Speaker
Description
Abstract
Drop Weight Tear Test (DWTT) performance is a critical indicator of fracture resistance in high-strength pipeline steels, directly reflecting the ability to resist brittle crack propagation. In thermo-mechanical controlled processing (TMCP) of API X70 plates, achieving consistently high DWTT shear values under industrial conditions remains a significant challenge due to variations in microstructure and process parameters.
This study presents an industrial investigation of DWTT performance in API X70 plates produced in a 4900 mm heavy plate mill. The work focuses on the relationship between microstructure evolution and fracture behavior, with particular emphasis on grain refinement, phase distribution, and steel cleanliness.
An integrated optimization approach was implemented, combining controlled alloy design, Ti/N ratio management for effective grain boundary pinning, improved inclusion control, and optimized rolling and accelerated cooling conditions. These measures promote a fine ferritic–bainitic microstructure while minimizing brittle constituents that can initiate cleavage fracture.
Industrial validation demonstrates that the optimized process achieves DWTT shear values above 95% at −20°C with stable mechanical properties. The results confirm that consistent fracture resistance in TMCP plates can be achieved through coordinated control of metallurgical design and process parameters.
This study highlights the critical role of microstructure engineering in fracture performance and provides a practical framework for achieving reliable DWTT performance in industrial plate production.