JPS6122015B2 - - Google Patents

Description

[Detailed description of the invention]

This invention is a WC-based sintered carbide that has impact resistance equivalent to or better than that of conventional tungsten carbide (WC)-based sintered cemented carbide, and also has excellent wear resistance. This relates to a method for producing alloys. Conventionally, WC-based sintered cemented carbide has been used as a typical material for cutting tools, along with high-speed steel, and in particular, for applications that require wear resistance, for example, TiC, which has high hardness, has been used. WC-TiC-TaC-Co alloys are used, which contain a large amount of Co, a binder phase-forming component with low hardness, while reducing the content of Co. For applications that require impact resistance, TiC
The content of Co was decreased and the content of Co was increased.
WC-TiC-TaC-Co alloys and WC-Co alloys are used. In this way, in the conventional WC-based sintered cemented carbide mentioned above, wear resistance and impact resistance are in a contradictory relationship.
As mentioned above, increasing wear resistance by increasing the TiC content or decreasing the Co content causes a decrease in impact resistance, while decreasing the TiC content or decreasing the Co content If the impact resistance is increased by increasing the abrasion resistance, the abrasion resistance decreases, and it is therefore extremely difficult to obtain a product that has both abrasion resistance and impact resistance. Furthermore, in recent years, it has been considered to add new components such as TiN and TaN to the conventional WC-based sintered cemented carbide, but this also improves impact resistance but reduces wear resistance. As a result, it does not have excellent properties in both abrasion resistance and impact resistance. 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 hardness and transverse rupture strength at room temperature, 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. It comes to show. Furthermore, aggregate grain alloys with an average crystal grain size of 4 to 6 μm have superior creep resistance compared to medium grain alloys and fine grain alloys, but because they must be sintered without being sufficiently crushed, There is a manufacturing problem in that the sinterability is poor, and therefore, the above-mentioned grouped grain alloys are used more for hot wear resistance or mining tools than for cutting, and furthermore, alloys of any grain size Currently, in order to exhibit sufficient performance in a specific application, it is considered that a narrow distribution of crystal grain size is better. Thus, an alloy that exhibits excellent cutting properties in terms of both warp wear resistance and impact resistance over a wide range from low-speed cutting to high-speed cutting has not been developed in terms of either alloy composition or grain size. . 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 research on Co-based sintered cemented carbide, focusing in particular on its alloy structure, we found that (a) ultra-coarse grains with an average grain size of 7 μm or more;
TiC crystal: 1-30% by volume, average diameter: 3-10μ
When the binder phase pool with m is uniformly dispersed in the structure, the impact resistance is equal to or higher than that of ordinary WC-based sintered cemented carbide in which the ultra-coarse grained TiC crystals and binder phase pool are not present. and excellent wear resistance.
Note that the binder phase pool refers to a granular binder phase dispersed in the tissue. (b) The reason for improving wear resistance is that TiC is harder than WC, is chemically stable, and has excellent heat resistance. The smaller the crystal grain size, the more activated TiC becomes, and therefore fine grains cannot provide the chemical stability and heat resistance inherent to TiC, and become ultra-coarse grains with an average grain size of 7 μm or more. For the first time, it is possible to ensure excellent chemical stability and heat resistance. In addition to the above-mentioned characteristics, the ultra-coarse grained TiC has the characteristic 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 raw material powder. Because of this, it is most suitable as an ultra-coarse grain. The reasons listed above can be cited. (c) The reason for the improvement in impact resistance is that the binder phase pool uniformly dispersed in the alloy structure prevents the propagation of cracks and relieves stress, resulting in a significant improvement in fracture toughness. It is assumed that this is due to the improvement. (d) Part of the TiC component in the ultra-coarse-grained TiC crystals is controlled in a periodic manner in a relative proportion of 2 to 50 mol% (therefore, the relative proportion of TiC is 50 to 98 mol%). Replacement with one or more of the carbides and nitrides of metals in Groups 4a, 5a, and 6a of Table 1 provides improved impact resistance while retaining the excellent wear resistance provided by TiC. To further improve sexuality. The findings shown in (a) to (d) 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, coarse grains with an average grain size of 7 μm or more are added to the structure.
TiC crystals and one or more components of TiC and carbides and nitrides of metals from groups 4a, 5a, and 6a of the periodic table (hereinafter referred to as metals) having an average grain size of 7 μm or more. Composite compound crystal with carbon/nitride (TiC: 50-98
(mol% content) or both: 1 to 30
By uniformly dispersing the binder phase pool with an average diameter of 3 to 10 μm, it has both excellent abrasion resistance and impact resistance.
This is a unique method for manufacturing WC-based sintered cemented carbide. Next, in the method for producing the WC-based sintered cemented carbide of the present invention, the content and average crystal grain size of ultra-coarse grains, the average diameter of the binder phase pool, and the amount of carbon/nitride substitution in the metal are determined. The reason for the above limitation will be explained. (a) Content of ultra-coarse crystals If the content is less than 1% by volume, the desired excellent impact resistance cannot be secured;
If the content exceeds 1% by volume, the ultra-coarse crystals tend to form skeletons, resulting in deterioration of impact resistance. Therefore, the content was set at 1 to 30% by volume. (b) Average grain size of ultra-coarse crystals If the average grain size is less than 7 μm, TiC itself cannot fully demonstrate its excellent chemical stability and heat resistance, resulting in improved wear resistance. Since it would be difficult to measure the thickness, the lower limit was set at 7 μm. 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, the average particle size of the raw material powder is 9
Below μm, the average grain size in the alloy structure is 7
Ultra-coarse crystals of μm or more cannot be secured. (c) Average diameter of the binder phase pool If the average diameter is less than 3 μm, crack propagation cannot be completely prevented. On the other hand, if the average diameter exceeds 10 μm, the wear resistance will be significantly reduced, so the average diameter was set at 3 to 10 μm. In addition, the average diameter uniformly distributed in the alloy structure:
A binder phase pool of 3 to 10 μm is made by blending the starting raw material powder into a predetermined composition, pulverizing and mixing it wet, and drying it to form a mixed powder, which is then added with PVA.
(polyvinyl alcohol), pyryl wax, stearic acid, paraffin, etc., and has an average particle size of 3 to 10 μm, in an amount of 3 to 7% by weight. After mixing without pulverization, it is press-formed into a compact, which is pre-sintered to form pores in the pre-sintered compact, and then this pre-sintered compact is When the material is sintered, the voids are filled with the binder phase forming component, thereby forming the voids. Furthermore, the reason why the amount of organic compound powder added was set at 3 to 7% by weight as described above is because if the amount added is less than 3% by weight, the binder phase pool existing in the alloy structure is too small. This is because it is not possible to secure the desired excellent impact resistance, and on the other hand, if the amount added exceeds 7% by weight, the binder phase pool becomes too large and the wear resistance decreases. It is. In addition, in the conventional powder metallurgy method, organic compounds are added during wet grinding and mixing of the blended powder, and as a result, they become finely dispersed in the mixed powder, so the calcination after pre-sintering is There are no pores in the aggregate. (d) Amount of substitution As mentioned above, when a composite compound crystal consisting of ultra-coarse-grained TiC crystals partially replaced with metal carbon/nitride is dispersed in the structure, the excellent effects brought about by the TiC component The impact resistance of the alloy is further improved while maintaining the same wear resistance. Therefore, when particularly high impact resistance is required, the above-mentioned composite compound crystals may be added to the alloy structure as necessary. However, the proportion of metal carbon/nitride in the composite compound is 2 mol%.
If the proportion is less than 50 mol%, no further improvement in impact resistance can be obtained; on the other hand, if the proportion exceeds 50 mol%,
If the relative proportion of the TiC component is less than 500 mol%, the chemical stability and heat resistance provided by the TiC component cannot be fully exhibited, and as a result, the desired wear resistance cannot be achieved. Since this becomes difficult, the substitution ratio of metal carbon/nitride in the composite compound crystal was set at 2 to 50 mol%. 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, which is a part of the 40% by volume TiC content, is composed of ultra-coarse-grained TiC crystals having an average grain size of 7 μm,
Further, the present invention WC-based sintered cemented carbide in which a Co pool having an average diameter of 3 μm was present (hereinafter referred to as the present invention alloy) 1, the above p10 alloy, TiC: 30
Comparative WC-based sintered cemented carbide (hereinafter referred to as comparative alloy) 1 composed of ultra-coarse-grained TiC crystals with an average grain size of 7 μm, and a Co pool with an average grain size of 3 μm in the above p10 alloy. Comparative Alloy 2 in which 30
Comparative alloy 3, which was made up of TiC crystals having an average grain size of 4 μm outside the scope of the present invention and in which a Cc pool having an average grain size of 3 μm was present, was prepared by the following operations. Manufactured. 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
Prepare Co powder, and add these raw powders to 40% WC
- 10% TiC - 10% TaC - 10% Co (volume %), wet pulverized and mixed in a ball mill for 72 hours, then the balls in the ball mill were taken out and had an average particle size of 9 μm. TiC powder: 30% by volume was added, mixed for 5 hours, dried, and then 4% by weight of wood wax having an average particle size of 3 μm was added as an organic compound powder and processed in a dry process without pulverization. Alloy 1 of the present invention was manufactured by mixing, press-forming under manufacturing conditions of ordinary powder metallurgy, preliminary sintering, and finally main sintering. Furthermore, Comparative Alloy 1 was manufactured under the same conditions as those used in manufacturing Invention Alloy 1, except that the addition of wood wax and preliminary sintering were not performed. Furthermore, comparative alloy 2 does not use ultra-coarse-grained TiC powder as the raw material powder, that is, the above starting raw material powder is blended from the beginning to have the composition of the above p10 alloy during the production of the present invention alloy 1. Comparative alloy 3 was produced under the same conditions as used in
Average particle size: Instead of TiC powder with average particle size: 9μm
It was produced under the same conditions as applied to the production of Inventive Alloy 1, except that TiC powder having a diameter of 5 μm was used. Invention alloy 1 and comparative alloy 1~ obtained as a result
3 and the above p10 alloy, cutting chips with shapes conforming to CIS (Cemented Carbide Tool Association Standard) SNP432 were manufactured, work material: SNCM-8 (hardness H _B : 220), chip honing: 0.03. mm, Cutting speed: 200 m/min, Feed: 0.3 mm/rev., Depth of cut: 1.5 mm, Cutting time: 10 min, Continuous cutting tests were conducted under the following conditions to determine the flank wear (flank wear width) of the cutting edge. and crater wear (rake face wear depth), and furthermore, Work material: SNCM-8 (Hardness H _B : 280), Chip honing: None, Cutting speed: 140m/min, Feed: 0.3mm/ An interrupted cutting test was conducted under the following conditions: rev., depth of cut: 2 mm, cutting time: 3 min, and it was determined how many of the six cutting edges (chips) had defects. These measurement results are shown in Table 1.
The table also shows the average grain size of the TiC crystals and the average diameter of the Co pool. As shown in Table 1, Alloy 1 of the present invention maintains impact resistance equivalent to or better than Comparative Alloys 2 and 3, which do not contain ultra-coarse grained TiC crystals. On the other hand, although ultra-coarse grained TiC crystals are present, Co
It shows superior impact resistance while maintaining almost the same wear resistance as Comparative Alloy 1, which does not have a pool. In addition, Alloy 1 of the present invention exhibits superior properties in both wear resistance and impact resistance compared to the conventional p10 alloy.

[Table] Example 2 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, 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: Consists of 10% by volume, and during main sintering
The present invention was carried out in Example 1 except that 5% by weight (external number) of paraffin having an average particle size of 6 μm was added and mixed as an organic compound powder for forming pores that would become Co pools in the pre-sintered body. Invention Alloy 2 was produced under the same operating conditions as Alloy 1 was produced. Next, regarding the resulting invention alloy 2 and the above conventional p20 alloy, the following conditions were observed: Work material: SNCM-8 (hardness _HB : 220), Chip honing: 0.03 mm, Cutting speed: 150 m/min, Feed: An interrupted cutting test was conducted under the following conditions: 0.3 mm/rev., depth of cut: 1.5 mm, cutting time: 10 min, work material: SNCM-8 (hardness H _B : 280), chip honing: none, cutting speed: Intermittent cutting tests were conducted under the following conditions: 120 m/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. did.

[Table] As shown in Table 2, Invention Alloy 2 exhibits superior wear resistance in continuous cutting and superior impact resistance in interrupted cutting, compared to the conventional p20 alloy. That is clear. 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, 2% by volume of TiC powder as a starting raw material powder has an average particle size of 15 μm and TiC/WC = 80 mol%/
PVA substituted with (Ti, W)C powder having a composition of 20 mol% and having an average particle size of 8 μm as an organic compound powder for forming a Co pool:
Invention Alloy 3 was produced under the same operating conditions as in Example 1 for producing Invention Alloy 1, except that 5% by weight (extra number) was added and mixed. Next, the above-mentioned invention alloy 3 and the above-mentioned conventional p30
With alloy, work material: SNCM-8 (hardness H _B : 220), chip honing: 0.03mm, cutting speed: 100m/min, feed: 0.4mm/rev., depth of cut: 2.0mm, cutting time: 10min Continuous cutting tests were conducted under the following conditions: Work material: SNCM-8 (Hardness _HB : 280), Chip honing: None, Cutting speed: 100 m/min, Feed: 0.4 mm/rev., Depth of cut: An interrupted cutting test was conducted under the following conditions: 2.0 mm, cutting time: 3 min, and the results are shown in Table 3 as in Example 1.

[Table] As is clear from the results shown in Table 3,
In the case of this Example 3 as well, the alloy 3 of the present invention was conventionally p30
It exhibits superior wear and impact resistance compared to alloys. Example 4 Corresponds to JIS classification p10 with a component composition of 40% WC - 40% TiC - 10% TaC - 10% Co (volume %)
When producing a WC-based sintered cemented carbide, 30% by volume of the TiC powder as a starting raw material powder was mixed with a powder having an average particle size of 10 μm and a composition of TiC/ZrN = 95 mol%/5 mol%. (Ti, Zr) Except for adding and mixing 4% by weight (external number) of wood wax having an average particle size of 4 μm as an organic compound powder for forming a Co pool, Invention Alloy 4 was produced under the same conditions as Invention Alloy 1. Invention alloy 4 obtained as a result and the above conventional alloy
A cutting test was conducted on the p10 alloy under the same conditions as in Example 1, and the test results are shown in Table 4. Note that Table 4 also shows the average grain size of the (Ti, Zr)CN crystal and the average diameter of the Co pool.

[Table] In Example 4 as well as in Examples 1 to 3, Invention Alloy 4 exhibits excellent cutting properties. Example 5 Corresponds to JIS classification p20 with a component composition of 58% WC - 27% TiC - 3% TaC - 12% Co (volume %)
In the production of WC-based sintered cemented carbide, 15% by volume of Tic powder as a starting raw material powder has an average particle size of 20 μm, and TiC/VN/HfC = 94 mol%/5 mol%/1 mol. % composition (Ti,
V, Hf) Consisting of CN powder, average particle size: 5μ as an organic compound powder for forming a Co pool.
Invention alloy 5 was produced under the same conditions as in Example 1, except that 5% by weight (extra number) of paraffin having m was added and mixed. Cutting tests were conducted on the invention alloy 5 and the conventional p20 alloy under the same conditions as in Example 2, and the test results are shown in Table 5. As shown in Table 5, average grain size: 15μ
The alloy 5 of the present invention, in which (Ti, V, Hf)CN crystals having a diameter of 5 μm and Co pools having an average diameter of 5 μm are uniformly dispersed in the structure, is better in both continuous cutting and interrupted cutting than the conventional p20 alloy. It is clear that the material also exhibits excellent cutting properties.

[Table] Example 6 Corresponds to JIS classification p30 with a component composition of 67% WC - 14% TiC - 5% TaC - 14% Co (volume %)
When producing WC-based sintered cemented carbide, 5% by volume of the Tic powder as the starting raw material powder has an average particle size of 22 μm and TiC/TiN/Mo ₂ C = 50.
Consists of (Ti, MO)CN powder with a composition of mol%/3 mol%/20 mol%, and an average particle size of 10 as an organic compound powder for forming a Co pool.
Invention alloy 6 was produced under the same conditions as in Example 1, except that 5% by weight (extra number) of PVA having a diameter of .mu.m was added and mixed. Then, in the same manner, the above-mentioned invention alloy 6 was added to the above-mentioned conventional alloy.
When a cutting test was conducted on the p30 alloy under the same conditions as in Example 3, the results shown in Table 6 were obtained.

[Table] Also in the case of Example 6, as shown in Table 6, the alloy 6 of the present invention exhibits superior cutting properties compared to the conventional p30 alloy. 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 the 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, both used as raw material powders, were made to have an average particle size of 10 μm to form TiC/TaN.
=90 mol%/10 mol% (Ti,
Inventive alloy 1 in Example 1 except that it was composed of Ta) CN powder and 5% by weight (extra number) of paraffin having an average particle size of 5 μm was added and mixed as an organic compound powder for forming a Co pool. Inventive Alloy 7 was produced under similar operating conditions to those used to produce Inventive Alloy 7. 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. As shown in Table 7, average grain size: 11μ
A coarse TiC crystal with a diameter of m and (Ti, Ta) as a coarse composite compound crystal with a diameter of 7 μm.
Invention alloy 7 in which CN crystals and a Co pool having an average diameter of 5 μm are uniformly dispersed in the structure,
Continuous cutting and interrupted cutting compared to conventional p20 alloy.

[Table] It is clear that both types exhibit excellent cutting characteristics. As mentioned above, the WC-based sintered cemented carbide produced by the method of the present invention has excellent impact resistance that is equivalent to or even better than the conventional WC-TiC-TaC-Co-based sintered cemented carbide. In addition to having the above-mentioned excellent impact resistance, it also has extremely excellent wear resistance that cannot be obtained with the conventional WC-based sintered cemented carbide, and is therefore 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, a large TiC powder with an average particle size of 9 μm or more is blended and mixed as part of the raw material powder. , super-grained TiC crystals with an average grain size of 7 μm or more are uniformly dispersed in the alloy structure at a ratio of 1 to 30% by volume, and further added to the mixed powder with an average grain size of 3 to 10 μm. Organic compound powder is added at a ratio of 3 to 7% by weight, mixed without pulverization, and the green compact formed from this is pre-sintered to form pores in the pre-sintered compact. By filling these pores with binder phase-forming components through main sintering, the alloy structure also has the following properties:
A method for producing a tungsten carbide-based sintered cemented carbide, characterized by uniformly dispersing a binder phase pool with an average diameter of 30 to 10 μm, thereby providing excellent wear resistance and impact resistance. 2 When producing WC-TiC-TaC-Co based sintered cemented carbide, coarse TiC with an average particle size of 9 μm or more and particles 4a, 5a, and 6 of the periodic table are used as part of the raw material powder.
Composite compound powder with one or more components of group a metal carbides and nitrides (but
By blending and mixing TiC (containing 50 to 98 mol%), the average crystal grain size is 7 μm in the alloy structure.
The above-mentioned composite compound crystals of super-aggregated grains of m or more are uniformly dispersed at a ratio of 1 to 30% by volume, and further, 3 to 7 weight of organic compound powder with an average particle size of 3 to 10 μm is added to the mixed powder. %, mixed without pulverization, and pre-sintered the green compact formed from this to form pores in the preliminary sintered body, and these pores are bonded by main sintering. By filling in phase-forming components, the alloy structure also contains
A method for producing a tungsten carbide-based sintered cemented carbide, characterized by uniformly dispersing a binder phase pool with an average diameter of 3 to 10 μm, thereby 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.
TiC powder and composite compound powder of TiC and one or more carbides and nitrides of metals in groups 4a, 5a, and 6a of the periodic table (with the exception of TiC :50~98mol%
By blending and mixing 1 to 30 TiC crystals and the above-mentioned composite compound crystals, each of which has an average grain size of 7 μm or more, the super-grained TiC crystals and the above composite compound crystals are mixed.
% by volume, and further, add organic compound powder with an average particle size of 3 to 10 μm to the mixed powder at a ratio of 3 to 7% by weight, and perform mixing without pulverization. The green compact formed from this is pre-sintered to form pores in the preliminary sintered body, and by main sintering, filling these pores with a binder phase forming component, the alloy structure is also formed. ,
A method for producing a tungsten carbide-based sintered cemented carbide, characterized by uniformly dispersing a binder phase pool with an average diameter of 3 to 10 μm, thereby providing excellent wear resistance and impact resistance.