Improvement of toughness and strength balance in low-carbon steel bars with cube texture processed by warm bi-axial rolling

Abstract

Abstract A novel rolling process characterized by multi-pass bi-axial reduction was proposed. An 800\u202fMPa class low-carbon steel bar with ultrafine elongated-grain structures was fabricated using bi-axial rolling at a warm working temperature, and tensile and three-point bending tests were conducted at a temperature range from 77\u202fK to 473\u202fK. The texture in the developed steel bar was dominated by {0\u202f0\u202f1}〈0\u202f0\u202f1〉 cube orientations. The toughness–strength balance of the developed steel was remarkably improved compared with that of conventional 0.15%C ferrite–pearlite steel and 0.29%C martensitic steel. The toughness reached its maximum when crack branching started to appear upon decreasing the test temperature, and the specimen did not separate into two pieces even at low temperature of 77\u202fK. A microstructural design that improves toughness in steel was demonstrated.