A method of producing closed-cell foam steel using a laser additive manufacturing technique

Abstract

The application relates to a method for preparing closed-cell foam steel by a laser additive manufacturing technology and belongs to the field of additive manufacturing forming technology. The method comprises the following steps: fully mixing steel powder and Cr2N powder to obtain mixed powder; taking the mixed powder as raw material, selecting laser processing parameters and scanning tracks according to size requirements, inputting into a corresponding laser processing operation system, obtaining two-dimensional information, carrying out laser additive manufacturing, and obtaining the closed-cell foam steel. The application develops a new laser preparation method of closed-cell foam steel, realizes the preparation of the closed-cell foam steel by using the program setting of a laser and the scanning of a laser beam, the aperture of the closed-cell foam steel is generally less than 500 mu m, the harm problem of residues caused by conventional casting foam steel and sintering method for manufacturing foam steel is avoided, meanwhile, the design is more free, the environment is harmless, the limitation of a mold is broken, and the flexibility and flexibility of the manufactured closed-cell foam steel are greatly increased.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a method for preparing closed-cell foam steel using laser additive manufacturing technology. Background Technology

[0002] Foamed steel is a structural-functional integrated material with a steel matrix containing a large number of interconnected or non-interconnected pores. It possesses properties such as sound absorption, heat insulation, flame retardancy, and electromagnetic shielding. Foamed steel is divided into closed-cell and open-cell types. Among them, closed-cell foamed steel has unique applications in many fields such as heat insulation and energy absorption. However, traditional manufacturing methods mainly use molding, lamination, and sintering methods, which have certain drawbacks. For example, the molding method is limited by the size of the mold; chemical residues may remain when using powder metallurgy sintering; and the lamination method is only suitable for manufacturing simple shapes of laminates, and it is difficult to manufacture slightly complex shapes. Therefore, people have been looking for suitable, convenient, and quick manufacturing methods.

[0003] Laser additive manufacturing (LAM) is a new technology that enables modular, rapid, near-net-shape forming of high-performance, dense metal parts. It combines modern materials technology, laser technology, and rapid prototyping, offering advantages such as the ability to form complex structural parts, reduce machining steps, shorten processing cycles, and achieve near-net-shape forming. In recent years, LAM has experienced rapid development, demonstrating unique advantages in fabricating complex-shaped components, designing compositional gradients, and customizing microstructures and properties, thus becoming a rising star in the manufacturing industry. If LAM can be used to prepare closed-cell foam steel, its design and manufacturing will become simpler and more flexible, further expanding the applications of functional foam steel. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing closed-cell foam steel using laser additive manufacturing technology. The method involves laser additive manufacturing a homogeneous mixture of steel powder and Cr2N powder in a specific ratio, layer by layer, to obtain foam steel. This makes the design and manufacturing of closed-cell foam steel simpler and more flexible.

[0005] This invention is achieved through the following technical solution:

[0006] The first objective of this invention is to provide a method for preparing closed-cell foam steel using laser additive manufacturing technology, comprising the following steps:

[0007] S1: Thoroughly mix steel powder and Cr2N powder to obtain a mixed powder;

[0008] S2: Using the mixed powder obtained in step S1 as raw material, select laser processing parameters and scanning trajectory according to size requirements, and input them into the corresponding laser processing operating system to obtain two-dimensional information, and perform laser additive manufacturing to obtain the closed-cell foam steel.

[0009] In one embodiment of the present invention, in step S1, the steel powder is selected from stainless steel powder and / or mold steel powder.

[0010] In one embodiment of the present invention, the stainless steel powder includes one or more of 316L, 304L, and 420 stainless steel; the mold steel powder includes H13 mold steel.

[0011] In one embodiment of the present invention, in step S1, the content of Cr2N powder in the mixed powder is ≤20wt% (greater than 0); preferably, the content of Cr2N powder in the mixed powder is 5wt% to 20wt%.

[0012] In one embodiment of the present invention, in step S1, the mixing method is: to fully mix by ball milling.

[0013] In one embodiment of the present invention, argon or acetone is introduced during the ball milling process; the rotational speed of the ball mill is preferably selected such that the surface temperature of the ball mill jar does not exceed 100°C during operation.

[0014] In one embodiment of the present invention, the ball milling speed is 50 r / min-100 r / min; the ball milling time is 1 h-3 h, so as to ensure that the Cr2N powder and steel powder are fully / uniformly mixed.

[0015] In one embodiment of the present invention, step S2 of the laser additive manufacturing includes the following steps:

[0016] Using a powder feeding mechanism, the mixed powder is transported to a designated area, and a laser is used to scan based on the two-dimensional information to melt and sinter the mixed powder transported to the designated area; the feeding and melting / sintering operations are repeated or continued until the closed-cell foam steel is obtained.

[0017] In one embodiment of the present invention, the scanning is performed under a protective atmosphere, which may be argon.

[0018] In one embodiment of the present invention, the melting and sintering is performed using selective laser melting or direct laser deposition.

[0019] In one embodiment of the present invention, the processing parameters for laser selective melting are as follows: a YAG (yttrium aluminum garnet) laser, a fiber laser, or a semiconductor laser is used; the laser scanning rate is 40 mm / min-200 mm / min; the laser power is 80 W-300 W; and the thickness of the mixed powder delivered each time is 0.2 mm-0.5 mm.

[0020] In one embodiment of the present invention, the processing parameters for laser direct deposition are: laser scanning speed 80mm / min-240mm / min, powder feed rate 3g / min-51g / min, overlap rate 20%-50%, and laser power 1000W-2500W.

[0021] A second objective of this invention is to provide closed-cell foam steel prepared by the method.

[0022] The technical solution of the present invention has the following advantages compared with the prior art:

[0023] 1. This invention provides a method for preparing closed-cell foam steel using laser additive manufacturing technology. A new laser preparation method for closed-cell foam steel is developed. By optimizing process parameters, controlling power and scanning speed, a physical form of closed-cell foam steel is obtained. The preparation of closed-cell foam steel is achieved by using laser program settings and laser beam scanning. The pore size is generally within 500 μm.

[0024] 2. This invention premixes steel powder with Cr2N powder, using inexpensive and readily available Cr2N powder as a foaming agent. No other components need to be added, and the residues do not adversely affect the steel, avoiding the harmful residue problems caused by conventional casting and sintering methods for manufacturing foam steel. Simultaneously, the flexibility of laser additive manufacturing technology solves the drawback of lamination methods in manufacturing complex shapes, allowing for greater design freedom. Furthermore, conventional casting methods require vacuum or auxiliary substances such as pore-forming agents, which are environmentally harmful. This invention uses a laser under argon protection, eliminating the need for a vacuum. Conventional software programming, program settings, and laser beam scanning are used to create porous structures, overcoming mold limitations and greatly increasing manufacturing flexibility and adaptability. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0026] Example 1

[0027] This embodiment provides a method for preparing closed-cell foam steel using laser additive manufacturing technology, wherein commercially available 316L stainless steel powder is selected, and the Cr2N powder purity is greater than 99.9%; specifically, the method includes the following steps:

[0028] (a) Mix 316L stainless steel powder with Cr2N powder; wherein the Cr2N powder accounts for 5% by weight.

[0029] (b) Place the mixed 316L stainless steel powder and Cr2N powder in a ball mill, introduce argon gas for ball milling, the ball mill speed is 50 r / min, the ball milling time is 1 h, so as to ensure that the Cr2N powder and stainless steel powder are fully / uniformly mixed to obtain mixed powder.

[0030] (c) Based on the required pore size of the closed-pore stainless steel, commercial software is used for pore design, which is then input into the corresponding laser processing operating system to obtain the two-dimensional information of the closed-pore stainless steel for rapid fabrication. This rapid fabrication specifically involves: using a powder feeding mechanism to transport the mixed powder to a designated area and compact it; simultaneously, a laser, under computer control and based on the designed two-dimensional information, scans the powder material under argon protection, melting the pre-placed powder material; then, the powder feeding / compaction, melting, and sintering process is repeated until the desired sample is obtained. During the scanning process, linear irradiation is performed, with a laser beam scanning rate of 42 mm / min; the thickness of each compacted powder layer is 0.2 mm; the laser used is a YAG or fiber laser with a laser power of 100 W.

[0031] Experimental tests showed that the porosity of the closed-cell stainless steel produced by the method of this embodiment was 7.25%, and the micropore diameter was between 2μm and 3μm.

[0032] Example 2

[0033] This embodiment provides a method for preparing closed-cell foam steel using laser additive manufacturing technology. The Cr2N powder has a purity greater than 99.9%, and the steel powder is made of 420 stainless steel. The specific steps include:

[0034] (a) Mix 420 stainless steel powder with Cr2N powder, wherein the Cr2N powder accounts for 10% of the total mass;

[0035] (b) The mixed 420 stainless steel powder and Cr2N powder were placed in a ball mill and argon gas was introduced for ball milling. The ball mill speed was 100 r / min and the ball milling time was 2 h to ensure that the Cr2N powder and the 420 stainless steel powder were fully / uniformly mixed to obtain mixed powder.

[0036] (c) Based on the required overall dimensions of the closed-cell foam steel, commercial software was used for pore design, and the results were input into the corresponding laser processing operating system to obtain the two-dimensional information of the closed-cell stainless steel 420 entity for rapid fabrication. This rapid fabrication involved: using a powder feeding mechanism to deliver the mixed powder to a designated area and compact it; simultaneously, a laser, under computer control and based on the designed two-dimensional information, scanned the powder under argon protection, melting the pre-placed powder material. This process was repeated—powder feeding / compacting, melting and sintering—until the desired sample was obtained. Linear irradiation was performed at a laser beam scanning rate of 150 mm / min; the compacted powder layer thickness was 0.4 mm; and a YAG or fiber laser with a laser power of 290 W was used.

[0037] Experimental tests showed that the porosity of the closed-cell 420 stainless steel produced using the method of this embodiment was 11.5%, and the micropore diameter was between 3μm and 5μm.

[0038] Example 3

[0039] This embodiment provides a method for preparing closed-cell foam steel using laser additive manufacturing technology, employing H13 mold steel powder and Cr2N powder with a purity greater than 99.9%, specifically including the following steps:

[0040] (a) H13 mold steel powder is mixed with Cr2N powder, wherein the Cr2N powder accounts for 15% of the total mass;

[0041] (b) The H13 mold steel powder and Cr2N powder were placed in a ball mill and argon gas was introduced for ball milling. The ball mill speed was 80 r / min and the ball milling time was 3 h to ensure that the Cr2N powder and H13 mold steel powder were fully / uniformly mixed to obtain mixed powder.

[0042] (c) Based on the required dimensions of the H13 mold steel, parameters were selected using commercial software and input into the corresponding laser processing operating system to obtain the two-dimensional information of the closed-cell H13 mold steel, and then rapidly fabricated. This rapid manufacturing process specifically involves: using a powder feeding mechanism to transport the mixed powder to a designated area, and simultaneously performing laser melting (using laser direct deposition additive manufacturing technology). Simultaneously, under computer control, a laser scans the material according to the designed two-dimensional information under argon protection, melting and sintering the powder. This process is repeated until the desired sample is obtained. The laser used is a semiconductor laser with a speed of 200 mm / min, a powder feed rate of 10 g / min, an overlap rate of 25%, and a laser power of 1500 W.

[0043] Experimental tests showed that the porosity of the closed-cell H13 mold steel manufactured using the method of this embodiment was 13.56%, and the micropore diameter was between 5μm and 6μm.

[0044] Example 4

[0045] This embodiment provides a method for preparing closed-cell foam steel using laser additive manufacturing technology, employing H13 mold steel powder and Cr2N powder with a purity greater than 99.9%, specifically including the following steps:

[0046] (a) Mix H13 mold steel powder with Cr2N powder; wherein, Cr2N powder accounts for 20% of the total mass;

[0047] (b) The H13 mold steel powder and Cr2N powder were placed in a ball mill and argon gas was introduced for ball milling. The ball mill speed was 80 r / min and the ball milling time was 2.6 h to ensure that the Cr2N powder and H13 mold steel powder were fully / uniformly mixed to obtain mixed powder.

[0048] (c) Based on the required dimensions of the H13 mold steel, parameters are selected using commercial software and input into the corresponding laser processing operating system to obtain the two-dimensional information of the closed-cell H13 mold steel, and then rapidly manufactured. This rapid manufacturing process involves: using a powder feeding mechanism to transport the mixed powder to a designated area, and simultaneously performing laser melting (using micro-laser energy direct deposition additive manufacturing technology). Simultaneously, under computer control, a laser scans the material according to the designed two-dimensional information under argon protection, melting and sintering. This process is repeated until the desired sample is obtained. Linear irradiation is performed using a semiconductor laser with a speed of 80 mm / min, a powder feed rate of 40 g / min, an overlap rate of 40%, and a laser power of 2300 W.

[0049] Experimental tests showed that the porosity of the closed-cell H13 mold steel produced using the method of this embodiment was 15%, and the micropore diameter was between 6μm and 7μm.

[0050] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing closed-cell foam steel using laser additive manufacturing technology, characterized in that, Includes the following steps, S1: Thoroughly mix steel powder and Cr2N powder to obtain a mixed powder; S2: Using the mixed powder obtained in step S1 as raw material, select laser processing parameters and scanning trajectory according to size requirements, and input them into the corresponding laser processing operating system to obtain two-dimensional information, perform laser additive manufacturing, and obtain the closed-cell foam steel. In step S1, the steel powder is selected from stainless steel powder and / or mold steel powder; In step S1, the content of Cr2N powder in the mixed powder is ≤20 wt%.

2. The method according to claim 1, characterized in that, In step S1, the mixing method is to use ball milling to mix thoroughly.

3. The method according to claim 2, characterized in that, Argon or acetone is introduced during the ball milling process.

4. The method according to claim 1, characterized in that, In step S2, the laser additive manufacturing includes the following steps: Using a powder feeding mechanism, the mixed powder is transported to a designated area, and a laser is used to scan based on the two-dimensional information to melt and sinter the mixed powder transported to the designated area; the feeding and melting / sintering operations are repeated or continued until the closed-cell foam steel is obtained.

5. The method according to claim 4, characterized in that, The melting and sintering process employs selective laser melting or direct laser deposition.

6. The method according to claim 5, characterized in that, The processing parameters for laser selective melting are: laser scanning rate of 40 mm / min-200 mm / min, laser power of 80 W-300 W, and thickness of mixed powder conveyed each time of delivery of 0.2 mm-0.5 mm.

7. The method according to claim 5, characterized in that, The processing parameters for laser direct deposition are: laser scanning speed 80 mm / min-240 mm / min, powder feed rate 3 g / min-51 g / min, overlap rate 20%-50%, and laser power 1000 W-2500 W.

8. Closed-cell foam steel prepared by any one of claims 1-7.