中文摘要：

利用高压焊接试验舱在环境压力分别为0.1、0.5、0.9MPa的条件下,以Q235C钢板为母材进行V型坡口对接焊试验,通过调节焊接电流和电压、焊接速度及焊枪摆幅等焊接参数,获得了不同环境压力下成形良好的焊缝,并对焊缝进行力学性能检测和微观组织形貌观察.结果表明：随着环境压力增加,焊缝的抗拉强度增加,韧性明显下降,焊缝及其热影响区的微观组织因环境冷却作用的增强而出现了上贝氏体组织,但焊缝的综合性能仍能够满足水下焊接相关标准的要求.

英文摘要：

A hyperbaric welding test chamber was used to simulate the environmental pressures of 0. 1, 0.5, 0.9 MPa and the Q235C steel was taken as the base metal for V-groove butt welding tests. The welds with good appearance were obtained by adjusting the parameters of the welding current and voltage, the welding speed, and the torch swing under different pressures. Mechanical performance tests and microstructure analysis of the welds were conducted after welding. The experiment results show that the tensile strength of the weld seam increases and the toughness significantly decreases with the increase of environmental pressure. The upper bainite structure emerges in the seam and the heat-affected zone because of the enhanced environmental cooling effect. However, the weld comprehensive performance can still satisfy the underwater welding requirement.