Abstract: The present invention relates to a high-tensile-strength low alloy carbon steel (in the form of a steel sheet, a steel pipe, a section steel or a wire rod), for a building structure, said high-tensile-strength steel being excellent in high temperature strength during a relatively short span of about one hour in the temperature from 600° C. to 800° C. and being used in the field of building construction, civil engineering, an offshore structure, shipbuilding, a reservoir tank or the like; and, more specifically, is a high-tensile-strength steel excellent in high temperature strength, characterized by containing, in mass, C at not less than 0.005% to less than 0.08%, Si at not more than 0.5%, Mn at 0.1 to 1.6%, P at not more than 0.02%, S at not more than 0.01%, Mo at 0.1 to 1.5%, Nb at 0.03 to 0.3%, Ti at not more than 0.025%, B at 0.0005 to 0.003%, Al at not more than 0.06%, and N at not more than 0.006%, with the balance consisting of Fe and unavoidable impurities and satisfying the expression p??0.0029×T+2.

Abstract: The present invention provides a high-strength steel for welded structures excellent in strength at a high temperature of a temperature range of 600° C. to 800° C. and a method of production of the same, in particular 490 MPa class high-strength steel for welded structures excellent in high temperature strength containing C: 0.005% to less than 0.040%, Si: 0.5% or less, Mn: 0.1 to less than 0.5%, P:0.02% or less, S: 0.01% or less, Mo: 0.3 to 1.5%, Nb: 0.03 to 0.15%, Al: 0.06% or less, and N: 0.006% or less and in accordance with need one or more of Cu, Ni, Cr, V, Ti, Ca, REM, and Mg, having a weld crack susceptible formulation PCM defined as PCM=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B of 0.15% or less, substantially not containing B, and a remainder Fe and unavoidable impurities, the microstructure being mainly composed of a mixed structure of ferrite and bainite, and the fraction of bainite being 20 to 90%.

Abstract: In order to quickly and economically evaluate cleanliness of a metal with high representativity when quantities, compositions, etc., of non-metallic inclusion particles existing in a metal and resulting in product defects are evaluated by a sample collected during the production process of the metal, the present invention provides an evaluation method involving the steps of levitation-melting a metal piece for a predetermined time by cold crucible levitation-melting means, discharging non-metallic inclusion particles contained in the metal piece to the surface of a molten metal, and directly analyzing a curved and non-smooth sample surface after solidification by a fluorescent X-ray analysis method using an energy dispersion type spectroscope, or by other chemical or physical measurements, to measure or analyze the quantities of elements constituting the non-metallic inclusion particles and to determine quantity of the non-metallic inclusions.

Abstract: In order to quickly and economically evaluate cleanliness of a metal with high representativity when quantities, compositions, etc., of non-metallic inclusion particles existing in a metal and resulting in product defects are evaluated by a sample collected during the production process of the metal, the present invention provides an evaluation method involving the steps of levitation-melting a metal piece for a predetermined time by cold crucible levitation-melting means, discharging non-metallic inclusion particles contained in the metal piece to the surface of a molten metal, and directly analyzing a curved and non-smooth sample surface after solidification by dissolving the surface and extracting and filtering the inclusions to measure or analyze the quantities of elements constituting the non-metallic inclusion particles and to determine quantity of the non-metallic inclusions.

Abstract: A steel having excellent HAZ toughness can be used for ships, buildings, pressure containers, linepipes, and so forth. The steel is of a Ti--Mg--O system steel containing at least 40 pcs/mm.sup.2 of oxide and composite oxide particles of Ti and Mg having a size of 0.001 to 5.0 .mu.m. A steel having excellent HAZ toughness can be produced, and the safety of structures using this steel can be remarkably improved.

Abstract: In order to quickly and economically evaluate cleanliness of a metal with high representativity when quantities, compositions, etc., of non-metallic inclusion particles existing in a metal and resulting in product defects are evaluated by a sample collected during the production process of the metal, the present invention provides an evaluation method involving the steps of levitation-melting a metal piece for a predetermined time by cold crucible levitation-melting means, discharging non-metallic inclusion particles contained in the metal piece to the surface of a molten metal, and directly analyzing a curved and non-smooth sample surface after solidification by a fluorescent X-ray analysis method using an energy dispersion type spectroscope, or by other chemical or physical measurements, to measure or analyze the quantities of elements constituting the non-metallic inclusion particles and to determine quantity of the non-metallic inclusions.

Abstract: A Ti--Al intermetallic compound has a compressibility of at least 25% at room temperature and a superior high temperature oxidation resistance and consists essentially of about 40 to 52 atomic percent of Ti, about 48 to 60 atomic percent of Al, and 10 to 1000 atomic ppm of at least one of P, As, Se, or Te.

Abstract: A Ti-Al intermetallic compound is prepared from a mixture of about 40 to 52 atomic % Ti, about 48 to 60 atomic % Al, and 10 to 3000 atomic ppm of at least one of P, As, Se, or Te. The mixture is melted and then solidified. The solidified product is annealed to form a uniform microstructure.