Laser butt welding experiments assisted with high speed imaging were conducted to isochronously observe the keyhole and weld pool in this study. The time-averaged characteristics of the keyhole and weld pool geometries were extracted by image processing. The characteristics contained the upper width, bottom width and upper length of the weld pool, and the diameter and inclining angle of the keyhole. The effect of welding speed on the characteristics was investigated and the results showed the increased welding speed gave rise to a decrease in the keyhole diameter and the weld pool widths, while the weld pool upper length firstly decreased from 5.795 mm to 4.308 mm until the speed was 4.2 m/min, and then increased to 4.941 mm when the speed was 6.9 m/min. Based on the measured time-averaged characteristics, a double cylindrical heat source model considering the keyhole angle and diameter was derived to predict the weld size. Thermal analysis based on the heat source model was performed and the prediction results were validated using the time-averaged characteristics and the single weld cross section sizes respectively. The results showed the model had good simulation accuracy (7.20%–12.48%) for sub-millimeter weld cross section and had good adaptability of multi-process parameters. The max difference in the errors of the two validations was 3.92%, indicating the thermal analysis validating with the time-averaged results had higher accuracy.

在这项研究中，进行了激光对焊实验，并在高速成像的辅助下对小孔和熔池进行了等时观察。通过图像处理提取小孔和熔池几何形状的时间平均特征。特征包括熔池上部宽度、底部宽度和上部长度，以及小孔的直径和倾角。研究了焊接速度对特性的影响，结果表明焊接速度的增加导致小孔直径和熔池宽度的减小，而熔池上部长度首先从 5.795 mm 减小到 4.308 mm，直到速度达到为 4.2 m/min，然后在速度为 6.9 m/min 时增加到 4.941 mm。基于测得的时间平均特性，推导出考虑小孔角度和直径的双圆柱热源模型来预测焊缝尺寸。进行了基于热源模型的热分析，并分别使用时均特性和单焊缝横截面尺寸验证了预测结果。结果表明，该模型对亚毫米焊缝截面具有良好的模拟精度（7.20%～12.48%），对多工艺参数具有良好的适应性。两次验证的误差最大差异为3.92%，表明用时间平均结果验证的热分析具有更高的准确度。进行了基于热源模型的热分析，并分别使用时均特性和单焊缝横截面尺寸验证了预测结果。结果表明，该模型对亚毫米焊缝截面具有良好的模拟精度（7.20%～12.48%），对多工艺参数具有良好的适应性。两次验证的误差最大差异为3.92%，表明用时间平均结果验证的热分析具有更高的准确度。进行了基于热源模型的热分析，并分别使用时均特性和单焊缝横截面尺寸验证了预测结果。结果表明，该模型对亚毫米焊缝截面具有良好的模拟精度（7.20%～12.48%），对多工艺参数具有良好的适应性。两次验证的误差最大差异为3.92%，表明用时间平均结果验证的热分析具有更高的准确度。