Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Katsuki Tanaka

Hiroyuki Hirata

Hirokazu Okada

Junichi Higuchi

Kana Jotoku

Toshihide Ono

Tomoaki Hamaguchi

Yoshitaka Nishiyama

Hiroyuki Semba

Atsuro Iseda

Mitsuru Yoshizawa

Shinnosuke Kurihara

Masahiro Seto

Masayuki Takiguchi

A method of producing a ferritic heat-resistant steel welded joint, the method including: a multi-layer welding step in which a ferritic heat-resistant steel base material including B at 0.006% by mass to 0.023% by mass is multi-layer welded using a Ni-based welding material for heat-resistant alloy, wherein root pass welding is performed under a welding condition such that a ratio of an area [S] that has been melted of the ferritic heat-resistant steel base material to an area [S] of a weld metal, in a transverse cross-section of a weldment after the root pass welding but before second pass welding in the multi-layer welding step, satisfies the following formula (1): 0.1&#x2264;[S]/[S]&#x2264;&#x2212;50&#xd7;[% B]+1.3, with respect to a mass percent of B, [% B], which is included in the ferritic heat-resistant steel base material.

Method of producing ferritic heat-resistant steel welded joint

A austenitic stainless steel which has a chemical composition consisting of, by mass %, C: 0.04 to 0.12%, Si: 0.25 to 0.55%, Mn: 0.7 to 2.0%, P: 0.035% or less, S: 0.0015% or less, Cu: 0.02 to 0.80%, Co: 0.02 to 0.80%, Ni: 10.0 to 14.0%, Cr: 15.5 to 17.5%, Mo: 1.5 to 2.5%, N: 0.01 to 0.10%, Al: 0.030% or less, O: 0.020% or less, Sn: 0 to 0.01%, Sb: 0 to 0.01%, As: 0 to 0.01%, Bi: 0 to 0.01%, V: 0 to 0.10%, Nb: 0 to 0.10%, Ti: 0 to 0.10%, W: 0 to 0.50%, B: 0 to 0.005%, Ca: 0 to 0.010%, Mg: 0 to 0.010% and REM: 0 to 0.10%, with the balance being Fe and impurities, and satisfying [18.0&#x2264;Cr+Mo+1.5&#xd7;Si&#x2264;20.0] and [14.5&#x2264;Ni+30&#xd7;(C+N)+0.5&#xd7;(Mn+Cu+Co)&#x2264;19.5].

Austenitic stainless steel

A austenitic stainless steel weld metal which has a chemical composition consisting of, by mass %, C: 0.01 to 0.10%, Si: 0.20 to 0.70%, Mn: 0.8 to 2.5%, P: 0.035% or less, S: 0.0030% or less, Cu: 0.01 to 0.60%, Co: 0.01 to 1.00%, Ni: 8.0 to 12.0%, Cr: 14.5 to 17.5%, Mo: 1.0 to 2.2%, N: 0.02 to 0.10%, Al: 0.030% or less, O: 0.020% or less, Sn: 0 to 0.01%, Sb: 0 to 0.01%, As: 0 to 0.01%, Bi: 0 to 0.01%, V: 0 to 0.10%, Nb: 0 to 0.10%, Ti: 0 to 0.10%, W: 0 to 0.50%, B: 0 to 0.005%, Ca: 0 to 0.010%, Mg: 0 to 0.010% and REM: 0 to 0.10%, with the balance being Fe and impurities, and satisfying [17.5&#x2264;Cr+Mo+1.5&#xd7;Si&#x2264;19.5] and [11.0&#x2264;Ni+30&#xd7;(C+N)+0.5&#xd7;(Mn+Cu+Co)&#x2264;17.0].

Austenitic stainless steel weld metal and welded structure

The present invention provides a welding material for ferritic heat-resistant steel, a welded joint for ferritic heat-resistant steel, and a method for producing the welded joint for to form a weld metal having a high creep strength and a high toughness in welding a ferritic heat-resistant steel that contains B. The welding material for ferritic heat-resistant steel has a chemical composition containing, in mass %, C: 0.06 to 0.10%, Si: 0.1 to 0.4%, Mn: 0.3 to 0.7%, Co: 2.6 to 3.4%, Ni: 0.01 to 1.10%, Cr: 8.5 to 9.5%, W: 2.5 to 3.5%, Nb: 0.02 to 0.08%, V: 0.1 to 0.3%, Ta: 0.02 to 0.08%, B: 0.007 to 0.015%, N: 0.005 to 0.020%, with the balance being Fe and impurities, and satisfying Formula (1):0.5&#x2264;Cr+6Si+1.5W+11V+5Nb+10B&#x2212;40C&#x2212;30N&#x2212;4Ni&#x2212;2Co&#x2212;2Mn&#x2264;10.0&#x2003;&#x2003;(1).

Welding material for ferritic heat-resistant steel, welded joint for ferritic heat-resistant steel, and method for producing welded joint for ferritic heat-resistant steel

An austenitic stainless steel weld metal which has a chemical composition consisting of, by mass %, C: 0.05 to 0.11%, Si: 0.10 to 0.50%, Mn: 1.0 to 2.5%, P: 0.035% or less, S: 0.0030% or less, Co: 0.01 to 1.00%, Ni: 9.0 to 11.5%, Cr: 17.0 to 21.0%, Nb: 0.60 to 0.90%, Ta: 0.001 to 0.100%, N: 0.01 to 0.15%, Al: 0.030% or less, O: 0.020% or less, V: 0 to 0.10%, Ti: 0 to 0.10%, W: 0 to 0.50%, Mo: 0 to 0.50%, Cu: 0 to 0.50%, B: 0 to 0.005%, Ca: 0 to 0.010%, Mg: 0 to 0.010% and REM: 0 to 0.10%, with the balance being Fe and impurities, and satisfying [Nb&#x2212;7.8&#xd7;C&#x2264;0.25].

A high Cr austenitic stainless steel with a chemical composition consisting of in terms of % by mass, 0.03 to 0.12% of C, 0.10 to 1.00% of Si, 0.10 to 3.00% of Mn, 0.030% or less of P, 0.020% or less of S, 21.50 to 28.00% of Cr, more than 26.00 and not more than 35.00% of Ni, more than 2.00 and not more than 5.00% of W, 0.80% or less of Co, 0.01 to 0.70% of V, 0.15 to 1.00% of Nb, 0.001 to 0.040% of Al, 0.0001 to 0.0100% of B, 0.010 to 0.400% of N, 0.001 to 0.200% of Zr, 0.001 to 0.200% of Nd, 0.001 to 0.200% of Ta, 0.020 to 0.200% of Ta+0.8Nd+0.5Zr, 0.025% or less of Ti+Sn+Sb+Pb+As+Bi, 0.0090% or less of O, and a remainder consisting of Fe and impurities.

High Cr-based austenitic stainless steel

There is provided an austenitic stainless steel pipe excellent in steam oxidation resistance. The austenitic stainless steel pipe excellent in steam oxidation resistance contains, by mass percent, 14 to 28% of Cr and 6 to 30% of Ni, and is configured so that a region satisfying the following Formula exists in a metal structure at a depth of 5 to 20 &#x3bc;m from the inner surface of the steel pipe:(&#x3b1;/&#x3b2;)&#xd7;&#x3b4;/&#x3b5;&#xd7;100&#x2267;0.3where the meanings of symbols in the above Formula are as follows:&#x3b1;: sum total of the number of pixels of digital image in region in which orientation difference of adjacent crystals detected by electron backscattering pattern is 5 to 50 degrees&#x3b2;: the number of total pixels of digital image in region of measurement using electron backscattering pattern&#x3b5;: analysis pitch width of electron backscattering pattern (&#x3bc;m)&#x3b4;: grain boundary width (&#x3bc;m).

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Tokyo, Japan

Katsuki Tanaka