PURPOSE: To obtain titled high-tensile steel permitting additional intensification by making the temp. for stopping of the accelerated cooling after heating-rolling under adequate conditions for steel of composition having adequate content of Nb lower than that in the prior art. CONSTITUTION: A slab of 0.02W0.15 C, by %, 0.03W0.60 Si, 1.0W2.5 Mn, 0.005W 0.060 solAl, 0.01W0.10 Nb, ≥1 kinds of limited amts. of Ti, Ni, Cu, Mo, V, Cr, B, Ca, REM and ≤0.008 S and F out of the balance unavoidable impurities is heated to 1,180°C or below temp. at which Nb solutionizes at ≥0.01. Thereafter, it is rolled to ≥ 50% cumulative draft in an austenite recrystallization temp., in succession to which it is rolled to ≥50% cumulative draft at Ar 3 WAr 3 +150°C. Thereafter, it is cooled immediately down to 450W300°C at 2W20°C/sec. cooling rates, after which it is air-cooled. With the accelerated cooling temp. in excess of the upper limit, the two phase structure of ferrite and bainite is formed, and the effect of increasing strength is not large. Below the lower limit, the amt. of martensite increases and this decreases the effect of tempering. COPYRIGHT: (C)1982,JPO&Japio

Production of high-tensile steel of superior low- temperature toughness and weldability

PURPOSE:To obtain a hot-rolled steel material having high strength and excellent low-temp. toughness by rolling steel contg. specific contents of C, Si, Mn, SolAl under specific temp. conditions and reduction ratios and cooling the same slowly after force cooling. CONSTITUTION:The steel contg. 0.02-0.18wt% C, =40% reduction ratio at >=950 deg.C and >=10% reduction ratio per pass to fine the initial gamma grains. Thereafter, the steel is rolled at >=50% reduction ratio at <=950 deg.C and 90-700 deg.C final finish temp. Further the rolled steel is forcibly cooled down to 650-500 deg.C at 2-15 deg.C/sec cooling rate and is thereafter subjected to air cooling or slow cooling. Thus, the hot-rolled steel material having 75% volume ratio of granullar ferrite in microstructure and having high strength and excellent low-temp. toughness is obtained.

Production of hot-rolled steel material having high strength and excellent low temperature toughness

PURPOSE:To manufacture a high tensile steel with superior toughness at low temp. and superior weldability by heating and rolling a steel contg. adequate amounts of B and Ti under specified conditions and by carrying out accelerated cooling. CONSTITUTION:A steel slab contg. 0.02-0.12% C, 0.03-0.60% Si, 1.0-2.5% Mn, 0.005-0.01% sol.Al, 0.01-0.10% Nb, 0.0003-0.003% B, 0.005-0.08% Ti and =50% total draft. It is further rolled at Ar3-Ar3+ 150 deg.C and >=50% total draft and immediately quenched to =2 deg.C/sec cooling rate.

Manufacture of unnormalized high tensile boron steel with superior toughness at low temperature and superior weldability

Disclosed is a process for manufacturing a building construction steel having excellent high-temperature characteristics, which can be marketed at an economically reasonable price. According to this process, a slab having a steel composition in which appropriate amounts of Mo and Nb are added to a low-C and low-Mn steel is heated at a high temperature and rolling is finished at a relatively high temperature, or a slab having a steel composition in which an appropriate amount of Mo is added to a low-C and low-Mn steel composition is heated at a high temperature, rolling is finished at a relatively high temperature, and at the subsequent air-cooling step, water cooling is started at a temperature of a ferrite fraction of 20 to 50% during the transformation from austenite to ferrite, water cooling is carried out to an arbitrary temperature lower than 550° C., followed by air cooling.

Building construction steel having excellent fire resistance and low yield ratio

PURPOSE:To manufacture a high tension steel plate having superior strength and toughness in its weld heat-affected zone by subjecting a low carbon steel contg. a prescribed amount of Nb to heating, rolling and cooling under specified conditions. CONSTITUTION:The composition of a steel slab is composed of, by weight, 0.005-0.05% C, 0.05-0.75% Si, 0.2-2.2% Mn, 0.005-0.1% Al, 0.01-0.1% Nb and the balance Fe with inevitable impurities. The steel slab is heated to 1,000-1,250 deg.C and rolled. The rolling is finished at >=900 deg.C in the austenite recrystallization temp. range. The resulting steel plate is cooled at once at 1-50 deg.C/sec average cooling rate in the temp. range of 800 deg.C to 300 deg.C.

Manufacture of high tension steel plate having superior strength and toughness in its weld heat-affected zone

PURPOSE:To obtain a non-refined high tensile steel having strength and toughness almost equal to those of refined steel and improved weldability by reducing carbon equivalent of non-refined steel; off-setting a decrease in strength with the addition of B; and rolling the steel of a controlled compsn. at a temp. above Ar3 transformation point followed by proper slow cooling and air cooling.

Manufacture of nonnrefined high tensile steel

PURPOSE:To obtain a refined steel of a strength above 60kg/mm with minimized consumption of energy by suitably controlling rolling, heating and cooling conditions of a refined steel contg. a limited amt. of sol. Al and B, V and Mo. CONSTITUTION:A steel is refined contg. C; 0.03-0.15%, Si; 0.01-0.6%, Mn; 1.2-2%, Mo; 0.01-0.5%, V; 0.01-0.15%, sol. Al; 0.05-0.12% and >=10X T.N, and B; 0.0005-0.0025%. The steel is heated to 1000-1150 deg.C, hot rolled, cooled from a temp. above the Ar3 point to a cooling end point of 400-650 deg.C at a rate of 10-30 deg.C/ sec, and tempered at 550 deg.C-the Ac1 point. Thus, a mixed structure is obtd. contg. ferrite, bainite and a small amt. of martensite, and a tempered steel of a strength above 60kg/mm can be manufactured with energy consumption corresponding to about 40% of that of a conventional method.

Manufacture of refined steel with above 60 kg*mm2 strength

PURPOSE:To obtain a non-refined high tensile thick steel plate with excellent toughness, the thickness of which is specified, by using Nb and V; making C content low; increasing the amount of Ni added; and adding a slight amount of Ti.

Production of nonnrefined high tensile thick steel plate with excellent toughness

PURPOSE:To provide the title steel sheet, SR brittleness of which can be prevented without decreasing the strength and toughness of the base material by adding C, Si, Mn and Nb of each specified atm. range and one or more out of Cu, Ni and Mo of each specified atm. or below as required to Fe.

Sanbe Tetsuya

Papers

Manufacture of nonnrefined high tensile steel

Manufacture of refined steel with above 60 kg*mm2 strength

Production of nonnrefined high tensile thick steel plate with excellent toughness

60 kg class high tensile controlling rolled steel sheet with brittleness resistance in stress relief annealing