LPBF austenitic stainless steel with high powder utilization rate and manufacturing method of LPBF austenitic stainless steel

Abstract

The invention relates to the technical field of stainless steel materials prepared through LPBF, in particular to LPBF austenitic stainless steel with the high powder utilization rate and a manufacturing method of the LPBF austenitic stainless steel. The austenitic stainless steel powder adopted by the invention comprises the following components in percentage by mass: less than or equal to 0.15% of C, less than or equal to 0.045% of P, less than or equal to 0.030% of S, less than or equal to 1.00% of Si, less than or equal to 2.00% of Mn, 16.00-26.00% of Cr, 3.50-22.00% of Ni, 2.00-3.00% of Mo, 0.8-1.50% of N, 0.8-1.50% of Ti and the balance of Fe. The austenitic stainless steel powder with the components is subjected to laser powder bed melting according to different parameters, an austenitic stainless steel formed part is finally formed, and the formed part is subjected to heat treatment. The process parameters of the LPBF are 300 to 380 W, the scanning rate is 600 to 1050 mm / s, the scanning interval is 0.05 to 0.15 mm, and the layer thickness is 60 to 90 microns; the heat treatment temperature is 600-800 DEG C, and the heat treatment time is 1-8 hours. According to the method, the high-density austenitic stainless steel can be manufactured by using the powder with the particle size of 15-53 microns and the powder with the particle size of 54-105 microns at the same time, and the utilization rate of the powder is effectively increased.

Description

Technical Field

[0001] This invention relates to the field of LPBF preparation of stainless steel materials, and in particular to an LPBF austenitic stainless steel with high powder utilization and its manufacturing method. Background Technology

[0002] Austenitic stainless steel is widely used in industries such as medical, chemical, marine engineering, aerospace, and nuclear power due to its high thermal stability, strong corrosion resistance, and excellent mechanical properties at both room and low temperatures. Laser powder bed melting (LPBF) is an additive manufacturing process that uses a laser beam as an energy source to melt a bed of powder layer by layer according to pre-established CAD data and form parts. It can produce high-precision austenitic stainless steel components; this technology has developed rapidly over the past 30 years and has been widely applied.

[0003] Currently reported austenitic stainless steel manufactured using LPBF primarily employs powders with particle sizes ranging from 15 to 53 μm. Chinese patent CN118527660A describes the use of powders with particle sizes in the 15-53 μm range when constructing the powder bed based on the LPBF process; Chinese patent CN118268590A discloses a method for preparing high-elongation 316L stainless steel using selective laser melting, employing powders with particle sizes ranging from 15 to 53 μm; and Chinese patent CN202310140339.0 describes the preparation of stainless steel-based composite materials using 316L and high-entropy alloy powders, where the 316L powder has a particle size range of 15-53 μm.

[0004] Currently, the powder used for LPBF austenitic stainless steel is mainly produced using the gas atomization method. During powder production, powder with a particle size of 1-300 μm is typically produced. If powder with a particle size of 54-105 μm (hereinafter referred to as "coarse powder") is used in LPBF production, the density of the stainless steel decreases sharply, and defects such as porosity increase significantly. Therefore, this coarse powder is considered waste powder in the LPBF industry and cannot be used on a large scale for commercial purposes.

[0005] Therefore, there is a need for an LPBF austenitic stainless steel that uses 54-105μm powder to ensure that its density reaches the level of products printed using powder with a particle size of 15-53μm as raw material. Summary of the Invention

[0006] To address the issues of limited powder particle size range and low powder utilization in LPBF printing of austenitic stainless steel, this invention provides an LPBF austenitic stainless steel that can utilize both 15-53μm and 54-105μm powders, along with its manufacturing method. This invention significantly improves powder utilization without requiring major equipment changes or new equipment investment, and has significant engineering application value.

[0007] To address the above problems, the technical solution of the present invention is as follows.

[0008] A method for manufacturing LPBF austenitic stainless steel with high powder utilization rate includes the following steps: Step 1: Prepare raw materials, make your own austenitic stainless steel powder; Step 2: Obtain austenitic stainless steel components by passing austenitic stainless steel powder through the LPBF method; Step 3: Heat treat the austenitic stainless steel components to obtain austenitic stainless steel.

[0009] Furthermore, the austenitic stainless steel powder has a particle size of 15-53 μm powder or 54-105 μm (waste powder).

[0010] Furthermore, austenitic stainless steel powder is prepared by aerosol method, including the following specific steps: using austenitic stainless steel ingot as raw material, after loading the ingot into the furnace, the furnace is evacuated, and then the ingot is melted; after the furnace charge is completely melted, the evacuation is stopped, and then the melt temperature is raised to a predetermined temperature, at which point atomization begins; after atomization, the tail exhaust is turned off, and the obtained austenitic stainless steel powder is cooled in the atomized gas environment, and after cooling, it is vacuum sealed.

[0011] Furthermore, the austenitic stainless steel powder comprises the following elements: C: ≤0.15%, P: ≤0.045%, S: ≤0.030%, Si: ≤1.00%, Mn: ≤2.00%, Cr: 16.00~26.00%, Ni: 3.50~22.00%, Mo: 2.00~3.00%, N: 0.80~1.50%, Ti: 0.80~1.50%, with the balance being Fe; all percentages are by mass.

[0012] Furthermore, in step 2, the process parameters of LPBF include: laser power of 340-390W, scanning rate of 600-1050mm / s, scanning spacing of 0.05-0.15mm, and layer thickness of 60-90μm.

[0013] Furthermore, in step 3, the heat treatment parameters are: annealing temperature of 600~800℃ and annealing time of 1~8h.

[0014] The density of LPBF austenitic stainless steel with high powder utilization rate is ≥99.3%.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0016] This invention can utilize not only powders with particle sizes of 15-53μm, but also powders considered waste (54-105μm). Based on LPBF technology, it prints austenitic stainless steel with a density ≥99.3%, enabling the utilization of 54-105μm powder, which is traditionally classified as waste powder in LPBF printing plants, resulting in a significant advantage in reducing production costs. The aforementioned waste powder-utilizable LPBF austenitic stainless steel and its manufacturing method effectively solve the problem of numerous pore defects in the printing process using waste powder (54-105μm). When traditional austenitic stainless steels such as 316L are used for LPBF printing, if the raw material powder particle size is 54-105μm, the increased particle heat capacity and decreased layup density easily lead to insufficient molten pool energy, resulting in incomplete fusion pores. Simultaneously, factors such as a thick oxide film on the particle surface, poor wettability, and gas entrainment can induce porosity. More importantly, large-particle-size powders often lead to coarsening of the solidification structure and significant grain growth, which in turn reduces strength and fatigue performance, exacerbates the tendency for hot cracking, and deteriorates service reliability.

[0017] Significantly reducing grain size shortens the feeding channels, reduces reflux resistance, and enhances liquid-liquid connectivity at the end of solidification, thereby effectively suppressing void formation. Liquid reflux along grain boundary channels is the primary way to suppress void defects during solidification, as the molten metal compensates for formed voids by following the grain boundary path. However, due to the viscosity of the molten metal, intergranular channels resist liquid reflux, causing the liquid pressure to gradually decrease. In this invention, the addition of appropriate amounts of N and Ti elements promotes the formation of TiN heteronucleating agents, replacing large-sized, flat columnar crystals with refined grains. This shortens the intergranular channels in the later stages of solidification, reduces the liquid supply resistance required to suppress voids, and decreases void formation.

[0018] Based on the above mechanism, this patent employs a special composition design to alter its solidification nucleation and growth behavior during printing. According to the nucleation theory and interdependence theory of Winegard and Chalmers, if the newly formed solid / liquid (S / L) interface front generates sufficient supercooling (ΔT), and this supercooling exceeds the critical nucleation supercooling (ΔT) required for heterogeneous nucleation, n That is, ΔT≥ΔT n This invention effectively improves the solidification nucleation rate. By adding appropriate amounts of N and Ti elements, the formation of TiN heterogeneous nucleating agents is promoted. TiN and the δ-ferrite phase of austenitic stainless steel at high temperatures have very similar lattice mismatch. Therefore, in the solid-liquid two-phase region, the δ-ferrite of austenitic stainless steel requires only a small degree of undercooling (T0) on TiN particles. nCrystallization can then occur. Simultaneously, the numerous heterogeneous nucleations occurring in front of the solid / liquid interface effectively inhibit the growth of δ-grains, achieving a highly efficient grain refinement effect and thus eliminating columnar crystals formed during solidification. The resulting fine grain network shortens the liquid replenishment channel, improves the permeability of the mushy region, reduces liquid backflow resistance, inhibits the formation of unfused and solidification shrinkage voids, and thus significantly improves the density of the molded part. Attached Figure Description

[0019] Figure 1 The relationship between nitrogen content and density of austenitic stainless steel forming parts with different laser powers according to the present invention. Detailed Implementation

[0020] The technical solutions of this invention will now be clearly and completely described. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] A method for manufacturing LPBF austenitic stainless steel with high powder utilization rate includes the following steps: Step 1: Prepare raw materials and make austenitic stainless steel powder. The austenitic stainless steel powder includes the following elements: C: ≤0.15%, P: ≤0.045%, S: ≤0.030%, Si: ≤1.00%, Mn: ≤2.00%, Cr: 16.00~26.00%, Ni: 3.50~22.00%, Mo: 2.00~3.00%, N: 0.80~1.50%, Ti: 0.80~1.50%, with the balance being Fe; all percentages are by mass; the particle size of the austenitic stainless steel powder is 15-53μm powder or 54-105μm (waste powder). Step 2: Obtain austenitic stainless steel components by passing austenitic stainless steel powder through the LPBF method; the process parameters of LPBF include: laser power of 340-390W, scanning rate of 600-1050mm / s, scanning spacing of 0.05-0.15mm, and layer thickness of 60-90μm. Step 3: Heat treat the austenitic stainless steel components. The heat treatment parameters are: annealing temperature of 600~800℃ and annealing time of 1~8h to obtain austenitic stainless steel.

[0022] Furthermore, austenitic stainless steel powder is prepared by aerosol method, including the following specific steps: using austenitic stainless steel ingot as raw material, after loading the ingot into the furnace, the furnace is evacuated, and then the ingot is melted; after the furnace charge is completely melted, the evacuation is stopped, and then the melt temperature is raised to a predetermined temperature, at which point atomization begins; after atomization, the tail exhaust is turned off, and the obtained austenitic stainless steel powder is cooled in the atomized gas environment, and after cooling, it is vacuum sealed.

[0023] The density of LPBF austenitic stainless steel with high powder utilization rate is ≥99.3%.

[0024] Example 1.

[0025] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0026] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 60 μm, scanning spacing of 0.05 mm, laser power of 300 W, laser speed of 1050 mm / s, and energy density of 95 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 600℃, annealing time 8h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0027] The density of the stainless steel formed parts obtained by the above method is 99.3%.

[0028] Example 2.

[0029] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0030] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 80 μm, scanning interval of 0.1 mm, laser power of 340 W, laser speed of 850 mm / s, and energy density of 50 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 700℃, annealing time 4h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0031] The density of the stainless steel formed parts obtained by the above method is 99.6%.

[0032] Example 3.

[0033] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0034] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 90 μm, scanning interval of 0.15 mm, laser power of 380 W, laser speed of 600 mm / s, and energy density of 47 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 800℃, annealing time 1h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0035] The density of the stainless steel formed parts obtained by the above method is 99.5%.

[0036] Example 4.

[0037] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0038] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 60 μm, scanning spacing of 0.05 mm, laser power of 300 W, laser speed of 1050 mm / s, and energy density of 95 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed. The annealing parameters were: annealing temperature 600℃, annealing time 8h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0039] The density of the stainless steel formed parts obtained by the above method is 99.6%.

[0040] Example 5.

[0041] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0042] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 80 μm, scanning interval of 0.1 mm, laser power of 340 W, laser speed of 850 mm / s, and energy density of 50 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 700℃, annealing time 4h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0043] The density of the stainless steel formed parts obtained by the above method is 99.6%.

[0044] Example 6.

[0045] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0046] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 90 μm, scanning interval of 0.15 mm, laser power of 380 W, laser speed of 600 mm / s, and energy density of 47 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 800℃, annealing time 1h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0047] The density of the stainless steel formed parts obtained by the above method is 99.5%.

[0048] Example 7.

[0049] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0050] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 60 μm, scanning spacing of 0.05 mm, laser power of 380 W, laser speed of 600 mm / s, and energy density of 95 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 600℃, annealing time 8h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0051] The density of the stainless steel formed parts obtained by the above method is 99.4%.

[0052] Example 8.

[0053] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0054] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 80 μm, scanning interval of 0.1 mm, laser power of 340 W, laser speed of 850 mm / s, and energy density of 50 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 700℃, annealing time 4h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0055] The density of the stainless steel formed parts obtained by the above method is 99.8%.

[0056] Example 9.

[0057] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0058] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 90 μm, scanning interval of 0.15 mm, laser power of 380 W, laser speed of 600 mm / s, and energy density of 47 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 800℃, annealing time 1h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0059] The density of the stainless steel formed parts obtained by the above method is 99.4%.

[0060] Example 10.

[0061] The austenitic stainless steel powder with alloying elements as shown in Table 1 was prepared using a particle size of 15~53μm.

[0062] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 60 μm, scanning spacing of 0.05 mm, laser power of 300 W, laser speed of 1050 mm / s, and energy density of 95 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed. The annealing parameters were: annealing temperature 600℃, annealing time 8h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0063] The density of the stainless steel formed parts obtained by the above method is 99.7%.

[0064] Example 11.

[0065] The austenitic stainless steel powder with alloying elements as shown in Table 1 was prepared using a particle size of 15~53μm.

[0066] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 80 μm, scanning interval of 0.1 mm, laser power of 340 W, laser speed of 850 mm / s, and energy density of 50 J / mm². 3The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 700℃, annealing time 4h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0067] The density of the stainless steel formed parts obtained by the above method is 99.8%.

[0068] Comparative Example 1.

[0069] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0070] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 80 μm, scanning interval of 0.1 mm, laser power of 340 W, laser speed of 850 mm / s, and energy density of 50 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 600℃, annealing time 4h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0071] The density of the stainless steel formed parts obtained by the above method is 98.9%.

[0072] Comparative Example 2.

[0073] The self-made austenitic stainless steel powder with alloying elements as shown in Table 1 was used, and the particle size of the austenitic stainless steel powder used was 54-105 μm.

[0074] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 90 μm, scanning interval of 0.15 mm, laser power of 380 W, laser speed of 600 mm / s, and energy density of 95 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 600℃, annealing time 4h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0075] The density of the stainless steel formed parts obtained by the above method is 99.2%.

[0076] Comparative Example 3.

[0077] The austenitic stainless steel powder with alloying elements as shown in Table 1 was prepared using a particle size of 15–53 μm.

[0078] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 60 μm, scanning interval of 0.1 mm, laser power of 300 W, laser speed of 1050 mm / s, and energy density of 50 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 600℃, annealing time 8h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0079] The density of the stainless steel formed parts obtained by the above method is 99.3%.

[0080] Comparative Example 4.

[0081] The austenitic stainless steel powder with alloying elements as shown in Table 1 was prepared using a particle size of 15–53 μm.

[0082] Self-made austenitic stainless steel powder was loaded into an LPBF (Liquid Laser Printing) device for printing. The printing parameters were: layer thickness of 80 μm, scanning interval of 0.15 mm, laser power of 340 W, laser speed of 850 mm / s, and energy density of 47 J / mm². 3 The austenitic stainless steel components obtained by LPBF were annealed with the following parameters: annealing temperature 700℃, annealing time 4h, and air cooling. After annealing, the printing material was cooled to room temperature by air cooling.

[0083] The density of the stainless steel formed parts obtained by the above method is 98.5%.

[0084] Table 1. Composition of austenitic stainless steel powder (mass fraction).

[0085] The above description is merely a preferred embodiment of the present invention. For those skilled in the art, modifications and substitutions can be made within the scope of the claims of this patent. Whether it is a minor adjustment to the process flow or an attempt to diversify material selection, all such modifications and substitutions should be considered within the protection scope of the present invention. Therefore, the protection scope of this patent application should be determined by the appended claims, while the specification and drawings can be used to assist in understanding the meaning of the claims.

Claims

1. A method for manufacturing LPBF austenitic stainless steel with high powder utilization rate, characterized in that, Includes the following steps: Step 1: Prepare raw materials, make your own austenitic stainless steel powder; Step 2: Obtain austenitic stainless steel components by passing austenitic stainless steel powder through the LPBF method; Step 3: Heat treat the austenitic stainless steel components to obtain austenitic stainless steel.

2. The method for manufacturing LPBF austenitic stainless steel with high powder utilization rate according to claim 1, characterized in that, The particle size of austenitic stainless steel powder is 15-53μm or 54-105μm.

3. The method for manufacturing LPBF austenitic stainless steel with high powder utilization rate according to claim 1, characterized in that, Austenitic stainless steel powder is prepared by aerosolization, including the following specific steps: using austenitic stainless steel ingots as raw materials, the ingots are loaded into the furnace, and a vacuum operation is performed inside the furnace, followed by melting of the ingots; once the furnace charge is completely melted, the vacuum operation is stopped, and then the melt temperature is raised to a predetermined temperature, at which point atomization begins; after atomization, the tail exhaust is turned off, and the obtained austenitic stainless steel powder is cooled in the atomized gas environment, and after cooling, it is vacuum sealed.

4. The method for manufacturing LPBF austenitic stainless steel with high powder utilization rate according to claim 1, characterized in that, Homemade austenitic stainless steel powder includes the following elements: C: ≤0.15%, P: ≤0.045%, S: ≤0.030%, Si: ≤1.00%, Mn: ≤2.00%, Cr: 16.00~26.00%, Ni: 3.50~22.00%, Mo: 2.00~3.00%, N: 0.80~1.50%, Ti: 0.80~1.50%, balance Fe; All percentages are mass percentages.

5. The method for manufacturing LPBF austenitic stainless steel with high powder utilization rate according to claim 1, characterized in that, In step 2, the process parameters of LPBF include: laser power of 340-390W, scanning rate of 600-1050mm / s, scanning spacing of 0.05-0.15mm, and layer thickness of 60-90μm.

6. The method for manufacturing LPBF austenitic stainless steel with high powder utilization rate according to claim 1, characterized in that, In step 3, the heat treatment parameters are: annealing temperature of 600~800℃ and annealing time of 1~8h.

7. An austenitic stainless steel prepared by the method for manufacturing LPBF austenitic stainless steel with high powder utilization according to any one of claims 1-6.

8. An austenitic stainless steel prepared by the method for manufacturing high powder utilization LPBF austenitic stainless steel according to any one of claims 1-7, characterized in that, The density of the austenitic stainless steel is ≥99.3%.

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