Abstract:In order to eliminate the surface star cracks of hot rolled Q355B steel plates, a series of methods including thermodynamic calculation, metallographic examination, grinding, shot blasting, acid pickling, macroscopic evaluation, SEM and EDS analysis were conducted to probe into the reasons. The results showed there is no finding of decarburized layer, oxidation origin, the secondary phase particle, inclusion and copper in the cracks, which indicated the occurrence of surface star cracks is not from slab defect. The low cracking ratio of steel plate produced by cold charging and analysis of two-phase domain demonstrated the occurrence of surface star cracks is mainly caused by hot charging of slabs in the two-phase domain between 767 ℃ and 677 ℃. Through independent design and application of spraying device, and meanwhile controlling the temperature more than 790 ℃ before entering spraying zone and then less than 510 ℃ when leaving spraying zone, the slab surface temperature before entering the heating furnace was decreased to be less than 635 ℃. Eventually, the star crack ratio decreased from 0.99% before technology improvement to 0.07% at 2021.
王龙飞. Q355B钢板表面星裂缺陷的研究与控制[J]. 连铸, 2022, 41(5): 82-87.
WANG Long-fei. Study and control of surface star cracks on Q355B steel plates. CONTINUOUS CASTING, 2022, 41(5): 82-87.
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