TUBE MANUFACTURING METHOD BY LASER BEAM WELDING METHOD AND DEVICE THEREFOR

摘要

PURPOSE:To provide a laser beam welded tube excellent in the inner surface of a tube and the quality of a welded part. CONSTITUTION:When a metallic plate is formed by forming rolls continuously into a tubular shape and the butted part is welded by laser beam to manufacture a tube, a damage preventing member 7 supported by a mandrel 14 having a water feeding structure is arranged in the welded tube. This damage preventing member 7 has a shield gas injecting hole 13 at the part of the through hole 8 for a welded part penetrating energy beam and is so constituted that the inner part cooling water is poured into the inner surface of the tube. In the manufacture of the tube, a prescribed width of water flow 17 is formed by this damage preventing member 7 on the inner surface of the tube opposite to the welded part and the shield gas is injected just below the welded part to perform laser beam welding. In this way, spatters are cooled by the water flow running in the inner surface of the tube facing the welded part and at the same time, exhausted out to the outer part of the tube. The thermal damage of the inner surface of the tube by the welded part penetrating energy beam is prevented. The welded part is prevented by shield gas from steam etc.