用Gleeble－1500热模拟机对Cu－Nb－B系超低碳贝氏体钢进行不同焊接工艺下热模拟试验，选定峰值温度为1340℃，高温停留0．5s，t(8/5)，分别取30，45，60s．研究了焊接热影响区（HAZ）组织、性能和硼的分布．结果表明：此类钢在不同焊接条件下，焊接热影响区均具有较好的低温韧性和较低的韧脆转变温度．进一步探讨了不同t(8/5)；对钢中贝氏体组织组成及形态的影响，以及组织和低温韧性的关系．用径这显微照相技术（PTA）显示了硼在热影响区的行为． The thermal simulation experiments of Cu-Nb-B ultra-low carbon bainitic steels were carried out with Gleeble-1500 thermal simulator. The peak temperature was 1340 ℃, 0.5s, t (8/5) , Respectively, take 30,45,60 s. The microstructure, properties and boron distribution of HAZ were studied. The results show that the welded HAZ has better low temperature toughness and lower ductile-brittle transition temperature under different welding conditions. The effect of different t (8/5) on the microstructure and morphology of bainite in steel was also discussed. The relationship between the structure and the low temperature toughness was also discussed. This photomicrograph (PTA) shows the behavior of boron in the HAZ.