JPH0529764Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] This invention relates to an interrupted cutting tool using a high-hardness sintered body containing cubic boron nitride as a cutting blade. [Prior Art] Cubic boron nitride (CBN) is a hard substance second only to diamond, and its sintered body is used in various cutting tools. For example, JP-A-53-
No. 77811 shows an example of this type of CBN sintered body suitable for cutting tools. The high hardness sintered body disclosed in the above publication is CBN
Contains 80 to 40% by volume, with the remainder mainly consisting of carbides, nitrides, borides, silicides, oxides, or mixtures or mutual solid solution compounds of group a, Va, and a transition metals of the periodic table. This compound forms a continuous binder phase in the structure of the sintered body. In such a CBN sintered body, the remaining compound, which is the binder phase, has a relatively high hardness and a high melting point, and therefore,
Generally shows high performance as a cutting tool. Therefore, commercially available products are already available. This commercial product is
It usually contains 50 to 60% by volume of CBN with an average particle diameter of about 3 μm, and is used to form a cutting edge and used as a cutting tool or throw-away tip. These tools are used under conditions where the cutting edge inclination angle φ is zero or negative, the side rake angle θ is negative, or φ is positive and θ is zero or positive. [Problems to be solved by the invention] It has been sufficiently demonstrated that the CBN sintered body having the composition as described above, including commercially available products, generally exhibits high performance when used under the conditions as described above. However, depending on the usage pattern, the following problems still occur. That is, when cutting hardened steel, as shown in FIG. It was often damaged because it was bitten by the target.
In interrupted cutting, the cutting edge once separated from the workpiece receives a strong impact when it bites again, and the impact is extremely large because the workpiece is hardened steel. In addition, the chipping of the cutting edge is concentrated in the contact area of the cutting edge with the work material, that is, in the diagonally shaded area on the rake face 2 surrounded by the three points A, B, and C in Fig. 6, at point A. . Here, the blade angle (β in Figure 7) should be less than 90°,
Furthermore, it is known that when the cutting edge inclination angle φ is made positive, the principal force and back force during cutting are reduced. This method is widely used for cutting with general tools because the cutting edge stress value is reduced by reducing the principal force and thrust force, but it is In interrupted cutting, as mentioned above, a strong impact is applied, so chips still occur. Therefore, this idea was developed for the interrupted cutting of hardened steel.
This is an attempt to solve the problem of chipping of CBN sintered cutting edges from the viewpoint of tool shape. [Means for solving the problem] The inventors of the present invention set the cutting edge angle β to at least 90° in order to maintain the strength of the cutting edge, and searched for a method to avoid stress concentration at point A in Figure 6. As a result, as shown in Fig. 1, the inclination angle φ of the cutting edge 1 is -12°<φ<-3°,
When cutting at a so-called negative or positive angle, where the side rake angle θ is 4° or more (the chain line cutting edge indicates a state where both φ and θ are zero), the impact force applied to the cutting edge is reduced, resulting in a significant reduction in tool life. I found that it can be improved. Here, if the cutting edge inclination angle φ is larger than -3°, the effect of mitigating the impact during intermittent biting will be weak; on the other hand, if φ is -
If it is smaller than 12°, the impact mitigation effect will improve, but on the other hand, the cutting back force during continuous cutting will increase too much, increasing flank wear and crater wear of the cutting edge, and the cutting edge will fall off due to this wear. Furthermore, when the side rake angle θ is less than 4°, stress is concentratedly applied to point A in FIG. 6, shortening the fracture life. Furthermore, when θ+φ exceeds 1°, the lateral rake angle θ becomes relatively large, and the lateral flank 3 (second
(Fig.) hits the workpiece A and becomes impossible to cut. Similarly, the ratio d/R of the nose R of the cutting edge and the depth of cut d is
If it exceeds 0.375, the side flank surface 3 will also come into contact with the workpiece, making cutting impossible. In addition, providing the well-known negative brand 4 shown in FIG. 3 on the nose R portion of the cutting blade 1
In the case of a CBN sintered cutting blade, this is particularly preferable in terms of improving the chipping resistance of the cutting blade. However, that land 4
When the angle α exceeds −10°, the cutting edge approaches so-called solid contact during interrupted cutting, which increases the stress on the cutting edge and makes it more likely to break. Furthermore, if α is less than -35°, the cutting resistance during continuous cutting will increase, making the cutting edge more likely to break as above. Furthermore, by adopting the configuration of this invention, the CBN sintered body exhibits excellent cutting performance even in interrupted cutting of hardened steel, but in order to maximize its effectiveness, it is necessary to sinter the CBN. The body itself,
It is preferable to select one with a CBN content of 55 to 75% by volume. If the content is less than 55% by volume, the strength of the sintered body itself will be insufficient and the cutting edge will easily break. On the other hand, if it exceeds 75% by volume, a portion where CBN particles directly bond to each other will occur, and this portion, which is vulnerable to impact, will cause cracks during interrupted cutting, leading to chipping of the cutting edge. The remaining composition of this CBN sintered body is mainly composed of carbides, nitrides, borides, silicides, or mixtures or mutual solid solution compounds of transition metals from groups a to a of the periodic table mentioned above. It goes without saying that aluminum is desirable, but it is necessary as one of the remaining components to firmly bond these compounds and CBN, and after sintering, AlB ₂ ,
Exists as AlN etc. Furthermore, WC also has a high modulus of elasticity, so it is desirable to include it in the remaining composition in order to increase the strength of the binder. Detailed examples of this invention are listed below. [Example 1] Powder material having the composition shown in Table 1 was heated at a pressure of 55 kb,
Sintering was performed under ultra-high pressure and ultra-high temperature at a temperature of 1400°C to obtain a sintered body. Next, a cutting chip was made from the sintered body, and the chip was fixed to a holder so that the cutting edge inclination angle φ and the side rake angle θ became the values shown in Table 1 during cutting. Then, using this tool, SKD11
A cutting tool was used to cut the outer periphery of a workpiece material that had a U-groove with a width of 20 mm on the outer periphery. The hardness of the work material is H _RC 60. The cutting conditions are: cutting speed 100m/min, depth of cut 0.2mm, feed 0.1
It was a dry method of mm/rev. The nose radius of the chip cutting edge is 0.8R, the angle α of the negative land provided at the nose radius is -25°, and the width of the land (W in Figure 3) is 0.15mm. The results of the cutting test are shown in Figure 4. In the figure, samples Noc, f, g, l, m, and n are all comparative products, and the others are products of the present invention. As can be seen from the results, compared to the comparative product, which lasts up to 10 minutes before breakage, the tool of this invention has a significantly longer usable time.

[Table] * Note: ○ indicates the product of the present invention, × indicates the comparative product [Example 2] CBN content is 60% by volume, average particle size is 1 μm, and the remainder is titanium nitride, titanium boride, aluminum nitride, and tungsten carbide. A chip with nose radius R and negative land angle α shown in Table 2 is made from a CBN sintered body consisting of aluminum boride and unavoidable impurities. A tool was obtained that was fixed to the holder so that the angle was +5°. And with this tool, SCM435, hardness H _RC
A workpiece having the shape shown in Fig. 5 of 60, that is, outer diameter D ₁
= 60 mm, hole diameter D ₂ = -15 mm, and the end face of diameter D ₁ has a diameter
Surface F of work material A' was cut with four holes of D ₃ =7 mm open. Cutting conditions are cutting speed 90m/
min, feed rate 0.1mm/rev, depth of cut listed in Table 2,
It is a dry method. The number of cutting operations until breakage under each condition is shown in the same table. In addition, samples v, x in this Table 2
does not satisfy the conditions of the present invention.

〔effect〕

The cutting tool of this invention described above has a cutting tool angle β of
90° or more, the already high strength of the cutting edge is further strengthened by the installation of a negative brand. is negative,
By adopting a positive angle for the latter, it has the effect of alleviating the stress applied to the cutting edge and the effect of avoiding stress concentration, thus enabling stable interrupted cutting of hardened steel with a CBN sintered body of a well-known composition. It has the effect of
In addition, by setting φ to -12°<φ<-3°, we achieved a shock-reducing effect during intermittent biting while also suppressing flank wear and crater wear, resulting in a longer tool life compared to conventional ones. It grows big. The tool of this invention can also be used for continuous cutting, but in many cases hardened steel is used for interrupted cutting rather than continuous cutting, and from this point of view, the contribution of this invention to industry is extremely high. I can say that.

[Brief explanation of drawings]

Figure 1 is a perspective view showing the tool of this invention in use, Figure 2 is an enlarged plan view of its main parts, Figure 3 is a sectional view taken along the - line in Figure 2, and Figure 4. is a graph showing the effect of Example 1, FIG. 5 is a side view of the workpiece used in Example 2, FIG. 6 is a plan view showing the contact area of the cutting edge with the conventional tool, and FIG. 7 is the conventional tool. It is a diagram showing an example of an interrupted cutting form by. 1...Cutting edge, 2...Rake face, 3...Side flank, 4...Negative brand, R...Nose radius, β...Cutter angle, φ...Cutting blade inclination angle, θ...Side rake Angle, α... Negative brand angle, A,
A'...Work material, F...Machine end surface.

Claims (1)

[Claims for Utility Model Registration] (1) A cutting tool whose cutting edge is made of a high-hardness sintered body containing cubic boron nitride, the cutting tool having a cutting edge angle β of
90° or more, the nose of the cutting blade has a roundness with a radius R, and the cutting blade inclination angle φ and side rake angle θ are φ+θ≦1°, −12°<φ<−3°, θ≧4°
The nose R portion of the cutting edge has a negative radius of -10° to -35°, and the ratio d/R between the R and the depth of cut d during cutting is 0.375.
An interrupted cutting tool using a high-hardness sintered body, which is characterized by the following: (2) The high-hardness sintered body contains cubic boron nitride in a volume ratio of 55 to 75%, and the remainder is carbides and nitrides of group a, Va, and a transition metals of the periodic table.
The high-hardness sintered product according to claim 1 of the utility model registration claim, characterized in that it contains boride, silicide, oxide, or a mixture or mutual solid solution thereof, and aluminum, tungsten carbide, or unavoidable impurities. A tool for interrupted cutting using the body.