JP3290929B2 - Recycling treatment of cemented carbide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of recovering and regenerating a raw material powder from a cemented carbide scrap. In particular, a raw material powder such as tungsten carbide is used as a raw material powder of a cemented carbide without particle growth or contamination of impurities. The present invention relates to a method for regenerating a cemented carbide that can be recycled as it is.

[0002]

2. Description of the Related Art A cemented carbide is a super-hard alloy obtained by blending a metal carbide powder and a metal powder and sintering the mixture. The cemented carbide is mainly produced using a transition element series metal carbide and an iron group metal. That is, tungsten carbide (WC), titanium carbide (Ti
C), IVa, V of the periodic table such as tantalum carbide (TaC)
a hard phase mainly composed of at least one of carbides of Group a and VIa metals, iron (Fe), nickel (Ni)
And a binder phase composed of at least one of cobalt (Co) and WC-Co, WC
-TiC-Co system and WC-TiC-TaC-Co system are widely used. Since this 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.

[0003] Recently, various recycling attempts have been made in various fields of the industry as an environmental measure. Tungsten (W), a main material of carbide tools, which accounts for almost half of machine tools, is entirely imported. And it is a rare resource and very expensive. Therefore, many methods of recovering carbides such as WC, TiC, and TaC from cemented carbide scrap have been proposed.

[0004] For example, Japanese Patent Publication No. 44-27457 discloses a method for reusing scrap of a cemented carbide tool, in which scrap of cemented carbide is covered with carbon, and the scrap is scrapped from 1800 to 2300.
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 high temperature of 00 ° C. or more is required, 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 a binder in a solution containing an inorganic acid at a temperature of 80 ° C. or lower to elute the Fe, Ni, Co, or Cu binder, and then pulverizing the residual carbide. . Such a means is an effective technique as a regeneration technique that can recover carbide alone, but the recovery rate is low because the binder phase is difficult to elute, and the strength of the residual carbide decreases significantly even though the binder phase is removed. Therefore, it is difficult to pulverize and cannot be directly used 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.

[0007] 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-51-370.
No. 20 discloses a method in which a cemented carbide oxidized by heating and oxidizing in an oxidizing atmosphere is pulverized, then subjected to a reduction treatment, purified and separated, and a constituent metal is recovered. It is disadvantageous in terms of cost.

[0008]

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 difficult to say that the recovered metal cannot be used for high-grade tools due to its low quality, and is used only as a part of auxiliary materials of spiked tires and high-speed steel for limited applications. That is, in the conventional regeneration treatment method, there is a problem in the particle growth of the regenerated metal carbide powder, the mixing of impurities during the regeneration, and the sintering characteristics and the like, and it is difficult to reuse the material as a raw material of the cemented carbide. At present it has hardly been put to practical use.

Accordingly, the present invention provides a method of controlling the periodic table to include I Va, Va
And a cemented carbide scrap containing at least one or more of carbides of Group VIa metals such as W, Ti and Ta as a hard phase and at least one or more of Fe, Ni and Co as a binder phase. Recovering and regenerating a phase alone, especially a method for regenerating a cemented carbide that recycles a material powder such as tungsten carbide so that it can be reused as a material powder for cemented carbide without particle growth or contamination of impurities The task is to provide

[0010]

In order to solve the above-mentioned problems, the present invention provides a porous carbonaceous carbide obtained by removing a binder from a cemented carbide, containing an aqueous solution in its pores. Rapidly cooling in a state, freezing the aqueous solution, causing a phase change by expanding the volume and rapidly expanding the volume, thereby destroying the connective structure of the residual carbide, and filling the cemented carbide together with the acidic aqueous solution into a heat resistant pressure vessel, After the binder in the cemented carbide is dissolved in an acidic aqueous solution and removed by performing a heat treatment, the obtained porous carbonized residue is quenched in a state where the aqueous solution is contained in the pores, and the aqueous solution is cooled. Provides a means for destroying the connective structure of residual carbides by causing a phase change by freezing and rapidly expanding the volume.

Further, the acidic condition of the acidic aqueous solution is pH 2
Means using the following acidic aqueous solution and means for setting the processing temperature in the hydrothermal treatment to 100 ° C. to 300 ° C. are provided. Further, the residual carbonaceous substance in a porous state in which the aqueous solution is contained in the pores is subjected to ultrasonic treatment in an aqueous solution, so that the inner surface of the pores is brittle or the aqueous solution is further penetrated into the pores and then the aqueous solution is frozen. Means, means comprising adding a surfactant to an aqueous solution,
A means for repeatedly performing a predetermined number of times of rapid expansion of a volume by freezing an aqueous solution to cause a phase change, a means for using water, an acidic aqueous solution, or an aqueous ammonia solution as an aqueous solution, and a means for using liquid nitrogen as a freezing means are provided.

A means for recovering the raw material powder of the cemented carbide by crushing by mechanical means and pulverizing it after breaking the connecting structure of the residual carbide. A means is provided in which at least one or more of carbides of Va and Group VIa metals are used as a main component and at least one or more of iron, nickel and cobalt are used as 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. By filling in a heat-resistant pressure vessel and performing hydrothermal treatment, Co and the like as a binder can be completely and quickly dissolved in an acidic aqueous solution and recovered. And the residual carbide from which the binder has been removed is in the form of a porous body, and although the strength is lower than that of the cemented carbide, it still has the strength considered to be due to the bonding between the carbide particles, It is difficult to easily pulverize as it is. Therefore, by the regeneration treatment method according to the present invention, by rapidly cooling in a state of containing the aqueous solution in the pores of the porous residual carbide, the aqueous solution is frozen and the phase is changed to rapidly expand the volume, The connective structure of the residual carbide can be destroyed. Thereafter, the powder is pulverized by a mechanical means and pulverized into fine powder, whereby the powder can be easily recovered as a raw material powder of a cemented carbide.
It is excellent in sintering characteristics without particle growth and impurity contamination observed in high-temperature heat treatment at a temperature of not less than ℃, and can be reused as raw material powder of cemented carbide as it is.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific embodiment of a method for reprocessing a cemented carbide according to the present invention will be described. In the present invention, after filling the scrap of cemented carbide in a heat-resistant pressure vessel together with the acidic aqueous solution, and dissolving the binder in the cemented carbide in the acidic aqueous solution by performing hydrothermal treatment,
The obtained porous carbonized residue is rapidly cooled in a state of containing an aqueous solution in its pores, and the aqueous solution is frozen to cause a phase change to rapidly expand the volume, thereby destroying a connective structure of the residual carbonized material. After that, the basic means is to pulverize and pulverize by mechanical means to recover the raw material powder of the cemented carbide.

First, in order to dissolve and remove the binder phase in the scrap of the cemented carbide, at least one of carbides of metals belonging to Group IVa, Va and VIa of the periodic table such as WC, TiC and TaC is used. Mainly, scrap of cemented carbide containing at least one of Fe, Ni and Co as a binder together with an acidic aqueous solution is filled in a sealed heat-resistant pressure vessel to perform hydrothermal treatment. By the hydrothermal treatment using this acidic aqueous solution, the binder phase in the scrap of the cemented carbide is dissolved and removed in the acidic aqueous solution to obtain a porous residual carbide.

A method for eluting a binder phase 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. Thus, by dissolving the binder phase with an acid under hydrothermal conditions, the binder phase can be completely eluted in a short time. 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 it is as a cemented carbide powder.

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 phase within a realistic processing time below the temperature of ℃, that is, outside the hydrothermal condition, and special heat resistance excellent in acid resistance and pressure resistance when the hydrothermal treatment temperature is 300 ℃ or more A pressure vessel is required and the equipment cost becomes too expensive, which is not practical. If the temperature is preferably 250 ° C. or lower, a Teflon container excellent in acid resistance and easy to handle can be used.

As a heat-resistant pressure vessel, it has excellent acid resistance,
In addition, 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 phase of the cemented carbide scrap slightly varies depending on the treatment temperature. That is, the hydrothermal treatment time is reduced as the pH is lower, that is, as the acidic aqueous solution used is a stronger acid, or as the concentration is higher, or as the treatment temperature is higher.

By the above hydrothermal treatment, the binder phase is dissolved and removed from the cemented carbide scrap in the acidic aqueous solution, and a porous residual carbide is obtained. At the end of the hydrothermal treatment, the pores of the residual carbide are filled with an acidic aqueous solution. Although the strength of the porous carbide is lower than that before the hydrothermal treatment, it has strength due to the bonding between the carbide particles, and it is difficult to easily pulverize as it is.

In order to reduce the strength of the obtained porous residual carbonized material and to easily make it into a fine powder by a usual pulverizing method, the porous material containing an aqueous solution in the pores is used. The residue-like carbide is rapidly cooled to freeze the aqueous solution in the pores, and the aqueous solution is changed into ice.

As the aqueous solution to be filled into the pores of the residual carbide, water is suitable. No special restrictions or treatments are required for the water used. In addition to water, any material may be used as long as its volume expands due to a phase change due to freezing. Specifically, an aqueous ammonia solution can be used, and when an aqueous ammonia solution is used, the rapid expansion rate of the volume caused by the phase change can be increased. Note that the aqueous ammonia solution may have any concentration. Further, the acidic aqueous solution used for the hydrothermal treatment for dissolving and removing the binding layer can be used as it is.

The pores of the residual carbide after the hydrothermal treatment are filled with an acidic aqueous solution. When an acidic aqueous solution is used as an aqueous solution to be contained in the pores, the freezing treatment is performed as it is. Just do it. When water or aqueous ammonia is used as the aqueous solution, the residual carbonized material after the hydrothermal treatment is thoroughly washed with water to remove the acidic aqueous solution from the pores, or washed well with water to remove the acidic aqueous solution from the pores. After removing the aqueous solution and drying, it may be immersed in water or an aqueous ammonia solution or the like to fill the pores with the aqueous or ammonia aqueous solution or the like.

The quenching method is carried out by bringing the residual carbide containing an aqueous solution into the pores into contact with an ultra-low temperature substance such as liquid nitrogen. The quenching method is not particularly limited as long as the phase of the aqueous solution can be changed to ice. In particular, the lower the minimum temperature of the quenching, the better. Further, it is preferable that the quenching treatment is repeatedly performed.

As described above, when the aqueous solution in the pores of the porous residual carbide is rapidly frozen, the aqueous solution undergoes a phase change to ice as a solid, and the volume rapidly expands due to this phase change, and the residual carbon is removed. In order to destroy the connective structure between the carbide particles, the strength of the carbide rapidly decreases.

Further, not only the quenching of the porous residual carbon material containing the aqueous solution in the pores, but also the inner surface of the pores becomes more brittle, or after the hydrothermal treatment in order to further penetrate the aqueous solution into the pores, it becomes finer. A method of rapidly freezing after ultrasonic treatment while containing an aqueous solution in the pore, a method of rapidly freezing after penetrating an aqueous solution containing a surfactant after hydrothermal treatment, and a method of hydrothermal treatment It is also possible to use a method in which an aqueous solution to which a surfactant is added later is permeated into the pores, then subjected to ultrasonic treatment, and then rapidly frozen.

For the ultrasonic treatment, a usual ultrasonic cleaning device or the like may be used. Further, any surfactant can be used as long as it allows an aqueous solution to penetrate into the pores. Specifically, carboxylate, sulfonate, sulfate ester salt, phosphate ester salt, aliphatic amine salt, aliphatic quaternary ammonium salt and the like can be used.

The ultrasonic treatment has a function of permeating the aqueous solution into the pores because the connecting structure between the carbides becomes brittle, and the same effect can be obtained with an aqueous solution to which a surfactant is added. Further, by adding a surfactant to the aqueous solution and then performing ultrasonic treatment, the destruction effect of connective tissue is increased,
The strength between the porous residual carbides can be effectively reduced.

The aqueous solution is rapidly frozen by the above-mentioned various methods, subjected to easy pulverization treatment, and thereafter, the residual carbide in a porous material is pulverized into fine powder by a mechanical pulverizing means, whereby the raw material powder of the cemented carbide is obtained. To be collected. As the mechanical pulverizing means, a hammer mill, a ball mill, a jet mill, or the like is used.

On the other hand, an alkali such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) is added to the acidic aqueous solution in which the binder phase is dissolved by the hydrothermal treatment to form a hydroxide. After that, the binder phase can be regenerated as a metal by performing hydrogen reduction or the like. The regenerated binder phase can be reused as it is for cemented carbide binders and other uses.

[0030]

【Example】

<< Example 1 >> In an autoclave having an inner volume of 10 liters, a cemented carbide chip having WC as a hard phase and Co as a binder phase (manufactured by Toshiba Tungaloy Co., Ltd .: TH-10, Co content 4 to 7%) was used. The scrap was filled with a total weight of 1 kg, and HCl (hydrochloric acid) having a concentration of 10 mol / l as an acidic aqueous solution 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 200 ° C and a pressure of 15 kgf. / Cm ²
After hydrothermal treatment for 15 hours, open after cooling
A porous residual carbon material eluted with Co of the binder phase and an HCl solution in which Co was dissolved were taken out.

FIG. 1 is an electron micrograph (× 5000) showing the metal structure of the cemented carbide chip before hydrothermal treatment in Example 1,
FIG. 4 is a graph showing the pore distribution, FIG. 2 is an electron micrograph (× 5000) showing the metal structure of the porous residual carbide after hydrothermal treatment, and FIG. 5 is a graph showing the pore distribution. is there. 4 and FIG. 5 and the graph of FIG. 6 described below, the horizontal axis represents the pore diameter (Å), and the vertical axis represents the total pore volume (cc / cc).
g) and differential pore volume (cc / g · logｌｏ). As shown in the electron micrograph, FIG. 2 in which Co of the binder phase was dissolved and removed as compared to before the hydrothermal treatment showed that it was more porous than in FIG. 1 and that the carbides were still strongly bonded. It turns out that there is. By dissolving and removing Co of the binder phase by the acidic hydrothermal treatment in this manner, the obtained residual carbide is in the form of a porous body. This is because the fine carbide particles before hydrothermal treatment shown in the graph of FIG. While pores are hardly recognized in the pore distribution, the residual carbide which is an acid hydrothermally treated product shown in the graph of FIG.
9 cc / g and increased significantly, yet has been demonstrated by a sharp peak is observed in the pore diameter 10 ³ Å around even differential pore volume. In FIG. 4 showing the pore distribution of the untreated cemented carbide tip, the pore diameter is 10 ⁵ to 10 ⁵ .
Small changes in broad near 10 ⁶ Å is observed, the total pore volume shows a substantially 0.002cc / g, which is considered a measure of the unevenness of the cemented carbide chip surface.

Next, the obtained porous residual carbonized material is sufficiently washed with water, and in a stainless steel container containing 5 liters of liquid nitrogen (−197 ° C.) while keeping water in the pores. And quenched to freeze the water in the pores. In addition, out of the chip-shaped residual carbides that were injected,
Approximately 40% had cracked chips or chipped corners, and about 60% retained their original shape.

FIG. 3 is an electron micrograph (× 5000) showing the metal structure of the residual carbide after the quenching treatment, and FIG. 6 is a graph showing the pore distribution thereof. As shown in the micrograph of FIG. 3, the rapid freezing treatment makes the porous body more porous than that of FIG. 2 after the hydrothermal treatment, and the bond between the carbides is broken. As shown in the graph of FIG. 6, the fact that the porous residual carbonized material obtained by the acidic hydrothermal treatment was turned into a porous material having a larger diameter and a larger total pore volume by the quenching treatment as shown in FIG. 0.023 total pore volume
cc / g, which is much larger than the total pore volume of 0.009 cc / g of the acidic hydrothermally treated product shown in FIG. 5, and also in the differential pore volume, in addition to the pore diameter of around 10 ³ mm,
This is demonstrated by the fact that a sharp peak is observed near the pore diameter of 10 ⁴ °.

Thereafter, the porous carbonized residue after the quenching treatment was coarsely crushed by a crusher and then finely pulverized by a jet mill. The carbide obtained by pulverization has a particle size of 10 ⁴ Å (1 μm).
m) The following is a fine powder of about 50%, and the result of composition analysis shows that the content of Co is 0.01% or less, the content of O ₂ is 0.09% and WC residue, and the Co of the binder phase is almost dissolved and removed. And could be reused as a cemented carbide material. W
The C recovery rate is 99% or more.

On the other hand, the HCl solution in which Co is dissolved is NaO
H was added to recover Co (OH) ₂ , which was fired and then reduced with hydrogen to obtain metal Co.

Example 2 A cemented carbide chip containing WC-TiC-TaC as a main component and Co as a binder (manufactured by Toshiba Tungaloy Co., Ltd .: UX-30, Co content) was placed in an autoclave having an internal volume of 10 liters. 6 to 12%) of scrap with a total weight of 1 kg and a concentration of 5 mol as an acidic aqueous solution.
1 / liter of H ₂ SO ₄ was filled until the space occupied by the autoclave reached 80% of the space occupied by the autoclave, sealed and heated, and the autoclave temperature was 240 ° C. and the pressure was 33 kgf /.
After performing a hydrothermal treatment for 12 hours while maintaining the pressure at ² cm ² , the mixture was cooled and opened, and the residual carbonaceous carbide having eluted Co of the binder phase and Co were dissolved to take out the H ₂ SO ₄ solution. .

The pore distribution of the residual carbide obtained by the hydrothermal treatment using H ₂ SO ₄ in Example 2 is the pore distribution of the porous carbide obtained by the hydrothermal treatment using HCl in Example 1. This is almost the same as that of Example 1. It can be seen that the residual carbide obtained by the hydrothermal treatment using H ₂ SO ₄ of Example 2 is also porous.

After sufficiently washing the porous carbon residue, it is poured into a stainless steel container containing 5 liters of liquid nitrogen (−197 ° C.) while keeping water in the pores. Quenched to freeze the water in the pores. In addition, about 40% of the chip-shaped carbides charged in the same manner as in Example 1 had cracked chips or chipped corners, and about 60% retained the original shape.

The pore distribution of the residual carbide obtained by the quenching treatment of Example 2 is almost the same as the pore distribution of the residual carbide obtained by the quenching treatment of Example 1. It can be seen that, by the quenching treatment in the same manner as in Example 1, the obtained porous residual carbonized material is further porous. Next, this sufficiently cooled porous carbide was crushed and pulverized in the same manner as in Example 1.

The porous carbide obtained by the pulverization is a fine powder having a particle size of 10 ⁴ １０ (1 μm) or less and about 50%.
As a result of composition analysis Co 0.01% is less, O ₂ is 0.10% and WC-TiC-TaC residue, Co binder phase is almost dissolved and removed, re as cemented carbide material Available. In addition, WC-TiC-TaC
The recovery was 98% or more.

On the other hand, the H ₂ SO ₄ solution in which Co is dissolved is KO
H was added to recover Co (OH) ₂ , which was fired and then reduced with hydrogen to obtain metal Co.

Example 3 Co was dissolved and removed by the hydrothermal treatment obtained in Example 1 and then washed with water to remove 5 l of water from the porous residual carbonized material containing water in the pores. Ultrasonic cleaner (SHARP SILENTS)
ONIC UT-304) and sonicated for 30 minutes, then 5 liters of liquid nitrogen (-197 ° C)
And quenched in a stainless steel container.

Approximately 50 of the injected chip-shaped carbides
The percentage of the chips was broken or the corners of the chips were missing, and about 50% of the originals remained. The same coarse and fine pulverization as in Example 1 was performed on the cooled carbide. Porous shaped carbides obtained in finely divided particle size 10 ⁴ Å (1 [mu]
m) The following was a fine powder of about 60%, and the result of composition analysis was the same as in Example 1.

Example 4 Co was dissolved and removed by the hydrothermal treatment obtained in Example 1 and then washed with water to obtain a porous residual carbon material containing water in the pores as a surfactant. 0.1% sodium dodecylbenzenesulfonate (DB
A) The solution was poured into a stainless steel container containing 5 liters of an aqueous solution, and the container was placed on a shaking table and vibrated for 1 hour.
It was put into a stainless steel container containing 1 liter of liquid nitrogen (−197 ° C.) and quenched.

Approximately 45 of the injected chip-shaped carbides
The percentage was broken or the corner of the chip was chipped, and about 55% of the prototypes remained. The cooled residual carbonized material was subjected to the same coarse and fine grinding as in Example 1. The carbide obtained by pulverization has a particle size of 10 ⁴
Å (1 μm) or less was a fine powder of about 55%, and the result of composition analysis was almost the same as in Example 1.

Example 5 Co was dissolved and removed by the hydrothermal treatment obtained in Example 1 and then washed with water to obtain a porous residual carbide containing water in the pores as a surfactant. 0.1% sodium dodecylbenzenesulfonate (DB
A) The same ultrasonic cleaner as in Example 3 containing 5 liters of an aqueous solution was put therein, and subjected to ultrasonic treatment for 30 minutes.
It was put into a stainless steel container containing 1 liter of liquid nitrogen (−197 ° C.) and quenched. Approximately 55% of the injected chip-shaped carbides have cracked chips or chipped corners, and only about 45% of the original mold remains
Met.

The cooled carbide was crushed and pulverized in the same manner as in Example 1. The porous carbonized material obtained by the fine pulverization was a fine powder having a particle size of not more than 63% (1 ⁴ μm) or less. The result of composition analysis was almost the same as that of Example 1.

Example 6 Co was dissolved and removed by the hydrothermal treatment obtained in Example 1 and then washed with water to remove residual carbon in a porous state containing water in the pores. The quenching treatment shown in FIG. 5 was repeated twice. About 60% of the input chip-shaped carbides were cracked or lacked in edges, and about 40% retained the original form.

The cooled porous carbonized residue was subjected to the same coarse and fine grinding as in Example 1. The carbide obtained by the fine pulverization was a fine powder having a particle size of 10 ⁴ ° (1 μm) or less and about 65%. The result of composition analysis was almost the same as that of Example 1.

<< Comparative Example 1 >> Scrap of cemented carbide chips was performed under the same conditions and methods 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 extraction rate of Co was 2
It was 9.7%, and the obtained residual carbide was quenched in the same manner as in Example 1. In addition, the chipped residual carbide in the shape of the chips had no cracks or chipped corners of the chips, and all remained in the original form.

The same grinding operation as in Example 1 was attempted on the cooled residual carbide, but it was difficult to pulverize it. Therefore, unless a hydrothermal treatment at 100 ° C. or higher is performed as described in this example, the binder phase such as Co is not sufficiently dissolved in the solvent, and the residual carbide in which the binder phase is not sufficiently removed is subjected to a quenching treatment. It can be seen that the strength cannot be significantly reduced.

On the other hand, according to the cemented carbide regeneration treatment method shown in Embodiment 1, the binder phase such as Co can be almost completely removed by the hydrothermal treatment, and the binder phase can be recovered.
By rapidly cooling and freezing the residual carbide, it can be easily pulverized.

Comparative Example 2 Co was dissolved and removed by the hydrothermal treatment obtained in Example 1, and then the porous residual carbide washed with water was sufficiently dried until water was not contained in the pores. After that, the same rapid cooling treatment as in Example 1 was performed. In addition, the chipped residual carbide in the shape of the chips did not crack the chips, and all remained the original form. The pore distribution of the carbide obtained by the quenching treatment of Comparative Example 2 is the same as before the quenching treatment, and the effect of the quenching treatment observed in Example 1 and the like is not observed.

This is because water is not contained in the pores.
This is because there is no rapid expansion of the volume due to the phase change due to the rapid freezing, and the connective structure of the carbide cannot be destroyed. The same grinding operation as in Example 1 was attempted on the cooled carbide, but it was difficult to pulverize the cooled carbide.

Comparative Example 3 Co was dissolved and removed by the hydrothermal treatment obtained in Example 1, and then the porous residual carbide washed with water was subjected to the same crude treatment as in Example 1 without quenching. Crushing and pulverization were attempted, but it was difficult to easily pulverize. The residual carbide obtained only by removing the binder phase such as Co is in a porous state and has a strength considered to be due to the bond between the carbide particles, although the strength is lower than before the hydrothermal treatment. Because.

On the other hand, according to the method for regenerating cemented carbide according to the present invention, the strength of the porous residual carbide is significantly reduced by the rapid cooling / freezing treatment, and it can be easily pulverized. , yet the resulting porous shaped carbides, since there is no heating step at a high temperature, no grain growth as found upon heating at 1800 ° C. or higher, the particle size 10 ⁴ Å
(1 μm) is a fine powder of 50% or more and can be reused as raw material of cemented carbide as it is.

[0057]

As described in detail above, according to the method for reclaiming cemented carbide according to the present invention, the ordinary cemented carbide has a very narrow binder phase between carbide particles, and thus is hardened at normal temperature and normal pressure. Although it is extremely difficult to completely dissolve the binder phase in, a scrap of cemented carbide was filled in a heat-resistant pressure vessel together with a solvent and a solvent was contained in the pores after performing a hydrothermal treatment. By rapidly cooling the aqueous carbide residue in the state and rapidly freezing the aqueous solution, the connective tissue is destroyed by the rapid expansion of the volume due to the phase change of the porous carbide and the strength is significantly reduced, and the pulverization is performed. It can be carried out. Therefore, the raw material powder such as tungsten carbide can be obtained from the porous residual carbide obtained by dissolving the cemented carbide scrap completely and in a short time in a solvent to elute the binder phase without particle growth or contamination of impurities. It can be recycled as raw material powder for cemented carbide as it is.

In particular, the quality of the raw material powders which have been conventionally collected and recovered is higher than that of various methods, and is advantageous in terms of processing cost. W, Ti of Group IVa, Va and VIa group metals of the periodic table And at least one of carbides such as Ta and the like as a hard phase and at least one or more of Fe, Ni and Co as a binder phase. In addition, the raw material powder can be easily regenerated.

[Brief description of the drawings]

FIG. 1 is an electron micrograph showing the metal structure of cemented carbide scrap before hydrothermal treatment.

FIG. 2 is an electron micrograph showing the metal structure of the residual carbide of cemented carbide scrap after hydrothermal treatment.

FIG. 3 is an electron micrograph showing a metal structure of residual carbide of cemented carbide scrap after being subjected to hydrothermal treatment and then cooled and frozen.

FIG. 4 is a graph showing the pore distribution of cemented carbide scrap before hydrothermal treatment.

FIG. 5 is a graph showing a pore distribution of residual carbide in cemented carbide scrap after hydrothermal treatment.

FIG. 6 is a graph showing a pore distribution of residual carbide of cemented carbide scrap after cooling and freezing after hydrothermal treatment.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-108302 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 31/00-31/36 B09B 3 / 00 C22B 7/00 B22F 9/04 INSPEC (DIALOG) JICST file (JOIS)

Claims (11)

(57) [Claims] 1. A porous solid carbide obtained by removing a binder from a cemented carbide is rapidly cooled in a state where an aqueous solution is contained in its pores, and the aqueous solution is frozen to cause a phase change. A method for reclaiming cemented carbide, characterized by destroying the connective structure of the residual carbide by rapidly expanding the volume. 2. A porous material obtained 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 remove the binder in the cemented carbide in the acidic aqueous solution. Quenched in the state of containing an aqueous solution in its pores, and rapidly changing the phase by freezing the aqueous solution to rapidly expand the volume, thereby destroying the connective structure of the residual carbide. Method for reclaiming cemented carbide. 3. The method for reclaiming cemented carbide according to claim 2, wherein an acidic aqueous solution having a pH of 2 or less is used as the acidic condition of the acidic aqueous solution. 4. The treatment temperature in the hydrothermal treatment is from 100 ° C.
The method for reclaiming cemented carbide according to claim 2 or 3, wherein the temperature is set to 300 ° C. 5. A porous carbonaceous residue containing an aqueous solution in the pores is subjected to ultrasonic treatment in an aqueous solution to make the inner surface of the pores brittle or to further penetrate the aqueous solution into the pores before the aqueous solution. 5. The method for reclaiming cemented carbide according to claim 1, 2, 3, or 4. 6. The method for reclaiming cemented carbide according to claim 1, wherein a surfactant is added to the aqueous solution. 7. The method according to claim 1, wherein the rapid expansion of the volume by freezing the aqueous solution and changing the phase is repeated a predetermined number of times.
7. The method for reprocessing a cemented carbide according to 2, 3, 4, 5 or 6. 8. The method according to claim 1, wherein the aqueous solution is water, an acidic aqueous solution, or an aqueous ammonia solution.
8. The method for reclaiming a cemented carbide according to 6 or 7. 9. The method for reclaiming cemented carbide according to claim 1, wherein liquid nitrogen is used as the freezing means. 10. The method of claim 1, wherein after breaking down the connective structure of the residual carbide, the raw material powder of the cemented carbide is recovered by pulverizing by mechanical means and pulverizing it.
The method for reprocessing a cemented carbide according to 2, 3, 4, 5, 6, 7, 8, or 9. 11. A cemented carbide mainly comprises at least one or more of carbides of Group IVa, Va and VIa metals of the periodic table, and at least one or more of iron, nickel and cobalt as a binder. Claims 1, 2, 3, 4, 5,
11. The method for reclaiming cemented carbide according to 6, 7, 8, 9 or 10.