Disclosed is a high-strength steel sheet having excellent processability and a tensile strength of 980 MPa or more. The high-strength steel sheet has the following composition (in mass%): C: 0.1 to 0.3% inclusive, Si: 2.0% or less, Mn: 0.5 to 3.0% inclusive, P: 0.1% or less, S: 0.07% or less, Al: 1.0% or less, and N: 0.008% or less, with the remainder being Fe and unavoidable impurities. The steel structure of the high-strength steel sheet comprises 50% or more of martensite, 50% or less (including 0%) of ferrite, 10% or less (including 0%) of bainite, and 10% or less (including 0%) of residual austenite. In the high-strength steel sheet, the half width in the degree distribution of the nano-hardness obtained by the measurement of the hardness distribution of the martensite is 2.0 GPa or more, and the steel sheet has a tensile strength of 980 MPa or more.

High strength steel sheet and method for manufacturing the same

Nonmetallic (based on polymers or oxides) and metallic protective coatings are used to protect metal products against the harmful action of the corrosion environment. In recent years, self-healing coatings have been the subject of increasing interest. The ability of such coatings to self-repair local damage caused by external factors is a major factor contributing to their attractiveness. Polymer layers, silica-organic layers, conversion layers, metallic layers and ceramic layers, to mention but a few, are used as self-healing coatings. This paper presents the main kinds of self-healing coatings and explains their self-healing mechanisms.

https://link.springer.com/content/pdf/10.1007%2Fs10853-013-7616-y.pdf

Self-healing coatings in anti-corrosion applications

Disclosed are an ultra-high-strength steel sheet having both a tensile strength of as high as 1400MPa or above and excellent formability and an advantageous process for manufacturing the same. A high-strength steel sheet having both a composition which contains by mass C: 0.12 to 0.50%, Si: 2.0% or less, Mn: 1.0 to 5.0%, P: 0.1% or less, S: 0.07% or less, Al: 1.0% or less, and N: 0.008% or less with the balance being Fe and unavoidable impurities, and a structure which comprises, in terms of area fraction, autotempered martensite: 80% or more, ferrite: less than 5%, bainite: 10% or less, and retained austenite: 5% or less and in which the average number of precipitated iron carbide particles of 5nm to 0.5[mu]m in the autotempered martensite is 5OE04 or above per mm2.

High-strength steel sheet and process for production thereof

The direct electrodeposition of electroactive conducting polymers on active metals such as iron and aluminum is complicated by the concomitant metal oxidation that occurs at the positive potentials required for polymer formation. In the case of aluminum and its alloys, the oxide layer that forms is an insulator that blocks electron transfer and impedes polymer formation and deposition. As a result, only patchy nonuniform polymer films are obtained. Electron transfer mediation is a well-known technique for overcoming kinetic limitations of electron transfer at metal electrodes. In this work, we report the use of electron transfer mediation for the direct electrodeposition of polypyrrole onto aluminum and onto Al 2024-T3 alloy. This report focuses on the use of Tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt) as the mediator, although catechol appears to function in a similar manner. Depositions were carried out under galvanostatic conditions at current densities of The mediator reduced the deposition potential by nearly 500 mV compared to deposition performed in the absence of mediator (where Tiron was replaced by p-toluene sulfonic acid sodium salt). Polypyrrole formation and deposition appears to occur with 100% current efficiency and uniform films are obtained. Results of the characterization of these films by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, conductivity measurements, and adhesion measurements are presented. © 2002 The Electrochemical Society. All rights reserved.

Direct Electrodeposition of Polypyrrole on Aluminum and Aluminum Alloy by Electron Transfer Mediation

pH-controlled self-healing polymer coatings with cellulose nanofibers providing an effective release of corrosion inhibitor

Disclosed is a high strength steel sheet having excellent hydrogen embrittlement resistance. The steel sheet has a tensile strength of 1180 MPa or more, and satisfies the following conditions: with respect to an entire metallographic structure thereof, bainite, bainitic ferrite and tempered martensite account for 85 area % or more in total; retained austenite accounts for 1 area % or more; and fresh martensite accounts for 5 area % or less (including 0 area %).

High-strength steel sheet having excellent hydrogen embrittlement resistance

PROBLEM TO BE SOLVED: To provide an ultrahigh-strength steel sheet superior in hydrogen-embrittlement resistance. SOLUTION: The ultrahigh-strength steel sheet superior in hydrogen-embrittlement resistance comprises, by mass%, 0.10-0.25% C, 1.0-3.0% Si, 1.0-3.5% Mn, 0.15% or less P, 0.02% or less S, 1.5% or less (excluding 0%) Al, 1.0% or less (excluding 0%) Mo, 0.1% or less (excluding 0%) Nb and the balance iron with unavoidable impurities; has a metallurgical structure in which retained austenite occupies 1% or more, bainitic ferrite and martensite occupy 80% or more in total, and ferrite and pearlite occupy 9% or less (including 0%) in total by an area rate with respect to the total structure, and in which crystal grains of the retained austenite have an average axial ratio (major axis/minor axis) of 5 or higher; and has further a tensile strength of 1,180 MPa or higher. COPYRIGHT: (C)2006,JPO&NCIPI

Ultrahigh-strength steel sheet superior in hydrogen-embrittlement resistance

Provided are the following cold-rolled steel sheets: 1) a cold-rolled steel sheet having higher stretch flangeability than conventional steels; 2) a cold-rolled steel sheet having a higher balance between elongation and stretch flangeability than conventional steels; and 3) a cold-rolled steel sheet heightened in all of yield stress, elongation, and stretch flangeability. The cold-rolled steel sheets are characterized by containing 0.03-0.30 mass % carbon, up to 3.0 mass % (including 0 mass %) silicon, 0.1-5.0 mass % manganese, up to 0.1 mass % phosphorus, less than 0.01 mass % sulfur, up to 0.01 mass % nitrogen, and 0.01-1.00 mass % aluminum and having a structure which comprises tempered martensite in an amount of 50% or more (including 100%) in terms of areal proportion and in which the remainder is ferrite. The steel sheets are further characterized in that at least one of the following structural factors has been regulated: the proportions of cementite particles and of the ferrite grains in the tempered martensite and the dislocation density in all structures.

Cold-rolled steel sheet

The purpose of the present invention is to provide a high strength thin steel sheet that has high hydrogen embrittlement resisting property. In order to achieve the above purpose, a high strength thin steel sheet having high hydrogen embrittlement resisting property comprises: C: 0.10 to 0.25%; Si: 1.0 to 3.0%; Mn: 1.0 to 3.5%; P: 0.15% or less; S: 0.02% or less; and Al: 1.5% or less (higher than 0%) in terms of percentage by weight, with balance of iron and inevitable impurities; and the metal structure comprises: residual austenite; 1% by area or more in proportion to the entire structure; bainitic ferrite and martensite: 80% or more in total; and ferrite and pearlite: 9% or less (may be 0%) in total, while the mean axis ratio (major axis/minor axis) of said residual austenite grains is 5 or higher, and the steel has tensile strength of 1180 MPa or higher.

High strength thin steel sheet having high hydrogen embrittlement resisting property

The invention relates to an ultrahigh-strength thin steel sheet excellent in the hydrogen embrittlement resistance, the steel sheet including, by weight %, 0.10 to 0.60% of C, 1.0 to 3.0% of Si, 1.0 to 3.5% of Mn, 0.15% or less of P, 0.02% or less of S, 1.5% or less of Al, 0.003 to 2.0% of Cr, and a balance including iron and inevitable impurities; in which grains of residual austenite have an average axis ratio (major axis/minor axis) of 5 or more, the grains of the residual austenite have an average minor axis length of 1 μm or less, and the grains of the residual austenite have a nearest-neighbor distance between the grains of 1 μm or less.

Junichiro Kinugasa

Papers

High-strength steel sheet having excellent hydrogen embrittlement resistance

Ultrahigh-strength steel sheet superior in hydrogen-embrittlement resistance

Cold-rolled steel sheet

High strength thin steel sheet having high hydrogen embrittlement resisting property

Ultrahigh-strength thin steel sheet