CN115722685A - Green body sintering process based on binder jet printing - Google Patents
Green body sintering process based on binder jet printing Download PDFInfo
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- CN115722685A CN115722685A CN202211444565.XA CN202211444565A CN115722685A CN 115722685 A CN115722685 A CN 115722685A CN 202211444565 A CN202211444565 A CN 202211444565A CN 115722685 A CN115722685 A CN 115722685A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention discloses a green body sintering process based on binder jet printing, which is characterized in that a suitable binder is adopted to carry out degreasing sintering treatment on a printed green body, and the binder in the green body is completely removed at the temperature of 450-600 ℃; pre-sintering the green body at 1150-1250 ℃ under the vacuum condition, rapidly finishing preliminary densification of the internal space, and improving the densification speed; then, carrying out micro-positive pressure sintering under the protection of inert gas, further improving the density, inhibiting the evaporation of alloy elements, further quickly densifying, shortening the high-temperature sintering time, and inhibiting the coarsening of crystal grains; after sintering, cooling to 1000-1300 ℃, introducing inert gas, accelerating cooling and shortening sintering period. Compared with the whole-process vacuum sintering, the method can shorten the high-temperature time, avoid the coarse grains, shorten the sintering time, reduce the energy consumption and improve the production efficiency.
Description
Technical Field
The invention belongs to the technical field of 3D printing, and particularly relates to a green body sintering process based on binder jet printing.
Background
The binder jetting 3D printing technology has the potential of batch production as a printing method with high precision and high efficiency. However, the density of the printing green body is low, so that a plurality of defects exist in the aspects of subsequent sintering shrinkage deformation, density and the like, and the development and application of a binder spraying technology are seriously influenced.
Compared with the traditional powder metallurgy technologies such as powder injection molding, the binder spraying 3D printing technology adopts a powder laying technology to realize green body printing, and the density of the green body is lower than that of the traditional powder metallurgy green body, so that the shrinkage deformation and the density control are very difficult during post-processing sintering. Although the compactness can be improved by vacuum sintering, the problems of evaporation of alloy elements, low cooling speed and the like exist in the sintering process, and the vacuum sintering effect cannot be achieved by atmosphere sintering.
Disclosure of Invention
In order to solve the technical problems, the invention provides a green body sintering process based on binder jet printing.
The invention adopts the following technical scheme:
a green body sintering process based on binder jet printing comprises the following steps:
transferring the green body sprayed and printed by the binder to a sintering furnace, vacuumizing, heating to the degreasing temperature of 450-600 ℃, and preserving heat for 1-5 hours for full degreasing;
raising the temperature to 1150-1250 ℃, preserving the heat for 1-3h, and pre-sintering the green body to preliminarily densify the green body;
introducing inert protective gas into the sintering furnace until the positive pressure is 0.2-1Mpa, heating to the sintering temperature of 1320-1450 ℃, and preserving the heat for 0.5-3h.
The sintering process of the application rapidly completes preliminary densification through vacuum pre-sintering, further densification through micro-positive pressure sintering, shortens high-temperature sintering time, can effectively inhibit grains from being thick and large, improves density, accelerates cooling, shortens sintering time, and improves production efficiency.
Preferably, the green body is placed on loose corundum pellets while it is moved into the sintering furnace. The corundum balls can roll during sintering shrinkage, so that sliding friction is avoided, shrinkage resistance of a contact surface of a green body is reduced, and shrinkage consistency is improved.
Preferably, the evacuation is carried out to a pressure of 0.001 to 0.5Pa.
Preferably, after the inert protective gas is introduced into the furnace to a positive pressure of 0.2-1Mpa, the temperature is raised to a sintering temperature of 1320-1450 ℃, and the temperature is kept for 0.5-3h, the method further comprises the following steps: after sintering, cooling to 1000-1300 ℃, and then introducing cooling inert gas to accelerate cooling to obtain the sintered component. Cooling along with the furnace at the temperature of between 1000 and 1300 ℃ to avoid deformation and cracking of the sample caused by over-quick temperature reduction, introducing inert gas at the temperature of between 1000 and 1300 ℃, improving the cooling speed, avoiding large and thick high-temperature crystal grains and shortening the cooling time, thereby shortening the whole sintering period time and improving the production efficiency
Preferably, the printing method of the green body by binder jet printing is: and amplifying the three-dimensional model of the part to be printed by 10-20%, and then carrying out binder jet printing, curing and powder cleaning to obtain a green body. Based on a plurality of sintering experiences or simulation compensation in the initial stage, the target model is amplified and compensated to a certain degree, and then green body printing is carried out.
Preferably, the blank is formed by stainless steel powder. Further, the stainless steel powder is preferably 420L stainless steel powder having a particle size of 15 to 53 μm or 316L stainless steel powder having a particle size of 25 μm.
Preferably, the green body sintering process based on binder jet printing comprises the following steps:
(1) Amplifying the three-dimensional model of the part to be printed by 15-17%, then paving stainless steel powder, spraying and printing green body binder, curing and cleaning powder to obtain a green body;
(2) Transferring the green body to a sintering furnace, and placing the green body on loose corundum balls;
(3) Vacuumizing to 0.01-0.05Pa, heating to the degreasing temperature of 550-600 ℃, and preserving heat for 2-3h for full degreasing;
(4) Heating to 1180-1220 deg.c, maintaining for 1-3 hr to pre-sinter the green body and densify the green body preliminarily;
(5) Introducing high-purity argon into the furnace until the positive pressure is 0.4-0.6MPa;
(6) Heating to 1350-1420 deg.c for 1-3 hr to densify and sinter;
(7) And after sintering, cooling to 1200 ℃, and introducing high-purity argon for rapid cooling to finally obtain the sintered component.
Preferably, the adhesive spray printing process uses a low-temperature degreased adhesive. The low-temperature degreasing binder can completely remove the binder in the green body at 450-600 ℃.
Compared with the prior art, the invention has the following advantages: completely removing the binder in the green body at 450-600 ℃ by degreasing and sintering the printed green body by using a suitable binder; pre-sintering the green body at 1150-1250 ℃ under the vacuum condition, rapidly finishing preliminary densification of the internal space, and improving the densification speed; then, carrying out micro-positive pressure sintering under the protection of inert gas, further improving the density, inhibiting the evaporation of alloy elements, further quickly densifying, shortening the high-temperature sintering time, and inhibiting the coarsening of crystal grains; after sintering, cooling to 1200 ℃, introducing inert gas, accelerating cooling and shortening sintering period. Compared with the whole-process vacuum sintering, the method can shorten the high-temperature time, avoid the coarse grains, shorten the sintering time, reduce the energy consumption and improve the production efficiency.
Detailed Description
In order to facilitate understanding of the technical solutions of the present invention, the following detailed descriptions are given with reference to specific examples.
Example 1
1. After the model of 420 stainless steel powder (with the grain diameter of 15-53 mu m) is enlarged by 17 percent, carrying out spray printing, curing and powder cleaning on a green binder; the binder is PVA-based binder; 2. transferring the green body to a sintering furnace, and placing the green body on loose corundum balls;
3. vacuum pumping to 1.0 x 10 -2 Pa, heating to the degreasing temperature of 600 ℃, and preserving heat for 2 hours to carry out full degreasing;
4. heating to 1220 ℃, preserving heat for 2h, and presintering the green body to preliminarily densify the green body;
5. introducing high-purity argon into the furnace until the positive pressure is 0.6MPa;
6. heating to a sintering temperature of 1420 ℃, and preserving heat for 1.5h to further densify and sinter;
7. after sintering, cooling to 1200 ℃, and then introducing high-purity argon gas for rapid cooling, so that the density of the finally obtained 420 stainless steel sample is over 97%, the size deviation is less than 0.5%, and the hardness reaches 47HRC.
Example 2
1. Amplifying a 316L stainless steel powder (with the particle size of-25 mu m) model by 15 percent, and then carrying out spray printing, curing and powder cleaning on a green binder; the adhesive is ethylene glycol-based adhesive; 2. transferring the green body to a sintering furnace, and placing the green body on loose corundum balls;
3. vacuum pumping to 5.0 x 10 -2 Pa, heating to the degreasing temperature of 550 ℃, and preserving heat for 3 hours to carry out full degreasing;
4. heating to 1180 ℃, preserving heat for 1.5 hours, and pre-sintering the green body to preliminarily densify the green body;
5. introducing high-purity argon into the furnace until the positive pressure is 0.4MPa;
6. heating to 1350 ℃ for sintering, and preserving heat for 1h to further densify and sinter;
7. after sintering, cooling to 1200 ℃, and then introducing high-purity argon gas for rapid cooling, thereby finally obtaining a 316L stainless steel sample with the density of more than 95%, the dimensional deviation of less than 1.0% and the hardness of 86HRB.
Comparative example 1
1. After the model of 420 stainless steel powder (with the grain diameter of 15-53 mu m) is enlarged by 17 percent, carrying out spray printing, curing and powder cleaning on a green binder; the binder is PVA-based binder;
2. transferring the green body to a sintering furnace, and placing the green body on loose corundum balls;
3. sintering under normal pressure in argon atmosphere, heating to the degreasing temperature of 600 ℃, and preserving heat for 2 hours to carry out full degreasing;
4. heating to a sintering temperature of 1420 ℃, and preserving heat for 1.5h;
5. after sintering, cooling along with the furnace, and finally obtaining the 420 stainless steel sample with 93% density, 0.7% dimensional deviation and 42HRC hardness.
The above is only a preferred embodiment of the present invention, and the scope of the present invention is defined by the appended claims, and several modifications and amendments made by those skilled in the art without departing from the spirit and scope of the present invention should be construed as the scope of the present invention.
Claims (8)
1. A green body sintering process based on binder jet printing is characterized by comprising the following steps:
transferring the green body sprayed and printed by the binder to a sintering furnace, vacuumizing, heating to the degreasing temperature of 450-600 ℃, and preserving heat for 1-5 hours for full degreasing;
raising the temperature to 1150-1250 ℃, preserving the heat for 1-3h, and pre-sintering the green body to preliminarily densify the green body;
introducing inert protective gas into the sintering furnace to a positive pressure of 0.2-1Mpa, heating to a sintering temperature of 1320-1450 ℃, and preserving heat for 0.5-3h.
2. The green sintering process based on binder-jet printing according to claim 1, characterized in that: and when the green body is moved into a sintering furnace, placing the green body on loose corundum balls.
3. The green sintering process based on binder-jet printing according to claim 1, characterized in that: and vacuumizing to 0.001-0.5Pa.
4. The green body sintering process based on binder jet printing as claimed in claim 1, wherein after "introducing inert shielding gas into the furnace to positive pressure of 0.2-1Mpa, raising the temperature to sintering temperature of 1320-1450 ℃, and keeping the temperature for 0.5-3h", the method further comprises the following steps: after sintering, cooling to 1000-1300 ℃, and then introducing cooling inert gas to accelerate cooling to obtain the sintered part.
5. The green sintering process based on binder-jet printing according to claim 1, characterized in that: the printing method of the green body printed by the binder spraying comprises the following steps: and (3) after amplifying the target model of the part to be printed by 10-20%, carrying out binder jet printing, curing and powder cleaning to obtain a green body.
6. The green sintering process based on binder-jet printing according to claim 5, wherein: the green body is formed by stainless steel powder.
7. The green body sintering process based on binder-jet printing according to claim 1, characterized by comprising the following steps:
(1) Amplifying a target model of a part to be printed by 15-17%, then paving stainless steel powder, spraying and printing a green body binder, curing and cleaning the powder to obtain a green body;
(2) Transferring the green body to a sintering furnace, and placing the green body on loose corundum balls;
(3) Vacuumizing to 0.01-0.05Pa, heating to the degreasing temperature of 550-600 ℃, and preserving heat for 2-3h for full degreasing;
(4) Heating to 1180-1220 deg.c, maintaining for 1-3 hr to pre-sinter the green body and densify the green body preliminarily;
(5) Introducing high-purity argon into the furnace until the positive pressure is 0.4-0.6MPa;
(6) Heating to 1350-1420 deg.c for 1-3 hr to densify and sinter;
(7) And after sintering, cooling to 1200 ℃, and introducing high-purity argon for rapid cooling to finally obtain the sintered component.
8. The green sintering process based on binder-jet printing according to claim 1 or 7, characterized in that: the adhesive spray printing process uses a low-temperature degreased adhesive.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211444565.XA CN115722685A (en) | 2022-11-18 | 2022-11-18 | Green body sintering process based on binder jet printing |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211444565.XA CN115722685A (en) | 2022-11-18 | 2022-11-18 | Green body sintering process based on binder jet printing |
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| CN115722685A true CN115722685A (en) | 2023-03-03 |
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| CN202211444565.XA Pending CN115722685A (en) | 2022-11-18 | 2022-11-18 | Green body sintering process based on binder jet printing |
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