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

In the present study, the effects of inclusions on the local ductility of DP steel are investigated using finite element analysis (FEA). In order to evaluate local ductility, a continuum damage mechanics (CDM) model has been incorporated into the Abaqus/Explicit® commercial finite element code. Furthermore, three-dimensional representative volume elements (RVEs) with ferrite, martensite, and inclusion phases have been used to evaluate the stress-strain response. Simulation results show that the volume fraction of the martensite as well as the difference in hardness between the ferrite and the martensite phases dominates the effect of inclusions on local ductility.

Evaluation of the Effects of Inclusion Distribution on the Local Ductility of DP Steel

PROBLEM TO BE SOLVED: To provide a high strength steel pipe excellent in formability in hydroforming, or the like. SOLUTION: This good workability high strength steel pipe has a composition containing, by mass, 0.0005 to 0.30% C, 0.001 to 2.0% Si, 0.01 to 3.0% Mn, 0.0001 to 0.0050% S, 0.0001 to 0.0040% O and 0.0001 to 0.030% N, and, if required, containing other elements, and the balance iron with inevitable impurities, in which the area ratio of nonmetallic inclusions with an aspect ratio (the length parallel to the rolling direction/the length vertical to the rolling direction (parallel to the sheet thickness direction)) of >=2 is <=0.05%, and also, the area ratio of nonmetallic inclusions with an aspect ratio of <2 is <=0.03%.

Good workability high strength steel pipe and its production method

Steel plate and tube exhibiting excellent workability and method for producing the same

PROBLEM TO BE SOLVED: To produce high strength steel excellent in endless rollability and formability. SOLUTION: This extra-low carbon steel contains, by mass, N/14, moreover contains either or both of Ti and Nb so as to satisfy (Ti/48+Nb/93)>(C/12+N /14+S/32)} and additionally contains Mg of >=0.0003% also so as to satisfy 0.1<=Mg/O<=2.3, and the balance Fe with inevitable impurities. If required, 0.0003 to 0.002% B is contained as well.

Extra-low carbon steel excellent in endless rollability and formability

PROBLEM TO BE SOLVED: To provide a steel pipe resistant to severe molding such as hydroforming and superior in molding property. SOLUTION: The shape and quality of a weld of a welded steel pipe are controlled to set a n-value and a r-value showing plastic deformability at characteristic ranges. For this purpose, the average r-value and shape of a raw plate and a temperature for reheating treatment after pipe formation are specified in specific ranges.

Nobuhiro Fujita

Papers

Evaluation of the Effects of Inclusion Distribution on the Local Ductility of DP Steel

Good workability high strength steel pipe and its production method

Steel plate and tube exhibiting excellent workability and method for producing the same

Extra-low carbon steel excellent in endless rollability and formability

Welded steel pipe superior in molding property and its manufacturing method