Stiffened plate and method of manufacturing the same

Abstract

A stiffened plate is formed by welding a plurality of stiffener materials which, together with a steel plate, form closed cross-sectional structures onto a surface of the steel plate. The stiffener materials are joined to the steel plate as a result of edge portions of the stiffener materials which are in contact with the steel plate by being laser welded at a predetermined welding speed as a result of a laser having a predetermined output being irradiated from a predetermined direction thereon from the external side of the closed cross-sectional structures. Accordingly, it is possible to achieve an improvement in the weld quality when welding stiffener materials onto a steel plate, and to achieve an improvement in fatigue strength.

1 . A stiffened plate which is formed by welding a plurality of stiffener materials which, together with a steel plate, form closed cross-sectional structures onto a surface of the steel plate, wherein
 the stiffener materials are joined to the steel plate as a result of edge portions of the stiffener materials which are in contact with the steel plate by being laser welded at a predetermined welding speed as a result of a laser having a predetermined output being irradiated from a predetermined direction thereon from the external side of the closed cross-sectional structures.   
   
   
       2 . The stiffened plate according to  claim 1 , wherein the edge portions of the stiffener materials are formed so as to face the surface of the steel plate substantially parallel therewith, and are laser welded to the steel plate. 
   
   
       3 . The stiffened plate according to  claim 1 , wherein the stiffener materials are closed cross section ribs which have a substantially U-shaped cross section orthogonally to the longitudinal direction. 
   
   
       4 . The stiffened plate according to  claim 1 , wherein,
 instead of laser welding, the stiffener materials are welded to the steel plate by means of hybrid laser-arc welding in which laser welding and arc welding are performed in combination.   
   
   
       5 . A method of manufacturing a stiffened plate which is formed by welding a plurality of stiffener materials which, together with a steel plate, form closed cross-sectional structures onto a surface of the steel plate, wherein
 the steel plate and the stiffener materials are joined together as a result of edge portions of the stiffener materials which are in contact with the steel plate by being laser welded at a predetermined welding speed as a result of a laser having a predetermined output being irradiated from a predetermined direction thereon from the external side of the closed cross-sectional structures.   
   
   
       6 . The method of manufacturing a steel plate according to  claim 5 , wherein, prior to the laser welding, the edge portions of the stiffener materials are formed so as to face the surface of the steel plate substantially parallel therewith. 
   
   
       7 . The method of manufacturing a steel plate according to  claim 5 , wherein, in the laser welding, a refractive laser welding apparatus which refracts laser light which has been converged by a convex lens onto a planar mirror is used to irradiate laser light over the surface of the steel plate so as to join the stiffener materials to the steel plate. 
   
   
       8 . The method of manufacturing a steel plate according to  claim 5 , wherein, in the laser welding, a refractive laser welding apparatus which converges and refracts laser light by using a parabolic mirror or spherical mirror is used to irradiate laser light over the surface of the steel plate so as to join the stiffener materials to the steel plate. 
   
   
       9 . The method of manufacturing a steel plate according to  claim 5 , wherein the welding is achieved by hybrid laser-arc welding in which arc welding is performed in a process either simultaneously with or consecutively to the laser welding. 
   
   
       10 . The method of manufacturing a steel plate according to  claim 5 , wherein, in the laser welding or in the hybrid laser-arc welding, filler wire is used. 
   
   
       11 . The method of manufacturing a steel plate according to  claim 5 , wherein, in the laser welding or in the hybrid laser-arc welding, a bevel shape in which there is no gap with the skin plate is used. 
   
   
       12 . The method of manufacturing a steel plate according to  claim 5 , wherein, in the laser welding or in the hybrid laser-arc welding, the skin plate is used in a structure having a curved surface.