When welding steel pipe is firstly liquidation clean welded joints of oil, paint, water, rust, and then based on wall thickness open groove, thick open and thin open smaller (angle grinder), then the gap is the right productcommon, which is the welding rod or wire diameter 1 - 1.5 times, if you groove, be careful not to open a speech appropriately to stay small. Tack welding at least three points, four points incomparable good work.
After midnight should be half and half welded steel pipe welding, the starting point for the best beyond the lowest point one centimeter or so, so good joints from the opposite. If wall thickness of the pipe should be stratified at least two layers, the first layer of the whole ring of solder until they have finished welding the second layer.