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

Influence of Microstructure on Ductile Damage Behavior of Dual Phase Steel

PROBLEM TO BE SOLVED: To provide a high strength, high ductility steel sheet in which the weldablity and hole expansibility of a high strength steel sheet having a tensile strength of ≥800 MPa are simultaneously improved, and to provide a production method therefor. SOLUTION: The high strength steel sheet having excellent weldability and hole expansibility has a composition containing, by mass, 0.01 to 0.20% C, 0.01 to 2.5% Si, 0.01 to 3% Mn, 0.0010 to 0.1% P, 0.0010 to 0.05% S,, and 0.005 to 2% Al, and further containing one or two kinds selected from 0.01 to 5.0% Mo and 0.001 to 1.0% Nb in the ranges so as to saatisfy the following inequality (A), and the balance Fe with inevitable impurities, and has a microstructure containing bainite or bainitic ferrite by ≥70% in an area ratio, and has a tensile strength of ≥800 MPa, and the production method uses the same high strength steel sheet: (3.0Nb+2.5Mo+1/10Si+Mn)-(2C 0.5 +2)>0 (A). COPYRIGHT: (C)2003,JPO

High strength steel sheet having excellent weldability and hole expansibility and production method therefor

A hot-dip galvanized steel sheet includes a steel sheet and a hot-dip galvanized layer arranged on the steel sheet, in which the Si content and the Al content by mass% of components of the steel sheet satisfy a relationship 0.5<Si+Al<1.0, and a metallographic structure of the steel sheet satisfies a relationship of {(n 2 ) 2/3 ×d 2 }/{(n 1 ) 2/3 ×d 1 }×ln(H 2 /H 1 )<0.3 when the n 1 is the number of a MnS of a surface portion of the steel sheet, the d 1 µm is an average equivalent circle diameter of the MnS in the surface portion of the steel sheet, the H 1 GPa is a hardness of a martensite of the surface portion of the steel sheet, the n 2 is the number of the MnS of a center portion of the steel sheet, the d 2 µm is an average equivalent circle diameter of the MnS in the center portion of the steel sheet, and the H 2 GPa is the hardness of the martensite of the center portion of the steel sheet.

Hot-dip zinc-plated steel sheet and process for production thereof

The high-strength steel sheet includes, by mass %: C: 0.01% to 0.10%; Si: 0.15% or less; Mn: 0.80% to 1.80%; P: 0.10% or less; S: 0.015% or less; Al: 0.10% to 0.80%; Cr: 0.01% to 1.50%; N: 0.0100% or less; and a balance consisting of iron and inevitable impurities, in which a metallic structure is composed of ferrite and a hard second phase, the area fraction of the ferrite is 80% or more, the area fraction of the hard second phase is 1% to 20%, the fraction of unrecrystallized ferrite in the ferrite is less than 10%, the ferrite grain sizes are 5 μm to 20 μm, and the fraction of the ferrite crystal grains having an aspect ratio of 1.2 or less in the entire ferrite crystal grains is 60% or more.

High-strength steel sheet having excellent processability and paint bake hardenability, and method for producing of high-strength steel sheet

High-strength parts and a method for producing them can be provided, where such parts exhibit hydrogen embrittlement resistance and strength after high-temperature forming. For example, the atmosphere in a heating furnace can contain less than about 10% hydrogen and/or have a dew point of about 30° C. or less. The amount of hydrogen penetrating a steel sheet during heating can thereby be reduced. After forming, quench hardening in a die assembly and post-working can be performed. Post-working can include shearing followed by re-shearing or compression forming; punching with a cutting blade having a continuously reduced base width; punching with a tool having a curved blade and a protrusion at the tip of the cutting blade, where the curved blade may include a shoulder portion of given radius and/or angle; fusion cutting; etc. Tensile residual stresses after punching can be reduced and resistance to hydrogen embrittlement can be improved.

Nobuhiro Fujita

Papers

Influence of Microstructure on Ductile Damage Behavior of Dual Phase Steel

High strength steel sheet having excellent weldability and hole expansibility and production method therefor

Hot-dip zinc-plated steel sheet and process for production thereof

High-strength steel sheet having excellent processability and paint bake hardenability, and method for producing of high-strength steel sheet

High strength part and method for producing the same