3D printing inorganic binder forming method

Abstract

The invention belongs to the technical field of additive manufacturing, and particularly relates to a 3D printing inorganic binder forming method which comprises the steps that metal powder is prepared; a powder layer is laid on a workbench of printing equipment through the prepared metal powder, an inorganic binder is sprayed to the powder layer according to a printing slicing software pattern, and then the metal blank is obtained through sequential layer-by-layer printing; curing and clearing powder; and sintering. An inorganic binder is adopted for 3D printing forming, no pungent smell is generated in the printing process, and no harm is caused to the body of an operator; green body sintering is free of carbon emission, a metal test block is free of oxidation, and the product sintering quality is good; in the whole sintering process, the toughness of the metal green body can be enhanced, and cracking of the metal green body is inhibited; compared with an organic binder, the inorganic binder has no degreasing process in sintering, so that the sintering period can be shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of additive manufacturing, and in particular relates to a 3D printing inorganic binder molding method. Background Art

[0002] Binder jetting, as a powder bed-based additive manufacturing technology, has the advantages of high automation, low cost, and high efficiency. Its unique bonding molding method is suitable for the molding of almost all types of materials such as metals, ceramics, and resins.

[0003] At present, binder jet printing technology mainly uses organic binders, which are mostly resin polymers. Among them, metal binder jet printing mainly uses PVP or PVA binder jet forming, which leads to the generation of harmful volatile gases in the post-processing process after printing, causing physical harm to operators and further polluting the environment; at the same time, gas will also escape during the sintering and degreasing process. The escaped gas reacts with the metal, seriously affecting the sintering quality of the printed product, especially the sintering process of easily oxidized metal parts is difficult to control. Summary of the invention

[0004] Based on this, it is necessary to provide a 3D printing inorganic binder molding method to address the problems of harmful volatile gases generated by organic binder jet printing in the prior art.

[0005] A 3D printing inorganic binder molding method, the molding method comprising the following steps:

[0006] Preparation of metal powder: Select metal powder with a size of 2 μm to 100 μm and a repose angle of 25° to 48°, use a 150-mesh screen to screen, filter out large particles of metal and impurities, and bake to ensure that the powder is dry and can be spread normally.

[0007] Printing a metal blank: laying a powder layer of the prepared metal powder on a workbench of a printing device, spraying an inorganic binder on the powder layer according to the print slicing software graphics, and then printing layer by layer in sequence to obtain a metal blank; preferably, the inorganic binder is a silicate inorganic binder or a phosphate inorganic binder, and its viscosity is 8Pa·s to 14Pa·s.

[0008] Curing and powder removal: The printed metal body is cured and dried to remove the floating powder on the surface of the metal body;

[0009] Sintering treatment: The metal blank after cleaning the floating powder is placed in a sintering furnace for sintering treatment, and then cooled in the furnace to obtain a metal formed product.

[0010] In one embodiment, in the step of printing the metal blank, since the green body strength is insufficient when the inorganic binder with a saturation below 40% is printed, the green body has serious ink seepage when the inorganic binder with a saturation of 100% is printed; therefore, the saturation of the inorganic binder is 40% to 100%.

[0011] In one embodiment, in the step of printing the metal blank, the powder filling rate is 20% to 70%. If the powder filling rate is less than 20%, the binder needs to fill more than 80% of the pores, which consumes a large amount of binder and will cause problems such as difficulty in solidification and ink seepage; if the powder filling rate is more than 70%, the binder needs to fill less than 30%, the binder is less, it is not easy to stick together, and the printed sample strength is insufficient.

[0012] In one embodiment, in the step of printing the metal blank, the speed of the printing device spreading the powder is 50 μm / s to 250 μm / s. If the powder spreading speed is lower than 50 μm / s, too much powder is deposited, causing the powder bed to push the powder; if it is higher than 250 μm / s, less powder is deposited, causing the powder bed to lack powder. Therefore, the preferred powder spreading speed is 50 μm / s to 250 μm / s.

[0013] In one embodiment, in the step of printing the metal blank, the speed of the printing device at the starting position of the powder spreading on the workbench is 0.1 μm / s to 10 μm / s. If the speed is lower than 0.1 μm / s, too much powder is spread, causing the powder bed to push the powder; if the speed is higher than 10 μm / s, less powder is spread, resulting in insufficient powder spreading and thus causing the powder bed to be short of powder.

[0014] In one embodiment, in the step of printing the metal blank, the speed of the compacting roller of the printing device during the printing process is 100 r / min to 600 r / min. When the speed of the compacting roller is lower than 100 r / min or higher than 600 r / min, the powder bed may push the powder during printing.

[0015] In one embodiment, in the step of printing the metal blank, the temperature of the printing device during the printing process is 30° C. to 50° C. If the baking temperature of the lamp tube of the printing device is lower than 30° C., the printed sample has serious ink seepage; if the baking temperature of the lamp tube of the printing device is higher than 50° C., the binder solidifies faster, but causes the printed sample to be delaminated.

[0016] In one embodiment, in the curing and powder removal step, the temperature range of curing the printed metal blank is 100° C. to 300° C. In this way, the binder is bonded by heat, so that the strength of the metal blank is optimized.

[0017] In one of the embodiments, in the sintering treatment step, the metal blank after cleaning the floating powder is placed in a sintering furnace, first heated to 900°C at a heating rate of 0.5°C / min to 5°C / min, and kept warm for 1h to 4h; then heated to 1400°C at a heating rate of 0.5°C / min to 2°C / min, and kept warm for 3h to 6h; then cooled in the furnace to obtain a metal formed product.

[0018] The present invention provides a forming method for 3D printing using an inorganic binder. The inorganic binder has the advantages of high bonding strength, good high-temperature performance, easy use, economy, etc.; when the inorganic binder is used for 3D printing, no pungent odor is generated during the printing process, and there is no harm to the operator's body; there is no carbon emission during the sintering of the green body, the metal test block is not oxidized, and the product sintering quality is good; in the entire sintering process, the toughness of the metal green body can be enhanced and the cracking of the metal green body can be inhibited; compared with organic binders, the inorganic binder sintering does not require a degreasing process, thereby shortening the sintering cycle.

[0019] The molding method provided by the invention has low printing cost, is suitable for industrial production, and has good market prospects. DETAILED DESCRIPTION

[0020] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are provided. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood.

[0021] A 3D printing inorganic binder molding method specifically comprises the following steps:

[0022] Preparation of metal powder: Select metal powder with a size of 2 μm to 100 μm and a repose angle of 25° to 48°, use a 150-mesh screen to screen, filter out large particles of metal and impurities, and bake to ensure that the powder is dry and can be spread normally.

[0023] Printing metal blank: Lay a powder layer of the prepared metal powder on the workbench of the printing equipment, spray an inorganic binder on the powder layer according to the printing slicing software graphics, and then print layer by layer in sequence to obtain the metal blank; the inorganic binder can be a silicate inorganic binder or a phosphate inorganic binder, with a saturation of 40% to 100% and a viscosity of 8Pa·s to 14Pa·s.

[0024] Specifically, during the printing process, the powder filling rate of the printing device is 20% to 70%, the powder spreading speed is 50μm / s to 250μm / s, that is, the speed of the powder spreader of the printing device moving on the workbench; the powder spreading speed at the starting position of the workbench powder spreading is 0.1μm / s to 10μm / s, which can be called the powder stacking speed, that is, the movement speed of the powder spreader at the starting position of the workbench powder spreading 1cm; the speed of the compacting roller of the printing device is 100r / min to 600r / min. During the printing process, baking is carried out in time, and the baking temperature of the lamp of the printing device is 30℃ to 50℃.

[0025] Curing and powder cleaning treatment: The printed metal blank is cured and dried at a temperature of 100°C to 300°C. After the set time, the floating powder on the surface of the metal blank is cleaned.

[0026] Sintering treatment: The metal blank after cleaning the floating powder is placed in a sintering furnace for sintering treatment. First, the temperature is increased to 900°C at a heating rate of 0.5°C / min to 5°C / min, and the temperature is kept for 1h to 4h; then the temperature is increased to 1400°C at a heating rate of 0.5°C / min to 2°C / min, and the temperature is kept for 3h to 6h; then the metal blank is cooled in the furnace to obtain a metal formed product.

[0027] Embodiment 1

[0028] A 3D printing inorganic binder molding method specifically comprises the following steps:

[0029] Preparation of metal powder: Select copper powder with a size of 2 μm to 100 μm, sieve it with a 150-mesh sieve, and bake it to ensure that the powder is dry and can be spread normally.

[0030] Printing copper test block: Lay the prepared copper powder on the workbench of the printing equipment to form a powder layer, spray the inorganic binder on the powder layer according to the print slice software graphics, and then print layer by layer to obtain the copper test block. The parameters during the printing process are: printing layer thickness is 150μm, powder filling rate is 45%, binder saturation is 65%, powder spreading speed is 180μm / s, powder stacking speed is 5μm / s, compaction roller speed is 500r / min, and baking temperature is 40℃.

[0031] Curing and powder removal treatment: Place the printed copper test block in a vacuum drying oven for curing and drying at 200°C for 2 hours, and then remove the floating powder on the surface of the copper test block.

[0032] Sintering treatment: the copper test block after cleaning the floating powder is placed in a sintering furnace, vacuumed, heated to 900°C at a heating rate of 5°C / min and kept warm for 1h; then heated to 1070°C at a heating rate of 1°C / min and kept warm for 4h; then cooled in the furnace to obtain the finished copper test block.

[0033] Embodiment 2

[0034] A 3D printing inorganic binder molding method specifically comprises the following steps:

[0035] Preparation of metal powder: Select stainless steel powder with a size of 2 μm to 100 μm, sieve it with a 150-mesh sieve, and bake it to ensure that the powder is dry and can be spread normally.

[0036] Printing stainless steel test block: Lay the prepared stainless steel powder on the workbench of the printing equipment to form a powder layer, spray the inorganic binder on the powder layer according to the print slice software graphics, and then print layer by layer to obtain the stainless steel test block. The parameters during the printing process are: printing layer thickness of 160μm, powder filling rate of 55%, binder saturation of 65%, powder spreading speed of 160μm / s, powder stacking speed of 3μm / s, compaction roller speed of 600r / min, and baking temperature of 45℃.

[0037] Curing and powder removal treatment: Place the printed stainless steel test block in a vacuum drying oven for curing and drying at 200°C for 4 hours, and then remove the floating powder on the surface of the stainless steel test block.

[0038] Sintering treatment: the stainless steel test block after cleaning the floating powder is placed in a sintering furnace, vacuumed, heated to 900°C at a heating rate of 4°C / min and kept warm for 1h; then heated to 1375°C at a heating rate of 1.5°C / min and kept warm for 5h; then cooled in the furnace to obtain the finished stainless steel test block.

[0039] Embodiment 3

[0040] A 3D printing inorganic binder molding method specifically comprises the following steps:

[0041] Preparation of metal powder: Select high-temperature alloy powder with a size of 2 μm to 100 μm, sieve it with a 150-mesh sieve, and bake it to ensure that the powder is dry and can be spread normally.

[0042] Printing high-temperature alloy test blocks: Lay the prepared high-temperature alloy powder on the workbench of the printing equipment to form a powder layer, spray the inorganic binder on the powder layer according to the print slice software graphics, and then print layer by layer to obtain the high-temperature alloy test block. The parameters during the printing process are: printing layer thickness of 180μm, powder filling rate of 35%, binder saturation of 70%, powder spreading speed of 150μm / s, powder stacking speed of 4μm / s, compaction roller speed of 450r / min, and baking temperature of 40℃.

[0043] Curing and powder removal treatment: Place the printed aluminum alloy test block in a vacuum drying oven for curing and drying. After curing at 160°C for 3 hours, remove the floating powder on the surface of the high-temperature alloy test block.

[0044] Sintering treatment: Place the high-temperature alloy test block after cleaning the floating powder in a sintering furnace, evacuate, heat to 900°C at a heating rate of 4°C / min and keep warm for 1h; then heat to 1260°C at a heating rate of 1.5°C / min and keep warm for 5h; then cool with the furnace to obtain the finished high-temperature alloy test block.

[0045] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0046] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A 3D printing inorganic binder molding method, characterized in that: The molding method comprises the following steps: preparing metal powder; Printing metal blank: Lay the prepared metal powder on the workbench of the printing equipment to form a powder layer, spray the inorganic binder on the powder layer according to the printing slice software graphics, and then print layer by layer to obtain the metal blank; Curing and powder removal: The printed metal body is cured and dried to remove the floating powder on the surface of the metal body; Sintering treatment: The metal blank after cleaning the floating powder is placed in a sintering furnace for sintering treatment, and then cooled in the furnace to obtain a metal formed product.

2. The 3D printing inorganic binder forming method according to claim 1, characterized in that: In the step of printing the metal blank, the saturation of the inorganic binder is 40% to 100%.

3. The 3D printing inorganic binder forming method according to claim 1, characterized in that: In the step of printing the metal blank, the powder filling rate is 20% to 70%.

4. The 3D printing inorganic binder forming method according to claim 1, characterized in that: In the step of printing the metal blank, the speed of the printing device spreading powder is 50 μm / s to 250 μm / s.

5. The 3D printing inorganic binder forming method according to claim 1, characterized in that: In the step of printing the metal blank, the speed of the printing device in spreading powder at the starting position of the workbench is 0.1 μm / s to 10 μm / s.

6. The 3D printing inorganic binder forming method according to claim 1, characterized in that: In the step of printing the metal blank, the rotation speed of the compacting roller of the printing device during the printing process is 100 r / min to 600 r / min.

7. The 3D printing inorganic binder forming method according to claim 1, characterized in that: In the step of printing the metal blank, the temperature of the printing device during the printing process is 30° C. to 50° C.

8. The 3D printing inorganic binder forming method according to claim 1, characterized in that: In the curing and powder cleaning step, the temperature range for curing the printed metal blank is 100° C. to 300° C.