460MPa-Yielcl-Strength-Class Steel Plate with JFE EWEL~(R) Technology for Large-Heat-Input Welding

摘要

The "JFE EWEL~(R)" technology for improving the toughness of heat affected zone (HAZ) effected by large heat input welding has been applied to make YP460 MPa class steel plates for very large container carriers. The "JFE EWEL" technology consists of minimizing the coarse grain HAZ region through controlling TiN particles, refining the microstructure of HAZ by using B, Ca and improving the toughness of matrix. Furthermore, the reduction of C, Si, Nb contents improves HAZ toughness with decreasing martensite-austenite constituents. Production of this steel plate was made possible by Super-OLAC~(R) (OLAC: On-Line Accelerated Cooling) and state-of-the-art thermo-mechanical control process. The developed steel has been approved by Nippon Kaiji Kyokai as rolled steel for hull, and is under the application to actual ship.