PRODUCTION OF STEEL MATERIAL OF SUPERIOR CRACKING RESISTANCE

• Main Authors: NANUN MICHIHIKO, KUBOTA TAKESHI
• Format: Patent
• Language: English
• Published: 02.08.1982
• Subjects: CHEMISTRY; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS

PURPOSE:To eliminate the segregation of the elements formed during casting and to obtain a steel material of superior cracking resistance by subjecting an ingot or slab of steel to primary hot working in a specific temp. region then holding the same at above specific temp. CONSTITUTION:An ingot or slab is subjected to primary hot working of >=20% reduction of area in an asutenite temp. region of 1,200 deg.C or below, after which it is held for >=30min at above 1,000 deg.C central temp. of the ingot or slab continuously or by reheating, whereby the segregation elements are diffused and the cause for weld HAZ cracking is eliminated. At the primary hot working temp. above 1,200 deg.C, the diffusion effect is deprived of by the restoration and recrystallization of the steel, and if it is too low, the deformation resistance increases. However, it is equally well to work the ingot or slab in an austenite-ferrite two phase coexistence temp. region. The holding time at 1,000 deg.C or above is 30min or longer and up to 5hr depending upon required characteristics of steel materials. After the temp. treatment, secondary hot working can be accomplished in succession.