Aiming at the surface powder loss of pickling spring steel 60Si2Mn during cold rolling after annealing,the surface,cross-sectional morphology and composition of annealed and cold rolled samples were analyzed,and it was found that there was an obvious loose layer of about 10 μm on the surface of the annealed and cold rolled samples,with Fe as the main component,and the powdery substance that was rolled off was mainly Fe too.In order to further explore the correlation between the loose layer and the iron oxide scale,the hot rolled sample,incomplete pickling sample and complete pickling sample were annealed in the full hydrogen furnace,and the results showed that the surface iron oxide scale of hot rolled sample was completely reduced to a layer of dense metal iron,and the loose layer structure similar to rolling powder appeared on the surface of the incomplete pick-ling sample,and the surface of the complete pickling sample still retained the initial surface of pickling.In addition,it was also found that there was an inner oxide layer with a thickness of 8 μm under the iron oxide scale of 6 μm of 60Si2Mn hot rolled sample,but after incomplete pickling and annealing,the thickness of the loose layer of 8 μm was much larger than the thickness of the iron oxide scale of the hot rolled sample,and it obviously extended to the matrix to include the inner oxide layer.Through pickling experiments,it is found that the structure of 60Si2Mn iron oxide scale is very dense,and pickling mainly corrodes the oxide scale in the form of microc-racks,because the pickling time required is about several times that of conventional high-carbon steel,therefore,at the same time as the corrosion of the iron oxide scale,the internal oxide layer undergoes obvious intergranular corrosion,which together with the residual iron oxide scale,forms a loose structure after annealing leading to powder loss problem during cold rolling.Therefore,for 60Si2Mn strip,in order to avoid the occurrence of such problems,on the one hand,it is necessary to try to pickle completely,on the other hand,control-ling the thickness of the inner oxide layer is also an important factor.
spring steelsurface powder lossiron oxide scaleinner oxide scaleintergranular corrosion
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