JP3317124B2 - Cermet cutting tool with excellent fracture resistance and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cermet cutting tool excellent in fracture resistance and having at least a flank surface on a flank, and a method for producing the same.

[0002]

2. Description of the Related Art Recently, a binder phase containing one or two of Co and Ni as main components: 5 to 25% by weight,
It is widely known that a cutting tool made of a TiCN-based cermet is used, the remainder being mainly composed of a carbonitride of Ti and a hard dispersed phase containing a double carbonitride of Ti and W.

[0003] These cutting tools made of TiCN-based cermet can be sintered by a method of sintering in a vacuum atmosphere disclosed in Japanese Patent Application Laid-Open No. 4-2173 or a liquid nitrogen temperature above the liquid phase temperature disclosed in Japanese Patent Application Laid-Open No. 2-93036. It is manufactured by a method in which a gas is introduced, and after reaching a specified temperature, the vacuum is returned again and sintering is performed.

When a cutting tool made of a TiCN-based cermet is manufactured by these conventional methods, a denitrification phenomenon occurs during sintering, and at the same time, movement of Ti, W, etc. between the vicinity of the surface and the inside thereof occurs. The vicinity is Ti and N compared to the inside.
It is also known that the content of Ti and N on the surface is minimized and the content of W is maximized due to lack of carbon and enrichment of W.

[0005]

SUMMARY OF THE INVENTION An iron-based material is cut using a TiCN-based cermet cutting tool having a burnt surface with the minimum N and Ti contents and the highest W content on the conventional surface. When cutting, the burnt surface with a low content of N and Ti, which have low affinity for iron, and a high content of W, which has high affinity for iron, causes a welding phenomenon with the work material during cutting. This phenomenon is particularly likely to occur on the flank of the cutting tool. If a welding phenomenon occurs with the work material at the cutting edge of the cutting tool during cutting, the welded material repeatedly forms and falls off. With the cutting tool made of TiCN-based cermet, the fracture resistance was insufficient.

[0006]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of studying to obtain a TiCN-based cermet cutting tool having higher fracture resistance than conventional, N, Ti and W
Is generated in a vacuum atmosphere while maintaining a predetermined temperature at the time of sintering. First, the inside of the sintering furnace is heated while being kept at a vacuum of 10 ^-1 Torr or less, at 1200 to 1350 ° C.
1 to 60 Torr when heated to a predetermined temperature within the range
r nitrogen gas is introduced and further heated to 1400-15
Immediately after reaching the predetermined temperature in the range of 50 ° C,
The pressure is returned to a vacuum of 0 ^-1 Torr or less, and subsequently, the pressure in the sintering furnace is maintained at a vacuum atmosphere of 10 ^-1 Torr or less.
After maintaining at a predetermined temperature within the range of 0 to 1550 ° C., when nitrogen gas of 1 to 20 Torr is introduced again, movement and re-movement of N, Ti, W, etc. occur between the vicinity of the surface and the inside, and as a result, N and Ti are enriched in the vicinity of the surface compared to the inside and W is insufficient.
Has a minimum value, and the content of W has a concentration gradient such that it has a maximum value, thereby obtaining a cermet cutting tool having excellent fracture resistance.

The present invention has been made on the basis of the above research results, and (1) a binder phase containing one or two of Co and Ni as a main component: containing 5 to 25% by weight. A cermet cutting tool comprising a hard dispersed phase containing carbides, nitrides and carbonitrides of Ti, and double carbonitrides of Ti and W, and having at least a flank surface on a flank;
The minimum value of the nitrogen concentration distribution when performing composition analysis from the surface of the baked skin surface to the inside is 1 to 100 μm from the surface.
m, and the nitrogen concentration on the surface of the baked surface is in the range of 1.1 to 5.0 times the minimum value, and the composition analysis is performed from the surface of the baked surface to the inside. The minimum value of the Ti concentration distribution is within a range of 1 to 100 μm from the surface, and the Ti concentration on the surface of the baked surface is the minimum value of 1.2 to
1.5 times, the maximum value of the W concentration distribution when the composition analysis is performed from the surface to the inside of the burnt surface is within a range of 1 to 100 μm from the surface, and the burnt surface is A cermet-made cutting tool excellent in fracture resistance having a surface W concentration in the range of 0.5 to 0.9 times the maximum value; (2) one or two of Co powder and Ni powder
Species: 5 to 25% by weight is blended, and the balance is one or two of carbides, nitrides and carbonitride powders of Ti, WC powders, and carbides of Mo, V, Nb, Ta, Zr, and Cr. One or two or more of the powders are blended, and the mixed powder obtained by mixing is press-molded to produce a compact, and the compact is placed in a sintering furnace and sintered to produce a cermet. In the method for manufacturing a cutting tool, the sintering is performed in a sintering furnace at 10 ^-1 T.
heating while maintaining the vacuum at or
When heated to a predetermined temperature within the range of 350 ° C., 1 to 6
0 Torr of nitrogen gas was introduced and further heated to 140
Immediately after reaching a predetermined temperature within the range of 0 to 1550 ° C., the inside of the sintering furnace is returned to a vacuum of 10 ⁻¹ Torr or less, and subsequently, the inside of the sintering furnace is maintained at a vacuum atmosphere of 10 ⁻¹ Torr or less, 1400 to 1550. after holding at a predetermined temperature in the range of ° C., again held by introduction of nitrogen gas 1～20Torr, then cooled at the same time as the start of the sintering furnace atmosphere 10 ^-1
A method for manufacturing a cermet cutting tool that returns to a vacuum of Torr or less.

In order to make it easier to understand the difference between the cermet cutting tool of the present invention and the conventional cermet cutting tool, the typical N concentration of the surface layer of the burnt surface of the cermet cutting tool of the present invention is as follows. FIG. 1 shows the Ti concentration, the W concentration, the distribution of these concentrations, and the N concentration, the Ti concentration, the W concentration, and the distribution of these concentrations in the surface layer of a typical burnt surface of a conventional cermet cutting tool. From FIG. 1, there is a minimum value and a maximum value in the N concentration, the Ti concentration, the W concentration, and the concentration distribution of the surface layer portion of the typical burnt surface of the cermet cutting tool of the present invention. There is no minimum value or maximum value in the N concentration, Ti concentration, W concentration and these concentration distributions of the surface layer portion of the typical burnt surface of the tool. In this respect, the cermet cutting tool of the present invention and the conventional cermet It turns out that it is greatly different from a cutting tool.

Next, the binding phase of the cermet cutting tool of the present invention, the N concentration, the Ti concentration, the W concentration of the surface of the burnt surface and the concentration distribution thereof, and the limitations on the manufacturing conditions of the cermet cutting tool of the present invention. Explain why. A, Reasons for limiting cermet cutting tools (a) Binder phase The binder phase of the baked surface mainly containing one or two of Co and Ni has a fracture resistance when its content is less than 5% by weight. In contrast, if it exceeds 25% by weight, the wear resistance is insufficient.

(B) N Concentration In the cermet cutting tool of the present invention, the minimum value of the N concentration distribution when the composition analysis is performed from the surface of the burnt surface to the inside thereof is within a range of 1 to 100 μm from the surface. It is preferable that the N concentration on the surface is 1.1 to 5.0 times the minimum value. If the minimum value of the N concentration distribution is less than 1 μm from the surface, the welding phenomenon is not improved, while if it is deeper than 100 μm, the hardness of the surface is insufficient and the desired wear resistance cannot be obtained. It is. The minimum value of the N concentration distribution is within a range of 10 to 50 μm from the surface,
Further, the N concentration at the surface is more preferably in the range of 1.5 to 3 times the minimum value.

(C) Ti Concentration In the cermet cutting tool of the present invention, the minimum value of the Ti concentration distribution when the composition analysis is performed from the surface of the burnt surface to the inside thereof is within a range of 1 to 100 μm from the surface. In addition, it is preferable that the Ti concentration on the surface is in the range of 1.1 to 2.0 times the minimum value. If the minimum value of the Ti concentration distribution is less than 1 μm from the surface, the welding phenomenon is not improved, while if it is deeper than 100 μm, the hardness of the surface is insufficient and the desired wear resistance cannot be obtained. It is. T
The minimum value of the i concentration distribution is within the range of 10 to 50 μm from the surface, and the Ti concentration on the surface is the minimum value of 1.2 to 1.
More preferably, it is in the range of 5 times.

(D) W concentration In the cermet cutting tool of the present invention, the maximum value of the W concentration distribution when the composition is analyzed from the surface of the burnt surface to the inside thereof is within a range of 1 to 100 μm from the surface. In addition, it is preferable that the W concentration on the surface is in the range of 0.5 to 0.9 times the maximum value. When the maximum value of the W concentration distribution is less than 1 μm from the surface, the welding phenomenon is not improved.
If it is deeper than 100 μm, the surface hardness will be insufficient,
This is because desired abrasion resistance cannot be obtained. More preferably, the maximum value of the W concentration distribution is in the range of 10 to 50 μm from the surface, and the W concentration on the surface is in the range of 0.6 to 0.8 times the maximum value.

B, Reasons for Limiting the Method of Manufacturing a Cermet Cutting Tool The method of manufacturing a cermet cutting tool of the present invention is characterized in that one or two of Co powder and Ni powder: 5 to 25% by weight are blended. The balance is one or two of carbide, nitride and carbonitride powders of Ti, WC powder, and Mo,
One or two or more of carbide powders of V, Nb, Ta, Zr, and Cr are blended, and a mixed powder obtained by mixing is press-molded to produce a compact, and this compact is sintered. The method for manufacturing a cermet cutting tool of the present invention is the same as the conventional method until the compact is manufactured, but the sintering conditions for sintering the compact are the conventional methods. The reason for limiting the difference is described below.

(E) Degree of vacuum The reason for heating while maintaining the inside of the sintering furnace at a vacuum of 10 ^-1 Torr or less at the time of raising the temperature during sintering is that the degree of vacuum in the sintering furnace is 1
If the pressure exceeds 0 ^-1 Torr, the degassing of the impurity component of the molded product becomes insufficient, which is not preferable.
The degree of vacuum in the sintering furnace after reaching a predetermined temperature in the range of 0 to 1550 ° C. and the degree of vacuum in the sintering furnace during cooling are set to 10 ⁻¹ Torr.
The reason for the lower limit of r is that when the pressure exceeds 10 ^-1 Torr, a soft layer is formed on the surface and the abrasion resistance becomes insufficient. The more preferable range of the degree of vacuum is 5 × 10 ⁻² Torr or less.

(F) Nitrogen gas introduction condition at the time of temperature rise When heating to a predetermined temperature within the range of 1200 to 1350 ° C. at the time of temperature rise, the nitrogen gas of 1 to 60 Torr is introduced at this time. When introduced at less than 1 Torr, internal pores are formed due to denitrification and the fracture resistance is insufficient, which is not preferable. On the other hand, when nitrogen gas is introduced at more than 60 Torr, the surface is severely nitrided, resulting in poor wear resistance. This is because it is not desirable because it is insufficient. The reason why the nitrogen gas is introduced at a predetermined temperature within the range of 1200 to 1350 ° C. at the time of raising the temperature is less than 1200 ° C., because the degassing of the impurity component of the molded body is insufficient. If it exceeds, internal pores are generated due to denitrification, which is not preferable. More preferable conditions for introducing nitrogen gas at the time of temperature rise are as follows.
When heating to a predetermined temperature within the range of 250 to 1300 ° C., 10 to 30 Torr of nitrogen gas is introduced.

(G) Heating holding temperature and nitrogen gas re-introduction condition The inside of the sintering furnace is returned to a vacuum of 10 ^-1 Torr or less by maintaining the temperature at a predetermined temperature in the range of 1400 to 1550 ° C. Is maintained at a predetermined temperature in the range of 1400 to 1550 ° C. while maintaining a vacuum atmosphere of 10 ⁻¹ Torr or less, and then nitrogen gas at ^{1 to 20} Torr is again introduced and maintained. This is not preferable because the residual hardening is insufficient because of the lack of fracture resistance. On the other hand, when the temperature exceeds 1550 ° C., the hard phase grows violently and the fracture resistance is insufficient. 1400-15
The reason why the nitrogen gas of 1 to 20 Torr is introduced again at 50 ° C. is that even if the nitrogen gas is introduced at a pressure of less than 1 Torr, the surface cannot be sufficiently nitrided and the welding phenomenon is not improved. If the nitrogen gas is introduced in excess of 20 Torr, the surface is severely nitrided and the wear resistance is insufficient, which is not preferable. The more preferable range of the nitrogen gas introduction condition at the time of holding the heating temperature is 1450 to 150
Introducing nitrogen gas at 5 to 15 Torr at a temperature in the range of 0 ° C.

[0017]

Next, the present invention will be specifically described based on embodiments. As raw material powder, average particle size:
1.4 μm TiCN (TiC / TiN = 50/50)
Powder, average particle size: 1.5 μm TiC powder, average particle size:
1.0 μm TiN powder, average particle size: 1.0 μm WC
Powder, Mo ₂ C powder with an average particle size of 1.5 μm, VC powder with an average particle size of 2.0 μm, N with an average particle size of 1.3 μm
bC powder, TaC powder having an average particle diameter of 1.2 μm, ZrC powder having an average particle diameter of 1.5 μm, Cr ₃ C ₂ powder having an average particle diameter of 2.0 μm, Co powder having an average particle diameter of 1.2 μm, In addition, Ni powder having an average particle diameter of 1.0 μm was prepared, and these raw material powders were blended so as to have a blending composition shown in Table 1, wet-mixed in a ball mill for 72 hours, dried, and then 1.5 ton. / Cm ^{2 at} a pressure of CNMG12040
The green compacts A to F were prepared by press-forming into eight shapes.

[0018]

[Table 1]

Example 1 The green compacts A to F shown in Table 1 were charged into a sintering furnace,
Heating was performed under the sintering conditions of the pattern shown in FIG. In FIG. 2, a is the nitrogen introduction temperature during heating, b is the sintering temperature, x
Represents the nitrogen gas partial pressure at the time of temperature rise, and y represents the nitrogen gas partial pressure when the nitrogen gas is introduced again after heating and holding at the sintering temperature for a predetermined time, and specific values of a, b, x and y in FIG. The target values are shown in Table 2.

[0020]

[Table 2]

The green compacts A to F shown in Table 1 were sintered under the conditions shown in FIG.
After manufacturing cutting tools (hereinafter, referred to as the present invention cutting tools) 1 to 6 of the present invention having a shape of 0408 (non-polishing graded throwaway tip), a vertical section of a flank of the cutting tools 1 to 6 of the present invention is produced. 2μm inside from baked skin
(The density at this point is defined as the outermost surface density), 5 μm,
(Hereinafter, every 5 μm),..., Up to 200 μm
Quantitative analysis of analysis area: 2 μm × 200 μm was performed by PMA, and the extreme depth of the gradient of N, Ti and W concentrations, and the outermost surface concentration / minimum concentration value of N and Ti, and W
, The outermost surface concentration / maximum concentration value was calculated, and the results are shown in Table 3. For N and Ti, NK is used.
Analysis was performed by applying a waveform separation method to the X-ray spectrum in which α and TiLl were superimposed.

Conventional Example 1 On the other hand, for comparison, the green compacts A to F shown in Table 1 were charged into a sintering furnace, and the inside of the sintering furnace was maintained in a vacuum atmosphere shown in Table 2 while keeping the vacuum atmosphere. After sintering at the temperature shown in Table 2 according to the temperature pattern shown in Table 2, the sintering furnace was turned off, and the furnace was cooled as it was. Cutting tools (hereinafter, referred to as conventional cutting tools) 1 to 6 were manufactured, and the obtained conventional cutting tools 1 to 6 were subjected to quantitative analysis of an analysis area: 2 μm × 200 μm by EPMA in the same manner as in Example 1, and N, Gradient extreme depth of Ti and W concentration,
For N and Ti, the outermost surface concentration / minimum concentration value and for W, the outermost surface concentration / maximum concentration value are calculated,
Table 4 shows the results.

Next, regarding the cutting tools 1 to 6 of the present invention and the conventional cutting tools 1 to 6, a work material: SCM439, a cutting speed: 220 m / min. Feed: 0.3 mm / rev. , Depth of cut: 2.5 mm, 1 pass: cutting for 6 seconds, pause for 6 seconds, an interval cutting test of 50 passes and 100 passes was performed, the flank wear of the cutting edge was measured, and the results are shown in Table 3. The results are shown in Table 4 and Table 4, and the chipping resistance due to welding chipping was evaluated.

[0024]

[Table 3]

[0025]

[Table 4]

From the results shown in Tables 3 and 4, the cutting tools 1 to 6 of the present invention can improve the chipping resistance without impairing the wear resistance as compared with the conventional cutting tools 1 to 6. It can be seen that even with cermet cutting tools having the same component composition, the life of the cermet cutting tool is greatly improved due to the difference in the burnt surface.

[0027]

As described above, the cutting tool made of cermet according to the present invention can greatly improve the tool life as compared with the conventional one, and has excellent industrial effects.

[Brief description of the drawings]

FIG. 1 is a graph schematically showing N concentration, Ti concentration, W concentration and distribution of these concentrations in the surface layer of a burnt surface of a cermet cutting tool of the present invention and a conventional cermet cutting tool.

FIG. 2 is a pattern diagram showing the sintering temperature and atmosphere conditions of the cermet cutting tool of the present invention.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsuhisa Nonaka 1511 Komagi, Ishishita-cho, Yuki-gun, Ibaraki Prefecture Inside the Tsukuba Works, Mitsubishi Materials Corporation (72) Inventor Seiichiro Nakamura 1511 Furimagi, Ishishita-cho, Yuki-gun, Ibaraki Prefecture Mitsubishi Materials Corporation Tsukuba Works (72) Inventor Hisashi Tsujizaki 1511 Furamaki, Ishishita-cho, Yuki-gun, Ibaraki Prefecture Mitsubishi Materials Corporation Tsukuba Works (56) References JP-A-5-221725 58) Field surveyed (Int. Cl. ⁷ , DB name) B23P 15/28 B23B 27/14 C22C 29/02

Claims (1)

(57) [Claims] 1. One or two of Co powder and Ni powder: 5 to 25% by weight, and the balance is one or two of Ti carbide, nitride and carbonitride powder,
WC powder, and one or more of carbide powders of Mo, V, Nb, Ta, Zr, and Cr are blended, and a mixed powder obtained by mixing is press-molded to form a molded body;
In the method of manufacturing a cermet cutting tool for sintering the formed body, the sintering is performed while heating the atmosphere in the sintering furnace while maintaining the atmosphere in a sintering furnace at a vacuum of 10 ^-1 Torr or less. When heated to a predetermined temperature, nitrogen gas at 1 to 60 Torr is introduced, and further heated to 1400 to 1550.
Immediately after reaching a predetermined temperature within the range of ° C., the atmosphere in the sintering furnace is returned to a vacuum of 10 ^-1 Torr or less, and subsequently, the atmosphere in the sintering furnace is maintained at a vacuum atmosphere of 10 ^-1 Torr or less.
After maintaining at a predetermined temperature in the range of 400 to 1550 ° C,
Nitrogen gas of ^{1 to 20} Torr is again introduced and maintained, and then, at the same time as cooling is started, the atmosphere in the sintering furnace is changed to 10 ^-1 Torr.
A method for manufacturing a cermet cutting tool, comprising returning the vacuum to the following: