refine the B1 type solid solution and prevent the B1 type solid solution from disappearing on the surface of the alloy. Achieves uniformity between the inside and the surface of the
In addition, the wear resistance and toughness have been successfully improved.
However, the alloy disclosed in JP-A-60-110838 is inferior in oxidation resistance and welding resistance because the nitrogen content is too small, and because the particle size distribution of the B1 type solid solution has not been made uniform. However, there is a problem that the fracture toughness value is low and the thermal shock resistance is poor.

The present invention has solved the above-mentioned problems, and specifically, tungsten carbide and B1 in a certain tissue
Alloy consisting of a sintered solid solution and a binder phase mainly composed of Co, and having a structure in which the average particle size of tungsten carbide and B1 type solid solution is controlled and the particle size distribution of B1 type solid solution is uniform. An object of the present invention is to provide a nitrogen-containing tungsten carbide-based sintered bond having excellent thermal shock resistance, wear resistance and chipping resistance.

(Means for Solving the Problems) The present inventors were examining the effect of adding nitrogen to the tungsten carbide-based sintered binder, and found that the tungsten carbide-based sintered binder became finer due to the inclusion of nitrogen. Using the conventional effect as it is, it is not possible to maximize the properties and performance of the alloy, especially when the B1 type solid solution is made a certain composition, the particle size of tungsten carbide, B1 type solid solution It has been found that various properties and performances of the alloy can be improved by controlling the particle size and the particle size distribution of the B1 type solid solution, and that an appropriate amount of nitrogen can substitute for tantalum carbide. The present invention has been completed based on this finding.

That is, the nitrogen-containing tungsten carbide-based bonded metal of the present invention comprises 5 to 20% by weight of a binder phase containing Co as a main component and 15 to 75% by weight of a first hard phase made of tungsten carbide (Ti _a1 , Zr _a2 , W _b1 , Cr _b2 , Ta _c1 , Nb _c2 , V _c3 ) (C _x , N _y ) _z −
(A) [where a1 is the molar ratio of titanium (Ti) in the metal element, a2 is the molar ratio of zirconium (Zr) in the metal element, and b1 is the molar ratio of tungsten (W) in the metal element. Molar ratio, b2
Is the molar ratio of chromium (Cr) in the metal element, c1 is the molar ratio of tantalum (Ta) in the metal element, c2 is the molar ratio of niobium (Nb) in the metal element, and c3 is vanadium (V) in the metal element. )
X is the molar ratio of carbon (C) in the non-metallic element, y
Represents the molar ratio of nitrogen (N) in the nonmetallic element, z represents the molar ratio of the nonmetallic element to the metal element, and a1 + a2 + b1 + b2 + c1 + c2 + c3 = 1, 0.6 ≧ a1 + a2 ≧ 0.4, 0.1 ≧ a2 / a1 + a2 ≧ 0, 0.4 ≧ b1 + b2 ≧ 0.2, 0.1 ≧ b2 / b1 + b2 ≧ 0, 0.4 ≧ c1 + c2 + c3 ≧ 0.1, 0.3 ≧ c2 / c1 + c2 + c3 ≧ 0, 0.1 ≧ c3 / c1 + c2 + c3 ≧ 0, x + y = 1, 0.3 ≧ y> 0, 1.0 ≧ z ≧ 0.75 In a relationship. And a composition comprising 15 to 80 wt% of a second hard phase comprising a B1 type solid solution and unavoidable impurities, wherein the first hard phase has an average particle size of 1 to 3
μm, the average particle size of the second hard phase is 0.8 to 2.5 μm, and the second hard phase has a particle size of 0.5 μm or less and 20% or less.

The binder phase in the nitrogen-containing tungsten carbide-based bonded gold of the present invention is cobalt in which carbon of a metal element or a nonmetal element in the hard phase is contained to an extent of impurity, or chromium,
It is made of an alloy containing Co as a main component in consideration of corrosion resistance by containing a small amount of vanadium, nickel, or the like. When the content of the binder phase is less than 5% by weight, the total amount of the first hard phase and the second hard phase relatively exceeds 95% by weight, and the fracture toughness value and the strength are reduced. Conversely, when the amount of the binder phase exceeds 20 wt%, the total amount of the first hard phase and the second hard phase becomes relatively less than 80 wt%, and the wear resistance and the heat deformation resistance decrease. For this purpose, the binder phase is defined as 5 to 20% by weight.

In the case of WC having an average particle size of less than 1 μm, the first hard phase in the nitrogen-containing tungsten carbide based sintered binder of the present invention has a reduced thermal shock resistance and a reduced thermal crack resistance, and conversely, the average particle size exceeds 3 μm. In the case of WC, mechanical properties such as hardness and bending strength are reduced. For this reason, the average particle size of the first hard phase is determined to be 1 to 3 μm. The first hard phase is used for WC having an average particle size of 2 to 3 μm, especially for applications where importance is placed on thermal shock resistance and thermal crack resistance, applications where importance is placed on wear resistance, especially room temperature strength or room temperature impact resistance. It is preferable to select WC having an average particle size of 1 to 2 μm for wear-resistant tool parts in which the importance is placed on WC. Also, this first hard phase is
In order to increase the fracture toughness value and the strength, it is preferable to control the uniformity to the particle size distribution.

When the average particle size is less than 0.8 μm, the second hard phase in the nitrogen-containing tungsten carbide-based bonded metal of the present invention has a reduced fracture toughness value and W-Co in the binder phase at the time of practical use at 700 to 800 ° C. Easily precipitates to reduce heat cracking resistance. Conversely, the average particle size of the second hard phase is 2.5 μm
When the ratio exceeds the above range, the dispersion of the second hard phase becomes non-uniform, thereby decreasing the strength and the thermal shock resistance. For this reason, the average particle size of the second hard phase is determined to be 0.8 to 2.5 μm. When the number of particles having a particle size of 0.5 μm or less in the second hard phase exceeds 20%, the dispersion of the second hard phase in the alloy structure becomes poor, and the fracture toughness value and the fracture resistance in particular decrease. . For this reason, it is necessary that the second hard phase having a particle size of 0.5 μm or less be 20% or less. The second hard phase is made by _{(Ti a1, Zr a2, W} b1, Cr b2, Ta c1, Nb c2, V c3) (C x, N y) can be expressed carbonitride in _z. This carbonitride is
Uniform intragranular composition, uniform particle size, B1 with other composition
Titanium and zirconium in metal elements are 0.6 ≧ a1 + a2 ≧ 0.4, and tungsten and chromium are 0.4 ≧ due to prevention of precipitation of mold solid solution [eg (Ti, W) (C, N) etc.] and improvement of various properties and performance of alloy. b1 + b2 ≧ 0.2, tantalum, niobium and vanadium 0.4 ≧ c1 + c2 + c3 ≧ 0.1 and nitrogen in nonmetallic elements 0.3
≧ y> 0, the ratio of the nonmetallic element to the metal element is 1 ≧ z ≧
0.75 (each shows a molar ratio). Especially,
When used as a cutting tool part for high-speed cutting or high-feed cutting for the purpose of high efficiency, titanium and zirconium present in the metal element of carbonitride are 0.6 ≧ a1 + a2 ≧ 0.
5.0.35 ≧ b1 + b2 ≧ 0.25 for tungsten and chromium, 0.25 ≧ c1 + c2 + c3 ≧ 0 for tantalum, niobium and vanadium.
1. It is preferable that the nitrogen present in the nonmetallic element satisfies 0.2 ≧ y ≧ 0.05 (each shows a molar ratio). In addition, the second hard phase composed of carbonitride replaces a certain amount of Ta present in the metal element of the second hard phase with Nb and / or V which is a homologous to Ta. In particular, it is preferable to substitute 30 mol% of Nb and / or 10 mol% of V with respect to Ta from the viewpoint of improvement of heat crack resistance and cost reduction. In addition, W present in the metal element of the second hard phase can be replaced with Mo and / or Cr, which is a homologous to W, to a certain extent. Mol%
Is preferred from the viewpoint of improving oxidation resistance and welding resistance. Alternatively, for Ti present in the metal element of the second hard phase, Zr and / or
Or some amount can be replaced with Hf, especially Ti
Substitution with 10 mol% of Zr is preferable from the viewpoint of improvement in high-temperature strength.

In order to produce the nitrogen-containing tungsten carbide-based bonded metal of the present invention, it is necessary to pay particular attention to the selection of the particle size distribution and the average particle size of the starting material powder and the mixing and pulverization process after blending the starting material powder in a predetermined amount. There is.

First, the starting material powder is preferably fine in terms of facilitating sintering.
In particular, it is necessary to prevent the second hard phase from becoming too fine due to the effect of suppressing the grain growth. For this purpose, the starting material powder has an average particle size of at least 1 μm, preferably the desired average particle size, of various starting material powders composed of carbides, nitrides, and carbonitrides necessary for forming the second hard phase. It is better to select one that is about 1.5 to 3 times as large as. In addition, the particle size distribution of these starting material powders, particularly the particle size distribution of the various starting material powders for forming the second hard phase described above, is as uniform as possible by, for example, treating with a powder and particle classifier. It is preferable to select one.

Next, in the mixing and pulverizing step, it is necessary to consider the average particle size and the particle size distribution of the starting raw material powder to be used. It is necessary to sufficiently suppress the type and amount of the organic solvent such as acetone, benzene, and hexane, the type, shape and amount of the ball and the like, and the mixing and pulverizing time.

The drying, granulation and sieving, forming and sintering steps after mixing and pulverization may be performed by a method used for conventional tungsten carbide-based sintered gold, for example, in a reduced pressure nitrogen atmosphere or in a vacuum. it can.

(Action) In the nitrogen-containing tungsten carbide-based bonded metal of the present invention, the second hard phase of the carbonitride containing titanium, tungsten and tantalum has an optimum particle size and a uniform particle size distribution. Since the particle size of the second hard phase and the first hard phase are almost the same size, the second hard phase and the first hard phase have an excellent mutual dispersion state. Things. Further, the relation between the mutual dispersion state of the first hard phase and the second hard phase and the relation of the respective particle diameters is such that the binder phase in the sintered metal of the present invention is uniformly distributed at the grain boundaries, that is, the mean free path is uniform. That is the effect. From these facts, the sintered bonding metal of the present invention is an alloy having very few defects in the alloy structure.

Example 1 Example 1 WC powder having an average particle size of 3.0 μm, average particle sizes of 1.5 μm, 2.5 μm,
5.0μm three kinds of (W, Ti) C powder, average particle size 1.0μm
TaC powder, TiN powder with average particle size 1.5μm, average particle size 1.4μm
WC-27% (W, Ti) C-12% TaC-2% A comparative product 4 containing no nitrogen was mixed with a composition of TiN-8.5% Co (wt%) and a composition of WC-27% (W, Ti) C-12% TaC-8% Co (wt%), respectively. . Each of the blended samples was mixed and pulverized in a hexane solvent using a stainless steel container and a cemented carbide ball, followed by paraffin mixing, drying and 1 ton / cm ²
Molded under pressure and then deparaffinized. The green compact was placed in a vacuum furnace and placed in a vacuum of 5 × 10 ^-2 Torr,
Sintering was performed at 80 ° C to 1420 ° C for 1 hour. Of the starting raw material powders used for each sample, it differs depending on the sample (W,
Table 1 shows the type of Ti) C powder, the grinding time and the sintering temperature. In particular, the pulverization method for the products 1, 2, and 3 of the present invention is the total time of mixing and pulverizing only powder other than WC powder for 24 hours and then adding and mixing WC powder. The hardness, bending strength and fracture toughness of each sintered alloy obtained in this way were determined, and the results are shown in Table 2. Also, the structure was observed with a scanning electron microscope and an X-ray microanalyzer, and the grain size of the first hard phase, the grain size of the second hard phase, and the content of the grain size of 0.5 μm or less in each sintered metal were obtained. Also shown in Table 2. The second hard phases of the present invention products 1, 2, 3 and comparative products 1, 2, 3 obtained here consist of (Ti _0.53 , W _0.27 , Ta _0.20 ) (C _0.90 , N _0.10 ) _0.90. Was.

Example 2 Using the respective samples obtained in Example 1, a cutting test was performed under the following turning and milling conditions, and the results are shown in Table 3.

Turning Test conditions Workpiece S48C (H _B 218) chip shape SNP432 Cutting speed 100 m / min Feed rate 0.3 mm / rev Depth of cut 1.5mm Cutting time 5min milling cutting test conditions Workpiece SCM440 (H _B 270) chip shape SNP432 cutting Speed 150m / min Depth of cut 2.0mm Feed amount per tooth 0.2mm / tooth Life judgment Cutting length to chipping Example 3 WC powder with average particle size of 1.5 μm, 3.0 μm, 5.0 μm, average particle size
1.5 μm, 3.0 μm (W, Ti, Ta, Nb) C powder, average particle size 1.5
μm TiN powder and Co powder having an average particle diameter of 1.4 μm were used as starting materials, and the products 4, 5, 6, 7 of the present invention and the comparative products 5, 6, 7 out of the present invention were subjected to WC-60% (W , Ti, Ta, Nb) C-3% TiN-8% Co (wt%) and nitrogen-free comparative product 8 with WC-60% (W, Ti, Ta, Nb) C-8% Co (% By weight). Each of the blended samples was used in Example 1
It was burned through the same process as above. Table 4 shows the types of WC powder and the types of (W, Ti, Ta, Nb) C powder, and the pulverization time and sintering time which differ among the starting material powders used for each sample. The hardness, bending strength, and fracture toughness of each of the sintered alloys thus obtained were determined, and the results are shown in Table 5. Also, the structure was observed with a scanning electron microscope and an X-ray microanalyzer, and the grain size of the first hard phase, the grain size of the second hard phase, and the content of the grain size of 0.5 μm or less in each sintered metal were obtained. Also shown in Table 5. The product of the present invention obtained here 5, 6,
The second hard phase of No. 7 and Comparative Products 5, 6, 7 consisted of [Ti _0.55 , W _0.33 , (Ta · Nb) _0.12 ] (C _0.87 , N _0.13 ) _0.95 . This second
Nb in the hard phase was Nb / Ta + Nb = 10 mol%.

Example 4 Using each of the samples obtained in Example 3, a cutting test was performed under the following turning conditions and interrupted cutting conditions, and the results are shown in Table 6.

Turning Test conditions Workpiece S48C (H _B 230) chip shape SNP432 Cutting speed 160 m / min Feed rate 0.3 mm / rev Depth of cut 1.5mm Cutting time 7min interrupted cutting test conditions Workpiece S48C (H _B 230) 4 present slot entrance Insert shape SNP432 Cutting speed 100m / min Depth of cut 1.5mm Feed speed 0.05mm / rev After 4000 interrupted cuts for the first time
Compared by feed speed at the time of loss.

Example 5 WC powder having an average particle size of 3.0 μm and (W, T
i) C powder, TaC powder with average particle size of 1.0 μm, average particle size of 1.5 μm
m, TiN powder and Co powder with an average particle size of 1.4 μm as starting materials, using the products 8, 9 of the present invention and comparative products deviating from the present invention.
9, 10 and 11 were blended as shown in Table 7, respectively. Of these, products 8 and 9 of the present invention were manufactured by the same method as that of product 1 of the present invention in Example 1, and comparative products 9, 10, and 11 were manufactured by the same method as that of product 1 of the first embodiment. It was a sintered alloy. The hardness, transverse rupture strength, and fracture toughness of the products 8, 9 of the present invention and the comparative products 9, 10, 11 thus obtained were examined in the same manner as in Example 1. The results are shown in Table 8. Further, each hard phase was examined in the same manner as in Example 1, and the results are shown in Table 9.

Example 6 A cutting test was performed on each of the samples obtained in Example 5 in the same manner as in the turning test conditions and the milling test conditions in Example 1.
The results are shown in Table 10.

(Effects of the Invention) From the above results, the nitrogen-containing tungsten carbide-based sintered metal of the present invention is a conventional tungsten carbide having a trade-off relationship in that one of the wear resistance and the fracture resistance is improved while the other is reduced. It has succeeded in improving both wear resistance and chipping resistance in a well-balanced manner with respect to the base bonding metal. More specifically, the sintered metal of the present invention has an improved fracture resistance of about 20 to 29% as compared with the conventional tungsten carbide-based sintered metal, which is particularly excellent in fracture resistance but tends to be inferior in wear resistance. However, there is an effect that the wear resistance is improved by about 36 to 56%. Conversely, compared to the conventional tungsten carbide-based sintered bond which is excellent in wear resistance but tends to be inferior in fracture resistance, the sintered bond of the present invention has almost no difference in wear resistance, There is a result that the fracture resistance is improved by 113 to 183%. From this, the sintered metal of the present invention is:
It is excellent in reliability and is an industrially useful material that can be used as a tool for NC machines and unmanned processing machines or as a tool part for high efficiency.

Claims (1)

(57) [Claims] (1) A binder phase containing Co as a main component in an amount of 5 to 20% by weight and a first hard phase made of tungsten carbide in an amount of 15 to 75% by weight and the following (A):
A composition component comprising 15 to 80 wt% of a second hard phase composed of a BI-type solid solution represented by the formula and unavoidable impurities, wherein the first hard phase has an average particle size of 1 to 3 μm and the average of the second hard phase is The particle size is
A nitrogen-containing tungsten carbide-based sintered alloy excellent in fracture resistance, characterized in that the second hard phase is 0.8 to 2.5 µm and the particle size of 0.5 µm or less is 20% or less. (Ti _a1 , Zr _a2 , W _b1 , Cr _b2 , Ta _c1 , Nb _c2 , V _c3 ) (C _x , N _y ) _z −−
(A) [where a1 is the molar ratio of titanium (Ti) in the metal element, a2 is the molar ratio of zirconium (Zr) in the metal element, and b1 is the molar ratio of tungsten (W) in the metal element. Molar ratio, b2
Is the molar ratio of chromium (Cr) in the metal element, c1 is the molar ratio of tantalum (Ta) in the metal element, c2 is the molar ratio of niobium (Nb) in the metal element, and c3 is vanadium (V) in the metal element. )
X is the molar ratio of carbon (C) in the non-metallic element, y
Represents the molar ratio of nitrogen (N) in the nonmetallic element, z represents the molar ratio of the nonmetallic element to the metal element, and a1 + a2 + b1 + b2 + c1 + c2 + c3 = 1, 0.6 ≧ a1 + a2 ≧ 0.4, 0.1 ≧ a2 / a1 + a2 ≧ 0, 0.4 ≧ b1 + b2 ≧ 0.2, 0.1 ≧ b2 / b1 + b2 ≧ 0, 0.4 ≧ c1 + c2 + c3 ≧ 0.1, 0.3 ≧ c2 / c1 + c2 + c3 ≧ 0, 0.1 ≧ c3 / c1 + c2 + c3 ≧ 0, x + y = 1, 0.3 ≧ y> 0, 1.0 ≧ z ≧ 0.75 In a relationship. ]