CN114226756B

CN114226756B - Additive manufacturing method

Info

Publication number: CN114226756B
Application number: CN202010938377.7A
Authority: CN
Inventors: 东青; 张佼; 孙宝德
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2020-09-09
Filing date: 2020-09-09
Publication date: 2023-06-16
Anticipated expiration: 2040-09-09
Also published as: CN114226756A

Abstract

The application relates to an additive manufacturing method, and relates to the technical field of metallurgy. The additive manufacturing device comprises a spraying module, a crystallization module and a traction module, wherein the spraying module comprises a first chamber, and at least one nozzle is arranged on the first chamber; the crystallization module comprises a second chamber, and the second chamber is provided with a second feed inlet; the traction module comprises a dummy bar head configured to be movable within the second chamber; the nozzle penetrates through the second feeding hole and stretches into the second cavity, and the spraying direction of the nozzle faces the dummy bar head. Therefore, the method can adopt an additive manufacturing mode to perform metal casting, and improve the quality of cast ingots.

Description

Additive manufacturing method

Technical Field

The application relates to the technical field of metallurgy, in particular to an additive manufacturing method.

Background

In the prior art, semi-continuous casting is a manufacturing method of large-size aluminum alloy ingots which are conventionally adopted in industry, and mainly comprises two modes: one is hot top casting and the other is direct chill casting. The hot top casting has the advantages that the liquid level in the casting process is stable, but a deeper liquid cavity is generated in the center of the cast ingot, a large-area columnar crystal area is contained in a solidification structure, macrosegregation is serious from the center to the edge of the cast ingot, high internal stress residues exist, the cast ingot is easy to crack, the yield is low, and the method is not suitable for production of the high alloy content aluminum alloy cast ingot. The direct chill casting has the advantages that the depth of a liquid cavity in the center of the ingot can be reduced to a great extent, and then the macrosegregation and internal stress of the ingot are relieved; however, the liquid level is unstable in the casting process, slag is easy to roll, and columnar crystal areas are difficult to avoid. Therefore, it is extremely difficult to prepare a large-sized ingot with good homogeneity using a conventional process.

Disclosure of Invention

It is an object of the present application to provide an additive manufacturing method that enables metal casting in an additive manufacturing manner.

Embodiments of the present application are implemented as follows:

an additive manufacturing device comprises a spraying module, a crystallization module and a traction module, wherein the spraying module comprises a first chamber, and at least one nozzle is arranged on the first chamber; the crystallization module comprises a second chamber, wherein the second chamber is provided with a second feed inlet; the traction module includes a dummy bar head configured to be movable within the second chamber; the nozzle penetrates through the second feeding hole to extend into the second cavity, and the spraying direction of the nozzle faces the dummy bar head.

In one embodiment, the spraying module further comprises a support plate, a plug rod and a plug rod moving mechanism, and the first chamber is fixed on the support plate; the plug rod is arranged in the first cavity; the plug rod moving mechanism is in transmission connection with the plug rod and is used for driving the plug rod to move; when the plug rod is in a first preset position, the nozzle is closed by the plug rod.

In an embodiment, the injection module further includes a first feed port, a liquid supply mechanism, and a first liquid level detection element, where the first feed port is disposed in the first chamber, and a valve is connected to the first feed port; the liquid supply mechanism is connected with the first feed inlet and is used for supplying liquid; the first liquid level detection element is arranged in the first cavity.

In an embodiment, the spraying module further comprises a vent hole, a pressure regulating element and a pressure detecting element, wherein the vent hole is arranged in the first chamber; the pressure regulating element is connected to the vent hole; the air pressure detection element is arranged in the first chamber.

In an embodiment, the injection module further comprises at least one first heater and at least one first temperature detection element, the first heater being provided in the first chamber; the first temperature detection element is arranged in the first chamber.

In one embodiment, a plurality of nozzles are provided, and the plurality of nozzles are distributed in an array.

In an embodiment, the additive manufacturing apparatus further comprises a cooling module connected to the first cooler and the second cooler for driving the first cooler and the second cooler.

In an embodiment, the crystallization module further includes a second cooler, a heat insulating layer, at least one second heater, and at least one second temperature detecting element, where the second heater is disposed in the second chamber and is disposed near the second feed inlet; the second cooler is arranged in the second chamber and is spaced from the second heater; the heat insulation layer comprises a first layer wrapped outside the second chamber and a second layer arranged between the second heater and the second cooler; the second temperature detection element is arranged in the second chamber.

In an embodiment, the traction module further comprises a dummy bar head moving mechanism and a first cooler, wherein the dummy bar head moving mechanism is in transmission connection with the dummy bar head and is used for driving the dummy bar head to move along a preset route; the first cooler is arranged outside the second cavity and is positioned on the preset route.

In an embodiment, the second chamber is of an annular structure, and further comprises a second discharge port, and when the dummy bar head moves on the preset path, the dummy bar head can move outside the second chamber through the second discharge port.

In an embodiment, the additive manufacturing apparatus further includes a main control module, and the main control module is electrically connected to the spraying module, the crystallization module, and the traction module, and is used for controlling.

An additive manufacturing method, comprising:

introducing initial materials into a first cavity, and enabling the first cavity to be in a first preset environment;

opening a nozzle of the first chamber, leading initial materials to flow into a second chamber from the nozzle, accumulating the initial materials on a dummy bar head in the second chamber to form a first liquid layer, and leading the nozzle to extend into the first liquid layer;

when the nozzle is immersed into the first liquid layer to reach a preset depth, closing the nozzle, and solidifying part or all of the first liquid layer to form a solid phase;

when the height of the solid phase in the second cavity reaches a preset height, the dummy bar head is moved to a preset direction, and in the moving process, the height of the solid phase in the second cavity is within a first preset range;

and controlling the opening or closing of the nozzle, and leading the initial material into a second cavity through the nozzle according to a preset time interval, so that the thickness of the second liquid layer above the solid phase is within a second preset range.

Wherein the initial material builds up over the solid phase forming the second liquid layer together with the first liquid layer being unset.

Compared with the prior art, the beneficial effects of this application are:

according to the method, metal casting can be performed in an additive manufacturing mode, the casting mode of molten metal bulk solidification is changed, large-size cast ingots are prepared through continuous melting and superposition of the infinitesimal areas, liquid cavity formation is avoided, and meanwhile, the improvement of the cooling speed is beneficial to forming a full equiaxial crystal structure.

Furthermore, the spray mode is changed by enabling the spray nozzle to extend into the second cavity, so that the metal liquid spray mode adopts the immersion type, the spray nozzle is immersed below the metal liquid level, the oxidation risk of the metal liquid is reduced, the stability of metal liquid injection is improved, the quality of the ingot can be improved, the heat conduction difference between the edge part and the core part of the ingot can be made smaller, the generation rate of liquid cavity phenomenon is reduced, the tissue uniformity and the component uniformity of the prepared ingot are better, the internal stress of the ingot is reduced, the cracking rate and the defect rate of the ingot are reduced, and the quality and the yield of products are improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered limiting the scope, and that other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of an additive manufacturing apparatus according to an embodiment of the present application.

Fig. 2 is a schematic view of a part of an additive manufacturing apparatus according to an embodiment of the present disclosure.

Fig. 3 is a schematic view of a part of an additive manufacturing apparatus according to an embodiment of the present disclosure.

Fig. 4 is a schematic structural diagram of an additive manufacturing apparatus according to an embodiment of the present disclosure.

Fig. 5 is a schematic structural diagram of an additive manufacturing apparatus according to an embodiment of the present disclosure.

Fig. 6 is a schematic structural diagram of an additive manufacturing apparatus according to an embodiment of the present disclosure.

Fig. 7 is a schematic structural diagram of an additive manufacturing apparatus according to an embodiment of the present disclosure.

Fig. 8 is a schematic structural diagram of an additive manufacturing apparatus according to an embodiment of the present disclosure.

Fig. 9 is a flow chart of an additive manufacturing method according to an embodiment of the disclosure.

Fig. 10 is a metallographic structure diagram of an ingot provided in an embodiment of the present application.

Icon: 1-an additive manufacturing device; a 100-jetting module; 110-a first chamber; 111-a first feed inlet; 112-vent holes; 113-nozzles; 120-supporting plates; 130-stopper rod; 131-a stopper rod moving mechanism; 140-a liquid supply mechanism; 141-valve; 150-a first level detection element; 160-a voltage regulating element; 170-an air pressure detecting element; 180-a first heater; 190-a first temperature detecting element; 200-crystallization module; 210-a second chamber; 211-a second feed inlet; 212-a second discharge port; 220-a second heater; 230-a second cooler; 240-a heat insulating layer; 241-first layer; 242-a second layer; 250-a second temperature sensing element; 290-a cooling module; 300-traction module; 310-dummy bar head; 320-dummy bar head moving mechanism; 330-a first cooler; 340-a preset route; 400-a main control module; 410-a human-computer interaction interface; 420-a processor; 430-a controller; 500-diverter trays; 610-molten metal; 620-a first liquid layer; 630-solid phase; 640-liquid-solid interface; 650-water cooling line; 660-second liquid layer.

Detailed Description

The terms "first," "second," "third," and the like are used merely for distinguishing between descriptions and not for indicating a sequence number, nor are they to be construed as indicating or implying relative importance.

Furthermore, the terms "horizontal," "vertical," "overhang," and the like do not denote a requirement that the component be absolutely horizontal or overhang, but rather may be slightly inclined. As "horizontal" merely means that its direction is more horizontal than "vertical", and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the description of the present application, it should be noted that, directions or positional relationships indicated by terms such as "inner", "outer", "left", "right", "upper", "lower", etc. are directions or positional relationships based on those shown in the drawings, or those that are conventionally put in use for the product of the application, are merely for convenience of description and simplification of the description, and are not indicative or implying that the apparatus or element to be referred to must have a specific direction, be configured and operated in a specific direction, and therefore should not be construed as limiting the present application.

In the description of the present application, unless explicitly stated and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements.

The technical solutions of the present application will be clearly and completely described below with reference to the accompanying drawings.

Referring to fig. 1, a schematic structure of an additive manufacturing apparatus 1 according to an embodiment of the disclosure is shown. The additive manufacturing device 1 comprises a spraying module 100, a crystallization module 200 and a traction module 300, wherein the spraying module 100 is used for spraying molten metal to the crystallization module 200, the crystallization module 200 can be a crystallizer for cooling and solidifying the metal 610, and the traction module 300 is used for continuously drawing out a casting blank with a liquid core which is initially solidified in the crystallization module 200.

The additive manufacturing apparatus 1 of the present embodiment may be used for metal casting, that is, casting of pure metal and casting of alloy materials such as aluminum alloy, the metal materials may be pure aluminum and aluminum alloy, steel material, pure copper and copper alloy, pure zinc and zinc alloy, magnesium alloy, pure titanium and titanium alloy; the material can also be used for 3D printing by using powdery metal or plastic and other bondable materials, and the material for 3D printing can be nylon glass fiber, durable nylon material, gypsum material, aluminum material, titanium alloy, stainless steel, silver plating, gold plating, rubber and other materials. In this embodiment, the spray module 100 is located above the crystallization module 200. The additive manufacturing apparatus 1 can be used to manufacture square ingots, slab ingots, and round ingots of various sizes.

The injection module 100 includes a first chamber 110, a support plate 120, a plug rod 130, and a plug rod moving mechanism 131, where the first chamber 110 is fixed on the support plate 120 by bolting, welding, clamping, etc., so that the first chamber 110 is kept stationary.

The side wall of the first chamber 110 is provided with a first feed inlet 111, the first feed inlet 111 is connected with a liquid supply mechanism 140, and the liquid supply mechanism 140 can be a liquid storage tank, a pump and other components and is used for filling molten metal into the first chamber 110 through the first feed inlet 111. The valve 141 is connected to the first feed port 111, and the valve 141 may be a solenoid valve, a pneumatic control valve, a self-operated pressure control valve, or the like, for controlling the opening or closing of the first feed port 111, thereby controlling the flow of the feed liquid. In another embodiment, the solid metal is introduced into the first inlet 111, and melted by the heating element in the first chamber 110 to form molten metal.

The injection module 100 further includes a first liquid level detecting element 150, where the first liquid level detecting element 150 is disposed in the first chamber 110 and is configured to detect a liquid level of the metal liquid in the first chamber 110.

At least one nozzle 113 is provided at the bottom of the first chamber 110, and the nozzle 113 is used for introducing molten metal in the first chamber 110 into the second chamber 210. The plug rod 130 is arranged in the first chamber 110; the stopper rod moving mechanism 131 is in transmission connection with the stopper rod 130 and is used for driving the stopper rod 130 to move. The stopper rod moving mechanism 131 may be a motor, a motor screw, an air cylinder, a hydraulic cylinder, or the like.

In this embodiment, the stopper 130 moves vertically in a straight line, and when the stopper 130 moves downward, the stopper 130 can reach a first preset position (as shown in fig. 1), so that the nozzle 113 is closed by the stopper 130; when the stopper 130 moves upward, the stopper 130 moves away from the nozzle 113, and the stopper 130 can reach a second preset position (as shown in fig. 4) so that the nozzle 113 is opened. The longitudinal section of the stopper rod 130 is T-shaped, and the bottom of the stopper rod 130 is shaped like the bottom of the first chamber 110 for closing the plurality of nozzles 113 at one time.

The spraying module 100 further comprises a vent 112 and a pressure regulating element 160, wherein the vent 112 is arranged in the first chamber 110 and is used for detecting the temperature of the material in the first chamber 110; the pressure regulating element 160 is connected to the vent 112, the pressure regulating element 160 is an air charging assembly such as an air storage box and an air pump, and the pressure regulating element 160 regulates the air pressure of the first chamber 110 by charging an appropriate amount of inert gas such as nitrogen or argon into the first chamber 110.

The spray module 100 further includes a pressure detecting element 170, where the pressure detecting element 170 is a barometer or a pressure sensor, and is disposed in the first chamber 110 for detecting the pressure of the air in the first chamber 110.

The jetting module 100 further includes at least one first heater 180, the first heater 180 being disposed in the first chamber 110 for heating material within the first chamber 110. The first heater 180 may be an electric heating plate, a heating pipe, or the like, and the first heater 180 is provided in plurality and uniformly and directly fixed to the respective outer surfaces of the first chamber 110.

The spray module 100 further includes a first temperature detecting element 190, where the first temperature detecting element 190 is disposed in the first chamber 110 and is used to detect a temperature of a material in the first chamber 110 or detect an ambient temperature of the first chamber 110. The first temperature detecting element 190 may be a temperature sensor or a thermocouple, and may be provided with one or more.

The crystallization module 200 includes a second chamber 210, the second chamber 210 is in an annular structure, the second chamber 210 has a second inlet 211 and a second outlet 212 which are coaxially arranged, and the sizes and shapes of the second inlet 211 and the second outlet 212 are equal. In this embodiment, the inner hole of the second chamber 210 is cylindrical, that is, the inner hole in the transverse cross section of the second chamber 210 is circular. In other embodiments, the shape of the internal bore in the transverse cross-section of the second chamber 210 may be rectangular, square, triangular or other polygonal depending on the cross-sectional shape of the ingot being produced. The second feed port 211 is larger or smaller than the second discharge port 212.

The traction module 300 comprises a dummy bar head moving mechanism 320 and a dummy bar head 310, wherein the dummy bar head moving mechanism 320 is in transmission connection with the dummy bar head 310 and is used for driving the dummy bar head 310 to move along a preset route 340. Dummy bar head moving mechanism 320 may be a motor, a motor screw, a cylinder, a hydraulic cylinder, or the like.

The longitudinal section of the dummy bar head 310 is T-shaped, and the shape and the size of the top of the dummy bar head 310 are equal to those of the inner hole of the second chamber 210, so that the dummy bar head 310 can seal the second discharge hole 212 to prevent molten metal from leaking. When the dummy bar head 310 moves on the preset path 340, the dummy bar head 310 may move outside the second chamber 210 through the second discharge port 212, or may move up and down along the inner wall of the second chamber 210 in the second chamber 210.

Wherein the nozzle 113 protrudes into the second chamber 210 through the second feed port 211, and the spraying direction of the nozzle 113 is toward the dummy bar head 310.

The traction module 300 further comprises a first cooler 330, wherein the first cooler 330 is arranged outside the second chamber 210 and is positioned on a preset route 340 for cooling the material to be processed on the dummy bar head 310 and positioned outside the second chamber 210.

The crystallization module 200 further comprises a second cooler 230 and a second temperature detecting element 250, wherein the second cooler 230 is arranged in the second chamber 210 and is used for cooling the material to be processed on the dummy bar head 310 and positioned in the second chamber 210; the second temperature detecting element 250 is disposed in the second chamber 210, and is used for detecting the ambient temperature of the second chamber 210 or the temperature of the material in the second chamber 210.

In an operation, preliminary treatments such as preheating and pressure regulation are performed on the first chamber 110, and the nozzle 113 is closed, so that the dummy bar head 310 is located in the second chamber 210. The initial material to be processed enters the first chamber 110 from the first feed port 111; opening the nozzle 113, allowing the initial material to enter the second chamber 210 through the nozzle 113, wherein the initial material is accumulated on the dummy bar head 310 to form a first liquid layer 620, and the nozzle 113 is immersed in the first liquid layer 620 as the nozzle 113 extends into the second chamber 210; the nozzle 113 is then closed and a portion or all of the first liquid layer 620 is solidified by the first cooler 330 to form a solid phase 630; then, the dummy bar head 310 is moved to enable the casting blank to slowly move downwards at a constant speed, meanwhile, the nozzle 113 is opened at intervals, and the molten metal 610 is injected into the second chamber 210 at intervals in a pulse liquid supply mode through the nozzle 113; when the dummy bar head 310 moves to the position of the second cooler 230 along the preset route 340, cooling the cast embryo of the dummy bar head 310 by the second cooler 230; and finally, after the blank reaches the preparation required size, the first feed inlet 111 is closed, the first chamber 110 is not filled with the initial material, after the initial material in the first chamber 110 is consumed, and the molten metal 610 in the second chamber 210 is completely solidified, the ingot is taken out through the dummy ingot head 310, the additive manufacturing device 1 is closed, and the whole preparation process is finished.

The embodiment can adopt an additive manufacturing mode to perform metal casting, changes a casting mode of solidifying a large volume of molten metal 610, prepares a large-size cast ingot through continuous melting and superposition of a infinitesimal area, avoids liquid cavity formation, and simultaneously improves the cooling speed to be beneficial to forming a full equiaxial crystal structure.

Generally, the alloy melt injected into crystallization module 200 begins at the edges of crystallization module 200, forms a solidified shell, and then solidifies gradually from the edges toward the center as dummy bar head 310 is pulled down (cooling continues). Therefore, after the steady state solidification is established, the liquid-solid interface 640 cannot be maintained in a planar state, but becomes a concave curved surface. A larger melt pool (liquid pocket) is formed within crystallization module 200. The root cause of the liquid cavity is that the heat conduction of the side part and the core part of the ingot is greatly different, and the phenomenon is that the structure of the ingot is not uniform (the grain size of the side part and the core part are different) and the composition is not uniform (the composition of the side part and the core part is different); meanwhile, larger internal stress is brought, the cast ingot is easy to crack, and the quality and the yield of the product are reduced. The degree of sagging of the liquid-solid interface 640 is closely related to the size of the ingot. When the size of the cast ingot is smaller, the difference between the side heat conduction and the core heat conduction is smaller, the liquid-solid interface 640 is relatively straight, the uniformity of the structure and the component uniformity of the prepared cast ingot are better, and the harm caused by the liquid hole phenomenon is not obvious; when the size of the cast ingot is larger, the difference between the side heat conduction and the core heat conduction is obviously increased, the curvature of the liquid-solid interface 640 is increased, the uniformity of the structure and the component of the prepared cast ingot are poorer, and the harm caused by the liquid cavity phenomenon is extremely serious.

In this embodiment, the injection mode is changed by making the nozzle 113 extend into the second chamber 210, so that the injection mode of the molten metal 610 adopts immersion, the nozzle 113 is immersed below the liquid surface of the molten metal 610, the oxidation risk of the molten metal 610 is reduced, the injection stability of the molten metal 610 is improved, the quality of the ingot can be improved, the heat conduction difference between the edge and the core of the ingot can be made smaller, the generation rate of the liquid cavity phenomenon is reduced, the tissue uniformity and the component uniformity of the prepared ingot are better, the internal stress of the ingot is reduced, the cracking rate and the defect rate of the ingot are reduced, and the quality and the yield of products are improved.

Fig. 2 is a schematic diagram of a portion of an additive manufacturing apparatus 1 according to an embodiment of the disclosure. The nozzles 113 are provided in plurality, and the plurality of nozzles 113 are distributed in an array. The first chamber 110 is a cuboid, the bottom surface of the first chamber 110 is rectangular, and the nozzles 113 are distributed in a bidirectional array along the length direction and the width direction of the first chamber 110.

Here, the distance between two adjacent nozzles 113 in the longitudinal direction of the first chamber 110 is a1, and the distance between two adjacent nozzles 113 in the width direction of the first chamber 110 is a 2. a1 and a2 may be equal or unequal. In this embodiment, four adjacent nozzles 113 may be used as a minimum unit, and a rectangle or square may be formed between the four nozzles 113, with the apex angle b1 being 90 °.

In the present embodiment, the first chamber 110 and the second chamber 210 (refer to fig. 1) are fixed, the additive manufacturing apparatus 1 does not provide a horizontal moving platform, and the spreading and injection of the molten metal 610 are not required to be realized by the relative displacement of the horizontal platform and the nozzle 113. The injection of the molten metal 610 is realized by the geometric array arrangement of the nozzles 113 and the impact and flow action of the melt of the immersion nozzle 113, so that the embodiment can uniformly disperse a large volume of the molten metal 610 into tens or hundreds of continuous liquid flows through the geometric array arrangement of the nozzles 113, improve the uniformity of tissues and components, reduce the difference of the grain sizes of the side parts and the core parts of the cast ingot and the component difference of the side parts and the core parts, ensure that the process is easy to control, and reduce the oxidation risk of the molten metal 610 and improve the injection stability of the molten metal 610 through the impact and flow action of the melt of the immersion nozzle 113, thereby improving the quality of the cast ingot.

Referring to fig. 3, a schematic diagram of a portion of an additive manufacturing apparatus 1 according to an embodiment of the disclosure is shown. The first chamber 110 is a cylinder, the bottom surface of the first chamber 110 is a circle, the nozzles 113 are distributed in a staggered array, three adjacent nozzles 113 can be used as a minimum unit, a triangle can be formed between the three adjacent nozzles 113, in this embodiment, an equilateral triangle is formed between the three adjacent nozzles 113, the internal angle b2 is 60 °, and the distance between the two adjacent nozzles 113 is a3.

The inner bore of the nozzle 113 may be a circular truncated cone, with the bore diameter decreasing sequentially from top to bottom. In other embodiments, the nozzles 113 may be arranged in a circular array, a unidirectional linear array, or the like.

Referring to fig. 4, a schematic structural diagram of an additive manufacturing apparatus 1 according to an embodiment of the disclosure is shown. The crystallization module 200 further includes at least one second heater 220 and a heat insulation layer 240, the second heater 220 being disposed at an upper portion of the second chamber 210 and being disposed near the second feed port 211; the second heater 220 may be an electric heating plate, a heating pipe, or the like, and the plurality of second heaters 220 are uniformly fixed to the upper portion of the second chamber 210, and the second cooler 230 is fixed to the lower portion of the second chamber 210 to be spaced apart from the second heater 220.

The second chamber 210 may be a graphite ring, and the heat insulating layer 240 may be made of an insulating material such as asbestos, foam glass, ceramic fiber, hollow glass, a vacuum plate, or the like. The heat insulating layer 240 includes a first layer 241 wrapped outside the second chamber 210 and a second layer 242 between the second heater 220 and the second cooler 230, the second layer 242 serving to insulate the second heater 220 and the second cooler 230 from each other.

Therefore, the upper portion of the second chamber 210 adopts a heating and heat insulating material protection design, and the lower portion adopts a cooling design, and the liquid-solid interface 640 in the second chamber 210 is kept straight in the whole crystallization process through heat balance control, so that the quality of the ingot is improved, and an ingot with higher grain uniformity and higher component uniformity is formed, so that the tissue uniformity and component uniformity of the prepared ingot are better, the internal stress of the ingot is reduced, the cracking rate and defect rate of the ingot are reduced, and the quality and the yield of products are improved.

The second temperature detecting element 250 is provided in plurality so as to perform multi-point temperature measurement, thereby facilitating the overall detection of the temperature of the second chamber 210 and the temperature control of the second heater 220 and the second cooler 230.

Fig. 5 is a schematic structural diagram of an additive manufacturing apparatus 1 according to an embodiment of the disclosure. The additive manufacturing apparatus 1 further comprises a cooling module 290, the cooling module 290 being connected to the first cooler 330 and the second cooler 230 for driving the first cooler 330 and the second cooler 230 synchronously.

The cooling module 290 may include a circulation member, a pump, a water tank or a heat exchanger, and the like, and the first cooler 330 and the second cooler 230 are all pipeline members, and the cooling module 290 is used for filling the pipeline of the first cooler 330 and the second cooler 230 with a refrigerant liquid or a refrigerant gas to achieve a refrigeration effect.

Referring to fig. 6, a schematic structural diagram of an additive manufacturing apparatus 1 according to an embodiment of the disclosure is shown. The additive manufacturing apparatus 1 further comprises a main control module 400, wherein the main control module 400 comprises a man-machine interaction interface 410, a processor 420 and a controller 430. The main control module 400 is electrically connected with the spraying module 100, the crystallization module 200 and the traction module 300, and is used for control and information processing. The main control module 400 integrates data collection and control of each module in the additive manufacturing apparatus 1, and realizes functions of valve 141 opening and closing control, plug rod 130 movement control, first chamber 110 temperature measurement, first chamber 110 heating control, first chamber 110 pressure measurement, first chamber 110 pressure control, second chamber 210 temperature measurement, second chamber 210 heating control (temperature balance compensation), cooling module 290 control, secondary cooling system control, traction module 300 control and the like.

Fig. 7 is a schematic structural diagram of an additive manufacturing apparatus 1 according to an embodiment of the disclosure. The man-machine interaction interface 410 may be a display screen, a touch screen, a key, a knob, a switch, a rocker and other computer input and output devices, and the man-machine interaction interface 410 is configured to input instructions and read information, so as to realize man-machine interaction and information intercommunication.

The first temperature detecting element 190 detects the temperature of the first chamber 110 and transmits a signal to the processor 420, and the processor 420 processes the signal and transmits an instruction to control the temperature of the first heater 180 through the controller 430.

The second temperature detecting element 250 detects the temperature of the second chamber 210 and transmits a signal to the processor 420, and the processor 420 processes the signal and transmits an instruction to control the temperature of the second heater 220 and the second cooler 230 (cooling module 290) through the controller 430.

The air pressure detecting element 170 detects the air pressure of the first chamber 110, and transmits a signal to the processor 420, and the processor 420 processes the signal and sends an instruction, and controls the pressure regulating element 160 to regulate the air pressure through the controller 430.

The main control module 400 may further include a timer, etc., and the main control module 400 may further control the opening or closing of the nozzle 113 through the stopper rod moving mechanism 131, and the main control module 400 may further control the moving speed and moving direction of the dummy ingot head 310 of the traction module 300 through the dummy ingot head moving mechanism 320.

Referring to fig. 8, a schematic structural diagram of an additive manufacturing apparatus 1 according to an embodiment of the disclosure is shown. The additive manufacturing apparatus 1 further comprises a diverter tray 500, which diverter tray 500 may be a porous tray.

Fig. 9 is a flow chart of an additive manufacturing method according to an embodiment of the disclosure. The present method may be used in an additive manufacturing apparatus 1 as shown in fig. 1 to 7. The additive manufacturing method may include the steps of:

step S101: the initial material is introduced into the first chamber 110 and the first chamber 110 is placed in a first predetermined environment.

The starting material in this step may be a fully molten metal 610. The first preset environment in this step is temperature T1, and T1> alloy melting point, pressure is P1, and P1 is greater than or equal to 1 atmosphere (normal pressure).

In this step, the plug 130 is adjusted to make the plug 130 be at the first preset position, so as to close the nozzle 113. The first heater 180 is turned on to preheat the first chamber 110, the preheating temperature T1 is greater than the melting point of the alloy, after the first chamber 110 reaches the preheating temperature T1, the valve 141 is opened to open the first feed inlet 111, the completely melted metal liquid 610 is filled into the first chamber 110 through the liquid supply module, and then the valve 141 is closed to make the chamber in a closed state. During this time, the pressure P1 of the first chamber 110 may be greater than or equal to 1 atmosphere by charging the pressure regulating element 160 with an appropriate amount of inert gas such as nitrogen or argon.

Step S102: the nozzle 113 of the first chamber 110 is opened, the starting material is introduced from the nozzle 113 into the second chamber 210, the starting material is accumulated on the dummy head 310 in the second chamber 210 to form a first liquid layer 620, and the nozzle 113 is extended into the first liquid layer 620.

In this step, the dummy bar head 310 is placed at the lower edge of the second chamber 210 through the second discharge port 212 (refer to fig. 4), the cooling module 290 is turned on, and the first cooler 330 and the second cooler 230 are turned on simultaneously. The stopper 130 is lifted up by the stopper moving mechanism 131, the nozzle 113 is opened, the molten metal 610 in the first chamber 110 is introduced into the second chamber 210 through the nozzle 113, a first liquid layer 620 (molten metal 610 layer) is formed, and the molten metal 610 in the first liquid layer 620 is caused to permeate through the nozzle 113.

Step S103: when the nozzle 113 is submerged in the first liquid layer 620 to a predetermined depth, the nozzle 113 is closed and some or all of the first liquid layer 620 is solidified to form a solid phase 630.

In this step, the depth of the nozzle 113 immersed below the liquid surface of the first liquid layer 620 is δ (see fig. 4), and the predetermined depth in this step is 0 < δ < 20cm.

In this step, when the nozzle 113 is submerged in the first liquid layer 620 to a predetermined depth δ (0 < δ < 20 cm), the stopper rod 130 is controlled to move downward by the stopper rod moving mechanism 131, the nozzle 113 is closed, and the melt injection at the nozzle 113 is stopped. The molten metal 610 solidifies rapidly on the dummy bar head 310 under the influence of the first cooler 330 to form a solid phase 630.

Step S104: when the height of the solid phase 630 in the second chamber 210 reaches the preset height, the dummy bar head 310 is moved in the preset direction, and during the movement, the height of the solid phase 630 in the second chamber 210 is within the first preset range.

In this step, the height h1 of the solid phase 630 in the second chamber 210, that is, the height h1 of the solid phase 630 above the lower edge of the second chamber 210, that is, the height h1 of the solid phase 630 above the water cooling line 650 (refer to fig. 1), is the distance h1 between the top surface (the liquid-solid interface 640) of the solid phase 630 and the water cooling line 650. In this step, the first preset range is 0 < h1 < 2m.

In this step, when the height h1 of the solid phase 630 above the water cooling line 650 is increased to h1 (0 < h1 < 2 m), the dummy bar head moving mechanism 320 is started, and the dummy bar head 310 is pulled downward at a speed v (0 < v) to slowly move down the ingot at a constant speed, thereby performing a stable casting stage. In the process of slowly and uniformly moving down the ingot, the height h1 of the solid phase 630 in the second chamber 210 can be precisely controlled within a first preset range (0 < h1 < 2 m) by adjusting the temperature of the first cooler 330 and the second cooler 230.

Step S105: the nozzle 113 is controlled to be opened or closed, so that the initial material is introduced into the second chamber 210 through the nozzle 113 at preset time intervals, and the thickness of the second liquid layer 660 above the solid phase 630 is within a second preset range.

In this step, the thickness of the second liquid layer 660 above the solid phase 630 is h2 (see fig. 5). The second liquid layer 660 may be composed of the initial material accumulated over the solid phase 630 sprayed by the nozzle 113 in step S105 and the first liquid layer 620 not solidified in step S103. Wherein the interface between the second liquid layer 660 and the solid phase 630 is referred to as a liquid-solid interface 640. In this step, the second preset range is delta < h2 < 20cm.

This step belongs to the stable casting phase, and requires the valve 141 to be opened or closed at intervals, so as to precisely control the liquid inlet of the first chamber 110, and continuously supplement the liquid metal 610 consumed by the first chamber 110.

The step further requires intermittently opening or closing the nozzle 113, so that the molten metal 610 in the first chamber 110 is injected into the molten metal 610 in the second chamber 210 through the nozzle 113 in a pulse type and at a certain time interval Δt (0 < Δt), and the thickness of the second liquid layer 660 is h2 within a second preset range (δ < h2 < 20 cm).

In order to make the molten metal 610 smoothly injected into the second liquid layer 660 and impact the liquid-solid interface 640, the first chamber 110 needs to be pressurized by the pressure regulating element 160 simultaneously, so that the pressure P1 of the first chamber 110 is greater than the pressure P2 of the second chamber 210, and at this time, the pressure P1 of the first chamber 110 is greater than 1 atmosphere, and the pressure P2 of the second chamber 210 is 1 atmosphere (normal pressure).

Continuing with step S105, the casting process may end when the ingot reaches the preparation desired size. In the ending process, the valve 141 may be closed first, the first chamber 110 is not filled with the molten metal 610, after the molten metal 610 in the first chamber 110 is consumed and the molten metal 610 in the second chamber 210 is completely solidified, the first heater 180 and the second heater 220 are closed, the pressure regulating element 160 is closed, the cooling module 290 is kept in an open state, after the whole ingot is sufficiently cooled, the cooling module 290 is closed again, the ingot is taken out through the dummy ingot head 310, and the whole preparation process is ended, and the additive manufacturing apparatus 1 is closed.

Referring to fig. 10, a metallographic structure diagram of an ingot according to an embodiment of the present disclosure is shown. In one embodiment, the applicant has tested the additive manufacturing apparatus 1 shown in fig. 1 to 7 and the additive manufacturing method shown in fig. 9.

Test target: a round ingot with the diameter of 200mm is cast, and the material is 6082 aluminum alloy.

Test equipment: the nozzles 113 are arranged in a staggered array, three adjacent nozzles 113 form a regular triangle, and the interval between any two adjacent nozzles 113 is a3=20mm.

The test process comprises the following steps:

first, the nozzle 113 is adjusted to be at the lowest position (first preset position) so that the nozzle 113 is closed. The first heater 180 is turned on to preheat the first chamber 110, and the preheating temperature T1 is 680 ℃.

After the preheating temperature T1 was reached, the valve 141 was opened, the alloy liquid having a temperature of 710 c, which was completely melted, was filled into the first chamber 110, and then the valve 141 was closed, and the first chamber 110 was in a closed state at a pressure of 1 atmosphere (normal pressure).

The dummy bar head 310 was placed at the lower edge of the second chamber 210 (second discharge port 212), the first cooler 330 and the second cooler 230 were turned on, the stopper 130 was lifted up, the nozzle 113 was opened, the aluminum liquid was allowed to enter the second chamber 210 through the nozzle 113 to form an aluminum liquid layer, and the aluminum liquid was allowed to go beyond the nozzle 113, and when the nozzle 113 was submerged to a depth δ of 6cm below the liquid surface, the stopper 130 was lowered, and melt injection at the nozzle 113 was closed.

The molten aluminum rapidly solidifies on dummy bar head 310 under the influence of the cooling water in first cooler 330 to form solid phase 630. When the ingot height h1 above the water cooling line 650 (meaning the height of the solid phase 630 above the lower edge of the second chamber 210) increases to 35cm, the dummy head 310 is pulled down at a speed of v=65 mm/min to slowly move the ingot down at a constant speed, and the stable casting stage is entered.

After entering the steady casting stage, the cooling intensity is precisely controlled so that the liquid-solid interface 640 is always maintained at a vertical distance h1 of 35cm from the water cooling line 650 (the lower edge of the second chamber 210); the valve 141 is opened and closed to accurately control the liquid inlet of the first chamber 110, so that the aluminum liquid consumed by the first chamber 110 is continuously replenished; the opening and closing of the nozzle 113 are precisely controlled, so that the aluminum liquid is injected into the second chamber 210 through the nozzle 113 at intervals of Δt=12s in a pulsed liquid supply manner, and the thickness h2 of the liquid layer above the solid phase 630 in the second chamber 210 is maintained to be 10cm all the time. Meanwhile, when the plug 130 of the nozzle 113 is controlled to be opened, in order to enable the aluminum liquid to be smoothly injected into the second chamber 210 and to impact the liquid-solid interface 640, the first chamber 110 should be pressurized by the pressure control system simultaneously, so that the pressure of the first chamber 110 is 1.2 atm, and the pressure of the lower chamber is 1 atm (normal pressure). The above state is maintained stable until the casting process is finished.

After the ingot reaches the preparation required size, the valve 141 is closed, the first chamber 110 is not filled with aluminum liquid, and after the aluminum liquid in the first chamber 110 is consumed and the aluminum liquid in the second chamber 210 is completely solidified, the first heater 180 and the second heater 220 are closed, and the pressure regulating element 160 is closed. After the whole ingot is sufficiently cooled, the cooling module 290 is closed, the ingot is taken out, and the whole preparation process is finished.

The prepared 6082 aluminum alloy cast ingot is fine and uniform in crystal grain, is of a congruent-axis crystal structure, has an average crystal grain size of 100 microns and macrosegregation of less than 8% and is detected by an optical microscope and a direct-reading spectrometer, and a metallographic structure diagram is shown in figure 10.

It should be noted that, without conflict, features in the embodiments of the present application may be combined with each other.

The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An additive manufacturing method, characterized in that an additive manufacturing apparatus is used, the additive manufacturing apparatus comprising:

the spraying module comprises a first chamber, wherein a plurality of nozzles are arranged on the first chamber, and the nozzles are distributed in an array manner;

the jetting module further includes: a vent hole provided in the first chamber;

a pressure regulating element connected to the vent hole;

the air pressure detection element is arranged in the first cavity;

at least one first heater provided in the first chamber; and

at least one first temperature detecting element provided in the first chamber;

the crystallization module comprises a second chamber, wherein the second chamber is provided with a second feed inlet,

the crystallization module further comprises:

the at least one second heater is arranged in the second chamber and is close to the second feed inlet;

the second cooler is arranged in the second chamber and is spaced from the second heater;

a heat insulating layer including a first layer wrapped outside the second chamber and a second layer disposed between the second heater and the second cooler; and

at least one second temperature detecting element provided in the second chamber; and

a traction module comprising a dummy head configured to be movable within the second chamber;

the flow dividing disc is arranged on the second chamber and is a porous disc;

the nozzle penetrates through the second feeding hole and stretches into the second cavity, and the spraying direction of the nozzle faces the dummy bar head;

the traction module further includes:

the dummy bar head moving mechanism is in transmission connection with the dummy bar head and is used for driving the dummy bar head to move along a preset route; and

the first cooler is arranged outside the second cavity and is positioned on the preset route;

the liquid-solid interface in the second cavity is kept straight in the whole crystallization process through thermal balance control;

the method comprises the following steps:

when the nozzle is immersed into the first liquid layer to reach a preset depth delta, wherein the preset depth delta is more than 0 and less than 20cm, closing the nozzle, and solidifying part of the first liquid layer to form a solid phase;

when the height of the solid phase in the second cavity reaches a preset height, wherein the preset height is h1, the dummy ingot head is enabled to move towards a preset direction, and in the moving process, the height of the solid phase in the second cavity is within a first preset range, the first preset range is more than 0 and less than 1 and less than 2m, the dummy ingot head moving mechanism is started, the dummy ingot head is pulled downwards at a speed v, so that an ingot is slowly and uniformly lowered, and stable casting is carried out;

and controlling the opening or closing of the nozzle, leading the initial material to be led into a second cavity through the nozzle according to a preset time interval, and leading the thickness h2 of a second liquid layer above the solid phase to be in a second preset range, wherein the second preset range is delta < h2 < 20cm, and intermittently opening or closing the nozzle to control the liquid inlet of the first cavity.

2. An additive manufacturing method according to claim 1, wherein the jetting module further comprises:

a support plate on which the first chamber is fixed;

the plug rod is arranged in the first cavity; and

the plug rod moving mechanism is in transmission connection with the plug rod and is used for driving the plug rod to move;

when the plug rod is in a first preset position, the nozzle is closed by the plug rod.

3. An additive manufacturing method according to claim 1, wherein the jetting module further comprises:

the first feeding port is arranged in the first chamber and is connected with a valve;

the liquid supply mechanism is connected with the first feed inlet and is used for supplying liquid; and

the first liquid level detection element is arranged in the first cavity.

4. An additive manufacturing method according to claim 1, wherein the additive manufacturing apparatus further comprises:

and the cooling module is connected with the first cooler and the second cooler and is used for driving the first cooler and the second cooler.

5. An additive manufacturing method according to claim 1, wherein the additive manufacturing apparatus further comprises:

the main control module is electrically connected with the spraying module, the crystallization module and the traction module and used for controlling.