Microstructural changes under Fire in TMT 500W Structural Steel rebars

4th International Conference on Structure, Processing and Properties of Materials

Shahriar, M.S.^1 ; Nawaz, M.R.^1 ; Islam, M.A.^1

Department of Materials and Metallurgical Engineering, Bangladesh University of Engineering and Technology, Dhaka

1000, Bangladesh^1

关键词: High temperature;    High-temperature exposure;    Increasing temperatures;    Load bearing capabilities;    Microstructural changes;    Reinforced cement concretes;    Steel bars;    Tempered martensite;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/438/1/012035/pdf
DOI  :  10.1088/1757-899X/438/1/012035

来源: IOP

【 摘 要 】

Reinforced cement concrete or RCC has become the most commonly utilized construction material for various buildings, bridges, flyovers, etc. As plain concrete can't easily withstand the stresses created by vibrations, wind or other forces; steel bars, plates or fibers are embedded as reinforcing agent, which amplify the load bearing capability. But as the temperature is increased, e.g. in case of unwanted fire the load bearing capability of steel decreases at an alarming rate, so the RCC structure becomes vulnerable at high temperatures. In our country, TMT 500W steel rebars are increasingly used as reinforcement in RCC, but there are no enough studies regarding the properties of this type of steel, especially for locally produced grades, at very high temperatures. For this study, TMT 500W steel rebars of 8mm diameter from three different local brands were collected and their composition & room temperature tensile properties were evaluated. Then microstructures at various high temperatures of 500, 600 and 650°C along with room temperature had been investigated. The results show that, the microstructure of each of as received samples at room temperature consists of ferrite and pearlite at the core and tempered martensite at the edge. At high temperatures, martensite and bainite at the edge became virtually vanished due to high temperature exposure and converted to ferrite and pearlite. The grain coarsening with increasing temperature was also significant.