Kobe Steel, Ltd.

Kabushiki Kaisha Kobe Seiko Sho

The Japan Steel Works, Ltd.

Mikihiro Sakata

Hidenori Nako

Ken Yamashita

Rinzo Kayano

Minoru Otsu

Hideaki Takauchi

Genichi Taniguchi

Yuta Honma

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

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Fujisawa, Japan

Mikihiro Sakata