LSAW steel pipe is a welded steel pipe produced by pressing (rolling) a single medium and thick plate into a tube blank in a mold or a forming machine, using double-sided submerged arc welding and expanding its diameter.Pre-welding technology is a part of the welding process of LSAW steel pipe, which "shallow welding" the forming seam along the entire length, which is one of the special processes in the production of LSAW steel pipe.
The process of LSAW steel pipe pre-welding process
During pre-welding, the steel pipe blank is firstly seamed, followed by continuous gas shielded welding, and monitoring and feedback of the welding seam status and welding quality are carried out at the same time.
The specific process of a pre-welding cycle is: the inlet roller table accepts the tube blank → adjusts the opening position of the tube blank → conveys the tube blank → the tube blank is seamed → confirms the quality of the seam → the welding gun descends to prepare for welding and starts the laser tracker for tracking. →Open the shielding gas and cooling water valve →Start welding (the tube blank is fed at the welding speed) → stop the welding at the terminal arc extinguishing → lag off the shielding gas →the welding torch rises and returns → the tube blank is transferred to the next process.
Pre-soldering quality
Pre-weld quality includes seam quality and weld quality.
(1) There is no wrong edge or the wrong edge is smaller than the specified value. Generally, the amount of wrong edge is ≤ 8% of the plate thickness, and the maximum does not exceed 1.5mm.
(2) It is necessary to ensure that the welding seam has a suitable penetration depth and deposition amount. It is necessary to ensure that there is no cracking after welding, and no burn-through phenomenon occurs, and the height of the welding seam should be controlled, so that the excess height of the external welding seam will not be affected.
(3) The weld bead is continuous and well formed, so as to ensure the final external welding quality.
(4) There are no defects such as welding deviation, porosity, crack slag inclusion, burn-through and back welding flash in the weld, and the center deviation of the weld is required to be ≤1mm.
(5) There is no arc burn, little splash, and does not affect the bevel and surface quality of the pipe end.
(6) The physical and chemical properties of the weld and the base metal match the weld metal to meet the quality requirements.
Welding Specifications.
Usually determined by experiment. For welding wires of different specifications, when the welding line energy is within a certain range, the welding seam has a good appearance and good physical and chemical properties. Taking Φ4 0mm welding wire as an example, when the line energy is 35~40kJ/cm, the appearance and physical and chemical properties of the weld are in an ideal state.
The process of LSAW steel pipe pre-welding process
During pre-welding, the steel pipe blank is firstly seamed, followed by continuous gas shielded welding, and monitoring and feedback of the welding seam status and welding quality are carried out at the same time.
The specific process of a pre-welding cycle is: the inlet roller table accepts the tube blank → adjusts the opening position of the tube blank → conveys the tube blank → the tube blank is seamed → confirms the quality of the seam → the welding gun descends to prepare for welding and starts the laser tracker for tracking. →Open the shielding gas and cooling water valve →Start welding (the tube blank is fed at the welding speed) → stop the welding at the terminal arc extinguishing → lag off the shielding gas →the welding torch rises and returns → the tube blank is transferred to the next process.
Pre-soldering quality
Pre-weld quality includes seam quality and weld quality.
(1) There is no wrong edge or the wrong edge is smaller than the specified value. Generally, the amount of wrong edge is ≤ 8% of the plate thickness, and the maximum does not exceed 1.5mm.
(2) It is necessary to ensure that the welding seam has a suitable penetration depth and deposition amount. It is necessary to ensure that there is no cracking after welding, and no burn-through phenomenon occurs, and the height of the welding seam should be controlled, so that the excess height of the external welding seam will not be affected.
(3) The weld bead is continuous and well formed, so as to ensure the final external welding quality.
(4) There are no defects such as welding deviation, porosity, crack slag inclusion, burn-through and back welding flash in the weld, and the center deviation of the weld is required to be ≤1mm.
(5) There is no arc burn, little splash, and does not affect the bevel and surface quality of the pipe end.
(6) The physical and chemical properties of the weld and the base metal match the weld metal to meet the quality requirements.
Welding Specifications.
Usually determined by experiment. For welding wires of different specifications, when the welding line energy is within a certain range, the welding seam has a good appearance and good physical and chemical properties. Taking Φ4 0mm welding wire as an example, when the line energy is 35~40kJ/cm, the appearance and physical and chemical properties of the weld are in an ideal state.
