Developments and optimisation of high strenght boron treated steels through the application of advanced boron monitoring techniques developments and optimisation of high strength boron treated steels through the application of advanced boron monitoring techniques
The present work is directed to high (>600MPa) and ultrahigh-strength (>900MPa) boron treated plate/strip and cold rolled and annealed sheet steels.
Boron is a widely used alloying element in the production of high strength steels and is commonly added on account of its dramatic effect in improving hardenability thereby allowing bainitic or martensitic microstructures to be obtained using lower levels of alloying elements such as Mn, Cr and Mo.
Although a lot of past research exists on B-steels, many questions remain and need clarification and this project aims at obtaining a better understanding of the behaviour of boron, through the use of advanced detection techniques and electron microscopy.
The main objectives of present work are:
1) to investigate the efficiency of available state of the art characterisation techniques to monitor B in its different forms (free B, precipitated, segregated), to define guidelines about capabilities and detection limits and to adapt laboratory methodologies to B-rich species.
2) helped by these improved detection techniques, to progress in the understanding of B interactions with other additions (AlN versus BN and competition between different carbide species in Nb, V and Mo added grades) in order to improve consistency of properties in quenched (and tempered) high and ultrahigh strength plate/strip.
3) to compare direct quenching versus air cooling plus subsequent Q&T treatment as a precursor for the elimination of a costly and energy consuming reheating treatment after hot rolling, with a particular focus on optimum boron protection methods for each route and control of recrystallisation in hot rolling.
4) to explore the applicability of B in conjunction with other alloying elements (Mn, Cu+Ni) for a consistent production of multi phase cold rolled and annealed strip combining high strength, abrasion resistance, formability and weldability at a reduced cost with respect to present DP and TRIP steel grades.
5) To test the sensitivity of current precipitation and phase transformation models and to incorporate B effects into existing models for recrystallization that already include Nb, Ti and Mo.
Tata Steel UK Limited (Tata Steel)
Centre de Recherches Métallurgiques (CRM)
Onderzoekscentrum voor Aanwending van Staal (OCAS)
NEW DEVELOPMENTS AND OPTIMISATION OF HIGH STRENGTH BORON TREATED STEELS THROUGH THE APPLICATION OF ADVANCED BORON MONITORING TECHNIQUES