Yuan Z.-H.,University of Science and Technology Beijing |
Wang F.-M.,University of Science and Technology Beijing |
Qin R.-Z.,University of Science and Technology Beijing |
Wei S.-L.,Hebei Jinxi Iron and Steel Group Co Ltd |
Ye G.-Q.,Hebei Jinxi Iron and Steel Group Co Ltd
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2013
In order to make use of chromium originated from the low-cost ore, the contents of C and Mn were reduced and Cr was added based on the chemical composition of Q345 steel. The dynamic continuous cooling transformation (CCT) curves of four low-alloy structural steels with different contents of Cr were obtained by DSC analysis and dilatometric method combining with metallographic test and hardness measurement. The results show that with the increase of Cr content, the hardness of the steel greatly increases. Chromium may retard the pro-eutectoid ferrite formation of super-cooled austenite and broaden the transformation region of bainite. Compared to the original Q345 steel, the steel with the adjusted composition (C and Mn reduced and Cr added) may have a higher critical cooling velocity (0.5°C/s) of F+P, the two-phase structure formation. Therefore, a higher cooling rate may be applied in the actual process of steel making to improve productivity.
Yuan Z.,University of Science and Technology Beijing |
Wang F.,University of Science and Technology Beijing |
Wei S.,Hebei Jinxi Iron and Steel Group Co. |
Ye G.,Hebei Jinxi Iron and Steel Group Co.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2014
Based on the chemical composition of Q345 steel, the tested steel with different Cr contents (0.36%, 0.55% and 0.70%, mass fraction) was designed and made. Effect of Cr content on the CGHAZ of the low alloy structural steel was studied by the method of thermal simulation. The results show that the microstructure of the steel is bainite after thermal simulation. The grain is coarsened dramatically, and the finer and longer lath bainite formed directionally in the specimen with 0.70% Cr, that make the toughness of the steel worse. With Cr content increasing, the impact absorbing energy decreases, and both the percentage of crystallinity of fracture and the hardness increases. In considerationof of welding performance, the content of Cr should be controlled in about 0.55%.