This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Recent developments in stainless steels

The present invention provides a heterocyclic compound and an organic light-emitting device including the heterocyclic compound. The organic light-emitting devices using the heterocyclic compounds have high-efficiency, low driving voltage, high luminance and long lifespan.

Organic light-emitting device

Gibbs-Thomson effects in phase transformations

A new model for the evolution of the precipitate structure derived by means of application of the thermodynamic extremum principle is presented. The model describes the evolution of the radii and of the chemical composition of individual precipitates of different phases in the multi-component system. In connection with a proper theory of nucleation, the model is able to describe the evolution of the precipitate structure in the classical stages of nucleation, growth and coarsening as well as interaction of precipitates of different phases, of different chemical composition and of different sizes via diffusion in the matrix.

Modelling of kinetics in multi-component multi-phase systems with spherical precipitates I. – Theory

Development of high strength ferritic steel for interconnect application in SOFCs

A steel sheet including, by mass%, C: more than 0.100% and 0.500% or less, Si: 0.0001% or more and less than 0.20%, Mn: more than 0.20% and 0.50% or less, Al: 3.0% or more and 10.0% or less, N: 0.0030% or more and 0.0100% or less, Ti: more than 0.100% and 1.000% or less, P: 0.00001 % or more and 0.0200% or less, S: 0.00001% or more and 0.0100% or less, and a remainder including Fe and impurities, in which a sum of a C content and a Ti content satisfies 0.200<C+Ti≤1.500 by mass%, a product of an Al content and an Si content satisfies Al×Si≤0.8 by mass%, and a specific gravity is 5.5 to less than 7.5.

High-strength, low-specific gravity steel plate having excellent spot welding properties

A steel sheet including, by mass %, C: more than 0.100% and 0.500% or less, Si: 0.0001% or more and less than 0.20%, Mn: more than 0.20% and 0.50% or less, Al: 3.0% or more and 10.0% or less, N: 0.0030% or more and 0.0100% or less, Ti: more than 0.100% and 1.000% or less, P: 0.00001% or more and 0.0200% or less, S: 0.00001% or more and 0.0100% or less, and a remainder including Fe and impurities, in which a sum of a C content and a Ti content satisfies 0.200<C+Ti≦1.500 by mass %, a product of an Al content and an Si content satisfies Al×Si≦0.8 by mass %, and a specific gravity is 5.5 to less than 7.5.

High-strength low-specific-gravity steel sheet having superior spot weldability

This galvanized steel sheet comprises a steel sheet and a galvanized layer on the surface of the steel sheet. The chemical composition of the steel sheet, in mass%, is: more than 0.100% but no more than 0.500% C; at least 0.0001% but less than 0.20% Si; more than 0.20% but no more than 3.00% Mn; 3.0%-10.0% Al; 0.0030%-0.0100% N; more than 0.100% but no more than 1.000% Ti; 0.00001%-0.0200% P; and 0.00001%-0.0100% S; with the remainder being Fe and unavoidable impurities. The galvanized layer contains as chemical components thereof, in mass%, 0.01%-15% Fe, with the remainder being Zn and unavoidable impurities, and has a specific gravity of at least 5.5 but less than 7.5.

Galvanized steel sheet and method for producing the same

PROBLEM TO BE SOLVED: To provide a hot pressing method by which resistance to hydrogen embrittlement is improved in formed parts for which the hot pressing process of a steel sheet having the tensile strength of ≥980 MPa is used. SOLUTION: A dew point inside a heating furnace just before pressing in the hot pressing process is set to -100 to 30°C, the component of the atmosphere inside an annealing furnace is essentially composed of nitrogen or argon, the concentration of hydrogen is set to ≤5 mol%, and the steel sheet is heated to 650-1,000°C, and then press forming is performed. COPYRIGHT: (C)2006,JPO&NCIPI

Hot pressing method for high strength steel sheet having excellent resistance to hydrogen embrittlement

PROBLEM TO BE SOLVED: To provide a high-strength cold-rolled steel sheet excellent in homogeneous deformability and local deformability achieved by ensuring uniform elongation by the control of a texture fraction, improving local ductility of the high-strength steel sheet with the texture, and improving anisotropy within the steel sheet, and to provide a method for producing the same.SOLUTION: The high-strength cold-rolled steel sheet excellent in homogeneous deformability and local deformability comprises: 0.01-0.4% C, 0.001-2.5% Si, 0.001-4.0% Mn, 0.001-0.15% P, 0.0005-0.03% S, 0.001-2.0% Al, 0.0005-0.01% N, and 0.0005-0.01% O. In the texture of the steel sheet, the average of the X-ray random intensity ratios of the orientation group {112} to {113} and of crystal orientation of {112} on the surface of the steel sheet at the portion ranging from the surface of the steel sheet in a depth of 5/8-3/8 of the sheet thickness is 5.0 or less, the X-ray random intensity ratio of the crystal orientation {001} is 4.0 or less, the r value (rC) in the direction rectangular to the rolling direction is 0.70 or more, and the r value (r30) at 30° with respect to the rolling direction is 1.10 or less. The steel sheet contains, by an area ratio of the steel sheet texture, 50% or more in a total of ferrite and bainite and 1-50% of martensite.

Nobuhiro Fujita

Papers

High-strength, low-specific gravity steel plate having excellent spot welding properties

High-strength low-specific-gravity steel sheet having superior spot weldability

Galvanized steel sheet and method for producing the same

Hot pressing method for high strength steel sheet having excellent resistance to hydrogen embrittlement

High-strength cold-rolled steel sheet excellent in homogeneous deformability and local deformability