Abstract: Based on the high-temperature thermal expansion analysis, the formability at different temperature of hot-forming 22MnB5 is studied and also verified by Dynaform simulation. Comparing the thermal expansion characteristics at forming temperature 800 ℃ and 700 ℃, the results suggest that：Forming at 800 ℃, the sample results in a tensile rupture since the principal strain in plane strain direction is too large, while the secondary strain in tensile-compressive zone is negative; forming at 700 ℃, the formability is significantly improved since the strain of all parts remain in a safety area and sample has a uniform deformation in biaxial stretching region and tensile-compressive zone. In addition, this work puts forward that the optimized forming temperature of hot-forming advanced high strength steel(AHSS) sample is not in the range of 800 ℃ to 850 ℃ reported in present literatures. This conclusion provides directions for deep exploration of optimized forming temperature and improvement of formability. A rapid cooling method is designed to provide a cooling rate over 27 ℃/s, with which the sample is cooled to 700 ℃-the target temperature for quenching. The experiment shows that by this method, there is a significant improvement on the formability, and the microstructure is denser

Key words: formability, high-strength steel, hot forming, stamping temperature, thermal expansion characteristics