Effect of Super-Large Defocus on Microstructure and Mechanical Properties of TRIP800 High-Strength Steel Laser Welded Joint

TIAN Jiazhuang; TAO Wu; YANG Shanglu

doi:10.7512/j.issn.1001-2303.2023.07.06

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Effect of Super-Large Defocus on Microstructure and Mechanical Properties of TRIP800 High-Strength Steel Laser Welded Joint
Vol. 53, Issue 7, Pages: 40-45(2023)
DOI： 10.7512/j.issn.1001-2303.2023.07.06

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田佳壮，陶武，杨上陆.超大离焦量对TRIP800高强钢激光焊接接头微观组织与力学性能的影响［J］.电焊机，2023，53（7）：40-45.

TIAN Jiazhuang, TAO Wu, YANG Shanglu.Effect of Super-Large Defocus on Microstructure and Mechanical Properties of TRIP800 High-Strength Steel Laser Welded Joint[J].Electric Welding Machine, 2023, 53(7): 40-45.
田佳壮，陶武，杨上陆.超大离焦量对TRIP800高强钢激光焊接接头微观组织与力学性能的影响［J］.电焊机，2023，53（7）：40-45. DOI： 10.7512/j.issn.1001-2303.2023.07.06.

TIAN Jiazhuang, TAO Wu, YANG Shanglu.Effect of Super-Large Defocus on Microstructure and Mechanical Properties of TRIP800 High-Strength Steel Laser Welded Joint[J].Electric Welding Machine, 2023, 53(7): 40-45. DOI： 10.7512/j.issn.1001-2303.2023.07.06.

摘要

传统激光焊接车用先进高强钢时，经常容易发生焊接接头热影响区软化、焊缝脆化以及塌陷等影响焊接接头成形性能和力学性能的问题。针对此问题，使用超大离焦量激光焊接工艺，对1.6 mm厚度的TRIP800高强钢进行激光焊接，获得一种大尺寸的新型焊接接头，并对新型焊接接头的微观组织、硬度和力学性能进行分析。结果表明，当采用激光功率3 500 W、焊接速度3 m/min、离焦量为50 mm时，能够获得形貌良好、无明显缺陷的激光焊接接头。接头热影响区的组织以残余奥氏体和马氏体组织为主，焊缝区域以马氏体组织为主。焊接接头硬度的分布曲线由焊缝区至母材区呈现逐步降低的趋势，超大离焦焊接接头的抗拉强度与母材的强度相当，断后延伸率约为无离焦接头的1.25倍，断口呈现大量的韧窝，以韧性断裂为主。对于TRIP800高强钢的新型焊接接头力学性能的提升，主要是由于较宽的焊缝区域组织，增强了抵抗裂纹的能力，分散了激光焊接时的能量集中，使焊接接头不易产生较大的内应力，成形性能较好。

Abstract

Problems affecting the forming properties and mechanical properties of welded joints such as softening of the heat-affected zone of welded joints, embrittlement and collapse of welded joints are often prone to occur When advanced high-strength steel is used for traditional laser welding vehicles. To solve this problem, The super larger-defocus laser welding process was used to laser 1.6 mm thick TRIP800 high-strength steel to obtain a new type of welded joint with a wide weld size, and the microstructure, hardness and mechanical properties of the welded joint were analyzed. The results showed that when the laser power is 3 500 W, the welding speed is 3m/min, and the defocusing distance is 50 mm, a new laser welding joint with good morphology and no obvious defects can be obtained. The microstructure of the heat-affected zone of the welded joint was mainly composed of residual austenitic and martensitic structure, while the weld area was mainly composed of martensitic structure. The distribution curve of the hardness of the welded joint showed a gradual decrease trend from the weld area to the base metal area, the tensile strength of the super larger-defocus welded joint was comparable to the strength of the base metal, the elongation after breaking is about 1.25 times that of the traditional welded joint, and the fracture presents a large number of tenacity sockets, mainly ductile fracture. The improvement of the mechanical properties of the new welded joints of TRIP800 high-strength steel is mainly due to the wide weld area organization, which enhances the ability to resist cracks, disperses the energy concentration during laser welding, and was not easy to produce large internal stress in the welded joints, and the row performance was better.

关键词

TRIP800高强钢激光焊超大离焦微观组织力学性能

Keywords

TRIP800 high strength steellaser weldingsuper larger-defocusmicrostructuremechanical properties

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