Composite manufacturing method for improving side face integrity of selective laser melting additive manufacturing 316L part

Abstract

The invention provides a composite manufacturing method for improving the integrity of the side face of a 316L part manufactured through selective laser melting additive manufacturing. The composite manufacturing method comprises the following steps that S1, selective laser melting additive manufacturing is conducted on the part; in this step, each layer is divided into a boundary region and a core region, and differentiated scanning strategies are implemented. Specifically, the boundary area adopts a scanning strategy of parallel section contour lines, and the core area adopts a conventional strip or chessboard type scanning strategy, so that the surface quality is optimized; and S2, ultrasonic surface deep rolling post-treatment is conducted on the side face of the part. The method is characterized in that through the combination of partition scanning and post-treatment, the excellent surface integrity, including high surface hardness, high corrosion resistance and low surface roughness, of the side face of the additive manufacturing 316L stainless steel part is achieved. Particularly, the surface roughness reaches the precision grinding level, meanwhile, the thin-wall part manufactured through the method shows extremely high strength and plasticity at the same time, and therefore the requirement for high-performance application is met.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a composite manufacturing method for improving the side integrity of a 316L component manufactured by selective laser melting additive manufacturing. Background Art

[0002] Additive manufacturing technology (also known as 3D printing), especially metal additive manufacturing, can produce metal parts with complex geometric structures and fine internal features with unprecedented freedom. This technology not only greatly reduces material waste and reduces production costs, but also significantly shortens the manufacturing cycle, thus making significant progress in efficiency and sustainability. The widespread application of additive manufacturing technology is leading to a profound change in the manufacturing of key parts in the fields of aerospace, marine equipment, rail transportation, engineering machinery, mining machinery, biomedicine, etc., and promoting the entire manufacturing industry to develop in a more intelligent and personalized direction.

[0003] 316L stainless steel is widely used in various fields due to its excellent corrosion resistance, excellent mechanical properties and formability. 316L stainless steel is also one of the most successful materials in the field of additive manufacturing. It is widely used to manufacture key components such as heat exchangers, multi-channel valve bodies, and marine equipment components. Research in recent years has shown that compared with traditionally manufactured 316L stainless steel, additively manufactured 316L stainless steel not only performs better in strength and plasticity, but also has better pitting performance. These characteristics not only prove the superiority of additively manufactured 316L stainless steel parts, but also indicate its broad prospects in future applications.

[0004] Additive manufacturing technology is well known for its unique layer-by-layer construction method, but this also leads to a generally high surface roughness, a phenomenon that also exists in the additive manufacturing of 316L stainless steel. Even the selective laser melting (SLM) technology, which performs well in surface quality control, often produces 316L stainless steel parts with a surface roughness Ra value of more than 10μm, which is significantly higher than traditional subtractive manufacturing processes, such as fine turning processes, where the surface roughness Ra value can reach 0.8 to 1.6μm. This high surface roughness often fails to meet the standards of key components that have strict requirements on surface quality. In addition, the surface hardness of 316L stainless steel is relatively low, and its corrosion resistance in harsh environments such as the ocean needs to be improved. These problems make the surface integrity of 316L stainless steel parts manufactured by additive manufacturing insufficient, becoming the main obstacle to its widespread application. Summary of the invention

[0005] In view of the current technical bottleneck, the present invention provides a composite manufacturing method for improving the side integrity of 316L parts manufactured by selective laser melting additive manufacturing. Specifically, through the combination of the partition scanning strategy of the additive manufacturing process and the ultrasonic surface deep rolling post-processing, the excellent surface integrity of the side of the additively manufactured 316L stainless steel parts is achieved, which includes reducing the surface roughness, improving the surface hardness and enhancing the corrosion resistance. Especially for thin-walled parts, the parts manufactured by the present invention show extremely high strength and plasticity, thus meeting the needs of high-performance applications.

[0006] The technical means adopted by the present invention are as follows:

[0007] A composite manufacturing method for improving the side integrity of a 316L component manufactured by selective laser melting additive manufacturing, comprising the following steps:

[0008] S1, Selective Laser Melting Additive Manufacturing of 316L Stainless Steel Parts

[0009] Furthermore, 316L stainless steel powder was used with a particle size of 45 to 105 μm;

[0010] Furthermore, the key process parameters of the selective laser melting are as follows: laser power 100-400W, scanning speed 200-1000mm / s, scanning spacing 0.05-0.20mm, layer thickness 0.01-0.1mm;

[0011] Furthermore, each layer is divided into a boundary area and a core area, the width of the boundary is 0.03-0.1 mm, and differentiated scanning strategies are implemented in the boundary area and the core area to improve the surface quality and reduce the roughness of the side of the additively manufactured parts;

[0012] Further, the scanning strategy of the core may be a strip scanning strategy, a chessboard scanning strategy, a triangle wave strip scanning strategy, etc. The inter-layer scanning path angle may be any angle, preferably 67°;

[0013] Furthermore, the boundary area adopts a scanning strategy parallel to the cross-sectional contour line. The laser power is 120-160W, and the scanning speed is 300-500mm / min;

[0014] S2, ultrasonic deep rolling technology is used to post-process the side of 316L stainless steel parts

[0015] Furthermore, the static load of the ultrasonic surface deep rolling is 400-2000N, the frequency is 20-30kHz, the amplitude is 3-20μm, the rolling speed is 0.1-10m / min, the rolling interval is 0.01-0.5mm, the ball diameter is 4-20mm, and the rolling is 1-6 times.

[0016] Furthermore, during the ultrasonic deep rolling process, cooling and lubrication are performed by using coolant or cutting oil, and a cooling source such as liquid nitrogen can also be used for more effective cooling. Cutting oil is preferred.

[0017] The composite manufacturing method provided by the present invention for improving the side integrity of 316L parts manufactured by selective laser melting additive manufacturing has the following beneficial effects:

[0018] 1. The greatest advantage of the present invention is that a method is used to achieve multiple beneficial properties on the side of a 316L component manufactured by selective laser melting additive manufacturing;

[0019] 2. The side of the additively manufactured 316L stainless steel parts has excellent surface integrity, including low surface roughness, high surface hardness and high corrosion resistance;

[0020] 3. For thin-walled parts, the parts obtained by the present invention have extremely high strength and plasticity as a whole;

[0021] 4. The method is highly applicable and suitable for side parts with complex geometric shapes;

[0022] 5. The method has high cost and efficiency advantages. In particular, the method of the present invention can be applied only to the key side faces, thereby greatly improving the processing efficiency and reducing the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Attached Figure 1 is the surface hardness of the embodiment and the comparative example

[0025] Attached Figure 2 It is the Tafel curve diagram of embodiment and comparative example

[0026] Attached Figure 3 Typical tensile curves of the examples and comparative examples DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] Example:

[0029] The 316L stainless steel flat plate specimen was manufactured by selective laser melting process, and its side was processed by ultrasonic surface deep rolling technology. The specific implementation process is as follows:

[0030] S1, Selective Laser Melting Additive Manufacturing of 316L Stainless Steel Parts

[0031] 25×50×2.5mm is manufactured by selective laser melting technology 3 The raw material of the sample is 316L stainless steel powder with an average particle size of ~33.98μm. The selective laser melting technology is carried out using the SimpNeed SLM 280 system equipment, and the parts are divided into the core and the boundary area for printing. The scanning strategy of the core is the strip strategy, the laser power is 200W, the scanning rate is 1000mm / s, the scanning spacing is 0.11mm, the layer thickness is 0.03mm, and the scanning direction is rotated 67° between layers. The boundary area adopts a scanning strategy parallel to the cross-sectional contour line, and is printed using a 140W laser power device with a scanning speed of 350mm / min. Other parameters are consistent with the core.

[0032] S2, ultrasonic deep rolling technology is used to post-process the side of 316L stainless steel parts

[0033] Ultrasonic surface deep rolling technology was used to process the two side surfaces of the SLM specimen in four passes. The main process parameters included ultrasonic frequency of 22 kHz, amplitude of 5 μm, static load of 1200 N, scanning speed of 0.02 m / s, scanning interval of 0.1 mm, ball diameter of 14 mm, and static pressure of 800 N. Cutting oil was used for lubrication and cooling.

[0034] Comparative Example:

[0035] The 316L stainless steel parts are manufactured by selective laser melting process and polished with sandpaper. The specific implementation process is as follows:

[0036] S1, Selective Laser Melting Additive Manufacturing of 316L Stainless Steel Parts

[0037] The printing strategy of the sample of comparative example 1 adopts the printing strategy of the core in embodiment 1, that is, a 200W power laser is used for printing, a scanning rate of 1000mm / s, a scanning spacing of 0.11mm, a layer thickness of 0.03mm, and a long straight line scanning strategy is used in each layer, and the scanning direction is rotated 67° between layers.

[0038] S2. Grinding and cleaning the sides of additively manufactured 316L stainless steel parts

[0039] Use 800-grit sandpaper to grind the sides of 316L stainless steel parts made by selective laser melting until they are smooth and bright, and soak them in more than 95% alcohol for ultrasonic cleaning to remove metal powder, oil stains, dust and other impurities on the surface. Finally, use a cold air blower to dry the surface.

[0040] The surface roughness Ra value of the embodiment is 0.04 μm, which is much smaller than the roughness data of metal selective laser melting (Ra value is usually greater than 10 μm), and reaches the roughness level of precision grinding.

[0041] The surface hardness was measured by a micro Vickers hardness tester, with a load of 4.9 Newtons and a holding time of 15 seconds. The results showed that the surface hardness of the embodiment reached 417.9 HV, which was 67% higher than that of the comparative example (249.9 HV). Figure 1 shown.

[0042] The corrosion behavior of the embodiment and the comparative example in 3.5wt.% NaCl solution was tested by electrochemical experiment. The results showed that the corrosion current density of the embodiment was 118A / cm 2 ×10 -9 , the pitting voltage is 552.9mV, such as Figure 2 The corrosion current density of the comparative example is 149A / cm 2 ×10 -9 , the corrosion potential is -229V×10 -1 , the pitting voltage is 449.5 mV. In comparison, the corrosion resistance of the embodiment in NaCl solution is significantly better than that of the comparative example, indicating that the embodiment has excellent corrosion resistance in a marine environment.

[0043] The results of the uniaxial tensile test at room temperature show that the yield strength of the embodiment reaches 694.8 MPa and the ultimate tensile strength is 772.5 MPa. Figure 3 As shown. In contrast, the yield strength of the comparative example is 516.2MPa and the ultimate tensile strength is 674.4MPa, which represents the typical strength level of 316L stainless steel currently manufactured by additive manufacturing. The yield strength of the embodiment is increased by 34.6% compared with the comparative example, while maintaining an elongation of 42.6%, which shows that the embodiment exhibits excellent mechanical properties.

Claims

1. A composite manufacturing method for improving the side integrity of a 316L component manufactured by selective laser melting additive manufacturing, comprising the following steps: S1, Selective laser melting additive manufacturing of 316L stainless steel parts; S2. Ultrasonic deep surface rolling technology is used to post-process the side of 316L stainless steel parts.

2. A composite manufacturing method for improving the side integrity of 316L parts manufactured by selective laser melting additive manufacturing according to claim 1, characterized in that: In step S1, each layer is divided into a boundary area and a core area, and a differentiated scanning strategy is implemented, and the width of the boundary is 0.03-0.1 mm. The aim is to improve the surface quality and reduce the roughness on the sides of additively manufactured parts.

3. A composite manufacturing method for improving the side integrity of 316L parts manufactured by selective laser melting additive manufacturing according to claim 1, characterized in that: In step S1, the boundary area adopts a scanning strategy parallel to the cross-sectional contour line, with a laser power of 120-160 W and a scanning speed of 300-500 mm / min, while the core adopts a commonly used strip scanning strategy, a chessboard scanning strategy, a triangle wave strip scanning strategy, etc.

4. A composite manufacturing method for improving the side integrity of 316L parts manufactured by selective laser melting additive manufacturing according to claim 1, characterized in that: The processing parameters used in the ultrasonic surface deep rolling technology in step S2 are: static load of 400-20000N, frequency of 20-30kHz, amplitude of 3-20μm, rolling speed of 0.1-10m / min, rolling interval of 0.01-0.5mm, ball diameter of 4-20mm, and rolling 1-6 times.

5. A composite manufacturing method for improving the side integrity of 316L parts manufactured by selective laser melting additive manufacturing according to claim 1, characterized in that: In the ultrasonic surface deep rolling process of step S2, coolant or cutting oil is used for cooling and lubrication. Liquid nitrogen and other cold sources can also be used for more effective cooling. Cutting oil is preferred.

6. A composite manufacturing method for improving the side integrity of 316L parts manufactured by selective laser melting additive manufacturing according to claim 1, characterized in that: The obtained parts have excellent surface integrity on their sides, including low surface roughness, high surface hardness, high corrosion resistance, etc.

7. A composite manufacturing method for improving the side integrity of 316L parts manufactured by selective laser melting additive manufacturing according to claim 1, characterized in that: For thin-walled parts, the parts obtained by the present invention have extremely high strength and plasticity as a whole.

8. A composite manufacturing method for improving the side integrity of 316L parts manufactured by selective laser melting additive manufacturing according to claim 1, characterized in that: The process has strong applicability and is suitable for side parts with complex geometric shapes.

9. A composite manufacturing method for improving the side integrity of 316L parts manufactured by selective laser melting additive manufacturing according to claim 1, characterized in that: The method has high cost and efficiency advantages, and can be used only on key sides, thereby greatly improving processing efficiency and reducing costs.

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