Long distance pipeline construction welding problem

　　At present, the domestic long-distance pipeline construction usually "under the cellulose type electrode to weld, cellulose type electrode root welding + self shielded flux cored wire semi-automatic welding and STT root pass + self shielded flux cored wire semi-automatic welding" process, welding easy question that arises is:

　　1, Slag

　　Reason: Because they use a long-distance pipeline under flux cored wire semi-automatic welding process to be filled, cover up, when a semi-automatic welding process equipment intermittent fault, often top wire phenomenon, then wear a wire into the bath, when melt instant re-ignited after rapid cooling pool, the weld was often wrapped with metal debris, or slag, produced slag.

　　Measures: Before root weld groove should carefully cleaning, filling, be careful when you clean up the slag cover pass.

　　2, Stomatal

　　Cause: The filling layer porosity is mainly due to self-protection cored semiautomatic welding arc voltage caused by excessive.

　　Action: In the welding process, to select the appropriate arc voltage and wire feed speed, to maintain a certain length of wire out, next to the vertical welding to control the proper welding speed.

　　3, Roots of incomplete penetration

　　Cause: The main group of the gap is too small or too thick blunt edge.

　　Measures: Before welding serious and group weld grinding, to ensure wire or rod can be smoothly inserted into the groove when the root weld root; root weld can not occur when the hole when dissolved, grinding out the root gap applications and appropriately adjust the welding parameters .

　　4, Crack

　　The reason: to force the group to crack when often lead solder.

　　Measures: 1) to avoid forcible Group; 2) preheat, a modest increase in root weld bead thickness, immediately after the completion of the root weld heat welding, filling, capping.

　　5, Burn

　　Reason: Because the root bead is too thin or improper welding parameters.

　　Measures: not too thin root bead to 3mm thick appropriate; root welding process parameters is not too much; to stop welding immediately after burn, to be grinding out bevel angle and root gap, and then re-root welding, heat welding To complete this procedure.