JPH0320445B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for recovering components of hybrid cemented carbide scrap in a reusable form. Conventionally, the following methods of recovering cemented carbide scrap are known, but they also have the drawbacks described therein. (1) Cold stream method This method uses low-temperature brittleness to simply impact crush the material, but since it is not possible to separate each component, it is only valuable as scrap powder, and the cost of the refrigerant is high. (2) High-temperature heating method with carbon addition Because it requires a high temperature of 2000℃, carbide grains grow, so it cannot be used for anything other than scrap powder, and
Energy costs are high because the temperature is over 2000℃. (3) Wet processing method A dissolution method using an acid or salt solution, the reaction rate is slow, the separation process after dissolution is multi-stage, and the yield is poor. (4) Menstrum method Since it decomposes in an iron bath, a high-temperature bath is required, and since iron is eluted with acid, contamination of iron and acid consumption are undesirable. (5) Zn decomposition method It is suitable for processing certain grades of products by using pit rotting of molten zinc, but when processing miscellaneous products, it is limited to scrap powder. (6) Chemical processing method This method involves roasting and wet processing, which is expensive and has a low yield. The present inventors focused on the Zn decomposition method, which is superior to other conventional methods in terms of recovery rate and cost, and conducted research on this method. As a result, it was found that this method had the following drawbacks. (1) Cemented carbide is divided into types based on the particle size of WC, but if WC cannot be separated, it cannot be recovered as a normal product, and when this method is applied to hybrid cemented carbide, WC separation is Since I can't do that, I'll stop at scrap powder. (2) Separation of each component from scrap powder is carried out by wet method, but as the binder phase is increasingly reinforced with alloys and has a contact-resistant composition such as Co-W and Ni-Mo, it can be easily separated using acids, etc. It cannot be dissolved, and there is a lot of solid phase in solid-liquid separation, resulting in loss. (3) As mentioned in (2) above, some of W and Mo are alloyed in the binder phase, and when roasted, CoMoO ₄ ,
Since they combine to form poorly soluble compounds like CoWo ₄ , the recovery rate of W and Mo is low. The present inventors have conducted intensive research to improve the drawbacks of the zinc decomposition method described above and provide a method suitable for scrap recovery of hybrid cemented carbide.
The present invention was achieved based on the following findings. (1) In the zinc decomposition treatment, the non-uniform, non-equilibrium composition of hard scrap is brought to an equilibrium state to facilitate subsequent treatment. That is,
800℃~1000℃ with addition of carbon and molten zinc
By reacting at about 0.degree. C., all carbide-forming elements are converted into carbides and decomposed in molten zinc. (2) After zinc decomposition, heavy metal carbides and binder
Although Co separates into upper and lower phases to some extent due to the difference in specific gravity, neither of them dissolves, so it cannot be separated into two parts if it is cooled as is. Therefore, separation is performed in a molten state using a slight excess of Zn. It is more effective to repeat this operation. (3) After Zn distillation, the spongy recovered material separated into groups takes advantage of its spongy nature and continues the reaction in the next step without being crushed. That is, the WC group performs oxidative roasting, and the Co group performs acid leaching. In the present invention, carbon and molten zinc are added to cemented carbide scrap, carbonization and zinc decomposition are performed, and then zinc is recovered by distillation from each phase separated into an upper and lower phase. From the zinc distillation residue of the upper phase, Co, Ni
This invention relates to a method for recovering hybrid cemented carbide scrap into its respective components, which consists of recovering equibonded metals and oxidizing and roasting the lower phase zinc distillation residue to recover heavy metals. The method of the present invention will be explained in detail with reference to the attached flowchart. Hard scrap [WC, MO ₂ C, TiC, TiN,
Dia ₍ scum), _Cr3C2 , VC, TaC, NbC, _H5C ,
Co, Ni, Fe, Al ₂ O ₃ , Au, Ag] and carbon C
Add molten zinc, Zn, and maintain the temperature above 800℃ to perform zinc decomposition treatment. Au and Ag are derived from the mouth material. At 850°C to 1000°C, in the presence of molten zinc and C, W, Mo, Cr, etc. are easily converted into carbides and arranged into compound groups that can be easily processed later.
Furthermore, molten zinc enters the grain boundaries and drives out bonded metals such as Co and Ni, floating them in the Zn bath, while excess carbon leaves W, Mo, Cr, etc. in the bonding phase as carbides. This reaction occurs when bonding metals such as Co and Ni
This is carried out until TiN, Cr ₃ C ₂ and heavy metal carbide are roughly separated into upper and lower phases. After the Zn decomposition treatment, the molten zinc bath is left standing, and Al ₂ O ₃ , Dia, TiC, TiN, etc. floating on the upper phase of the molten zinc are separated by tapping or scraping. Regarding the remaining phases excluding the upper phase, there is no boundary between the two layers of the heavy metal carbide part and the binder Co part;
Since the two cannot be separated in this state, the upper phase
By repeating the operation of tapping Zn, adding an equivalent amount of Zn, allowing it to react, and tapping, it is separated into an intermediate phase and a lower phase. Zn is distilled and recovered for each of the intermediate and lower phases. Each distillation residue is spongy. The intermediate phase distillation residue contains V, Ti, Zr and Cr.
It contains carbide, Co, Ni, Fe, etc., which is decomposed with sulfuric acid or hydrochloric acid to recover the bound metals as Co(Ni) salt. The lower phase distillation residue contains
It contains Mo ₂ C, WC, TaC, NbC, Au _, Ag, etc. MoO ₃ is recovered by oxidizing and roasting it and sublimating it, and WC is converted to APT (ammonium At the same time, the residue containing ta ₂ O ₅ , Nb ₂ O ₅ , Au, Ag, etc. is decomposed with HF, and further KF is added.
Separate and recover TaF _2.2KF and NbF _5.2KF , and recover Au and Ag from the remainder. Preferred embodiments of the present invention include the following. (1) Fill the Zn condenser to be distilled with the next process to improve Zn recovery rate and efficiency. (2) The furnace for Zn decomposition should be small in diameter, tall and tappable. (3) Add enough Zn to disperse and separate the reactants. Use at least twice the amount by weight. (4) The temperature in the Zn decomposition reaction is kept slightly higher, preferably at 900°C or higher, to facilitate the formation of carbides. The method of the present invention includes cemented carbide scrap processing, powder scrap processing for cemented carbide, cemented carbide polishing, recovery of valuable components from grinding scraps, treatment of cermet scraps, recovery and utilization of valuable components from precious metal contact scraps,
It is used to recover valuable components such as Co and Mo from waste catalysts. Example Carbide scrap (WC80%, Co14%, _Mo2C4
%, TiC2%) 180Kg and 1Kg of carbon, Zn
Add 420 kg of molten metal, keep it at 800℃, and after the intense reaction is complete, leave it to stand for 10 minutes, scrape off the scum floating on the surface, and tap about 1/2 of the molten metal, 200 kg, to separate into a ladle. After adding 200 kg of molten Zn and completing the same reaction, tap it again and dispense it into a ladle. The separated lower phase and ladle were placed in a vacuum chamber for approximately 800 min.
Heat to ℃ and reduce pressure to distill and recover Zn. The distillation residue became sponge-like, and its composition was separated into WC, Mo ₂ C, and Co, as shown in the table below, and Ti was further removed.

【table】

[Table] When the bottom WC portion was oxidized and roasted, it was easily converted into an oxide because it was spongy, and 9.7 kg of MoO ₃ was obtained by volatilization recovery (1200°C). The remaining W is
WO ₃ is converted into APT by NH ₄ OH treatment.
It becomes a high-purity product. The Co portion remaining in the ladle is separated as CoO by oxidative roasting. The overall yield in this process is W98.4%, Mo96.2
%, Co97%.

[Brief explanation of the drawing]

The accompanying drawing is a flowchart illustrating one embodiment of the invention.

Claims (1)

[Claims] 1 Carbon and molten zinc are added to cemented carbide scrap, carbonization and zinc decomposition are carried out, and zinc is recovered by distillation from each phase separated into upper and lower phases. Co, Ni, etc. are extracted from the zinc distillation residue of the upper phase. A method for recovering hybrid cemented carbide scrap into its respective components, which consists of recovering the combined metals and oxidizing and roasting the lower phase zinc distillation residue to recover heavy metals.