超快速加热对冷轧IF钢组织和力学性能的影响

超快速加热工艺由于高效和经济的优点而受到广泛的关注,为了研究该工艺对冷轧IF钢组织和性能的影响,设计了两类超快速加热工艺——直接加热和预热工艺,特别地与连续退火工艺进行了比较。与870 ℃保温270 s的连退样品相比,以200~500 ℃/s加热至870 ℃可明显细化IF钢晶粒,采用500 ℃/s超快速加热能够明显提高屈服强度,如抗拉强度可达约300 MPa,而伸长率依然保持在约43%。相比于直接加热,在引入400 ℃的预热段后晶粒可进一步细化,同时由于回复消耗存储能导致再结晶温度显著提高;然而,预热超快速加热工艺会产生{110}<110>织构,并降低了γ织构强度,导致在拉伸变形过程中容易发生减薄进而导致颈缩提前,因而降低了塑性。

Effect of ultra-fast heating on microstructural evolution and mechanical properties of IF steel

Ultrafast heating (UFH) process has attracted a wide attention due to its high efficiency and economic advantages. To investigate the influence of UFH on the microstructural evolution and mechanical performance of the cold-rolled IF steel sheet, two types of UFH processes, i.e. the direct UFH and a preheating stage were performed. Compared with the conventional continuous annealing (CA) process at 870 ℃ for 270 s, the direct UFH process at 200-500 ℃/s to 870 ℃ could effectively refine the grain sizes. In particular, the UFH at 500 ℃/s could obviously improve the yield strength, for example the tensile strength approximately reached 300 MPa, while the total elongation remained 43%. Compared with direct heating, the grains can be further refined after the introduction of 400 ℃ preheating section, and the recrystallization temperature can be significantly increased due to the recovery consumption of storage. However, the preheating stage also caused {110}<110> texture appear and the weaker texture strength, leading to thinning in the process of stretch deformation, which resulted in the necking advance, thus reducing the plasticity.