【作者】 杨浩；

【导师】 王元勋；

【作者基本信息】 华中科技大学 ， 工程力学， 2013， 硕士

【摘要】 双相钢因具备高强度、高韧性以及耐腐蚀、可焊性好等优点，已经广泛应用于汽车车身制造中，对双相钢电阻点焊的研究是保证车身安全，实现汽车轻量化的重要依据。本文以DP600热镀锌双相钢为研究对象，通过焊接动态电阻的测试，研究了主要焊接参数与点焊质量的关系，通过热电有限元数值模拟，分析电阻点焊温度场及熔核形成过程，将实验研究与数值模拟研究结论对比分析，为电阻点焊在线监控提供参考依据。通过搭建焊接参数数据采集系统，采集焊接电流和电极间电压等关键焊接参数，然后通过数学处理得到焊接动态电阻参数。结合动态电阻曲线，对动态电阻变化规律进行了研究，分析总结了焊接电流、电极压力对动态电阻的影响规律，同时对虚焊与发生喷溅时的动态电阻变化规律进行了探讨，这为利用动态电阻监测双相钢电阻点焊质量提供了依据。通过建立二维轴对称点焊接头的热电有限元模型，充分考虑边界条件、材料热电参数、固液相变潜热、接触电阻、焊接电流加载等问题，对电阻点焊进行热电数值模拟，得到熔核生长过程温度场。在一定范围内，焊接电流越大，得到的熔核尺寸也越大。熔核的形成过程经历了塑性粘连、快速增长、缓慢增长三个阶段。熔核的径向增长呈波动性且其增长速度明显大于轴向增长速度。通过对比分析不同焊接工艺参数下的熔核实验值与数值模拟值可知，在不引起焊件飞溅和过烧的情况下，无论是熔核直径变化规律还是具体尺寸均较好的吻合，验证热电模拟分析的准确性。更多还原

【Abstract】 The dual phase steel has high strength, high toughness, and good corrosion as well as good weldability. It has been widely used in automotive body manufacturing. It is very important to study the resistance spot welding of dual phase steel for the safety of the automotive body and lightweight of automobile. In this paper, the resistance spot welding of Dual Phase Steel600is researched, the relationship between the welding parameters and spot welding quality is detailedly studied through dynamic resistance testing, and the temperature field in resistance spot welding and nugget formation process is attentively analyzed through the thermoelectric finite element numerical simulation. Comparative analysis of the experimental study and numerical simulation study conclusions provide the basis for online monitoring of resistance spot welding.Collecting the critical welding parameters of the welding current and the inter-electrode voltage through constructing welding parameter data acquisition system, combined with the dynamic resistance curve, dynamic resistance variation law is studied, and the influence of welding current and electrode pressure on the dynamic resistance is analyzed and summarized, at the same time, dynamic resistance variation law when weld splashing and cold joint happens is also discussed. This provides a basis for the use of dynamic resistance to monitoring the quality of resistance spot welding of dual phase steel.The nugget growth process and temperature field results are obtained from resistance spot welding thermoelectric numerical simulation which is based on two-dimensional axisymmetric model fully considered boundary conditions, thermoelectric parameters of material, latent heat of phase transition, the effect of contact resistance and the loading of welding current. Within a certain range, the welding current and the nugget size are positive correlation. Nugget formation process undergone three stages, they are plastic adhesion stage, rapid growth stage and slow growth stage. The radial growth of the nugget has volatility and its growth rate is significantly greater than the axial growth rate.It can be concluded from the comparative analysis of the experimental value and numerical simulation value of the nugget under different welding parameters that the nugget diameter variation and specific dimensions coincided well when weldment splash and over firing didn’t occur. This verified the accuracy of the thermoelectric simulation analysis.更多还原