搅拌摩擦焊过程中搅拌头温度场分布特征

Characteristic of temperature distributions in stirring tools during friction stir welding

试验测定了搅拌头温度分布曲线,分析了搅拌头温度场的分布特征,对比研究了不同材质搅拌头温度分布的特点.结果表明,摩擦焊初始阶段,搅拌区域金属的软化致使摩擦针与试板之间的摩擦产热量降低,在搅拌头轴肩与试板接触之前,搅拌头温度出现滞涨,并出现一定程度的回落;稳定焊接阶段,摩擦热传递至搅拌头的热量与通过其散失的热量处于动平衡状态,其温度波动较小;高速旋转搅拌头的表面与周围空气进行强烈的热交换,搅拌头轴线上的温度高于外缘的温度;采用比热容小、热导率高材质制作的搅拌头,焊接过程中其温度变化快,整体温度高.

The temperature distribution in stirring tools was measured by experimental method. It is shown that the characteristic of temperature distribution in stirring tools is much different from that in workpieces. At the beginning stage of friction stir welding,the softening in stirring zone reduces the friction coefficient and the friction heat between the stirring pin and the workpiece,so the temperature in stirring tools stops rising,whereas decreases in the exterior margin of the tool before the shoulder touches the workpiece. At the steady welding stage,equilibrium exists between the heat quantity delivered to and dissipated through the stirring tool,and its temperature keeps little fluctuation. The surface of the high-speed rotating tool has intensive heat exchange with the air around it,so the temperature near its axis is higher than that on the exterior margin. The stirring tools made of metal with lower specific heat capacity and higher coefficient of heat transfer lead to heat within the welding area dissipating faster.