JPH11256263A - Cutting tool made of titanium carbonitride series cermet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting tool made of titanium carbonitride series cermet exhibiting excellent cutting performance over a long period. SOLUTION: This cutting tool made of titanium carbonitride sereis cermet has a compsn. in which hard dispersed phases occupy 85 to 97 area% by electronic microscopic structural observation, and the balance bonding phases 1 essentially consisting of Co and/or Ni with inevitable impurities. Then, the hard dispersed phases are composed of (a) the one with a core structure in which the core parts 2a are composed of TiCN or Ti series multiple carbonitrides of Ti and one or more kinds among W, Mo, Ta and Nb [hereinafter shown by (Ti, M') CN], and the surface parts 2b are composed of (Ti, M') CN, but have core structure of concn. gradients in which the concn. of Ti is lower than that in the core parts 2a and the concn. of M' is relatively higher than that therein, and >=30 area% by the ratio occupied in the whole body have a deformed core structure in which the surface parts 2b are uncontinuously distributed, and a part of the core parts 2a is exposed to the bonding phases 1, and the balance core Ti series multiple carbonitrides phases 2 and (b) TiB2 phases 3, and the ratio of the core Ti series multiple carboitride phases 2 is made to 83 to 96 area%, and the ratio of the TiB2 phases 3 is made to 0.5 to 5 area%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent chipping resistance, for example, when cutting steel under heavy cutting conditions such as high depth of cut or high feed, and when performing intermittent cutting, chipping or chipping of the cutting edge. The present invention relates to a titanium carbonitride-based cermet cutting tool (hereinafter, simply referred to as a cermet tool) which exhibits excellent cutting performance for a long period of time without occurrence of the above.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2 which is described in, for example, Japanese Patent Publication No. 56-51201 and which schematically shows the results of structure observation by an electron microscope in a schematic diagram, as shown in FIG. And the balance shows a composition consisting of a binder phase mainly composed of Co and / or Ni and inevitable impurities, and the hard dispersed phase is formed of titanium carbonitride (hereinafter referred to as TiCN) or Ti. Ti-based composite carbonitrides [hereinafter, (Ti, M) CN] with one or more of metals belonging to groups 4a, 5a, and 6a of the periodic table excluding Ti (hereinafter collectively referred to as M) Indicated by
The surface portion 2b is made of (Ti, M) CN,
A fixed form in which a Ti concentration is lower than that of the core portion, and a M concentration has a cored tissue having a relatively high concentration gradient, and the cored structure is such that the surface portion 2b completely surrounds the core portion 2a. There is known a cermet tool composed of a titanium carbonitride-based cermet (hereinafter, simply referred to as a cermet) composed of a cored Ti-based composite carbonitride phase having a cored structure.

[0003]

On the other hand, in recent years, the use of FA and high performance cutting machines has been remarkable, and there has been a strong demand for labor saving and energy saving in the cutting process. There is a tendency for cutting tools that can be used for intermittent cutting and can also perform heavy cutting such as high feed and high depth of cut. When used for cutting under heavy cutting conditions such as cutting, chipping or chipping (small chipping) is likely to occur on the cutting edge due to chipping resistance, and the service life is relatively short in the current situation It is.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoints, the above-mentioned conventional cermet tools were focused on, and research was carried out to improve the fracture resistance thereof. As a result, the sintering of the conventional cermet tools is usually performed by: Heating rate: 1 to 3 ° C / min. (B) Atmosphere of temperature rise from room temperature to 1200 to 1350 ° C:
A vacuum atmosphere of 0.1 torr or less, (c) a sintering temperature of 1200 to 1350 ° C.
Temperature rising atmosphere to 0 to 1560 ° C: 0.5 to 30 torr
(D) Holding time and atmosphere at the above sintering temperature: 60 to 9
0 minutes and a nitrogen atmosphere of 0.5 to 30 torr, (e) Cooling: furnace cooling in a vacuum atmosphere of 0.1 torr or less, which is carried out under the above conditions (a) to (e). The sintering conditions except for the sintering condition (d) among the a) to (e) are the same, but the sintering temperature of the sintering condition (d) is set to a relatively low 1380 to 1460 ° C. Constituting the core 2a and the surface 2b of the hard dispersed phase (Ti,
M) The M component in CN is W, Mo, Ta, and Nb
When sintering is performed under the condition that a titanium boride (hereinafter, referred to as TiB ₂ ) powder that forms a hard dispersed phase alone as a raw material powder is specified as one or more of the above, As shown in FIG. 1, which is a schematic diagram illustrating the results of microstructure observation by an electron microscope, a cermet constituting a cermet tool has a core 2 a exposed to a binding phase 1 as a hard dispersed phase, and a surface 2 b is formed. Cored Ti-based composite carbonitride phase 2 with cored structure of deformed cored structure with discontinuous distribution 2
However, the surface portion 2b alone or the core portion 2a
T with a cored structure of a fixed cored structure completely surrounding the
The cored Ti-based composite carbonitride phase 2 having the cored structure of the deformed cored structure is present in a state coexisting with the i-type composite carbonitride phase, and the pressure and the pressure of the sintering temperature holding atmosphere are changed. /
Or, while controlling the sintering temperature,
If the ratio is not less than 0 area% or the ratio of the total amount, the resulting cermet tool exhibits excellent fracture resistance, and furthermore, the TiB which coexists with these cored Ti-based composite carbonitride phase 2. 0.5 to 2 ratio of ₂ phase 3
By setting the area%, wear resistance can be improved. As a result, chipping or chipping does not occur on the cutting edge even when interrupted cutting is performed under heavy cutting conditions, and excellent wear resistance over a long period of time is obtained. We got the research result that it works.

The present invention has been made based on the results of the above-mentioned research, and it has been found from observation of the structure of an electron microscope that the hard dispersed phase occupies 85 to 97 area%, and the balance is mainly composed of Co and / or Ni. It shows a composition consisting of a binder phase and unavoidable impurities, wherein the hard dispersed phase is (a) a core is TiCN,
Or Ti and one of W, Mo, Ta, and Nb
Or more Ti-based composite carbonitride [hereinafter, (Ti, M ')
CN)], and all the surface portions are (Ti,
M ′) CN, but the Ti concentration is lower than that of the core portion, and the combined concentration of one or more of W, Mo, Ta, and Nb has a relatively high concentration gradient. Have
Further, the cored structure has a deformed cored structure in which the surface portion is discontinuously distributed and a part of the core portion is exposed to the binding phase, and the remaining portion is the surface area. The core has a fixed cored structure completely surrounding the core, or the entire cored structure has a cored Ti-based composite carbonitride phase having the deformed cored structure, (b) a TiB ₂ phase, And the ratio of the cored Ti-based composite carbonitride phase is 83 to 96.
The present invention is characterized by a cermet tool having excellent fracture resistance, comprising a cermet having an area% of 0.5% to 2 area% of the TiB ₂ phase.

The reason why the composition of the cermet constituting the cermet tool of the present invention is limited as described above will be described. (1) Proportion of Hard Dispersed Phase If the proportion is less than 85 area%, the proportion of the binder phase relatively exceeds 20 area% and becomes too large, so that desired excellent wear resistance cannot be secured. On the other hand, if the ratio exceeds 97 area%, the ratio of the binder phase becomes too small, the sinterability is reduced, and the predetermined strength cannot be secured. I decided.

(2) Cored Ti-based composite carbonitride phase The cored Ti-based composite carbonitride phase has high hardness and high toughness,
Thus, the cermet tool has an effect of improving the wear resistance and fracture resistance, but if the ratio is less than 83 area%,
If the desired improvement effect cannot be obtained in the above-mentioned action, and if the ratio exceeds 96 area%, the content ratio of the binder phase relatively decreases and the sinterability decreases, and the predetermined strength is reduced. The ratio can be reduced to 7
It was determined to be 8 to 96 area%. In this case, if the ratio of the deformed cored structure in the cored structure constituting the cored Ti-based composite carbonitride phase is less than 30% by area as a percentage of the entire structure, for example, extremely severe conditions will be obtained as described above. Since the occurrence of chipping and chipping of the cutting edge cannot be suppressed when interrupted cutting of steel is performed under heavy cutting conditions, the ratio is set to 30% by area or more.

(3) TiB ₂ phase The TiB ₂ phase has the effect of improving the wear resistance of the cermet tool. If the proportion is less than 0.5 area%, the desired effect can be obtained. But the ratio is 2
If the area% is exceeded, the excellent fracture resistance provided by the cored Ti-based composite carbonitride phase will be impaired, so the ratio is set to 0.5 to 2 area%.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a cermet construction according to the present invention will be described.
The components will be specifically described with reference to examples. As raw material powder,
Ti having a predetermined average particle size in the range of 0.5 to 2 μm
CN (TiC / TiN = 50/50, weight ratio, hereinafter the same)
E) powder, TiN powder, TiB _TwoPowder, TaC powder, N
bC powder, WC powder, Mo_Two C powder, (Ti, Ta) C
N [However, TiC / TiN / TaC = 50/30/2
0] powder, (Ti, Nb) CN [however, TiC / TiN
/ NbC = 55/25/20] powder, (Ti, Ta, N
b) CN [However, TiC / TiN / TaC / NbC = 3
0/30/10/30] powder, (Ti, Ta, W) CN
[However, TiC / TiN / TaC / WC = 50/20 /
20/10] powder, (Ti, Nb, Mo) CN [provided that
TiC / TiN / NbC / Mo_Two C = 50/30/10
/ 10] powder, (Ti, W, Mo) CN [however, TiC
/ TiN / WC / Mo_Two C = 50/30/10/10]
For powder, Co powder, Ni powder, and graphite (C) powder
In the meantime, these raw material powders were arranged as shown in Tables 1 and 2, respectively.
The mixture was mixed in a wet composition for 24 hours using a ball mill,
After drying, 1 ton / cm^Two Pressing into a predetermined shape with pressure
Then, green compacts A to Q were formed.

Next, the green compacts A to Q were subjected to the following sintering conditions, that is, from room temperature to 1300 ° C. for 0.05 to
rr in a vacuum atmosphere at 2 ° C./min. After the temperature was raised to 1300 ° C., the atmosphere was changed to a nitrogen atmosphere of 10 torr, and the temperature was raised to a predetermined sintering temperature in the range of 1380 to 1460 ° C. at the same temperature raising rate. After the temperature is raised to the sintering temperature, the pressure is adjusted to a predetermined pressure in the range of 0.5 to 30 torr in a nitrogen atmosphere, and then the sintering is performed under the sintering conditions of holding for 60 minutes and subsequently cooling the furnace in the same vacuum atmosphere. By I
Cermet tools 1 to 17 of the present invention each having a throw-away tip shape according to SO standard CNMG120408 were manufactured. Also, for the purpose of comparison, the above compacts A to
Comparative cermet tools 1 to 17 were manufactured by sintering under the same sintering conditions except that Q was set to a predetermined temperature within a relatively high range of 1530 to 1560 ° C.

Next, with respect to the various cermet tools obtained as a result, the surface hardness and the internal hardness were measured by Vickers hardness, and the structure at an arbitrary position in the cross section of the tool was observed with an electron microscope. Was measured using an image analyzer. Also, using an electron beam microanalyzer, when the concentration distribution of the cored Ti-based composite carbonitride phase, which is a hard dispersed phase of the cermet constituting the above various cermet tools, was measured. The surface portion has a lower Ti concentration than the core portion, and the concentration of one or more of W, Mo, Ta, and Nb has a relatively high concentration gradient. It was shown to have. FIG. 1 is a schematic diagram showing the internal structure of the cermet tool 7 of the present invention, and FIG. 2 is a schematic diagram showing the internal structure of the comparative cermet tool 6 by an electron microscope. Then, in order to evaluate the fracture resistance of the various cermet tools described above, a work material: JIS S45C, a longitudinally spaced round bar with four longitudinal grooves, a cutting speed: 250 m / min. Feed: 0.2 mm / rev. Notch: 2.5 mm. Cutting time: 20 minutes, a wet high-cut intermittent cutting test of steel was performed under the following conditions, and the flank wear width of the cutting edge was measured. Tables 3 and 4 show these measurement results.
It was shown to. The symbol A in the column of the core composition of the cored Ti-based composite carbonitride phase in Tables 3 and 4 indicates that the core is (Ti, M) C
N, and B shows the case where the core is made of TiCN. Therefore, A + B shows that the core is made of (Ti, M) C
Cored Ti-based composite carbonitride phase composed of N
The case where a cored Ti-based composite carbonitride phase composed of CN coexists is shown.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

[Table 4]

[0016]

From the results shown in Tables 3 and 4, the cermet tools 1 to 17 of the present invention have a surface of a cored structure constituting a cored Ti-based composite carbonitride phase, which is a hard dispersed phase of cermet. Portion has a lower Ti concentration than the core portion, and W, M
The combined concentration of at least one of o, Ta, and Nb has a relatively high concentration gradient, but 30% by area or more of the cored tissue, or the entire cored tissue is deformed cored. Although the concentration gradient of the surface portion and the core portion of the cored structure constituting the cored Ti-based composite carbonitride phase is the same, the entire cored structure has the surface portion corresponding to the core portion. It is evident that, compared to the comparative cermet tools 1 to 17 having a completely enclosed, fixed cored structure, the steel shows higher fracture resistance in wet high-cut interrupted cutting of steel under extremely severe cutting conditions. As described above, the cermet tool of the present invention has excellent fracture resistance, so that not only continuous cutting, but also the occurrence of chipping or chipping of the cutting edge even when performing intermittent cutting under heavy cutting conditions. By exhibiting excellent cutting performance over a long period of time, it is possible to contribute to labor saving and energy saving in cutting work, and it is possible to satisfactorily cope with FA.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an internal structure of a cermet tool 7 of the present invention as observed by an electron microscope.

FIG. 2 is a schematic diagram showing an internal structure of a comparative cermet tool 6 by an electron microscope.

Continued on the front page (72) Inventor Katsuhisa Nonaka 1511 Furamagi, Ishishita-cho, Yuki-gun, Ibaraki Pref. Mitsubishi Materials Corporation Tsukuba Works

Claims (1)

[Claims] 1. An electron microscopic structure observation shows that the hard dispersed phase is
5 to 97 area%, with the balance Co and / or Ni
Wherein the hard dispersed phase comprises: (a) a core portion comprising titanium carbonitride or Ti, W, M
o, Ta, and at least one of Nb and Ti-based composite carbonitride, and the surface portions are all Ti, W, M
It is composed of a Ti-based composite carbonitride with at least one of o, Ta, and Nb, but has a lower Ti concentration than the core, and at least one of W, Mo, Ta, and Nb. The combined concentration has a cored tissue with a relatively high concentration gradient,
The cored structure has a deformed cored structure in which 30% by area or more of the whole has a surface portion discontinuously distributed and a part of the core portion is exposed to the binding phase, and the rest has a surface portion. Has a fixed cored structure completely surrounding the core, or the cored tissue has the deformed cored structure as a whole.
(b) titanium boride phase, wherein the ratio of the cored Ti-based composite carbonitride phase is 83 to 96 area% and the ratio of the titanium boride phase is 0.5 A cutting tool made of titanium carbonitride-based cermet having excellent fracture resistance, comprising a titanium carbonitride-based cermet having an area of about 2% by area.