Addition of MgO Nanoparticles to Carbon Structural Steel and the Effect on Inclusion Characteristics and Microstructure
- PDF / 3,643,040 Bytes
- 13 Pages / 593.972 x 792 pts Page_size
- 72 Downloads / 194 Views
ODUCTION
NOWADAYS, the demand for various kinds of steels with good mechanical properties, especially strength, plasticity, and toughness, is significantly increased. It is well known that fine-grained strengthening, one of the various strengthening processes, contributes to impeding dislocation movement of the internal microstructure when external forces are applied to steel materials. It is also the only method hitherto to simultaneously improve the above three mechanical properties. Fine-grained strengthening mainly focuses on inducing the precipitation of intragranular acicular ferrite (IAF) in austenite grains to improve the mechanical properties and service life of the materials.[1] Conventionally, precipitation strengthening and thermomechanical processing are the most common methods to obtain appropriate microstructures.[2,3] The latter can be achieved during actual production through austenite non-crystallization controlled rolling,[4] strain-induced transformation, and accelerated cooling.[5,6] However, the precise control of important
XIANGZHOU GAO, Ph.D. Candidate, SHUFENG YANG, Associate Professor, JINGSHE LI, Professor, HANG LIAO, WEI GAO, and TUO WU, Postgraduates, are with the State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China and also with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China. Contact e-mail: [email protected] Manuscript submitted May 26, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
parameters such as micro-alloy content, cooling and rolling conditions must be specifically investigated in order to satisfy the individual requirements of different steels. Furthermore, with the thickness of the steel plates increasing continuously, larger welding energy must be input to maintain high fabrication efficiency, which ultimately would lead to microstructural coarsening in the heat-affected zone after welding.[7] In recent years, one proposed theory named ‘‘grain refinement of steel by second-phase particles’’ may theoretically slide over the above defects. The concept of incorporating second-phase particles in metal was first proposed by Zener.[8] The main purpose of this concept is to retard austenite grain growth with the pinning effect of precipitates and develop fine AF structure. Initially, steel researchers tried controlling steelmaking conditions or adding certain alloy elements to steel melt to obtain small-sized second phases (less than or equal to 1 lm[9]) with thermally stable nature. This refinement mechanism is basically consistent with ‘‘oxide metallurgy’’ theory.[10,11] Some studies[12–14] demonstrate that Ti2O3 is the optimal species to provide active nucleation sites for AF when introduced into steel. Shang et al.[15,16] also have performed a series of laboratory experiments to investigate the influence of steel composition, cooling velocity, and other relative factors on the inducing ability of titanium oxides for AF. High-melting titanium nitr
Data Loading...
