JP2003191108A - Cermet tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cermet tool with superior chipping resistance by improving chipping resistance while securing wear resistance in high speed cutting of the cermet tool. <P>SOLUTION: In the cermet tool, an area ratio of a hard phase using Ti as a main metal component and W as a mandatory component, including one type or more than one type of transition metal elements from groups IVa, Va and VIa of the periodic table, and mainly comprising carbonitride of the metal elements is ≥80%, and the rest comprises a binder phase mainly comprising Co, Ni and unavoidable impurities. It is characterized in that a Ti concentration and a W concentration increase from an interior toward a surface layer part. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cermet tool that exhibits excellent wear resistance and chipping resistance when used for cutting steel, for example.

[0002]

2. Description of the Related Art TiCN-based cermets are widely used as cutting tools. However, even TiCN-based cermets are inferior in toughness as compared with WC-Co based cemented carbides, so their applications are mainly limited to finish cutting.
On the other hand, the TiCN-based cermet contains a considerable amount of nitrogen, and this volatilizes as a part of gas during sintering (denitrification), so it is necessary to perform sintering while controlling denitrification.
This complicates the sintering of the cermet and makes it difficult to control. In addition, denitrification causes a change in the concentration of the component from the surface to the inside, which causes changes in properties such as texture and hardness, making it difficult to obtain desired properties. Attempts have also been made to improve the properties near the surface by utilizing this. As an example, a method of forming a softened layer having high toughness on the surface of a sintered body by introducing nitrogen gas at a temperature not higher than the liquid phase appearance temperature (Japanese Patent Publication No. 59-14).
No. 534), a method of forming a hardened layer on the surface of a sintered body by performing sintering in a reducing atmosphere containing CO (Japanese Patent Publication No. 59-17176), and CO gas in a cooling step after sintering. A method of obtaining uniform mechanical properties from the surface to the inside (Japanese Patent Publication No. 60-3461).
No. 8) has been proposed.

[0003]

However, the Japanese Patent Publication No. 59-
The cermet tools described in Japanese Patent Publication No. 14534 and Japanese Patent Publication No. 60-34618 have a drawback that the wear resistance is insufficient at high speed cutting, and the cermet tools described in Japanese Patent Publication No. 59-17176 have wear resistance at high speed cutting. Although it is possible to obtain excellent long life, there is a problem that when it is used for intermittent cutting such as milling, it is likely to be chipped.

[0004]

Therefore, the present inventors have
In order to further improve the fracture resistance while ensuring the wear resistance of the cermet tool in high-speed cutting, an intensive study was conducted focusing on the concentration distribution of metal components. As a result, by increasing the concentrations of Ti and W from the inside toward the surface, the vicinity of the surface can be made to have high hardness and high toughness, and a cermet tool having excellent fracture resistance as compared with the prior art can be obtained. I got a research result that I can.

The present invention has been made on the basis of the above research results, and contains Ti as a main component as a metal component, W as an essential component, and one of transition metal elements of the 4a, 5a, and 6a groups of the periodic table. Alternatively, in a cermet tool containing two or more kinds, the hard phase mainly composed of carbonitrides of these metal elements has an area ratio of 80% or more, and the balance consisting of a binder phase mainly composed of Co, Ni and unavoidable impurities, The cermet tool is characterized in that the Ti concentration and the W concentration increase from the inside toward the surface layer portion.

The detailed reasons for limiting the cermet tool of the present invention will be described below. First, W is indispensable as a metal component because W is usually added in the form of WC to improve the wettability during sintering of TiCN, which is a carbonitride composed of Ti as a main component, and a binder phase. This is because the sinterability can be improved. At the same time, the carbonitride containing W has a lower hardness and a higher toughness than the carbonitride containing Ti as a main component, and therefore has a function of increasing the toughness of the entire cermet.

Next, as a metal element, 4a in the periodic table,
It is essential to include one or more kinds of 5a and 6a group transition metal elements. By adding these elements, for example, in the case of Ta and Nb, respectively, crater wear resistance is improved. This is because it is possible to improve the characteristics of the cermet tool. Also, Zr, Hf, V
This is because the addition of the above makes it possible to improve the plastic deformation resistance of the cermet tool, and it becomes possible to use it at a higher cutting speed. Further, Mo, like W, improves the wettability between TiCN and the binder phase during sintering and enables the production of a sintered body having no pores. Some of these metal elements added with Ti and W form a single carbonitride phase,
In addition, the rest form solid solution with each other to form a double short nitride to form a hard phase, and some of these metal elements dissolve in the binder phase to strengthen the binder phase by solid solution, Plays a role in improving strength, heat resistance, and plastic deformation resistance. In addition, the hard phase area ratio is set to 80% or more because when it is 80% or less, the amount of hard phase is small and it becomes impossible to obtain a predetermined hardness which is one of the most important characteristics as a cermet tool, and wear resistance is reduced. This is because the sex is reduced.

In the cermet tool of the present invention, Ti
It is characterized in that the concentration and the W concentration increase from the inside toward the surface layer portion, which has the following meanings. That is, when comparing TiCN and WC, the hardness is TiC.
N is high and WC is high in toughness. In an actual cermet tool, particles of TiCN and WC do not exist alone, but a hard phase is formed as a carbonitride solid solution except for a part of TiCN. However, even when it becomes a carbonitride solid solution, the carbonitride solid solution containing a large amount of Ti tends to have a higher hardness than the solid solution containing a large amount of W, and conversely, the carbonitride solid solution containing a large amount of W contains a solid solution containing a large amount of Ti. Toughness tends to be higher than Therefore, it is possible to increase both hardness and toughness in the vicinity of the surface by increasing the Ti concentration and the W concentration from the inside toward the surface layer portion. Here, the surface layer portion refers to a region up to about 0.5 mm from the surface of the cermet tool, and is characterized in that the concentrations of Ti and W are gradually increased from the inside toward the surface layer portion. More specifically, the Ti concentration and the W concentration in the portion 0.1 mm from the surface are 1.015 and 1.05 times or more the Ti concentration and the W concentration in the portion 1 mm from the surface, respectively. Here, the element concentration of 0.1 mm is adopted as the surface layer portion in the cermet tool because denitrification occurs at the time of sintering as described above, and as a result, a portion of the surface of about 20 to 30 μm extremely close to the surface is affected. This is because the concentrations of these elements are easily affected by a slight difference in the sintering atmosphere, the installation position in the sintering furnace, and the like. Hereinafter, the cermet tool of the present invention will be specifically described with reference to examples.

[0009]

Example: 0.4 as a hard phase forming component as a raw material powder
TiCN, WC, Ta with average particle size of μm to 3 μm
C, NbC, ZrC, VC and 1 as a bonded phase forming component
To Co powder and Ni powder having an average particle diameter of 1.5 μm were prepared. These powders were added to the composition shown in Table 1,
After 6 hours of wet mixing and drying with an attritor, 1.0t
Press molding at onf / cm2, and vacuum up to 1300 ° C in 0.1 Torr or less, 1300 ° C or more in 1To.
Sintering was performed at 1400 to 1600 ° C. in a nitrogen atmosphere of rr or less. The holding time was set to 1 to 2 hours, and after sintering, quenching was performed with nitrogen gas. Through the above steps, the invention examples 1 to 1
Eight SNMN432 and SEK422 shaped inserts were manufactured.

[0010]

[Table 1]

Next, as Comparative Examples 9 to 13, cutting tools other than the present invention were also manufactured. In some cases of these comparative examples, after completion of the sintering and holding among the sintering conditions, the furnace was cooled to 800 ° C. without quenching with nitrogen gas. The raw material powder is
Although carbides, nitrides, and carbonitrides of simple substances have been taken up, it goes without saying that solid solution carbides, nitrides, and carbonitrides containing two or more kinds of these can be used. Also,
It is also possible to add an appropriate amount of hard carbides, nitrides, carbonitrides, etc. other than those shown in this embodiment.

With respect to the present invention examples 1 to 8 and comparative examples 9 to 13, after grinding 0.05 mm and 1.0 mm from the surface,
After polishing, the structure was observed by SEM. Further, the element concentration was analyzed from the surface by fluorescent X-ray analysis. Further, by using these, as a cutting specification 1, a work material: SC
Round bar of M440 (hardness HB220), cutting speed: 350
m / min, depth of cut: 1.5 mm, feed: 0.3 mm
Continuous cutting test under the condition of / rev (life evaluation was performed with flank wear of 0.3 mm), and as cutting specifications 2,
A milling cutting test (life evaluation was carried out with a life up to fracture) was carried out under the conditions of a work material: SKD11, a cutting speed: 150 m / min, a depth of cut: 2 mm, and a feed per blade of 0.15 mm. The results are shown in Table 2.

[0013]

[Table 2]

Further, FIG. 1 shows the element concentration distribution from the surface to the inside of Example 5. From Table 2, the tool 1 of the present invention
It is clear that the samples Nos. 8 to 8 show much better cutting life than the comparative examples 9 to 13 in both high speed cutting and milling of steel.

[0015]

From the above, it is clear that the cermet tool to which the present invention is applied is industrially significant in that it contributes to labor saving of cutting and cost reduction.

[Brief description of drawings]

FIG. 1 shows the element concentration distribution from the surface to the inside of Example 5 of the present invention, with the value of 1 mm from the surface as a reference (0), and shows the increase and decrease thereof.

Claims (2)

[Claims] 1. A metal nitride containing Ti as a main component, W as an essential component, and one or more of transition metal elements of groups 4a, 5a, and 6a of the periodic table, and carbonitrides of these metal elements. In a cermet tool having a hard phase mainly composed of 80% or more in area ratio and the remainder being a binder phase mainly composed of Co, Ni and unavoidable impurities, Ti concentration and W concentration increase from the inside toward the surface layer part. A cermet tool that is characterized by 2. The cermet tool according to claim 1, wherein
A cermet tool characterized in that the Ti concentration and the W concentration in a portion 0.1 mm from the surface of the cermet are 1.015 and 1.05 times or more the Ti concentration and the W concentration in a portion 1 mm from the surface, respectively.