JPH1030130A - Method for regenerating cemented carbide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover a raw material powder and a binding material from cemented carbide scrap and regenerated them and particularly to provide a method for regenerating cemented carbide, capable of regenerating a raw material powder of tungsten carbide, etc., into a state free from grain growth and impurity contamination so that it can be reclaimed in the state as a raw material powder for cemented carbide. SOLUTION: In this method of regenerating cemented carbide, a heat resistant pressure container is filled with cemented carbide together with acidic aqueous solution and hydrothermal treatment is performed to dissolve a binding material contained in the cement carbide in the acidic aqueous solution and recover the binding material. Further, a heat resistant pressure container is filled with cemented carbide together with acidic aqueous solution and hydrothermal treatment is performed to dissolve the binding material contained in the cemented carbide in the acidic aqueous solution and remove the binding material, and then, the resultant residual carbide is heated under a nonoxidizing atmosphere, cooled rapidly, and further crushed and reduced to powder, by which the resultant powder is recovered as a raw material powder for cemented carbide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering raw material powder and a binder from cemented carbide scrap and regenerating the same. The present invention relates to a method for regenerating a cemented carbide that can be recycled as raw material powder as it is.

[0002]

2. Description of the Related Art Since cemented carbide is extremely hard, it is frequently used as a disposable cutting edge of a cemented carbide tool, especially a cutting tool, and accordingly, a large amount of used scrap is generated. This cemented carbide is generally made of tungsten carbide (WC),
A hard phase mainly composed of at least one of the group IVa, Va and VIa group metal carbides of the periodic table such as titanium carbide (TiC) and tantalum carbide (TaC);
And a binder phase composed of at least one of nickel (Ni) and cobalt (Co). Since these cemented carbide materials such as tungsten are scarce resources and very expensive, many methods for recovering carbides such as WC, TiC and TaC from cemented carbide scrap have been proposed.

For example, Japanese Patent Publication No. 44-27457 discloses a method in which cemented carbide scrap is covered with carbon, and
There is disclosed a method of heat-treating at a temperature of ° C., followed by crushing and powdering. However, in such means, 18
Since heating at a temperature of 00 ° C. or more is required, the carbide particles undergo particle growth and cannot be reused as a cemented carbide material.

Japanese Patent Publication No. 56-36692 discloses that a cemented carbide is used in at least one kind of solution selected from ferric chloride, ferric nitrate, and cupric chloride, or a solution thereof. A method is disclosed in which a regenerated powder is obtained by immersing in a solution to which an inorganic acid has been added at a temperature of 80 ° C. or less to elute the Fe, Ni, Co, or Cu binder and pulverizing the residual carbide. Such a means is an effective technique as a regeneration technique that can recover carbide alone, but the binder is difficult to elute and the recovery rate is low, and even though the binder is removed, the strength of the residual carbide is significantly reduced. Since it is not ground, it is difficult to pulverize and cannot be used as it is as a raw material for cemented carbide.

Further, US Pat. No. 3,595,484 discloses a method of treating a cemented carbide in molten zinc, recovering the zinc by distillation under reduced pressure, and pulverizing the residual cemented carbide composition to powder. Is disclosed. However, such means have problems such as growth of carbide particles and residual zinc used as in the above-mentioned JP-B-44-27457, and cannot be reused as a cemented carbide material.

[0006] In addition, Japanese Patent Publication No. 38-4052 discloses that a cemented carbide is reacted with chlorine gas to volatilize metal carbides and binding metals as chlorides. The method is disclosed in JP-A-51-37.
No. 020 discloses that a cemented carbide that has been heated and oxidized in an oxidizing atmosphere is pulverized, then subjected to a reduction treatment and purified and separated.
Methods for recovering the constituent metals are disclosed, but all of these methods are expensive and not economical.

[0007]

As described above, various methods have been conventionally proposed. However, all of them have problems in the recovery quality and processing cost, and it is considered that sufficient results have been obtained at present. It is hard to say that it is only used as a part of spike tires and high-speed steel supplementary materials. That is, in the conventional regenerating method, there is a problem in particle growth of the regenerated metal carbide powder, mixing of impurities during the regenerating, and further, sintering characteristics and the like.
It is difficult to reuse as a raw material for cemented carbide, and at present it has not been put to practical use.

[0008] Accordingly, the present invention provides a superconducting material comprising at least one or more of carbides of metals belonging to Group IVa, Va and VIa of the periodic table and a binder comprising at least one or more of Fe, Ni and Co. Carbide and binder can be recovered and reclaimed independently at low cost and easily from hard alloy scrap, and in particular, raw material powder such as tungsten carbide is free from particle growth and impurity contamination, It is an object of the present invention to provide a method for regenerating a cemented carbide which is reclaimed so that it can be reused as raw material powder.

[0009]

In order to solve the above-mentioned problems, the present invention fills a cemented carbide together with an acidic aqueous solution in a heat-resistant pressure vessel and performs a hydrothermal treatment to reduce the binder in the cemented carbide. After being dissolved in an acidic aqueous solution and collected, and the hydroxide obtained by adding an alkali to the acidic aqueous solution in which the binder is dissolved is calcined to form an oxide, the hydrogen is reduced to convert the binder into a metal. Provide a means to regenerate.

[0010] Further, the cemented carbide is filled in a heat resistant pressure vessel together with an acidic aqueous solution, and a hydrothermal treatment is performed to dissolve and remove the binder in the cemented carbide in the acidic aqueous solution. A means for recovering as a raw material powder of a cemented carbide by heat-treating in a non-oxidizing atmosphere, quenching, and further pulverizing into powder. The means for setting the heat treatment temperature of the residual carbide in the range of 500 to 1600 ° C., the means for forming the non-oxidizing atmosphere by filling the non-reactive gas with the non-reactive gas in the heating furnace, the method for forming the non-reactive gas The present invention provides a means selected from helium gas, argon gas, or neon gas, and a means for rapidly cooling the heat-treated residual carbide to a temperature difference of 500 ° C. or more and 100 ° C. or less.

Further, the means for adjusting the pH of the acidic aqueous solution to 2 or less and the conditions of the hydrothermal treatment are as follows.
Means in the range of 00 ° C., the cemented carbide is IVa of the periodic table,
A means is provided in which at least one of carbides of Va and VIa group metals is a main component, and at least one of iron, nickel and cobalt is a binder.

Since the cemented carbide has a very narrow binder phase between carbide particles, it is extremely difficult to completely dissolve the binder phase at normal temperature and normal pressure. According to the regeneration method, the cemented carbide scrap is filled in a heat-resistant pressure vessel together with an acidic aqueous solution, and by performing a hydrothermal treatment, Co and the like as a binder are completely and quickly converted into an acidic aqueous solution. It can be dissolved and recovered. On the other hand, the residual carbide obtained by eluting the binder becomes porous due to dissolution of the binder phase, and the strength can be reduced as compared with before the treatment. However, it still has the strength considered to be due to the bond between the carbide particles, and it is difficult to easily pulverize as it is, so after heating the obtained residual carbide in a non-oxidizing atmosphere, By quenching, the strength is remarkably reduced, and pulverization can be easily performed. In addition, the powdered material has excellent sintering characteristics without particle growth and contamination of impurities, so it is super hard as it is. It can be reused as alloy powder.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific embodiment of a method for regenerating a cemented carbide according to the present invention will be described. In the present invention, the cemented carbide scrap is filled into a heat-resistant pressure vessel together with an acidic aqueous solution, and the binder in the cemented carbide scrap is dissolved and recovered in the acidic aqueous solution by performing hydrothermal treatment. It is characterized in that after heating the obtained residual carbide in a non-oxidizing atmosphere, it is rapidly cooled, further pulverized and powdered to recover as a raw material powder of a cemented carbide.

First, in order to dissolve and extract the binder in the scrap of the cemented carbide, at least one of the carbides of metals from Group IVa, Va, and VIa of the periodic table such as WC, TiC, and TaC is used. Fe, Ni and Co
Of cemented carbide in a scrap of cemented carbide by filling a sealed heat-resistant pressure vessel together with an acidic aqueous solution together with a scrap of cemented carbide having at least one of them as a binder. Is dissolved, and only the carbide is obtained as a solid.

A method for eluting a binder in a cemented carbide with an acid is described in Japanese Patent Publication No. 56-36692 or a document (Industrial Rare Metal, No. 77, 1982, P110). Since the binder phase between the carbide particles is very narrow, it is extremely difficult to completely dissolve the binder phase at normal temperature and normal pressure.

Therefore, in the present invention, the binder is dissolved completely and drastically in a short time by dissolving the binder phase with an acid under hydrothermal conditions. The acidic aqueous solution used in the present invention may have any pH as long as it is 2 or less, and is not particularly limited. However, an acid having a strong oxidizing action, for example, an acid such as HNO ₃ oxidizes the metal carbide and cannot be reused as a cemented carbide powder as it is, which is not preferable.

The temperature of the hydrothermal treatment is set so that the temperature inside the heat-resistant pressure vessel is in the range of 100 to 300 ° C. Hydrothermal treatment temperature is 100
It is difficult to completely elute the binder within a realistic processing time below ℃ C, that is, outside the hydrothermal condition, and special heat resistance excellent in acid resistance and pressure resistance when the hydrothermal treatment temperature is more than 300 ℃ Pressure vessel is required, and the equipment cost becomes too expensive, which is not practical. Preferably, if the temperature is 250 ° C. or lower, a Teflon container excellent in acid resistance and easy to handle can be used. The heat-resistant pressure vessel has excellent acid resistance as described above, and
Any material may be used as long as it is easy to handle, and there is no particular limitation.

The hydrothermal treatment time, that is, the time required to elute the binder in the scrap of the cemented carbide depends on the pH of the acidic aqueous solution and the treatment temperature. Hydrothermal treatment time is pH
Is lower, that is, as the acidic aqueous solution used is a stronger acid,
Also, the shorter the concentration of the acidic aqueous solution or the higher the processing temperature, the shorter the time.

Next, in order to recover the binder such as Co eluted in the acidic aqueous solution, an alkali such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) is added to the acidic aqueous solution in which the binder is dissolved by hydrothermal treatment. Then, the hydroxide is calcined to form an oxide, and then hydrogen is reduced to regenerate the binder as a metal. The recycled binder can be reused as it is for cemented carbide binders and other uses.

The binder is regenerated as a metal by the regenerating process of dissolving and recovering the binder in the acidic aqueous solution by the above-mentioned hydrothermal treatment, and only the carbide from which the binder is removed from the cemented carbide scrap is solidified. Can be obtained as The obtained residual carbide has become porous due to the dissolution of the binder phase, and although there is a decrease in strength as compared to before the hydrothermal treatment, it still has a strength considered to be due to the bonding between the carbide particles. However, it is difficult to easily pulverize as it is.

Therefore, in order to drastically reduce the strength of the residual carbonized material and easily make it into a fine powder by an ordinary pulverizing method, the porous carbonized residual carbonized material is removed under a non-oxidizing atmosphere. After heating in a heating furnace to raise the temperature, rapid cooling is performed. This is because the expansion by heating and the shrinkage by rapid cooling cause distortion of the porous residual carbide, and break the bond between the carbide particles to drastically reduce the strength of the carbide.

The greater the temperature difference between the heating and the quenching, the greater the decrease in the strength of the residual carbide, and the easier the pulverization. Therefore, the higher the temperature of the heat treatment, the larger the temperature difference during quenching becomes, which is preferable. However, when the temperature is raised to 1800 ° C. or more, carbides grow as in the case of Japanese Patent Publication No. 44-27457. However, it deteriorates the quality of the cemented carbide raw material, and is not preferable for reusing the obtained regenerated powder as a cemented carbide.

Therefore, in the present invention, 50
After heat treatment in a temperature range of 0 to 1600 ° C., 500 ° C.
The quenching is performed to the temperature difference and the temperature of 100 ° C. or less. According to this treatment, the residual carbide can be easily pulverized, and the carbide particles do not grow, and the regenerated powder can be reused as a cemented carbide material. 5
As a result of conducting a detailed test at 00 to 1600 ° C., in this temperature range, almost no carbide grain growth is recognized, and the quality of the cemented carbide material does not deteriorate.
Further, the temperature difference due to rapid cooling needs to be 500 ° C. or more, and if it is less than 500 ° C., the effect of breaking the bond between carbide particles is insufficient.

The quenching method is a method in which the heat-treated high-temperature residual carbide is brought into contact with a low-temperature substance such as liquid nitrogen to quench rapidly, and is not particularly limited as long as it can be quenched. The heating furnace is not particularly limited as long as it can be adjusted to a temperature of 500 to 1600 ° C., and any heating furnace may be used.

The use of a non-oxidizing atmosphere during heating is necessary to prevent the oxidation of carbides, and a gas that is non-reactive with residual carbides such as WC, such as helium (He) gas, is placed in the heating furnace. , Argon (Ar) gas, neon (N
e) It can be produced by a method of filling an inert gas such as a gas or a method of covering a carbide to be heat-treated with carbon.

Since the strength of the above-described heated and quenched porous carbonized residue is significantly reduced, the reduced-residue carbonized residue is pulverized using a crusher or the like.
Further, the powder is pulverized using a ball mill and recovered as a raw material powder of a cemented carbide. When the temperature difference between heating and quenching is set large, it is also possible to pulverize using only a ball mill without crushing by a crusher.

[0027]

【Example】

<< Example 1 >> A cemented carbide chip (Co) having WC as a hard phase and Co as a binder phase was placed in an autoclave having an internal volume of 10 l.
Content of 5%), a total weight of 1 kg, and HCl of a concentration of 10 mol / l were charged until reaching 80% of the space occupied by the autoclave main body, sealed and heated, and the temperature in the autoclave was 200 ° C. and the pressure was 15 kg. / C
After the hydrothermal treatment was performed for 15 hours while maintaining the pressure at m ² , the mixture was cooled and opened, and the residual carbide and the HCl solution in which Co was dissolved were taken out. NaOH was added to the HCl solution in which Co was dissolved to recover Co (OH) ₂ , which was calcined and then reduced with hydrogen to obtain metal Co.

The residual carbide is heated at 900 ° C. in a heating furnace filled with Ar gas, and then subjected to liquid nitrogen (−197
° C) and quenched. Next, the sufficiently cooled carbide was pulverized using a crusher, and further pulverized by a ball mill for 24 hours.

The obtained carbide is a fine powder of about 1 μm in which no particle growth is observed when heated at 1800 ° C. or more.
₂ 0.09%, WC residue, Co in the binder is almost completely dissolved and removed, and it can be reused as a cemented carbide material. The WC recovery was 99%.

Example 2 In a 10-liter autoclave, scraps of cemented carbide chips (Co content 6%) mainly composed of WC-TiC-TaC and Co as a binder were used in a total weight of 1 kg and a concentration of 5 mol. / L of H ₂ SO ₄ was filled up to 80% of the space occupied by the autoclave body, sealed and heated, and the autoclave was heated to a temperature of 2%.
After a hydrothermal treatment for 24 hours at 40 ° C. and a pressure of 33 kg / cm ² , the mixture was cooled and opened to remove the residual carbide and C
The H ₂ SO ₄ solution in which o was dissolved was taken out.

NaOH was added to the H ₂ SO ₄ solution in which Co was dissolved to recover Co (OH) ₂ , which was calcined and then hydrogen reduced to obtain metal Co.

The residual carbide is heated at 900 ° C. in a heating furnace filled with Ar gas, and then subjected to liquid nitrogen (−197
° C) and quenched. Next, the sufficiently cooled carbide was pulverized using a crusher, and further pulverized by a ball mill for 24 hours.

The obtained carbide is a fine powder of about 1 μm in which no particle growth is observed when heated at 1800 ° C. or more.
₂ 0.10%, WC-TiC-TaC residue, Co is almost completely removed from the binder, and can be reused as a cemented carbide material. The WC-TiC-TaC recovery was 98%.

<< Comparative Example 1 >> Scrap of cemented carbide chips was performed under the same conditions and in the same manner as described in Example 1, except that the temperature in the pressure vessel was 90 ° C. and the processing time was 24 hours. Was. As a result of examining the Co content in the obtained residual carbide and the liquid phase, the Co extraction rate was 29.7%. After heating and quenching the obtained residual carbide in the same manner as in Example 1, an attempt was made to grind it with a crusher and a ball mill, but it was difficult to easily pulverize it.

As shown in Comparative Example 1, unless a hydrothermal treatment at a temperature of 100 ° C. or higher is performed, a binder such as Co is not sufficiently dissolved in an acidic aqueous solution, and the residual carbide from which the binder is not sufficiently removed is heated. It can be seen that the strength cannot be reduced even by rapid cooling. On the other hand, according to the cemented carbide regenerating method according to the present invention shown in Example 1, the binder such as Co can be almost completely removed by hydrothermal treatment, the binder can be recovered, and the residual carbide is heated and quenched. By doing so, it can be easily crushed.

<< Comparative Example 2 >> The residue obtained by extracting Co obtained in Example 1 was directly pulverized without heating and quenching, but it was difficult to easily pulverize it.

As shown in Comparative Example 2, the residual carbide from which only the binder such as Co had been removed was porous and had a lower strength than before the hydrothermal treatment. Has the strength that seems to be due to
It turns out that it is difficult to easily pulverize as it is. On the other hand, according to the method for regenerating a cemented carbide according to the present invention shown in Example 1, the strength of the residual carbide is significantly reduced by heating and quenching, so that it can be easily pulverized and obtained. The carbide thus obtained is a fine powder of about 1 μm in which no grain growth is observed when heated at 1800 ° C. or more, and can be reused as a raw material of cemented carbide as it is.

[0038]

As described above in detail, according to the method for regenerating a cemented carbide according to the present invention, Co or the like as a binder is completely and rapidly dissolved and recovered in an acidic aqueous solution. be able to. On the other hand, a raw material powder such as tungsten carbide can be regenerated from the residual carbide obtained by eluting the binder without particle growth or contamination of impurities, and can be reused as a raw material powder of a cemented carbide as it is. In addition, the operation process is relatively simple, and the regeneration process can be performed easily at low cost.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshitaka Yamashita 1-15-2, Minami Harimaya-cho, Kochi City, Kochi Prefecture (72) Inventor Nakamichi 107, Kogawa, Sagawa-cho, Takaoka-gun, Kochi Prefecture

Claims (10)

[Claims] 1. A cemented carbide characterized by filling a cemented carbide together with an acidic aqueous solution into a heat-resistant pressure vessel and performing a hydrothermal treatment to dissolve and recover the binder in the cemented carbide in the acidic aqueous solution. Alloy recycling method. 2. The method according to claim 1, wherein the hydroxide obtained by adding an alkali to the acidic aqueous solution in which the binder is dissolved is calcined to form an oxide, and then subjected to hydrogen reduction to regenerate the binder as a metal. Recycling method of cemented carbide. 3. A cemented hard alloy is charged together with an acidic aqueous solution into a heat-resistant pressure vessel, and a hydrothermal treatment is performed to dissolve and remove the binder in the cemented carbide in the acidic aqueous solution. A method for regenerating a cemented carbide, which comprises subjecting the mixture to a heat treatment in a non-oxidizing atmosphere, quenching, further pulverizing the mixture, and pulverizing the mixture to obtain raw material powder for the cemented carbide. 4. The heat treatment temperature of the residual carbide is 500 to 1
The method for reclaiming cemented carbide according to claim 3, wherein the temperature is in the range of 600 ° C. 5. The method for reclaiming cemented carbide according to claim 4, wherein the non-oxidizing atmosphere is formed by filling a non-reactive gas with a non-reactive gas in a heating furnace. 6. The method according to claim 5, wherein the non-reactive gas is selected from helium gas, argon gas and neon gas. 7. The method according to claim 4, wherein the quenching of the heat-treated residual carbide is quenched to a temperature difference of 500 ° C. or more and 100 ° C. or less. 8. The method for reclaiming cemented carbide according to claim 1, wherein the pH of the acidic aqueous solution is 2 or less. 9. The hydrothermal treatment condition is in a temperature range of 100 to 300 ° C. in the heat-resistant pressure vessel.
The method for reclaiming a cemented carbide according to 5, 6, 7 or 8. 10. The cemented carbide mainly comprises at least one or more of carbides of metals of groups IVa, Va and VIa of the periodic table, and at least one or more of iron, nickel and cobalt as a binder. Claims 1, 2, 3, 4, 5,
10. The method for reclaiming a cemented carbide according to 6, 7, 8 or 9.