Method for producing carbide powder

Abstract

The invention relates to a method for producing a carbide powder from cemented carbide waste, in which cemented carbide waste is subjected to an acid treatment, in which a metal binder is dissolved, thereby forming a carbide residue comprising a carbide skeletal fraction, which is then ground into a carbide powder. The invention also relates to a powder produced according to the method and to a cemented carbide produced using the carbide powder.

Description

[0001] The present invention relates to a method for manufacturing carbide powder from hard alloy waste. The present invention also relates to a carbide powder manufactured according to this process and a hard alloy manufactured from such carbide powder. Background Art

[0002] The recycling of hard alloys has been known for a long time, and several processes are used in the art for recycling. One of the most common processes is the Zn process, in which the Co binder in the hard alloy waste is dissolved in molten Zn, and the Zn is removed by distillation.

[0003] Due to environmental and economic reasons, the demand for hard alloy recycling is increasing. The availability of primary raw materials is limited, and the extraction of these raw materials requires a large amount of resources.

[0004] Although the Zn process is considered effective, it is not environmentally friendly and has a high energy requirement. The final carbide product obtained by the Zn process contains a large amount of metal binder, usually Co, and other metals are also present in the waste, such as grain growth inhibitors such as Cr, V, etc., which will largely remain in the final carbide product.

[0005] In recent years, the components of recycled materials in hard alloy production have increased, which has led to higher quality requirements for the recycled carbide powder. Due to the increase in the components of recycled materials, certain elements may accumulate in the recycled materials over time during the repeated recycling of hard alloys. If not removed during recycling, some elements from coatings and / or residues (such as brazing residues) may cause defects in the microstructure of the hard alloy if the amount is too high.

[0006] An object of the present invention is to obtain an environmentally friendly and energy-saving method for recycling hard alloy waste, in which the carbide powder has high quality.

[0007] Another object of the present invention is to obtain a method for recycling hard alloy waste that reduces the amount of grain growth inhibitors such as Cr, V, etc.

[0008] An object of the present invention is to obtain a method for removing residues and / or coatings from hard alloy waste, in which the remaining hard alloy waste is recycled. Summary of the Invention

[0009] The present invention relates to a method for manufacturing carbide powder from hard alloy waste containing tungsten carbide and a metal binder. The method includes the following steps:

[0010] a) At atmospheric pressure, the cemented carbide waste is subjected to acid treatment at a temperature between 15 and 99 °C for a period of at least 24 hours to dissolve the metal binder in an acid solution, wherein the acid is H2SO4 with a concentration between 0.4 and 10 N, and the cemented carbide waste is in a stationary state during the acid treatment, thereby forming an acid solution containing the dissolved metal binder and a solid component containing a carbide skeleton portion, wherein the carbide skeleton portion is formed by dissolving the metal binder in at least the outer part of the original cemented carbide waste.

[0011] b) Separate the acid solution from the solid component.

[0012] c) If the solid component contains a part of the original cemented carbide waste in which the metal binder still exists as a cemented carbide residue inside, separate the carbide skeleton portion from the cemented carbide residue.

[0013] d) Crush the carbide skeleton portion into carbide residues, and

[0014] e) Grind the carbide residues to form carbide powder.

[0015] In this text, the cemented carbide waste refers to solid cemented carbide workpieces in the shape of cutting inserts, drills, end mills, mining button bits, rolls, etc.

[0016] In this text, the cemented carbide refers to a sintered material containing hard phase grains embedded in a metal binder, wherein the hard phase contains at least 50 wt% of WC. Other hard phase components that may be present are one or more carbides, nitrides or carbonitrides of Nb, Ti, Ta, Cr, V, etc.

[0017] The metal binder can be any metal binder used in the field of cemented carbides, such as one or an alloy of Fe, Co and Ni. The most commonly used binder is Co.

[0018] If necessary, the cemented carbide waste undergoes more than one classification step. The classification step has several purposes. One purpose is to eliminate non-cemented carbide wastes, such as cermets (where the hard phase is mainly TiCN or TiC), steels, ceramics, etc.

[0019] Once the non-cemented carbide wastes are eliminated from the remainder, the cemented carbide workpieces are also classified into different categories based on size, shape, etc.

[0020] In one embodiment of the present invention, cemented carbide scrap is classified by using markings already present on cutting tools / cemented carbide workpieces. An example of such markings is described in US 2021 / 0229175. Such markings can give information about chemical composition, coating type, etc., so that the scrap can be processed in batches, enabling the production of final carbide powders with a more predictable composition.

[0021] In one embodiment of the present invention, before subsequent process steps, the cemented carbide scrap is broken into smaller workpieces. The breaking can be carried out by any mechanical means suitable for this purpose, such as crushers, shredders, hammer mills, (gravity) drop hammers, etc. If the broken cemented carbide scrap is broken into small enough workpieces before acid treatment, the metal binder is dissolved throughout the workpiece. How small the broken workpieces should be after the metal binder is dissolved throughout depends on the type of scrap.

[0022] In one embodiment of the present invention, when the cemented carbide scrap is broken before acid treatment, no other process steps / treatments are performed on the broken material before acid treatment, i.e., the acid treatment is applied directly after the breaking step.

[0023] If a cleaning and / or de-coating step is required, the breaking can be carried out before or after the cleaning and / or de-coating step.

[0024] In one embodiment of the present invention, if the cemented carbide scrap is not very suitable for breaking, the scrap is directly subjected to acid treatment.

[0025] Whether the cemented carbide scrap is suitable for breaking depends on the type of scrap, the size of the workpiece, and the physical properties of the scrap (such as hardness and toughness). Additionally, if the cemented carbide workpiece is small enough for the metal binder to be dissolved throughout, the breaking step is not required.

[0026] To dissolve the metal binder, the cemented carbide scrap is subjected to acid treatment by placing the scrap in an acid solution containing sulfuric acid (H2SO4) and water, where the concentration (normality) is between 0.2 and 10 N, preferably between 0.3 and 6 N, to dissolve the binder.

[0027] The temperature of the acidic solution is between 15 and 99 °C, preferably between 50 and 90 °C.

[0028] During the acid treatment, the cemented carbide scrap is in a stationary state. This means herein that the cemented carbide scrap workpiece is stationary during leaching, i.e., no mechanical interference, such as continuous milling, etc., is applied to the cemented carbide scrap. Since it is desired to maintain the grain size of the WC grains, mechanical interference during the leaching step will break some WC grains, and the recovered carbide powder will have limited uses.

[0029] The acid treatment is carried out at atmospheric pressure. This means in this context that no pressure is applied.

[0030] In one embodiment of the present invention, the acid treatment is carried out without applying any electric current.

[0031] The time the cemented carbide workpiece stays in the acid solution is between 24 hours and 100 days, preferably between 3 and 50 days.

[0032] After the acid treatment, the dissolved metal binder will be present in the acid solution, and the remaining cemented carbide waste will form a solid component.

[0033] The solid component comprises the part of the cemented carbide waste from which the metal binder has been removed by acid treatment, which is referred to herein as the carbide skeleton part. This means in this context that this part still has its original shape, but the metal binder is absent, resulting in the carbide particles being held together loosely enough to be broken by mechanical means (such as crushing). The solid component may also comprise a powder component of carbides derived from the spontaneous decomposition of the carbide skeleton.

[0034] If the cemented carbide waste has been subjected to a crushing step before the acid treatment, the acid will dissolve the metal binder throughout the workpiece, and the entire workpiece will form a carbide skeleton.

[0035] If the cemented carbide waste is subjected to acid treatment without a crushing step, the binder throughout the workpiece may not be dissolved in a single acid treatment step.

[0036] When no crushing step is carried out before the acid treatment, the solid component after the acid treatment will also contain parts in which metal binder still remains, so-called cemented carbide residues. Generally, the metal binder still remains inside the original cemented carbide waste, while the outside is the carbide skeleton part from which the metal binder has been removed during the acid treatment.

[0037] If desired, the carbide skeleton part can be further released from the cemented carbide residues (i.e., the inside) by mechanical means (i.e., vibration, sieving, etc.). Then, the cemented carbide residue part is preferably removed from the carbide skeleton part and the acid solution by sieving and / or magnetic separation. Due to the presence of the metal binder, the cemented carbide residue part still containing the metal binder will still be magnetic, while the skeleton part is not magnetic since the metal binder has been removed.

[0038] Then, the cemented carbide residue part will be treated as cemented carbide waste and will be subjected to one or more additional acid treatments until all the metal binder is dissolved.

[0039] After the acid treatment, the metal binder exists as ions in the acidic solution.

[0040] Remove the acid solution and wash the carbide skeleton part to remove any residual acid. Water is usually suitable for washing.

[0041] Preferably, after separating the carbide residue from the acid solution, the metal binder dissolved in the acid solution is recovered by precipitation.

[0042] Then, preferably, the washed carbide skeleton part is dried.

[0043] To make the carbide skeleton part suitable for grinding, it is usually necessary to mechanically break the carbide skeleton into smaller workpieces so that it is suitable for the grinding step. This is preferably carried out by crushing to form carbide residues.

[0044] Grinding can be carried out by any grinding techniques common in the carbide field, such as ball mills, attritor mills, bead mills, jet mills, etc.

[0045] In one embodiment of the present invention, the cemented carbide scrap is subjected to a cleaning and / or de-coating step before recycling to remove residues and / or coatings from the cemented carbide scrap. The method comprises the following steps:

[0046] - Pre-acid treat the cemented carbide scrap in an acid solution with a concentration between 0.2 and 10 N at a temperature between 15 and 99 °C for a period between 30 minutes and 72 hours;

[0047] - Mechanically remove the residues and / or coatings.

[0048] The most common type of cemented carbide scrap with a coating is cutting tools, such as inserts, drills, end mills, etc. Typical coatings are deposited using conventional PVD (Physical Vapor Deposition) and CVD (Chemical Vapor Deposition). Recently, more advanced deposition techniques have also become more common, such as HIPIMS (High Power Impulse Magnetron Sputtering), which is a PVD technique.

[0049] Cutting tools (such as inserts) are usually deposited using PVD or CVD techniques, while cutting tools (such as drills or end mills) are usually coated using PVD techniques.

[0050] As used herein, residues refer to any unwanted particles or elements that are beneficially removed from the cemented carbide scrap before recycling the cemented carbide. Examples of residues are brazing residues, rock residues, residues of workpiece materials welded to the cutting tool during mechanical operation, etc.

[0051] Hard alloy mining tools and wear parts are usually brazed to supports, drill bits, etc. Before recycling, the hard alloy parts are separated from the support, and some solder may still remain on the hard alloy parts. Mining tools can also contain parts of rocks that are wedged into the mining tools during operation. Cutting tools can also contain brazed parts, which may leave brazing residues.

[0052] In the pre-acid treatment for removing residues and / or coatings, the acid used in the acid solution can be any acid capable of dissolving the metal binder under the residues and / or coatings. Preferably, the acid is one or more of sulfuric acid (H2SO4), hydrochloric acid (HCl), acetic acid (CH3COOH), or phosphoric acid (H3PO3). More preferably, it is one or more of sulfuric acid (H2SO4) and hydrochloric acid (HCl), and most preferably sulfuric acid (H2SO4). When the hard alloy waste contains brazing residues (such as solder), the solder can also be at least partially dissolved in the acid. The concentration of the acid solution is between 0.2 and 10 N, preferably between 0.3 and 6 N, and more preferably between 0.5 and 5 N. The temperature of the acid solution can be between 15 and 99 °C, preferably between 50 and 90 °C. The time for pre-acid treatment of the hard alloy is between 30 minutes and 72 hours, preferably between 10 and 48 hours. This time depends on the concentration and temperature of the acid solution.

[0053] In one embodiment of the present invention, the pre-acid treatment is carried out without any applied pressure or current.

[0054] After the pre-acid treatment, it is preferred to wash the hard alloy workpiece to remove any residual acid. This is mainly to avoid corrosion of the equipment.

[0055] The acid used in the pre-acid treatment can be reused. For example, it can be used in the manufacture of carbide powders according to the present invention.

[0056] After the pre-acid treatment, any residues and / or coatings will still exist, but the adhesion is poor because the acid treatment has dissolved the metal binder in the outermost part of the hard alloy. Therefore, the residues and / or coatings can be removed.

[0057] After the pre-acid treatment, the residues and / or coatings are removed from the hard alloy waste by mechanical means. Here, mechanical means refer to any type of mechanical treatment capable of removing the residues and / or coatings. Preferably, the residues and / or coatings are removed by sandblasting or tumbling. After the mechanical treatment, the removed residues and / or coating residues are separated from the hard alloy waste by any suitable means (such as screening, magnetic means, etc.).

[0058] In one embodiment of the present invention, after pre-acid treatment, residues and / or coatings are removed from the cemented carbide scrap by sandblasting. Sandblasting can be used for all types of cemented carbide scrap, but is particularly suitable for grooved drill bits and end mills. If there is a coating in the grooves, it may be difficult to achieve using other types of mechanical removal methods. The exact parameters of the sandblasting step, i.e., the type of sandblasting medium, sandblasting pressure, wet or dry sandblasting, nozzle size, etc., may depend on several factors, such as the type of sandblasting equipment used, and are adjusted by those skilled in the art to achieve the desired result.

[0059] In one embodiment of the present invention, after pre-acid treatment, residues and / or coatings are removed from the cemented carbide scrap by tumbling. The most common type of tumbling is to place the workpieces in a rotating drum, where the workpieces collide with each other and with the walls of the drum. Tumbling is particularly suitable when a large volume of cemented carbide scrap is to be processed. The parameters of the tumbling process, such as the load of the drum, the rotational speed, etc., are set by those skilled in the art according to the type and size of the drum, the size of the cemented carbide scrap, etc.

[0060] In one embodiment of the present invention, the cemented carbide scrap is mechanically treated before the pre-acidification step. The mechanical treatment can be any technique that can cause defects (such as cracks in the coating) or even break the cemented carbide scrap into smaller workpieces. Examples of such techniques are tumbling, sandblasting, and crushing. Causing defects or breaking the scrap can make the acid in the acid treatment more easily penetrate the coating, thus dissolving the metal binder. This step can be beneficial if the coating thickness is too large and / or if the coating has a very dense type (such as HIPIMS coating, etc.).

[0061] In one embodiment of the present invention, the method relates to a method for manufacturing carbide powder from coated cemented carbide scrap, wherein the method comprises the following steps:

[0062] a) performing a cleaning and / or de-coating step and a crushing step on the cemented carbide scrap,

[0063] b) acid-treating the crushed cemented carbide scrap at a temperature between 15 and 99 °C under atmospheric pressure to dissolve the metal binder in the acid solution, wherein the acid is H2SO4 with a concentration between 0.2 and 10 N, for a period of at least 24 hours, wherein the cemented carbide scrap is in a stationary state during the acid treatment, thereby forming an acid solution containing the dissolved metal binder and a solid component containing the carbide skeleton portion, wherein the carbide skeleton portion is formed by dissolving the metal binder,

[0064] c) separating the acid solution from the solid component containing the carbide skeleton portion,

[0065] d) Crushing the carbide skeleton portion into carbide residues, and

[0066] e) Grinding the carbide residues to form carbide powder.

[0067] In one embodiment of the present invention, the method relates to a method for manufacturing carbide powder from uncoated cemented carbide waste, wherein the method comprises the following steps:

[0068] a) Performing a cleaning process on the cemented carbide waste and a crushing step,

[0069] b) At atmospheric pressure, treating the crushed cemented carbide waste with an acid at a temperature between 15 and 99 °C to dissolve the metal binder in the acid solution, wherein the acid is H2SO4 with a concentration between 0.2 and 10 N, for a period of at least 24 hours, wherein the cemented carbide waste is in a stationary state during the acid treatment, thereby forming an acid solution containing the dissolved metal binder and a solid component containing the carbide skeleton portion, wherein the carbide skeleton portion is formed by dissolving the metal binder,

[0070] c) Separating the acid solution from the solid component containing the carbide skeleton portion,

[0071] d) Crushing the carbide skeleton portion into carbide residues, and

[0072] e) Grinding the carbide residues to form carbide powder.

[0073] In one embodiment of the present invention, the method relates to a method for manufacturing carbide powder from uncoated cemented carbide waste, wherein the method comprises the following steps:

[0074] a) At atmospheric pressure, treating the cemented carbide waste with an acid at a temperature between 15 and 99 °C to dissolve the metal binder in the acid solution, wherein the acid is H2SO4 with a concentration between 0.2 and 10 N, for a period of at least 24 hours, wherein the cemented carbide waste is in a stationary state during the acid treatment, thereby forming an acid solution containing the dissolved metal binder and a solid component containing the carbide skeleton portion, wherein the carbide skeleton portion is formed by dissolving the metal binder in at least the exterior of the original cemented carbide waste,

[0075] b) Separating the cemented carbide component in which the metal binder still remains from the cemented carbide component from which the binder has been dissolved,

[0076] c) The cemented carbide component from which the binder has been dissolved will form carbide residues,

[0077] d) Separating the carbide residue from the acid solution and the metal binder, and

[0078] e) Subjecting the carbide residue to a grinding step to form carbide powder.

[0079] The invention also relates to carbide powder produced according to the above method.

[0080] The final carbide powder contains less than 1 wt% of metal binder, preferably less than 0.5 wt% of metal binder, more preferably less than 0.2 wt% of metal binder.

[0081] In one embodiment of the invention, the final carbide powder will contain at least 40% less Cr, preferably 50% less Cr, than the Cr initially present in the hard alloy scrap.

[0082] In one embodiment of the invention, the final carbide powder will contain at least 20% less V, preferably 30% less V, than the V initially present in the hard alloy scrap.

[0083] Since the WC grains remain almost completely unchanged throughout the process, the WC grain size in the final carbide powder will be the same as the WC grain size in the hard alloy scrap.

[0084] The invention also relates to the use of the recycled carbide powder for manufacturing sintered hard alloys, wherein the hard phase in the hard alloy comprises at least 50 wt% of the recycled carbide powder as described above, preferably at least 70 wt%, more preferably at least 90 wt%, and most preferably consists of 100% of the recycled carbide powder. The recycled carbide powder is used in the same manner as conventional WC raw materials, and the hard alloy is manufactured according to standard practices in the art, i.e., mixing the input raw materials (e.g., by wet grinding), forming a slurry, spray drying, pressing, and sintering. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 Shows a flow chart of one embodiment of the invention, wherein

[0086] A is a cleaning and / or de-coating step,

[0087] B is a crushing step,

[0088] C is an acid treatment,

[0089] D is a step of separating the acid solution from the solid components,

[0090] E is a step of separating the hard alloy scrap still containing metal binder if the metal binder has not been completely dissolved in the acid treatment, for recycling for further acid treatment,

[0091] Step F is to break the carbide skeleton part.

[0092] Step G is the grinding step.

[0093] Figure 2 An optical micrograph of the sintered cemented carbide from Example 7 is shown.

[0094] Example 1 (Invention)

[0095] The uncoated cemented carbide waste in the shape of indexable inserts was broken into smaller workpieces and sieved to a size below 8 mm. Then the waste workpieces were placed in a container. Acid treatment was carried out in 12 wt% H2SO4 (2.6 N) at 80 °C. To maintain the acid concentration in the container, the acid concentration was continuously adjusted during the acid treatment. The total time of acid treatment was 17 days.

[0096] At the end of the acid treatment process, the acid was removed and the remaining carbide skeleton part was washed in 4 washing cycles to remove any residual acid residues.

[0097] The remaining carbide skeleton part was broken to a size less than 1 mm and then ground in a ball mill to form carbide powder.

[0098] The final carbide powder was analyzed, and the elemental analysis and grain size are listed in Table 1. The remaining elements are W and impurities, and all values are in wt%. The oxygen and carbon contents were analyzed using a LECO instrument (WC-600), and the other elements were analyzed using a Panalytical Axios MaxAdvanced Instrument using XRF (X-ray fluorescence).

[0099]

[0100] Example 2 (Invention)

[0101] Pre-destroyed bars of cemented carbide were used as the starting material for the cemented carbide waste.

[0102] Then the waste workpieces were placed in a container. Leaching was carried out with 12 wt% H2SO4 (2.6 N) at 60 °C. The acid concentration was kept as stable as possible. To maintain the acid concentration in the container, the acid concentration was continuously adjusted during the acid treatment. The total time of acid treatment was 20 days.

[0103] At the end of the leaching process, the acid was removed and the remaining carbide skeleton part was washed in 3 washing cycles to remove any residual acid residues.

[0104] After leaching, the Co content of the carbide skeleton part was 0.1%.

[0105] Decompose the remaining carbide skeleton part (<1 mm), and then grind it in a ball mill to form carbide powder.

[0106] Analyze the final carbide powder and list the properties in Table 2.

[0107]

[0108] 1 FSSS a. s. Fisher Sub-Sieve Sizer – as-supplied condition

[0109] Example 3 (Invention)

[0110] Subject a batch of coated blades to acid treatment in 12 wt% H2SO4 (2.6 N) at 70 °C for 24 hours. After acid treatment, wash the blades, and then perform a tumbling process on 1500 g of the blades by placing them in an 800 ml mill filled with water up to 2 / 3. Then run the mill for 36 hours.

[0111] After tumbling, separate the cemented carbide scrap from the fine coating residues through a sieve (1 mm).

[0112] When comparing the cemented carbide scrap before and after the coating removal process, it can be determined by visual inspection that more than 70% of the coating has been removed.

[0113] Example 4 (Invention)

[0114] Subject 13.75 tons of coated blades to treatment in 12 wt% H2SO4 (2.6 N) at 80 °C for 24 hours. After acid treatment, wash the blades and perform a tumbling process on the blades using a large mill (1 ton). Then run the mill for 36 hours.

[0115] After tumbling, separate the cemented carbide scrap from the fine coating residues through a sieve (3 mm).

[0116] When comparing the cemented carbide scrap before and after the coating removal process, it can be determined by visual inspection that more than 70% of the coating has been removed.

[0117] Example 5

[0118] For comparison, subject a batch of coated blades to a tumbling process in water for 36 hours. Wash the blades and when studied, more than 60% of the coating remains after visual inspection.

[0119] Then perform a recycling process (Zn process) on the blades to form recycled cemented carbide powder. When analyzing the recycled cemented carbide powder, coating fragments and coating residues can be detected.

[0120] Example 6

[0121] Drills and end mills coated with a PVD coating were prepared.

[0122] One batch was acid-treated in 12 wt% H2SO4 (2.6 N) at 60 °C for 24 hours. This batch is hereinafter referred to as Invention 1.

[0123] For comparison, the components of the coated cutting tools without acid treatment were divided into 3 batches, Comparisons 1 - 3.

[0124] Invention 1 and Comparisons 1 - 3 were dry-blasted using an injection blasting system, where the spray gun was manually moved in a suction blasting cabinet "Boy 100" equipped with a filtering device. The blasting medium was Al2O3 (120 mesh). The pressure was 5 bar, the nozzle diameter was 8 mm, and the nozzle distance was 70 mm. The blasting time varied and can be seen in Table 1. Visual inspections of the cutting tools were carried out, and the results are given in Table 3.

[0125]

[0126] It can be seen from the examples that by only using blasting, even with a long blasting time, the removal rate of the coating is insufficient, while the process according to the present invention shows a high removal rate.

[0127] Example 7

[0128] Recycled carbide powder manufactured according to Example 1 was used to manufacture sintered hard alloy. The carbide powder was mixed with 6.5 wt% Co and 2 wt% PEG (amount based on the total weight of the powder) to form a powder blend. The powder blend was mixed with a grinding liquid (ethanol / water) to form a slurry, which was then tray-dried and then pressed into a green body.

[0129] After the green body was degreased at 310 °C for 120 minutes, it was sintered in a vacuum at 1450 °C for 60 minutes.

[0130] The microstructure of the sintered hard alloy was studied using an optical microscope (LOM). Figure 2 LOM images are shown, where it can be seen that the microstructure is completely dense.

Claims

1. A method for manufacturing carbide powder from hard alloy waste containing tungsten carbide and a metal binder, the method comprising the following steps: a) At atmospheric pressure, at a temperature between 15 °C and 99 °C, subject the hard alloy waste to acid treatment to dissolve the metal binder in an acid solution, wherein the acid is H2SO4 with a concentration between 0.4 N and 10 N, for a period of at least 24 hours, wherein the hard alloy waste is in a stationary state during the acid treatment, thereby forming an acid solution containing the dissolved metal binder and a solid component containing a carbide skeleton portion, wherein the carbide skeleton portion is formed by dissolving the metal binder in at least the exterior of the original hard alloy waste. b) Separate the acid solution from the solid component. c) If the solid component contains a portion of the original hard alloy waste in which the metal binder still exists as a hard alloy residue in the interior, separate the carbide skeleton portion from the hard alloy residue. d) Crush the carbide skeleton portion into carbide residues, and e) Grind the carbide residues to form carbide powder.

2. The method according to claim 1, wherein the hard alloy residue is separated from the carbide skeleton portion using a magnetic method.

3. The method according to claim 2, wherein, Treat the hard alloy residue in which the metal binder still remains as hard alloy waste, and repeat the method according to claim 1 until all the metal binders are dissolved.

4. The method according to any one of the preceding claims, wherein the concentration of the acid solution is between 1 N and 6 N.

5. The method according to any one of the preceding claims, wherein the acid treatment of the hard alloy waste is carried out at a temperature between 50 °C and 90 °C, for a period between 1 day and 100 days.

6. The method according to any one of the preceding claims, wherein a crushing step is carried out on the hard alloy waste before the acid treatment, and the acid treatment is directly applied after the crushing step.

7. The method according to any one of the preceding claims, wherein the hard alloy waste is classified by using the information in the marks already existing on the hard alloy waste workpiece.

8. The method according to any one of the preceding claims, wherein a cleaning step and / or a de - coating step is carried out on the hard alloy waste before the acid treatment.

9. The method according to claim 8, wherein the cleaning step and / or the de-coating step comprises: At a temperature between 15 °C and 99 °C, subject the coated hard alloy waste to pre - acid treatment in an acid solution with a concentration between 0.2 N and 10 N, for a period between 30 minutes and 72 hours, and then remove the coating using a mechanical method.

10. The method according to claim 9, wherein the mechanical method is selected from tumbling or sandblasting.

11. The method according to any one of claims 8 - 10, wherein a mechanical pre - treatment is carried out before the pre - acid treatment, and the mechanical pre - treatment is selected from tumbling, sandblasting, and crushing.

12. A carbide powder made from recycled cemented carbide waste produced by the method according to claims 1-11, wherein the metal binder content of the powder is less than 1% by weight.

13. The carbide powder according to claim 12, wherein the metal binder content is less than 0.5% by weight.

14. Use of the carbide powder according to any one of claims 12-13 for manufacturing a sintered cemented carbide body, wherein at least 50% by weight of the hard phase is composed of the carbide powder.

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