JPH04143204A - High hardness complex sintered body for tool - Google Patents

Abstract

PURPOSE:To develop a high hardness complex sintered body for tool having excellent performance by arranging a high hardness sintering body containing CBN, diamond, etc., through coating layer composed of TiC, TiN, TiCN, etc., on both surfaces of a cemented carbide alloy-made basis plate and integrally sintering it. CONSTITUTION:The high hardness sintering bodies 14 containing at least >=30vol% one kind either high hardness material of CBN (cubic system boron nitride) or diamond, etc., are arranged on both surfaces of the sintered hard alloy-made base plate 12 of WC-Co series, etc., through the coating layer 13 having 3-20mu thickness, composed of one kind either TiC, TiN or TiCN and integrally sintered. The high hardness complex sintered body 11 obtd. in such way, is suitably removes with a part of the high hardness sintered body 14 and the coating layer 13, and after exposing a part of the base plate 12 composed of the cemented carbide alloy, a part of this exposed base plate 12 is brazed and stuck to a tool body, and the remaining high hardness sintered body part 14 and the cemented carbide alloy 12 are machined to form an edge.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-hardness composite sintered body for a tool, which is suitable for use as a cutting edge of a cutting tool such as a ball end mill.

[Conventional technology] Cubic boron nitride (hereinafter referred to as CBN) is used for the cutting edge of this type of cutting tool.
It is abbreviated as ) or diamond, the hardness of the sintered body and the steel that makes up the tool body may be poor in wettability or may not be able to be applied to the tool body using methods such as brazing. Since it is difficult to join, a high-hardness sintered body is sintered with a cemented carbide such as WC to form a composite sintered body, and the cemented carbide part of this composite sintered body is brazed to make tools. A method is used to attach it to the main body.

As such a composite sintered body, for example, Japanese Patent Application Laid-Open No. 61-3
4108 and the structure shown in Japanese Unexamined Patent Publication No. 61-266364 are known. As shown in FIG. 5, this composite sintered body 1 has a high hardness sintered body 2 containing CBN, diamond, etc. sandwiched between layers 3 of cemented carbide or cermet.
It has a sandwich structure in which these are sintered together.

In order to use such a composite sintered body l for the cutting blade of a ball end mill, for example, the rotation axis C of the tool body 4 at the tip of the tool body 4 of the ball end mill must be The composite sintered body l formed into a semicircular plate shape is fitted into the groove fKI5 formed in the plane including the groove fKI5 and soldered.

After that, change the direction of rotation when using the ball end mill (7th direction).
The cemented carbide or cermet layer 3 in the portion facing Fi (counterclockwise in the figure) is removed to expose the high hardness sintered body 2 and form the cutting edge 6.

In the ball end mill configured in this way, the cutting edge is C.
Since it is made of a high hardness sintered body containing BS and diamond, it has the advantage that the cutting edge has high wear resistance.

[Problem to be solved by the invention] By the way, in such a ball end mill, a large thrust load acts on the cutting edge portion on the rotation axis of the tool body, that is, the center blade portion, and the cutting speed is low in this portion. Therefore, cutting resistance also becomes extremely large. Therefore, if a high-hardness sintered body, which has high hardness but poor toughness, is located at the center edge as in the conventional example, the cutting edge will break at the center edge, causing the tool to become damaged. This results in a reduction in service life.

In order to solve these drawbacks, a ball end mill as shown in FIGS. 8 and 9 has been proposed. This is described in Utility Application No. 1-41860, and a rod-shaped tip 7 made of cemented carbide is mounted on the rotation axis C at the tip of the tool body 4.
At the same time, a composite sintered body 8 consisting of two layers of a high-hardness sintered body 2 and a cemented carbide 3 was placed between the rod-shaped tips 7 and within the area including the rotating shaft C. These cemented carbide tips 7 and the high hardness sintered body 2 of the composite sintered body 8 continuously form a cutting edge. In a ball end mill with such a configuration, the parts of the cutting blade other than the center edge, that is, the outer peripheral edge, are made of a high-hardness sintered body with high wear resistance, and the center edge part is made of this high-hardness sintered body. Since it is made of cemented carbide, which has higher toughness than the body, it is possible to avoid damage to the center edge due to large thrust loads and cutting resistance.

However, although this kind of ball end mill prevents the center cutting edge from breaking, the boundary between the center cutting edge and the peripheral cutting edge is joined by brazing, which causes severe wear during cutting, which also shortens the tool life. The problem was that the time period was significantly shortened.

On the other hand, such a composite sintered body is produced by adding carbon to a high hardness sintered body, for example.
When using BS, a compact formed by pressing a mixed powder of CBN and a binder such as TiN or TIC is placed on top of the cemented carbide that has already been sintered, and then sintered under ultra-high pressure and high temperature. It is manufactured by connecting the However, this sintering temperature is
Since the eutectic temperature of C (cemented carbide) is exceeded, the Co component in the cemented carbide during sintering is in a molten state, and on the other hand, the sintering of the CBN layer is a solid phase sintering of CBN and the binder. So,
A so-called infiltration phenomenon occurs in which the Co component in the cemented carbide, which has melted near the interface between the CBN layer and the cemented carbide, penetrates into the CBN layer due to capillary action and pressure difference until both are completely sintered. may occur.

This infiltration phenomenon stops as the sintering of the CBN layer is completed after a certain amount of time has passed, but since the infiltrating Co component is supplied from within the cemented carbide, A Co-enriched layer and a Co-depleted layer may be formed in the alloy portion. In this way, if an enriched layer and a depleted layer of COF7g are formed and segregation of Co components occurs in the cemented carbide, the original properties of the cemented carbide may be impaired.
When used as a tool material, there is a risk that peeling may occur at the interface between the cemented carbide portion and the CBN layer, making it impossible to obtain the desired performance.

[Means for Solving the Problems] The present invention has been made to solve the above problems, and
On both sides of a substrate made of cemented carbide, 30 volumes of cubic boron nitride, diamond, or a mixture thereof is applied via a coating layer of 3 to 20 μm thick made of one of TiC, TiN, and TiCN. %
The present invention is characterized in that a high-hardness sintered body containing the above components is provided, and the cemented carbide, the coating layer, and the high-hardness sintered body are sintered together.

[Function] The present invention applies a high-hardness sintered body containing at least 30% by volume of CBS, diamond, or a mixture thereof on both sides of a cemented carbide through a coating layer of TiC, TiN, TiCN, etc. It has a sandwich structure. Then, a high hardness composite sintered body with such a configuration,
For example, when used in the blade body of a tool such as the aforementioned Whole Et Mill, by removing the sintered body layer on the rear side in the rotational direction of the tool and attaching it to the tip of the tool body, the sintered body can be removed from the peripheral edge part. In addition, it is possible to provide a blade body in which the central blade part is made of cemented carbide and these blades are integrally molded.

This imparts toughness to the central blade while maintaining the wear resistance of the outer peripheral blade, thereby suppressing damage to the central blade due to thrust loads and cutting resistance during cutting. Moreover, since the center blade and the peripheral blade are integrally molded, there is no risk of the parts being worn out during brazing.

Furthermore, in the present invention, the cotinog layer of TiC, TiN, or TiCN placed between the high-hardness sintered body and the cemented carbide suppresses the infiltration of the Co component in the cemented carbide.
Segregation of the Co component in the cemented carbide can be prevented.

[Example] FIG. 1 shows an example of the present invention. In this figure, a high-hardness composite sintered body 11 for tools has a substrate 12 made of cemented carbide.
And, TiC is applied to both sides of this substrate 12.

A coating layer with a thickness of 3 to 20 μm made of either TiN or TiCN! The high-hardness sintered body 14 contains at least 30% by volume of CBN, diamond, or a mixture thereof disposed through the cemented carbide substrate 12 and the coating layer 13. , and the high-hardness sintered body 14 are integrally sintered and formed.

Such a high-hardness composite sintered body 11 is produced by appropriately removing a portion of the high-hardness sintered body portion 14 and coating layer 13 to expose a portion of the substrate 12 made of cemented carbide. The base plate 12 is fixed to the tool body by brazing a part of the base plate 12. Then, the remaining high-hardness sintered body portion 14 and cemented carbide 12 are processed to form a cutting edge, thereby providing a blade body for a cutting tool or the like.

On the other hand, in the present invention, Ti is added between the cemented carbide and the high-hardness sintered body.
A coating layer made of C, TiN, or TiCN is interposed.

The presence of this coating layer suppresses infiltration of Co components during sintering under ultra-high pressure and high pressure, and therefore prevents segregation of Co components in the cemented carbide, thereby preventing loss of properties of the cemented carbide. Peeling between the cemented carbide part and the high hardness sintered body part can be prevented.

If the thickness of the coating layer 13 is less than 3 μm, the Co component in the cemented carbide will infiltrate into the boundary during sintering under ultra-high pressure, whereas if the thickness of the coating layer 13 exceeds 20 μm, the Hard alloy substrate 12 and high hardness sintered body 1
4, and there is a risk of it peeling off due to cutting resistance when used as a tool blade.
Both are undesirable. Further, if the volume of CBS, diamond, or a mixture thereof contained in the high-hardness sintered body 14 is less than 30% by volume, the high-hardness sintered body 1
These are undesirable because the hardness is lower than 4, and when used as a tool blade, the wear of the cutting edge and the tooth surface is greatly accelerated.

Next, with reference to FIGS. 2 and 3, the case where the present invention is applied to the blade of a pole end mill will be described.

In these figures, the tool body 21 is the head part 2 on the tip side.
2, and a noyank part 23 on the proximal end side that is coupled and integrated with this head part 22, and is rotated about a rotation center C and used for cutting. The tip of the head portion 22 of this tool body 21 is formed into a substantially hemispherical shape, and a semicircular groove portion 2 is formed along a plane including the rotation center C.
4 is formed. Further, a chip pocket part 25.25 is formed on the front side of the groove part 24 in the tool rotation direction during cutting (counterclockwise direction in FIG. 3) for discharging chips generated by cutting.

The groove portion 24 is formed into a semi-disc shape, and the high hardness sintered body and the coating layer located on the rear side in the tool rotation direction are removed to form a cemented carbide surface 12A on the rear side in the tool rotation direction. The exposed high-hardness composite sintered body 11 for tools is fitted, and its exposed cemented carbide surface! 2A and the groove portion 24 opposite thereto are fixed to the head portion 22 by being joined by brazing or the like. Furthermore, a cutting edge is formed in the high-hardness sintered body portion 14 of the high-hardness composite sintered body II located on the front side in the tool rotation direction, and forms an outer peripheral edge 26, and is located on the rotation center C. A cutting edge is also formed on the cemented carbide portion 12 located there, and serves as a center edge 27.

These outer peripheral blades 26 and central blades 27 are made of high hardness composite sintered bodies! It is continuously formed in the circumferential direction of X to constitute the blade body of the ball end mill.

In a ball end mill with such a configuration, the peripheral cutting edge is CB.
It is made of a high hardness sintered body containing S and diamond, and the center blade is made of cemented carbide, and these cutting blades are integrally molded. This makes it possible to impart toughness to the center blade while maintaining the excellent wear resistance properties of high-hardness sintered bodies, and prevents breakage of the center blade due to large thrust loads and cutting resistance. can.

In addition, since the center blade and the peripheral blade are integrally molded as a composite sintered body, the peripheral blade and the central blade cannot be molded separately as in the conventional examples shown in Figs. 8 and 9. Compared to the case where these parts are joined by brazing or the like, there is no risk of wear of the parts by brazing, and the durability of the tool can be improved.

Although an example in which the present invention is used in a ball end mill has been described here, it is also possible to use the present invention in a cutting blade of a normal end mill, for example.

[Experiment example] Experimental examples will be given below to demonstrate the effects of the present invention.

In the first experimental example, cutting work was performed using a ball end mill according to the present invention as shown in Figs. 2 and 3 under certain processing conditions, and the processing time and
The relationship between wear on the flank surfaces of the center cutting edge and the peripheral cutting edge was measured.

In addition, as a comparative example, a ball end mill using the composite sintered body shown in Figs. 6 and 7 and a ball end mill using the high hardness sintered body shown in Figs. 8 and 9 under the same processing conditions. A similar cutting operation was performed using a ball end mill in which a peripheral blade and a cemented carbide center blade were joined by brazing, and the relationship between machining time and wear on the flank surfaces of the central blade and peripheral blade was measured.

The results are shown in FIG. However, in the figure, the symbol A1
and A shows the relationship between the machining time and flank wear of the central blade and the peripheral blade in this experimental example in which the central blade is made of cemented carbide and the peripheral blade is a CBN sintered body. Also, symbols B1 and B refer to the center blade and the comparative example in which the center blade is made of cemented carbide and the peripheral blade is made of CBN sintered body, and the center blade and the peripheral blade are separate bodies and are joined by brazing. This figure shows the relationship between machining time and flank wear of the peripheral cutting edge. Furthermore, the symbol C indicates the relationship between machining time and flank wear of a comparative example in which both the center blade and the peripheral blade are made of a CBN sintered body and these are integrally molded.

Note that the processing conditions are as follows.

Cutting speed: 500 m/min Feed: 4000 am/win Rotation speed: -530 Orpm Big feed: 0.5 mm Stock removal: 10 to 14 mm Tool diameter: φ30 mm Work material: Fe25 Results shown in Figure 4 According to the Comparative Example shown in Figures 6 and 7, the wear of the center blade rapidly progressed from 5 minutes after the start of machining, and the center blade broke 8 minutes after the start of machining, resulting in failure in subsequent experiments. became impossible. In addition, in the comparative examples shown in Figures 8 and 9, although the wear on the outer edge was within an acceptable range, the center edge, especially the outer edge, showed significant wear immediately after the start of the experiment. This tendency became more noticeable from around 20 minutes after the start of processing.

In contrast to these comparative examples, in this experimental example, both the center blade and the peripheral blade showed stable wear, and the wear was within a sufficiently tolerable range and did not interfere with cutting work.

Next, as a second experimental example, TiN was added to the coating layer.
Using TiC1 and TiCN, we created several high-hardness composite sintered bodies for tools with different coating layer thicknesses, and used them as cutting edges using the ball end mill shown in Figures 2 and 3. Cutting was performed under the processing conditions described above.

The wear condition and damage of the composite sintered body at this time are shown in the table below.

From this table, it can be seen that when the thickness of the coating layer is 3 to 20 μm, the blade shows normal wear, whereas when the thickness of the coating layer is less than 3 μm, the center blade is made of cemented carbide. On the other hand, when the thickness of the coating layer increases to more than 20 μm, it can be seen that peeling defects occur from the coating layer portion at the boundary between the center blade and the peripheral blade.

This wear of the center blade is caused by the fact that when the coating layer is less than 3μ, the coating layer is too thin and infiltration of the Co component during sintering cannot be suppressed, and the Co component segregates within the cemented carbide. This is thought to be due to the loss of the original properties of the alloy. On the other hand, when the coating layer becomes thicker than 20 μm, peeling defects between the center blade and the peripheral blade will inhibit sintering between the cemented carbide and the high-hardness sintered body, significantly impairing the bonding properties between the two. This is thought to be caused by the

[Effects of the Invention] As explained above, in the present invention, the coating layer interposed between the high-hardness sintered body and the cemented carbide removes the Co component from the entire cemented carbide portion to the high-hardness sintered body portion. Infiltration is suppressed, segregation of Co components within the cemented carbide is prevented, and the properties unique to the cemented carbide are not impaired.

Furthermore, when such a composite sintered body is used for the blade body of a cutting tool such as a pole mill, the outer peripheral edge is made of a high-hardness sintered body, the center blade is made of a cemented carbide, and These can be molded into one piece. This makes it possible to add toughness to the center edge while maintaining high wear resistance on the outer edge, preventing damage to the center edge due to high cutting resistance and thrust loads, and also preventing damage to the center edge due to high cutting resistance and thrust loads. The durability of the tool can be improved without causing wear at the boundary with the center cutting edge.

[Brief explanation of drawings]

FIG. 1 shows one embodiment of the present invention, and FIGS. 2 and 3 show examples of the use of this in the blade of a ball end mill. Further, FIG. 4 shows an experimental example showing the effects of the present invention and a comparative example thereto. Furthermore, Fig. 5 is an example of a conventional composite sintered body, and Fig. 6 shows an example of a conventional composite sintered body.
7 and 7 show examples of ball end mills using this for the blade body, and FIGS. 8 and 9 show examples of hole end mills in which separately molded center blades are joined by brazing or the like. 11 High hardness composite sintered body for tools, 12 Cemented carbide, 13 Coating layer, 14 High hardness sintered body, 21 Ball end mill, 22 Head part, 23 Yank part, 24 Groove part,
25 Pocket portion, 26 - Peripheral blade, 27 Center blade, C Tool rotation center, A + , At... Wear condition of central blade and peripheral blade in experimental examples of the present invention, B 1. B t , C - Wear condition of the center blade and outer peripheral blade in a comparative example.

Claims (1)

[Claims] A substrate made of cemented carbide with a thickness of 3 to 20 μm made of any one of TiC, TiN, and TiCN on both sides.
A high-hardness sintered body containing 30% by volume or more of cubic boron nitride, diamond, or a mixture thereof is disposed through a coating layer of these cemented carbide,
A high-hardness composite sintered body for tools, characterized in that a coating layer and a high-hardness sintered body are integrally sintered.