Mitsubishi Heavy Industries Limited

Mitsubishi Jukogyo Kabushiki Kaisha

Other

Sumitomo Metal Industries, Inc.

Mitsubishi Hitachi Power Systems, Ltd.

National Institute for Materials Science

Nobuyoshi Komai

Fujimitsu Masuyama

Tomomitsu Yokoyama

Yuichi Hirakawa

Hiroaki Fukushima

Fumio Nishi

Masaaki Igarashi

Masahiro Kobayashi

Hiroaki Yoshida

Hiroyuki Hirata

Kaori Kawano

Takayuki Kawano

Masaaki Fujita

Takumi Tokiyoshi

Masaki Honda

Kazuhiro Kimura

Kaori Miyata

Fumitoshi Sakata

Hiroyuki Ohyama

Iwami Ishihara

Nobuhiko Saito

Takao Kan

Toshiaki Nishio

Kota Sawada

Yasuhiro Ukeguchi

Takeshi Miyazawa

Kaoru Sekido

Kimihiko Tominaga

Koichi Teshima

Akinori Yamaguchi

Eiji Murakami

Masahiko Hokano

Toshiyuki Imazato

A repair welding method according to at least one embodiment is for a member in which a first end and a second end of a parent material are connected by welding and includes: a step of removing a portion including at least a part of a first heat-affected zone of an existing welded portion of the member; and a step of performing repair welding after removing the portion. In a cross-section including the parent material and the existing welded portion, all intersection portions between the first heat-affected zone of the existing welded portion and a second heat-affected zone due to the repair welding have an intersection angle between the first heat-affected zone and the second heat-affected zone of 70° to 110°.

Repair welding method

A faulted condition determination method is designed to detect a chromium content and a nickel content in a predetermined boundary region proximate to a boundary between a high-strength ferrite steel and a weld material in a welded joint in which the high-strength ferrite steel and another steel are welded together using the weld material containing nickel and to thereby determine the faulted condition of the predetermined boundary region based on the chromium content and the nickel content. Accordingly, it is possible to appropriately determine the faulted condition of welding of a replacement part in which a high-strength ferrite steel and another steel are welded together using a nickel-based weld material.

Faulted condition determination device and faulted condition determination method

A first measured value of a specific physical quantity at a target portion is correlated with a damage evaluation index to calculate a damage degree corresponding to the first measured value. The specific physical quantity is measured at least once at a position corresponding to the first measurement position in another time period having a different usage elapsed time from that of the first measurement, and these second and subsequent measured values are correlated with damage degrees calculated based on temporal changes corresponding to the second and subsequent measurements. A new damage evaluation index is approximately calculated based on a relationship between the first, second, and subsequent measured values and the damage degrees corresponding to the first, second, and subsequent measured values.

Damage evaluation method and maintenance evaluation index decision method

A high-precision method for evaluating creep damage of high tension heat resistant steel used in high temperature exposed apparatuses involves comparing particle size behavior varying with creep damage progress of crystal grains having a crystal orientation difference of about 2 degrees or more, preferably 3 degrees or more at an evaluated part on the basis of a working curve or a working map prepared in advance by looking for the relation of grain sizes to creep damage extent. A high-precision apparatus evaluates the creep damage of high tension heat resistant steel used in high temperature exposed apparatuses. A measuring device measures particle size variation behavior of crystal grains or sub grains having a crystal orientation difference of about 2 degrees or more with regard to a specimen at the evaluated part of high tension heat resistant steel and a working curve or a working map prepared in advance by looking for the relation of the grain sizes with respect to the creep damage extent (including creep damage rates) at every level of loaded stress. The creep damage extent is evaluated by comparing the grain size variation behavior measured by the measuring device with a working curve or a working map selected on the basis of loaded stress.

High-precision method and apparatus for evaluating creep damage

A welding method and a welded joint for high strength, temperature resistant steels produce the same strength as the base metal in the welded joint, thereby resolving strength problems in the heat affected area by making a simple change to the welding method. Additionally, this advantage is extended to high strength ferrite heat resistant steels by providing a multi-pass buildup welding method for such high strength ferrite heat resistant steels. A multi-layered capfusion area extends past the heat affected areathat lies outside grooveand the surface area of the foregoing extension that is required to impart the same level of creep strength as is inherent in the base metal is based on the relationship between the groove width and the base metal thickness shown as hatched area in FIG.(B).

Welded joints in high strength, heat resistant steels, and a welding method therefor

A high strength, low alloy, heat resistant steel having excellent weldability has an average crystal grain diameter of at most 110 &mgr;m and consists essentially of, by mass %: C: 0.03-0.15%, Si: at most 1%, Mn: at most 2%, P: at most 0.03%, S: at most 0.03%, Ni: at most 0.5%, Cu: at most 0.5%, Cr: 1.8-2.8%, V: 0.1-0.3%, Nb: 0.01-0.08%, Mo: 0.05-0.35%, W: 1.2-1.8%, Ti: 0.001-0.05%, B: 0-0.02%, Al: at most 0.1%, O: at most 0.1%, N: in an amount satisfying the formula &lsqb;%N&rsqb;&lE;&lsqb;%Ti&rsqb;&plus;5&lsqb;%B&rsqb;&plus;0.004, and a remainder of unavoidable impurities.

High strength, low alloy, heat resistant steel

This invention provides a welding material for low chromium (Cr) ferritic heat-resisting steel having high toughness, wherein the chemical composition of welding metal comprises, in weight %, carbon (c) 0.04-0.1%, silicon (Si) 0.1-0.6%, manganese (Mn) 0.1-0.6%, phosphorus (P) 0.0005-0.03%, sulfur (S) 0.0005-0.015%, chromium (Cr) 1.75-2.5%, nickel (Ni) 0.01-0.8%, molybdenum (Mo) 0.05-1.5%, vanadium (V)0.01-0.5%, tungsten (W) 0.05-2%, niobium (Nb) 0.01-0.2%, tantalum (Ta) 0.01-0.5%, aluminum (Al) 0.003-0.05%, boron (B) 0.0001-0.01%, nitrogen (N) 0.003-0.03%, and the remainder comprises iron and inevitable impurities. The welding material satisfies the following formula: C+Cr/20+Mo/15+V/10+W/7+5B.ltoreq.0.8%. According to this invention, the welding material is suitable for welding low Cr ferritic heat-resisting steels having high strength such as those used in steam generators and heat exchangers of boilers, etc. which are exposed to high temperatures and high pressures, more particularly, at a high temperature of 500.degree. C. or more.

Welding material for low chromium (Cr) ferritic steel having high

This invention provides low-Cr ferritic steels and low-Cr ferritic cast steels having excellent high-temperature strength and weldability. These low-Cr ferritic steels and low-Cr ferritic cast steels consist essentially of, on a weight percentage basis, 0.03 to 0.12% C, 0.05 to 0.7% Si, 0.05 to 1% Mn, 0.002 to 0.025% P, 0.001 to 0.015% S, 0.3 to 3% Cr, 0.01 to 1% Ni, 0.05 to 3% Mo, 0.01 to 0.5% V, 0.1 to 3% W, 0.01 to 0.2% Nb, 0.02 to 1.5% Re, 0.003 to 0.05% Al, 0.0001 to 0.01% B, 0.003 to 0.03% N, and the balance being Fe and incidental impurities, and have excellent high-temperature strength and weldability.

Low-Cr ferritic steels and low-Cr ferritic cast steels having excellent

A low Mn-low Cr ferritic heat resistant steel consisting essentially of, in weight %: 0.02-0.20% C, up to 0.7% Si, less than 0.1% Mn, up to 0.8% Ni, 0.8-3.5% Cr, 0.01-3.0% W, 0.1-0.5% V, 0.01-0.20% Nb, 0.001-0.05% Al, 0.0005-0.05% Mg, 0.0005-0.01% B, less than 0.05% N, up to 0.03% P, up to 0.015% S, 0.001-0.05% Ti and the balance Fe and incidental impurities, wherein the B content is defined so as to satisfy the following formula (14/11)B&gt;N-N(V/51)/{(C/12)+(N/14)}-N(Nb/93)/{(C/12)+(N/14)}-N(Ti/48)/{C/12 )+(N/14)}. The steel can further contain optionally 0.01-1.5% Mo, and/or one or more elements selected from the group consisting of 0.01-0.2% La, 0.01-0.2% Ce, 0.01-0.2% Y, 0.01-0.2% Ca, 0.01-0.2% Ta and 0.01-0.2% Zr. The steel can be used in place of the austenitic steels or high Cr ferritic steels, since it has remarkably improved toughness, workability and weldability, and excellent creep properties at elevated temperatures.

Low Mn-low Cr ferritic heat resistant steel excellent in strength at

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Nagasaki, Japan

Nobuyoshi Komai