Method of manufacturing weldable, tough and high strength steel for structure members usable in the ashot-state and steel so made

Claim 1

A METHOD OF MANUFACTURING WELDABLE, TOUGH AND HIGH STRENGTH STEEL FOR STRUCTURE MEMBERS USABLE IN THE AS-HOT-WORKED STATE, SAID STEEL CONSISTING OF CARBON 0.080.30% SILICON 0.02-0.60%M MANGANESE 0.5-2.5%, NITROGEN LESS THAN 0.345%, AT LEAST 0.010% OF WHICH IS TO BE BOUND TO ALUMINUM IN THE FORM OF PRECIPITATED ALUMINUM NITRIDE OF 0.03-0.12%, THE REST TO ANY ONE SELECTED FROM THE GROUP COMPOSED OF: COLUMBIUM LESS THAN 0.20%, TITANIUM LESS THAN 0.12% AND ZIRCONIUM LESS THAN 0.20%, AND A COMBINATION THEREOF; FREE UNCOMBINED NITROGEN LESS THAN 0.004%, FREE METALLIC ALUMINUM DISSOVED IN THE MATRIX AS SOLID SOLUTION LESS THAN 0.15%, AS WELL AS AT LEAST ONE COMPLEMENTING ALLOYING ELEMENT SELECTED FROM THE GROUP CONSISTING OF: NICKEL 0.10-1.0%, CHROMIUM 0.10-1.0%, MOLYBDENUM 0.05-1.0%, COPPER 0.05-1.0%, VANADIUM 0.005-0.30%, BORON 0.0005-0.01%; THE BALANCE SUBSTANTIALLY ALL IRON WITH INCIDENTAL AND UNAVOIDABLE IMPURITES, THE METHOD CONSISTING OF HEATING THE STEEL TO A SOAKING TEMPERATURE IN THE RANGE OF 1100*- 1200*C., HOT-WORKSING THE STEEL IN THE TEMPERATURE RANGE OF 1200*700*C., STARTING THE HOTWORKING AT A TEMPERATURE NOT ABOVE 1200*C. AND FINISHING AT A TEMPERATURE NOT BELOW 700*C., GIVING THE STEEL A REDUCTION IN THICKNESS, CALCULATED ON THE FINAL THICKNESS OF THE PRODUCT, OF AT LEAST 20% IN AT LEAST ONE PASS IN THE TEMPERATURE RANGE BELOW 1000*C., AND THEREAFTER COOLING THE STEEL.

Claim 2

A METHOD OF MANUFACTURING WELDABLE, TOUGH AND HIGH STRENGTH STEEL FOR STRUCTURE MEMBERS USABLE IN THE AS-HOT-WORKED STATE, SAID STEEL CONSISTING OF CARBON 0.080.30% SILICON 0.02-0.60%M MANGANESE 0.5-2.5%, NITROGEN LESS THAN 0.345%, AT LEAST 0.010% OF WHICH IS TO BE BOUND TO ALUMINUM IN THE FORM OF PRECIPITATED ALUMINUM NITRIDE OF 0.03-0.12%, THE REST TO ANY ONE SELECTED FROM THE GROUP COMPOSED OF: COLUMBIUM LESS THAN 0.20%, TITANIUM LESS THAN 0.12% AND ZIRCONIUM LESS THAN 0.20%, AND A COMBINATION THEREOF; FREE UNCOMBINED NITROGEN LESS THAN 0.004%, FREE METALLIC ALUMINUM DISSOVED IN THE MATRIX AS SOLID SOLUTION LESS THAN 0.15%, AS WELL AS AT LEAST ONE COMPLEMENTING ALLOYING ELEMENT SELECTED FROM THE GROUP CONSISTING OF: NICKEL 0.10-1.0%, CHROMIUM 0.10-1.0%, MOLYBDENUM 0.05-1.0%, COPPER 0.05-1.0%, VANADIUM 0.005-0.30%, BORON 0.0005-0.01%; THE BALANCE SUBSTANTIALLY ALL IRON WITH INCIDENTAL AND UNAVOIDABLE IMPURITES, THE METHOD CONSISTING OF HEATING THE STEEL TO A SOAKING TEMPERATURE IN THE RANGE OF 1100*- 1200*C., HOT-WORKSING THE STEEL IN THE TEMPERATURE RANGE OF 1200*700*C., STARTING THE HOTWORKING AT A TEMPERATURE NOT ABOVE 1200*C. AND FINISHING AT A TEMPERATURE NOT BELOW 700*C., GIVING THE STEEL A REDUCTION IN THICKNESS, CALCULATED ON THE FINAL THICKNESS OF THE PRODUCT, OF AT LEAST 20% IN AT LEAST ONE PASS IN THE TEMPERATURE RANGE BELOW 1000*C., AND THEREAFTER COOLING THE STEEL.