Closed-cell foam steel and preparation method thereof

Abstract

The present invention belongs to the field of additive manufacturing forming technology, and specifically relates to a closed-cell foam steel and a preparation method thereof. The preparation method comprises the following steps: mixing steel powder and magnesium powder or magnesium alloy powder to obtain a mixed powder, wherein the mass percentage of magnesium powder or magnesium alloy powder in the mixed powder is 2-7%; ball milling the mixed powder to obtain a powder raw material; using laser selective melting technology or laser direct deposition technology, the powder raw material is subjected to additive manufacturing processing to obtain the closed-cell foam steel. The present invention develops a new laser preparation method for closed-cell foam steel, which realizes the preparation of closed-cell foam steel by using the program setting of the laser and the scanning of the laser beam, and the pore size is generally within 120 μm; it avoids the hazard problem of residues caused by conventional casting foam steel and sintering method for manufacturing foam steel; at the same time, the design is more free, harmless to the environment, breaking through the limitation of the mold, and the flexibility and flexibility of manufacturing are greatly increased.

Description

Technical Field

[0001] The invention belongs to the field of additive manufacturing, and in particular relates to a closed-cell foam steel and a preparation method thereof. Background Art

[0002] Closed-cell foam steel has unique applications in many fields such as thermal insulation and energy absorption, but the traditional preparation method has certain problems. For example, the mold size is limited when the mold method is used for manufacturing; there are chemical residues when the powder metallurgy sintering method is used; when the lamination method is used, it is only suitable for manufacturing simple shapes of laminated boards, and it is difficult to prepare slightly complex shapes. For this reason, people have been looking for a suitable, convenient and fast preparation method.

[0003] In recent years, laser additive manufacturing technology has developed rapidly. This technology has unique advantages in preparing parts with complex shapes, designing composition gradients, and customizing organization and performance, making it a new favorite in the manufacturing industry.

[0004] Among the existing preparation technologies of foam steel, most of them use mold method, lamination method and sintering method, etc., and laser additive manufacturing technology is rarely used for preparation. If laser additive manufacturing technology can be used to prepare closed-cell foam steel, the design and manufacture of closed-cell foam steel will be simpler and freer, so that the application of functional foam steel can be further developed. Summary of the invention

[0005] The present invention aims to provide a closed-cell foam steel and a preparation method thereof, which has no toxic or harmful substance residues, is not restricted by molds and does not require vacuum casting, can be applied to industries such as construction and engineering, and greatly improves the service life of the product.

[0006] According to the technical solution of the present invention, the method for preparing the closed-cell foam steel comprises the following steps:

[0007] S1: mixing steel powder and magnesium powder or magnesium alloy powder to obtain a mixed powder, wherein the mass percentage of the magnesium powder or magnesium alloy powder in the mixed powder is 2-7%;

[0008] S2: ball milling the mixed powder to obtain a powder raw material;

[0009] S3: According to the size requirements, laser processing parameters and scanning trajectories are selected and input into the corresponding laser processing operating system to obtain two-dimensional information; laser selective melting technology or laser direct deposition technology is used to perform additive manufacturing processing using the powder raw material to obtain the closed-cell foam steel.

[0010] Furthermore, in step S2, the mixed powder is placed in a ball mill for ball milling, and the ball milling time is 1-3 hours to ensure sufficient and uniform mixing of the steel powder and the Mg powder or the magnesium alloy powder; the ball mill speed is selected so that the surface temperature of the ball mill jar does not exceed 60°C during operation; specifically, the ball mill speed is 50-100r / min.

[0011] Furthermore, argon or acetone is introduced during the ball milling process.

[0012] Furthermore, in step S2, the specific operation of using laser selective melting technology for additive manufacturing is: using a powder feeding mechanism to transport part of the powder raw material to a designated area and compact it; at the same time, under a protective atmosphere, using a laser to scan according to the two-dimensional information to melt the preset powder raw material; repeating the powder feeding, compacting and melting processes until the closed-cell foam steel is obtained.

[0013] Specifically, a YAG (yttrium aluminum garnet crystal) laser, a fiber laser or a semiconductor laser is used, and the protective atmosphere may be argon.

[0014] Furthermore, the scanning rate is 40-200 mm / min, and the laser power is 80-300 W.

[0015] Furthermore, after compaction, the thickness of each layer of the powder material is 0.2-0.5 mm.

[0016] Furthermore, in step S2, the specific operation of using laser direct deposition technology for additive manufacturing is: using a powder feeding mechanism to continuously transport the powder raw material to the molten pool; at the same time, under a protective atmosphere (argon), using a laser to scan according to the two-dimensional information, melt and sinter until the closed-cell foam steel is obtained.

[0017] Furthermore, the powder feeding mechanism has a powder feeding rate of 3-51 g / min.

[0018] Furthermore, the scanning rate is 80-240 mm / min, the overlap rate is 20-50%, and the laser power is 1000-2500W.

[0019] Another aspect of the present invention provides closed-cell foam steel obtained by the above preparation method.

[0020] The technical solution of the present invention has the following advantages compared with the prior art:

[0021] 1. The present invention develops a new laser preparation method for closed-cell foam steel. By optimizing process parameters, controlling power and scanning speed, a closed-cell foam steel entity is obtained. The preparation of closed-cell foam steel is achieved by using the program setting of the laser and the scanning of the laser beam. The pore size is generally within 120 μm.

[0022] 2. The present invention premixes steel powder, magnesium powder or magnesium alloy powder, and uses magnesium powder or magnesium alloy powder as a foaming agent, without adding other components, and the residue has no adverse effect on the steel, thus avoiding the harmful problems of residues caused by conventional casting of foam steel and sintering method for manufacturing foam steel; at the same time, the flexibility of laser additive manufacturing technology solves the problem that the lamination method is not easy to manufacture parts with complex shapes, thereby making the design more free; at the same time, conventional casting methods require the use of vacuum, or the use of auxiliary substances such as pore-forming agents, which are harmful to the environment; at the same time, the laser is used under argon protection, without the need for vacuum, and conventional software programming, program setting, and laser beam scanning are used to prepare porous materials, breaking through the limitations of the mold, and greatly increasing the flexibility and flexibility of manufacturing. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0024] Embodiment 1

[0025] A laser preparation method for closed-cell foam steel, using commercial 316L stainless steel powder and Mg powder, wherein the purity of the Mg powder is greater than 99.0%. The method comprises the following steps:

[0026] (a) 316L stainless steel powder was mixed with Mg powder, wherein Mg powder accounted for 2% of the total mass;

[0027] (b) The mixed 316L stainless steel powder and Mg powder were placed in a ball mill and argon gas was introduced for ball milling at a speed of 50 r / min for 1 h to ensure that the Mg powder and the stainless steel powder were fully / uniformly mixed.

[0028] (c) According to the pore size of the closed-cell stainless steel to be prepared, commercial software is selected for pore design and input into the corresponding laser processing operating system to obtain the two-dimensional information of the closed-cell stainless steel and perform rapid preparation; the so-called rapid manufacturing is specifically: using the powder feeding mechanism to transport the mixed powder to the designated area and compact it, while using the laser to scan under argon protection according to the designed two-dimensional information under the control of the computer, melt the preset powder material, and then feed / compact, melt and sinter, and repeat this process until the required sample is obtained. Linear irradiation is performed, and the laser beam scanning rate is 42mm / min; the thickness of each layer of the compacted powder is 0.25mm, the laser used is YAG, and the laser power is 105W. The prepared micropores are 10-17μm.

[0029] Experimental tests show that the micropore diameter of the closed-cell stainless steel manufactured by the method of this embodiment is about 10-17 μm.

[0030] Embodiment 2

[0031] A laser preparation method for closed-cell foam steel, wherein the steel powder is 420 stainless steel, and the analytical pure magnesium alloy powder is Mg-1Al magnesium alloy powder, wherein the Al content in the powder is 1wt%, and the method comprises the following steps:

[0032] (a) Commercial 420 stainless steel gold powder was mixed with Mg-1Al magnesium alloy powder, where Mg powder accounted for 3.5% of the total mass;

[0033] (b) The mixed 420 stainless steel powder and Mg-1Al powder were placed in a ball mill and argon gas was introduced for ball milling at a speed of 100 r / min for 2 h to ensure that the Mg-1Al powder and the stainless steel 420 powder were fully / uniformly mixed.

[0034] (c) According to the overall size requirements of the closed-cell foam steel to be prepared, commercial software is selected for pore design and input into the corresponding laser processing operating system to obtain the two-dimensional information of the closed-cell stainless steel 420 entity and to prepare it quickly; the so-called rapid manufacturing is specifically: using the powder feeding mechanism to transport the mixed powder to the designated area and compact it, and at the same time using the laser to scan under the protection of argon gas according to the designed two-dimensional information under the control of the computer, melt the preset powder material, and then feed / compact, melt and sinter, and repeat this process until the required sample is obtained. Linear irradiation is performed, and the laser beam scanning rate is 160mm / min; the thickness of each layer of compacted powder is 0.35mm, and the laser used is a fiber laser with a laser power of 290W.

[0035] According to experimental tests, the diameter of the closed-pore 420 stainless steel produced by the method of this embodiment is between 22 and 38 μm.

[0036] Embodiment 3

[0037] A laser preparation method for closed-cell foam steel, wherein the steel powder is 420 stainless steel, and the analytical pure magnesium alloy powder is Mg-1Al magnesium alloy powder, wherein the Al content in the powder is 1wt%, and the method comprises the following steps:

[0038] (a) Commercial 420 stainless steel gold powder was mixed with Mg-1Al magnesium alloy powder, where Mg powder accounted for 4.5% of the total mass;

[0039] (b) The mixed 420 stainless steel powder and Mg-1Al powder were placed in a ball mill and acetone was introduced for ball milling at a speed of 100 r / min for 2 h to ensure that the Mg-1Al powder and the stainless steel 420 powder were fully / uniformly mixed.

[0040] (c) According to the overall size requirements of the closed-cell foam steel to be prepared, commercial software is selected for pore design and input into the corresponding laser processing operating system to obtain the two-dimensional information of the closed-cell stainless steel 420 entity and to prepare it quickly; the so-called rapid manufacturing is specifically: using the powder feeding mechanism to transport the mixed powder to the designated area and compact it, and at the same time using the laser to scan under the protection of argon gas according to the designed two-dimensional information under the control of the computer, melt the preset powder material, and then feed / compact, melt and sinter, and repeat this process until the required sample is obtained. Linear irradiation is performed, and the laser beam scanning rate is 160mm / min; the thickness of each layer of compacted powder is 0.35mm, and the laser used is a fiber laser with a laser power of 290W.

[0041] According to experimental tests, the diameter of the closed-cell pores of 420 stainless steel manufactured by the method of this embodiment is between 35 and 50 μm.

[0042] Embodiment 4

[0043] A laser preparation method for closed-cell foam steel, using H13 mold steel powder and Mg-Ca powder, wherein the mass ratio of Ca is 0.6%, comprises the following steps:

[0044] (a) H13 die steel powder was mixed with Mg-Ca powder, wherein Mg powder accounted for 5.5% of the total mass;

[0045] (b) The mixed H13 mold steel powder and Mg-Ca powder were placed in a ball mill and argon gas was introduced for ball milling at a speed of 80 r / min for 3 h to ensure that the Mg-Ca powder and the H13 mold steel powder were fully / uniformly mixed.

[0046] (c) According to the size requirements of the H13 mold steel to be prepared, commercial software is used to select parameters and input them into the corresponding laser processing operating system to obtain the two-dimensional information of the closed-cell H13 mold steel and perform rapid preparation; the so-called rapid manufacturing is specifically: using the powder feeding mechanism to transport the mixed powder to the designated area, and laser melting is performed while the powder is being transported (this is laser direct deposition additive manufacturing technology), and at the same time, the laser is used to scan, melt and sinter under argon protection according to the designed two-dimensional information under the control of the computer, and repeat this process until the required sample is obtained. The laser used is a semiconductor laser. The speed is 200mm / min, the powder feeding rate is 10g / min, the overlap rate is 25%, and the laser power is 1500W.

[0047] According to experimental tests, the hole diameter of the closed-cell H13 die steel manufactured by the method of this embodiment is between 70 and 89 μm.

[0048] Embodiment 4

[0049] A laser preparation method for closed-cell foam steel, using H13 die steel powder and Mg-Zr magnesium alloy powder, wherein the mass ratio of Zr is 1.5%, comprises the following steps:

[0050] (a) H13 die steel powder was mixed with Mg-Zr powder, wherein Mg powder accounted for 6.5% of the total mass;

[0051] (b) The mixed H13 mold steel powder and Mg-Zr powder were placed in a ball mill and argon gas was introduced for ball milling at a speed of 80 r / min for 2.6 h to ensure that the Mg-Zr powder and the H13 mold steel powder were fully / uniformly mixed.

[0052] (c) According to the size requirements of the H13 mold steel to be prepared, commercial software is used to select parameters and input them into the corresponding laser processing operating system to obtain the two-dimensional information of the closed-cell H13 mold steel and perform rapid preparation; the so-called rapid manufacturing is specifically: using the powder feeding mechanism to transport the mixed powder to the designated area, and laser melting is performed while the powder is being transported (this is the laser energy direct deposition additive manufacturing technology), and at the same time, the laser is used to scan, melt and sinter under argon protection according to the designed two-dimensional information under the control of the computer, and repeat this process until the required sample is obtained. Linear irradiation is performed, and the laser used is a semiconductor laser. The speed is 80mm / min, the powder feeding rate is 40g / min, the overlap rate is 40%, and the laser power is 2300W.

[0053] Experimental tests show that the pore diameter of the porous magnesium alloy manufactured by the method of this embodiment is between 90-105 μm.

[0054] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for preparing a closed-cell foam steel, characterized in that: The following steps are included: S1: mixing steel powder and magnesium powder or magnesium alloy powder to obtain a mixed powder, wherein the mass percentage of the magnesium powder or magnesium alloy powder in the mixed powder is 2-7%; S2: ball milling the mixed powder to obtain a powder raw material; S3: According to the size requirements, laser processing parameters and scanning trajectories are selected and input into the corresponding laser processing operating system to obtain two-dimensional information; laser selective melting technology or laser direct deposition technology is used to perform additive manufacturing processing using the powder raw material to obtain the closed-cell foam steel.

2. The method for preparing closed-cell foam steel according to claim 1, characterized in that: In the step S2, the mixed powder is placed in a ball mill for ball milling for 1-3 hours; during the ball milling process, the surface temperature of the ball mill jar does not exceed 60°C.

3. The method for preparing closed-cell foam steel according to claim 2, characterized in that: Argon or acetone was introduced during the ball milling process.

4. The method for preparing closed-cell foam steel according to claim 1, characterized in that: In step S2, the specific operation of using laser selective melting technology for additive manufacturing is: using a powder feeding mechanism to transport part of the powder raw material to a designated area and compact it; at the same time, under a protective atmosphere, using a laser to scan according to the two-dimensional information to melt the preset powder raw material; repeating the powder feeding, compacting and melting processes until the closed-cell foam steel is obtained.

5. The method for preparing closed-cell foam steel according to claim 4, characterized in that: The scanning speed is 40-200 mm / min, and the laser power is 80-300 W.

6. The method for preparing closed-cell foam steel according to claim 4, characterized in that: After compaction, the thickness of each layer of powder raw material is 0.2-0.5mm.

7. The method for preparing closed-cell foam steel according to claim 1, characterized in that: In the step S2, the specific operation of using laser direct deposition technology for additive manufacturing is: using a powder feeding mechanism to continuously transport the powder raw material to the molten pool; at the same time, under a protective atmosphere, using a laser to scan according to the two-dimensional information, melt and sinter until the closed-cell foam steel is obtained.

8. The method for preparing closed-cell foam steel according to claim 7, characterized in that: The powder feeding rate of the powder feeding mechanism is 3-51 g / min.

9. The method for preparing closed-cell foam steel according to claim 7, characterized in that: The scanning rate is 80-240 mm / min, the overlap rate is 20-50%, and the laser power is 1000-2500W.

10. A closed-cell foam steel obtained by the preparation method according to any one of claims 1 to 9.