Abstract: An object to be achieved by the present invention is to provide a gas barrier film having excellent acid resistance, transparency, and gas barrier properties. The gas barrier laminated body of the present invention is a laminate, in which an inorganic thin-film layer is laminated onto at least one of surfaces of a polymer substrate, and the inorganic thin-film layer mainly contains Al and Si, and a ratio of an Al content amount between before and after treatment of immersing the laminate into aqueous solution of hydrochloric acid that has concentration of 1 mol/L for one hour satisfies a formula of (Al Content Amount After Treatment)/(Al Content Amount Before Treatment)×100?75.

Abstract: To provide an oil-well steel pipe having excellent SSC resistance. The oil-well steel pipe according to the present invention contains, by mass percent, C: 0.15 to 0.35%, Si: 0.1 to 0.75%, Mn: 0.1 to 1.0%, Cr: 0.1 to 1.7%, Mo: 0.1 to 1.2%, Ti: 0.01 to 0.05%, Nb: 0.010 to 0.030%, Al: 0.01 to 0.1%, P: at most 0.03%, S: at most 0.01%, N: at most 0.007%, and O: at most 0.01%, the balance being Fe and impurities. The Ti content and the Nb content in a residue obtained by bromine-methanol extraction satisfy equation (1): 100×[Nb]/([Ti]+[Nb])?27.5??(1) where the Ti content (mass %) and the Nb content (mass %) in the residue are substituted for [Ti] and [Nb].

Abstract: The present invention provides a steel which simultaneously satisfies a plurality of characteristics, specifically, a steel for tubes with excellent sulfide stress cracking resistance, including, C: 0.2 to 0.7%; Si: 0.01 to 0.8%; Mn: 0.1 to 1.5%; S: not more than 0.005%; P: not more than 0.03%; Al: 0.0005 to 0.1%; Ti: 0.005 to 0.05%; Ca: 0.0004 to 0.005%; N: not more than 0.007%; Cr: 0.1 to 1.5%; and Mo: 0.2 to 1.0%; the balance being Fe, Mg and impurities, being characterized in that: the content of Mg is not less than 1.0 ppm and not more than 5.0 ppm; and inclusions of not less than 50% of the total number of those in steel have such a morphology that Mg—Al—O-based oxides exist at the central part of the inclusion, Ca—Al-based oxides enclose the Mg—Al—O-based oxides, and Ti-containing-carbonitrides further exist on a periphery of the Ca—Al-based oxides.

Abstract: The present invention provides a steel which simultaneously satisfies a plurality of characteristics, specifically, a steel for tubes with excellent sulfide stress cracking resistance, including, C: 0.2 to 0.7%; Si: 0.01 to 0.8%; Mn: 0.1 to 1.5%; S: not more than 0.005%; P: not more than 0.03%; Al: 0.0005 to 0.1%; Ti: 0.005 to 0.05%; Ca: 0.0004 to 0.005%; N: not more than 0.007%; Cr: 0. 1 to 1.5%; and Mo: 0.2 to 1.0%; the balance being Fe, Mg and impurities, being characterized in that: the content of Mg is not less than 1.0 ppm and not more than 5.0 ppm; and inclusions of not less than 50% of the total number of those in steel have such a morphology that Mg—Al—O-based oxides exist at the central part of the inclusion, Ca—Al-based oxides enclose the Mg—Al—O-based oxides, and Ti-containing-carbonitrides further exist on a periphery of the Ca—Al-based oxides.

Abstract: A method of producing steel for a steel pipe excellent in sour-resistance performance comprises controlling the amount of Ca addition charged into a molten steel in a ladle according to a N content in the molten steel prior to Ca addition. Non-metallic inclusions in the steel are mainly composed of Ca, Al, 0 and S, and a CaO content in the inclusions is in the range of 30 to 80%, the ratio of the N content in the steel to the CaO content in the inclusions satisfying equation (1), and a CaS content in the inclusions satisfies equation (2), 0.28?[N]/(% CaO)?2.0??(1) (% CaS)?25%??(2) where [N] represents the mass content (ppm) of N in the steel, (% CaO) represents the mass content (%) of CaO in the inclusions, and (% CaS) represents the mass content (%) of CaS in the inclusions.

Abstract: The steel for steel pipes of the present invention is the one for steel pipes excellent in sour-resistance performance including C, Mn, Si, P, S, Ti, Al, Ca, N and O, and optionally including a predetermined amount of one or more of Cr, Ni, Cu, Mo, V, B and Nb, in which inclusions in the steel have Ca, Al, O and S as main components, the CaO content in the inclusions is 30 to 80%, the ratio of the N content in the steel (ppm) to the CaO content in the inclusions (%) is from 0.28 to 2.0, and the CaS content in the inclusions is 25% or less. In addition, the method of producing steel for steel pipes of the present invention is to produce steel for steel pipes in which Ca is added so that the ratio of the N content in the steel to the amount of Ca addition (kg/t) into the molten steel is from 200 to 857.

Abstract: A method of producing steel pipe excellent in sour-resistance performance, uses comprises controlling the amount of Ca addition charged into molten steel in a ladle according to a N content in the molten steel prior to Ca addition. As a result of the controlling step, a CaO content in the inclusions is in the range of 30 to 80%, the ratio of the N content in the steel to the CaO content in the inclusions satisfies the relation expressed by equation (1), and a CaS content in the inclusions satisfies the relation expressed by equation (2). 0.28?[N]/(% CaO)?2.0??(1) (% CaS)?25%??(2) where [N] represents the mass content (ppm) of N in the steel, (% CaO) represents the mass content (%) of CaO in the inclusions, and (% CaS) represents the mass content (%) of CaS in the inclusions.

Abstract: The steel for steel pipes of the present invention is the one for steel pipes excellent in sour-resistance performance including C, Mn, Si, P, S, Ti, Al, Ca, N and O, and optionally including a predetermined amount of one or more of Cr, Ni, Cu, Mo, V, B and Nb, in which inclusions in the steel have Ca, Al, O and S as main components, the CaO content in the inclusions is 30 to 80%, the ratio of the N content in the steel (ppm) to the CaO content in the inclusions (%) is from 0.28 to 2.0, and the CaS content in the inclusions is 25% or less. In addition, the method of producing steel for steel pipes of the present invention is to produce steel for steel pipes in which Ca is added so that the ratio of the N content in the steel to the amount of Ca addition (kg/t) into the molten steel is from 200 to 857.

Abstract: A steel product for a line pipe according to the invention has a composition containing, in mass %, C : 0.03% to 0.15%, Si: 0.05% to 1.0%, Mn: 0.5% to 1.8%, P: 0.015% or less, S: 0.004% or less, O: 0.01% or less, N: 0.007% or less, sol. Al: 0.01% to 0.1%, Ti: 0.024% or less, Ca: 0.0003% to 0.02%, and the balance consisting of Fe and impurities. The size of TiN in the steel product for a line pipe is at most 30 ?m. The steel product has high HIC resistance and its crack area ratio can be reduced to 3% or less.

Abstract: A low alloy steel, which has a chemical composition by mass %, of C: 0.1 to 0.55%, Si: 0.05 to 0.5%, Mn: 0.1 to 1%, S: 0.0001 to 0.005%, Al: 0.005 to 0.08%, Ti: 0.005 to 0.05%, Cr: 0.1 to 1.5%, Mo: 0.1 to 1%, O: 0.0004 to 0.005%, Ca: 0.0005 to 0.0045%, Nb: 0 to 0.1%, V: 0 to 0.5%, B: 0 to 0.005%, Zr: 0 to 0.10%, P?0.03%, and N?0.006%, with the balance being Fe and impurities, is manufactured by adjusting the value of ([Ti]/47.9)([N]/14)/([Ca])/40.1) satisfies not less than 0.0008 and not more than 0.0066, at the time of melting the said low alloy steel, wherein [Ti], [N] and [Ca] are the contents in the molten steel by mass % of Ti, N and Ca respectively. The thus-manufactured low steel alloy has a high SSC resistance with a yield stress of not less than 758 MPa.

Abstract: A steel product for a line pipe according to the invention has a composition containing, in mass %, C : 0.03% to 0.15%, Si: 0.05% to 1.0%, Mn: 0.5% to 1.8%, P: 0.015% or less, S: 0.004% or less, O: 0.01% or less, N: 0.007% or less, sol. Al: 0.01% to 0.1%, Ti: 0.024% or less, Ca: 0.0003% to 0.02%, and the balance consisting of Fe and impurities. The size of TiN in the steel product for a line pipe is at most 30 ?m. The steel product has high HIC resistance and its crack area ratio can be reduced to 3% or less.

Abstract: A steel for steel pipes which comprises, on the percent by mass basis, C: 0.2 to 0.7%, Si: 0.01 to 0.8%, Mn: 0.1 to 1.5%, S: 0.005% or less, P: 0.03% or less, Al: 0.0005 to 0.1%, Ti: 0.005 to 0.05%, Ca: 0.0004 to 0.005%, N: 0.007% or less, Cr: 0.1 to 1.5%, Mo: 0.2 to 1.0%, Nb: 0 to 0.1%, Zr: 0 to 0.1%, V: 0 to 0.5% and B: 0 to 0.005%, with the balance being Fe and impurities, in which non-metallic inclusions containing Ca, Al, Ti, N, O, and S are present, and in the said inclusions (Ca %)/(Al %) is 0.55 to 1.72, and (Ca %)/(Ti %) is 0.7 to 19 can be used as a raw material for oil country tubular goods, being used at a greater depth and in severer corrosive circumstances, such as casings and tubings for oil and/or natural gas wells, drilling pipes and drilling collars for excavation, and the like.

Abstract: A low alloy steel, which has a chemical composition by mass %, of C: 0.1 to 0.55%, Si: 0.05 to 0.5%, Mn: 0.1 to 1%, S: 0.0001 to 0.005%, Al: 0.005 to 0.08%, Ti: 0.005 to 0.05%, Cr: 0.1 to 1.5%, Mo: 0.1 to 1%, O: 0.0004 to 0.005%, Ca: 0.0005 to 0.0045%, Nb: 0 to 0.1%, V: 0 to 0.5%, B: 0 to 0.005%, Zr: 0 to 0.10%, P?0.03%, and N?0.006%, with the balance being Fe and impurities, is manufactured by adjusting the value of ([Ti]/47.9)([N]/14)/([Ca])/40.1) satisfies not less than 0.0008 and not more than 0.0066, at the time of melting the said low alloy steel, wherein [Ti], [N] and [Ca] are the contents in the molten steel by mass % of Ti, N and Ca respectively. The thus-manufactured low steel alloy has a high SSC resistance with a yield stress of not less than 758 MPa.

Abstract: A steel for steel pipes which comprises, on the percent by mass basis, C: 0.2 to 0.7%, Si: 0.01 to 0.8%, Mn: 0.1 to 1.5%, S: 0.005% or less, P: 0.03% or less, Al: 0.0005 to 0.1%, Ti: 0.005 to 0.05%, Ca: 0.0004 to 0.005%, N: 0.007% or less, Cr: 0.1 to 1.5%, Mo: 0.2 to 1.0%, Nb: 0 to 0.1%, Zr: 0 to 0.1%, V: 0 to 0.5% and B: 0 to 0.005%, with the balance being Fe and impurities, in which non-metallic inclusions containing Ca, Al, Ti, N, O, and S are present, and in the said inclusions (Ca %)/(Al %) is 0.55 to 1.72, and (Ca %)/(Ti %) is 0.7 to 19 can be used as a raw material for oil country tubular goods, being used at a greater depth and in severer corrosive circumstances, such as casings and tubings for oil and/or natural gas wells, drilling pipes and drilling collars for excavation, and the like.