高强钢采用低强组配接头尽管具有增加接头韧性、降低冷裂倾向、降低预热 温度甚至可以不预热焊接等优点，但高强钢的常规低组配焊接接头的承载能力低 于等匹配接头，尤其是焊趾区应力集中系数严重降低了接头的疲劳抗力。“等承 载能力”焊接结构设计思想(ELCC)就通过优化接头几何参数使低强度焊缝区具 有与母材相同的静承载能力和疲劳抗力。机械加工整形方法是目前获得等承载设 计所要求的余高及余高与母材过渡区形状参数的唯一手段。但是机加整形成本 高、效率低，不利于等承载设计方法的推广应用。为提高整形效率本文提出利用 焊缝金属塑性变形能力进行随焊整形的思想，并对随焊整形方法的可行性进行了 研究。 随焊整形是利用具有圆弧过渡轮廓特征的整形模具，对熔池后方变形抗力较 低的高温焊缝金属进行塑性加工，迫使焊趾区金属发生塑性延展变形进而使余高 与母材之间过渡平滑，达到减小应力集中的目的。 整形可行性试验材料采用 HQ620CF 高强钢和 J422 焊条。按等承载设计原则 确定了一定匹配比下焊缝的目标几何形状尺寸。提出了塑性整形区的概念，把温 度处于 450-700℃的焊缝金属所在区域叫做塑性整形区。本文用 TIG 电弧加热焊 缝表面获得整形所需温度，分析了加热电弧作用下塑性整形区的位置。 根据塑性整形区位置和焊缝目标形状的尺寸要求，研制了两套焊缝整形装 置，分别是气锤驱动的碾压轮整形装置和电锤驱动的冲击杆整形装置。从应力应 变的角度，说明碾压轮作用下的金属发生塑性变形的趋势。通过试验模拟相结合 的方法探索了焊缝整形工艺。整形试验发现碾压轮要与合适的焊缝形状相耦合才 能发挥效应，接触面为双弧形时焊缝成形效果较好。冲击杆整形对焊缝形状没有 严格的要求。 整形结果表明，经整形焊缝的焊趾过渡半径明显增大。焊接残余应力测量结 果显示，两种整形过程均对焊趾区引入了有益的压应力。力学性能测试结果表明 整形接头的焊趾区表层硬度和疲劳性能都有一定提高。静拉伸试验时，接头均断 于焊趾部位，焊趾最大应力高于母材屈服强度，说明接头的静载强度达到等承载 要求。 关键词，碾压轮整形；冲击杆整形；低匹配等承载接头哈尔滨工业大学工学硕士学位报告 -II- Abstract In the welding of high strength steel, the toughness of weld can be improved and the sensitivity of cold cracks decreased by using under-matched joints , the temperature of preheating and post-weld treatment is lower than that of equal-matched joints as well. But the load-carrying capacity of conventional under-matched joints is not enougth. For which the under-matched Equal Load Carrying Capacity (ELCC) method was put into forword to meet the requirement of loading-carrying properties. According to ELCC,geometric designs parameters such as width of weld , reinforcement and weld toe radius can reduce the stress concentration factor at weld toe and improve the fatigue property. The geometry appearance can be obtained by mechanical processing. However disadvantages of this process such as high cost and low efficiency is obvious. So a new method that can modify the geometry appearance with trailing was brought out in this paper. The modify method is based on the fact that the weld metal behind welding pool is prone to plasticly deform. The shape of hot metal of weld toe that under the hammering impact can be modified by some forming tool such as wheel or rod with round feature. The stress concentration factor of smooth weld toe can be reduced dramatically. The modifing equipments were put forward to realize this new forming process in this reserch named as impacting rolling wheel device and impacting rod device.The test materials in the feasibility test of weld with trailing shape modifying is undermatched ELCC HQ620CF steel joints welded with J422 electrode. The investigation of modify with trailing test indicates the initial shape of weld joint plays an important role on rolling wheel shaping process. This influence has also been simulated by using FEM software Deform. The effects of weld shape modifying process indicate that the weld toe radius after modifying is larger than initial value. Compressive residual stress comes into being at the joint toe area. The hardness at the weld toe surface of shape modified joint has been improved than that of initial state, as well as the fatigue property.The results of tensile test show that the modified joints have the same load carrying capcity with base metal. Keywords: rolling wheel shaping, impacting rod shaping, under-matched equal load- carrying capacity joints哈尔滨工业大学工学硕士学位报告 目录 摘要I ABSTRACT II 目录III 第 1 章 绪 论1 1.1 课题来源及研究的目的意义 1 1.2 焊缝形状参数对接头承载能力的影响 1 1.3 低匹配等承载接头设计准则 2 1.4 焊缝整形方法的研究现状 3 1.5 机械力加载在焊接领域的的应用 5 1.5.1 锤击法 5 1.5.2 碾压法 5 1.5.3 冲击旋转挤压法 6 1.6 本文的主要研究内容 6 第 2 章 焊缝随焊整形原理及实验材料8 2.1 焊缝随焊整形基本原理 8 2.2 试验材料 9 2.3 低匹配等承载接头形状的确定及焊接工艺 10 2.4 本章小结 12 第 3 章 焊缝随焊整形装置的研究14 3.1 焊缝整形温度区间 14 3.2 塑性整形区位置的确定 14 3.3 焊缝随焊整形施力方案的研究 16 3.3.1 碾压轮施力方案 17 3.3.2 冲击杆施力方案 17 3.4 焊缝随焊整形装置的设计 18 3.4.1 碾压轮整形装置的设计 18 3.4.2 碾压轮整形装置工作原理 21 3.5 冲击杆整形装置 22 3.6 本章小结 22 第 4 章 焊缝随焊整形数值模拟和实验研究24 -III-哈尔滨工业大学工学硕士学位报告 4.1 碾压轮整形有限元模拟 24 4.1.1 碾压轮整形应力应变分析 24 4.1.2 初始形状对整形效果的影响 27 4.2 碾压轮整形工艺过程 29 4.3 碾压轮整形效果分析 30 4.4 冲击杆整形试验 31 4.5 本章小结 32 第 5 章 随焊整形焊接接头性能分析34 5.1 焊趾区圆弧过渡半径对比 34 5.2 硬度实验与结果分析 36 5.3 焊缝附近焊接残余应力分析 36 5.4 焊接接头不同整形状态下承载性能分析 40 5.4.1 静拉伸试验 40 5.4.2 疲劳试验 41 5.5 本章小结 42 结论44