A galvanized martensitic steel rolled profile and a method for producing it

Abstract

The application provides a galvanized martensitic steel roll-shaped section and a preparation method thereof, and relates to the technical field of welding.The second and third fillet regions are locally heated before the first laser welding, the first fillet region is locally heated before the second laser welding, and the heating temperature is controlled at 500-700 DEG C.The material of the fillet region is softened by local heating, the yield strength and resilience of the three fillet regions are reduced, the roll residual stress originally concentrated in the weld and the heat affected zone is transferred and released to the fillet softened region with lower yield strength, and thus the instant cracks and delayed cracks are effectively eliminated.For the preparation of the galvanized martensitic steel roll-shaped section by using the process of "segmented roll forming + two laser weldings", the method of the application can eliminate the instant cracks in the roll forming process and the delayed cracks after the product is placed, and ensure the forming precision.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more specifically, to a galvanized martensitic steel roll-formed profile and its preparation method. Background Technology

[0002] Galvanized martensitic steel (such as MS1500) is widely used in safety structural components such as anti-collision beams and battery pack edge beams in new energy vehicles due to its ultra-high strength and corrosion resistance. The typical production process for roll-formed profiles used in these safety structural components is: roll forming - laser welding - shaping and cutting. To reduce the forming difficulty of roll-formed profiles and ensure dimensional accuracy, a "segmented roll forming + two-stage laser welding" process is often adopted. However, during the subsequent roll forming process after the first laser welding, immediate cracks are prone to appear in the weld. More seriously, some products develop delayed cracks after being left for several hours, resulting in a persistently high scrap rate. Summary of the Invention

[0003] The problem solved by this invention is: how to eliminate instantaneous cracks and delayed cracks, and ensure forming accuracy, for galvanized martensitic steel roll-formed profiles prepared by the "segmented roll forming + two-stage laser welding" process.

[0004] To address the above problems, this invention provides a method for preparing a galvanized martensitic steel roll-formed profile. The galvanized martensitic steel roll-formed profile is a closed structure formed by multiple roll forming processes from a single galvanized martensitic steel sheet, comprising a first cavity and a second cavity arranged in parallel. The preparation method includes: Step S1: After pretreatment of the galvanized martensitic steel sheet, it is subjected to a first roll forming to obtain a first intermediate profile sample with a semi-closed structure; the first intermediate profile sample includes a first upper wall, a left side wall, a lower wall, a right side wall, a second upper wall, and a middle inclined wall connected in sequence; one end of the first upper wall is connected to the left side wall, and the other end is a free end; the middle inclined wall overlaps the lower wall to form a first overlapping area, thereby dividing the lower wall into a lower left wall segment and a lower right wall segment; the left side wall, the first upper wall, the middle inclined wall, and the lower left wall segment are used to subsequently enclose and form the first cavity; the middle inclined wall, the second upper wall, the right side wall, and the lower right wall segment are used to subsequently enclose and form the second cavity; a first rounded corner area is formed between the left side wall and the lower left wall segment, a second rounded corner area is formed between the right side wall and the second upper wall, and a third rounded corner area is formed between the right side wall and the lower right wall segment; Step S2: After the second rounded corner area and the third rounded corner area are locally heated for the first time, the first overlapping area is laser welded for the first time to fix the middle inclined wall to the lower wall, thereby forming the second cavity and obtaining the second intermediate profile sample; wherein, the temperature of the first local heating is 500℃ to 700℃; Step S3: Perform a second roll forming on the second intermediate profile sample so that the free end of the first upper wall overlaps the upper end of the intermediate inclined wall to form a second overlapping area. After the first rounded corner area is locally heated for the second time, the second overlapping area is immediately laser welded for the second time so that the intermediate inclined wall is fixedly connected to the first upper wall, thereby forming the first cavity and obtaining the galvanized martensitic steel roll-formed profile; wherein, the temperature of the second local heating is 500℃ to 700℃.

[0005] Optionally, both the first local heating and the second local heating are performed using high-frequency induction heating.

[0006] Optionally, the power of the high-frequency induction heating is 5kW to 9kW.

[0007] Optionally, in step S2, the duration of the first local heating is 3 to 18 seconds.

[0008] Optionally, in step S2, the power of the first laser welding is 10kW to 14kW, and the speed is 2m / min to 10m / min.

[0009] Optionally, in step S3, the duration of the second local heating is 3 to 18 seconds.

[0010] Optionally, in step S3, the power of the second laser welding is 10kW to 14kW, and the speed is 2m / min to 10m / min.

[0011] Optionally, in step S1, the pretreatment of the galvanized martensitic steel sheet includes: scraping the area of ​​the galvanized martensitic steel sheet to be welded so that the thickness of the residual zinc layer in the area to be welded is less than 5 μm.

[0012] Optionally, in step S1, the thickness of the galvanized martensitic steel plate is 1 mm to 2 mm.

[0013] The present invention also provides a galvanized martensitic steel roll-formed profile, which is manufactured using the galvanized martensitic steel roll-formed profile preparation method described above.

[0014] Compared with related technologies, this invention preheats the second and third rounded corner areas before the first laser welding, and then preheats the first rounded corner area before the second laser welding, controlling the heating temperature between 500℃ and 700℃. This localized heating softens the material in the rounded corner areas, reducing the yield strength and springback resistance of all three areas. This allows the residual stress from rolling, originally concentrated in the weld and heat-affected zone, to be transferred and released to the softened rounded corner areas with lower yield strength, effectively eliminating both immediate and delayed cracks. Furthermore, this method does not require heating the entire steel plate; it only heats the target areas to soften the stress, avoiding overall annealing and softening of the profile. This preserves the original high strength of the martensitic steel to the greatest extent and effectively reduces dimensional deviations caused by rounded corner springback, significantly improving the final forming accuracy of the rolled profile. Additionally, heating only the rounded corner areas avoids excessive damage to the galvanized layer in non-processed areas, effectively ensuring the overall corrosion resistance of the finished product and extending its service life. In summary, for the preparation of galvanized martensitic steel roll-formed profiles using the "segmented roll forming + two-stage laser welding" process, the method of this invention can eliminate instantaneous cracks during the roll forming process and delayed cracks after product placement, while ensuring forming accuracy. Attached Figure Description

[0015] Figure 1 This is a schematic cross-sectional view of the roll-formed profile in an embodiment of the present invention; Figure 2 This is a schematic cross-sectional view of the first intermediate profile sample in an embodiment of the present invention; Figure 3 This is a schematic diagram of the deformation process of the first upper wall during the second roll forming process in an embodiment of the present invention.

[0016] Explanation of reference numerals in the attached figures: 1. First cavity; 2. Second cavity; 3. First upper wall; 4. Left side wall; 5. Lower wall; 51. Lower left wall segment; 52. Lower right wall segment; 6. Right side wall; 7. Second upper wall; 8. Middle inclined wall; 9. First rounded corner area; 10. Second rounded corner area; 11. Third rounded corner area. Detailed Implementation

[0017] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0019] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0020] This invention provides a method for preparing galvanized martensitic steel roll-formed profiles, such as... Figure 1 As shown, the galvanized martensitic steel roll-formed profile is a closed structure formed by multiple roll forming processes from a single galvanized martensitic steel sheet, including a first cavity 1 and a second cavity 2 arranged side by side. The preparation method includes: Step S1: After pretreatment, the galvanized martensitic steel sheet undergoes a first roll forming process to obtain a first intermediate profile sample with a semi-closed structure; for example... Figure 2 As shown, the first intermediate profile sample includes a first upper wall 3, a left side wall 4, a lower wall 5, a right side wall 6, a second upper wall 7, and a middle inclined wall 8 connected in sequence; one end of the first upper wall 3 is connected to the left side wall 4, and the other end is a free end; the middle inclined wall 8 overlaps the lower wall 5 to form a first overlapping area, thereby dividing the lower wall 5 into a left lower wall segment 51 and a right lower wall segment 52; the left side wall 4, the first upper wall 3, the middle inclined wall 8, and the left lower wall segment 51 are used to subsequently enclose and form the first cavity 1; the middle inclined wall 8, the second upper wall 7, the right side wall 6, and the right lower wall segment 52 are used to subsequently enclose and form the second cavity 2; a first rounded corner area 9 is formed between the left side wall 4 and the left lower wall segment 51, a second rounded corner area 10 is formed between the right side wall 6 and the second upper wall 7, and a third rounded corner area 11 is formed between the right side wall 6 and the right lower wall segment 52; Step S2: After the second rounded corner area 10 and the third rounded corner area 11 are locally heated for the first time, the first overlapping area is laser welded for the first time so that the intermediate inclined wall 8 is fixedly connected to the lower wall 5, thereby forming the second cavity 2 and obtaining the second intermediate profile sample; wherein, the temperature of the first local heating is 500℃ to 700℃; Step S3, as follows Figure 3 As shown, the second intermediate profile sample is subjected to a second roll forming so that the free end of the first upper wall 3 overlaps the upper end of the intermediate inclined wall 8 to form a second overlapping area. After the first rounded corner area 9 is subjected to a second local heating, the second overlapping area is immediately subjected to a second laser welding so that the intermediate inclined wall 8 is fixedly connected to the first upper wall 3, thereby forming the first cavity 1 and obtaining the galvanized martensitic steel roll-formed profile; wherein, the temperature of the second local heating is 500℃ to 700℃.

[0021] In this embodiment of the invention, the second rounded corner region 10 and the third rounded corner region 11 are locally heated before the first laser welding, and the first rounded corner region 9 is locally heated before the second laser welding, with the heating temperature controlled between 500℃ and 700℃. This localized heating softens the material in the rounded corner regions, reducing the yield strength and springback resistance of the three rounded corner regions. This allows the residual stress from rolling, originally concentrated in the weld and heat-affected zone, to be transferred and released to the softened rounded corner regions with lower yield strength, effectively eliminating both immediate and delayed cracks. Furthermore, this method does not require heating the entire steel plate; heating only the target area for stress transfer avoids overall annealing and softening of the profile, maximizing the preservation of the original high strength properties of the martensitic steel. It also effectively reduces dimensional deviations caused by rounded corner springback, significantly improving the final forming accuracy of the rolled profile. Additionally, heating only the rounded corner regions avoids excessive damage to the galvanized layer in the non-processed areas of the profile, effectively ensuring the overall corrosion resistance of the finished product and extending its service life. In summary, for the preparation of galvanized martensitic steel roll-formed profiles using the "segmented roll forming + two-stage laser welding" process, the method of this invention can eliminate instantaneous cracks during the roll forming process and delayed cracks after product placement, while ensuring forming accuracy.

[0022] In some embodiments of the present invention, preferably, both the first local heating and the second local heating are performed using high-frequency induction heating. The skin effect of high-frequency induction heating allows for precise local heating of only the target rounded corner area, without affecting the weld base material or other non-target areas. This ensures that the rounded corner area reaches a softening temperature of 500°C to 700°C without causing changes in the microstructure of other areas. Compared to laser heating, the advantage of using high-frequency induction heating is that it avoids damage to the zinc layer on the surface of the galvanized martensitic steel sheet and also prevents weld cracks and main body cracks from appearing in the roll-formed profile samples during side impact performance testing.

[0023] In some embodiments of the present invention, the power of the high-frequency induction heating is 5kW to 9kW. In this embodiment, by controlling the power of the induction heating to 5kW to 9kW, it is possible to avoid excessive heat diffusion caused by slow heating, which could lead to overall deformation of the steel plate. It is also possible to prevent the heating area from heating too quickly, which could lead to surface overheating and local melting. At the same time, it is possible to avoid excessive expansion of the heat-affected zone, which could damage the original high-strength properties of the martensitic steel plate matrix.

[0024] In some embodiments of the present invention, in step S2, the duration of the first local heating is 3 to 18 seconds, and the duration of the second local heating is 3 to 18 seconds. In this embodiment, the local heating time is controlled between 3 and 18 seconds. The lower limit of 3 seconds ensures that the target rounded corner area receives sufficient heat input to reach the target softening temperature of 500°C to 700°C, avoiding insufficient heating that would result in inadequate softening of the rounded corner and failure to effectively transfer and release residual stress from rolling. The upper limit of 18 seconds avoids excessive heating time that would cause heat to diffuse into the matrix, reducing unnecessary energy consumption and preventing excessive tempering and softening of the martensitic matrix. At the same time, it avoids overall deformation of the profile, ensuring that the softening range is limited to the target rounded corner area.

[0025] In some embodiments of the present invention, in step S2, the power of the first laser welding is 10kW to 14kW, and the speed is 2m / min to 10m / min; in some embodiments of the present invention, in step S3, the power of the second laser welding is 10kW to 14kW, and the speed is 2m / min to 10m / min. In this embodiment, controlling the laser welding power to 10kW to 14kW and the welding speed to 2m / min to 10m / min is suitable for the lap laser welding requirements of thick galvanized martensitic steel plates. The lower limit power of 10kW can ensure sufficient energy input to achieve full penetration welding of the first lap area, avoiding defects such as incomplete penetration and poor fusion. The upper limit power of 14kW can avoid excessive laser energy leading to an excessively wide weld and an excessively large heat-affected zone. The speed range of 2m / min to 10m / min can improve welding production efficiency while ensuring sufficient heat input and providing time for zinc vapor to escape, reducing porosity defects, and is suitable for batch production requirements.

[0026] In some embodiments of the present invention, step S1, the pretreatment of the galvanized martensitic steel plate, includes: scraping the area to be welded of the galvanized martensitic steel plate to reduce the thickness of the residual zinc layer in the area to be welded to less than 5 μm. In this embodiment, controlling the thickness of the residual zinc layer in the area to be welded to less than 5 μm can reduce the amount of gas generated by zinc vaporization during laser welding from the source, avoiding the formation of porosity and spatter defects due to excessive zinc vapor not escaping in time. It can also prevent the formation of low-melting-point eutectic structures at the molten pool boundary due to excessive zinc, reducing the tendency for crystallization cracks, improving the crack resistance and mechanical strength of the weld, and reducing the interference of zinc vapor on the laser beam, improving the stability of the laser welding process, and improving the weld formation quality.

[0027] In some embodiments of the present invention, in step S1, for example, the galvanized martensitic steel plate is made of MS1500 galvanized steel and the thickness of the galvanized martensitic steel plate is 1 mm to 2 mm.

[0028] This invention also provides a galvanized martensitic steel roll-formed profile, which is manufactured using the method described above for preparing galvanized martensitic steel roll-formed profiles. Exemplarily, this galvanized martensitic steel roll-formed profile is used to manufacture automotive door sill beams.

[0029] The present invention will be further described below with reference to specific embodiments.

[0030] Example 1 A1. The area to be welded on the galvanized martensitic steel sheet is scraped to reduce the thickness of the residual zinc layer in the area to less than 3 μm. Then, a first roll forming is performed to obtain a first intermediate profile sample with a semi-closed structure. The first intermediate profile sample includes a first upper wall, a left side wall, a lower wall, a right side wall, a second upper wall, and a middle inclined wall connected in sequence. One end of the first upper wall is connected to the left side wall, and the other end is a free end. The middle inclined wall overlaps the lower wall to form a first overlapping area, thereby dividing the lower wall into a lower left wall segment and a lower right wall segment. The left side wall, the first upper wall, the middle inclined wall, and the lower left wall segment are used to subsequently enclose and form the first cavity. The inclined wall, the second upper wall, the right side wall, and the lower right wall section are used to subsequently enclose and form the second cavity; a first rounded corner area is formed between the left side wall and the lower left wall section, a second rounded corner area is formed between the right side wall and the second upper wall, and a third rounded corner area is formed between the right side wall and the lower right wall section; the included angle of the straight edges of the first rounded corner area, the second rounded corner area, and the third rounded corner area is 97.5 degrees, and the arc length of the outer arc of the cross section of the first rounded corner area, the second rounded corner area, and the third rounded corner area is 12mm; the galvanized martensitic steel plate is made of MS1500 galvanized steel, and the thickness of the galvanized martensitic steel plate is 1.6mm.

[0031] A2. After the second rounded corner area and the third rounded corner area are locally heated for the first time, the first overlapping area is immediately laser welded to fix the intermediate inclined wall to the lower wall, thereby forming the second cavity and obtaining the second intermediate profile sample; wherein, the first local heating is performed by high-frequency induction heating, the power of the high-frequency induction heating is 7kW, the temperature of the first local heating is 600℃, and the time is 6s; the power of the first laser welding is 12kW, and the speed is 6m / min.

[0032] A3. The second intermediate profile sample is subjected to a second roll forming so that the free end of the first upper wall overlaps the upper end of the intermediate inclined wall to form a second overlapping area. After the first rounded corner area is subjected to a second local heating, the second overlapping area is immediately subjected to a second laser welding to fix the intermediate inclined wall to the first upper wall, thereby forming the first cavity and obtaining a galvanized martensitic steel roll-formed profile. The second local heating is performed by high-frequency induction heating with a power of 7kW, a temperature of 600℃, and a time of 6s. The second laser welding has a power of 12kW and a speed of 6m / min. The length of the galvanized martensitic steel roll-formed profile is 2054mm, the cross-sectional width is 128mm, and the cross-sectional height is 67mm.

[0033] Example 2 The difference from Example 1 is that the temperature of the first local heating and the second local heating is 500°C.

[0034] Example 3 The difference from Example 1 is that the temperature of the first local heating and the second local heating is 700°C.

[0035] Comparative Example 1 The difference from Embodiment 1 is that, in step A2, the second rounded corner region and the third rounded corner region are not locally heated; and in step A3, the first rounded corner region is not locally heated.

[0036] Comparative Example 2 The difference from Example 1 is that the temperature of the first local heating and the second local heating is 350°C.

[0037] Comparative Example 3 The difference from Example 1 is that both the first local heating and the second local heating are performed by laser heating, with a laser heating power of 4kW.

[0038] Comparative Example 4 The difference from Example 1 is that both the first local heating and the second local heating are performed by laser heating, with a laser heating power of 3.5kW.

[0039] Effect Example The instantaneous cracks and delayed cracks after product placement during the roll forming process in Examples 1 to 3 and Comparative Examples 1 to 2 were statistically analyzed, and the results are shown in Table 1. The included angle (R3) of the straight edge of the third rounded corner area of ​​the roll-formed profiles obtained in Examples 1 to 3 was also tested, and the results are shown in Table 1. As can be seen from Table 1, compared with Comparative Example 1, the instantaneous cracks and delayed cracks in Examples 1 to 3 were significantly improved. Compared with Comparative Example 2, the delayed cracks in Examples 1 to 3 were significantly improved. Compared with Comparative Examples 1 and 2, the springback amount of the rounded corner area of ​​the roll-formed profiles obtained in Examples 1 to 3 was smaller, indicating that the forming accuracy of the roll-formed profiles was higher.

[0040] Table 1

[0041] Observations on the zinc layer damage in the heated areas of the roll-formed profiles prepared in Examples 1 to 3 and Comparative Examples 3 to 4 revealed that the zinc layer in the heated areas of the roll-formed profiles prepared in Comparative Examples 3 to 4 showed significant damage, while the zinc layer in the heated areas of the roll-formed profiles prepared in Examples 1 to 3 did not show significant damage. Side impact performance tests were conducted on the roll-formed profiles prepared in Examples 1 to 3 and Comparative Examples 3 to 4, and the crack patterns after the impact tests were statistically analyzed. The results are shown in Table 2. Table 2 shows that the roll-formed profiles prepared in Examples 1 to 3 have better impact resistance compared to Comparative Examples 3 to 4.

[0042] Table 2

[0043] It should be noted that the first weld refers to the weld produced during the first laser welding; the second weld refers to the weld produced during the second laser welding; and the main crack refers to the crack in the area of ​​the roll-formed profile other than the weld.

[0044] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for preparing galvanized martensitic steel roll-formed profiles, characterized in that, The galvanized martensitic steel roll-formed profile is a closed structure formed by multiple roll forming processes from a galvanized martensitic steel sheet, including a first cavity (1) and a second cavity (2) arranged in parallel. The preparation method includes: Step S1: After pretreatment of the galvanized martensitic steel sheet, it is rolled for the first time to obtain a first intermediate profile sample with a semi-closed structure; the first intermediate profile sample includes a first upper wall (3), a left side wall (4), a lower wall (5), a right side wall (6), a second upper wall (7), and a middle inclined wall (8) connected in sequence; one end of the first upper wall (3) is connected to the left side wall (4), and the other end is a free end; the middle inclined wall (8) overlaps the lower wall (5) to form a first overlapping area, thereby dividing the lower wall (5) into a left lower wall segment (51) and a right lower wall segment (52); the left side wall (4) The first upper wall (3), the middle inclined wall (8), and the lower left wall segment (51) are used to subsequently enclose and form the first cavity (1); the middle inclined wall (8), the second upper wall (7), the right side wall (6), and the lower right wall segment (52) are used to subsequently enclose and form the second cavity (2); a first rounded corner area (9) is formed between the left side wall (4) and the lower left wall segment (51), a second rounded corner area (10) is formed between the right side wall (6) and the second upper wall (7), and a third rounded corner area (11) is formed between the right side wall (6) and the lower right wall segment (52); Step S2: After the second rounded corner area (10) and the third rounded corner area (11) are subjected to the first local heating, the first overlapping area is immediately subjected to the first laser welding so that the intermediate inclined wall (8) is fixedly connected to the lower wall (5) to form the second cavity (2) and obtain the second intermediate profile sample; wherein, the temperature of the first local heating is 500°C to 700°C; Step S3: Perform a second roll forming on the second intermediate profile sample so that the free end of the first upper wall (3) overlaps the upper end of the intermediate inclined wall (8) to form a second overlapping area. After the first rounded corner area (9) is heated for the second time, the second overlapping area is immediately laser welded for the second time so that the intermediate inclined wall (8) is fixedly connected to the first upper wall (3) to form the first cavity (1) and obtain the galvanized martensitic steel roll profile; wherein, the temperature of the second local heating is 500℃ to 700℃.

2. The method for preparing galvanized martensitic steel roll-formed profiles according to claim 1, characterized in that, Both the first and second local heating are performed using high-frequency induction heating.

3. The method for preparing galvanized martensitic steel roll-formed profiles according to claim 2, characterized in that, The power of the high-frequency induction heating is 5kW to 9kW.

4. The method for preparing galvanized martensitic steel roll-formed profiles according to claim 1, characterized in that, In step S2, the duration of the first local heating is 3 to 18 seconds.

5. The method for preparing galvanized martensitic steel roll-formed profiles according to claim 1, characterized in that, In step S2, the power of the first laser welding is 10kW to 14kW, and the speed is 2m / min to 10m / min.

6. The method for preparing galvanized martensitic steel roll-formed profiles according to claim 1, characterized in that, In step S3, the duration of the second local heating is 3 to 18 seconds.

7. The method for preparing galvanized martensitic steel roll-formed profiles according to claim 1, characterized in that, In step S3, the power of the second laser welding is 10kW to 14kW, and the speed is 2m / min to 10m / min.

8. The method for preparing galvanized martensitic steel roll-formed profiles according to claim 1, characterized in that, In step S1, the pretreatment of the galvanized martensitic steel plate includes: scraping the area of ​​the galvanized martensitic steel plate to be welded so that the thickness of the residual zinc layer in the area to be welded is less than 5 μm.

9. The method for preparing galvanized martensitic steel roll-formed profiles according to claim 1, characterized in that, In step S1, the thickness of the galvanized martensitic steel plate is 1 mm to 2 mm.

10. A galvanized martensitic steel roll-formed profile, characterized in that, It is manufactured using the method for preparing galvanized martensitic steel roll-formed profiles as described in any one of claims 1 to 9.

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