Abstract
Recently there has been a renewed interest in the addition of zirconium to microalloyed steels. It has been used since the early 1920s, but has never been universally employed, as have niobium, titanium or vanadium. The functions of zirconium in steelmaking are associated with a strong chemical affinity, in decreasing order, for oxygen, nitrogen, sulphur and carbon. Historically, the main use of additions of zirconium to steel was for combination preferentially with sulphur, to avoid the formation of manganese sulphide, known to have a deleterious influence of the impact toughness of wrought and welded steel. Modern steelmaking techniques have also raised the possibility that zirconium additions can reduce the austenite grain size and increase dispersion strengthening, due to precipitation of zirconium carbonitrides, or in high nitrogen vanadium–zirconium steels, vanadium nitride. This review gathers information on the compounds of zirconium identified in steels together with crystallographic data and solubility equations. Also brief accounts of the role of sulphides and particles in general on austenite grain size control and toughness are included.
Acknowledgements
The author wishes to thank Dr W. B. Morrison, formerly of British Steels and Corus, for introducing him to zirconium microalloyed steels and then supporting several pieces of research in this area, Dr David Crowther, formerly of Corus (now Tata Steel), for his support and Mr Peter Mitchell, formerly of Vanitec, who supported financially the DCTS research, and all three for many useful and enjoyable discussions. Also, Dr Michael Arrowsmith is thanked for providing information from his selected area electron diffraction work on zirconium compounds which he identified in steels, and Aileen Petrie for her patience in re-editing the figures and tables.