激光—电弧复合焊高强钢的微观组织与拉伸性能关系研究

发布时间：2018-02-14 22:03

本文关键词： 激光-电弧复合焊接高强钢显微组织拉伸强度　出处：《长春理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：激光-电弧复合焊作为激光焊接技术中的新兴技术,在国内外具有较强的竞争力和广阔的应用市场,但是国内对激光-电弧复合焊接技术的研究较晚,相对一些发达国家,我国在这方面的研究相对落后。因此,本论文采用激光-电弧复合热源焊接方法,对焊后的高强钢进行微观组织及力学性能的基础分析。(1)首先,在实验室条件下对低合金调质高强钢进行激光-电弧复合焊焊接,经过打磨抛光等处理后将其制成标准试样;其次,详细介绍了试验过程中涉及的设备以及测量仪器的机械结构以及主要功能等;最后,研究了维氏硬度分布规律、微观组织形貌以及拉伸性能这三个方面,并且对不同方面给出了不同的研究方法。(2)首先,分析了试样的显微维氏硬度,通过研究发现:靠近焊缝区中心硬度值有降低的趋势,在焊缝区和过热区之间硬度基本维持在较稳定的水平,从正常晶粒区开始降低,并在软化区达到最低。母材的硬度在400HV左右,除了个别点之外,焊缝和热影响区的硬度基本处于500HV到600HV之间,软化区的宽度大小在0.6~0.7mm内,其硬度最低。其次,分析了试样的微观组织形貌。通过金相显微镜和扫描电子显微镜观察复合焊接接头的显微组织形貌,发现:在热影响区组织中没有发现新成型的铁素体组织,并且,从靠近基体位置到靠近融合线的位置,全是板条状的马氏体组织。再次,通过对试样进行X射线衍射分析,发现:无论是焊缝区、热影响区还是基体组织都是马氏体组织。最后,通过对焊缝区进行EDS分析,发现:焊缝区的主要元素Mn、Cr、Ni的含量基本没有变化,这也就说明,焊缝区的组成成分比较一致,硬度基本不变。(3)对试样进行拉伸试验。研究发现,在拉伸过程中,试样断裂均发生在焊缝区,同时,拉伸断口形貌与拉伸强度有关:强度为573MPa时,断口缺陷为结晶裂纹;强度为806MPa时,断口缺陷为结晶裂纹和气孔缺陷;强度为941MPa时,断口形式为韧窝断裂和气孔缺陷;强度为1073MPa时,断口形式是典型的韧窝断裂。
[Abstract]:As a new technology in laser welding technology, laser-arc composite welding has strong competitiveness and wide application market at home and abroad. However, the study of laser-arc composite welding technology in China is relatively late, compared with some developed countries. Therefore, in this paper, the laser arc composite heat source welding method is used to analyze the microstructure and mechanical properties of high strength steel after welding. The low alloy quenched and tempered high strength steel was welded by laser-arc composite welding under laboratory conditions. After polishing and polishing, it was made into a standard sample. Secondly, The mechanical structure and main functions of the equipment and measuring instruments are introduced in detail. Finally, the distribution of Vickers hardness, the microstructure and the tensile properties of Vickers hardness are studied. At first, the microhardness of the sample is analyzed. It is found that the hardness value near the center of the weld zone has a tendency to decrease. The hardness between the weld zone and the superheated zone is maintained at a stable level, which decreases from the normal grain area and reaches the lowest in the softening zone. The hardness of the base metal is about 400 HV, except for a few points, the hardness of the base metal is about 400HV, and the hardness of the base metal is about 400HV. The hardness of weld and heat affected zone is between 500HV and 600HV, and the width of softening zone is 0.6 ~ 0.7mm, and the hardness is the lowest. The microstructure of composite welded joints was observed by metallographic microscope and scanning electron microscope. It was found that no newly formed ferrite structure was found in the heat-affected zone. From the position near the matrix to the position near the fusion line, all the martensite structures are strip. Thirdly, by X-ray diffraction analysis of the sample, it is found that: no matter in the weld zone, The heat affected zone and matrix structure are both martensite microstructures. Finally, through the EDS analysis of the weld zone, it is found that the content of the main element of the weld zone is basically unchanged, which means that the composition of the weld zone is consistent. It was found that the fracture occurred in the weld zone during the tensile process, and the tensile fracture morphology was related to the tensile strength: when the tensile strength was 573 MPA, the fracture defect was crystalline crack; When the strength is 806 MPA, the fracture surface is crystalline crack and porosity defect, the fracture form is dimple fracture and pore defect when the strength is 941 MPA, and the fracture form is typical dimple fracture when the strength is 1073 MPA.
【学位授予单位】：长春理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG456.7

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