How to effectively prevent welding cracks and deformation of NM400 steel plate during welding process? We have taken the following measures from the production process.
(1) Selection of electrode: Selection of electrode with high crack resistance is conducive to reducing the tendency of NM400 steel plate weld cracking.
(2) Welding groove: When two unequal thickness NM400 steel plates are joined together, in order to make the weld seam transition smoothly, it is necessary to open a groove of 6×35°.
(3) preheating: Correct selection of preheating and postheating regimes is helpful to improve the microstructure and stress state of welded joints, reduce the hydrogen content in the weld and near-weld zone, and thus effectively improve the cold crack resistance of NM400 steel plate.
(4) Positioning welding: In order to ensure smooth butt joint and penetration, two pieces of NM400 steel plates are placed flat on the workbench to maintain a gap of 1mm, and the workpiece is pressed on the platform with welding fixture. After preheating, the butt joint is positioned immediately.
(5) Full welding: In order to slow down the cooling of the weld and heat-affected zone and reduce the tendency of cracking, short-pass welding should be adopted, that is, to weld a long weld piece by piece, so that each weld is repeatedly heated in a short time. When the NM400 steel plate is welded, the short track jump welding method is adopted, and the length of each weld is 150~200mm.
NM400 steel plate is Chinese grade wear resistant steel plate, the related steel grades are NM360, NM450, NM500, NM600.
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