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

This high strength cold rolled steel sheet include a predetermined chemical composition wherein a microstructure at a 1/4 positon in a thickness direction from a surface includes, by volume%, a tempered martensite of 70.0% or more, a residual austenite of more than 3.0% and less than 10.0%, a total of a ferrite and a bainite of 25.0% or less, and a martensite of 5.0% or less, a microstructure at 25 [mu]m in the thickness direction from the surface, includes by volume%, a total of the ferrite and the bainite of 70% or more, and a total of the martensite and the tempered martensite of 30% or less, and at 25 [mu]m in the thickness direction from the surface, an average grain diameter of the martensite and the tempered martensite is 5.0 [mu]m or less, a tensile strength is 1310 MPa or more, an uniform elongation is 5.0% or more, a R/t, which is a ratio of limiting bend radius R and sheet thickness t, is 5.0 or less.

High-strength cold rolled steel sheet and manufacturing method thereof

PROBLEM TO BE SOLVED: To provide: a high-strength cold-rolled steel sheet excellent in local deformability such as bending, stretch-flanging and burring; and a method for manufacturing the same.SOLUTION: The high-strength cold-rolled steel sheet excellent in local deformability includes 0.002-0.20% of C, 0.001-2.5% of Si, 0.001-4.0% of Mn, 0.001-0.15% of P, 0.0005-0.03% of S, 0.001-2.0% of Al, 0.0005-0.01% of N, and 0.0005-0.01% of O. In the steel sheet, the area ratio of bainite in the metal structure is 95% or more, an average of X-ray random intensity ratios in the orientation group of {100} to {223} in the sheet face at least in a 5/8 to 3/8 sheet thickness from the surface of the steel sheet in the texture of the steel sheet is less than 4.0 and an X-ray random intensity ratio in a crystal orientation of {332} is 5.0 or less, and the volume-average as a unit size of a grain is 7 μm or less.

High-strength cold-rolled steel sheet excellent in local deformability and method for manufacturing the same

Steel sheets containing residual austenite of not more than 7 vol. %, crystallized and/or precipitated compounds with particle diameters of 0.01 to 5.0 μm of 100 to 100000 particle/mm2 and C of 0.05 to 0.3 mass %, Si of not more than 3.0 mass %, Mn of 0.01 to 3.0 mass %, P of not more than 0.02 mass %, S of not more than 0.02 mass %, Al of 0.01 to 3.0 mass %, N of not more than 0.01 mass % and Mg of 0.0002 to 0.01 mass %, with the remainder comprising iron and unavoidable impurities.

High-strength steel sheets with excellent resistance to delayed fracture after forming, method for manufacturing the same, and high-strength automotive part manufactured of the same

Hochfestes feuerverzinktes galvanisiertes stahlblech und feuerverzinktes geglühtes stahlblech mit ermüdungsfestigkeit,korrosionsbeständigkeit,duktilität und plattierungshaftung,nach starker verformung und verfahren zu dessen herstellung

PROBLEM TO BE SOLVED: To provide a welded steel tube having excellent workability and uniformity including a welded area. SOLUTION: In the method for manufacturing the welded steel tube having excellent workability, a welded steel tube prepared by means of welding in a tube-axis direction is subjected, after welding, to reheating treatment, such as normalizing or solid solution heat treatment, where the weld zone including heat affected zone is held at a temperature not lower than the Ac3 transformation point of the material for >=1 s and inversely transformed and successively cooled to form the structure of the weld zone into recrystallized structure with respect to as-welded structure and then the steel tube is subjected to reheat treatment such as solution heat treatment and then subjected, in a tension- applied state, to diameter-reduction deformation at a temperature as high as >=500 deg.C. A steel sheet having >=1.0 average r-value and >=0.2 n-value can be used as a stock. As diameter-reduction rolling conditions, rolling finishing temperature and reduction of area are made to a value not higher than the Ac3 transformation point and >=40%, respectively.

Nobuhiro Fujita

Papers

High-strength cold rolled steel sheet and manufacturing method thereof

High-strength cold-rolled steel sheet excellent in local deformability and method for manufacturing the same

High-strength steel sheets with excellent resistance to delayed fracture after forming, method for manufacturing the same, and high-strength automotive part manufactured of the same

Hochfestes feuerverzinktes galvanisiertes stahlblech und feuerverzinktes geglühtes stahlblech mit ermüdungsfestigkeit,korrosionsbeständigkeit,duktilität und plattierungshaftung,nach starker verformung und verfahren zu dessen herstellung

Method for manufacturing welded steel tube having excellent workability, and welded steel tube