Preface to the Special Issue on “Recent Progress in Inclusion/ Precipitate Engineering”

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Inclusion/ precipitate particle behaviors in liquid steel and solid steel influence strongly both the cleanliness and the material properties such as the toughness of the steel materials, and consequently their controls are crucially important. These fundamental techniques have traditionally been called “Clean Steel Technology” and “Oxide Metallurgy” respectively, and they have been utilized in practice. So far, the directions of these two researches have been partially overlapped, or remarkably evolved through their combination. As a result, they collectively have been referred to as “Inclusion/Precipitate Engineering”. It is highly expected to discuss the present states of the prediction methods and control techniques using thermodynamics and growth kinetics with regard to the composition, the formation amount, and the size of various inclusions/ precipitates in high alloy steels as well as carbon steels.

In this special issue, with the aim of enhancing activities in the field of “Inclusion/ Precipitate Engineering”, the latest researches and review papers were widely invited. In addition to the general open call for papers, excellent papers were going to be chosen from those presented at “The International Conference on Inclusion/ Precipitate Engineering in Steels (IPES2020)” co-supported by the ISIJ, which was scheduled on June 11–12th, 2020 in Stockholm, with the cooperation of the organizing committee. Although IPES 2020 was postponed due to the global spread of the new coronavirus (COVID-19), the invitations to authors who were planning to attend the conference, had continued in the schedule. Furthermore, authors in “Refining of Cr steel by slag and inclusion control” research group of ISIJ, which focused on steels with high content of chromium to produce special steels such as stainless steels, heat resistant steels, high tensile-strength steels, and tool steels, and so on, were also invited. Accordingly, this special issue includes the latest researches within the following fields:

1) fundamentals of high temperature processes relevant to the formation of various inclusions,

2) methods for predicting the composition, the formation amount and the size of various inclusions/ precipitates, and

3) control techniques based on them, e.g., the related thermodynamics, growth kinetics, dissolution from refractory, inclusion/ precipitate particle behavior in refining, casting, and machining processes, assessment techniques, and physical properties of slags and fluxes, etc.

This special issue will serve to find out the potential directions for the future progresses and applications of “Inclusion/ Precipitate Engineering”. Finally, I would like to express my gratitude to all the authors for their contributions, and to the entire editorial staff who supported the publication of this special issue. I am also indebted to Prof. Keiji Nakajima of KTH Royal Institute of Technology and Prof. Takahiro Miki of Tohoku University for their cooperation in publishing this special issue.