FD级镀锌钢卷的表面质量控制

FD级表面镀锌IF钢是表面质量要求最高的镀锌产品，表面质量控制难度大，合格率低。其主要缺陷之一“线状”缺陷是炼钢内生夹杂或保护渣卷入引起的。控制“线状”缺陷的主要措施是洁净度控制和机清（火焰清理）。为了对比洁净度控制和机清措施的有效性，进行了IF钢镀锌钢卷表面质量控制试验。结果表明，机清对提高FD命中率的作用大于洁净度控制措施；没有经过机清的板坯，钢水洁净度控制措施、连铸液位波动和三路氩气背压控制的影响是明显的。试验过程发现的“机清翘皮”缺陷，是机清板坯表面毛刺或凸棱经轧制形成的。“机清翘皮”下方没有夹杂物，有时能够发现少量FeO。修磨等提高机清后板坯表面质量的方法有助于消除机清“翘皮”缺陷。

Surface quality control of FD- class galvanized sheet

FD- class galvanized sheet represents the highest surface quality of IF steel product due to the the difficulty to control the surface quality and the low qualification rate. One of the important defects called “sliver”, is induced by the endogenous inclusion entrapment or mold flux entrapment. The cleanliness control actions and flame scarfing are taken to control the “sliver” defects. To compare the validity of cleanliness control actions and flame scarfing, the experiment on surface quality control of IF galvanized sheet is conducted. The results show that the flame scarfing plays bigger role in improving surface quality of galvanized sheet. Without flame scarfing, it woud be effective to take the cleanliness control actions, control mold level fluctuation or keep the argon atmosphere in stopper, tundish nozzle and submerged nozzle. Another defects called “scarfing upwards” are found in the test, which are produced by rolling the burrs or ridges on the scarfing slab surface, and there is no inclusions but little FeO under the block. The means to improve the surface quality of scarfing slabs, such as grinding, do well in eliminating the “scarfing upwards”.