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

PROBLEM TO BE SOLVED: To provide a high strength steel sheet which has a tensile strength of ≥1,180 MPa and has excellent delayed fracture resistance, and to provide its production method. SOLUTION: The high strength steel sheet having excellent delayed fracture resistance contains, by mass, 0.05 to 0.3% C, COPYRIGHT: (C)2005,JPO&NCIPI

High strength steel sheet having excellent delayed fracture resistance, and its production method

PROBLEM TO BE SOLVED: To provide a method for producing an aluminum plated steel sheet, a galvanized steel sheet or an aluminum-zinc plated steel sheet excellent in high temperature formability and hydrogen-brittleness resistance with which this steel sheet is used for a member, as a typical example, a structural member of car parts needed to the strength and produced with a high temperature press and after high temperature formation, the strength having ≥1200 MPa can be obtained. SOLUTION: The method for producing the steel sheet for hot press, is performed as the followings, by which in the case of annealing the steel sheet containing 0.1-0.5 mass% C, after annealing at 660°C-Ac 3 point under atmosphere having ≤15% hydrogen concentration and ≤0°C dew point, the plating mainly containing aluminum or zinc is applied and diffusible hydrogen in the steel is made to be ≤0.3 ppm. COPYRIGHT: (C)2006,JPO&NCIPI

Method for producing plated steel sheet for hot press

PROBLEM TO BE SOLVED: To provide a high strength steel sheet in which the weldability, hole expansibility and ductility 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, hole expansibility, and ductility, and having a tensile strength of ≥800 MPa has a microstructure containing bainite or bainitic ferrite as the main phase of 50 to 97% by an area fraction, and containing austenite as a second phase of 3 to 50% in total by an area fraction. COPYRIGHT: (C)2003,JPO

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

This is a cold-rolled steel sheet includes, by mass %, C: 0.02% to 0.4%, Si: 0.001% to 2.5%, Mn: 0.001% to 4.0%, and Al: 0.001% to 2.0%. The sum of the Si content and the Al content is 1.0% to 4.5%. An average pole density of an orientation group from {100} to {223} is 1.0 to 6.5, and a pole density of a crystal orientation {332} is 1.0 to 5.0. A microstructure includes, by an area ratio %, 5% to 80% of ferrite, 5% to 80% of bainite, and 2% to 30% of retained austenite. In the microstructure, by an area ratio %, martensite is limited to 20% or less, pearlite is limited to 10% or less, and tempered martensite is limited to 60% or less.

Cold-rolled steel sheet and production method thereof

This hot-rolled steel sheet has an average pole density for {100} to {223} orientations of 1.0-5.0, has a pole density for the crystal orientation {332} of 1.0-4.0, and has a metallographic structure which comprises, in terms of areal proportion, 30-99% ferrite and bainite and 1-70% martensite and which satisfies the following relationships (1) and (2) wherein fM is the areal proportion of the martensite in % by area, dia is the average size of the martensite in µm, dis is the average distance between martensite grains in µm, and TS is the tensile strength of the steel sheet in MPa. dia≤13 µm (relationship 1) TS/fM×dis/dia≥500 (relationship 2)

Nobuhiro Fujita

Papers

High strength steel sheet having excellent delayed fracture resistance, and its production method

Method for producing plated steel sheet for hot press

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

Cold-rolled steel sheet and production method thereof

Hot-rolled steel sheet and process for producing same