JP6358433B2 - Titanium carbonitride-based cermet powder, titanium carbonitride-based cermet sintered body, and manufacturing method of titanium carbonitride-based cermet cutting tool - Google Patents

Description

The present invention, titanium carbonitride (hereinafter, denoted as "TiCN".) The method of manufacturing group cermet powder, comprising a method of manufacturing a preparation and TiCN based cermet cutting tools of TiCN based cermet sintered body, raw material Method for producing TiCN-based cermet powder having a step of grinding and mixing powder and solvent using hard media, TiCN-based cermet sintered body having excellent toughness obtained by sintering this powder, and TiCN-based cermet The present invention relates to a method for manufacturing a cutting tool.

Conventionally, TiCN-based cermets are used for various cutting tools, jigs, machine parts and the like because of their high hardness and excellent wear resistance. Moreover, since the affinity with iron (Fe) is low and the finished surface after processing becomes high-grade, it is often used in steel finishing in cutting. However, in recent years, the performance required for a cutting tool made of TiCN-based cermet has been increasingly demanded not only for wear resistance but also for chipping resistance directly connected to the finished surface quality.
To improve the chipping resistance of TiCN-based cermet cutting tools, it is necessary to improve the fracture toughness as a physical property of the cermet. Although various proposals have been made, no such proposal is found in TiCN-based cermets.

  As a general mixing and pulverizing method for TiCN-based cermet, for example, as shown in Patent Document 1, it is known to mix for 3 to 20 hours with an attritor using spherical hard media of about 3 to 15 mmφ.

JP-A-8-117580

  In the prior art TiCN-based cermet shown in Patent Document 1 described above, this is used as, for example, a blade-tip-replaceable insert, and exhibits excellent wear resistance when subjected to normal cutting. When it is used for severer cutting conditions where high load is generated, such as high-speed steel turning and turning of steel with interrupted parts, chipping is likely to occur due to the strong load on the cutting edge, There was a problem that the service life was reached in a relatively short time.

  Accordingly, the present inventor has developed a TiCN-based cermet cutting tool that has excellent chipping resistance and excellent wear resistance even when used under severe cutting conditions in which chipping tends to occur at the cutting edge. As a result, the following findings were obtained as a result of extensive research.

In order to obtain a cutting tool made of TiCN-based cermet having excellent chipping resistance, the present inventor has investigated the relationship between the structure of TiCN-based cermet and fracture toughness. The presence of micropores in TiCN-based cermet and the relationship between hard particles It was found that the degree of contact greatly affects fracture toughness.
That is, as shown in FIG. 1, in the structure of the TiCN-based cermet, foreign matter (adsorbed oxygen, etc.) on the surface of the raw material used is caused by the hard phase / hard phase interface or a part of the hard phase / binding phase interface. Micropores may occur, and removing them is the key to improving fracture toughness. Furthermore, the adhesive strength is weak at the interface where the hard phases containing TiCN etc. are in direct contact, and cracks at the time of fracture propagate Therefore, it was found that the key to improving fracture toughness is to obtain a homogeneous structure mainly composed of the hard phase / bond phase interface by reducing the hard phase / hard phase interface as much as possible.

And when this inventor further investigated the manufacturing process for forming the homogeneous structure with few micropores of a TiCN group cermet, and having a hard phase / hard phase interface few, in order to control micropores, When crushing and mixing the raw material powder of TiCN-based cermet, first, crushing and mixing treatment is performed using spherical hard media with a relatively large diameter and high crushing energy, and the primary particles of the raw material are reliably crushed to form a hard phase. Spherical hard media with a relatively small diameter in order to make a new surface of the raw material to be formed (called crushing treatment) and to obtain a homogeneous structure consisting of a hard phase / bond phase interface by reducing the hard phase / hard phase interface It is necessary to pulverize the aggregated secondary particles of the raw material (called pulverization treatment), and the diameter of the pulverization treatment media is There is less than the length necessary for the gap that occurs between the media and is the effect by repeated by circulating crushing and disintegration to obtain a knowledge that is obtained.
The crushing and crushing methods may be any method as long as they are performed in a container using a spherical hard medium and a liquid solvent, and representative examples include a ball mill, an attritor, and a bead mill.

  After pulverizing and mixing by this method, a compacted green body is formed, and this is sintered to obtain a TiCN-based cermet sintered body, as shown in FIG. As a result, a TiCN-based cermet cutting tool made of a TiCN-based cermet sintered body has a severe load on the cutting edge, such as high-speed turning processing. The present inventors have found that even when used for turning steel with an interrupted portion, it exhibits excellent chipping resistance and excellent wear resistance.

The present invention has been made based on the above findings,
“(1) TiCN-based cermet powder production method, 5-15% by mass of cobalt powder having an average particle size of 1.5 μm or less, and 2-10% by mass of nickel powder having an average particle size of 3.0 μm or less 20 to 40% by mass of one or more carbide powders of tungsten, molybdenum, tantalum and niobium having an average particle size of 3.0 μm or less, and the balance is carbonitriding having an average particle size of 0.5 to 3.0 μm When raw material powder made of titanium powder is pulverized and mixed in a container using a liquid solvent and spherical hard media,
The crushing process using the spherical hard medium having a relatively large diameter D is performed for 20 minutes to 1 hour, and then the crushing process using the spherical hard medium having a relatively small diameter d and the relatively large diameter are performed. The crushing process using the spherical hard medium having D is circulated and repeated for 1 to 6 hours , and the diameter D of the spherical hard medium having a relatively large diameter used in the crushing process is 5.0 to 20. TiCN-based cermet powder having a diameter d of 0 mmφ and a diameter d of the relatively small spherical hard media used in the crushing treatment satisfies a relationship of d / D = 0.08 to 0.16 Manufacturing method.
(2) A method for producing a TiCN-based cermet sintered body , wherein the TiCN-based cermet powder obtained by the production method according to (1) is molded and then sintered.
(3) A method for producing a TiCN-based cermet cutting tool, wherein the TiCN-based cermet powder obtained by the production method according to (1) is molded and then sintered. "
It is characterized by.

  The present invention will be described in detail below.

First, the reasons for determining the blending composition of the raw material powder, the average particle size, and the like are as follows.
Cobalt powder:
Cobalt powder is contained as a binder phase forming component in the TiCN-based cermet. However, when the cobalt content is less than 5% by mass, the desired fracture toughness cannot be obtained. On the other hand, when the cobalt content exceeds 15% by mass, the cobalt powder rapidly increases. Since the desired hardness required as a TiCN-based cermet cutting tool cannot be obtained, the content ratio of the cobalt powder in the raw material powder is determined to be 5 to 15% by mass.
Further, since the cobalt powder causes adhesion during mixing when the average particle size exceeds 1.5 μm and causes poor mixing, the average particle size is determined to be 1.5 μm or less.

Nickel powder:
The nickel powder having higher wettability with the hard phase than cobalt is included as a binder phase forming component in the TiCN-based cermet together with the cobalt powder, but if the nickel content is less than 2% by mass, the desired fracture toughness cannot be obtained. On the other hand, if the nickel content exceeds 10% by mass, it softens rapidly and the desired hardness required for a TiCN-based cermet cutting tool cannot be obtained. -10% by mass.
Further, since the nickel powder causes adhesion during mixing when the average particle size exceeds 3.0 μm and causes poor mixing, the average particle size is determined to be 3.0 μm or less.

One or more carbide powders of tungsten, molybdenum, tantalum and niobium:
The powder is mainly contained as a hard phase forming component in the TiCN-based cermet, and increases the high-temperature strength of the hard phase or improves the wettability with the binder phase to suppress cermet chipping. However, this effect is insufficient when the content is less than 20% by mass. On the other hand, when the content exceeds 40% by mass, the Ti component ratio in the cermet becomes relatively small and wear resistance is reduced. It begins to decline.
Therefore, the content ratio of one or more carbide powders of tungsten, molybdenum, tantalum, and niobium in the raw material powder is set to 20 to 40% by mass.
In addition, when the average particle size of one or more carbide powders of tungsten, molybdenum, tantalum, and niobium exceeds 3.0 μm, they are not uniformly dispersed throughout the mixed powder, and as a result, the hard phase composition after sintering is not stable. In order to cause homogenization, the average particle size was determined to be 3.0 μm or less.

TiCN powder:
The smaller the average particle size of the TiCN powder in the raw material powder, the smaller the particle size of the hard phase in the TiCN-based cermet cutting tool, and the bending strength and wear resistance are improved, but if the average particle size is too small, In the present invention, the lower limit of the average particle size of the TiCN powder is set to 0. 0 because it becomes difficult to be densified during sintering, easily generates pores, and the chipping resistance of the TiCN-based cermet cutting tool decreases. The thickness was 5 μm.
On the other hand, if the average particle size of the TiCN powder in the raw material powder exceeds 3.0 μm, even if pulverization treatment / mixing treatment is performed, a coarse hard particle remains in the TiCN-based cermet, resulting in a non-uniform structure. In the present invention, the upper limit value of the average particle size of the TiCN powder is set to 3.0 μm.

Spherical hard media diameter D used for crushing treatment:
The crushing process is a process whose main purpose is to make sure that the primary particles of the raw material are crushed by the spherical hard medium to make a new surface of the raw material appear, and the diameter D of the spherical hard medium is 5. If it is less than 0 mmφ, the crushing force is insufficient, so that the raw material powder forming the hard phase having an average particle size of 0.5 to 3.0 μm cannot be sufficiently crushed, while the spherical hard media diameter D is 20. If it exceeds 0 mmφ, a sufficient crushing effect cannot be obtained due to the generation of aggregated secondary particles of the raw material powder that forms a crushed hard phase, the remaining of coarse hard particles, etc. The diameter D needs to be D = 5.0 to 20.0 mmφ.

Spherical hard media diameter d used for crushing treatment:
The main purpose of the crushing treatment is to crush the aggregated secondary particles of the raw material forming the hard phase in order to obtain a homogeneous structure consisting of the hard phase / bonded phase interface by reducing the hard phase / hard phase interface. Since it is a process, the diameter d of the spherical hard media used for the crushing process needs to be smaller than the length of the gap generated between the spherical hard media used for the crushing process. When the diameter of the spherical hard medium used for the crushing process is D, the length d of the gap generated between the spherical hard media and the medium is d≈0.16D. The media diameter d has an upper limit of 0.16D. On the other hand, when the diameter d is smaller than 0.08D, the crushing force for crushing the aggregated secondary particles of the raw material forming the hard phase is lowered, so the diameter d needs to be 0.08D or more.
Therefore, in this invention, the diameter d of the spherical hard medium used for a crushing process is made into the range of 0.08D-0.16D.

  The average particle size of cobalt powder, nickel powder, one or more carbide powders of tungsten, molybdenum, tantalum, and niobium, and TiCN powder defined in the present invention is a particle size determined by the Fisher method (FSSS). The average value of

Next, the processing steps of the present invention will be described.
(A) As a raw material powder, one or more carbide powders of TiCN powder, Co powder, Ni powder, W, Mo, Ta, and Nb having a predetermined average particle diameter are blended in a predetermined ratio.
(B) First, this raw material powder is crushed for 20 minutes to 1 hour in a container using a spherical hard medium having a diameter of 5.0 to 20.0 mmφ and a liquid solvent, and a mixed slurry having a certain degree of homogeneity is obtained. To manufacture.
(C) Next, the mixed slurry is guided to another container, and crushing treatment is performed in the container using a spherical hard medium having a diameter of 0.08 to 0.16 Dmmφ and a liquid solvent when the medium diameter is D. Return to the container (b).
(D) Furthermore, the mixed slurry is circulated through the step (b) and the step (c), so that the crushing treatment and the crushing treatment are simultaneously performed in parallel for 1 to 6 hours, and then the slurry is dried. To obtain a TiCN-based cermet powder.
(E) Next, the green compact is pressed into a predetermined shape.
(F) Next, in a predetermined atmosphere, a TiCN-based cermet sintered body is obtained by maintaining a predetermined temperature within a range of 1400 to 1600 ° C.
(G) A TiCN-based cermet cutting tool is manufactured by processing the TiCN-based cermet sintered body into a desired shape and size.

Here, there are a ball mill, an attritor, a bead mill, etc. as a method of pulverization / mixing treatment, and each will be described briefly.
As is well known, the ball mill is filled with a spherical hard medium having a diameter of about 2.0 to 20.0 mmφ and a raw powder together with a liquid solvent and rotated, and the impact caused by the fall of the spherical hard medium It is a device that grinds and mixes raw material powder by friction.
Attritor fills a vertical cylindrical container with spherical hard media with a diameter of about 2.0-20.0mmφ, rotates the stirring shaft with arm at high speed in this container, and collides with each other in a high-speed rotation field. This is an apparatus for pulverizing and mixing the raw material powder mixed with the liquid and made into a slurry by contacting (scratching).
The bead mill has substantially the same configuration as that of the attritor, but the size of the media is smaller than that used in the attritor (diameter: about 0.03 to 2.0 mmφ), and a pin is used as the stirring shaft. A stirrer shaft is used.

In the production method of the present invention, first, the crushing process in the step (b) is performed for 20 minutes to 1 hour. When the treatment time is less than 20 minutes, the blended raw material powder and the liquid solvent are not sufficiently blended, and a slurry having a sufficiently homogeneous viscosity is not formed at the initial stage. Therefore, the step of circulating the steps (b) and (c) ( Even if it transfers to d), the effect of this invention is not acquired. Further, in order to cause a structural abnormality such as significant grain growth when exceeding 1 hour, the processing time in the step (b) was set to 20 minutes to 1 hour.
In step (d), the crushing process and the crushing process are simultaneously performed for 1 hour to 6 hours. If the treatment time is less than 1 hour, the desired effect of improving fracture toughness cannot be obtained. On the other hand, if the treatment time exceeds 6 hours, the hard particles are excessively refined and the balance between hardness and toughness as an alloy is achieved. In the present invention, the processing time in the step (d) is set to 1 to 6 hours because it cannot be taken.
The mixed raw material powder produced in the steps (b), (c) and (d) is press-molded at a pressure of about 100 MPa in the step (e) to produce a green compact having a predetermined shape, and then In the step (f), a TiCN-based cermet sintered body is produced by maintaining and sintering at a predetermined temperature within a range of 1400 to 1600 ° C. in a predetermined atmosphere, and then in the step (g). Then, a TiCN-based cermet cutting tool is manufactured by processing into a predetermined size and shape.

According to the manufacturing method of the present invention, a crushing process using a spherical hard medium having a relatively large diameter and a crushing process using a spherical hard medium having a small fixed ratio with respect to the media diameter used in the process are circulated. By repeatedly carrying out the process, it is possible to produce a TiCN-based cermet powder that suppresses micropores and forms a homogeneous structure with few hard phase / hard phase interfaces, and to sinter this TiCN-based cermet powder. Thus, a TiCN-based cermet sintered body having excellent toughness can be obtained.
When a TiCN-based cermet sintered body obtained from the TiCN-based cermet powder produced by the production method of the present invention is used as a cutting tool, severe cutting conditions such as high-speed rolling occur that cause a heavy load on the cutting edge. Even when used for machining and turning of steel with interrupted parts, it exhibits excellent chipping resistance and excellent wear resistance.

It is a schematic diagram of the cermet structure which consists of the hard phase of conventional TiCN group cermet, a binder phase, and a micropore, Comprising: It shows that there are many hard phase / hard phase interfaces, and there is much formation amount of a micropore. It is a schematic diagram of the cermet structure which consists of the hard phase of a TiCN group cermet obtained by the manufacturing method of the present invention, and a binder phase, and shows that there are many hard phase / binder phase interfaces, and micropores are hardly formed.

  The present invention will be specifically described below using examples.

First, as raw material powders, TiCN powders (TiC / TiN = 50/50 in mass ratio) having respective average particle sizes shown in Table 1, Co powder, Ni powder, WC powder, Mo ₂ C powder, TaC powder, NbC Similarly, powders were blended in the proportions shown in Table 1 to prepare raw material powders A to D.

  The raw material powders A to D were charged into a pulverization / mixing apparatus using spherical hard media having the diameters shown in Table 2, and pulverization / mixing treatment I was performed for the time shown in Table 2. Next, the slurry was introduced into a pulverizing / mixing apparatus using spherical hard media having the diameters shown in Table 2 to perform pulverizing / mixing treatment II, and then returned to the pulverizing / mixing apparatus I again, and this was repeated . The circulating and parallel processing of the pulverization / mixing processing I and II was performed for the time shown in Table 2. Then, it was press-molded at a pressure of 150 MPa to produce a green compact having a shape defined by ISO · SEEN1203AFTN1.

  Next, the green compact is heated from room temperature to 1470 ° C. in a vacuum atmosphere of 13 Pa or less, and then nitrogen is introduced to form a nitrogen atmosphere of 133 Pa. The powder is held at 1470 ° C. for 1 hour and sintered, and TiCN A base cermet sintered body was manufactured, and then a chamfer honing process with a width of 0.15 mm and an angle of 20 degrees was performed on the cutting edge portion, thereby forming a TiCN-based cermet cutting tool of the present invention shown in Table 2 (hereinafter referred to as “the present invention”). 1-8 "were produced.

For comparison, the raw material powders A to D having the composition and average particle diameter shown in Table 1 were charged into a pulverization / mixing apparatus using spherical hard media having the diameter shown in Table 3, and the time shown in Table 3 was obtained. After performing the crushing and mixing treatment, press molding was performed at a pressure of 150 MPa to produce a green compact having a shape defined by ISO · SEEN1203AFTN1.
Next, the green compact was sintered and chamfer honing processed under the same conditions as in Example 1, so that TiCN-based cermet cutting tools (hereinafter referred to as “comparative example tools”) 1 to 3 shown in Table 3 were used. 8 was produced.

Next, with respect to the present invention tools 1 to 8 and comparative tools 1 to 8, a high-speed milling cutting test is performed under the conditions shown below, and the flank wear width of the cutting edge is measured. The presence or absence was observed.
Work Material: JIS / S45C
Cutting speed: 220 m / min (normal speed is 150 m / min)
Cutting depth: 1.0mm
Single blade feed amount: 0.15 mm / tooth
Cutting fluid: Water-soluble Cutting time: 20 min
Table 4 shows the results of the cutting test.

According to Tables 2-4, the present invention tools 1-8 produced using the TiCN-based cermet powder produced by the production method of the present invention exhibit excellent wear resistance in a high-speed milling cutting test, The occurrence of defects and chipping was extremely small.
On the other hand, the comparative tools 1 to 8 had a very short life because chipping or chipping occurred, or the wear width progressed abnormally from cracks before chipping.

The raw material powders A to D having the blending ratios shown in Table 1 were charged into a pulverization / mixing apparatus using spherical hard media having the diameters shown in Table 5, and the pulverization / mixing treatment I was performed for the times shown in Table 5. Then, after the slurry was guided to the grinding / mixing apparatus II using the spherical hard media having the diameter shown in Table 5, the grinding / mixing process II was performed, and then returned to the grinding / mixing apparatus I again. It was. The pulverization / mixing treatments I and II were carried out for the time shown in Table 5.
Thereafter, it was press-molded at a pressure of 150 MPa to produce a green compact having a shape defined by ISO · CNMG120408.
Next, the green compact is heated from room temperature to 1470 ° C. in a vacuum atmosphere of 13 Pa or less, and then nitrogen is introduced to form a nitrogen atmosphere of 133 Pa. The powder is held at 1470 ° C. for 1 hour and sintered, and TiCN A base cermet sintered body was manufactured, and then the cutting edge portion was round-honed with a radius of 0.03 mm, so that the cutting tool made of TiCN base cermet of the present invention shown in Table 5 (hereinafter referred to as “the present invention tool”) 11 was prepared. -18 were produced.

For comparison, the raw material powders A to D having the composition and average particle diameter shown in Table 1 were charged into a pulverization / mixing apparatus using a spherical hard medium having the diameter shown in Table 6, and the time shown in Table 6 was obtained. After the pulverization / mixing treatment, press molding was performed at a pressure of 150 MPa to produce a green compact having a shape defined by ISO / CNMG120408.
Next, the green compact was sintered under the same conditions as in Example 1 and round-honed to produce a TiCN-based cermet cutting tool (hereinafter referred to as “comparative example tool”) 11 shown in Table 6. -18 were produced.

Next, with respect to the above-mentioned inventive tools 11 to 18 and comparative tools 11 to 18, an intermittent cutting test of the alloy steel is performed under the conditions shown below, and the flank wear width of the cutting blade is measured. The presence or absence of chipping was observed.
Work material: JIS SCM440 4-slot slit material Cutting speed: 250 m / min
Cutting depth: 0.5mm
Feed: 0.2mm / rev
Cutting fluid: Water-soluble Cutting time: 16 min
Table 7 shows the results of the cutting test.

According to Tables 5 to 7, the present invention tools 11 to 18 produced using the TiCN-based cermet powder produced by the production method of the present invention exhibit excellent wear resistance in intermittent cutting of alloy steel. The occurrence of defects and chipping was extremely small.
On the other hand, the comparative tools 11 to 18 had a very short life because chipping or chipping occurred, or the wear width progressed abnormally from cracks before chipping.

As described above, according to the TiCN-based cermet powder manufacturing method of the present invention and the TiCN-based cermet sintered body, a titanium carbonitride-based cermet cutting tool having excellent toughness can be obtained, and this has a strong load on the cutting edge. Even when used in severe cutting conditions such as high-speed rolling and turning of steel with interrupted parts, it exhibits excellent chipping resistance and excellent wear resistance, as well as fracture resistance and resistance. A cutting tool made of TiCN-based cermet having excellent wear characteristics can be provided.

Claims (3)

It is a manufacturing method of TiCN base cermet powder, Comprising: 5-15 mass% of cobalt powder with an average particle diameter of 1.5 micrometers or less, 2-10 mass% of nickel powder with an average particle diameter of 3.0 micrometers or less, and an average particle diameter 20 to 40% by mass of one or more carbide powders of tungsten, molybdenum, tantalum, or niobium having a particle size of 3.0 μm or less, and the balance is a titanium carbonitride powder having an average particle size of 0.5 to 3.0 μm. When the raw powder is pulverized and mixed in a container using a liquid solvent and spherical hard media,
The crushing process using the spherical hard medium having a relatively large diameter D is performed for 20 minutes to 1 hour, and then the crushing process using the spherical hard medium having a relatively small diameter d and the relatively large diameter are performed. The crushing process using the spherical hard medium having D is circulated and repeated for 1 to 6 hours , and the diameter D of the spherical hard medium having a relatively large diameter used in the crushing process is 5.0 to 20. TiCN-based cermet powder having a diameter d of 0 mmφ and a diameter d of the relatively small spherical hard media used in the crushing treatment satisfies a relationship of d / D = 0.08 to 0.16 Manufacturing method. A method for producing a TiCN-based cermet sintered body , wherein the TiCN-based cermet powder obtained by the production method according to claim 1 is molded and then sintered. A method for producing a TiCN-based cermet cutting tool, wherein the TiCN-based cermet powder obtained by the production method according to claim 1 is molded and then sintered.