JPS62103336A - High-toughness cermet for dot wire and its production - Google Patents

Abstract

PURPOSE:To obtain the titled high-toughness cermet excellent in bending strength or deflectivity, not to mention in hardness and wear resistance, by providing a composition which contains each prescribed amount of Ni and Mo2C and in which the quantity of contained gas in the balance TiCN, C/(C+N), and the grain size of TiCN are specified, respectively. CONSTITUTION:In a TiCN-Mo2C-Ni cermet, Ni for effecting the bonding of rapid fine grains and Mo2C for improving wettability between TiCN and Ni by forming a so-called peripheral structure at the periphery of the rigid fine grains are incorporated by 15-30wt% and 1-10wt%, respectively. Further, the amount of contained gas in the balance TiCN, C/(C+N), is regulated to 0.5-0.9 and the grain size of TiCN is limited to 0.05-0.5mum. The titled cermet obtained in the above manner shows very high deflectivity in the dimensional range as dot wire, so that it can be most suitably used as a material for dot wire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a high toughness cermet for dot wires used in dot printers and a method for manufacturing the same.

[Conventional technology]

Conventional dot wire materials used in dot printers are generally powdered high-speed steel materials or super hard alloy materials. As the speed of dot printers increases, the former powdered high-speed steel material has sufficient toughness as a material for dot wires, but is unsatisfactory in terms of life due to its slightly inferior wear resistance. On the other hand, the latter is a super hard goldfish material.

Although it has sufficient wear resistance, it has a high specific gravity.

This is inconvenient because it goes against the demand for lighter components as speed increases.

[Problem that the invention seeks to solve]

As mentioned above, the characteristics required for dot wire materials used in high-speed dot printers are:

While having wear resistance comparable to that of superhard alloys, the components are required to be lightweight. Cermets that have wear resistance have traditionally been used as tool materials, and the scope of their application has been expanding recently, but conventional cermets for tools have a problem of extremely high hardness but low bending strength or transverse rupture strength. There is a point.

This was insufficient as a material for dot wires.

Figure 10 shows Ti CN-WC-Ta C-NbC-Mo, which is a cermet conventionally known as a tool material.
It is a figure showing the relationship between test piece thickness and transverse rupture strength in 2C-Ni (binder Ni: 20%). The width of each test piece was twice the thickness. As is clear from the figure, the transverse rupture strength sharply decreases in the region where the thickness of the test piece is less than 1f1. Therefore, as a material used at a thickness of about 0.3 μm, such as dot wire, the transverse rupture strength is insufficient, so it has not been put to practical use.

Therefore, the inventors conducted various studies and found that, as is clear from the results shown in FIGS. 11 and 12, the content of W in the above composition is It's unnecessary.

They also found that reducing the thickness of the surrounding tissue layer formed around the hard particles is effective in improving the transverse rupture strength. That is, FIG. 11 shows the cermet with Ni as a binder in a test piece of 0.5 diameter.
FIG. 2 is a diagram showing the relationship between the amount of W solid solution in (20%) and the transverse rupture strength, and it shows that when the amount of W solid solution is decreased, the transverse rupture strength tends to improve approximately in inverse proportion. Next, FIG. 12 is a diagram showing the relationship between the transverse rupture strength, the thickness of the surrounding tissue, and the transverse rupture strength in the test piece, and particularly in the region where the thickness of the surrounding tissue is 0.5 μm or less, the transverse rupture This shows that the improvement is significant.

Based on the above findings, the present invention solves the problems that exist when cermet, which has been conventionally used as a tool material, is used as a dot wire material, and improves hardness and wear resistance.

The object of the present invention is to provide a high-toughness cermet for dot wires that has the same characteristics as conventional materials and has a high bending strength or transverse rupture strength, and a method for manufacturing the same.

[Means for solving problems]

In order to solve the above problems, the present invention employs the following technical means.

First, in the first invention, TiCN-Mo2C-
In Ni-based cermet, Ni: 15 to 30% by weight,
Moz C=1-10% by weight, TiCN gas content C/(C+N) 0.5-0.9 and TiCN
The particle size is 0.05 to 0.5 μm.

Next, a second invention is an invention of a method for manufacturing the above-mentioned cermet, which is characterized in that the method for manufacturing a TiCN-Mo2C--Ni-based cermet comprises sintering and subsequent hot isostatic pressing under the following conditions. This is a method for producing high toughness cermet for dot wire.

(a) Sintering temperature: TS = 1300-1450°C
(b) Hot isostatic pressure pressurization (C1 hot isostatic pressure: PH = 500 to 1500 atm).

Further, a third invention is one in which a resintering process is further added to the second invention, and the resintering temperature TR is T, -50°C≦
TR≦TS+50°C.

Components and other limiting conditions in the present invention will be described.

Ni is an element that is contained in order to achieve a bonding effect between the hard fine particles that constitute the cermet.

If it is less than 15% by weight, N acts as a binder between the particles.
This is disadvantageous because the transverse rupture strength decreases because the amount of i is insufficient and the movement of one particle is restricted. On the other hand, if it exceeds 30%, it is called N.
Since the i-boules appear, the distance between particles becomes excessive, which is undesirable because the transverse rupture strength decreases. Therefore, the amount of Ni is 1
It was limited to 5 to 30% by weight.

Next, Mo2C is a component that is included in order to form a so-called peripheral structure around the hard particles and improve the wettability of TiCN and Ni, but if it is less than 1% by weight, the above effect cannot be expected. On the other hand, if it exceeds 15% by weight, the layer thickness of the surrounding tissue increases to form a so-called skeleton, which serves as a starting point for progression of fracture, which is disadvantageous because it causes a decrease in transverse rupture strength. Therefore, MotC@ was determined to have a weight of 1 to 15%.

If the value of the gas contained in TiCN fc/(C+N) is less than 0.5, the amount of N will be too large and pores will be easily generated during denitrification, which will reduce sinterability, which is disadvantageous. . On the other hand, if the above-mentioned value exceeds 0.9, it is not preferable because it promotes the growth of two grains and forms coarse grains, which lowers the transverse rupture strength.

Therefore, the value of C/(C+N) was limited to 0.5 to 0.9.

Next, since the transverse rupture strength is improved as the particle size of TiCN becomes smaller, it is desirable that the TiCN be fine particles. Therefore, the particle size is 0.5 μm.
If it exceeds this, it is inconvenient because the transverse rupture strength required for the dot wire cannot be expected. On the other hand, the particle size is 0.05μ
If the particle diameter is less than m, although the transverse rupture strength is improved, the particles become too fine and handling in the manufacturing process becomes very complicated, so it is not preferable. Therefore, the particle size of TiCN is 0.05~
It was limited to 0.5 μm.

The reasons for limiting the temperature and pressure in the above cermet manufacturing methods of the second and third inventions will now be described.

If the sintering temperature is less than 1,300°C, it is disadvantageous because Nj, which should act as a binder for hard particles, does not dissolve and penetrate uniformly, whereas if it exceeds 1,450°C, two-grain growth becomes intense, which reduces the transverse rupture strength. 1.
The temperature was limited to 300°C to 1450°C.

Next, hot isostatic pressure (Hot l5ostatic Pr
(hereinafter referred to as HIP) conditions are described below.

HIP treatment is an effective means for improving transverse rupture strength because it crushes minute pores generated in the cermet sintered body and eliminates the origin of fracture induction, but HIP fjL degree (TI (
) is closely related to the sintering temperature (T3). In other words, when the HIP temperature ('rl) is less than (T 5-50°C), the transverse rupture strength is the same as that without HIP treatment, and there is no effect of HIP, and on the other hand (TS + 50°C)
Exceeding this is disadvantageous because it induces coarse growth of one grain, resulting in a large decrease in transverse rupture strength. Therefore, HIP temperature ('r
o) was limited to T, -50°C≦T, ≦rs+so°C.

Next, the pressure for HIP treatment has an optimum range corresponding to the above-mentioned Ni1l. However, if the pressure is less than 500 atm, the HIP treatment will not have the effect of crushing the micropores, which is disadvantageous. Moreover, if the pressure exceeds 1500 atmospheres, gas will enter the Ni binder to generate cavities, which will become starting points and induce fractures, which will reduce the transverse rupture strength, which is not preferable. Therefore, the pressure of HIP treatment is 500
The pressure was limited to ~1500 atm.

Next, the reason for limiting the resintering temperature (T, I) in the third invention will be described. As mentioned above, the F[P treatment is a process of crushing micropores in the sintered body by external pressure, and embeds Ni in the micropores. However, if the material remains as it is after the HIP treatment, it may become a Ni pool depending on the case, which may become a starting point for fracture and reduce the transverse rupture strength.

Therefore, the Ni pool is removed by diffusing the Ni that has entered into the micropores by resintering. The resintering temperature (TR) has a close relationship with the sintering temperature (T3), and if it is lower than (T, -50°C), the effect of the HIP treatment cannot be expected and the transverse rupture strength does not improve.

On the other hand, if it exceeds (TS + 50°C), it is disadvantageous because micropores are generated and the transverse rupture strength is lowered. Therefore, the resintering temperature (TR) is TS-50℃≦TR≦'rs+so
It was limited to ℃.

[Example 1] TiCN 75% by weight, Mo2C-5 weight%, weight Ni2
After mixing O weight% in powder state and molding, 1400℃
9 different thicknesses were prepared by sintering.

The results of transverse rupture strength measurements are shown in Figure 1. In addition, the width dimension of each test piece was made to be twice the thickness dimension.

As is clear from FIG. 1, it can be seen that test specimens with a thickness of less than 1 piece exhibit extremely high transverse rupture strength.

Next, TiCN particle size 0.3 it m, Mow C
The dependence of transverse rupture strength on Ni weight % is shown in FIG. 2, assuming 5 weight %. The cross-sectional dimensions of the test piece are Q, 5m x 1w. As is clear from the figure, the transverse rupture strength decreases in the region where Ni is less than 15% by weight. That is, in this region, the amount of Ni as a binder is insufficient, so the movement of hard particles is restricted. On the other hand, if it exceeds 30% by weight, the amount of Ni becomes too large and forms a Ni pool, resulting in an excessive distance between two particles, resulting in a sharp decrease in transverse rupture strength.

FIGS. 3 to 5 are diagrams showing the relationship between transverse rupture strength and MotC weight % weight % 2 when the binder Ni content is 5 weight %. The dimensions of the test piece are the same as those shown in Figure 2 above. First, in Figure 3, Mo2
C- If it is less than 1% by weight, the transverse rupture strength shows an extremely low value. Mo2C- forms a peripheral structure around the hard particles and has the effect of improving the wettability between Tt CN and the binder Ni, but if it is less than 1% by weight, this effect is not sufficient, so the transverse rupture strength becomes a low value. It's staying. On the other hand, even in a range where Mo2C- exceeds 15% by weight, there is a region where the transverse rupture strength is low.

That is, in this region, as a result of the excessive thickness of the surrounding tissue due to Mo2C, a so-called skeleton is formed, and this serves as a starting point for progression of fracture, so it is presumed that the transverse rupture strength decreases. FIG. 4 shows that, similar to the amount of Mo2C mentioned above, the value of transverse rupture strength is drastically reduced in regions where the thickness of the surrounding tissue is extremely small and in regions where the thickness exceeds 1 μm. Next, as is clear from Fig. 5, the transverse rupture strength gradually decreases in the region where the value of C/(C+N) is less than 0.5. This is because when the amount of N becomes too large, vacancies are likely to occur during denitrification. This is because it inhibits sinterability. On the other hand, C/
When the value of (C+N) exceeds 0.9, single-grain growth is promoted and coarse particles are formed, resulting in a sharp decrease in the transverse rupture strength value.

Next, FIG. 6 is a diagram showing the relationship between transverse rupture strength and TiCN particle size, with the binder Ni fi set at 209% by weight,
Ti CN 75% by weight and MO2C 5% by weight. As is clear from the figure. The smaller the TiCN particle size, the higher the transverse rupture strength, which decreases in approximately inverse proportion to the increase in particle size.

[Example 2] The sintered body produced by sintering at 1400°C in Example 1 was pressurized by HIP (hot isostatic pressure) in an Ar atmosphere. The results are shown in Figures 7 and 8. .

Figure 7 shows that the binder Ni is 20% by weight, and C/C+N
The value of 0. 7 is a diagram showing the relationship between transverse rupture strength and HIP treatment temperature. As is clear from the figure,
At HIP temperatures of 1200° C. and 1300° C., the transverse rupture strength remained at the same level as that without HIP treatment, and the effect of HIP treatment did not appear. On the other hand, when the temperature exceeds 1500°C, the transverse rupture strength decreases significantly. Next, FIG. 8 is a diagram showing the relationship between the transverse rupture strength and the HIP pressure when the binder Ni is 15%, 20%, and 30% by weight, respectively. In other words, as is clear from the figure, for each Ni%, the optimum HI
P pressure is present. The purpose of the HIP treatment is to fill the microscopic pores existing in the sintered body with binder Ni and to remove and eliminate the origin of fracture, thereby improving the transverse rupture strength. However, if the pressure is less than 500 atm, the effect cannot be exhibited, and the transverse rupture strength remains the same as that without HIP treatment. On the other hand, if the HIP pressure is too high.

For example, in one containing 30% by weight of Ni. When the pressure exceeds 1,500 atmospheres, gas enters the Ni binder and forms cavities. This becomes the starting point of fracture and reduces the transverse rupture strength.

[Example 3] TiCN75% by weight, Mo□05% by weight and Ni2O
FIG. 9 shows the results of molding with raw material powder having a composition of % by weight, sintering at 1400° C., HIPing at 1000 atm, and re-sintering at various temperatures. As is clear from the figure, when the resintering temperature is lower than 1350°C, the effect of the resintering treatment is small.

The HIP treatment does not have the effect of diffusing the Ni that has penetrated into the micropores, and the transverse rupture strength remains at the same value as the HIP treatment alone. On the other hand, the resintering temperature is 1450℃
If it exceeds this, on the contrary, micropores will appear, which will serve as fracture starting points, and as a result, the transverse rupture strength will be greatly reduced.

〔Effect of the invention〕

Since the present invention has the transverse rupture force and function as described above, the following effects can be expected.

(1) It exhibits extremely high transverse rupture strength within the size range used as dot wires, making it ideal as a material for dot wires.

(2) Since the hardness and abrasion resistance are equal to or higher than those of conventional cermets, a long life can be expected when used in high-speed dot wires.

(3) Since fine pores are crushed by HIP treatment after shaping and sintering, fracture starting points can be removed and high toughness can be imparted.

(4) Toughness can be further improved by performing re-packing and sintering treatment after HIP.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the transverse rupture strength and the thickness of the test piece in Example 1 of the present invention, FIG. 2 is a diagram showing the relationship between the transverse rupture strength and the amount of Ni, and FIG. A diagram showing the relationship between the transverse rupture force and the amount of MotC, FIG. 4 is a diagram showing the relationship between the transverse rupture force and the thickness of the surrounding tissue, and FIG. 5 is a diagram showing the relationship between the transverse rupture force and C/C+N. , FIG. 6 is a diagram showing the relationship between the transverse rupture strength and the TiCN particle size, and FIG. 7 is a diagram showing the relationship between the transverse rupture strength and the TiCN particle size, and FIG.
FIG. 8 is a diagram showing the relationship between transverse rupture strength and HIP pressure, and FIG. 9 is a diagram showing the relationship between transverse rupture strength and resintering temperature in Example 3 of the present invention. figure. Figure 10 is a diagram showing the relationship between transverse rupture strength and specimen thickness in conventional cermets, and Figure 11 shows the relationship between the transverse rupture strength and W in Ni.
FIG. 12 is a diagram showing the relationship between the transverse rupture strength and the thickness of the surrounding tissue. Patent applicant: Hitachi Metals, Ltd. (1 other person) Patent attorney: Mori 1) (1% asthma)

Claims (2)

[Claims] (1) In the TiCN-Mo_2C-Ni cermet, Ni: 15 to 30% by weight, Mo_2C: 1 to 10% by weight, and the amount of gas contained in TiCN C/(C+N) is 0.5
A high toughness cermet for dot wires, characterized in that the TiCN particle size is 0.05 to 0.5 μm. (2) A method for producing a high-toughness cermet for dot wires, which comprises sintering and subsequent hot isostatic pressing under the following conditions. (a) Sintering temperature: T_S = 1300-1450℃ (b)
Hot isostatic pressure temperature: T_H T_S-50℃≦T_H≦T_S+50℃ (c) Hot isostatic pressure: P_H=500 to 1500 atm (3) In the method for manufacturing TiCN-Mo_2C-Ni cermet, sintering is performed under the following conditions. 1. A method for producing a high-toughness cermet for dot wires, which comprises sintering, subsequent hot isostatic pressing, and further sintering. (a) Sintering temperature: T_S = 1300-1450℃ (b)
Hot isostatic pressure temperature: T_H T_S-50℃≦T_H≦T_S+50℃ (c) Hot isostatic pressure: P_H=500 to 1500 atm (d) Re-sintering temperature: T_R T_S-50℃≦T_R≦T_S+50℃