高效无取向硅钢冷轧过程断带分析

Analysis of stripbreakage on high-efficiency non-oriented silicon steel during cold rolling

对鞍钢高效无取向硅钢热轧卷在环形炉退火后进行冷轧过程中出现的断带故障进行了分析。通过观察热轧钢板断面金相,发现钢板次表面存在较多的夹杂物;扫描电镜定性分析表明,该夹杂物是氮化铝。造成冷轧断带的主要原因是,热轧卷退火过程中保护气氛中的氮渗入钢中,与钢中的铝结合生成氮化铝,造成的夹杂物异常增多,破坏了钢质的连续性。钢中的氮含量沿板厚方向存在梯度,钢板边部较心部氮含量明显偏高,与钢板表面的氧化铁皮分布有较强的对应关系,说明氧化铁皮在退火过程中对氮的渗入起到了催渗的作用。同时,渗入的氮在钢板焊接时从焊缝逸出形成气泡,对焊接质量产生严重影响。

The cold rolling strip breakage fault of high-efficiency non-oriented silicon steel made in Ansteel was analyzed,of which the hot rolled coil was annealed in a ring furnace before cold rolling.Many inclusions were found on the subsurface of hot-rolled steel plate by metallographic observation of steel plate section.And by SEM observation,it was showed that the inclusions were AlN.The main reason of the cold rolling strip breakage was the nitrogen in protection atmosphere permeated into steel during annealing of hot rolled coil,which was then generated into AlN combining with the aluminum in steel,causing the abnormal increase of inclusions and broking the continuity of steel.The nitrogen content in steel had a gradient along the direction of the plate thickness,and the nitrogen content in the edge of steel plate was evidently higher than that in the core,which had a strong corresponding relationship with the oxide scale distribution on the surface of the steel plate,and it is indicated that the oxide scale played a catalytic role in nitrogen infiltration during the annealing process.Meanwhile,the infiltrated nitrogen escaped from the weld and form bubbles,which affected the welding quality seriously.