JPS6122014B2 - - Google Patents

Description

[Detailed description of the invention]

This invention is a sintered cemented carbide based on tungsten carbide (WC) that provides excellent wear resistance without reducing the excellent impact resistance of conventional tungsten carbide (WC)-based sintered cemented carbide.
This invention relates to a method for producing a base sintered cemented carbide. Conventionally, WC-based sintered cemented carbide has been used as a typical material for cutting tools along with high-speed steel, and for applications that require particularly wear resistance, it has been used as a material containing TiC, which has high hardness. WC−TiC−TaC
-Co-based sintered cemented carbide is used. However, in the conventional WC-based sintered cemented carbide mentioned above, wear resistance and impact resistance are in a contradictory relationship.
For example, if the wear resistance is increased by increasing the TiC content or decreasing the Co content, the impact resistance will decrease; on the other hand, if the TiC content is decreased,
When the impact resistance is improved by increasing the Co content,
Abrasion resistance began to decline, and it was extremely difficult to achieve both impact resistance and abrasion resistance. In addition, in recent years, the conventional WC-based sintered cemented carbide mentioned above,
Incorporation of new components such as TiN and TaN is being considered, but this also improves impact resistance but reduces wear resistance. It hasn't become a thing. On the other hand, looking at the grain size of the conventional WC-based sintered cemented carbide mentioned above, fine-grained alloys with an average grain size of 1 to 2 μm are superior to medium-grained alloys with an average grain size of 3 to 4 μm. It has high room temperature hardness and transverse rupture strength, and exhibits excellent wear resistance and impact resistance in low-speed cutting. However, in high-speed cutting, medium-grained alloys have superior properties compared to fine-grained alloys. Furthermore, coarse-grained alloys with an average crystal grain size of 4 to 6 μm have superior cleaving resistance compared to medium-grained alloys and fine-grained alloys, but they cannot be sintered without being sufficiently crushed. Therefore, the above-mentioned coarse-grained alloys are used more for hot wear resistance or mining tools than for cutting, and furthermore, any crystal grains are In order to exhibit sufficient performance in specific applications, it is currently believed that a narrow grain size distribution is best for alloys with different diameters. In this way, conventional WC-based sintered cemented carbide, which has particularly excellent wear resistance, contains a large amount of TiC, which has high heat resistance, and has an average grain size of 3.
A medium-grained alloy of ~4 μm is used, and for cutting cast iron, a fine-grained alloy containing a small amount of TiC or no TiC, low Co content, and an average grain size of 1 to 2 μm is used. However, it cannot be said that it is a material that exhibits the desired high performance in all applications, and there is a desire to develop a material with better cutting properties, especially from the point of view of extending the life of cutting tools. From the above-mentioned viewpoint, the present inventors aimed to obtain a material that has both wear resistance and impact resistance and exhibits excellent properties especially when used as a cutting tool. As a result of conducting research on Co-based sintered cemented carbide, focusing in particular on its grain size, we found that (a) ultra-coarse grains with an average grain size of 7 μm or more;
When TiC crystals are uniformly dispersed in the structure so as to account for 1 to 3% by volume in total, the excellent properties of the ordinary WC-based sintered cemented carbide, which does not contain the ultra-coarse grained TiC crystals, can be improved. It is possible to greatly improve wear resistance without reducing impact resistance. (b) The improvement in wear resistance due to the presence of the ultra-coarse-grained TiC crystals is due to the fact that TiC is harder than WC, chemically stable, and has excellent heat resistance. The smaller the crystal grain size, the more activated TiC becomes. Therefore, fine grains cannot provide the chemical stability and heat resistance inherent to TiC, and only ultra-coarse grains can provide excellent chemical stability and heat resistance. To be able to have sex. In addition to the properties shown above, the ultra-coarse-grained TiC has the property that the amount of solid solution in the binder phase is small, so it exists in the sintered structure in a form close to the particle size of the starting material powder. Therefore, it is most suitable as an ultra-coarse grain. It must be based on the reasons shown above. (c) Part of the TiC component in the ultra-coarse-grained TiC crystals is controlled in a periodic manner in a relative proportion of less than 2 to 50 mol% (therefore, the relative proportion of TiC is 50 to 98 mol%). One or two of the carbides and nitrides of metals listed in Tables 4a, 5a, and 6a.
When substituted with more than one component, while retaining the excellent wear resistance provided by the TiC,
Impact resistance will be further improved. The findings shown in (a) to (c) above were obtained. Therefore, this invention was made based on the above knowledge, and it is based on the above-mentioned knowledge.
When manufacturing sintered cemented carbide, part or all of TiC is added to the total proportion of 1 to 30% by volume.
Average crystal grain size: 7 μm
TiC crystals having the above, and one or more components of TiC and carbides and nitrides of metals in groups 4a, 5a, and 6a of the periodic table (hereinafter referred to as metal carbon/nitrides). complex compound crystals (however
By uniformly dispersing these ultra-coarse crystals in the structure, it has both excellent wear resistance and impact resistance. It has particular characteristics. Next, in the manufacturing method of the WC-based sintered cemented carbide of this invention, we will explain the reason why the average crystal grain size and content of ultra-coarse grain crystals, as well as the amount of metal carbon/nitride replacement, are limited as described above. do. (a) Average grain size If the average grain size is less than 7 μm, the excellent chemical stability and heat resistance of TiC itself cannot be fully demonstrated, and as a result, the desired excellent wear resistance cannot be achieved. Therefore, it is necessary to have an average crystal grain size of 7 μm or more. (b) Content If the content is less than 1% by volume, the desired excellent wear resistance cannot be imparted, while if the content exceeds 30% by volume, the ultra-coarse crystals will form a skeleton. The content was determined to be 1 to 30% by volume because the impact resistance deteriorates. (c) Amount of metal replaced by carbon/nitride. As mentioned above, when composite compound crystals consisting of ultra-coarse grained TiC crystals partially replaced with metal carbon/nitride are dispersed in the structure, the excellent wear resistance brought about by the TiC component can be improved. While holding it,
Since the impact resistance of the alloy is further improved, especially when even higher impact resistance is required, the composite compound crystals are dispersed in the alloy structure as necessary. If the proportion of metal carbon/nitride is less than 2 mol%, no further improvement in impact resistance can be obtained, while if the proportion exceeds 50 mol%, the relative proportion of TiC component is 50 mol%. %, the chemical stability and heat resistance provided by the TiC component cannot be fully demonstrated, and as a result, it becomes difficult to secure the desired wear resistance. The substitution ratio of metal with carbon/nitride was set at 2 to 50 mol%. In addition, uniform dispersion of ultra-coarse grain crystals having an average grain size of 7 μm or more in the alloy structure is achieved by using coarse powder with an average grain size of 9 μm or more as the raw material powder and blending it as part of the raw material powder. This is possible by thoroughly mixing the entire raw material powder. Therefore, if the average grain size of the raw material powder is less than 9 μm, ultra-coarse crystals with an average grain size of 7 μm or more cannot be ensured in the alloy structure. Next, the method for producing the WC-based sintered cemented carbide of the present invention will be explained with reference to Examples. Example 1 Corresponds to JIS classification P10 with a component composition of 40% WC - 40% TiC - 10% TaC - 10% Co (volume %)
In the WC-based sintered cemented carbide, 30% by volume of the 40% TiC content is made up of ultra-coarse-grained TiC crystals with an average grain size of 7 μm. A sintered cemented carbide (hereinafter referred to as the alloy of the present invention) 1 and a comparative WC-based sintered cemented carbide (hereinafter referred to as a comparative alloy) 1 composed of the same amount of coarse-grained TiC crystals having an average crystal grain size of 5 μm were prepared. , were manufactured by the operations shown below. That is, first, as starting raw material powders, WC powder with an average particle size of 2.5 μm and (W,Ti)− with an average particle size of 1.2 μm were used.
C powder, 1.5 μm TaC powder, and 1.2 μm TaC powder
Co powder is used, and these raw powders are 40% WC−
The composition of 10% TiC - 10% TaC - 10% Co (volume %) was blended and mixed by wet grinding in a ball mill for 72 hours.The balls in the ball mill were then taken out and the resulting mixed powder was mixed. Divide the mixture into two, and add 30% by volume of ultra-coarse TiC powder with an average particle size of 9 μm and 5 μm of average particle size to each mixed powder.
Coarse-grained TiC powder having a particle size of m was separately blended and mixed for 5 hours. Thereafter, Invention Alloy 1 and Comparative Alloy 1 were manufactured, respectively, according to a conventional powder metallurgy method. Cutting chips with shapes conforming to the CIS (Cemented Carbide Tool Association Standard) SNP432 were manufactured from the resulting Inventive Alloy 1, Comparative Alloy 1, and JISP10 alloy, and the workpiece material: SNCM-8 (hardness H _B : 220), Chip honing: 0.03mm, Cutting speed: 200m/min, Feed: 0.3mm/rev., Depth of cut: 1.5mm, Cutting time: 10min, A continuous cutting test was conducted under the following conditions. The flank wear (flank wear width) and crater wear (rake face wear depth) of the blade were measured, and furthermore, work material: SNCM-8 (hardness H _B : 280), chip honing: none, cutting speed. An interrupted cutting test was conducted under the following conditions: 140 m/min, feed: 0.3 mm/rev., depth of cut: 2 mm, cutting time: 3 min. In this interrupted cutting test, how many of the 6 cutting edges (chips) The occurrence of defects was measured. The results of these measurements are shown in Table 1. Note that Table 1 also shows the average crystal grain size of TiC crystals in each of the above alloys. As shown in Table 1, in continuous cutting, the cutting tip made of Invention Alloy 1 having ultra-coarse grained TiC crystals, the cutting tip made of Comparative Alloy 1 having coarse grained TiC crystals, and the cutting chip made of P10 alloy. It shows superior wear resistance compared to cutting chips, and in the interrupted cutting test, it is clear that it shows excellent impact resistance equivalent to P10 alloy, which has excellent impact resistance, and Comparative Alloy 1. .

[Table] Example 2 Equivalent to JIS classification; 20 with a component composition of 58% WC - 20% TiC - 10% TaC - 12% Co (volume %)
When producing WC-based sintered cemented carbide, part of the TiC powder as the starting raw material powder is
(Ti, Ta, Nb)C with a composition of TiC/TaC/NbC=85 mol%/10 mol%/5 mol%
Powder: Alloy 2 of the present invention was produced by the usual powder metallurgy method in the same manner as in Example 1, except that the powder was composed of 10% by volume. Next, regarding the resulting invention alloy 2 and the above p20 alloy, workpiece material: SNCM-8 (hardness _HB : 220), chip honing: 0.03 mm, cutting speed: 150 m/min, feed: 0.3 mm /rev., Depth of cut: 1.5mm, Cutting time: 10min, Continuous cutting test under the following conditions: Work material: SNCM-8 (hardness H _B : 280), Chip honing: None, Cutting speed: 120m/ Intermittent cutting tests were conducted under the following conditions: min, feed: 0.4 mm/rev., depth of cut: 2.0 mm, cutting time: 3 min, and the test results were measured in the same manner as in Example 1, and are shown in Table 2. Ta.

[Table] As shown in Table 2, the present invention alloy 2 is:
It is clear that it shows superior wear resistance in continuous cutting compared to p20 alloy, and shows excellent impact resistance equivalent to p20 in interrupted cutting. Example 3 Corresponds to JIS classification p30 with a component composition of 69% WC - 14% TiC - 3% TaC - 14% Co (volume %)
When producing a WC-based sintered cemented carbide, 1% by volume of TiC powder as a starting raw material powder has an average particle size of 15 μm, and TiC/WC = 80 mol%/20
Inventive alloy 3 was produced by the usual powder metallurgy method in the same manner as in Example 1, except that (Ti, W)C powder having a composition of mol % was substituted. Next, regarding the above-mentioned invention alloy 3 and p30 alloy, work material: SNCM-8 (hardness _HB : 220), chip honing: 0.03 mm, cutting speed: 100 m/min, feed: 0.4 mm/rev., Continuous cutting test under the conditions of depth of cut: 2.0mm, cutting time: 10min, work material: SNCM-8 (hardness H _B : 280), chip honing: none, cutting speed: 100m/min, feed : 0.4 mm/rev., depth of cut: 2.0 mm, cutting time: 3 min, respectively. Intermittent cutting tests were conducted under the following conditions, and these test results were used in the third test in the same manner as in Example 1.
Shown in the table. As is clear from the results shown in Table 3,
In the case of this example as well, the alloy 3 of the present invention was conventionally P30
It exhibits superior wear resistance and impact resistance compared to alloys.

[Table] Example 4 Corresponds to JIS classification p10 with a component composition of 50% WC - 35% TiC - 6% TaC - 9% Co (volume %)
When producing a WC-based sintered cemented carbide, 20% by volume of TiC powder as a starting raw material powder has an average particle size of 10 μm, and TiC/ZrN = 95 mol%/5.
Alloy 4 of the present invention was manufactured by a conventional powder metallurgy method under the same manufacturing conditions as in Example 1, except that it was composed of (Ti, Zr)CN powder having a composition of mol %. The resulting invention alloy 4 and the above P10
A cutting test was conducted on the alloy under the same conditions as in Example 1, and the test results were as follows.
As shown in the table together with the average grain size of the (Ti,Zr)CN crystals, it is clear that the alloy 4 of the present invention exhibits superior wear resistance and impact resistance compared to the conventional p10 alloy.

[Table] Example 5 Corresponds to JIS classification p20 with a component composition of 58% WC - 27% TiC - 3% TaC - 12% Co (volume %)
When producing WC-based sintered cemented carbide, 15% by volume of TiC powder as a starting material powder has an average particle size of 20 μm, and TiC/VN/HfC = 94 mol%/5 mol%/1 mol. % composition (Ti,
Inventive alloy 5 was produced by the usual powder metallurgy method in the same manner as in Example 1, except that it was composed of V,Hf)CN powder. Next, a cutting test was conducted on the resulting alloy 5 of the present invention and the above p20 alloy under the same conditions as in Example 1, and the results shown in Table 5 were obtained.

[Table] As shown in Table 5, the present invention alloy 5, in which ultra-coarse grained (Ti, V, Hf)CN crystals having an average grain size of 15 μm are uniformly dispersed in the structure, has a conventional p20
It is clear that the material exhibits superior cutting properties in both continuous cutting and interrupted cutting compared to alloys. Example 6 Corresponds to JIS classification p30 with a component composition of 67% WC - 14% TiC - 5% TaC - 14% Co (volume %)
In the production of WC-based sintered cemented carbide, 5% by volume of TiC powder as a starting raw material powder has an average particle size of 12 μm, and TiC/TiN/ _Mo2C =60mol%/20mol%/20 (Ti,
Invention alloy 6 was produced under the same production conditions as in Example 1, except that Mo)CN powder was substituted. Subsequently, continuous cutting tests and interrupted cutting tests were similarly conducted on the invention alloy 6 and the p30 alloy under the same conditions as in Example 1, and the results shown in Table 6 were obtained.

[Table] In the case of this Example 6, as is clear from the results shown in Table 6, Invention Alloy 6 had excellent wear resistance in the continuous cutting test, similar to Invention Alloys 1 to 5 above. It also shows excellent impact resistance in interrupted cutting tests. Example 7 Corresponds to JIS classification p20 with a component composition of 58% WC - 20% TiC - 10% TaC - 12% Co (volume %)
When producing WC-based sintered cemented carbide, 5% by volume of TiC powder as starting raw material powder is
Using TiC powder with a particle size of 15 μm, 5% by volume of TiC powder and 5% by volume of TaC powder, also used as raw material powders, are made to have an average particle size of 10 μm, and TiC/TaN=
(Ti, Ta) with a composition of 90 mol%/10 mol%
Invention Alloy 7 was produced under the same operating conditions as in Example 1 for producing Invention Alloy 1, except that it was composed of CN powder. Inventive alloy 7 obtained as a result and the above-mentioned conventional alloy
A cutting test was conducted on the p20 alloy under the same conditions as in Example 2, and the test results are shown in Table 7.

[Table] As shown in Table 7, the average grain size is 11μm.
Coarse TiC crystals with
It is clear that the alloy 7 of the present invention, in which Ta) CN crystals are uniformly dispersed in the structure, exhibits superior cutting properties, especially in continuous cutting, compared to the conventional p20 alloy. As mentioned above, the WC-based sintered cemented carbide produced by the method of the present invention has excellent impact resistance equivalent to or better than the conventional WC-TiC-TaC-Co-based sintered cemented carbide. In addition to having excellent impact resistance, it also has significantly superior wear resistance that cannot be obtained with the conventional WC-based sintered cemented carbide, making it suitable for use in cutting tools. It also exhibits excellent performance when used for wear resistance.

Claims (1)

[Claims] 1. When producing a WC-TiC-TaC-Co based sintered cemented carbide, coarse TiC powder with an average particle size of 9 μm or more is blended and mixed as part of the raw material powder. Therefore, by uniformly dispersing ultra-coarse TiC crystals with an average grain size of 7 μm or more in the alloy structure at a ratio of 1 to 30% by volume, excellent wear resistance and impact resistance can be achieved. A method for producing a tungsten carbide-based sintered cemented carbide, comprising: 2 When producing WC-TiC-TaC-Co based sintered cemented carbide, coarse TiC with an average particle size of 9 μm or more and metals from groups 4a, 5a, and 6a of the periodic table are used as part of the raw material powder. Composite compound powder with one or more components of carbides and nitrides (TiC: 50
By blending and mixing the ultra-coarse composite compound crystals with an average crystal grain size of 7 μm or more at a ratio of 1 to 30 mol% by volume, 1. A method for producing a tungsten carbide-based sintered cemented carbide, which is characterized by providing excellent wear resistance and impact resistance. 3 When manufacturing WC-TiC-TaC-Co based sintered cemented carbide, as part of the raw material powder, the average particle size is 9.
Coarse TiC powder of μm or more, and composite compound powder of TiC and one or more components of carbides and nitrides of metals in groups 4a, 5a, and 6a of the periodic table (however, TiC: 50~ By blending and mixing 98 mol% of ultra-coarse grains with an average grain size of 7 μm or more,
A tungsten carbide-based sintered carbide characterized by having excellent wear resistance and impact resistance by uniformly dispersing TiC crystals and the above composite compound crystals at a ratio of 1 to 30% by volume. Alloy manufacturing method.