Welding technique of annular pipe joints. Welding ring joints of pipelines has some specific features. Usually performed by welding seams on pipes with diameter ranging from tens of millimeters to 1440 mm with wall thickness of 16 mm or more. When the thickness of pipe wall of low-carbon and low alloy steels up to 8-12 mm welding can be performed in a single layer. However, multi-joints have improved mechanical properties determined by the positive influence of weld thermal cycle subsequent to the previous weld metal, so the welding of pipes, mostly performed in two layers or more. The recommended number of layers depends on the thickness of the seam of the wall.
Pipe joints can be welded to the swivel, when the tube can be rotated, or nonslewing position. Weld joints of the first type is usually carried out in the down position without too much difficulty, although difficult to boil the root of the weld, since its formation is most often on the weight. Butt welding requires skilled welders, as the whole seam is performed at different spatial positions. Can be welded in two ways: each semi-circle from the top down or bottom up. The first way is possible with electrodes 4 mm in diameter, giving a little slag (with an organic coating), with a short arc leaning on the end of the electrode is formed on the edge of the visor without the transverse vibrations of the electrode, or with a few of its variations. When welding a bottom-up process is carried out at a much slower rate with the transverse vibrations of an electrode with a diameter of 3-5 mm.
See also:
Manual Arc Welding
Introduction to Arc Welding
Creating and maintaining an arc
Ways to improve performance
Technique of upper and horizontal joints
Technique of the lower seam
Pipe Welding Technique
The Method
Arc Welding in Protective Gases
Electrodes for Manual Arc Welding
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