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新建输油气管道在投产过程中发现的各种焊接缺陷,需要在线动火进行焊口返修焊接。焊口返修处经过2次焊接和2次加热膨胀与收缩,易产生热裂纹和冷裂纹,或使返修焊缝内部留下较大的内应力,而诱发事故;因此对于钢级为L415、X60、X70、X80的管道,焊口返修前需进行焊前预热,当施焊环境温度低于0℃时,焊口返修后需采取保温缓冷措施。为了避免焊口割除重焊而增加工程成本和难度,应尽量提高首次返修合格率,为此给出了在线实施焊口返修的焊前准备、工艺规范、焊接参数和环境条件等要求。
The new pipeline found in the pipeline during the production of a variety of welding defects, the need for online welding fire welding rework welding. Weld rework after 2 welding and 2 heating expansion and contraction, easy to produce hot cracks and cold cracks, or rework the weld left within the larger internal stress, and induce accidents; so for the steel grade L415, X60 , X70, X80 pipe, weld before rework before welding to be preheated, when the welding environment temperature is below 0 ℃, after rework weld to take insulation slow cooling measures. In order to avoid the welding seam cutting and re-welding to increase the cost and difficulty of engineering, the qualification rate of repairing for the first time should be raised as much as possible. The requirements of welding preparation, process specification, welding parameters and environmental conditions are given online.