Abstract: A process for producing high-tension bainitic steel having high-toughness and excellent weldability by subjecting a bainitic steel of a specific composition to a low-temperature heating and subsequently rolling the steel under specific conditions.

Abstract: In the method of heat-treatment of welded pipe having a reinforcement weld bead therealong by heating the pipe by using an induction heating device and then by cooling it, the bead which has just been heated by the induction heating device, is further heated by a bead heater to a temperature such that the temperature difference between the metal of the pipe and the bead is smaller than a temperature difference which will produce a bad influence on the quality of the pipe.

Abstract: A method for producing a steel sheet having excellent low-temperature toughness, comprising a step of heating to a temperature not higher than 1150.degree. C., a steel slab containing 0.01 - 0.13% C, 0.05 - 0.8% Si, 0.8 - 1.8% Mn, 0.01 - 0.08% total Al, 0.08 - 0.40% Mo and not more than 0.015% S with the balance being iron and unavoidable impurities, and a step of hot rolling the steel slab thus obtained by at least three passes with a minimum reduction percentage not less than 2% by each rolling pass in a temperature range of 900 - 1050.degree. C, a total reduction percentage not less than 50%, and with a finishing temperature not higher than 820.degree. C.

Abstract: A method for heating steel pipe for induction heating coils, while the pipe is travelling through said coils in the axial direction, which comprises:(a) calculating the limit absorption electric power density Po (W/cm.sup.2) by the followng formula:Po = 1/40 x T x .sqroot.dwhere T = heating temperature (.degree. C) and d = wall thickness (mm);(b) attaching a power supply of low frequency to the induction heating coils;(c) setting said power supply for maximum capacity to be impressed to said induction heating coils, and(d) heating the steel pipe as it is travelling through said induction heating coils heated by said power supply, at such speed as to permit the steel pipe to be heated to the desired temperature, and heating the steel pipe with the set power if the absorption electric power density P by the set power is P .gtoreq. Po, and heating the steel pipe by shortening the effective length of the induction heating coils to obtain P .gtoreq. Po if P .ltoreq.

Abstract: The production process characterized in that a steel ingot or slab containing not less than 0.004% of TiN not larger than 0.02.mu. is heated to a temperature not higher than 1150.degree. C and rolled, and growth of the .gamma. grains during this heating and rolling step is prevented by TiN to improve the toughness, and the resultant steel product has an excellent low-temperature toughness with a yield point of 40 kg/mm.sup.2 or higher, and is useful as hot rolled or as heated at a temperature ranging from 300.degree. to 750.degree. C after the hot rolling.

Abstract: A method for obtaining a weld metal having excellent toughness at low temperatures as below -40.degree. C, which method comprises heating the weld metal having a specific steel composition to its austenitizing temperature and cooling it or holding it at the temperature for not longer than 25 minutes and then quenching and tempering it. In order to further improve the low temperature toughness, the weld metal is reheated again to the Ac.sub.1 to Ac.sub.3 range. Excellent low temperature toughness of the weld metal can be obtained without the necessity of using any special welding materials.

Abstract: A method for producing a large diameter steel pipe having excellent shape, toughness and tensile strength by subjecting the pipe to descaling and to heat treatment which involves heating the steel pipe locally successively from one end to the other end of the steel pipe in the axial direction and forcedly cooling the pipe, and then expanding the steel pipe after the heat treatment.

Abstract: A method for producing a high tensile strength steel plate which comprises subjecting to a low temperature rolling, a steel composition containing not more than 0.25% of carbon, not more than 0.5% of silicon, 0.5 to 2.0% of manganese, not more than 0.015% of sulfur, 0.005 to 0.1% of aluminum, one or more of niobium, vanadium and titanium in an amount not less than 0.01%, and REM in an amount not less than 1.3 times the amount of sulfur, with optionally one or more of nickel, chromium and copper, with the balance being iron and unavoidable impurities, which steel possesses a low notch toughness transition temperature and high absorbed energy in the notch-impact test, and is suitable in the as rolled condition for use as pipe lines in cold districts.

Abstract: A method for producing a high tensile strength and toughness bend pipe in which a heat treatment is done as a pretreatment prior to bending, and a tempering treatment is done, if necessary, after the bending, and the bend pipe produced by the present invention is useful for pipe line construction and shows excellent properties at low temperatures.

Abstract: The production process characterized in that a steel ingot or slab containing not less than 0.004% of TiN not larger than 0.02.mu. is heated to a temperature not higher than 1150.degree. C. and rolled, and growth of the .gamma. grains during this heating and rolling step is prevented by TiN to improve the toughness, and the resultant steel product has an excellent low-temperature toughness with a yield point of 40 kg/mm.sup.2 or higher, and is useful as hot rolled or as heated at a temperature ranging from 300.degree. to 750.degree. C. after the hot rolling.