312-paper-快冷对超高强钢板性能的影响（英）.docVIP

Effect of fast cooling on the properties of continuous annealed phase transformation hardened ultra high strength steels Xiaodong Zhu Xufei Li (Technology Center, Baoshan Iron and Steel Co. Ltd, Shanghai 201900) Abstract: Cold rolled high strength steels primarily alloyed with C-Si-Mn are investigated to study the effect of cooling parameters on the mechanical properties in order to obtain tensile strength as high as 980MPa. It is found that tensile strength can be prominently increased by increasing fast cooling speed. When the fast cooling speed is between 15-150℃/s, which is typical for high speed gas jet cooling, the carbon content must be at least 0.15% to ensure the minimum strength requirement of 980MPa. Water quenching can greatly increase the strength, but still the least carbon content should be well above 0.1% to obtain 980MPa grade. Other processing parameters such as the fast cooling start temperature, fast cooling end temperature as well as overageing temperature all have significant influences on the yield and tensile strength of the experimental steels. For the experimental steels with relatively low alloy addition, the strength is significantly reduced if overaged at temperature of 350℃ or above. Microstructure study reveals obvious decomposition of martensite and precipitation of cementite at high overageing temperatures, which inevitably leads to the decrease in strength. Key Words: cold rolled；ultra high strength steel；continuous annealing Xiaodong Zhu, PH D, Engineer, Institute of Auto Steel Research, Technology Center, Baosteel. E-mail: xdzhu@ 1 Introduction To reduce fuel consumption and exhaust emissions, reducing auto weight is becoming one of the major concerns of the auto industry. Along with the trend toward new alternative fuels, new automotive architectures may require further reduction to the mass. To reduce weight and meanwhile maintain the rigidity of the auto body structure, ultra high strength steel must be applied to replace curr