Kobe Steel, Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Minoru Otsu

Hidenori Nako

Ken Yamashita

Yoshitomi Okazaki

Hideaki Takauchi

Genichi Taniguchi

Mikihiro Sakata

Hayato Koike

Liang Chen

This welded structure comprises a weld metal which contains C, Si, Mn, Cr, Mo, V, Nb, N and O in prescribed amounts respectively with the balance being Fe and unavoidable impurities and which exhibits an A value of 200 or more and a Z value of 0.05 or more. The A value is calculated from the element contents of the weld metal according to the formula: A value=([V]/51+[Nb]/93)/{[V]&#xd7;([Cr]/5+[Mo]/2)}&#xd7;10. The Z value is calculated according to the formula: Z value=N&#xd7;[insol. V] [wherein N (particles/&#x3bc;m) is the number density of carbide particles present in a prior austenite grain boundary per unit grain boundary in the stress-relief annealed weld metal, and [insol. V] is the concentration of compound-type V as determined by analyzing an extraction residue of the stress-relief annealed weld metal].

Weld metal and welded structure

A weld metal according to the present invention has a specific chemical composition, contains carbide particles each having an equivalent circle diameter of greater than 0.5 &#x3bc;m in a number of 0.25 or less per micrometer of grain boundary length, and has an A-value as specified by Formula (1) of 0.12 or more, Formula (1) expressed as follows:-value=([V]/51+[Nb]/93)/([Cr]/52+[Mo]/96) &#x2003;&#x2003;(1)where [V], [Nb], [Cr], and [Mo] are contents (percent by mass) of V, Nb, Cr, and Mo, respectively, in the weld metal.

Weld metal having excellent temper embrittlement resistance

This weld metal has excellent creep characteristics and has a given chemical composition. In the weld metal, the value A defined by equation (1) is 200 or greater, and carbide particles each having an equivalent-circle diameter of 0.40 &#x3bc;m or more have an average equivalent-circle diameter less than 0.85 &#x3bc;m. In the segments that connect the centers of three or more carbide particles which are present on a 6-&#x3bc;m straight line and which each has an equivalent-circle diameter of 0.40 &#x3bc;m or more, the sum of the lengths of the portions where the segments intersect the carbide particles is 25% or more of the overall length of the segments.Value=([V]/51+[Nb]/93)/{[V]&#xd7;([Cr]/5+[Mo]/2)}&#xd7;10&#x2003;&#x2003;(1)In the equation, [V], [Nb], [Cr], and [Mo] respectively indicate the contents (mass %) of V, Nb, Cr, and Mo in the weld metal.

Weld metal with excellent creep characteristics

Provided is a welding metal in which the chemical component composition thereof is appropriately controlled; an A value that is specified by a predetermined relational expression satisfies the requirement of being 3.8% to 9.0%; an X value that is specified by a predetermined relational expression satisfies the requirement of being 0.5% or greater; the area percentage of carbide particles having a circle-equivalent diameter of 0.20 &#x3bc;m or greater in the welding metal is 4.0% or less; and the number of carbide particles having a circle-equivalent diameter of 1.0 &#x3bc;m or greater is 1000 particles/mmor less. This welding metal, which can exhibit not only high strength but also good low-temperature toughness and good drop-weight characteristics, is useful as a material for a pressure vessel in a nuclear power plant.

Welding metal having excellent low-temperature toughness and drop-weight characteristics

Provided is a welding metal in which a predetermined chemical component composition is satisfied, the A value as specified by formula (1) is 3.8% to 9.0%, and the surface area percentage of carbide having a circle-equivalent diameter of 0.20 &#x3bc;m or greater in the welding metal is 4.0% or less.value=0.8&#xd7;[C]&#x2212;0.05&#xd7;[Si]+0.5&#xd7;[Mn]+0.5&#xd7;[Cu]+[Ni]&#x2212;0.5&#xd7;[Mo]+0.2&#xd7;[Cr]&#x2003;&#x2003;(1)(Provided that [C], [Si], [Mn], [Cu], [Ni], [Mo] and [Cr] are the C, Si, Mn, Cu, Ni, Mo and Cr content (by mass percent), respectively) The welding metal is useful as a material for a pressure vessel of a nuclear power plant as the welding metal is high in strength and has good low-temperature toughness and drop-weight characteristics.

To provide weld metal that has a high strength and toughness in the as-welded condition or in the annealed condition. The weld metal of the present invention contains by weight %, C: 0.04-0.15%, Si: 0.50% or less, Mn: 1.0-1.9%, Ni: 1.0-4.0%, Cr: 0.10-1.0%, Mo: 0.20 to 1.2%, Ti: 0.010-0.060%, Al: 0.030% or less, O: 0.15-0.060%, N: 0.010% or less, Fe and inevitable impurities as the remaining contents. The weld metal is further characterized by the fact that the ratio of Ti content (%) to Si content (%) i.e., [compound type Ti]/[compound type Si] is more than 1.5, and the number A defined by the following formula is 0.50 or more, wherein A=[Ti]/([O]&#x2212;1.1&#xd7;[Al]+0.05&#xd7;[Si]).

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Fujisawa, Japan

Minoru Otsu