激光电弧复合焊接风电安装船桩腿的组织及力学性能研究

论文总字数：23820字

摘 要

目前风电能源开发已经成为一种趋势，风电安装船桩腿良好的性能是保证风电装备开发新能源的重要保障。激光电弧复合焊接作为一种新型、高效的焊接方法，相比传统的焊接方法具有能量密度高、运行成本低、电弧稳定性高、工装准备要求低等特点，逐渐应用于航空航天、船舶制造、海洋工程等领域。在此研究背景下，本文以15 mm厚NVE690钢板为焊接对象，采用激光-MIG电弧复合焊接工艺，研究了焊接工艺参数对焊缝宏观形态、微观组织、物相及力学性能的影响规律。

实验结果表明，激光功率、焊接电流、电弧电压、离焦量、焊接速度等工艺参数以及多道焊焊接对焊接试样的宏观形貌产生重要的影响。单道复合焊接可以焊透13 mm厚的钢板，而双道复合焊接可以焊透15 mm厚的钢板。焊缝在形成过程中发生了相变，其微观组织为板条状马氏体与残余奥氏体，且晶粒尺寸大；过热区的微观组织为粗大的马氏体和残余奥氏体；细晶区的则为细小的马氏体及少量的残余奥氏体；不完全重结晶区为马氏体、贝氏体及铁素体的混合组织。由于热循环的作用，焊缝区及热影响区显微硬度大于母材区的硬度。拉伸断裂发生位置均发生在母材区域，可见焊缝区及热影响区域的力学性能优于母材区域的力学性能。双道焊焊接比单道焊焊接获得更深的熔深，且由于后一道焊的热影响作用，焊接接头组织得到细化，其显微硬度有一定程度上的降低。拉伸实验结果表明，实验中所有试样焊缝区的拉伸强度及屈服强度均优于母材区域。基体中存在的缺陷限制了焊接件的整体拉伸及屈服强度。本文的研究结果可以为风电安装船的激光电弧复合焊接提供理论借鉴及技术指标。

关键字：激光电弧复合焊接;NVE690钢;微观组织;力学性能

ABSTRACT

At present, the development of wind power has become a trend. The performance of wind power installation vessel is an important guarantee for the development of new energy sources. Laser arc hybrid welding is a new and efficient welding method. Compared to the traditional welding method, it has some characteristics, such as high energy density, low operation cost, high arc stability, and low tooling requirements for the preparation .And it is applied gradually in aerospace, shipbuilding, marine engineering and other fields. Under this background, this paper research the welding process parameters influent on weld macro morphology, microstructure, phase and mechanical properties with 15mm thick NVE690 steels by Nd:YAG laser-MIG arc hybrid welding.

The experimental results show that the welding process parameters, such as laser power、welding current、arc voltage、welding speed， have an important influence on the macro morphology of the welding samples. Single channel composite welding can be welded through 13 mm thick steel plate, while the dual channel composite welding can be welded through 15 mm thick steel plate. Phase transformation occurred in the formation of the weld and the microstructure of weld are lath martensite and residual austenite and the grain size is large; The microstructure of overheated zone are coarse martensite and residual austenite; The microstructure of fine grain zone is fine martensite and a small amount of residual austenite; yet the incomplete recrystallization zone’s are martensite, bainite and iron element of hybrid organization. The microhardness of the weld zone and the heat affected zone are greater than that of the base metal due to the effect of the thermal cycle. The location of tensile fracture occurs in the base metal, and the mechanical properties of the weld zone and the heat affected zone are better than that of the base metal. The welding process of double pass welding is deeper than that of single pass welding, and the microstructure of the welded joint is refined due to the heat influence of the latter, and the micro hardness is reduced to a certain extent. The tensile test results show that the tensile strength and yield strength of the weld zone are better than that of the base metal. The existence of defects in the matrix limits the overall tensile and yield strength of the welded joints. The research results of this paper can provide theoretical reference and technical indicators for the laser arc hybrid welding of wind power installation vessel.

Keywords: laser arc hybrid welding; NVE690 steel; microstructure; mechanical properties.

目录

摘要 Ⅲ

ABSTRACT Ⅳ

第一章. 绪论 1

1.1. 前言 1

1.2. 激光电弧复合焊接技术 2

1.3. 焊接参数对激光电弧复合焊的影响 3

1.4. 国内外研究现状及发展 5

1.5. 本课题研究内容 5

第二章. 实验材料、方法及设备 7

2.1. 实验材料 7

2.2. 实验方法及设备 7

2.2.1. 激光电弧复合焊接实验 8

2.2.2. 试样微观组织分析 8

2.2.3. 焊缝接头的力学性能测试 9

第三章. 激光电弧复合焊接接头组织分析 11

3.1. 焊接接头宏观形貌分析 11

3.2. 焊接接头微观组织分析 14

3.2.1. 单道焊焊接接头微观组织分析 14

3.2.2. 双道焊焊接接头微观组织分析 16

3.2.3. 单道焊与双道焊下焊缝的X射线衍射分析 20

3.3. 本章小结 21

第四章. 激光电弧复合焊焊接接头的力学性能分析 21

4.1. 焊接接头的硬度分布 22

4.2. 焊接接头的拉伸性能 25

4.3. 小结 30

第五章. 总结与展望 31

5.1. 工作总结 31

5.2. 关键创新点 31

5.3. 展望 31

致谢 32

参考文献 33

附录一 35

第一章 绪论

1.1 前言

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