Regeneration method for recycling stainless steel powder through 3D printing

Abstract

The invention discloses a regeneration method of 3D printing stainless steel powder, and relates to the technical field of stainless steel powder recovery, and the regeneration method comprises the following steps: S1, crushing a 3D printing scrapped blank into fragments; s2, soaking the fragments in a non-oxidizing dilute alkali solution, and stirring for reaction until the fragments become powder; and S3, the powder in the S2 is taken out, cleaned and dried, and the regenerated stainless steel powder is obtained. According to the method, a thin hot alkali liquor washing mode is adopted, a binding agent on the surface of scrapped blank powder is removed, stainless steel powder recycling is achieved, and industrial waste is reduced under the condition of low-cost powder recycling. The recovered powder is clean and complete, has good fluidity, and can be directly used for printing production.

Description

Technical Field

[0001] The present invention relates to the technical field of stainless steel powder recycling, and in particular to a method for regenerating 3D printing stainless steel powder. Background Art

[0002] Metal binder jet printing technology is a newly emerging field in recent years. In the binder jet 3D printing method of stainless steel, the stainless steel powder is first bonded layer by layer according to the design pattern by the binder sprayed by the print head, and then the blank is obtained after high-temperature curing. The blank is sintered at high temperature to become a metal part. The production process will inevitably produce a certain amount of scrapped blanks, because they have not been sintered, and the stainless steel powder is only bonded and formed by the binder. If it is directly discarded, it will cause serious waste of powder raw materials and environmental pollution. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for regenerating stainless steel powder for 3D printing.

[0004] The objective of the present invention is achieved through the following technical solutions: A method for regenerating 3D printing stainless steel powder comprises the following steps: S1. Crushing the 3D printed scrap body into pieces; S2, immersing the broken pieces in a non-oxidizing dilute alkali solution, stirring and reacting until the broken pieces become powder; S3, taking out the powder in S2, cleaning it and drying it to obtain recycled stainless steel powder.

[0005] The above-mentioned stainless steel powder includes ferritic stainless steel, austenitic stainless steel, martensitic stainless steel, duplex stainless steel and precipitation hardening stainless steel. The ferritic stainless steel includes 409, 410L, 430, 430Ti, 433, 434, 436, 439, 441, 444, 446; the austenitic stainless steel includes 200 and 300 series.

[0006] In S1, the scrapped green body is crushed into pieces with a diameter of less than 1 cm.

[0007] The non-oxidizing dilute alkaline solution is one of sodium hydroxide and potassium hydroxide.

[0008] The ratio of the non-oxidizing dilute alkali solution in S2 to the added broken pieces is 10-15 L / kg.

[0009] The stirring temperature in S2 is 80-100°C.

[0010] The stirring time in S2 is 1-3 hours, the stirring is performed by mechanical stirring, and the stirring speed is 200-300r / min.

[0011] When cleaning in S3, first wash with clean water and then wash with ethanol.

[0012] The above-mentioned clean water is 80°C hot water.

[0013] In S3, the drying temperature is 60° C. for 8 hours.

[0014] The beneficial effects of the present invention are: The present invention adopts a dilute hot alkali solution washing method to remove the surface binder of the scrapped body powder and realize the recovery of stainless steel powder. The dilute alkali solution used can be recycled after adjusting the pH value, avoiding the problem of large-scale waste liquid discharge. Because no organic solvent is used, there is no air pollution and flammable and explosive hazards during the use of organic solvents, ensuring low-cost powder recovery and reducing industrial waste. The recovered powder is clean and complete, has good fluidity, and can be directly used for printing production. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the electron microscope image of Example 1; Figure 2 This is an electron microscope image of Example 2. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0017] Embodiment 1 The scrapped stainless steel 17-4 blank was initially crushed to a diameter of less than 1 cm. Weigh 1 kg of the crushed blank and immerse it in 10 L of 0.01 mol / L sodium hydroxide solution with a pH of 12. Heat the mixture to 100°C and stir it mechanically at 300r / min for 3 hours. After stopping the stirring, let it stand, pour out the supernatant, collect the precipitated powder at the bottom, and wash the powder repeatedly with 80°C hot water three times, 20L each time; after washing with clean water, wash it twice with room temperature anhydrous ethanol, 10L each time. After washing, let it stand, pour out the supernatant, collect the precipitated stainless steel powder, dry it in an electric blast oven at 60°C for 8 hours, and pass it through a 250-mesh sieve to obtain recycled stainless steel powder. The obtained sample was weighed and recorded with an electronic balance. The recovery rate calculated by weighing was 92%.

[0018] The practicality of the recycled stainless steel powder was verified, and the results are as follows: The test results of the laser particle size analyzer are shown in Table 1. The results show that the average particle size of the regenerated powder is slightly larger than that of the original powder, which may be due to the loss of small ions during the cleaning process.

[0019] Table 1 Particle size distribution of original 17-4 powder and recycled powder recovered from green body In appearance, the recycled powder is completely consistent with the original stainless steel powder. Figure 1 , A is the original 17-4 powder; B is the recycled powder) It can be seen that there is no binder residue on the surface of the recycled powder, the surface is smooth, and most of them are regular and complete spheres, similar to the original powder.

[0020] In binder jet 3D printing, whether the powder can be evenly spread into a thin layer of tens of microns is the primary condition for successful printing. The powder spreadability, that is, fluidity, can be characterized by the angle of repose. After the original powder is dried, the angle of repose is 45 o , the repose angle of recycled stainless steel 17-4 powder under the same conditions can be measured to be 38 o , has better fluidity than the original powder, proving that it can be fully reused for printing.

[0021] Embodiment 2 The scrapped 304L stainless steel blanks were initially crushed to a diameter of less than 1 cm. 2 kg of the crushed blanks were weighed and immersed in 25 L of 0.05 mol / L potassium hydroxide solution with a pH of 12.4. The mixture was heated to 90 o C, and mechanically stir at 200r / min for 2 hours. After stopping the stirring, let it stand, pour out the supernatant, collect the precipitate at the bottom, and mix it with 80 o The powder was washed with hot water at 60 °C for three times, 20 L each time. The powder was washed with anhydrous ethanol at room temperature for two times, 10 L each time. After washing, the powder was allowed to stand, the supernatant was poured out, and the precipitated stainless steel powder was collected and placed in an electric blast oven at 60 °C. o The powder was dried at 400 °C for 8 hours and passed through a 250-mesh sieve to obtain a regenerated stainless steel powder. The obtained sample was weighed and recorded using an electronic balance. The recovery rate calculated by weighing was 96%.

[0022] The practicality of the recycled stainless steel powder was verified, and the results are as follows: The test results of the laser particle size analyzer are shown in Table 2, which show that the average particle size of the regenerated powder is slightly larger than that of the original powder, mainly because small particles are lost during the cleaning process.

[0023] Table 2 Particle size distribution of original 304L powder and recycled powder recovered from green body Original powder D10: 10.23 um D15: 12.48 um D50: 21.49 um D90: 35.78um D95: 37.30 um D97: 43.32 um Recycled powder D10: 11.08 um D15: 12.71 um D50: 22.06 um D90: 37.23 um D95: 39.51 um D97: 42.93 um In appearance, from the electron microscope image ( Figure 2 , A is the original 304L powder; B is the recycled powder) It can be seen that there is no binder residue on the surface of the stainless steel powder, the surface is smooth, and most of them are regular and complete spheres.

[0024] The repose angle is used to characterize its fluidity and compared with the original powder. After the original powder is dried, the repose angle is 40.8 o Under the same conditions, the angle of repose of the recycled powder is 33 o , indicating that its fluidity has been greatly improved compared with the original powder. The main reason is that some small particles in the recycled powder are lost. The fluidity test results show that the recycled powder can be fully reused for printing.

[0025] Embodiment 3 The scrapped 430 stainless steel blanks were initially crushed to a diameter of less than 1 cm. 1 kg of the crushed blanks were weighed and immersed in 15 L of 0.08 mol / L potassium hydroxide solution with a pH of 13. The mixture was heated to 80 o C, and mechanically stir at 250r / min for 1 hour. After stopping the stirring, let it stand, pour out the supernatant, collect the precipitate at the bottom, and mix it with 80 o The powder was washed with hot water at 60 °C for three times, 20 L each time. The powder was washed with anhydrous ethanol at room temperature for two times, 10 L each time. After washing, the powder was allowed to stand, the supernatant was poured out, and the precipitated stainless steel powder was collected and placed in an electric blast oven at 60 °C. o The powder was dried at 400 °C for 8 hours and passed through a 250-mesh sieve to obtain a regenerated stainless steel powder. The obtained sample was weighed and recorded using an electronic balance. The recovery rate calculated by weighing was 96%.

[0026] The practicality of the recycled stainless steel powder was verified, and the results are as follows: The Hausner ratio is used to characterize the fluidity of the original powder and the recycled powder. Here, the Hausner ratio refers to the ratio of the tap density of the powder to the bulk density. After the original powder is dried, the Hausner ratio is 1.25, and after the recycled powder is dried, this ratio is 1.23, which is close to the original powder, proving that the recycled powder can be used for printing.

[0027] Using this method to recycle scrapped embryos can ensure that the binder is completely removed, and at the same time has no corrosive effect on the stainless steel powder. The recycled powder is clean and complete, has good fluidity, and can be used again for printing production. At the same time, the recycling yield can be as high as 88%.

[0028] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for regenerating stainless steel powder for 3D printing, characterized in that: The following steps are involved: S1. Crushing the 3D printed scrap body into pieces; S2, immersing the broken pieces in a non-oxidizing dilute alkali solution, stirring and reacting until the broken pieces become powder; S3, taking out the powder in S2, cleaning it and drying it to obtain recycled stainless steel powder.

2. The regeneration method according to claim 1, characterized in that: The stainless steel powder includes ferritic stainless steel, austenitic stainless steel, martensitic stainless steel, duplex stainless steel and precipitation hardening stainless steel. The ferritic stainless steel includes 409, 410L, 430, 430Ti, 433, 434, 436, 439, 441, 444 and 446; the austenitic stainless steel includes 200 and 300 series.

3. The regeneration method according to claim 1, characterized in that: In S1, the scrapped green body is crushed into pieces with a diameter of less than 1 cm.

4. The regeneration method according to claim 1, characterized in that: The non-oxidizing dilute alkaline solution is one of sodium hydroxide and potassium hydroxide.

5. The regeneration method according to claim 1, characterized in that: The ratio of the non-oxidizing dilute alkali solution to the added broken pieces in S2 is 10-15 L / kg.

6. The regeneration method according to claim 1, characterized in that: The stirring temperature in S2 is 80-100°C.

7. The regeneration method according to claim 1, characterized in that: The stirring time in S2 is 1-3 hours, and the stirring is carried out by mechanical stirring at a stirring speed of 200-300 r / min.

8. The regeneration method according to claim 1, characterized in that: When cleaning in S3, first wash with clean water and then wash with ethanol.

9. The regeneration method according to claim 8, characterized in that: The clean water in S3 is hot water at 80°C.

10. The regeneration method according to claim 1, characterized in that: In S3, the drying temperature is 60° C. for 8 hours.

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