The study of micro-macroscopic act of steel materials under fire

• Main Author: 何以新
• Other Authors: 楊錦懷
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/14279949570251135835

碩士 === 國立臺灣科技大學 === 營建工程系 === 90 === There are plenty of people in small Taiwan and in order to make the buildings provide more people with more space, the building are manufactured higher and higher. The demands of steel materials also increase year by year. Besides, the frequency of fire accidents in Taiwan is quite high and the fire temperature and fire duration of each fire accident vary according to the differences of fire-load and ignition objects. So this study uses temperature of 350℃, 450℃, 550℃ and 650℃ with fire duration of 0 hour, 1 hour, 2 hours and 3 hours as testing variables, carrying out tensile-testing and SEM observation in order to understand if the characteristics of the steel under fire are critical to the safety of structure. Study results show that the higher the fire temperature and the loner the fire duration, the lower the strength of steel. But the ductility of steel has different tendency according to the difference of fire temperature. When temperature is higher than 550℃, the loner the fire duration the better the ductility of steel. For toughness, when temperature is lover than 550℃, the longer the fire duration the worse the toughness, but tendency is contrary when temperature is over 650℃. Macroscopic behavior and microscopic structure have intimate relationships. From the cross section of fracture, one can find the degree of high-temperature oxidation at the edge of dimple. The worse the degree of the oxidation, the thicker the de-carbonization layers and the lower the strength. The higher the temperature and the longer the fire duration, the worse the oxidation and the degree of de-carbonization.