【作者】 蒋意靖；

【导师】 唐新华；

【作者基本信息】 上海交通大学 ， 材料加工工程， 2008， 硕士

【摘要】 激光填丝焊具有速度快、效率高、焊缝质量好的特点,已成功用于宝钢集团股份有限公司普通碳钢带钢连轧生产线前后板带的连接,但在冷轧硅钢带时,发现在激光焊缝处经常发生断裂,严重影响生产效率。为弄清其原因,从根本上解决断带问题,本文就MW9124硅钢的激光焊缝冷轧过程中的断裂问题进行一系列的研究。本文首先对断带进行了失效分析。通过对断带试样的各种物理和化学性能的分析,对失效的各种可能进行了排查,发现断带主要是由低周疲劳引发,而焊缝表面缺陷造成的局部的应力应变集中对疲劳裂纹萌生有相当大的影响。本文利用ANSYS有限元软件,对焊缝的成形、内部缺陷、表面缺陷、强度匹配不当等因素引起的应力集中进行了模拟,分析了它们对应力应变集中的影响程度。其中焊缝的表面缺陷如错边,对应力应变集中的影响很大,而内部缺陷影响相对较小,因此表面缺陷在焊接中尤其需要关注。此外,本文还利用该软件,对裂纹疲劳扩展的过程进行了模拟研究。本文的最后部分,通过对MW9124硅钢的激光焊接工艺试验,对影响焊缝成形、焊缝组织和性能变化的工艺参数进行了研究和优化,找出了线能量对于焊缝组织和硬度的影响规律,总结了MW9124硅钢的激光焊接特点,为提高焊缝质量和断裂韧性,降低其冷轧过程中的断裂倾向提供有效的参考依据。更多还原

【Abstract】 The Laser Filler Wire Welding is characterised with high speed, high efficiency and good welding quality, it has been successfully applied to joining the general carbon steel sheet on the tandem rolling production lines at Bao Steel Group Co. Ltd. But on the cold-rolling production line of silicon steel, the fracture occurs in the laser welding seam from time to time, which greatly lowers the production effieciency. In order to fint out the fracture cause and the effective solution to this problem exactly, a series of researches that focused on the fracture problem in the cold-rolling process of the laser welded silicon steel MW9124 were carried out in this thesis.Firstly a series of failure analysis of the broken steel sheet parts were performed. By means of various kinds of chemical and physical analysis of these parts, as well as the study of some possible failure causes, it was found that the low-cycle fatigue is the main possible reason, and the local stress and strain concentration in a small area induced by surface defects of welding seams have also a great effect on the initiation of the fatigue crack. For this sake a finite element simulation software ANSYS is used to simulate and analyse the stress concentration caused by welding deformation, inner and surface welding defects and intensity mismatch. The surface welding defects such as unfitness of butt joint have much larger influence on stress and strain concerntration than the inner welding defects. Therefore more attentions should be paid on such surface defects. Besides, ANSYS was used to simulate the propagation process of fatigue crack. In the last part of this thesis, the technology parameters, which influence the forming, structure and performance of the welding seam, was studied and optimized through the laser welding experiment of MW9124 silicon steel, and the relationship between structure, hardness grandient and line input energy was obtained. The laser welding characteristics of MW9124 silicon steel was also concluded as a reference to raise the welding quality and fracture toughness property, and to lower the cracking probability in the cold rolling process.更多还原