The “JFE EWEL” technology for improving the toughness of heat affected zone (HAZ) effected by high heat input welding has been applied to make SA440 high tensile strength steel plates for architectural constructions. The developed “JFE EWEL” technology consists of minimizing the coarse grain HAZ region through controlling TiN particles, refining the microstructure of HAZ by using BN and Ca inclusions as nucleation sites of intra-granular ferrites and decreasing carbon equivalent (C_eq) of steel. Furthermore, welding consumables have been newly developed to control the microstructure of HAZ through diffusive B atoms from weld metal to base material. The developed 100mm thick SA440 grade steel plate exhibits excellent HAZ toughness in welded joints produced by SAW and ESW with high heat inputs. Consequently, JFE Steel has various kinds of high tensile strength steel plate and welding consumable for architectural construction with excellent toughness in welded joint.