Nippon Steel Sumitomo Metal Corporation

Nippon Steel & Sumikin Welding Co., Ltd.

Ryuichi Shimura

Kazuhiro Kojima

Shuichi Nakamura

Yasuhito Totsuka

Tadashi Kasuya

Manabu Mizumoto

Kiyohito Sasaki

Masaaki Toriyabe

Toshiei Hasegawa

In a flux-cored wire according to the present invention, CaFand the like are included and a total amount thereof &#x3b1; is 3.3 to 6.0% in terms of mass % with respect to a total mass, Ti oxide and the like are included and a total amount thereof &#x3b2; is 0.4 to 1.2% in terms of mass % with respect to the total mass, CaCOand the like are included and a total amount thereof is 0.1 to 0.5% in terms of mass % with respect to the total mass, and an amount of an iron powder in the flux is less than 10% in terms of mass % with respect to the total mass.

Flux-cored wire, welding method using flux-cored wire, method for manufacturing weld joint using flux-cored wire, and weld joint

In a flux-cored wire for welding an ultrahigh tensile strength steel, one or more of CaF2, BaF2, SrF2, and MgF2 are included in the wire and, when a total amount thereof is defined as &#x3b1;, the &#x3b1; is more than 2.0% and equal to or less than 8.0% in terms of mass % with respect to a total mass of the wire, one or more of Ti oxide, Si oxide, Mg oxide, and Al oxide are included in the wire and, when a total amount thereof is defined as &#x3b2;, the &#x3b2; is 0.01% to 1.20% in terms of mass % with respect to the total mass of the wire, a ratio of an amount of the CaF2 with respect to the &#x3b1; is 0.50 or more, a ratio of the &#x3b1; with respect to the &#x3b2; is 2.0 to 800.0, and Ceq defined in the following expression is 0.60% to 1.20%, Ceq=[C]+[Si]/24+[Mn]/6+[Ni]/40+[Cr]/5+[Mo]/4+[V]/14.

Flux-cored wire for welding ultrahigh tensile strength steel

A flux-cored wire for gas shielded welding use which can reduce the oxygen of weld metal to obtain a weld joint which is excellent in toughness and which enables all-position welding by direct current reverse polarity, wherein the wire contains, by mass % with respect to the wire total mass, CaO: 0.2 to 7.0%, one or more of MgF, CaF, SrF, and BaFin a total of 1.0% or more (total of fluorides and CaO being 3.0 to 12.0%), one or more of Si, Al (less than 0.3%), Ti, Mg, Zr, Ca, Ce, and La in a total of 0.2 to 2.0%, and one or more oxides of Si, Mn, Al, Ti, B, and Zr in a total of 0.2 to 3.0%, &#x3b1;=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+Nb/10+5B is 0.15 to 0.40%, P and S in a total of 0.040% or less, a balance of Fe, an arc stabilizer, unavoidable impurities, and a content of iron powder in the flux of 5.0% or less.

Flux-cored wire for gas shield arc welding use enabling all-position welding

A method of production of a welded joint which enables improvement of the fatigue strength in the case where measures for improvement of the fatigue strength cannot be applied due to the presence of structurally sealed regions is provided. The method is provided with a first weld step which performs welding by forming an inside weld toe or root part by using a weld metal with a transformation start temperature of 175&#xb0; C. to 400&#xb0; C. in range, at least parts of the weld metal forming the inside weld toe or root part which was formed at the first weld step becoming unmelted parts, and a second weld step which performs welding for building up the weld metal by a single pass by a weld heat input by which all of the unmelted parts are retransformed to austenite so as to introduce compressive residual stress to the inside weld toe or root part.

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Tokyo, Japan

Ryuichi Shimura