JP3236899B2 - Manufacturing method of surface coated tungsten carbide based cemented carbide cutting tool with excellent wear and fracture resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a surface-coated tungsten carbide (hereinafter abbreviated as WC) base material which exhibits excellent wear resistance in continuous cutting of steel and exhibits excellent fracture resistance in interrupted cutting. The present invention relates to a method for manufacturing a hard alloy cutting tool.

[0002]

2. Description of the Related Art Conventionally, a surface of a WC-based cemented carbide substrate is generally coated with, for example, Ti carbide, nitride, carbonitride, carbonate, and carbonitride, and aluminum oxide (hereinafter, TiC, TiN, respectively). , TiCN, TiCO, and TiCNO, as well as in Al ₂ O ₃₎ with an average layer thickness of 5~20μm by chemical vapor deposition one single layer or a hard layer made of a multi layer of two or more types of such It is well known that a surface-coated WC-based cemented carbide cutting tool formed by vapor deposition is used for continuous cutting of steel and the like.

Further, regarding the hard coating layer constituting the above-mentioned conventional surface-coated WC-based hard metal cutting tool, when the hard coating layer is cooled from the reaction atmosphere temperature during the formation of the hard coating layer by using the chemical vapor deposition method, the WC-based Since the shrinkage ratio of the WC-based cemented carbide substrate is smaller than that of the hard coating layer formed on the surface of the hard alloy substrate, a tensile stress is present in the hard coating layer. Is, for example, published in 1986,
10 to 50 kg / mm ² (98 to 490 MPa) as described in “Journal of the Japan Institute of Metals”, Vol. 30, No. 3
It is also known to be of the order.

[0004]

On the other hand, in recent years, labor saving and FA have been remarkable in cutting work, and along with this, cutting tools tend to be strongly required to be versatile. For cutting tools made of WC-based cemented carbide,
For example, when this is used for intermittent cutting of steel, the cutting edge is liable to be broken, and at present, it cannot be put to practical use.

[0005]

Means for Solving the Problems Accordingly, the present inventors have
In view of the above, the surface coating W having excellent fracture resistance
In order to manufacture a cutting tool made of C-base cemented carbide, a research was conducted with particular attention to the cutting tool made of the conventional surface-coated WC-based cemented carbide. The hard coating layer formed by the chemical vapor deposition method constituting 10 to 50 kg / mm ² (98
~ 490MPa) The hard coating layer at the rake face of the cutting edge is subjected to, for example, shot blasting using a steel ball to substantially remove the tensile stress of the hard coating layer. If the hard coating layer on the rake face is made substantially free of tensile stress, the resulting surface-coated WC-based cemented carbide cutting tool exhibits excellent fracture resistance in interrupted cutting, and further has a continuous The research results show that even when cutting, it shows even better wear resistance.

The present invention has been made on the basis of the above research results, and (a) formation of a WC-based cemented carbide substrate by a chemical vapor deposition method so that a tensile stress necessarily exists. (B) Then, only the rake face portion of the cutting edge after the formation of the hard coating layer is subjected to shot blast treatment to substantially reduce the tensile stress of the hard coating layer at the rake face portion. As a result, the hard coating layer on the flank of the cutting edge substantially has tensile stress during the formation of the hard coating layer, and the hard coating layer on the rake face of the cutting edge has a tensile stress. Coating WC with excellent abrasion resistance and fracture resistance substantially free of
The present invention is characterized by a method of manufacturing a base cemented carbide cutting tool.

[0007]

Next, a method for producing a surface-coated WC-based cemented carbide cutting tool according to the present invention will be described in detail with reference to examples.
WC powder having an average particle size of 3 μm as a raw material powder,
1.5 μm (Ti, W) C powder [TiC / WC = 30/70 at weight ratio (same as mass ratio), 1.2 μm
(Ti, W) CN powder (TiC / TiN / WC = 24/20/56 by weight ratio (same as mass ratio))
(Ta, Nb) C powder (TaC / NbC = 90/10 by weight ratio (same as mass ratio)), and 1.2 μm
Are prepared, and these raw material powders are blended in the composition shown in Table 1, and wet-mixed for 72 hours by a ball mill.
After drying, it is pressed into a green compact, and then this green compact is vacuum-sintered in a vacuum of 1 × 10 ^-2 torr (1.33 Pa) at a temperature of 1450 ° C. for one hour, All have the shape of ISO / CNMG120408.
C-based cemented carbide substrates A to C and a WC-based cemented carbide base D having a Co-enriched surface portion (maximum Co content: 13%, thickness: 20 μm) were produced, respectively. Further, the WC-based cemented carbide substrate C was added with 100 torr (1
3.3 KPa) in a methane gas atmosphere, temperature: 1400
Carburizing at a temperature of 1 ° C. for 1 hour, the surface has a maximum Co content of 17% by weight and a thickness of 40 μm.
m Co-enriched surface layer was formed.

Next, these WC-based cemented carbide substrates A to
The conventional surface-coated WC-based cemented carbide cutting by a conventional method comprising forming a hard coating layer having the composition and the average layer thickness shown in Table 2 under normal conditions using a normal chemical vapor deposition apparatus on the surface of D. Tools (hereinafter referred to as cutting tools made of conventionally coated cemented carbide) 1 to 8 were manufactured, respectively.

Further, a steel ball having an average diameter of 0.3 mmφ is used as a shot on the rake face of the cutting edge of the conventional coated cemented carbide cutting tool 2 manufactured by the above-mentioned conventional method. 50-90 m / sec, projection time: 50-2
The method of the present invention was carried out by performing shot blasting under the conditions of 00 seconds, and the flank of the cutting edge had a tensile stress shown in Table 3, and the rake face had substantially no residual stress. A cutting tool made of a surface-coated WC-based cemented carbide of the present invention (hereinafter, referred to as a cutting tool made of a coated cemented carbide of the present invention) was manufactured.

[0010] For the purpose of comparison, shot blasting is performed on the cutting rake face and / or flank face of the conventional coated cemented carbide cutting tools 1 to 8 also manufactured by the above-mentioned conventional method under the same conditions. WC-based cemented carbide cutting tools (hereinafter referred to as comparative-coated cemented carbide cutting tools) having the residual stress shown in Table 3 on the rake face and flank of the cutting edge. ) 1
8 were each produced. Therefore, the composition and the average layer thickness of each hard coating layer of the coated cemented carbide cutting tool manufactured by the method of the present invention and the comparative method correspond to those of the conventionally coated cemented carbide cutting tools 1 to 8, respectively. Will be the same.

In the comparative coated cemented carbide cutting tools 1 to 8 manufactured by the comparative method, the residual stress distribution of the hard coating layer at the rake face and / or flank of the cutting edge is out of the range of the present invention. It is a thing. Table 3 also shows the measurement results of the residual stress of the hard coating layer at the rake face and flank of the cutting edge of the conventional coated cemented carbide cutting tools 1 to 8 by the X-ray diffraction method.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015] Next, the resulting various coated cemented carbide cutting tool, work material: SCM440 (hardness: H _B 220) round bar, Cutting speed:. 220 m / min, Feed: 0 . .25mm / rev, cut: 1.5 mm cutting time: dry continuous cutting test of steel in 30 minutes, conditions as well as work material: SNCM439 (hardness: H _B 260) square bar of cutting speed: 100 m / min., Feed: 0.3 mm / rev., Depth of cut: 1.5 mm, a dry intermittent cutting test of steel was performed. In the continuous cutting test, the wear width of the flank of the cutting edge was measured. In the intermittent cutting test, the cutting time until the cutting edge was broken was measured. Table 3 shows the results of these measurements.

[0016]

From the results shown in Table 3, the cutting tool made of the coated cemented carbide of the present invention manufactured by the method of the present invention can be used in continuous cutting in comparison with the conventional cutting tools 1-8 of coated cemented carbide. In the case of intermittent cutting, conventional coated cemented carbide cutting tools 1 to 8 show chipping defects in a very short cutting time, and cannot be put to practical use. In contrast, it is clear that they exhibit excellent cutting performance over a long period of time and show excellent fracture resistance, and as shown in the comparative coated cemented carbide cutting tools 1 to 8, It is clear that when the residual stress distribution of the hard coating layer in the surface portion and the flank portion is different from that of the method of the present invention, at least one of the characteristics of wear resistance and fracture resistance is inferior.

As described above, according to the method of the present invention,
Surface coating that shows even better wear resistance in continuous cutting, and also shows excellent fracture resistance in interrupted cutting, and exhibits excellent cutting performance for both continuous cutting and interrupted cutting over a long period of time. This makes it possible to manufacture a cutting tool made of a WC-based cemented carbide.

──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Toshikatsu Sudo 1511 Furamaki, Ishishita-cho, Yuki-gun, Ibaraki Pref. Mitsubishi Materials Corporation Tsukuba Works (56) References Hei 2-254144 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23P 15/28 B23B 27/14 C23C 16/30

Claims (1)

(57) [Claims] 1. A tungsten carbide-based cemented carbide substrate having, on a surface thereof, (a) a hard coating layer formed by a chemical vapor deposition method so that a tensile stress necessarily exists, and (b) By subjecting only the rake face portion of the cutting edge after the formation of the hard coating layer to a shot blast treatment to substantially remove the tensile stress of the hard coating layer of the rake face portion, The coating layer substantially has tensile stress during the formation of the hard coating layer, and the hard coating layer on the rake face of the cutting edge has substantially no tensile stress. A method for producing excellent surface-coated tungsten carbide based cemented carbide cutting tools.