EPS处理对热浸镀锌高强钢表面质量的影响

目的研究湿法抛丸(EPS)处理对800 MPa级高强钢表面质量及热浸镀锌效果的影响。方法采用金相显微镜、扫描电镜和辉光光谱仪,对EPS处理及盐酸酸洗、冷轧和热浸镀锌各生产工序中的800 MPa级高强钢表面形貌和表层成分分布进行研究。结果EPS处理卷表面凹凸不平,而盐酸酸洗态表面平整,EPS处理卷表面粗糙度Ra值为2.645μm,约为盐酸酸洗卷的2倍,残留的表面氧化铁皮厚度为0.93μm,比盐酸酸洗试样厚45%。冷轧状态下,EPS处理卷表面凸起被轧平,表面基体“露白”比例约为63.5%,比盐酸酸洗低20.1%,残留的表面氧化铁皮厚度为0.36μm,比盐酸酸洗试样厚57%。热浸镀锌态下,EPS处理卷锌晶界存在尺寸3~5μm的孔隙,表面易出现尺寸约1 cm的漏镀缺陷。去除表面锌层后发现,EPS处理卷基板表面存在“翘皮”,微观观察抑制层形貌发现,界面处Fe-Al抑制层颗粒未充分形成,甚至未形成。GDS分析表明,抑制层处Al峰值较盐酸酸洗卷低17%。结论EPS处理后表面凹凸不平,冷轧时易“折叠”分层,去锌层基板表面有“翘皮”,易造成锌层厚薄不均,同时EPS处理的残留氧化层较厚,且易造成氧化铁皮嵌入基体,导致锌层与基板界面Fe-Al抑制层稀疏,锌层粘附性低,甚至漏镀。

Effect of EPS Treatment on Surface Quality of Hot Dip Galvanized High Strength Steel

The work aims to study the influence of EPS treatment on the surface quality and hot-dip galvanizing effect of 800 MPa grade high-strength steel.Optical microscope(OM),scanning electron microscope(SEM)and glow discharge spectrometer(GDS)were used to study the surface morphology and surface composition distribution in Eco Pickled Surface(EPS)treatment and hydrochloric acid pickling treatment,cold rolling and hot dip galvanizing.The surface of EPS treatment coil was quasi valley,while the surface of hydrochloric acid pickling state was flat.The surface roughness value of EPS treated coil was 2.645μm,about 2 times that of the hydrochloric acid pickling coil,and the thickness of the remaining surface oxidized iron sheet was 0.93μm,45%higher than that of the hydrochloric acid pickling steel coil.In the cold-rolled state,the surface of the EPS treatment coil was flattened,and the surface whiteness of the substrate was about 63.5%,20.1%lower than that of hydrochloric acid pickling.The residual oxidized iron thickness of EPS treatment coil was 0.36μm,57%thicker than that of hydrochloric acid pickling steel coil.Under the condition of hot dip galvanization,there were pores of 3~5μm in the grain boundary of zinc coil treated with EPS,and the surface was prone to plating leakage defects of about 1 cm in size.After the zinc layer on the surface was removed,the substrate surface treated with EPS was up-warped.For the inhibition layer,the particles of Fe-Al inhibition layer at the interface were not fully formed,or even not formed.GDS result showed that Al peak value at inhibition layer was 17%lower than that of hydrochloric acid pickling coil.After treatment with EPS,the surface is uneven,and it is easy to fold layer during cold rolling.After removal of the zinc layer,the substrate surface is up-warped and is easy to cause uneven thickness of zinc layer.At the same time,the surface treated by EPS has a thick residual oxidation layer and tends to cause the iron oxide scale to be embedded in the substrate,leading to sparse Fe-Al inhibition layer between the zinc-layer and the substrate interface,which resulted in low adhesion of the zinc layer and even plating leakage.