Austenite Grain Size Prediction in the Coarse-Grained Heat-Affected Zone of the Developed Cu-Free High-Strength Low-Allo
- PDF / 4,524,031 Bytes
- 12 Pages / 593.972 x 792 pts Page_size
- 14 Downloads / 135 Views
NTRODUCTION
HIGH strength is one of the main developing trends in hull structure steels. To develop a higher strength hull structure steel, Wang et al.[1] tried to design a new HSLA hull structure steel. The developed steel featured high strength (yield strength 870 MPa, tensile strength 890 MPa) and good low-temperature toughness (210 J at 50 °C). They preliminarily investigated the low-temperature toughness of simulated CGHAZ under low-medium heat input. Results showed that the impact toughness ( 50 °C) under heat inputs of 15, 30, and 50 kJ/cm were 156.2, 172.9, and 181.5 J, respectively. In further work, they studied the low-temperature toughness of simulated intercritically reheated CGHAZ (two-pass weld thermal cycles of a one-pass CGHAZ thermal cycle plus one pass of an incomplete recrystallization HAZ thermal cycle) of this developing steel.[2] The average impact toughness ( 50 °C) of the
XUAN-WEI LEI is with the Faculty of Materials, Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou 341000, P.R. China and also with School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China. SHUAN-BAO ZHOU and JI-HUA HUANG are with the School of Materials Science and Engineering, University of Science and Technology. Contact e-mail: [email protected] Manuscript submitted July 9, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
intercritically reheated CGHAZs under heat inputs of 15, 30, and 50 kJ/cm was about 75.2, 15.3, and 20.7 J, respectively. The chemical composition of this steel was redesigned to make it Cu-free. The manufacturing process has been improved. Thus, a Cu-free HSLA hull structure steel was developed. Test results showed this developed Cu-free HSLA hull structure steel had a yield strength of 820 MPa, tensile strength of 880 MPa, and low temperature at 50 °C of about 229 J. Investigation of the phase evolution and mechanical properties of CGHAZ of the developed Cu-free HSLA hull structure steel to evaluate its weldability was conducted in our previous work.[3] With analyses of the drawn continuous cooling transformation diagram, microstructures, and mechanical data (theoretical yield strength 785 and 775 MPa, tensile strength > 868 and 841 MPa, and impact toughness at 50 °C of 142 and 138 J under heat input 20 and 50 kJ/cm, respectively) of the simulated CGHAZs, it was concluded that the developed Cu-free HSLA hull structure steel had satisfactory weldability. As a significant part of microstructure characterization, the austenite grain size in the CGHAZ of the developed Cu-free HSLA hull structure steel has not been investigated in any previous study. The present work deduces a precise equation to predict the prior austenite grain size in the CGHAZ of this steel since the CGHAZ is considered the weakest zone in the HAZ, and its grain size plays an important role in phase transformation.
The equation provides a reference for CGHAZ grain size prediction in other similar steels.
II.
EQUATION FOR GRAIN SIZ
Data Loading...
