JPS6037051B2 - Method for producing hexagonal type solid solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of a composite carbide aimed at replacing WC, the main raw material of cemented carbide, 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, Cr are added according to the required characteristics of the alloy,
Iron group metals are used as bonding metals.
However, W is a relatively expensive metal and can only be found in very small quantities on earth, so it is considered a so-called "strategic" material. The degree of its use can be said to be of political value. Therefore, if the demand for cemented carbide containing W as a main component increases, this resource problem will naturally arise. If WC could be replaced with other high melting point metal carbides, it would have a significant impact on industry. Molybdenum monocarbide is the most promising candidate.

This carbide is considered to be a simple hexagonal type with the same crystal structure as WC, and its mechanical properties are also thought to be close to WC. However, the existence of molybdenum monocarbide is unstable, as has been questioned to this day, and it has been stabilized for the first time as a solid solution carbide or solid nitride of molybdenum and tungsten by forming a solid solution with tungsten carbide. I can do it. This method is 19
In 1950, W. Although it was first discovered by David David, this solid port was considered to be of industrial value at the time, and was not developed or studied much. The present invention has this (Mo.W)C, and (Mo.W)(C
This invention relates to a method for stably producing compounds such as N) and (Mo.W) (CNO).

The problem with (Mo.W)C, which has been studied in the past, is that this carbide is unstable and generates double carbides such as M2C type, which causes a decrease in alloy strength and hardness. be. However, from the perspective of practical I performance, M
A major problem is not only the precipitation of C type precipitates, but also the fact that improvements in ballability and heat resistance properties cannot be expected due to the fine grain size of carbides. That is, the WC grain size in the cemented carbide controls the thickness of the Co layer, which is the bonding metal, and by adjusting this adjustment, the tool exhibits excellent properties as a hot tool, an impact tool, and a wear-resistant tool. Since MoC has the same simple hexagonal type crystal structure as WC, the structure in the alloy is very similar to that of WC. In this case, the most important point is the particle size of (Mo.W)C. The present invention is excellent as a heat-resistant tool and an impact-resistant tool, but the manufacturing method is characterized by mixing a large amount of Fe and AI, and first melting Mo and W in a metal melt, thereby ensuring sufficient diffusion of Mo and W. After that, (Mo.W)C monocarbide is precipitated in the cooling process.

Another purpose is to produce a simple hexagonal type raw material powder by dissolving Fe and AI by acid treatment after cooling and then reheating to stabilize the coarse (MoW) C powder. Attempts to generate carbides using Fe and AI have long been well known as the thermite method, but the point of the present invention is to precipitate a hexagonal type carbide of Mo and W as a solid port. .

The second feature of the present invention is that in the coexistence of Fe-AI-C,
This is the discovery and practical application of the conditions for precipitating MoC, WC, and solid ports.

It is difficult to set the conditions; for example, simply applying the thermite method will cause WC, W2C,
Complex carbides such as Fe3W3C are formed, and MoC
Also in this case, carbides such as Mo2C and Fe3Mo3C are precipitated separately. A uniform solid solution cannot be formed between carbides having complex crystal shapes and different properties. In addition, even if Datae (Mo.W) C powder can be produced, the
% is difficult to obtain.

As a result of examining various heating conditions, the present inventors found that after obtaining the carbide obtained by melt analysis and obtaining it as a powder by acid treatment,
By heating the powder again at a temperature at which (Mo.W)C is stable, (Mo.W)C having the complete theoretical carbon content is obtained.
It was discovered that powder can be obtained.

In the present invention, the heating conditions may be vacuum and hydrogen, but it has been found that a more perfect hexagonal type alloy can be obtained by heating in N2 or CO gas for further stability. Furthermore, the cheapest way to produce this carbide is to use a ferroalloy as a starting material. The purpose of this carbide is to create a hexagonal type compound, but Mo.
It is also possible to make C drop out of the park. In this manufacturing method, heating is preferably performed for 1500 pm or more.

If the temperature is below 1500°C, no liquid phase with Fe will be produced, so that the solid solution reaction will be difficult to proceed. In addition, the secondary heating temperature is (Mo.W
) The stable temperature of C, which varies depending on the ratio of Mo and W, was found to be preferably between 1180qo and 1600qC. Example 1 Metallic Mo spots. 4 parts, W powder 31.5 parts, C 7 parts, AI
After mixing 22 parts of powder and 13 parts of Fe powder, 195
After heating at 0° C., acid treatment with hydrochloric acid and washing with water were performed to dissolve and separate and remove aluminum, iron, carbon, and other impurities.

The solid solution carbide of Mo and W thus obtained has a concentration of 1300qC
The mixture was stabilized by heating in N2 for 3 minutes. When this was crushed and examined using X-rays, it was found that all of the carbides had a WC type simple hexagonal structure. Analysis of the carbon content showed that the amount of bound carbon was 8.90% and the free carbon was 0.05%, indicating that it was a composite carbide with a close to stoichiometric composition. Example 2 41.4 parts of Moo3 powder, 28.6 parts of 03 powder, 14.8 parts of carbon powder, 17 parts of AI, 13 parts of Fe, 1
The reaction was carried out at a temperature of 800°C.

After the reaction, heat treatment was performed in acid treatment N2 as in Example 1. Analysis of the carbon content of the obtained carbide revealed that the amount of bound carbon was 8.93%, the free carbon content was 0.07%, and the N2 analysis value was 0.
．． It was 3%. Example 3 45.2 parts of Moo3 powder and 21.2 parts of W03 powder. Seito, 8.8 parts of Cr203 powder and 25 parts of carbon were added in advance to 120 parts in a N2 stream.
After reacting at 0qo, 1 portion of Fe-AI alloy was added and reacting at 2300oo.

Thereafter, the powder was subjected to acid treatment and stabilization treatment as in Example 1, and then examined using X-rays. All of the obtained carbides were transformed into hexagonal type solid solutions.

0% Ni powder was added to this carbide, and an alloy was prepared through the steps of wet mixing, drying, and freezing. The resulting alloy had excellent corrosion resistance. Example 4 6 parts of ferromolybdenum and 4 parts of ferrotungsten were added to 10 parts of AI powder and 15 parts of carbon powder and heated to about 2400 qo in an electric arc furnace, then acid treated as in Example 1 and the powder was heated with N2. Heating was performed at 130,000 ℃ in CO gas.

Claims (1)

[Claims] 1. In the production of a solid solution of a composite carbide or carbonitride of molybdenum and tungsten whose crystal structure is a simple hexagonal type, Fe, Al, and carbon coexist at the same time as metals or compounds of molybdenum and tungsten. A manufacturing method in which Fe and Al are dissolved by heating at a temperature of 1500° C. or higher, followed by acid treatment. 2. In claim 1, a composite carbide or carbonitride consisting of molybdenum, tungsten and chromium,
A method for producing a solid solution whose crystal structure is a simple hexagonal type. 3 In claim 1, after reacting a predetermined compound of molybdenum and tungsten, the solid solution carbide of molybdenum and tungsten obtained by acid treatment is again treated with 118
A manufacturing method characterized by reheating in a temperature range of 0 to 1600°C. 4. A manufacturing method according to claim 1 or 2, characterized in that the main starting material is a ferroalloy.