JPS6048448B2 - Method for producing solid solution of hexagonal monocarbide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of a composite carbide product for the purpose of replacing cemented carbide, particularly WC in the alloy, with MoC.

Conventionally, cemented carbide has WC as its main component, with Ti and T added to it.
High melting point metal carbides or carbonitrides such as a, Nb, Mo, Hf, V, and Cr are added depending on the required properties of the alloy, and iron group metals are used as the bonding metal.

Although tungsten is a relatively expensive metal for sumo wrestlers,
Since it is extremely rare or undiscoverable on earth,
It is considered a so-called "strategic" material, and its degree of use can be said to have political value. Therefore W
If the demand for cemented carbide whose main component is C increases, this resource problem will naturally arise.

If WC could be replaced with other high melting point metal carbides, the impact on the industry would be significant. Molybdenum monocarbide is the most promising candidate.

Only this carbide is the same as WC. It is a simple hexagonal type with the same crystal structure, and its mechanical properties are thought to be close to WC. However, the existence of molybdenum monocarbide alone is still questionable to this day, and MOC
Attempts are being made to stabilize the . This method was introduced in 1950
W. Although it was first discovered by David Dawihl, at that time no industrial value was found in this solid solution, and not much study was conducted. Recently, with the soaring price of W, (MOxWy) CCX
+Y=1] Research using solid solutions is becoming more active. However, it is very interesting to know why little research has been done on it, and no active attempts have been made to use it. In general, in the production of composite carbides, a homogeneous solid solution can be obtained by heating using a diffusion aid such as carbon dioxide or carbon dioxide.

However, when a solid solution composition containing 70% or more of MOC is heated at a high temperature, a uniform solid solution cannot be obtained only by interdiffusion. This is because MOC is unstable at high temperatures, but (MOC
W) C, -x or (MO-W). C. This is because the WC type solid solution of (MO.W)C cannot be obtained by simply cooling (MO.W). As a stabilization method, MO is reacted once at high temperature. C and W.C.
After diffusion, there is a method of holding the material at a low temperature for a long period of time.
[Unexamined Japanese Patent Publication No. 51-146306 (4)]. However, at low temperatures, (MOW)C,1X,(MOW). C. From (M
It takes a considerable amount of time for diffusion and recrystallization to release more O.W.)C. If such a method were to be carried out industrially, it would have to be heated in a furnace for a long time in order to obtain a complete carbide. This results in low productivity per furnace, which requires a large number of furnaces. On the other hand, if a continuous furnace is used, a long heating furnace would be required, making mass production difficult from an industrial perspective. The inventors (
As a result of various studies on industrially stable production methods for MO-W)C powder, the following problems became clear.

In other words, the easiest way to make (MO・W)C powder is WC6MO. After C is made into a solid solution at high temperature (MO・
W) Carbon is diffused at a temperature at which C is stable, but heating in a vacuum requires a long heating time.
In addition, by omitting the solid solution at a high temperature and forming the solid solution at the oxide stage, this is reduced to form an alloy powder (MOW).
There is also a method of producing (MO.W)C powder by reacting this alloy powder with carbon for a long period of time at a temperature at which (MO.W)C is stable. In either case, long-term heating is required, and if this is to be done in an industrially inexpensive manner, carbon diffusion must be assisted.

In general, carbides of groups ①A, Va, and ②a are stably generated in an H2 atmosphere. However, Schenck
Research by Z. AnOg. Allgem. Chem, 2
O3 (1931) 159] by H.

It is said that MOC is not stable in airflow. Figure 1 shows MOC+H2=1/2M02C+112CH4...(
1) and 112CH4=H2+112C...(2) Changes in the free energy of reaction formation are shown. That is, in H2 gas flow, Cll. Since the generation of is given priority, MOC is H2
I reacted with MO. It decomposes into C and CH. (M.O.
Also in the production reaction of W)C (MOW)C+2H. →．．
(MOW). By the reaction of C + CH,...(3),
The inventors' research also revealed that (MOW)C actually decomposes. On the other hand, a well-known example is the use of CO as a method to make this reaction more active, but it is not effective in H2 gas because the decomposition reaction takes priority.

Moreover, if it is carried out in a vacuum, heating for a long time will be required as described above. The present inventors investigated the heating atmosphere, temperature, and amount of diffusion aid as a catalyst, and found that (MOW) C powder can be stably produced by heating for a short period of q according to the following method. .

In other words, the conditions under which the (MOW)C powder is stabilized are the conditions under which the hexagonal type crystals of the WC type are stabilized by the inclusion of a trace amount of oxygen or nitrogen in the carbide, i.e. in N2 gas or CO gas or CO
The first feature is to prevent the decomposition of carbides by reacting in a mixed gas of CO2 gas and Fe, N as a diffusion aid.
l, CO is used. In particular, the second feature is that Fe is once changed to Fe and C to supply carbon. In addition, the amount of Fe, Ni, and CO contained in the powder is preferably 0.5% or less. *
stomach. If it exceeds 0.5%, the powders will sinter and form an alloy, making it difficult to recover them as powder.

However, when CO and Nl among the iron group elements are used, the supply of carbon is not very active, and it is necessary to add nearly 1%, and the effect of stabilizing carbides is small.

The heating temperature is preferably 1,200° C. or higher, and heating at a temperature of 2,000° C. or higher is not preferred because (MOW) C becomes unstable. In the method of the present invention, even when a solid solution of (MOW)C is formed with carbonitrides of group (1)A, Va, and (2)a group metals, high-quality carbides can be produced using the same concept.

Example 1 54 g of M0 powder) and 46 g of W powder were dissolved in 28% aqueous ammonia.

When this ammonium salt was gradually neutralized with hydrochloric acid, needle-shaped crystals were precipitated. The coprecipitated WO3 and MOO3 were well mixed on the order of angstroms. This oxide was sintered at 800'C in air. Charge this mixed powder into a Ni boat, cover the boat with a lid, and heat. When it was reduced at 1000°C in an air stream, it became an alloy powder of 4μ. 9.0% by weight of carbon powder was added to the (M()W) alloy powder and mixed in a ball mill for 3 hours.

The mixed powder was heated under each heating condition. The properties of the obtained carbide were as shown in Table 1. Experiment No. ．． N for l to 5. Although no diffusion aid was used in the atmosphere, the reaction rate was about 50 to 60%. Experiment No. 6,7 When CO was used as a catalyst, the reaction rate increased by over 98%, but long-term heating was required, and the powder became hard, requiring a long time for pulverization. N using 0.2% Fe. Inside 1
As a result of heating for a period of time, the reaction rate reached 100%, and a good quality carbide was obtained by being sufficiently pulverized. Next, when this was heated in hydrogen in the same manner (Experiment No. 10 to 14), the reaction rate was 80 to 90%, and no good quality carbide was obtained.

Example 2 9.0% by weight of carbon powder was added to the (MOW) alloy powder produced in the same manner as in Example 1, and mixed in a ball mill for 3 hours.

0.2% of N1 was added as a diffusion aid to this mixed powder,
Heated in H2 at 1800°C for 1 hour and cooled to room temperature. The total carbon content (T.C) of the carbide at this time is 8.99
wt%, free carbon (F.C) is 3.7 wt%, T
．． C: total carbon content, F. C: free carbon content (reaction rate - (bonded carbon content/theoretical carbon content) x C.C: bound carbon content (100) A reaction rate of 62% was obtained.

The amount of N2 in this carbide is 0.035%, and the amount of 02 is 0.035%.
It was 0.056%. This carbide was further carbonized under the carbonization conditions shown in Table 2. T. C: total carbon content, F. C: Free carbon content Reaction rate = (Bound carbon content/Theoretical carbon content) x 100 Carbonization conditions (1) 1800°C x IH (in H2) heating (2) 180
After heating at 0°CxIH (in H2) and cooling to room temperature, 1380
°CxIH was heated, and CO gas was introduced during cooling.

(3) Heating at 1800°C x IH (in H2) After cooling to room temperature, 1380'C x IH (N).

Carbonized in (middle). Under carbonization condition (3), only a reaction rate of 95% can be obtained, but under carbonization condition (2), a reaction rate of 100% can be obtained.
A good carbide was obtained.

Example 3 M0.

53g of C powder. 44g of WC powder, 3.0g of carbon powder.
Add 1.0 g of NIO as a diffusion aid to the carbide powder containing 0 g.
g was added and mixed by IH using a Henschel mixer. This mixture was washed with H. The mixture was heated at 1800° C. for 2 hours in an atmosphere and cooled to room temperature. Total carbon content of carbide at this time (T.C)
is 8.96% by weight, free carbon content (FC) is 3.85
% by weight, and a reaction rate of 60% was obtained. This carbide was further carbonized under the carbonization conditions shown in Table 3. T. C
:Total carbon content, F. C: Free carbon content Reaction rate = (Bound carbon content/Theoretical carbon content) x 100 Carbonization conditions (1) 1800°C x
IH (in H2) heating (2) 1800℃ x IH (in H2)
After heating and cooling to room temperature, the mixture was heated at 1380° C. by IH, and CO gas was introduced during cooling.

(3) Heated at 1800°C x IH (in H2), cooled to room temperature, and heated to 1380°C x IH (N).

Carbonized in (middle). Under carbonization condition (3), only a product with a reaction rate of 94% could be obtained, but under carbonization condition (2), a good carbide with a reaction rate of 100% could be obtained.

Example 4 11.3% by weight of TIC powder, MO.

66.6% by weight of C powder and 18.6% by weight of WC powder. A carbide containing 3.8% by weight of carbon powder was mixed by IH using a Henschel mixer. 0.2% Ni was added to this carbide, and heated at 1900°C for 3 g. After cooling to room temperature, IH heating was performed in CO gas at 1500°C. Also, for comparison, the carbon analysis results for those carbonized in a tank, N. ,O. The analysis results are shown in Table 4. T. C: total carbon content, F. C: Free carbon content Reaction rate = (Bound carbon content / Theoretical carbon content) x 100 Carbonization conditions (1) Carbonization at 1900°C x 3 powder (in H2), after cooling to room temperature, 1500'C x IH (in CO) Carbonized at.

(2) Carbonize at 1900°C x 3 powders (in H2), cool to room temperature, and then carbonize at 1500°C x IH (in N). As shown in Table 4, the carbide carbonized under carbonization condition (1) is
It was found that the reaction rate was higher than that of the carbide obtained in 2), and a reaction rate of 100% was obtained.

[Brief explanation of the drawing]

Figure 1 shows MOC+H.

Claims (1)

[Scope of Claims] 1. In the production of a solid solution of a composite carbide, carbonitride or molybdenum compound of molybdenum and tungsten, which is composed of one or more hard phases having a simple hexagonal crystal structure. A monocarbide is created by reacting a mixture of compounds containing molybdenum and tungsten or a solid solution of molybdenum and tungsten with carbon, corresponding to the abundance of molybdenum and tungsten in the molybdenum and tungsten composite carbide, carbonitride or molybdenum compound. In some cases, at least the final heating step is conducted using N_2CO or CO.
A method for producing a solid solution of hexagonal monocarbide, the method comprising heating in an atmosphere containing _2. 2. In the method for producing a solid solution of hexagonal monocarbide according to claim 1, after adding an iron group metal to the raw material, the temperature range is 1200°C to 2000°C in a gas containing N_2, CO or CO_2. A method for producing a solid solution of hexagonal monocarbide, the method comprising heating at . 3. The method for producing a solid solution of hexagonal monocarbide according to claim 2, characterized in that the iron group metal added is Fe, and the amount added is 0.5% by weight or less. Method for producing solid solutions.