A laser welding process and a method for producing welded parts by stamping

Abstract

The present invention relates to the technical field of steel laser welding, and more specifically, to a laser welding process for preventing white blistering after hot stamping of galvanized thermoformed steel and a method for producing welded parts by stamping. The laser welding process provided by the present invention performs a low-power laser post-treatment on the burrs on the back of the weld and the peeling zinc layer around the weld after laser welding. This removes burrs formed by re-solidification of zinc on the back of the weld and the peeling zinc layer near the weld, thereby producing welds with well-formed upper and lower surfaces, preventing white blister defects on the weld seams of the tailor-welded blanks after hot stamping, and improving the quality of the resulting parts.

Description

Technical Field

[0001] The invention relates to the technical field of steel laser welding, and in particular to a laser welding process and a method for producing welded parts by stamping. Background Art

[0002] The ultra-high strength of hot-formed steel can effectively reduce vehicle weight and improve safety, making it an ideal steel grade for lightweight automotive applications. Furthermore, hot-formed steel exhibits excellent stamping properties, resulting in high dimensional accuracy in formed parts. Consequently, hot-formed steel is increasingly being used in automotive applications.

[0003] Conventional cold-rolled hot-formed steel produces significant scale during the heating and stamping process, requiring shot blasting after forming. Furthermore, the exposed surface is prone to rust, shortening its service life. Coated hot-formed steel, however, offers excellent corrosion and oxidation resistance, and its share in hot-formed steel applications is gradually increasing.

[0004] Currently, the most common coated hot-formed steel is aluminum-silicon coated. With the introduction of patents such as CN112139335A and CN216420752U, galvanized hot-formed steel will see wider application after resolving the problem of liquid metal brittle cracks that are prone to occur during heated stamping. However, when laser welding galvanized hot-formed steel, burrs formed by the resolidification of zinc on the back of the weld and the peeling of the zinc layer near the weld can cause the zinc to overoxidize during heating, resulting in excessive zinc oxide, which adheres to the surface after stamping, causing white blister defects. Currently, patents for coated hot-formed steel primarily apply to aluminum-silicon coatings and do not address the white blister defect after stamping at the laser welded welds of galvanized hot-formed steel. Summary of the Invention

[0005] In response to the problem of white bubbles forming in the existing welded galvanized hot-formed steel after hot stamping, the present invention provides a laser welding process and a method for producing welded parts by stamping. After laser welding, excellent welds are formed on the surface, solving the technical problem of white bubble defects forming at the weld seams of the welded plates when hot stamping is used to produce welded parts.

[0006] In a first aspect, the present invention provides a laser welding process for preventing white blistering of galvanized hot-formed steel after hot stamping, comprising the following steps:

[0007] (1) Laser welding of galvanized hot-formed steel tailor-welded plates;

[0008] (2) The burrs on the back of the weld and the peeling zinc layer around the weld are removed by laser burning after laser welding.

[0009] Furthermore, the specific process of laser welding in step (1) is as follows:

[0010] (11) Keep the cleaned galvanized hot-formed steel tailor-welded sheet with the burr edge facing upwards and fix it with a clamp so that the cut edges of the two sheets of the tailor-welded sheet are butted together without any gap;

[0011] (12) Laser welding of tailor-welded plates using laser welding equipment.

[0012] Furthermore, the specific process of laser welding in step (12) is as follows: the thickness of the burr of the welded plate is d, and d can be measured by the maximum thickness;

[0013] When 0≤d<30μm, the welding speed is 0.03~0.10m / s, the laser power is 1800~2800W, the tilt angle is -5~+5°, the defocus is +0~5mm, and the shielding gas is inert gas;

[0014] When 30μm≤d<80μm, the welding speed is 0.03~0.10m / s, the laser power is 2000~3000W, the tilt angle is -5~+5°, the defocus is +2~7mm, and the shielding gas is inert gas;

[0015] When d≥80μm, the welding speed is 0.03~0.10m / s, the laser power is 2000~3200W, the tilt angle is -5~+5°, the defocus amount is +5~10mm, and the shielding gas is inert gas.

[0016] Furthermore, in step (2), laser welding equipment is used for laser burning, and the specific process is: laser power is 300~800W, welding speed is 0.03~0.10m / s, tilt angle is -5~+5°, defocus amount is +5~10mm, and shielding gas is inert gas.

[0017] Furthermore, the laser trajectory of the laser burning moves along a single track, multiple straight tracks or a wavy track.

[0018] In a second aspect, the present invention provides a method for producing tailor-welded parts by hot stamping galvanized hot-formed steel using the laser tailor-welding process, comprising the following steps:

[0019] S1. Placing the laser-welded galvanized hot-formed steel in a heating furnace for heating;

[0020] S2, after heating, the galvanized hot-formed steel is transferred to a cooling medium for cooling;

[0021] S3. After cooling, the galvanized hot-formed steel is formed, pressure-maintained, and quenched under the action of a mold to obtain a welded part.

[0022] Furthermore, in step S1, the heating temperature in the heating furnace is AC3-905°C, and the material is heated to a completely austenitized state while preventing zinc from gasifying. The heating and holding time is 3-8 minutes.

[0023] Furthermore, in step S2, the cooling medium is boiling water, and the cooling time is 3 to 6 seconds.

[0024] The beneficial effect of the present invention is that the laser welding process provided by the present invention performs low-power laser burning post-treatment on the burrs on the back of the weld and the peeling zinc layer around the weld after welding, thereby removing the burrs formed by the re-solidification of zinc on the back of the weld and the peeling zinc layer near the weld, thereby obtaining welds with excellent upper and lower surface formation, preventing white bubble defects from occurring at the weld seams of the welded plates after hot stamping, and improving the quality of the manufactured parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0026] Figure 1 This is a photograph of the weld morphology on the back of the welded part after hot stamping in Example 3 of the specific embodiment of the present invention.

[0027] Figure 2 This is a photograph of the weld morphology on the back of the welded part after hot stamping in Example 4 of the specific embodiment of the present invention.

[0028] Figure 3 This is a photograph of the weld morphology on the back of a tailor-welded part after hot stamping in a comparative example of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0030] Example 1

[0031] A laser welding process for preventing white blistering of galvanized hot-formed steel after hot stamping, comprising the following steps:

[0032] (1) The cleaned galvanized hot-formed steel tailor-welded sheet is fixed with the burr edge facing upwards, and fixed with a clamp so that the cut edges of the two sheets of the tailor-welded sheet are butted together without gaps. The tailor-welded sheet is laser welded using a laser welding device. According to the thickness of the cut edge burr of the tailor-welded sheet being 30 μm, the specific process of laser welding is as follows: welding speed 0.060 m / s, laser power 2500 W, tilt angle +5°, defocus amount +4.5 mm, and shielding gas is inert gas;

[0033] (2) The burrs on the back of the weld and the peeling zinc layer around the weld after laser welding were removed by laser burning. The thickness of the burrs on the edge of the welded plate was 20 μm, the laser power was 500 W, the welding speed was 0.06 m / s, the tilt angle was +4°, the defocus amount was +8 mm, the shielding gas was inert gas, and the laser trajectory of laser burning was a double-track straight trajectory. The debris was removed by blowing the shielding gas to produce a galvanized hot-formed steel welded plate. There were no burrs, peeling and other defects on the front and back welds of the welded plate.

[0034] Example 2

[0035] A laser welding process for preventing white blistering of galvanized hot-formed steel after hot stamping, comprising the following steps:

[0036] (1) The cleaned galvanized hot-formed steel tailor-welded sheet is fixed with the burr edge facing upwards, and fixed with a clamp so that the cut edges of the two sheets of the tailor-welded sheet are butted together without gaps. The tailor-welded sheet is laser welded using a laser welding device. According to the thickness of the cut edge burr of the tailor-welded sheet being 20 μm, the specific process of laser welding is as follows: welding speed 0.08 m / s, laser power 2300 W, tilt angle +3°, defocus amount +3 mm, and shielding gas is inert gas;

[0037] (2) The burrs on the back of the weld and the peeling zinc layer around the weld after laser welding were removed by laser burning. The thickness of the burrs on the edge of the welded plate was 20 μm, the laser power was 800 W, the welding speed was 0.10 m / s, the tilt angle was -5°, the defocus amount was +5 mm, the shielding gas was inert gas, and the laser trajectory of the laser burning was along a single straight line. The debris was removed by blowing the shielding gas to produce a galvanized hot-formed steel welded plate. There were no burrs, peeling and other defects on the front and back welds of the welded plate.

[0038] Example 3

[0039] This embodiment uses the galvanized hot-formed steel tailor-welded blanks prepared in Example 1 to produce tailor-welded parts by hot stamping. The specific method includes the following steps:

[0040] S1. Place the laser-welded galvanized hot-formed steel tailor-welded blanks in a heating furnace and heat them to 870°C for 8 minutes;

[0041] S2, after heating, the galvanized hot-formed steel is transferred to a boiling water cooling medium for cooling, and the cooling time is 6s;

[0042] S3. After cooling, the galvanized hot-formed steel is formed, pressure-maintained, and quenched under the action of a mold to obtain a welded part.

[0043] Example 4

[0044] This embodiment uses the galvanized hot-formed steel tailor-welded blanks prepared in Example 2 to produce tailor-welded parts by hot stamping. The specific method includes the following steps:

[0045] S1. Place the laser-welded galvanized hot-formed steel tailor-welded blanks in a heating furnace and heat them to 905°C for 3 minutes;

[0046] S2. After heating, the galvanized hot-formed steel is transferred to a boiling water cooling medium for cooling. The cooling time is 5s.

[0047] S3. After cooling, the galvanized hot-formed steel is formed, pressure-maintained, and quenched under the action of a mold to obtain a welded part.

[0048] Comparative Example

[0049] The comparative example uses the galvanized hot-formed steel tailor-welded blank obtained in Example 1 without performing step (2), and uses the method described in Example 3 to produce the tailor-welded parts by hot stamping.

[0050] Figure 1 、 Figure 2 The morphologies of the weld seams on the back of the tailor-welded parts after hot stamping of Example 3 and Example 4 are shown respectively. It can be seen that no white bubble defects occur at the weld seams of the tailor-welded parts produced by hot stamping of Example 3 and Example 4, and the appearance quality is good.

[0051] Figure 3 The figure shows the morphology of the weld seam on the back of the comparative hot stamping tailor-welded part. It can be seen that white bubble defects exist in the weld seam of the comparative hot stamping tailor-welded part.

[0052] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and substance of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any changes or substitutions that can be readily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.

Claims

1. A laser welding process for preventing white blistering of galvanized hot-formed steel after hot stamping, characterized in that: The steps include: (1) Laser welding of galvanized hot-formed steel tailor-welded plates; (2) Laser burning is performed to remove the burrs on the back of the weld and the peeling zinc layer around the weld after laser welding; The specific process of laser welding in step (1) is: (11) Keep the cleaned galvanized hot-formed steel tailor-welded sheet with the burr edge facing upwards and fix it with a clamp so that the cut edges of the two sheets of the tailor-welded sheet are butted together without any gap; (12) Laser welding of tailor-welded plates using laser welding equipment; The specific process of laser welding in step (12) is as follows: the thickness of the burr on the edge of the welded plate is d; When 0≤d<30μm, the welding speed is 0.03~0.10m / s, the laser power is 1800~2800W, the tilt angle is -5~+5°, the defocus is +0~5mm, and the shielding gas is inert gas; When 30μm≤d<80μm, the welding speed is 0.03~0.10m / s, the laser power is 2000~3000W, the tilt angle is -5~+5°, the defocus is +2~7mm, and the shielding gas is inert gas; When d≥80μm, the welding speed is 0.03~0.10m / s, the laser power is 2000~3200W, the tilt angle is -5~+5°, the defocus is +5~10mm, and the shielding gas is inert gas; In step (2), laser welding equipment is used for laser burning, and the specific process is: laser power is 300~800W, welding speed is 0.03~0.10m / s, tilt angle is -5~+5°, defocus amount is +5~10mm, and shielding gas is inert gas.

2. The laser welding process for preventing white blistering of galvanized hot-formed steel after hot stamping according to claim 1, characterized in that: The laser trajectory of laser burning is along a single track, multiple straight tracks or wavy tracks.

3. A method for producing welded parts by hot stamping galvanized hot-formed steel using the laser welding process according to claim 1, characterized in that: The steps include: S1. Placing the laser-welded galvanized hot-formed steel in a heating furnace for heating; S2, after heating, the galvanized hot-formed steel is transferred to a cooling medium for cooling; S3. After cooling, the galvanized hot-formed steel is formed, pressure-maintained, and quenched under the action of a mold to obtain a welded part.

4. The method according to claim 3, wherein In step S1, the heating temperature in the heating furnace is AC3-905°C, and the heating and holding time is 3-8 minutes.

5. The method according to claim 3, wherein In step S2, the cooling medium is boiling water, and the cooling time is 3 to 6 seconds.

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