Improvement of impact toughness of simulated heat affected zone by addition of aluminium

Abstract

The effect of aluminium content (0·023, 0·038 and 0·070 wt-%) on microstructure and impact toughness of simulated coarse grained heat affected zone (CGHAZ) of high strength low alloy steels with different heat inputs (20, 100 and 200 kJ cm⁻¹) was investigated. The microstructure of simulated CGHAZ consisted of predominantly granular bainite. The martensite–austenite constituents became finer and its volume fraction decreased with increasing aluminium content, irrespective of heat input level. The impact toughness of the simulated CGHAZ improved remarkably with increasing aluminium content even at high heat input of 200 kJ cm⁻¹. It was attributed to the reduction in volume fraction of martensite–austenite constituents and the refined martensite–austenite constituents by addition of appropriate aluminium.

Keywords:

• High strength low alloy steel
• Coarse grained heat affected zone
• High heat input welding
• Impact toughness
• Martensite–austenite constituent

Acknowledgements

The authors express their thanks to the financial support from the International Science and Technology Cooperation Program of China under grant no. S2012ZR0211 and from Hubei Provincial Department of Science and Technology under grant no. 2012BAA14005.