Automobile bottom protection plate and preparation method thereof

Abstract

The invention discloses an automobile bottom guard plate and a preparation method thereof, and relates to the field of automobile manufacturing, the preparation method comprises the following steps: firstly, preparing raw materials including 316L stainless steel powder, SiC powder and CeOpowder, the total content of the SiC powder and the CeOpowder is 1-5wt%, the weight ratio of the CeOpowder to the SiC powder is 1: 6-1: 3, then pretreating the raw materials, and carrying out heat treatment on the pretreated raw materials; and the pretreated raw materials are loaded into a powder supply cylinder of laser powder bed melting equipment, the automobile bottom guard plate is printed, and after printing is completed, the automobile bottom guard plate is subjected to aftertreatment. According to the automobile bottom guard plate formed by printing the SiC / CeO / 316L stainless steel composite powder, the hardness and the strength are greatly improved, the toughness and the ductility are improved, the abrasion resistance and the fatigue resistance are excellent, the automobile bottom guard plates with various complex shapes and high precision can be printed, and the industrial application value and the market prospect are huge.

Description

Technical Field

[0001] This invention relates to the field of automobile manufacturing technology, and more specifically, to an automobile underbody protection plate and its preparation method. Background Technology

[0002] Automotive underbody protection plates are engine protection devices designed to adapt to various vehicle models. They are protective plates installed at the bottom of the engine compartment to prevent the engine from being corroded by mud, sewage, etc., and to avoid damage to the engine from impacts by stones or friction with the ground. Therefore, automotive underbody protection plates have high requirements for wear resistance and mechanical properties.

[0003] With the development of the automotive industry, people have increasingly higher requirements for the performance and aesthetics of cars, leading to the emergence of various complex car structures. Consequently, car underbody protection plates have also taken on various structural forms. For complex underbody protection plates, traditional stamping and other processes are difficult to manufacture.

[0004] Additive manufacturing (AM), also known as 3D printing, is an advanced manufacturing technology that creates three-dimensional solids by depositing materials layer by layer. Among them, laser powder bed fusion (LPBF) technology has the ability to manufacture complex geometries, high-precision and high-density metal parts, and is suitable for making complex automotive underbody protection panels.

[0005] 316L stainless steel, a typical austenitic stainless steel, has become one of the most widely used materials in LPBF (Liquid-Based Burning) technology due to its excellent corrosion resistance, good formability, and comprehensive mechanical properties. However, compared with traditionally forged or cast 316L stainless steel, the inherent rapid melting and solidification characteristics of LPBF technology lead to some inherent defects in the 316L stainless steel parts printed from it: First, LPBF-formed parts usually have high residual stress, which may cause deformation or even cracking; second, its strength, hardness, and wear resistance often fail to meet the requirements of some working conditions with extremely high mechanical performance requirements (such as high-load friction environments, high-temperature and high-pressure components, etc.). These performance limitations severely restrict the application of LPBF technology in printing 316L stainless steel parts in a wider range of industrial fields.

[0006] To overcome limitations, existing technologies have attempted to prepare 316L stainless steel composites by introducing reinforcing phases to improve their mechanical properties and wear resistance. Silicon carbide (SiC), due to its extremely high hardness, good thermal stability, and wear resistance, is considered an ideal reinforcing phase material. By introducing SiC particles into the 316L stainless steel matrix through the LPBF process, it is hoped that the strengthening effect of SiC will significantly improve the strength, stiffness, and wear resistance of the composite material.

[0007] However, under the high-energy laser irradiation of LPBF, SiC undergoes a violent metallurgical reaction with elements such as Fe and Cr in the 316L stainless steel matrix, generating complex carbide and brittle silicide phases. This reaction consumes the effective reinforcing phase SiC, and the resulting brittle phases are often distributed at grain boundaries, which may not only lead to a less than expected strengthening effect but also severely deteriorate the toughness and ductility of the material, potentially introducing defects such as cracks and porosity, resulting in a decrease in density and negatively impacting the overall performance of the parts. Furthermore, the short melt pool life and rapid cooling rate of the LPBF process easily lead to the formation of coarse columnar crystals and significant grain boundary segregation, further posing a challenge to the balance between strength and toughness. Therefore, effectively suppressing the harmful reactions between the reinforcing phase and the metal matrix, refining the microstructure, and improving the uniformity of the reinforcing phase distribution have become key technical challenges in achieving high-performance 316L composite materials in the LPBF molding field.

[0008] To address the issue of suppressing harmful interfacial reactions, existing technologies have attempted to mitigate the reaction by adjusting laser process parameters (such as reducing laser energy density). However, this method often fails to completely solve the problem and can easily lead to new issues such as incomplete fusion and increased porosity defects. Another approach is to introduce a third alloying element, but finding an additive that can effectively regulate reaction kinetics while also having a beneficial effect on the 316L stainless steel matrix remains an area for further exploration.

[0009] In summary, there is an urgent need in this field for a new technical solution that can effectively suppress harmful interfacial reactions between SiC-reinforced 316L stainless steel and the metal matrix, refine grains, and obtain an automotive underbody protection plate that combines high strength, high hardness, excellent wear resistance, and good toughness, while utilizing the strength and wear resistance of SiC-reinforced 316L stainless steel in LPBF forming. Summary of the Invention

[0010] To overcome the above-mentioned technical defects, the present invention provides an automotive underbody protection plate and its preparation method, which not only meets the protection requirements of high strength, high hardness, good toughness and excellent wear resistance, but also can produce automotive underbody protection plates of various complex shapes and high precision.

[0011] The specific plan is as follows: This invention discloses a method for preparing an automotive underbody protection plate, comprising the following steps: S1, Prepare raw materials and pre-treat them; S2, the pre-treated raw materials are loaded into the powder supply cylinder of the laser powder bed melting equipment to print the car underbody protection plate; S3, After printing, remove the car underbody protection plate and perform post-processing on the car underbody protection plate; The raw materials in step S1 include 316L stainless steel powder, SiC powder and CeO2 powder. The total content of SiC powder and CeO2 powder is 1 to 5 wt%, and the weight ratio of CeO2 powder to SiC powder is between 1:6 and 1:3.

[0012] Preferably, the weight percentage of each component in the raw material of step S1 is: 96.5 wt% of 316L stainless steel powder, 3 wt% of SiC powder, and 0.5 wt% of CeO2 powder.

[0013] Preferably, the pretreatment of raw materials in step S1 includes the following steps: CeO2 powder was mixed with anhydrous ethanol, and the mixture was treated with an ultrasonic disruptor to form a preliminarily dispersed CeO2 suspension. Add 316L stainless steel powder and SiC powder to the CeO2 suspension above, and stir until the CeO2 suspension uniformly wets all powder particles to form a mixed slurry. The mixed slurry was placed in a vacuum rotary evaporator to slowly remove the ethanol solvent. During this process, CeO2 particles adhered to and coated the surfaces of 316L stainless steel particles and SiC particles to obtain composite powder. The resulting composite powder was dried and sieved to ensure its flowability.

[0014] Preferably, the chemical composition of the 316L stainless steel powder is: Cr: 16.5-18.5 wt%, Ni: 10.0-14.0 wt%, Mo: 2.0-3.0 wt%, C: ≤0.03 wt%, Si: ≤0.75 wt%, Mn: ≤2.0 wt%, P: ≤0.045 wt%, S: ≤0.03 wt%, with the balance being Fe.

[0015] Preferably, the printing parameters in step S2 are: laser power: 200-300W, scanning speed: 800-1200mm / s, scanning spacing: 0.08-0.12mm, layer thickness: 0.01-0.05mm, scanning strategy: stripe scanning, with the scanning direction rotated 67° between adjacent layers.

[0016] Preferably, the post-processing of the car underbody protection plate in step S3 includes: heating the car underbody protection plate to 900°C at a rate of 5°C / min under argon protection, holding it at that temperature for 2 hours, cooling it to below 200°C, and then removing it for air cooling.

[0017] Preferably, the CeO2 particles have a particle size of 10 nm to 1 μm.

[0018] Preferably, the particle size of the SiC particles is 1–5 μm.

[0019] Preferably, the particle size of the 316L stainless steel particles is 15–53 μm.

[0020] A second aspect of the present invention provides an automotive underbody protection plate, which is prepared according to the automotive underbody protection plate preparation method described in the first aspect.

[0021] The beneficial effects of this invention are as follows: Effectively suppressing harmful interfacial reactions, improving the distribution of reinforcing phases, and forming a synergistic strengthening effect: This invention introduces CeO2 into the raw materials processed by high-energy laser processing. Utilizing the unique interaction between CeO2 and active elements in the molten pool, it effectively suppresses excessively vigorous metallurgical reactions between SiC particles and the 316L stainless steel matrix (especially Cr and Fe elements), significantly reducing brittle carbides and silicides (such as Cr7C3, Cr...). 23 The addition of CeO2 refines the molten pool structure, promotes the uniform dispersion of SiC particles, and avoids the agglomeration of the reinforcing phase. CeO2 itself, as a thermally stable rare earth element reinforcing phase, together with the modified SiC, forms a composite strengthening system, which forms a good interfacial bond with the 316L stainless steel matrix, achieving synergistic strengthening.

[0022] Significantly Improved Comprehensive Mechanical and Wear Resistance of Automotive Underbody Protection Panels: Due to the optimization of the raw material microstructure, the automotive underbody protection panel prepared from SiC / CeO2 / 316L stainless steel composite powder in this invention exhibits significantly improved macroscopic properties compared to automotive underbody protection panels made of single SiC reinforced or unreinforced 316L stainless steel. Specifically: Firstly, hardness and strength are greatly improved; secondly, while maintaining good strength, the reduction of brittle phases and grain refinement improve the toughness and ductility of the material, avoiding the problem of sharp toughness decline commonly seen in traditional reinforced metal matrix composites, achieving a good balance between strength and toughness; thirdly, due to the increased hardness and uniform distribution of reinforcing phases, the automotive underbody protection panel exhibits excellent wear resistance and fatigue resistance. With excellent process compatibility and broad application prospects, the method for preparing automotive underbody protection plates of this invention does not require complex modifications to existing LPBF equipment. It achieves a significant performance leap primarily through optimized powder formulation, exhibiting strong process compatibility and ease of implementation and promotion. Automotive underbody protection plates prepared using this method can meet the urgent needs for high strength, high wear resistance, and long service life under harsh operating conditions (such as high load, high temperature, and corrosive environments). Furthermore, it can print automotive underbody protection plates of various complex shapes and high precision, possessing immense industrial application value and market potential. Attached Figure Description

[0023] Figure 1 This is an electron micrograph of the SiC / CeO2 / 316L stainless steel composite powder of the present invention; Figure 2This is the electron backscatter diffraction (EBSD) pattern of Comparative Example 1 of the present invention; Figure 3 This is the electron backscatter diffraction (EBSD) pattern of Embodiment 2 of the present invention; Figure 4 X-ray diffraction (XRD) patterns of various embodiments and comparative examples of the present invention; Figure 5 These are mechanical curves of various embodiments and comparative examples of the present invention; Figure 6 The graph shows the friction coefficient data for various embodiments and comparative examples of the present invention; Figure 7 The figures show wear rate data for various embodiments and comparative examples of the present invention. Detailed Implementation

[0024] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0025] Example 1: The method for preparing the automotive underbody protection plate disclosed in this example includes the following steps: S1. Prepare raw materials and pre-treat them.

[0026] The raw materials include matrix powder and reinforcing phase powder. The matrix powder is 316L stainless steel powder, and the reinforcing phase powder includes SiC (silicon carbide) powder and CeO2 (cerium dioxide) powder.

[0027] Matrix powder: 316L stainless steel spherical powder prepared by gas atomization method, with a particle size range of 15-53μm and chemical composition of: Cr: 16.5-18.5wt%, Ni: 10.0-14.0wt%, Mo: 2.0-3.0wt%, C: ≤0.03wt%, Si: ≤0.75wt%, Mn: ≤2.0wt%, P: ≤0.045wt%, S: ≤0.03wt%, balance Fe.

[0028] Reinforcing phase powder: SiC powder: High-purity α-SiC powder with an average particle size of 1-5 μm is selected.

[0029] CeO2 powder: High-purity nano CeO2 powder with an average particle size of 20-50 nm is selected.

[0030] In this embodiment, the raw material is a composite powder composed of 316L stainless steel powder, SiC powder and CeO2 powder, wherein the weight percentage of each component is: 97.5wt% 316L stainless steel powder, 2wt% SiC powder and 0.5wt% CeO2 powder.

[0031] Weigh out the appropriate weights of 316L stainless steel powder, SiC powder, and CeO2 powder, and perform pretreatment, including the following steps: (1) Pre-dispersion of nano CeO2: To prevent the nano CeO2 particles from agglomerating severely due to their high surface energy, the nano CeO2 powder was first mixed with anhydrous ethanol (CeO2 powder to ethanol mass ratio of 1:20) and treated with an ultrasonic disruptor (power of 500W) for 10 minutes to form a preliminarily dispersed CeO2 suspension.

[0032] (2) Mechanical fusion and in-situ encapsulation: 316L stainless steel powder and SiC powder were added to the CeO2 suspension and mechanically stirred for 2 hours to ensure that the CeO2 suspension uniformly wetted all powder particles, forming a mixed slurry. The mixed slurry was then placed in a vacuum rotary evaporator and the ethanol solvent was slowly removed at 60°C and -0.1 MPa to obtain the composite powder. During this process, the nano-CeO2 particles adhered in situ to and coated the surfaces of the larger 316L stainless steel and SiC particles via van der Waals forces, achieving a highly uniform dispersion of the nano-reinforcing phase, rather than simple mechanical mixing. Figure 1 Electron micrographs of SiC powder / CeO2 powder / 316L stainless steel powder, from Figure 1 The uniform adhesion of SiC powder / CeO2 powder / 316L stainless steel powder can be observed.

[0033] (3) Drying of composite powder: Finally, the obtained composite powder is thoroughly dried in a vacuum oven at 100°C for 4 hours, and then passed through a 100-mesh sieve to ensure its flowability. Since large particles can affect the smoothness of transmission and may cause the laser powder bed melting equipment to jam during the printing process, sieving the composite powder can remove excessively large particles caused by agglomeration and uneven coating, making the particle size uniform. It can also break up soft agglomerates, allowing the particles to return to independent single particles or form smaller agglomerates.

[0034] S2. The pretreated raw material is loaded into the powder supply cylinder of the laser powder bed melting equipment to print a sample of the car underbody protection plate. The printing parameters are: laser power: 250W, scanning speed: 1000mm / s, scanning interval: 0.10mm, layer thickness: 0.03mm, scanning strategy: stripe scanning, and the scanning direction between adjacent layers is rotated by 67°.

[0035] S3. After printing, remove the car underbody protection plate sample and separate it from the substrate using wire electrical discharge machining. Then, perform post-processing on the car underbody protection plate sample.

[0036] To further eliminate residual stress, optimize the interface structure, and promote the dispersion strengthening effect of CeO2, the printed sample can undergo the following post-processing: The automotive underbody protection plate sample was heated to 900℃ at a rate of 5℃ / min under argon protection, held at that temperature for 2 hours, and then cooled in the furnace to below 200℃ before being removed and air-cooled. This low-temperature heat treatment process can eliminate stress, stabilize the microstructure, and avoid excessive growth of the reinforcing phase or adverse phase transformation at high temperatures.

[0037] Example 2: The preparation method of the car underbody protection plate disclosed in this example is different from that in Example 1. The raw material in step S1 is a composite powder composed of 316L stainless steel powder, SiC powder and CeO2 powder, wherein the weight percentage of each component is: 96.5wt% of 316L stainless steel powder, 3wt% of SiC powder and 0.5wt% of CeO2 powder.

[0038] Example 3: The preparation method of the car underbody protection plate disclosed in this example is different from that in Example 1. The raw material in step S1 is a composite powder composed of 316L stainless steel powder, SiC powder and CeO2 powder, wherein the weight percentage of each component is: 96wt% of 316L stainless steel powder, 3wt% of SiC powder and 1wt% of CeO2 powder.

[0039] Comparative Example 1: The method for preparing the car underbody protection plate disclosed in this comparative example differs from that in Example 1 in that the raw material in step S1 is pure 316L stainless steel powder, that is, the proportion of 316L stainless steel powder is 100%.

[0040] Comparative Example 2: The method for preparing the car underbody protection plate disclosed in this comparative example differs from that in Example 1 in that the raw materials in step S1 consist of 316L stainless steel powder and SiC powder, with the following weight percentages: 97wt% 316L stainless steel powder and 3wt% SiC powder.

[0041] In summary, the composition of the raw materials in all embodiments and comparative examples is shown in Table 1: Table 1: Powder composition (wt%) of each example and comparative example serial number type 316L SiC CeO2 Example 1 <![CDATA[316L / SiC / CeO2]]> 97.5 2 0.5 Example 2 <![CDATA[316L / SiC / CeO2]]> 96.5 3 0.5 Example 3 <![CDATA[316L / SiC / CeO2]]> 96 3 1 Comparative Example 1 Pure 316L 100 0 0 Comparative Example 2 316L / SiC 97 3 0 The performance of the samples in each embodiment and comparative example was tested and characterized.

[0042] The above embodiments and comparative examples were tested as follows: Grain structure analysis: After grinding and polishing, the grain state of the sample was observed by electron backscatter diffraction (EBSD).

[0043] Phase analysis: The phase composition of the sample was analyzed using an X-ray diffractometer with Cu target Kα rays as the light source and a scanning range of 20° to 90°.

[0044] Mechanical property testing: Tensile specimens were processed according to ASTM E8 standard and subjected to room temperature tensile tests on a universal testing machine at a tensile rate of 1 mm / min to test their tensile strength and elongation.

[0045] Wear resistance test: A ball-disc friction and wear tester (HT-1000 type) was used, with Φ6mm GCr15 steel balls as the wear material, a load of 15N, a frequency of 3Hz, and a wear time of 30min. The wear volume and wear rate were calculated using a white light interferometer.

[0046] The test results are summarized in Table 2.

[0047] Table 2: Comparison of Performance Test Results Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Tensile strength (MPa) 1301.5 803.7 1202.3 584.4 701.6 Elongation (%) 5.9 49.3 12.1 44.6 3.1 coefficient of friction 0.48 0.46 0.50 0.54 0.53 <![CDATA[Wear rate (10 ⁻4 mm³ / N·m)]]> 1.42 0.99 1.18 2.4 2.16

[0048] As shown in Table 2, the test results of Example 2 are superior to those of Comparative Examples 1 and 2, achieving improvements in tensile strength and friction reduction and wear resistance. Although Examples 1 and 3 show a significant increase in tensile strength compared to Comparative Examples 1 and 2, their elongation is significantly lower than that of Comparative Example 1, but their friction reduction and wear resistance are improved compared to Comparative Example 1. Therefore, Example 2 has the best overall performance. The results are analyzed below in conjunction with Comparative Example 1 and Example 2.

[0049] Structure and phases: Figure 2 This is the EBSD plot for Comparative Example 1. Figure 3 The EBSD diagram for Example 2 is shown below. Figure 2 and Figure 3 The EBSD images show that the grains in Example 2 are significantly finer than those in Comparative Example 1, indicating that the SiC / CeO2 powder at this ratio has a significant grain-refining effect on the 316L stainless steel material. Figure 4 The images shown are X-ray diffraction (XRD) patterns for various embodiments and comparative examples, where the horizontal axis represents the diffraction angle in degrees (deg), and the vertical axis represents the diffraction intensity in arbitrary units (au), such as... Figure 4 As shown, XRD did not detect the formation of a new phase, possibly due to the low doping content of the composite powder.

[0050] Mechanical properties: Figure 5 Mechanical curves for each embodiment and comparative example, such as Figure 5As shown, the strength of Example 2 of the present invention is much higher than that of Comparative Example 1 and similar to that of Comparative Example 2. More importantly, compared to Comparative Example 1, Examples 1 and 3, while showing a significant increase in strength, exhibited a sharp deterioration in elongation (from 44.6% to 5.9% and 12.1%, respectively), exhibiting typical brittle fracture. In contrast, Example 2 of the present invention, while showing a significant increase in strength (tensile strength approximately 37.5% higher than that of pure 316L stainless steel in Comparative Example 1), still maintains considerable ductility (elongation approximately 49.3%), achieving a synergistic improvement in strength and toughness.

[0051] Abrasion resistance: Figure 6 The graph shows the friction coefficient data for each embodiment and comparative example. Figure 7 The wear rate data graphs for each embodiment and comparative example are shown below. Figure 6 and Figure 7 As shown, all samples with added reinforcing phases (Examples 1, 2, 3 and Comparative Example 2) exhibited better coefficients of friction and wear rates than pure 316L stainless steel (Comparative Example 1). Example 2 of this invention, due to its combination of high hardness and good toughness, had the lowest coefficient of friction and wear rate, demonstrating the best wear resistance. The wear rate of Example 2 was reduced by approximately 58.8% and the coefficient of friction was reduced by approximately 14.8% compared to pure 316L stainless steel.

[0052] The above examples and comparative examples fully demonstrate that the present invention, by introducing a specific proportion of SiC / CeO2 composite powder into 316L stainless steel powder, successfully solves the problems of decreased density and deteriorated toughness caused by severe interfacial reactions during LPBF (Limited Particulate Fiber) processing, and obtains a composite material with high strength, high hardness, good toughness, and excellent wear resistance. In particular, Example 2 (3wt% SiC + 0.5wt% CeO2) achieves the best balance in strength, toughness, and wear resistance, and is the preferred embodiment.

[0053] The automotive underbody protection plate prepared by the preparation method in Example 2 not only has excellent protective performance and can extend its service life, but also can be printed with various complex shapes and high precision using LPBF equipment, which has broad market prospects.

[0054] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. For example, the laser power can be optimized and adjusted to be 200–300W, the scanning speed can be 800–1200 mm / s, the scanning spacing can be between 0.08 and 0.12 mm, and the layer thickness can be between 0.01 and 0.05 mm; the particle size of CeO2 particles can be selected within the range of 10 nm to 1 μm; the total addition amount of SiC powder and CeO2 powder can vary between 1 and 5 wt%, and the weight ratio of CeO2 powder to SiC powder is preferably between 1:6 and 1:3, all of which can achieve the purpose of the present invention.

Claims

1. A method of manufacturing an underbody shield for a vehicle, characterized by, The method comprises the following steps: S1, preparing raw materials and pretreating the raw materials; S2, loading the pretreated raw materials into a powder feeding cylinder of a laser powder bed melting equipment and printing an automobile underbody shield; S3, taking out the automobile underbody shield after printing and post-treating the automobile underbody shield; In step S1, the raw materials comprise 316L stainless steel powder, SiC powder and CeO2 powder, the total content of the SiC powder and the CeO2 powder is 1-5wt%, and the weight ratio of the CeO2 powder to the SiC powder is 1:6 to 1:

3.

2. The method of claim 1, wherein the underbody panel is made of a material selected from the group consisting of steel, aluminum, magnesium, and a combination thereof. The weight percentage of each component in the raw materials in step S1 is as follows: 316L stainless steel powder 96.5wt%, SiC powder 3wt% and CeO2 powder 0.5wt%.

3. The method of claim 1, wherein the underbody panel is made of a material selected from the group consisting of steel, aluminum, magnesium, and a combination thereof. The pretreatment of the raw materials in step S1 comprises the following steps: The CeO2 powder is mixed with anhydrous ethanol, and the mixture is treated by using an ultrasonic disrupter to form a preliminarily dispersed CeO2 suspension; The 316L stainless steel powder and the SiC powder are added into the CeO2 suspension, and stirring is performed until the CeO2 suspension uniformly wets all the powder particles to form a mixed slurry; The mixed slurry is placed in a vacuum rotary evaporator, and the ethanol solvent is slowly removed, during which the CeO2 particles adhere to and coat the surfaces of the 316L stainless steel particles and the SiC particles to obtain a composite powder; The obtained composite powder is dried and sieved to ensure the flowability of the composite powder.

4. The method of claim 1, wherein the underbody panel is made of a material selected from the group consisting of steel, aluminum, magnesium, and a combination thereof. The chemical composition of the 316L stainless steel powder is as follows: Cr: 16.5-18.5wt%, Ni: 10.0-14.0wt%, Mo: 2.0-3.0wt%, C: ≤0.03wt%, Si: ≤0.75wt%, Mn: ≤2.0wt%, P: ≤0.045wt%, S: ≤0.03wt%, and the balance is Fe.

5. The method of claim 1, wherein the underbody panel is made of a material selected from the group consisting of steel, aluminum, magnesium, and a combination thereof. The printing parameters in step S2 are as follows: laser power: 200-300W, scanning speed: 800-1200mm / s, scanning interval: 0.08-0.12mm, layer thickness: 0.01-0.05mm, scanning strategy: stripe scanning, and the scanning direction is rotated by 67° between adjacent layers.

6. The method of claim 1, wherein the underbody panel is made of a material selected from the group consisting of steel, aluminum, magnesium, and a combination thereof. The post-treatment of the automobile underbody shield in step S3 comprises the following steps: heating the automobile underbody shield to 900℃ at a rate of 5℃ / min under argon protection, maintaining the temperature for 2 hours, and taking out the automobile underbody shield after cooling to below 200℃.

7. The method of claim 1, wherein the underbody panel is made of a material selected from the group consisting of steel, aluminum, magnesium, and a combination thereof. The particle size of the CeO2 particles is 10nm-1μm.

8. The method of claim 1, wherein the underbody panel is made of a material selected from the group consisting of steel, aluminum, magnesium, and a combination thereof. The particle size of the SiC particles is 1-5μm.

9. The method of claim 1, wherein the underbody panel is made of a material selected from the group consisting of steel, aluminum, magnesium, and a combination thereof. The particle size of the 316L stainless steel particles is 15-53μm.

10. An underbody shield for an automobile, characterized by The automobile underbody shield is prepared by the method according to any one of claims 1-9. The automobile underbody shield is prepared by the method according to any one of claims 1-9.

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