JP2000052112A - Hard sintered compact throw-away tips - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a throwaway formed by providing a seat groove in a corner portion of a tool base material and brazing a hard sintered body such as a diamond sintered body or a cBN sintered body to the seat groove. Chips are susceptible to cracks and cracks in the hard sintered body during brazing if a recess is formed in the corner of the seat groove to reduce cost and eliminate interference with the edge of the hard sintered body. This problem is eliminated. SOLUTION: An intersection angle θ between an upright side surface 3a of a seat groove 3 and a seat bottom surface 3b is made smaller than an intersection angle of a back surface and a bottom surface of a hard sintered body 1 so that the corner portion of the seat groove 3 can be hardened without being dug down. A flat portion was formed to receive the lower edge of the rear surface of the sintered body 1 to eliminate a sudden increase in the thickness of the bonding brazing layer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away insert formed by brazing a hard sintered body (diamond sintered body, cBN sintered body) containing diamond or cubic boron nitride to a tool base material. About.

[0002]

2. Description of the Related Art A sintered diamond product obtained by sintering fine diamond particles under a high pressure and a high temperature using a binder such as an iron group metal is used for cutting tools, wire drawing dies, drill bits, and wear-resistant tools. When used as a cutting edge material, it shows much better wear resistance than conventional cemented carbide. In addition, a material obtained by sintering fine cubic boron nitride (cBN) using various binders exhibits excellent performance in cutting a high-hardness iron group metal or cast iron.

FIGS. 1 (a) and 2 (a) show a conventional hard sintered body throw-away chip employing these sintered bodies. In this indexable insert, the hard sintered body 1 is first brazed and joined to a seat groove 3 formed in a corner portion of a tool base material 2, and then a ridge line of the hard sintered body that becomes a cutting edge 4. It is obtained by polishing the part.

[0004]

SUMMARY OF THE INVENTION
This is performed using a brazing material containing Ag or Cu. During the brazing process, the hard sintered body is rapidly heated and cooled, and depending on the conditions, the hard sintered body may have cracks or cracks due to the difference in thermal expansion of the material near the joint with the tool base material. May occur. Particularly, in order to enhance the brazing strength, a hard sintered body using an active brazing material (a brazing material in which an active metal such as Ti or Zr is added to Ag or Cu to improve wettability with the hard sintered body) is used. When it is firmly joined to the tool base material, the aforementioned cracks and cracks are likely to occur depending on the shape of the seat groove.

FIGS. 1 (b) and 2 (b) show examples of cracks and cracks generated by brazing the rigid sintered body 1 of each indexable tip. The cracks and cracks mainly occur due to a difference in thermal expansion between the hard sintered body 1 and the joining brazing layer 7. With respect to the stress due to the difference in thermal expansion, as the thickness of the joining brazing layer 6 increases, the strain due to the shrinkage of the brazing material increases, and a stronger tensile stress is applied to the hard sintered body. In the conventional indexable insert, a recessed recess 5 is provided at the inner end of the upright side surface 3a of the seat groove 3 or the inner end of the seat bottom surface 3b in order to avoid interference with the lower lower edge of the hard sintered body 1. Since the thickness of the joining brazing layer 7 is rapidly increased at that portion, the tensile stress applied to the hard sintered body 1 is concentrated on the portion, and therefore, cracks and cracks are likely to occur near the position shown in the figure. .

[0006] In the throw-away tip having cracks and cracks, the cracks and cracks serve as starting points of destruction, resulting in a decrease in bonding strength, and during use, the hard sintered body falls off and the tool life is shortened. .

[0007] Therefore, an object of the present invention is to prevent cracks and cracks caused by brazing of a hard sintered body while obtaining high joining strength to a tool base material.

[0008]

In order to solve the above problems, according to the present invention, a hard sintered body containing diamond or cubic boron nitride is provided in a seat groove formed in a corner portion of a tool base material. In a throw-away insert in which the ridge of the hard sintered body is formed as a cutting edge by brazing, the intersection angle between the upright side surface and the bottom surface of the seat groove of the tool base material is set to the hard surfaces joined to those surfaces. The angle was smaller than the intersection angle between the bottom surface and the back surface of the sintered body.

The intersection angle between the upright side surface of the seat groove and the seat bottom surface is preferably in the range of 75 ° to 87 °.

It is preferable that the connecting portion between the upright side surface of the seat groove and the seat bottom surface is formed of a curved surface having a radius of curvature in the range of 0.1 to 0.3 mm.

The present invention relates to a throw-away insert for directly brazing a single hard sintered body to a tool base material,
When the present invention is applied to a throw-away chip using an active brazing filler metal having the following composition (a) to (b), the effect of the present invention appears more remarkably.

(A) A brazing material containing 0.5 to 65% by weight of one or two of Ti and Zr, the balance being Cu and unavoidable impurities. (B) 20-30% by weight of Ti and 20-30% by weight of Z
A brazing filler metal containing r and the balance consisting of Cu and unavoidable impurities. (C) containing Ti and Zr at the same ratio as (a) and (b),
In addition, a brazing material further containing 10 to 30% by weight of Ni, with the balance being Cu and unavoidable impurities. (D) Any one or two of Ti and Zr are used in a range of 0.5 to 2;
0% by weight, 10 to 40% by weight of Cu, the balance being Ag
And brazing filler metal consisting of inevitable impurities.

[0013]

Function: As shown in FIG.
Is an economically advantageous method because it is not necessary to polish and remove the edge of the hard-to-work hard sintered body. However, as described above, stress concentration due to a sudden increase in the thickness of the joining brazing layer is achieved. To promote cracking and cracking of the hard sintered body.

On the other hand, in the indexable insert of the present invention, since the intersection angle between the upright side surface and the seat bottom of the seat groove is smaller than the intersection angle between the back surface and the bottom surface of the hard sintered body, the recess is formed in the corner of the seat groove. Even if it is not provided, the portion for avoiding interference of the edge of the hard sintered body can be formed at that portion.

Further, since the thickness of the joining brazing layer gradually increases toward the corner portion of the seat groove due to the difference in the crossing angle, local stress concentration does not occur, and the hard sintered body obtained by brazing cannot be used. Cracks and cracks are less likely to occur.

Here, it is easy to manufacture the hard sintered body in which the bottom surface and the back surface cross at a right angle (the edge angle at the lower surface of the back surface is 90 °). If the crossing angle exceeds 87 °, the effect of forming stagnation is thin, and the possibility that the hard sintered body is inclined and brazed is undesirably increased. On the other hand, when the crossing angle is 75 ° or less, the thickness of the joining brazing layer at the lower back edge of the hard sintered body becomes excessively large, and depending on brazing conditions, the effect of preventing cracks and cracks becomes insufficient. Therefore, it is desirable to limit the crossing angle to a range of 75 ° to 87 °.

Further, when the connecting portion between the upright side surface and the seat bottom is curved, stress concentration on the seat groove corner due to cutting resistance can be avoided. In this case, if the radius of curvature of the curved surface is 0.3 mm or more, the effect of the above-described sneaking is weakened.
If it is less than m, the effect of setting the curved surface may not be sufficiently brought out, so that it is preferable to set it in the range of 0.1 mm to 0.3 mm.

Next, the reason why the effect of the present invention is particularly remarkable when a single hard sintered body is directly joined to a seat groove or when an active brazing material having a specific composition is used will be described.

Since a general brazing material consisting mainly of Ag or Cu hardly adheres to a hard sintered body in an air atmosphere, when such a brazing material is used, as shown in FIG. In this method, the support layer 6 is integrated in advance and the support layer 6 is joined to the tool base material 2 by using an active brazing material or brazing under a special atmosphere. (B)
As described above, a single hard sintered body 1 is directly joined to a tool base material 2. In this case, since the edge of the hard sintered body 1 is placed at a portion where the thickness of the joining brazing layer 7 is sharply increased by the concave sunk portion 5, a crack or a crack is easily generated at the edge.

On the other hand, in the structure of the present invention, even if the edge of the hard sintered body is placed near the corner of the seat groove, stress concentration does not occur, so that cracks and cracks hardly occur.

Further, in order to increase the bonding strength with the hard sintered body, an active brazing material having an improved wettability with the hard sintered body by adding an active metal such as Ti or Zr may be used. In this case, the stress due to the difference in thermal expansion applied to the hard sintered body increases due to the increase in the joining strength. Above all, the melting point drop due to the ternary eutectic of Ti-Zr-Cu, which is adopted when the soldering material is required to have heat resistance, and the joining at a lower temperature The brazing filler metal of the composition (b), which is currently the most preferred composition, and the brazing filler metal of the composition (c), which is excellent not only in heat resistance but also in contact resistance, has excellent wettability with the hard sintered body, and the brazing material itself Because of its high rigidity, the joining strength is very high, and a large stress is applied to the hard sintered body during brazing.
Therefore, eliminating stress concentration in such a case is extremely effective for preventing cracks and cracks, and the effect of the present invention becomes more remarkable.

On the other hand, the brazing material having the composition (d) is made of soft Ag.
Therefore, the brazing temperature can be kept low, and the brazing material itself can absorb the strain generated during brazing. However, since this brazing material has a large difference in thermal expansion from the hard sintered body, cracks and cracks occur in the hard sintered body depending on brazing conditions. Therefore, also in this case, eliminating the stress concentration works effectively.

The material of the tool base material is cemented carbide, steel,
Any material such as ceramics having strength enough to withstand cutting is not particularly limited, but a cemented carbide is most suitable in consideration of a difference in thermal expansion from a hard sintered body and material strength.

[0024]

FIG. 3 to FIG. 5 show an embodiment of a throw-away tip according to the present invention.

The exemplary indexable insert 10 is provided with a seat groove 3 in a corner portion of a cemented carbide tool base material 2, and the hard sintered body 1 containing 20% by volume or more of diamond or cBN in the seat groove 3. And brazing. The hard sintered body 1 may be either one having a support layer 6 made of a cemented carbide or the like at the bottom (see FIG. 3) or a single material without the support layer (see FIGS. 4 and 5). The cutting edge 4 is formed by polishing and polishing the ridge portion of the hard sintered body 1 after brazing.

The seat groove 3 provided in the tool base material 2 is composed of an upright side surface 3a and a seat bottom surface 3b. In each of the illustrated throw-away tips 10, since the edge angle of the lower rear surface of the hard sintered body 1 is 90 °, the intersection angle θ between the upright side surface 3a and the seat bottom surface 3b is 90 ° or less (preferably 75 °). ~
87 °).

In the indexable inserts shown in FIGS. 3 and 4, the seat bottom surface 3b is made parallel to the upper surface of the tool base material 2, and the hard sintered body 1 is positioned with respect to the surface 3b during brazing. However, as shown in FIG.
And the hard sintered body 1 can be positioned with reference to the surface 3a.

Each chip has a corner portion of the seat groove 3, that is,
The connection between the upright side surface 3a and the seat bottom surface 3b has a radius of 0.1 mm.
It is composed of a curved surface 3c in a range of up to 0.3 mm.

Incidentally, the throw-away tip of the present invention can take any shape such as a quadrangle or a rhombus in addition to the triangle in plan view shown in FIG.

Hereinafter, more detailed examples will be described.

[0031]

EXAMPLE 1 Seven types of cemented carbide tool base materials were prepared in which the crossing angles between the upright side surfaces and the seat bottom surfaces of the seat grooves provided in the corner portions were variously changed as shown in Table 1, and the respective tool base materials were prepared. A single cBN sintered body (90 ° edge angle at the lower rear surface) containing 55% by volume of cubic boron nitride in a seat groove (the corners are all curved surfaces having a radius of 0.2 mm) is 25% Ti by weight. -25
% × 10% using a brazing material having a composition of
^-4 (torr) in a vacuum atmosphere.

Then, the ridge of the cBN sintered body was polished to provide a cutting edge.

With respect to the seven types of throw-away tips (samples A to G) obtained as described above, the maximum thickness of the joining brazing layer was measured and the presence or absence of abnormality in the hard sintered body was observed.

The results are shown in Table 1.

[0035]

[Table 1]

In Samples F and G, as a result of the joining brazing layer thickness being too thick at the sunk portion, the strain due to the shrinkage of the brazing material may increase and cracks may occur in the cBN sintered body (a plurality of the same). Some of the samples were cracked and some were not), which was less preferred.

In Sample A, the cBN sintered body was not joined to the cBN sintered body because the cBN sintered body was not inclined because the edge angle of the lower surface of the backside of the cBN sintered body was equal to the corner angle of the seat groove. , The product was not as designed.

On the other hand, Samples B to E had no inclination and cracks of the sintered body, and were products as designed.

[0039]

Example 2 Investigating how the cross-sectional shape of the connection between the upright side surface and the bottom surface of the seat groove provided in the tool base material affects the joining state of the hard sintered body and the cutting performance of the indexable insert. For this purpose, five types of samples H to L in Table 2 (throw-away tips) were prepared. These samples are made of cemented carbide with the intersection angle between the upright side surface of the seat groove and the seat bottom surface set to 85 °, the connecting portion of both surfaces curved, and the radius of curvature of the curved surface changed as shown in Table 2. A tool base material is prepared, and a cemented carbide support layer is provided on the back side in a seat groove of each tool base material.
The BN sintered body (cBN content 55% by volume, back lower edge angle 90 °) was replaced with a weight ratio of 72% Ag-26% Cu-2%
The joining was performed at 850 ° C. in an argon atmosphere using a brazing material having a Ti composition, and the cutting edge portion was finish-polished.

Table 2 shows the joining conditions of the hard sintered bodies of Samples H to L and the results of confirming the presence or absence of cracks.

[0041]

[Table 2]

In Sample L, the radius of curvature of the curved surface was too large, the effect of forming sneaking at the corner of the seat groove was lost, and the bonded hard sintered body was inclined and could not be finished as designed.

On the other hand, in Samples H to K, there were no mounting defects and no cracks occurred in the hard sintered body.

Next, with respect to the samples HK finished as designed, a cutting performance evaluation test was continuously performed under the following cutting conditions.

[0045] Cutting conditions Workpiece: carburized Irizai (SCM415) workpiece hardness having six longitudinal grooves in the outer periphery: cutting speed in H _RC 62 Workpiece surface portion: 200 meters / minute Depth of cut: 0.8 mm Feeding speed: 0.2 mm / rev Cutting time: 5 minutes As a result, in Sample H, the radius of curvature of the curved surface of the seat groove corner is small, and stress due to cutting resistance concentrates on that portion, and the sample H starts from here. Tool breakage occurred.

On the other hand, in Samples I, J and K, since the curvature radius of the curved surface was appropriate, the above-mentioned stress concentration did not occur, and stable cutting was possible.

Table 3 shows the flank wear of Samples I, J and K after cutting for 5 minutes.

[0048]

[Table 3]

[0049]

As described above, according to the hard sintered body throw-away tip of the present invention, the angle between the seat groove provided in the tool base material and the hard sintered body is increased so that the interference of the hard sintered body is prevented. Because of the avoidance of swelling, stress concentration does not occur during brazing due to rapid increase of the joining brazing layer, and cracking and cracking of the hard sintered body can be prevented without reducing the joining strength, and reliability of cutting process The improvement of the performance and the life of the chip can be achieved.

[Brief description of the drawings]

FIG. 1A is a side view showing an example of a conventional throw-away tip. FIG. 1B is a view showing cracks and cracks generated in a hard sintered body of the tip.

FIG. 2A is a side view showing another example of a conventional throw-away chip. FIG. 2B is a view showing cracks and cracks generated in a hard sintered body of the same chip.

FIG. 3A is a plan view showing an embodiment of a throw-away tip according to the present invention. FIG. 3B is an enlarged cross-sectional view taken along the line XX in FIG.

FIG. 4 is an enlarged sectional view of a main part of another embodiment.

FIG. 5 is an enlarged sectional view of a main part of still another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hard sintered body 2 Tool base material 3 Seat groove 3a Standing side surface 3b Seat bottom surface 3c Curved surface 4 Cutting edge 5 Recessed concave portion 6 Support layer 7 Joining brazing layer 10 Throw away tip C Crack, crack θ Crossing angle

Continued on the front page (72) Inventor Tetsuo Nakai 1-1-1 Kunyokita, Itami-shi F-term in Sumitomo Electric Industries, Ltd. Itami Works 3C046 GG01

Claims (9)

[Claims] 1. A hard sintered body containing diamond or cubic boron nitride is brazed to a seat groove formed in a corner portion of a tool base material, and a ridge portion of the hard sintered body is cut with a cutting edge. In the indexable insert to be formed, the intersection angle between the upright side surface and the seat bottom surface of the seat groove of the tool base material is smaller than the intersection angle of the bottom surface and the back surface of the hard sintered body joined to those surfaces. A hard sintered body throwaway tip. 2. The insert according to claim 1, wherein the intersection angle between the upright side surface and the seat bottom surface of the seat groove is set in a range of 75 ° to 87 °. 3. The hard sintered body according to claim 1, wherein a connecting portion between the upright side surface of the seat groove and the seat bottom surface is a curved surface having a radius of curvature in a range of 0.1 to 0.3 mm. Indexable tip. 4. The hard sintered body according to claim 1, wherein the hard sintered body is a single sintered body without a support layer, and the hard sintered body is directly brazed to a tool base material. A hard sintered body throwaway tip. 5. The hard sintered body is joined to a tool base material by a brazing material containing 0.5 to 65% by weight of one or two of Ti and Zr and the balance being Cu and unavoidable impurities. The indexable insert of a hard sintered body according to any one of claims 1 to 4. 6. The hard sintered body is joined to the tool base material with a brazing material containing 20 to 30% by weight of Ti and 20 to 30% by weight of Zr, the balance being Cu and unavoidable impurities. 5. The indexable insert for a hard sintered body according to any one of items 1 to 4. 7. In addition to Ti and Zr according to claim 5 or 6,
The hard sintered body according to any one of claims 1 to 4, wherein the hard sintered body is further joined to the tool base material by a brazing material comprising 0 to 30% by weight of Ni and the balance being Cu and unavoidable impurities. Indexable tip. 8. A composition containing 0.5 to 20% by weight of one or two of Ti and Zr and 10 to 40% by weight of Cu,
The hard sintered body throw-away tip according to any one of claims 1 to 4, wherein the hard sintered body is joined to the tool base material by a brazing filler metal including Ag and unavoidable impurities. 9. The indexable insert according to claim 1, wherein the tool base material is made of a cemented carbide.