A method for producing a steel-aluminum alloy having a preform skeleton

Abstract

The application provides a preparation method of a steel-aluminum alloy with a prefabricated framework, and belongs to the technical field of non-ferrous metal preparation. According to the characteristics of stainless steel and aluminum alloy materials, a stainless steel framework structure with added boron (B) elements is prepared by using a selective laser additive manufacturing technology. The stainless steel framework adopts a designed 'arch bridge' structure, has excellent compressive strength, and the 'arch bridge' structure design is flexible. The weight is reduced without reducing the strength, and the addition of boron elements can improve the strength of the stainless steel framework. An aluminum alloy melt is filled into the stainless steel 'arch bridge' shaped framework by a casting method. In the casting process, an ultrasonic wave is applied to reduce defects in the casting process, refine aluminum alloy grains, improve the heterogeneous interface bonding strength of steel and aluminum, reduce internal residual stress, and prepare a composite material of an aluminum alloy filled stainless steel framework with excellent performance and an 'arch bridge' microstructure.

Description

Technical Field

[0001] This invention belongs to the technical field of non-ferrous metal preparation, and specifically discloses a method for preparing steel-aluminum alloys with a prefabricated skeleton. Background Technology

[0002] Stainless steel is widely used in transportation, shipbuilding, and petrochemical industries due to its low price, high strength, and excellent corrosion resistance and rust prevention. With the development of industrial technology, lightweight products are a growing trend. Compared to stainless steel, aluminum alloys have lower density, lighter weight, and higher strength, making them a key member of lightweight materials. Combining the characteristics of stainless steel and aluminum alloys to create steel-aluminum composite structures can leverage the multiple advantages of both. Summary of the Invention

[0003] This invention provides a method for preparing a steel-aluminum alloy with a prefabricated skeleton. Taking into account the characteristics of stainless steel and aluminum alloy materials, selective laser additive manufacturing technology is used to prepare a stainless steel skeleton structure with added boron (B). The stainless steel skeleton adopts a designed "arch bridge" structure, which has excellent compressive strength. The "arch bridge" structure is flexible in design, reducing weight without compromising strength. The addition of boron can improve the strength of the stainless steel skeleton. Molten aluminum alloy is filled into the stainless steel "arch bridge" skeleton by casting. Ultrasonic waves are applied during the casting process to reduce casting defects, refine aluminum alloy grains, improve the bonding strength of the steel-aluminum heterogeneous interface, and reduce internal residual stress, thus preparing a high-performance composite material with an aluminum alloy-filled stainless steel skeleton and an "arch bridge" microstructure.

[0004] The above-mentioned method for preparing steel-aluminum alloys with prefabricated skeletons includes the following steps:

[0005] S1, Preparation of boron / stainless steel mixed powder

[0006] Stainless steel powder and boron powder were ball-milled and mixed to prepare boron / stainless steel mixed powder;

[0007] S2, using a selective laser additive manufacturing system to prefabricate a boron stainless steel skeleton.

[0008] t1, mount the printing substrate on the printing platform of the selective laser additive manufacturing system, place the boron / stainless steel mixed powder on the powder feeding platform of the selective laser additive manufacturing system, and close the chamber;

[0009] t2, Evacuate the vacuum, introduce argon gas, and heat the printing substrate;

[0010] t3, import the drawing of boron stainless steel skeleton. The boron stainless steel skeleton in the drawing includes an outer skin and an arch bridge structure. Multiple arch bridge structures are arranged in a preset array inside the outer skin. Slice the drawing and set the laser printing parameters.

[0011] t4, the powder spreading roller spreads the boron / stainless steel mixed powder from the powder feeding platform onto the printing substrate;

[0012] t5, Perform single-layer laser printing according to the laser printing parameters set in step t3;

[0013] At t6, the printing platform descends to a height equal to the thickness of the boron / stainless steel mixed powder on the printing substrate during t4.

[0014] t7, repeat steps t4-t6 to print the boron stainless steel skeleton layer by layer;

[0015] S3 uses an abrasive waterjet polishing boron stainless steel frame.

[0016] S4 uses ultrasonic vibration-assisted casting of steel and aluminum alloys.

[0017] The boron stainless steel skeleton prepared in step S2 is placed in a casting mold, and aluminum alloy molten liquid is poured from above the boron stainless steel skeleton downwards. At the same time, ultrasonic vibration is performed and a vacuum is drawn below the boron stainless steel skeleton until the aluminum alloy molten liquid fills the boron stainless steel skeleton. After the aluminum alloy cools, the ultrasonic vibration and vacuum are turned off, and the steel-aluminum alloy with the prefabricated skeleton is completed.

[0018] In step S1, 316L stainless steel powder with an average particle size of 26μm is used as the matrix powder, and boron powder with an average particle size of 2μm is used as the additive element. The boron powder is added to the 316L stainless steel powder at a rate of 0.5wt%. The two powders are mixed by a planetary ball mill at a speed of 150r / min for a mixing time of 240min. Stainless steel balls are used as the mixing medium, and the ball-to-powder ratio is 4:1.

[0019] In step S2, the parameters for t2 are: purging argon gas until the oxygen content drops below 8%, and heating the printing substrate to 80°C;

[0020] The laser printing parameters for t3 are: laser power 200W, scanning spacing 70μm, scanning speed 800mm / s, layer thickness 60μm, scanning strategy is checkerboard scanning, and interlayer angle is 67°.

[0021] The selective laser additive manufacturing system used in step S2 includes a chamber, a powder feeding platform, a printing platform, a powder spreading roller, a laser system, and a vacuum system. The chamber contains a powder feeding cylinder and a printing cylinder. The powder feeding platform, installed inside the powder feeding cylinder, has a lifting function and is used to place boron / stainless steel mixed powder. The printing platform, installed inside the printing cylinder, also has a lifting function and is used to place the printing substrate. The powder spreading roller, located inside the chamber, is used to spread the boron / stainless steel mixed powder from the powder feeding platform onto the printing substrate. The laser system includes a laser generator, a laser beam expanding and collimating system, a laser scanner, and a focusing lens. The laser generated by the laser generator is expanded and collimated by the laser beam expanding and collimating system. The laser scanner adjusts the laser direction according to the drawing of the boron / stainless steel skeleton. The laser, after direction adjustment, is focused by the focusing lens onto the printing substrate covered with boron / stainless steel mixed powder. The vacuum system is used to evacuate the chamber.

[0022] The chamber is also equipped with a recycling tank; the powder feeding tank, printing tank and recycling tank are arranged in sequence.

[0023] In step S4, the parameters of the ultrasonic vibration are: power 150W and frequency 20KHz.

[0024] In step S4, an ultrasonic generator is installed on the outer wall of the casting mold, and a pouring tank is set on top of it. The opening at the bottom of the casting mold is connected to a vacuum pump through a vacuum pipe, and a filter plate is installed between the vacuum pipe and the boron stainless steel frame.

[0025] The outer skin of the boron stainless steel skeleton includes a bottom surface of the skin and a side surface of the skin surrounding the edge of the bottom surface of the skin; in step S4, the bottom surface of the outer skin is opened and then placed in the casting mold.

[0026] In step S1, a QW-3SP4-1 planetary ball mill is used.

[0027] In step S2, the drawing of the boron stainless steel skeleton is an STL file exported by the Spaceclaim program. The outer skin is a cylinder with a thickness of 0.25mm, a diameter of 30mm, and a height of 10mm. The arch bridge structure is a catenary arch with an arch height of 1.125mm and a span of 3mm. The Dalian Meizhu FF-M140-H selective laser additive manufacturing system is used.

[0028] The present invention has the following beneficial effects:

[0029] This invention addresses the performance characteristics of stainless steel and aluminum alloy materials by designing an "arch-shaped" microstructure. An "arch-shaped" stainless steel skeleton is fabricated using selective laser additive manufacturing (SLA). Adding an appropriate amount of boron reduces the weight of the stainless steel skeleton without compromising its compressive strength. Molten aluminum alloy is then poured into the stainless steel skeleton using a casting method. During casting, high-frequency ultrasound is applied to improve the fluidity of the molten aluminum alloy within the skeleton, reduce internal defects in the steel-aluminum alloy, refine the aluminum alloy grains, improve the steel-aluminum interface bonding performance, and reduce internal residual stress in the steel-aluminum alloy. This method offers advantages such as material savings, low cost, good formability, and excellent steel / aluminum interface bonding. This advanced fabrication process is an ideal method for preparing high-performance steel-aluminum composite materials. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 A schematic diagram of the preparation of a boron-stainless steel skeleton for selective laser additive manufacturing equipment;

[0032] Figure 2 A schematic diagram of a boron stainless steel skeleton;

[0033] Figure 3 A schematic diagram of ultrasonic vibration-assisted casting of steel and aluminum alloys;

[0034] Figure 4 This is a schematic diagram of a steel-aluminum alloy structure with a prefabricated skeleton.

[0035] In the diagram: 101-Compartment; 102-Toner feeding platform; 103-Printing platform; 104-Toner spreading roller; 105-Vacuum system; 106-Toner feeding cylinder; 107-Printing cylinder; 108-Recovery cylinder; 109-Laser generator; 110-Laser beam expander and collimator system; 111-Laser scanner; 112-Focusing lens; 113-Laser;

[0036] 201-Casting mold; 202-Ultrasonic generator; 203-Pouring tank; 204-Vacuum pipe; 205-Vacuum pump; 206-Valve switch; 207-Filter plate;

[0037] 301 - Boron / stainless steel mixed powder; 302 - Printing substrate; 303 - Boron stainless steel skeleton; 303.1 - Outer skin; 303.2 - Arch bridge structure; 304 - Molten aluminum alloy. Detailed Implementation

[0038] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This embodiment provides a method for preparing a steel-aluminum alloy with a prefabricated skeleton. It has a wide range of applications, flexible and diverse internal microstructure designs, and a variety of skeleton and filler materials. The prepared material exhibits excellent properties and has broad application prospects. The raw materials used are: 316L stainless steel powder, aluminum alloy ingots, boron powder, argon gas, sandpaper, and alcohol. The quantities prepared are as follows: measured in pieces, millimeters, micrometers, kilograms, sheets, and liters.

[0040]

[0041] Specifically, it includes the following steps.

[0042] S1, Preparation of boron / stainless steel mixed powder

[0043] Using 316L stainless steel powder with an average particle size of 26μm as the matrix powder and boron powder with an average particle size of 2μm as the additive element, the boron powder was added to the 316L stainless steel powder at a rate of 0.5wt%. The two powders were mixed in a QW-3SP4-1 planetary ball mill at a speed of 150r / min for a mixing time of 240min. Stainless steel balls were used as the mixing medium, and the ball-to-powder ratio was 4:1.

[0044] S2, using a selective laser additive manufacturing system to prefabricate a boron stainless steel skeleton.

[0045] Selective laser additive manufacturing (SLA) technology offers advantages such as flexible product structure design, short manufacturing cycles, diverse material options, and high material utilization. It enables the design and fabrication of complex internal three-dimensional lattice structures, allowing for the preparation of various microstructures while reducing weight without compromising strength. In this embodiment, SLA is used to fabricate an "arch-shaped" microstructure, exhibiting excellent compressive strength. Adding boron to stainless steel can refine the grain size and improve its mechanical properties.

[0046] The Dalian Meizhu FF-M140-H selective laser additive manufacturing system used in this embodiment includes a chamber 101, a powder feeding platform 102, a printing platform 103, a powder spreading roller 104, a laser system, and a vacuum system 105. The chamber contains a powder feeding cylinder 106, a printing cylinder 107, and a recovery cylinder 108 arranged sequentially. The powder feeding platform 102, installed inside the powder feeding cylinder 106, has a lifting function and is used to hold boron / stainless steel mixed powder 301. The printing platform 103, installed inside the printing cylinder 107, also has a lifting function and is used to hold the printing substrate 302. The powder spreading roller 104 is located inside the chamber 101 and is used to spread the boron / stainless steel mixed powder from the powder feeding platform 102. The boron / stainless steel mixed powder 301 is spread onto the printing substrate 302, and the excess boron / stainless steel mixed powder 301 is sent to the recycling tank 108; the laser system includes a laser generator 109, a laser beam expanding and collimating system 110, a laser scanner 111, and a focusing lens 112; the laser 113 generated by the laser generator 109 is expanded and collimated by the laser beam expanding and collimating system 110, and the laser scanner 111 adjusts the laser direction according to the drawing of the boron / stainless steel skeleton 303. The laser 113 after adjustment is focused by the focusing lens 112 onto the printing substrate 302 on which the boron / stainless steel mixed powder 301 is spread; the vacuum system 105 is used to evacuate the chamber 101.

[0047] Step S2 specifically includes the following processes:

[0048] t1, the printing substrate 302 is installed on the printing platform 103 of the selective laser additive manufacturing system, the boron / stainless steel mixed powder 301 is placed on the powder feeding platform 102 of the selective laser additive manufacturing system, and the chamber is closed;

[0049] t2, Evacuate the vacuum, introduce argon gas until the oxygen content drops below 8%, and heat the printing substrate to 302 to 80°C;

[0050] t3. Import the drawing of boron stainless steel skeleton 303. The boron stainless steel skeleton 303 in the drawing includes an outer skin 303.1 and an arch bridge structure 303.2. Multiple arch bridge structures 303.2 are arranged in a preset array inside the outer skin 303.1. In this embodiment, the outer skin 303.1 is a cylindrical part with a closed bottom and an open top, with a thickness of 0.25mm, a diameter of 30mm, and a height of 10mm. The arch bridge structure 303.2 can be a circular arch, a parabolic arch, or a catenary arch. In this embodiment, the arch bridge structure 303.2 is a catenary arch with an arch height of 1.125mm and a span of 3mm. Slice the drawing and set the laser printing parameters: laser power 200W, scanning spacing 70μm, scanning speed 800mm / s, layer thickness 60μm, scanning strategy is checkerboard scanning, and interlayer angle 67°.

[0051] t4, the powder spreading roller 104 spreads the boron / stainless steel mixed powder 301 on the powder feeding platform 102 onto the printing substrate 302;

[0052] t5, Perform single-layer laser printing according to the laser printing parameters set in step t3;

[0053] At t6, the printing platform 103 descends, and the descent height is equal to the thickness of the boron / stainless steel mixed powder 301 on the printing substrate 302 in t4.

[0054] t7, repeat steps t4-t6 to print the boron stainless steel skeleton 303 layer by layer.

[0055] S3 uses an abrasive waterjet polishing boron stainless steel frame.

[0056] The boron stainless steel skeleton 303 printed in step S2 is placed in a polishing instrument. When compressed air is ejected at high speed through the nozzle on the spray gun, a negative pressure is generated at the nozzle. This causes the polishing liquid containing fine abrasive particles, which is stirred in the liquid tank, to be drawn into the spray gun through the inlet pipe, thus forming a high-speed jet that is sprayed onto the surface of the boron stainless steel skeleton 303. The high-speed collision between the abrasive particles and the surface of the boron stainless steel skeleton 303 causes a rapid concentration and change of local stress in the skeleton, resulting in erosion and shearing, thereby achieving material removal. During the polishing process, the high-speed abrasive particles act like a flexible cutting tool, cutting and machining the surface of the boron stainless steel skeleton 303, thus making the surface smooth.

[0057] S4 uses ultrasonic vibration-assisted casting of steel and aluminum alloys.

[0058] An ultrasonic generator 202 is installed on the outer wall of the casting mold 201, and a pouring tank 203 is set on top of it. The pouring tank 203 contains molten aluminum alloy 304 obtained by heating aluminum alloy ingots in a crucible. The lower opening of the casting mold 201 is connected to a vacuum pump 205 through a vacuum pipe 204. A valve switch 206 is set on the vacuum pipe 204.

[0059] Using the boron stainless steel skeleton 303 prepared in step S2 as the filling substrate, the bottom surface of the outer skin 303.1 is perforated and placed inside the casting mold 201. A filter plate 207 is installed between the vacuum pipe 204 and the boron stainless steel skeleton 303. Molten aluminum alloy 304 is poured from above the boron stainless steel skeleton 303 downwards, while ultrasonic vibration is performed and a vacuum is drawn from below the boron stainless steel skeleton 303 until the molten aluminum alloy 304 completely fills the boron stainless steel skeleton 303. After the aluminum alloy cools, the ultrasonic vibration and vacuum are turned off, and the casting mold 201 is disassembled. The steel-aluminum alloy with the pre-fabricated skeleton is now complete. The filter plate 207 effectively filters the molten aluminum alloy 304, preventing it from being drawn away during the vacuuming process.

[0060] S5, storage

[0061] Steel-aluminum alloys packaged with soft materials should be stored in a clean, dry environment, protected from moisture, sunlight, and acid, alkali, and salt corrosion. The storage temperature should be 20℃ and the relative humidity ≤10%.

[0062] Conclusion: The above method designs an "arch-shaped" microstructure, which reduces weight and saves raw materials without compromising strength. A boron-added stainless steel skeleton structure with good compressive strength was prepared using selective laser additive manufacturing. A steel-aluminum composite material was prepared by filling the stainless steel skeleton with aluminum alloy through casting. Applying high-frequency ultrasound during casting helps refine the grain size of the aluminum alloy, reduce defects during solidification, accelerate the flow of molten aluminum alloy, and improve the interfacial bonding performance between aluminum and steel. This advanced preparation method is an ideal approach for preparing high-performance composite materials.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a steel-aluminum alloy with a prefabricated skeleton, characterized in that, Includes the following steps: S1, Preparation of boron / stainless steel mixed powder Stainless steel powder and boron powder were ball-milled and mixed to prepare boron / stainless steel mixed powder; S2, using a selective laser additive manufacturing system to prefabricate a boron stainless steel skeleton. t1, mount the printing substrate on the printing platform of the selective laser additive manufacturing system, place the boron / stainless steel mixed powder on the powder feeding platform of the selective laser additive manufacturing system, and close the chamber; t2, Evacuate the vacuum, introduce argon gas, and heat the printing substrate; t3, import the drawing of boron stainless steel skeleton. The boron stainless steel skeleton in the drawing includes an outer skin and an arch bridge structure. Multiple arch bridge structures are arranged in a preset array inside the outer skin. Slice the drawing and set the laser printing parameters. t4, the powder spreading roller spreads the boron / stainless steel mixed powder from the powder feeding platform onto the printing substrate; t5, Perform single-layer laser printing according to the laser printing parameters set in step t3; At t6, the printing platform descends to a height equal to the thickness of the boron / stainless steel mixed powder on the printing substrate during t4. t7, repeat steps t4-t6 to print the boron stainless steel skeleton layer by layer; S3 uses an abrasive waterjet polishing boron stainless steel frame. S4 uses ultrasonic vibration-assisted casting of steel and aluminum alloys. The boron stainless steel skeleton prepared in step S2 is placed in a casting mold, and aluminum alloy molten liquid is poured from above the boron stainless steel skeleton downwards. At the same time, ultrasonic vibration is performed and a vacuum is drawn below the boron stainless steel skeleton until the aluminum alloy molten liquid fills the boron stainless steel skeleton. After the aluminum alloy cools, the ultrasonic vibration and vacuum are turned off, and the steel-aluminum alloy with the prefabricated skeleton is completed.

2. The method for preparing a steel-aluminum alloy with a prefabricated skeleton according to claim 1, characterized in that, In step S1, 316L stainless steel powder with an average particle size of 26μm is used as the matrix powder, and boron powder with an average particle size of 2μm is used as the additive element. The boron powder is added to the 316L stainless steel powder at a rate of 0.5wt%. The two powders are mixed by a planetary ball mill at a speed of 150r / min for a mixing time of 240min. Stainless steel balls are used as the mixing medium, and the ball-to-powder ratio is 4:

1.

3. The method for preparing a steel-aluminum alloy with a prefabricated skeleton according to claim 1, characterized in that, In step S2, the parameters for t2 are: argon gas is introduced until the oxygen content is reduced to below 8%, and the printing substrate 302 is heated to 80°C; The laser printing parameters for t3 are: laser power 200W, scanning spacing 70μm, scanning speed 800mm / s, layer thickness 60μm, scanning strategy is checkerboard scanning, and interlayer angle is 67°.

4. The method for preparing a steel-aluminum alloy with a prefabricated skeleton according to claim 3, characterized in that, The selective laser additive manufacturing system used in step S2 includes a chamber, a powder feeding platform, a printing platform, a powder spreading roller, a laser system, and a vacuum system. The chamber is equipped with a powder delivery cylinder and a printing cylinder; The powder feeding platform is installed inside the powder feeding cylinder and has a lifting function for placing boron / stainless steel mixed powder; The printing platform is installed inside the printing cylinder and has a lifting function for placing the printing substrate; The powder spreading roller is located in the chamber and is used to spread the boron / stainless steel mixed powder on the powder feeding platform onto the printing substrate. The laser system includes a laser generator, a laser beam expanding and collimating system, a laser scanner, and a focusing lens. The laser generated by the laser generator is expanded and collimated by the laser beam expanding and collimating system. The laser scanner adjusts the laser direction according to the drawing of the boron stainless steel skeleton. The laser with the adjusted direction is focused by the focusing lens onto the printing substrate covered with boron / stainless steel mixed powder. The vacuum system is used to evacuate the compartment.

5. The method for preparing a steel-aluminum alloy with a prefabricated skeleton according to claim 4, characterized in that, The chamber is also equipped with a recycling tank; The powder feeding cylinder, printing cylinder, and recycling cylinder are arranged in sequence.

6. The method for preparing a steel-aluminum alloy with a prefabricated skeleton according to claim 1, characterized in that, In step S4, the parameters of the ultrasonic vibration are: power 150W and frequency 20KHz.

7. The method for preparing a steel-aluminum alloy with a prefabricated skeleton according to claim 1 or 6, characterized in that, In step S4, an ultrasonic generator is installed on the outer wall of the casting mold, and a pouring tank is set on top of it. The opening at the bottom of the casting mold is connected to a vacuum pump through a vacuum pipe, and a filter plate is installed between the vacuum pipe and the boron stainless steel frame.

8. The method for preparing a steel-aluminum alloy with a prefabricated skeleton according to claim 7, characterized in that, The outer skin of the boron stainless steel skeleton includes the bottom surface of the skin and the side surface of the skin surrounding the edge of the bottom surface of the skin; In step S4, the bottom surface of the outer skin is perforated and then placed in the casting mold.

9. The method for preparing a steel-aluminum alloy with a prefabricated skeleton according to claim 1, characterized in that, In step S1, a QW-3SP4-1 planetary ball mill is used; In step S2, the drawing of the boron stainless steel skeleton is an STL file exported by the Spaceclaim program. The outer skin is a cylinder with a thickness of 0.25mm, a diameter of 30mm, and a height of 10mm. The arch bridge structure is a catenary arch with an arch height of 1.125mm and a span of 3mm. The Dalian Meizhu FF-M140-H selective laser additive manufacturing system is used.

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