JP2009275237A - Cemented carbide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cemented carbide which has excellent wear resistance, chipping resistance and welding resistance even in high speed cutting and high feed cutting, and in which the using amount of WC is reduced compared with the conventional cemented carbide. <P>SOLUTION: In the cemented carbide composed of a hard phase component comprising WC, Ti(C, N) and (Ta, Nb)C (including the case of Nb=0) and a binding phase component of Co and/or Ni, the ratio of the hard phase component lies in the range of 80 to 92 wt.% and the ratio of the binding phase component lies in the range of 8 to 20 wt.%, and its structure is composed of four phases of a WC phase, a (W, Ti, Ta, Nb)(C, N) phase (including the case of Nb=0), a Ti(C, N) phase and a binding phase, wherein, regarding the area ratio of each phase measured by scanning electron microscopy, that of the WC phase lies in the range of 10 to 45%, that of the (W, Ti, Ta, Nb)(C, N) phase lies in the range of 30 to 60% and that of the Ti(C, N) phase lies in the range of 5 to 25%, and the balance binding phase. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a super-hard alloy used for cutting tools and the like, and particularly to a super-hard alloy having excellent wear resistance and fracture resistance and high welding resistance even in high-speed cutting and high-feed cutting. is there.

  Conventionally, cemented carbides composed of a hard phase component of WC, TiC, (Ta, Nb) C and a binder phase component of Co and / or Ni have been used for cutting materials used for cutting tools and the like. Widely used for its excellent fracture resistance.

  Here, it is known that the structure of such a cemented carbide is composed of three phases of a WC phase, a (W, Ti, Ta, Nb) C phase generally composed of β-phase, and a binder phase. It has been.

  However, in recent years, when cutting with a cutting tool or the like, further high-speed cutting or high-feed cutting has been performed, and even when the above cemented carbide is used, sufficient wear resistance and There is a problem that the welding resistance cannot be obtained, and it has been desired to further improve the wear resistance and the welding resistance.

  In recent years, from the viewpoint of soaring WC raw materials and resource saving, it is also desired to replace WC with other compounds to reduce the amount of WC used.

  And as shown in patent document 1, periodic table IVa, Va, VIa group metal compounds, such as TiCN, are added to a cemented carbide, and the particle size is divided into the surface region and the internal region of the structure of the cemented carbide. And cemented carbides with different binder phase area ratios have been proposed.

  However, even the cemented carbide disclosed in Patent Document 1 cannot sufficiently improve the wear resistance and welding resistance at the time of high-speed cutting and high-feed cutting.

  Conventionally, cermets mainly composed of TiC, TiN and TiCN have been used as materials for finishing cutting tools as materials suitable for high-speed cutting, which are superior in chemical stability compared to cemented carbides mainly composed of WC. in use.

  Here, it is known that a cermet structure containing a large amount of TiCN is generally a cored structure having TiCN as a nucleus and periodic table IVa, Va, VIa group carbides and carbonitrides as surrounding structures. Yes.

  However, cermets containing a large amount of TiCN have lower strength and lower thermal conductivity than cemented carbides, and therefore have problems such as being prone to chipping during high-feed cutting or high-speed intermittent cutting. there were.

  For this reason, for example, as shown in Patent Document 2, a cermet mainly composed of a solid solution having no cored structure, or as shown in Patent Document 3, the first and second hard cores having a specific cored structure. A cermet composed of a phase and a third hard phase having a single-phase structure and a binder phase has been proposed.

However, the cermets disclosed in Patent Documents 2 and 3 also have a problem that a high-strength alloy such as a cemented carbide cannot be obtained, and defects are still generated during high-feed cutting.
JP 2004-263254 A JP-A-6-330219 JP 2006-346776 A

  An object of the present invention is to solve the above-mentioned various problems in cemented carbides and cermets used for cutting tools and the like, and wear resistance and fracture resistance even in high-speed cutting and high-feed cutting. It is an object of the present invention to provide a super hard alloy that is excellent in heat resistance, excellent in welding resistance, and capable of reducing the amount of WC used compared to conventional super hard alloys.

  In the present invention, in order to solve the above-mentioned problems, a hard phase component containing WC, Ti (C, N), (Ta, Nb) C (including the case where Nb = 0), Co And / or in the superhard alloy composed of Ni binder phase component, the hard phase component is in the range of 80 wt% to 92 wt%, the binder phase component is in the range of 8 wt% to 20 wt%, and the structure is It consists of four phases: WC phase, (W, Ti, Ta, Nb) (C, N) phase (including Nb = 0), Ti (C, N) phase, and bonded phase. The area ratio of each phase measured by photographs is 10% to 45% for the WC phase, 30% to 60% for the (W, Ti, Ta, Nb) (C, N) phase, and the Ti (C, N) phase. Is in the range of 5% to 25%, and the balance is composed of the binder phase.

  Here, regarding the area ratio of each phase in the structure of the super hard alloy of the present invention, the surface of the super hard alloy that is mirror-finished is randomly viewed 10 times by a scanning electron microscope (SEM) at a 5000 times COMPO image. The phase of 528 lattice points on the photograph for each field of view is classified into WC phase, (W, Ti, Ta, Nb) (C, N) phase, and Ti (C, N) phase, With the remainder as the binder phase, the area ratio of each phase was determined, and the average value was shown. Note that the size of one field of view is 18 × 24 μm.

  In the super hard alloy of the present invention, the hard phase component is in the range of 80 wt% to 92 wt% and the binder phase component is in the range of 8 wt% to 20 wt%. If the ratio is less than 1, the strength of the superhard alloy is reduced and the fracture resistance is lowered. On the other hand, if the binder phase component exceeds 20% by weight, the hardness of the superhard alloy is lowered and sufficient wear resistance is obtained. It is because it becomes impossible.

  Further, in the superhard alloy of the present invention, when Ti (C, N) is added to the hard phase component, the grain growth of the (W, Ti, Ta, Nb) C phase consisting of the cubic crystal called the β phase is caused. Suppressed, the structure becomes finer and the wear resistance of the superhard alloy is improved.

  When this Ti (C, N) is added to some extent, the β phase changes to the (W, Ti, Ta, Nb) (C, N) phase, and the WC phase In addition to the (W, Ti, Ta, Nb) (C, N) phase and the binder phase, a single Ti (C, N) phase appears to form four phases, and this Ti (C, N) phase It is thought that the chemical stability of super hard alloys at high temperatures and the welding resistance during high-speed cutting are remarkably improved. However, if the amount of Ti (C, N) to be added becomes too large, the area ratio of the WC phase decreases, and the strength and thermal conductivity of this superhard alloy decrease. , N) is preferably in the range of 8% to 35% by weight.

  Further, in the superhard alloy of the present invention, the area ratio of the Ti (C, N) phase in the structure is in the range of 5% to 25% because the area ratio is less than 5% as described above. On the other hand, if the area ratio exceeds 25%, the WC phase area ratio decreases as described above, and the strength and thermal conductivity of the superhard alloy decrease. .

  Moreover, it does not specifically limit about C / N ratio in Ti (C, N) added as a hard phase component, For example, C / N ratio is 8/2, 7/3, 5/5, 3/7, What became 2/8 can be used. However, the higher the C / N ratio in Ti (C, N), the more it reacts with the hard phase components WC and (Ta, Nb) C, and the aforementioned (W, Ti, Ta, Nb) (C, N) It becomes easy to form a phase, and the ratio of remaining as a Ti (C, N) phase in the structure is lowered. On the other hand, the lower the C / N ratio, the more difficult it is to form the (W, Ti, Ta, Nb) (C, N) phase, and the higher the ratio of remaining Ti (C, N) phase in the structure. In addition, the sinterability is deteriorated, and denitrification occurs during sintering, and pores are easily generated. However, the generation of pores as described above is caused by performing a sintering pip process in which an inert gas is processed at a high pressure of about 5 MPa after sintering or a HIP process in which a high temperature process is performed again at a high pressure of about 120 MPa after sintering. Can be prevented.

  Also, in the super hard alloy of the present invention, the area ratio of the WC phase in the structure is in the range of 10% to 45% because when the area ratio of the WC phase is less than 10%, the super hard alloy This is because the strength and thermal shock resistance of the steel are reduced, and if the area ratio exceeds 45%, the wear resistance of the superhard alloy is reduced.

  In the super hard alloy of the present invention, the area ratio of the (W, Ti, Ta, Nb) (C, N) phase in the structure is in the range of 30% to 60%. When the ratio is less than 30%, the wear resistance and oxidation resistance of the superhard alloy cannot be sufficiently improved. On the other hand, when the area ratio exceeds 60%, the WC phase and Ti (C, This is because the ratio of the N) phase decreases and the strength of the superhard alloy decreases.

  In the superhard alloy of the present invention, the phase components IVa, Va, and VIa group compounds can be contained in an amount of 5% by weight or less in the phase component.

  Here, these carbides, nitrides, and carbonitrides can be used as the compounds of the periodic table groups IVa, Va, and VIa. For example, when a Cr or V compound is added, Cr and V are considered to be dissolved in the binder phase. In addition, when a Mo compound is added, it becomes easy to form a (W, Ti, Ta, Nb) (C, N) phase together with WC and Ti (C, N), and the sinterability is improved. However, the grain size of the (W, Ti, Ta, Nb) (C, N) phase becomes coarse, and the strength and wear resistance of the superhard alloy tend to deteriorate.

  In the superhard alloy of the present invention, the hard phase component containing WC, Ti (C, N), (Ta, Nb) C (including the case where Nb = 0) is 80 wt% to 92 wt%, The binder phase component of Co and / or Ni is in the range of 8 wt% to 20 wt%, and the structure is WC phase, (W, Ti, Ta, Nb) (C, N) phase (where Nb = 0 ), Ti (C, N) phase, and bonded phase, and the area ratio of each phase measured by a scanning electron microscope is 10% to 45% for the WC phase, and (W, Ti , Ta, Nb) (C, N) phase is in the range of 30% to 60%, Ti (C, N) phase is in the range of 5% to 25%, and the balance is composed of the binder phase. Compared to alloys and cermets, the wear resistance, fracture resistance, and welding resistance are greatly improved as described above. Also in feed cutting, it becomes welded wear and defects or chips can be prevented, it becomes possible to reduce the amount of WC than more traditional cemented carbide.

  Next, the superhard alloy according to the present invention will be specifically described with reference to examples, and when cutting is performed using a tip using the superhard alloy according to this example for a face mill. It will be clarified with a comparative example that wear, chipping and chip welding are prevented in the chip. The superhard alloy according to the present invention is not particularly limited to those shown in the following examples, and can be appropriately modified and implemented without departing from the scope of the invention.

(Examples 1-9 and Comparative Examples 1-9)
In Examples 1-9 and Comparative Examples 1-9, as the hard phase component, WC powder having an average particle diameter of 1.1 μm and Ti (C) having an average particle diameter of 1.5 μm and C / N of 5/5 , N) powder and (Ta, Nb) C powder having an average particle diameter of 1.2 μm and Ta / Nb of 7/3, and Co powder having an average particle diameter of 1.3 μm as the binder phase component. I did it.

Further, in Example 8, Ni powder having an average particle diameter of 1 μm as the binder phase component, and in Example 9, the average particle diameter of the periodic table IVa, Va, VIa group carbides as the other components. 1.2 μm VC powder, in Comparative Example 3, Ni powder having an average particle size of 1 μm as a binder phase component, and other components having an average particle size of carbides of periodic table IVa, Va, VIa group A 2.5 μm Mo ₂ C powder was used.

  And said hard phase component, a binder phase component, and another component were mix | blended so that it might become a weight ratio respectively shown in the following Table 1, acetone was used for the mixed solvent, and the cemented carbide ball was used. After mixing for 72 hours by a ball mill, 2% by weight of paraffin was added to each mixture and dried by a spray dryer to obtain a powder of each superhard alloy.

  Next, each of the superhard alloy powders obtained as described above was press-molded into a predetermined shape, and then sintered at 1400 ° C. for 60 minutes under a reduced pressure of 100 Pa in an argon atmosphere. A sintered body was obtained.

  Then, the surface of the sintered body of each super-hard alloy obtained as described above is mirror-finished, and a 5000-times COMPO image is randomly obtained on the mirror-finished surface by the scanning electron microscope (SEM) as described above. 10 fields of view, and the phase of 528 lattice points on the photograph for each field of view is WC phase, (W, Ti, Ta, Nb) (C, N) phase, and Ti (C, N) phase. The area ratio of each phase was obtained by classifying and the remainder as the binder phase, and the average value of the area ratio of each phase was calculated. The results are shown in Table 1. Moreover, in the sintered body of the superhard alloys of Comparative Examples 1 to 3 in which the weight ratio of Ti (C, N) in the hard phase component is large, the cored structure was the same as that of the cermet, so that the cored structure was shown. .

Here, the SEM photograph of the sintered body of the super hard alloy of Example 2 is shown in FIG. 1, the SEM photograph of the sintered body of the super hard alloy of Example 3 is shown in FIG. 2, and the sintered body of the super hard alloy of Example 4 is fired. The SEM photograph of the ligature is shown in FIG. In these SEM photographs, the white part shown as (1) is the WC phase, the black part shown as (2) is the Ti (C, N) phase, and the light gray part shown as (3) is The dark gray portions shown as (W, Ti, Ta, Nb) (C, N) phase (abbreviated as β _CN phase) and (4) are the binder phase.

  Moreover, the SEM photograph of the sintered compact of the super hard alloy of the comparative example 1 was shown in FIG. In this SEM photograph, the portion near black shown as (1) is the Ti (C, N) phase that becomes the core, and the gray portion shown as (2) is the surrounding structure (W, Ti, Ta, Nb) ) (C, N) phase, white part shown as (3) is a binder phase, and has a cored structure having surrounding tissues around the core part.

(Comparative Example 10)
In Comparative Example 10, as the hard phase component, instead of the Ti (C, N) powders in Examples 1 to 9 and Comparative Examples 1 to 8, the average particle diameter is 1.2 μm and W / Ti is 5 / 5 (W, Ti) C powder is used, and the hard phase component and the binder phase component are blended so as to have a weight ratio shown in Table 2 below. Otherwise, the above Examples 1 to 9 and Comparative Example In the same manner as in cases 1 to 9, a sintered body of super hard alloy was obtained.

  And also about the sintered body of the superhard alloy obtained in this way, the SEM photograph was image | photographed similarly to the case of said Examples 1-9 and Comparative Examples 1-9, and the area of each phase in a structure | tissue The average value of the ratios was determined, and the results are shown in Table 2 below.

  Here, in the sintered body of the super hard alloy of Comparative Example 10, since Ti (C, N) powder is not used for the hard phase component as described above, as shown in the SEM photograph of FIG. (C, N) phase does not appear, white WC phase shown as (1), and light gray (W, Ti, Ta, Nb) C phase (abbreviated as β phase) shown as (2). , (3) and a dark gray binder phase.

(Examples 10 and 11 and Comparative Examples 11 and 12)
In Example 10 and Comparative Examples 11 and 12, as a hard phase component, C / N in the above Examples 1 to 9 and Comparative Examples 1 to 9 was replaced with Ti (C, N) powder of 5/5, Ti (C, N) powder having an average particle diameter of 1.5 μm and C / N of 7/3, and in Example 11, Ti (C, N) having an average particle diameter of 1.5 μm and C / N of 3/7 , N) Powder was used.

Furthermore, in Example 10, as other components, Cr ₃ C ₂ powder having an average particle size of 1.4 μm, which is a carbide of periodic table IVa, Va, VIa, is used. In Example 11, the average particle size is Used 2.5 μm Mo ₂ C powder.

  And said hard phase component, a binder phase component, and another component are mix | blended so that it may become a weight ratio shown in following Table 3, respectively, Otherwise, said Examples 1-9 and Comparative Examples 1- 1 In the same manner as in the case of 9, sintered bodies of the respective superhard alloys were obtained.

  And also about the sintered compact of each super-hard alloy obtained in this way, the SEM photograph was image | photographed similarly to the case of said Examples 1-9 and Comparative Examples 1-9, and each phase in structure | tissue is taken. The average value of the area ratio was determined, and the result is shown in Table 3 below.

  And the chip | tip of ISO standard SEKN1203AFN-16 was produced using the sintered compact of each super-hard alloy of said Examples 1-11 and Comparative Examples 1-12, and the diameter of each of the produced | generated chip | tips was each set as the cutter diameter. Attached to a 100 mm face mill.

  In the first cutting test, the cutting speed is 150 m / min, the feed rate is 0.3 mm / blade, the cutting depth is 2.0 mm, and the cutting width is 75 mm in the first cutting test using the face mill with the above chips attached. Repeat cutting with a cutting length of 0.5m under the conditions described above, and check the amount of wear on the flank face and chip chipping of the chip. If the above wear amount is 0.3 mm or more, or chipping occurs. In this case, the cutting length at that time, and if the wear amount is not 0.3 mm or more, or if the chip is not chipped, the wear amount at the cutting length of 20 m is obtained. Is shown in Table 4 below.

  In the second cutting test, cutting with a cutting length of 0.5 m was repeated on SUS304 material under conditions of a cutting speed of 120 m / min, a feed of 0.2 mm / blade, a cutting depth of 2.0 mm, and a cutting width of 75 mm. Investigate the amount of wear on the flank surface, chip chipping and chip welding on the chip.If the above wear amount is 0.3 mm or more, chipping occurs, or the chip is welded. If the wear amount does not exceed 0.3 mm, the chip does not chip, or the chip does not weld, the cutting length The amount of wear at the time of 5 m was determined, and the results are shown in Table 4 below.

  As is apparent from the results, when the chips made of the sintered bodies of the superhard alloys of Examples 1 to 11 satisfying the conditions of the present invention are used, the first cutting test and the second cutting test are performed. In any case, there was little wear of the tip, and the tip was not chipped or chips were not welded.

  On the other hand, when using a chip made of a sintered body of each superhard alloy that has the same cored structure as the cermets of Comparative Examples 1 to 3, the first cutting test and the second cutting test are performed. In any case, chipping occurred in the chip.

  Further, each of the superhards of Comparative Example 4 and Comparative Example 8 in which the area ratio of the WC phase exceeds 45%, Comparative Example 7 in which the binder phase component exceeds 20% by weight, and Comparative Example 10 in which no Ti (C, N) phase exists. When a chip made of an alloy sintered body is used, the chip wear increases both in the first cutting test and the second cutting test, and the super hard alloys of Comparative Example 4 and Comparative Example 10 are used. In the case where the chip made of the sintered body was used, chip welding occurred in the second cutting test.

  Further, Comparative Example 5 and Comparative Example 9 in which the area ratio of the WC phase was less than 10%, Comparative Example 6 in which the binder phase component was less than 8% by weight, (W, Ti, Ta, Nb) (C, N ) In the case of using a chip made of a sintered body of each super hard alloy of Comparative Example 11 and Comparative Example 12 in which the phase area ratio exceeds 60%, in any of the first cutting test and the second cutting test In addition, chipping occurred in the chip, and in the case where the chip made of the sintered super hard alloy of Comparative Example 11 and Comparative Example 12 was used, chip welding occurred in the second cutting test.

6 is a view showing a structure state of a sintered body of a super hard alloy of Example 2. FIG. 6 is a view showing a structure state of a sintered body of a super hard alloy of Example 3. FIG. It is the figure which showed the structure | tissue state in the sintered compact of the super hard alloy of Example 4. FIG. 6 is a view showing a structure state in a sintered body of a super hard alloy of Comparative Example 1. FIG. 6 is a view showing a structure state of a sintered body of a super hard alloy of Comparative Example 10. FIG.

Claims (3)

  In a superhard alloy comprising a hard phase component containing WC, Ti (C, N), (Ta, Nb) C (including the case where Nb = 0) and a binder phase component of Co and / or Ni. The hard phase component is in the range of 80 wt% to 92 wt%, the binder phase component is in the range of 8 wt% to 20 wt%, and the structure is the WC phase, (W, Ti, Ta, Nb) (C, N) phase (provided that Nb = 0 is included), Ti (C, N) phase, and binder phase, and the area ratio of each phase measured by scanning electron micrograph is WC phase. 10% to 45%, (W, Ti, Ta, Nb) (C, N) phase is in the range of 30% to 60%, Ti (C, N) phase is in the range of 5% to 25%, the balance is the bonded phase Super hard alloy characterized by comprising   The superhard alloy according to claim 1, wherein the amount of Ti (C, N) in the hard phase component is in the range of 8 wt% to 35 wt%.   The superhard alloy according to claim 1 or 2, wherein the phase component contains 5% by weight or less of a compound of groups IVa, Va and VIa of the periodic table.