搅拌针形貌和温度场对厚板铝合金FSW焊缝金属流动的影响

发布时间：2018-06-10 03:53

  本文选题：搅拌针 + 辅助热源　； 参考：《南昌航空大学》2015年硕士论文

【摘要】：本文采用6种不同形貌的搅拌针和添加辅助热源的方式对20mm厚的2024-T4铝合金板材进行搅拌摩擦焊试验。通过改变搅拌针形貌研究其对焊接时接头温度的影响,并测量了焊核区的形状尺寸,分析了不同搅拌针形貌对焊缝塑性金属流动行为的影响;利用有限元分析软件ANSYS对不同初始温度下的焊缝温度场进行模拟,探讨了温度场的变化规律以及其对焊缝金属流动的影响。为优化搅拌针的设计和厚板铝合金的焊接提供理论参考。研究结果表明:搅拌摩擦焊焊接20mm厚2024铝合金时,合适的焊接工艺参数范围较小。焊接热输入对厚板铝合金材料的成形有较大影响,在旋转速度为375r/min、焊接速度为37.5mm/min时,可获得无缺陷的焊接接头。搅拌针形貌对塑性金属流动有很大影响。在搅拌针锥度为25°至15°范围内,减小搅拌针基体锥度对焊缝金属充分流动有促进作用。当锥度减小至15°时,搅拌针表面螺纹对塑性金属的驱动力减小;但搅拌针端部直径增大、摩擦面积增加、产热增加,致使接头底部高温区变宽、焊缝中塑化的金属量以及搅拌针所携带的金属量增多,从而焊核区塑性金属挤压作用增加。宏观表现为焊核高度、宽度和面积都增大。多头螺纹搅拌针会增强焊缝塑性金属的流动。相比单头和双头螺纹,3头螺纹搅拌针的金属流动通道更多,焊缝塑性金属在轴向方向上的抽吸挤压作用增强,搅拌针端部脱离的高温金属量增多;但焊核周围母材金属的温度未随螺纹头数的增减而变化,即焊核金属周围母材的抗变形能力相同。因此随金属量的增加,焊核区金属向焊缝表层扩张趋势增强,焊缝中的孔洞及疏松等焊接缺陷减少。采用合适的辅热温度对2024-T4铝合金进行焊接,可改善焊缝的孔洞缺陷,获得无缺陷的焊接接头。当辅助热源温度为40℃时,2024-T4铝合金焊缝整体温度升高,高温区变宽,金属软化程度提升,塑化金属量增多,搅拌针向焊缝底部抽吸的金属量增加,使焊核区金属横向挤压力增强,阻力减弱;焊缝中“抽吸挤压”作用增强,塑性金属会更趋向于在横向方向流动,向上流动动能减小。宏观表现为焊核区的面积、宽度和高度增加。
[Abstract]:In this paper, friction stir welding experiments of 2024-T4 aluminum alloy plate with 20mm thickness were carried out by using six kinds of stirring needles with different morphologies and adding auxiliary heat source. The effect of stirring needle morphology on weld temperature was studied, and the shape and size of nugget zone were measured, and the effect of different stirring needle morphology on the flow behavior of plastic metal was analyzed. The finite element analysis software ANSYS is used to simulate the weld temperature field at different initial temperatures. The variation of the temperature field and its influence on the flow of weld metal are discussed. It provides a theoretical reference for optimizing the design of mixing needle and welding of thick plate aluminum alloy. The results show that the suitable range of welding parameters is small when 20mm thickness 2024 aluminum alloy is welded by friction stir welding. The welding heat input has great influence on the forming of thick plate aluminum alloy material. When the rotation speed is 375 r / min and the welding speed is 37.5mm/min, the non-defect welded joint can be obtained. The shape of agitated needle has great influence on the flow of plastic metal. In the range of taper between 25 掳and 15 掳, reducing the taper of stirring needle matrix can promote the full flow of weld metal. When the taper is reduced to 15 掳, the driving force of the surface thread on the plastic metal decreases, but the diameter of the end of the stirring needle increases, the friction area increases and the heat production increases, which results in the widening of the high temperature area at the bottom of the joint. The amount of plasticized metal in the weld and the metal carried by the stirring needle increased, thus the plastic metal extrusion in the nuke zone increased. Macroscopically, the nugget height, width and area are increased. The multi-threaded stirring needle enhances the flow of the plastic metal in the weld. There are more metal flow channels in the mixing needle with single or double screw thread, the suction and extrusion effect of the plastic metal in the axial direction is enhanced, and the amount of high temperature metal detached from the end of the stirring needle is increased. However, the temperature of the base metal around the nugget does not change with the increase or decrease of the number of thread heads, that is, the deformation resistance of the base metal around the nugget metal is the same. Therefore, with the increase of the amount of metal, the tendency of metal expansion into the surface of weld increases, and the defects such as porosity and porosity in the weld decrease. When 2024-T4 aluminum alloy is welded with appropriate auxiliary heating temperature, the hole defects of the weld can be improved and the welded joints without defects can be obtained. When the auxiliary heat source temperature is 40 鈩，

本文编号：2001883