Abstract: The high-strength steel BS700 is commonly used as a structural component for the boom of aerial fire truck over 70 m, and its high-temperature mechanical properties determine the structural safety of the boom when it is in service near fire. The high-temperature mechanical properties of BS700 steel were tested using steady-state tensile testing and constant temperature and load uniaxial tensile testing methods at 20~1 000 ℃. The mechanical property parameters and stress-strain relationship curves at different temperatures were obtained, and its creep performance at temperatures 300~500 ℃ was investigated. The results show that the yield strength and ultimate strength of BS700 steel gradually decrease with increasing temperature, nearly decaying by 50% at 500 ℃, being only 30% of room temperature at 600 ℃, and being less than 10% when the temperature exceeds 800 ℃. Within 400 ℃, the temperature has little effect on the post-yield elongation rate of BS700 steel, but after that, as the temperature further increases, the post-yield elongation rate increases sharply. When the temperature is between 300 ℃ and 400 ℃ and the stress is 380 MPa, the maximum creep strain of BS700 does not exceed 0.4%; however, at 500 ℃ under the same stress conditions, the maximum creep strain reaches 10%. Based on the measured experimental data, a mathematical model was established through polynomial fitting to describe the variation law of high-temperature mechanical property parameters of BS700 high-strength steel with temperature, providing a theoretical basis for designing the safe structural strength of booms of aerial fire truck over 70 m.

Key words: aerial fire truck, high-strength steel BS700, high-temperature mechanical properties, high-temperature creep