摘要:
镀锌/连退两用机组的退火周期与常规的连续退火机组明显不同,不仅退火周期较短、一次冷却速度低,而且无缓冷段。根据其工艺特点,以工业生产的热轧高温卷取低碳钢轧硬卷为试验材料,研究了退火温度和时间以及过时效对低碳钢和微碳钢组织和性能的影响。试验结果表明,不管是低碳钢还是微碳试验钢,退火后晶粒尺寸均较细,即使退火温度达到810℃,铁素体晶粒度仍在10.5级左右;经400℃×240 s过时效处理后,低碳钢的强度有所降低(10 MPa左右),延伸率有所提高,最高增加值为4.5%,微碳钢只有当退火温度达到810℃时,强度才有所降低(10 MPa左右),即过时效的作用不明显。通过采用微硼处理,优化连退和在线平整工艺,在热镀锌/连退两用机组上生产出了力学性能优良的产品。
Abstract:
The annealing cycle of the continuous annealing/hot-dip galvanizing dual-purpose line is different from that of the typical continuous annealing line which has no slow cooling section in addition to short annealing cycle and low cooling rate after annealing.The industrially-produced full-hard low carbon steel coils under high coiling temperature during hot rolling were used to investigate the effect of annealing temperature and time as well as over-aging treatment on the microstructures and mechanical properties of typical low carbon steels according to the characteristics of the dual purpose line.The results show that ferrite grains of both the low carbon steel and the extra-low carbon steel are fine with a grain size number of 10.5 even when the annealing temperature reaches 810℃.After over-aging treatment for 240 s at 400℃,the strength of the low carbon steel is lowered by about 10 MPa and its elongation is increased with a maximum of 4.5% while the strength of the extra-low carbon steel is lowered by about 10 MPa only at an annealing temperature of 810℃ or above,namely,the effect of over-aging treatment is limited.Steel sheets with excellent mechanical properties have been produced by optimizing the continuous annealing process and on-line skin-passing process as well as micro-alloying with baron on a continuous annealing/hot-dip galvanizing dual-purpose line.
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