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 steel sheet having a tensile strength of ≥980 MPa, having high workability and formability, and further having improved delayed fracture properties caused by hydrogen embrittlement, to provide an automobile member obtained by using the same, and to provide a production method therefor. SOLUTION: The steel sheet for a hot pressing excellent in hydrogen embrittlement resistance has a composition comprising 0.01 to 0.40% C, ≤2.0% Si, 0.01 to 3.5% Mn, ≤0.1% P, ≤0.05% S, 0.005 to 4% Al and ≤0.01% N, and comprising one or more kinds selected from the elemental group consisting of Nb, V, Cr, Ti and Mo in an amount of 0.001 to 3% in total, and the balance Fe with inevitable impurities, has a microstructure where martensite is a phase maximum in an area ratio, and has a tensile strength of ≥980 MPa. COPYRIGHT: (C)2005,JPO&NCIPI

Steel sheet for hot press having hydrogen embrittlement resistance, automobile member and its production method

Bainite is of considerable importance in the design of high strength steels. There are two types of morphologies, upper and lower bainite. In upper bainite, cementite forms between adjacent bainitic ferrite plates. In certain steels, however, the cementite reaction is suppressed so that carbon-enriched austenite remains untransformed between bainitic ferrite plates. In lower bainite, cementite also has the opportunity to precipitate within bainitic ferrite plates. In order to model the development of these microstructures, it is necessary to treat the simultaneous formation of both the ferritic and carbide components of the microstructure. A theory has been developed to do exactly this, enabling the estimation of the phase fractions, the cementite particle size and the transition from upper to lower bainite. The results have been compared against experimental data.

Modelling Upper and Lower Bainite Trasformation in Steels

A hot-rolled steel sheet according to the present invention is a steel sheet containing a predetermined components, and satisfying O < S/Ca < 0.8, N - 14/ 48 x Ti ≧ "0" (zero)%. It is a high-strength hot-rolled steel sheet for a spiral pipe excellent in low-temperature toughness in which a pro-eutectoid ferrite fraction is 3% or more and 20% or less, and the other is a low-temperature transformation phase in a microstructure at a depth of a half thickness of a sheet thickness from a steel sheet surface, a number average crystal grain size of a whole of the microstructure is 2.5 µm or less, an area average grain size is 9 µm or less, a standard deviation of the area average grain size is 2.3 µm or less, and a reflected X-ray intensity ratio {211}/ {111} in a {211} direction and in a {111} direction relative to a plane in parallel to the steel sheet surface at the depth of the half thickness of the sheet thickness from the steel sheet surface is 1.1 or more. The steel sheet has both high-toughness and strength of API5L-X80 standard or more.

Hot-rolled steel sheet and method for producing same

The present invention provides a steel pipe excellent in formability during hydraulic forming and the like and a method to produce the same, and more specifically: a steel pipe excellent in formability having an r-value of 1.4 or larger in the axial direction of the steel pipe, and the property that the average of the ratios of the X-ray intensity in the orientation component group of {110} to {332} on the plane at the center of the steel pipe wall thickness to the random X-ray intensity is 3.5 or larger, and/or the ratio of the X-ray intensity in the orientation component of {110} on the plane at the center of the steel pipe wall thickness to the random X-ray intensity is 5.0 or larger; and a method to produce a steel pipe excellent in formability characterized by heating the steel pipe having the property that the ratio of the X-ray intensity in every one of the orientation components of {001} , {116} , {114} and {112} on the plane at the center of the mother pipe wall thickness to the random X-ray intensity is 3 or smaller to a temperature in the range from 650 to 1,200° C. and by applying working under a condition of a diameter reduction ratio of 30% or more and a wall thickness reduction ratio of 5 to 30%.

Steel pipe having high formability and method for producing the same

A high-strength cold-rolled steel sheet includes, by mass%, C: 0.10% to 0.40%, Mn: 0.5% to 4.0%, Si: 0.005% to 2.5%, Al: 0.005% to 2.5%, Cr: 0% to 1.0%, and a balance of iron and inevitable impurities, in which an amount of P is limited to 0.05% or less, an amount of S is limited to 0.02% or less, an amount ofN is limited to 0.006% or less, the microstructure includes 2% to 30% of retained austenite by area percentage, martensite is limited to 20% or less by area percentage in the microstructure, an average particle size of cementite is 0.01 µm to 1 µm, and 30% to 100% of the cementite has an aspect ratio of 1 to 3.

Nobuhiro Fujita

Papers

Steel sheet for hot press having hydrogen embrittlement resistance, automobile member and its production method

Modelling Upper and Lower Bainite Trasformation in Steels

Hot-rolled steel sheet and method for producing same

Steel pipe having high formability and method for producing the same

High-strength cold-rolled steel sheet, and process for production thereof