STEEL PLATE FOR HULL EXCELLENT IN IMPACT ENERGY ABSORBING POWER AND ITS PRODUCTION

• Main Authors: KOSEKI TOSHIHIKO, MINAGAWA MASANORI, ISHIKAWA TADASHI, ISHIDA KOJI, IMAI SHIRO, JINUSHI SHUICHI
• Format: Patent
• Language: English
• Published: 14.09.1999
• Edition: 6
• Subjects: ALLOYS; CHEMISTRY; CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION ORPROCESSING OF GOODS; FERROUS OR NON-FERROUS ALLOYS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINSTCLIMATE CHANGE; TREATMENT OF ALLOYS OR NON-FERROUS METALS

PROBLEM TO BE SOLVED: To effectively improve the impact energy absorbing power of a steel plate by subjecting a slab whose chemical components and a carbon equivalent are specified to hot rolling, controlling the cooling rates after finish rolling to two stages and allowing residual γ to exist on the surface and back layers. SOLUTION: A steel having a compsn. contg., by weight, 0.05 to 0.2% C, 0.05 to 2.0% Si, 0.1 to 2.0%, Mn, 0.001 to 0.1% Al and the balance, and in which the carbon equivalent Ceq=(C+Mn/6+(Cu+Ni)/15+(V+Mo+Cr)/5+5B)% is regulated to 0.42 is cast. This slab is subjected to hot rolling finish rolling is completed within the temp. range of the Ar3 +100 deg.C to the Ar3 -50 deg.C, and it is cooled to the Ar1 +100 deg.C to the Ar1 deg.C at a cooling rate of 2 deg.C/sec. Moreover it is cooled at a cooling rate of >=10 deg.C/sec, an the cooling is stopped at 250 to 450 deg.C. In this way, the steel plate having >=8 mm plate thickness, and in which residual γ of 1.0 to 20% by area ratio is contained in the surface and back layers of at least >=1/8 of the plate thickness can be obtd.