Nippon Steel Corporation

Other

Nippon Steel Corpopration

Hiroshi Tamehiro

Takuya Hara

Hitoshi Asahi

Yoshio Terada

Narasimha-Rao Venkata Bangaru

Jayoung Koo

Michael J Luton

Clifford W Petersen

Hajime Nakasugi

Hiroo Mazuda

Hiroaki Masui

Hiroyuki Ogawa

Yasumitsu Onoe

Yuzuru Yoshida

Rikio Chiziiwa

Yoshifumi Sakumoto

Mamoru Ohashi

Koichiro Keira

Kazuo Funato

Yoshinori Ogata

Hajime Ishikawa

Akira Kawakami

Akihiko Takahashi

Ryuji Uemori

Rikio Chijiiwa

Taro Muraki

Koichi Shinada

Shigeru Ohkita

Masatoki Nakayama

Kunio Koyama

Naoki Saito

Masana Imagumbai

Tetuo Takeda

Masanobu Yamaguti

Turugi Kimura

Seiji Eiro

Shinogu Tamukai

Masahiko Murata

Koyoshi Nishioka

Isamu Kimoto

Asahi Hitoshi

Masaaki Sugiyama

To provide a super-high strength line pipe that is excellent in low temperature toughness, can be field welded easily, and has a tensile strength of at least 900 MPa (exceeding &times;100 of the API standard), and a production method thereof. The present invention relates to a super-high strength line pipe produced by shaping a steel plate into a pipe shape and arc welding seam portions, the strength of a base steel portion is 900 to 1,100 MPa and the strength of the weld metal is higher than the base steel strength &minus;100 MPa. In the steel pipe, the Ni content of the weld metal is higher by at least 1% than that of the base steel. The combination of the chemical components of the steel plate with those of the weld metal, for accomplishing these steel pipes by a U&O step is shown concretely. A production method of the steel plate and the welding method for achieving the steel pipe are also described. Furthermore, a method of reducing the strength of the inner surface of the weld metal to restrict cracking at the time of pipe expansion is also shown.

Super-high-strength line pipe excellent in low temperature toughness and production method thereof

An ultra-high strength steel having excellent ultra-low temperature toughness, a tensile strength of at least about 930 MPa (135 ksi), and a microstructure comprising predominantly fine-grained lower bainite, fine-grained lath martensite, or mixtures thereof, transformed from substantially unrecrystallized austenite grains and comprising iron and specified weight percentages of the additives: carbon, silicon, manganese, copper, nickel, niobium, vanadium, molybdenum, chromium, titanium, aluminum, calcium, Rare Earth Metals, and magnesium, is prepared by heating a steel slab to a suitable temperature; reducing the slab to form plate in one or more hot rolling passes in a first temperature range in which austenite recrystallizes; further reducing said plate in one or more hot rolling passes in a second temperature range below said first temperature range and above the temperature at which austenite begins to transform to ferrite during cooling; quenching said plate to a suitable Quench Stop Temperature; and stopping said quenching and allowing said plate to air cool to ambient temperature.

Ultra-high strength, weldable steels with excellent ultra-low temperature toughness

A method is provided for producing an ultra-high strength steel having a tensile strength of at least about 900 MPa (130 ksi), a toughness as measured by Charpy V-notch impact test at &minus;40&deg; C. (&minus;40&deg; F.) of at least about 120 joules (90 ft-lbs), and a microstructure comprising predominantly fine-grained lower bainite, fine-grained lath martensite, or mixtures thereof, transformed from substantially unrecrystallized austenite grains and comprising iron and specified weight percentages of the additives: carbon, silicon, manganese, copper, nickel, niobium, vanadium, molybdenum, chromium, titanium, aluminum, calcium, Rare Earth Metals, and magnesium. A steel slab is heated to a suitable temperature; the slab is reduced to form plate in one or more hot rolling passes in a first temperature range in which austenite recrystallizes; said plate is further reduced in one or more hot rolling passes in a second temperature range below said first temperature range and above the temperature at which austenite begins to transform to ferrite during cooling; said plate is quenched to a suitable Quench Stop Temperature; and said quenching is stopped and said plate is allowed to air cool to ambient temperature.

Method for producing ultra-high strength, weldable steels with superior toughness

An ultra-high strength boron-containing steel having a tensile strength of at least about 900 MPa (130 ksi), a toughness as measured by Charpy V-notch impact test at &minus;40&deg; C. (&minus;40&deg; F.) of at least about 120 joules (90 ft-lbs), and a microstructure comprising predominantly fine-grained lower bainite, fine-grained lath martensite, or mixtures thereof, transformed from substantially unrecrystallized austenite grains and comprising iron and specified weight percentages of the additives: carbon, silicon, manganese, copper, nickel, niobium, vanadium, molybdenum, chromium, titanium, aluminum, calcium, Rare Earth Metals, and magnesium, is prepared by heating a steel slab to a suitable temperature; reducing the slab to form plate in one or more hot rolling passes in a first temperature range in which austenite recrystallizes; further reducing said plate in one or more hot rolling passes in a second temperature range below said first temperature range and above the temperature at which austenite begins to transform to ferrite during cooling; quenching said plate to a suitable Quench Stop Temperature; and stopping said quenching and allowing said plate to air cool to ambient temperature.

Ultra-high strength, weldable, boron-containing steels with superior toughness

An ultra-high strength essentially boron-free steel having a tensile strength of at least about 900 MPa (130 ksi), a toughness as measured by Charpy V-notch impact test at &minus;40&deg; C. (&minus;40&deg; F.) of at least about 120 joules (90 ft-lbs), and a microstructure comprising predominantly fine-grained lower bainite, fine-grained lath martensite, or mixtures thereof, transformed from substantially unrecrystallized austenite grains and comprising iron and specified weight percentages of the additives: carbon, silicon, manganese, copper, nickel, niobium, vanadium, molybdenum, chromium, titanium, aluminum, calcium, Rare Earth Metals, and magnesium, is prepared by heating a steel slab to a suitable temperature; reducing the slab to form plate in one or more hot rolling passes in a first temperature range in which austenite recrystallizes; further reducing said plate in one or more hot rolling passes in a second temperature range below said first temperature range and above the temperature at which austenite begins to transform to ferrite during cooling; quenching said plate to a suitable Quench Stop Temperature; and stopping said quenching and allowing said plate to air cool to ambient temperature.

Ultra-high strength, weldable, essentially boron-free steels with superior toughness

Steel having improved toughness in welding heat-affected zone

A steel plate comprising by weight C: 0.01 to 0.1%, Si: 0.02 to 0.5%, Mn: 0.6 to 2.0%, P&lt;0.020%, S&lt;0.010%, O&lt;0.005%, Cr: 0.1 to 0.5%, Cu: 0.1 to 1.0%, Al: 0.005 to 0.05%, and Ca: 0.0005 to 0.005%, Mn, S, and O having respective contents regulated to satisfy a requirement represented by the formula Mn.times.(S+O).ltoreq.1.5 .times.10.sup.-2, and 0.01 to 0.1% in total of at least one member selected from the group consisting of Nb, V, and Ti with the balance consisting of Fe and unavoidable impurities. This steel plate has excellent corrosion resistance and sulfide stress cracking resistance in an environment containing carbon dioxide gas and hydrogen sulfide.

Steel plate having excellent corrosion resistance and sulfide stress

Weldable high strength steel having excellent low temperature toughness

High strength line pipe steel having low yield ratio and excellent in

A wire for gas metal arc welding containing 0.01 to 0.06 wt % of C, 0.10 to 0.60 wt % of Si, 0.9 to 3.1 wt % of Mn, 0.7 to 2.0 wt % of Cr, 0.005 to 0.06% of Ti, not greater than 0.08 wt % of Al and if necessary, 0.05 to 0.30 wt % of Cu, and the balance of Fe and unavoidable impurities. This wire improves the selective corrosion resistance and the low temperature toughness of the resulting weld metal, and is particularly suitable for circumferential welding of line pipes for transporting CO.sub.2 -containing petroleum, natural gases or CO.sub.2.

Line pipe metal arc welded with wire alloy

High-corrosion-resistant martensitic stainless steel having excellent

A method of producing clad steel plate comprises the steps of preparing an assembly slab by superposing a stainless-steel or nickel alloy cladding material onto base metal consisting essentially of, by weight, 0.020 to 0.06% carbon, 0.5% or less silicon, 1.0 to 1.8% manganese, 0.03% or less phosphorus, 0.005% or less sulfur, 0.08 to 0.15% niobium, 0.005 to 0.03% titanium, 0.05% or less aluminum, 0.002 to 0.006% nitrogen, and one or two elements selected from among a group consisting of 0.05 to 1.0% nickel, 0.05 to 1.0% copper, 0.05 to 0.5% chromium, 0.05 to 0.3% molybdenum and 0.001 to 0.005% calcium, with the balance being iron and unavoidable impurities, and welding its periphery; heating the slab to 1100.degree. to 1250.degree. C.; rolling the slab at a reduction ratio of 5 or more and a rolling finish temperature of 900.degree. to 1050.degree. C.; air cooling for 60 to 200 seconds; cooling the slab from a temperature of at least 750.degree. C. to 555.degree. C. or below at a cooling rate of 5.degree. to 40.degree. C./sec, and following this by air cooling.

Method of producing clad steel plate having good low-temperature

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.degree. C., followed by air cooling.

Building construction steel having excellent fire resistance and low

Process for manufacturing building construction steel having excellent

A method of producing steel plate with good low-temperature toughness comprises the steps of casting a steel melt consisting of 0.001-0.300 wt % C, not more than 0.8 wt % Si, 0.4-2.0 wt % Mn, not more than 0.007 wt % Al, 0.0010-0.0100 wt % O and the remainder of iron and unavoidable, impurities, and subjecting the cast steel either as it is or after rolling at a small reduction ration to accelerated cooling. In the cooling step, a fine-grained acicular ferrite texture having oxide-system inclusions as the nuclei develops radially and provides the resulting steel plate with excellent low-temperature toughness.

Method of producing steel plate with good low-temperature toughness

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Futtsu, Japan

Hiroshi Tamehiro