CN-122007629-A - Laser welding method for thermal forming steel butt joint based on annular light spot

Abstract

The invention discloses a laser welding method of a hot forming steel butt joint based on annular light spots, which relates to the technical field of laser welding. According to the invention, through the two-step energy input and pulse action mode of preheating and welding, the accurate and flexible control of heat input is realized, the first-step annular facula preheating can slow down the cooling shrinkage of a subsequent molten pool, the second-step central facula welding realizes rapid penetration, and the combination strategy is matched with pulse regulation, so that the defects of air holes, splashing, poor fusion and the like can be effectively inhibited, and the weld forming quality and joint reliability are obviously improved.

Inventors

• HUANG HAOJIE
• YANG SHANGLEI
• WANG JINQI
• ZHENG ZHAOZHU
• XIONG FENG
• LIANG JUNHUI

Assignees

• 上海工程技术大学

Dates

Publication Date

20260512

Application Date

20260122

Claims (9)

1. 1. The laser welding method for the thermal forming steel butt joint based on the annular light spot comprises the step of welding the thermal forming steel butt joint by adopting an annular light spot laser and is characterized in that the welding method adopts a pulse welding mode, and the formation of each pulse welding spot comprises two stages: The first step is a heating stage, wherein an annular pulse light spot with the ratio of the central laser power to the annular laser power ranging from (0.5 to 3.0) is adopted to preheat a welding seam area to form an unmelted circular heating area, and the second step is a welding stage, wherein the annular pulse light spot with the ratio of the central laser power to the annular laser power ranging from (9.5 to 7.0) is adopted to weld the preheated welding seam area to enable the preheated welding seam area to be melted to form a molten pool; a continuous butt weld is formed by sequentially superimposing a plurality of single pulse welds in the direction of the weld.
2. 2. The laser welding method of the butt joint of the hot forming steel based on the annular light spot according to claim 1, wherein the ratio of the central laser power to the annular laser power is 1:9 in the heating stage.
3. 3. The laser welding method of the butt joint of the hot forming steel based on the annular light spot according to claim 1, wherein the preferable ratio of the central laser power to the annular laser power is 9:1 in the welding stage.
4. 4. The laser welding method for the hot-forming steel butt joint based on the annular light spot is characterized in that the overlapping mode of the pulse welding spots is that the overlapping length b of the adjacent welding spots in the length direction of the welding spots meets the condition that b= (0.25-0.5) C is the diameter of the annular light spot.
5. 5. The laser welding method for the hot forming steel butt joint based on the annular light spot, which is disclosed in claim 4, is characterized in that the superposition mode of the pulse welding spots is that the superposition height a of adjacent welding spots in the height direction of the welding spots meets the requirement that a is more than or equal to D+0.2 mm, wherein D is the required butt welding seam width.
6. 6. The laser welding method for the butt joint of the hot forming steel based on the annular light spot, which is characterized in that the thickness of the hot forming steel is 0.5-2.0mm.
7. 7. The laser welding method of the hot forming steel butt joint based on the annular light spot according to claim 1, wherein the diameter of a welding spot formed by single pulse welding is 0.5 mm to 2.5 mm.
8. 8. The laser welding method for the hot forming steel butt joint based on the annular light spot, which is disclosed in claim 1, is characterized in that the optical fiber core diameter of the central laser is 0.1 mm, the optical fiber core diameter of the annular laser is 0.35 mm, the focal spot diameter of the central laser is 0.2-0.3 mm, and the focal spot diameter of the annular laser is 0.8-1.0 mm.
9. 9. The laser welding method of the hot-forming steel butt joint based on the annular light spot, which is disclosed in claim 1, is characterized in that when the thickness of the hot-forming steel is 1mm and the required weld width D is 1.0 mm, the total laser power is 2kW in the heating stage, wherein the central laser power is 0.2 kW and the annular laser power is 1.8 kW, the total laser power is 2kW in the welding stage, wherein the central laser power is 1.8 kW, the annular laser power is 0.2 kW, the defocus amount is 1mm, the superposition height a is not lower than 1.2 mm, and the superposition length b is not lower than 0.6 mm.

Description

Laser welding method for thermal forming steel butt joint based on annular light spot Technical Field The invention relates to the technical field of laser welding, in particular to a laser welding method for a hot forming steel butt joint based on annular light spots. Background Along with the rapid development of new energy automobile industry, light weight and safety become key targets of automobile body design, and the hot forming steel is widely applied to the automobile body structure, especially the key safety parts such as A column and B column, due to the high strength and excellent anti-collision performance, the use proportion of part of the hot forming steel in the high-end automobile type is up to more than 85%, and the hot forming structure is adopted to help realize the weight reduction of the automobile body, for example, a certain new energy automobile type realizes the weight reduction of the automobile body by about 20% through the application of the hot forming steel, so that the energy efficiency and the dynamic performance of the whole automobile are effectively improved. However, the existing hot formed steel has many technical challenges in the welding process, the welding joint is easy to generate welding core embrittlement due to the characteristics of high hardness and high temperature resistance, in the actual welding process, when the material hardness reaches 500 HV, the occurrence probability of welding core cracks is increased by 40% compared with that of common steel, and defects such as air holes, splashing, poor fusion and the like are easily generated in the welding process, so that the welding quality control difficulty is greatly improved, the production manufacturing cost is increased, in addition, in the traditional resistance spot welding process, the plate can be melted only by low current due to high material resistivity when the hot formed steel is welded, but in the combination of hot forming and hot forming, the diameter of a melting core can rapidly reach the requirement due to high contact resistance, but the problems of insufficient volume of the melting core, shallow melting depth and the like are easily caused, and the interface fracture is easily generated. In order to solve the defects of the traditional welding process, the laser welding technology is gradually applied to the field of hot forming steel welding. Compared with the traditional spot welding, the laser welding has the remarkable advantages that firstly, the welding can be completed in a short time due to the high energy density characteristic of the laser beam, the production efficiency is greatly improved, secondly, the welding precision can be controlled within 0.1mm, the surface of a welding seam is smooth and flat, the welding appearance quality is guaranteed, thirdly, a plurality of parts can be integrated and integrally formed, the number of the parts is reduced, meanwhile, the spot welding joint value among the parts is cancelled, the light weight of an automobile is further improved, in addition, the heat affected zone formed by the laser welding is smaller, the influence on the forming performance of the hot forming steel is weak, and the quality stability and the safety collision performance of the whole automobile can be improved. However, in practical application, it is found that when the thermoformed steel is welded by a single continuous laser, the heating and cooling speeds are too fast due to the high concentration of energy, so that it is still difficult to avoid the occurrence of welding defects such as air holes, splashing, poor fusion and the like, and the high-quality welding requirement of the butt joint of the thermoformed steel cannot be fully met. Therefore, it is necessary to invent a laser welding method for a butt joint of a hot forming steel based on an annular spot to solve the above-mentioned problems. Disclosure of Invention The invention aims to provide a laser welding method for a butt joint of hot forming steel based on annular light spots, which solves the problems that in the prior art, the conventional resistance spot welding and continuous laser welding processes of a hot forming plate are easy to generate welding defects such as air holes, splashing, poor fusion and the like, and easily cause embrittlement of welding nuclei, and the toughness and plasticity of the welding joint are reduced when severe, so that the control difficulty of welding quality and the production and manufacturing cost are greatly increased. In order to achieve the above purpose, the invention provides a laser welding method of a hot forming steel butt joint based on annular light spots, which comprises the following steps of adopting an annular light spot laser to weld the hot forming steel butt joint, adopting a pulse welding mode in the welding method, and forming each pulse welding spot comprises two stages: The first step is a heating stage, wherein an annular pulse light s