Nisshin Steel Co., Ltd.

Satoshi Suzuki

Naoto Hiramatsu

Hiroshi Fujimoto

Takashi Yamauchi

Junichi Katsuki

Hanji Ishikawa

Toshiro Adachi

Seiichi Isozaki

Yasutoshi Hideshima

Teruyoshi Iida

Masato Otsuka

Hideki Tanaka

Naoki Hirakawa

Takashi Igawa

Shigeru Morikawa

Toshirou Nagoya

A stainless steel material having compositions which contain on the basis of percent by mass, C from 0.04 to 0.12%, Ni from 0 (including a case of no addition) to 5.0%, Cr from 12.0 to 17.0%, N from 0.0 to 0.10%, Si from 0.2 to 2.0%, Mn at 2.0% or less, Cu from 0.0 to 2.0%, P at 0.06% or less, S at 0.006% or less, with residue being Fe and unavoidable impurities. Further, a parent phase has any one of a single phase structure of ferrite phase or martensite phase and a diploid phase structure of ferrite phase and martensite phase. An end of the base material is melt-welded as a joint to form a pipe. The parent phase is provided with carbide uniformly separated at grain boundaries and within grains, with a dissolved amount of C being 0.03% by mass or less.

High-strength stainless steel pipe

Provided is a high-strength stainless steel material having less deterioration in mechanical strength and improved workability, particularly bending workability compared with conventional steel materials. The high-strength stainless steel material of the present invention has a specific composition, has a metal microstructure composed of two phases, that is a ferrite phase and a martensite phase, has a &#x3b3;max of from 50 to 85, the &#x3b3;being represented by the following equation (1):&#x3b3;=420W+470W+23W+7W&#x2212;11.5W&#x2212;11.5W+189&#x2003;&#x2003;(1)wherein, W, W, W, W, W, and W; represent contents (unit: mass %) of C, N, Ni, Mn, Cr, and Si relative to the total mass of the stainless steel material, respectively; and has a difference of 300 HV or less in hardness between the ferrite phase and the martensite phase.

High-strength stainless steel material and production process of the same

A new austenitic stainless steel containing approximately 0.1-1.0 mass % of Si and not more than approximately 0.003 mass % of Al. Nonmetallic inclusions dispersed in a steel matrix are converted to MnO&#x2014;SiO&#x2014;AlOcontaining not less than approximately 15 mass % of SiOand not more than approximately 40 mass % of AlO. During steel making, molten steel is covered with basic slag and heavily deoxidized with a Si alloy whose Al content is controlled to not more than approximately 1.0 mass % in a vacuum or non-oxidizing atmosphere. The austenitic stainless steel sheet can be formed to an objective shape without the occurrence of cracking due to its decrease in susceptibility to cracking and its good formability.

Method of manufacturing austenitic stainless steel having less susceptibility to cracking during forming

A ferritic or martensitic stainless steel has the structure that Cu-enriched particles with concentration of C not less than 0.1 mass % or concentration of Sn and/or In not less than 10 mass % were dispersed in a matrix. Precipitation and dispersion of Cu-enriched particles is realized by aging the stainless steel at 500&#x2013;900&#xb0; C. for 1 hour or longer on any stage after a hot-rolling step until a forming step to a final product. The ferritic stainless steel contains 0.01&#x2013;1.0% C, Si up to 1.0%, Mn up to 1.0%, 15&#x2013;30% Cr, Ni up to 6.0% and 0.5&#x2013;6.0% Cu. The martensitic stainless steel contains 0.01&#x2013;0.5% C, Si up to 1.0%, Mn up to 1.0%, 10&#x2013;15% Cr, Ni up to 6.0% and 0.5&#x2013;6.0% Cu. Since Cu-enriched particles are dispersed for improvement of machinability instead of addition of S, Pb, Bi or Se, the stainless steel is machined to an objective shape without any harmful influence on workability, corrosion-resistance and the environment.

Ferritic and martensitic stainless steels excellent in machinability

An austenitic stainless steel comprising (C+&#xbd;N) up to 0.060 mass %, Si up to 1.0 mass %, Mn up to 5 mass %, S up to 0.003 mass %, S/Mn ratio up to 0.003, 15&#x2013;20 mass % Cr, 5&#x2013;12 mass % Ni, Cu up to 5 mass %, 0&#x2013;3.0 mass % Mo and the balance being Fe except inevitable impurities under the condition that a value Md(representing a ratio of a strain-induced martensite) defined by the under-mentioned formula is controlled within a range of &#x2212;60 to &#x2212;10. Hardness increase of the steel sheet after being cold-rolled is preferably 20% or more as Vickers hardness. A metallurgical structure of the steel sheet is preferably adjusted to grain size number of #8 to #11 in a finish annealed state. The steel sheet is blanked with high dimensional accuracy, and a die life is also prolonged.Md=551&#x2212;462(C+N)&#x2212;9.2Si&#x2212;29(Ni+Cu)&#x2212;8.1Mn&#x2212;13.7Cr&#x2212;18.5Mo.

Austenitic stainless steel excellent in fine blankability

A fuel tank for a motor vehicle is fabricated from an austenitic stainless steel sheet having elongation of 50% or more after fracture by a uniaxial stretching test with a work-hardening coefficient of 4000 N/mmor a ferritic stainless steel sheet having elongation of 30% or more after fracture with Lankford value of 1.3 or more. The stainless steel sheets are reformed to a complicated shape of a fuel tank without work flaws such as cracks or break-down. Excellent corrosion-resistance of stainless steel itself is maintained in the fabricated fuel tank. Consequently, the proposed fuel tank is used without diffusion of gasoline to the open air over a long term.

Stainless steel fuel tank for automobile

A fuel-filler tube, which is made of a welded pipe of corrosion-resistant austenitic or ferritic stainless steel, has a fuel-supply opening with high dimensional accuracy. The austenitic stainless steel has hardness of 180 HV or less with a work-hardening coefficient of 0.49 or less. The ferritic stainless steel has Lankford value of 1.2 or more with elongation of 30% or more by a uniaxial tensile test.

Stainless steel oil feeding pipe

A new austenitic stainless steel containing approximately 0.1-1.0 mass % of Si and not more than approximately 0.003 mass % of Al. Nonmetallic inclusions dispersed in a steel matrix are converted to MnO&mdash;SiO &mdash;Al O containing not less than approximately 15 mass % of SiO and not more than approximately 40 mass % of Al O . During steel making, molten steel is covered with basic slag and heavily deoxidized with a Si alloy whose Al content is controlled to not more than approximately 1.0 mass % in a vacuum or non-oxidizing atmosphere. The austenitic stainless steel sheet can be formed to an objective shape without the occurrence of cracking due to its decrease in susceptibility to cracking and its good formability.

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Shinnanyo, Japan

Satoshi Suzuki