KR102124566B1 - Manufacturing Methods of cBN Sintered Tool With High Hardness - Google Patents

Abstract

A method of manufacturing a high hardness cBN sintered body tool is disclosed. The present invention is a method for manufacturing a cBN sintered body comprising a cBN particle phase and a binding phase between the cBN particles, filling a raw material composition powder comprising cBN powder and Al, Co, and W source powder on a cemented carbide substrate ; And it provides a method for producing a cBN sintered compact tool comprising the step of sintering the raw material powder by hot pressing. According to the present invention, it is possible to provide a cBN sintered body tool having a particulate and bonded phase structure suitable for processing a Ni-based heat-resistant alloy workpiece.

Description

Manufacturing method of high hardness cBN sintered body {Manufacturing Methods of cBN Sintered Tool With High Hardness}

The present invention relates to a method for manufacturing a high hardness cBN sintered body tool and a cBN sintered body tool produced thereby.

Cubic boron nitride (cBN) has the highest hardness and excellent thermal conductivity after diamond, and has lower reactivity with iron than diamond. For this reason, a tool containing cubic boron nitride has been used for finishing cutting of cast iron or finishing sintered alloys and difficult-to-cut materials at high speed.

The materials of the cBN sintering tool can be classified into two types, the first being that the cBN content is high, so that the cBN is bound to each other and the remainder is made of the bonding material, the second is the cBN content is relatively low, the contact ratio between cBN is low, and the reactivity with iron This is a sintered body that is bonded through ceramics made of low Ti nitride (TiN) or carbide (TiC).

When a cBN sintered body tool having a high cBN content is applied to the cutting of a difficult-to-cut material having low ductility, friction heat generated in the processing part during the cutting process spreads to the cBN sintered body due to the high thermal conductivity of the cBN particles, thereby cutting. When the workpiece is not maintained at a high temperature, the cutting efficiency is significantly reduced. That is, a high cBN-containing sintered body having a cBN sintered body component of 80% by volume or more has a high thermal conductivity, and friction heat generated by processing escapes from the cBN sintered body. As a result, the heat generated in the machining is not sufficiently conducted to the work piece and the work piece is not softened, so the tool is loaded.

Due to such a problem, in the cutting of the iron-based sintered alloy, a problem arises in that the temperature of the workpiece is insufficient and the machining surface is torn and the roughness of the machining surface increases. In addition, if the cutting speed is increased to improve the roughness, the wear progresses rapidly and the desired tool life cannot be obtained. Particularly, in the case of cutting a Ni-based heat-resistant alloy having a high temperature and hardness, the work piece is hard to soften, and thus the cBN sintered body is liable to be defective.

On the other hand, when the content of cBN is less than 80% by volume, the thermal conductivity is relatively low, so that the heat of processing is difficult to flow into the cBN sintered body tool, and rapid quenching of the workpiece can be suppressed. However, there is a problem in that the cBN sintered body tool is deteriorated early because the number of bonding phases having lower strength and toughness is higher than that of cBN particles.

When the content of cBN particles is increased as described above, there is a problem in that it is difficult to satisfy both at the same time because the increase in hardness of the tool and the decrease in thermal conductivity are related to trade-offs.

(1) Korean Registered Patent No. 1270840

The present invention aims to provide a cBN sintered body tool that improves the hardness of a tool suitable for cutting Ni-based heat-resistant alloys such as Inconel and suppresses defects in the cBN sintered body in order to solve the above-mentioned prior art powdering point.

In addition, an object of the present invention is to provide a method for manufacturing a cBN sintered body tool having a bonding phase capable of withstanding the high heat experienced during continuous processing.

In addition, an object of the present invention is to provide a method for manufacturing a cBN sintered body tool having a particulate and bonded phase structure suitable for processing a Ni-based heat-resistant alloy workpiece.

In addition, an object of the present invention is to provide a manufacturing method for manufacturing the above-mentioned cBN sintered body tool.

In order to achieve the above technical problem, the present invention is a method of manufacturing a cBN sintered body comprising a cBN particle phase and a binding phase between the cBN particles, comprising cBN powder and Al, Co, and W source powder on a cemented carbide substrate. Filling the raw material composition powder; And it provides a method for producing a cBN sintered compact tool comprising the step of sintering the raw material powder by hot pressing.

In the present invention, the cBN powder may have an average particle diameter of 1 to 2 μm. In addition, it is preferable that the substrate made of cemented carbide includes WC-Co.

In the present invention, the sintering step is preferably carried out at a pressure of 4.0 GPa or more, preferably 5.0 GPa or more at a temperature of 1400-1500K.

In the present invention, the Al source is Al ₂ O ₃ , and the W source may be WC.

In order to achieve the other technical problem, the present invention, in a tool comprising a cBN sintered body comprising a cBN particulate phase and a binding phase between the cBN particles, the cBN particulate phase has a volume fraction in the sintered body of 89-96%, Provided is a cBN sintered compact tool, characterized in that the Vickers hardness value is 3900 to 4100 Hv.

In the present invention, the cBN particulate phase preferably has a volume fraction of 90 to 92% in the sintered body. At this time, the average particle diameter of the cBN particles is less than 2 μm, preferably 1 to 1.5 μm.

In the present invention, it is preferable that the metal element of the binding phase component is composed of Al, Co and W.

According to the present invention, it is possible to provide a cBN sintered body tool that improves the hardness of the tool to suppress the defect of the cBN sintered body so as to be suitable for cutting Ni-based heat-resistant alloys such as Inconel.

In addition, according to the present invention, it is possible to provide a cBN sintered body tool having a bonding phase capable of withstanding the high heat experienced during continuous processing.

Further, according to the present invention, it is possible to provide a cBN sintered body tool having a particulate and bonded phase structure suitable for processing a Ni-based heat-resistant alloy workpiece.

1 is a photograph of a cutting performance evaluation result according to an embodiment of the present invention.
Figure 2 is a photograph taken in cross section of the BN7000 sample and the 3-9 specimen of the present invention.

Hereinafter, the present invention will be described by describing preferred embodiments of the present invention with reference to the drawings.

In the context of the present invention, the cBN particulate phase refers to the cBN particle portion in the cBN sintered body tool. In addition, the binding phase refers to a phase composed of components other than cBN connecting cBN particles between cBN particles. In the cBN sintered body of the present invention, cBN particles may be bonded to each other or cBN particles may be bonded through a bonding phase.

In the present invention, the cBN sintered body tool includes a cBN particle phase and a binding phase as a binder for binding cBN particles. The sintered body tool of the present invention keeps the volume fraction of the bonding phase which is lower in strength and toughness than cBN particles to a minimum.

Preferably, in the cBN sintered body of the present invention, the volume fraction of the binding phase may be less than about 11% by volume, less than about 10%, less than about 8%, and less than about 4%. Preferably, the binding phase volume fraction is preferably 8-10%.

In addition, the average particle diameter of the cBN particles on the cBN particles of the cBN sintered body of the present invention is preferably about 1 to 2 μm, preferably about 1 to 1.5 μm. As described above, the present invention has a high cBN particulate fraction while the cBN particles have a low average particle diameter. The characteristics of the microstructure can bring the following advantages. First, the cBN sintered body of the present invention has a high hardness. In addition, the cBN sintered body has a lower cBN particle size, thereby providing more cBN particle-cBN particle interfaces and cBN particle-bonded phase interfaces, which act as a heat conduction resistance by scattering heat. Therefore, it is possible to maintain the workpiece at a high temperature despite the high cBN particulate fraction. Accordingly, a heat-resistant alloy such as Inconel can be processed at high speed for a long time.

In the present invention, the cBN sintered body may have a Vickers hardness value of 3900 to 4100 Hv. Here, the Vickers hardness is a value measured for 5 seconds under a 5 kg load with a diamond indenter in the FUTURE TECH FV-7 hardness tester.

In the present invention, the metal element of the bonding phase is composed of Al, Co and W. In other words, the use of a metal element such as Ti is excluded from the bonding phase of the cBN sintered body of the present invention. Further, in the present invention, the source of the metal element may be provided in various forms. For example, the metal element may be provided in a metal form, or may be provided in the form of a metal compound such as metal hydroxide, metal oxide or metal carbide. For example, Al may be provided in the form of Al ₂ O ₃ , W WC.

In the present invention, the Al content of the metal elements constituting the bonding phase is preferably 0.1% by weight to 1.0% by weight.

Hereinafter, preferred embodiments of the present invention will be described.

<Example 1>

As a raw material powder, a cBN powder having an average particle diameter of 2 μm and an Al, W, and Co precursor as a binder were mixed at an appropriate ratio to prepare a raw material composition powder. At this time, the blending ratio was adjusted so that the volume fraction of cBN in the sintered body was as shown in Table 1.

The substrate of the rectangular parallelepiped container was charged with a cemented carbide substrate, and the raw material composition powder was charged, followed by high pressure high temperature sintering in an Ar atmosphere (5,000 tons of ELWOOD Press). At this time, the sintering pressure was 4.2 GPa per unit area based on the internal cell, and the sintering temperature was 1400K.

The hardness of the prepared sintered body was measured. Hardness was measured with a Vicker hardness tester (FUTURE TECH; FV-7) 5 kgf.

Table 1 is a table showing the cBN content and hardness measurement results of the sintered body specimen prepared in this example.

Psalter cBN (vol.%) Grain Size (㎛) Sintering pressure (GPa) Sintering temperature (K) Hardness (HV) 1-1 65 2 4.2Gpa 1400K 2856 1-2 80 2 4.2Gpa 1400K 3053 1-3 92 2 4.2Gpa 1400K 1908

As shown in Table 1 above, as the cBN content increased from 65Vol% to 80Vol%, the hardness value increased. However, when the cBN content increased from 80Vol% to 92Vol%, the material hardness decreased after sintering. In these results, the change in material hardness is not limited to the cBN content, but it is expected that there will be another factor.

In addition to the constituent raw materials, the factors that change the hardness of general powder metallurgy materials are temperature and pressure conditions applied to the powder during sintering. Since pCBN is also manufactured by applying powder metallurgy, the temperature, pressure conditions and materials applied during sintering It is expected to be related to the amount of change in hardness.

<Example 2>

As in Example 1, a raw material composition powder was prepared, and ultra high pressure ultra high temperature sintering was performed. At this time, unlike Example 1, the sintering temperature was varied from 1400 to 1500 K.

Table 2 is a table showing the cBN content and hardness measurement results of the sintered body specimen prepared in this example. For comparison, the properties of Sumitomo's BN7000 grade are also shown.

Psalter cBN (vol.%) Grain Size (㎛) Sintering pressure (GPa) Sintering temperature (K) Hardness (HV) BN7000 85~90 3(Main) - - 3,874 2-1 65 2 4.2 1,400 2,856 2-2 65 2 4.2 1,470 3,071 2-3 65 2 4.2 1,500 3,167 2-4 80 2 4.2 1,400 3,053 2-5 80 2 4.2 1,470 3,201 2-6 80 2 4.2 1,500 3,394 2-7 92 2 4.2 1,400 1,908 2-8 92 2 4.2 1,470 1,980 2-9 92 2 4.2 1,500 2,162

It can be seen from Table 2 that the physical properties of the material hardness tend to increase as the sintering temperature increases, regardless of the cBN content. In addition, when the cBN content was 80 vol%, the material hardness was high on average, and showed the highest material hardness at a temperature of 1500K. In order to improve the hardness, sintering pressure evaluation was additionally performed among the sintering conditions.

<Example 3>

As in Example 1, a raw material composition powder was prepared, and ultra high pressure ultra high temperature sintering was performed. At this time, unlike Example 1, the sintering temperature was set to 1500 K, and the sintering pressure was changed.

Table 3 is a table showing the cBN content and hardness measurement results of the sintered body specimen prepared in this example. For comparison, the properties of Sumitomo's BN7000 grade are also shown.

Psalter cBN (vol.%) Grain Size (㎛) Sintering pressure (GPa) Sintering temperature (K) Hardness (HV) BN7000 85~90 3(Main) - - 3,874 3-1 65 2 4.2 1,500 3,167 3-2 65 2 4.8 1,500 3,250 3-3 65 2 5.0 1,500 3,324 3-4 80 2 4.2 1,500 3,394 3-5 80 2 4.8 1,500 3,652 3-6 80 2 5.0 1,500 3,774 3-7 92 2 4.2 1,500 2,162 3-8 92 2 4.8 1,500 3,510 3-9 92 2 5.0 1,500 3,992

Referring to the above results, the change in material hardness occurs according to the cBN content, but it was found that it shows the most influence on the temperature and pressure conditions applied during sintering. As a result, on average, as the cBN content increases, the temperature and pressure required for sintering must be increased, and it can be seen that the owner who changes the hardness of the material is the temperature and pressure applied during sintering.

<Experimental Example 1>

Cutting performance was evaluated using the 3-9 specimen of Example 3. For comparison, Sumitomo's BN7000 tool and Iljin Diamond's SB95S2 tool were evaluated together. The image analysis results of BN 7000 and SB95S2 are as follows. In the table, Main is 50% or more of the total weight ratio, and Sub is the weight ratio of 50% or less.

division BN7000 SB95S2 cBN content (Vol.%) 85~90 > 90 cBN particle size
(㎛) Min. 0.06 0.06 Max. 4.37 5.26 Main 3.30 1.00 Sub 1.10 0.00

Table 5 shows the cutting performance evaluation conditions.

Workpiece Inconel 718 Cutting method Turning
Continuous Equipment, coolant PUMA2600 Insert dimensions CNGA120408 T01225 Holder specification PCLNL 2525 M12N Cutting condition Main speed (m/min.) 120.0 Feed (mm/rev.) 0.12 Infeed (mm) 0.5 Cooling method Wet

1 is a photograph of the cutting performance evaluation result of the present embodiment. As shown in Fig. 1, the cutting performance and abrasion resistance of the 3-9 specimen were the best.

The performance of a cBN tool depends on the density of the cBN particles, the nature of the bonding phase, and the amount of cBN direct binding. The 3-9 specimen of the present invention is judged to have excellent abrasion resistance because the cBN particle size is small and the distance between particles is small and the density of cBN particles is high compared to the two grades of comparison, BN7000 and SB95S2. It is also judged that the heat resistance of the bonding phase, which affects the life of the tool, is relatively strong.

After machining, the wear condition of the tool had the lowest 3-9 specimens in both the top and side wear, and the chipping wear of the tool also had the lowest 3-9 specimens. This is believed to be due to the increased amount of cBN direct binding in the 309 specimen.

Image analysis of the samples was performed in the prepared examples. Figure 2 is a photograph taken in cross section of the BN7000 sample and the 3-9 specimen of the present invention.

It can be seen that the BN7000 sample shown in FIG. 2(a) has a larger particle size than the 3-9 specimen of FIG. 2(b), and the size of the binding phase pocket is also large.

2(a) and 2(b), the data on the particle size on the picture are recorded. The average and standard deviation of the cBN particle size measured at a magnification of x3000 is shown in Table 2 below. For particle size, 40 random particles were selected at 3000 magnification in SEM BSE Mode, and a total of 80 data were measured and recorded along the horizontal/vertical axis.

division Average (㎛) Standard Deviation BN7000 2.43 0.50 3-9 Psalms 1.43 0.36

Table 7 shows the volume fractions of the cBN particulate phase and the binding phase. The volume fraction was calculated from the area fractions of the particulate and bonded phases in the 160 µm x 120 µm region, using magnification x3000 times electron micrographs at arbitrary cross sections of the specimen, and the average values in the three regions were taken. At this time, it was assumed that the area fraction in an arbitrary cross section is the same as the volume fraction. The area fraction was calculated using Clemex.

division Granular
(Volume fraction, %) Bonding phase
(Volume fraction, %) BN7000 87.9 12.1 3-9 Psalms 90.6 9.3

As shown in Table 7, the 3-9 specimen of the present invention shows a small value of the fraction of the bonding phase is less than 10%.

The preferred embodiments of the present invention have been described above, but the technical spirit of the present invention is not limited to the preferred embodiments described above, and may be variously implemented within a scope not departing from the technical spirit of the present invention as specified in the claims. have.

Claims (11)

In the method for producing a cBN sintered body comprising a cBN particle phase and a binding phase between the cBN particles,
Filling a raw material composition powder composed of cBN powder and Al, Co, and W source powders on a cemented carbide substrate; And
Sintering by pressing the raw material composition powder at a high temperature,
The substrate made of cemented carbide includes WC-Co,
The cBN powder has an average particle diameter of 1 to 2 μm,
The cBN particulate phase has a volume fraction in the sintered body of 90 to 92%,
The sintering step is a method of manufacturing a cBN sintered body tool, characterized in that performed at a pressure of 4.0 GPa or more at a temperature of 1400-1500K. delete delete delete According to claim 1,
The sintering step,
Method of manufacturing a cBN sintered body tool, characterized in that carried out at a pressure of 5.0 GPa or more at a temperature of 1400 ~ 1500K. According to claim 1,
The Al source is Al ₂ O ₃ , W source is a method of manufacturing a cBN sintered body tool, characterized in that WC. It is produced by the method according to any one of claims 1, 5, and 6,
CBN sintered compact tool, characterized in that the Vickers hardness value is 3900-4100 Hv. The method of claim 7,
The cBN particulate phase cBN sintered body tool, characterized in that the volume fraction in the sintered body is 90 to 92%. The method of claim 7,
CBN sintered body tool, characterized in that the average particle diameter of the cBN particles is less than 2 μm. The method of claim 7,
CBN sintered body tool, characterized in that the average particle diameter of the cBN particles is 1 to 1.5 ㎛. The method of claim 7,
The cBN sintered body tool, characterized in that the metal element of the bonding phase component is composed of Al, Co, and W.

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