钛合金搅拌摩擦焊工艺研究及温度场分析

【作者】 赵强；

【导师】 王玉；

【作者基本信息】 西北工业大学 ， 机械制造及其自动化， 2007， 硕士

【摘要】 搅拌摩擦焊(Friction stir welding简称FSW)是一种新型的固态焊接工艺，被誉为“继激光焊后最为革命性的连接技术”。与传统焊接方法相比，它不但能够得到性能优良的焊接接头，而且能够焊接一些传统方法很难完成的材料的焊接，比如高强铝、低碳钢和钛合金等。由于FSW具有许多优点，人们进行大量搅拌摩擦焊试验，以期在工程上尽快使用这种先进的连接方法。 本文选择应用前景较好的TC4钛合金作为研究对象。在焊接过程中，通过改变焊接的工艺参数，如搅拌头的轴向压力、旋转速度、焊接速度等，以得到良好的焊接接头，然后对接头进行分析。分析得出：钛合金的搅拌摩擦焊接接头分为搅拌区、热机械影响区、热影响区和母材区，其中热影响区仅受热影响的作用，β相增大；热机械影响区在热影响和塑性变形双重作用下发生动态再结晶，出现了大量的等轴α相晶粒；搅拌区的温度达到β相变温度以上，在搅拌头的搅拌下，这个区域发生剧烈变形，组织为原始β相及转变β相。 然后对搅拌摩擦焊温度场进行有限元分析，使研究具有一定的理论支持，而且焊接过程中工件的温度分布也是研究搅拌摩擦焊接的重要方面。本次研究使用了ANSYS软件，并将瞬态温度场转化为很小时间步内的准稳态分析，运用了ANSYS的APDL参数化编程功能。在温度场的模拟过程中，采用移动坐标系的方法来代替搅拌头移动的过程，忽略焊接过程中金属塑性变形产生的热量，其热源包括搅拌头的轴肩和工件的摩擦生热以及搅拌针和周围材料作用生成的热。将模拟结果与试验结果分析、对比和验证，说明模型和试验结果相符。更多还原

【Abstract】 Friction stir welding (FSW) is a relatively new solid state joining process. It is said to be "the most revolutionary joining method after laser welding". Compared with the conventional welding processes, friction stir welds not only get batter joint, but can be used in various kinds of materials, which very hard to complete in conventional welding processes, such as high-strength aluminum, mild steel and titanium alloy etc. In order to hold the advanced joining process, people make a lot of FSW experiments on various situations.In the study, we select TC4 as the object, which will be applied widely. During the processing, we can get good joint by change normal force, rotate speed and welding speed, then, analyze the samples to get knowledge about FSW. The result shows that the weld region of defect-free weld of TC4 displayed four microstructure distinct regions: stir zone, thermo-mechanically affected zone, heat affected zone, base material. For heat affecting, the β grain in HAZ growth; there are a lot of exceeded a grain in the TMAZ, for the dynamic recrystallization resulted by heat and plastic yield; the temperature of SZ exceeded the β-transus temperature, its microstructure is prior β and transformed β, which was resulted by intense deformation caused by probe’s stir.In order to know the FSW process profundity, we made a temperature finite element analysis, after experiment. Simulation can provide academic base and reference for study. Temperature distribution is an important content of FSW research, In the study, simulation was carried out by finite element software ANSYS, whose APDL parameterized program function was used. Transient tem analysis was transferred to steady-state analysis, which occurred in short time. In the simulation, the tool’s move was replaced by moving coordinate system. The heat source includes frictional heat between the tool and workpiece and interacting of probe and workpiece, and the heat caused by metal’s plastic yield was ignore. To analyze, contrast and validate the result of simulation and experiment, it shows that model is accordant with real process.更多还原