AA1235Double Zero Aluminum Billet Tissue Lump Defects’ Study And Control Defects

The usage of CC (continuous casting) strip to produce two-zero aluminum foilhas high efficiency, high-speed, and low energy-consuming，maintaining obviousadvantages of economy. However, due to the technological characteristics ofcontinuous casting，resulting in strip breakage and pinhole defects when foil rolling.This paper is based on the production status of Shangqiu Yangguang AluminumMaterials LLC, according to the customer’s feedback the rate of strip breakage andpinhole of finished products is high when foil rolling, by a lot of research of thewhole cold rolling process of roll casting billet, it is concluded that the texture of rollcasting billet contains a large number of agglomerated defects is the main reason forthe high rate of strip breakage and pinhole of finished products. Therefore, mainly bymeans of metallographic microscope, scanning electronic microscope and energyspectrometer analysis, this paper future studied the agglomerated defects, and came toan conclusion that the hydrogen and slag inclusion in the aluminum melt is the mainreason to the formation of agglomerated defects. So through the experimentalverification, it is a feasible measure by optimizing the hydrogen and slag inclusionsremove process. The main research contents and results of this paper are as follows:1. The distribution of second phase in longitudinal texture of cast-rolling sheetspresents a characteristic that more in the middle, fewer on the two sides, and the sizeof particles in the central layer is larger than that on the surface. The grain ofcast-rolling sheets shows inhomogeneity of microstructure and non-equilibriumcharacteristics in thickness direction. It is distorted fiber texture on the surface area,however into the central layer, it becomes slender columnar crystal. By comparingthe normal cast-rolling texture and that contains agglomerated defects, it comes to aconclusion that the grain size change of cast-rolling texture is inconspicuous in thethickness direction, the grain on the surface is small, and the columnar crystal in thecentral layer and rib is inconspicuous.2. Through a lot of metallurgical research on the cast-rolling sheets produced bythe company, it sums up that the agglomerated defects divide into two kinds: dark and gray, and in the thickness direction of cast-rolling texture there are moreagglomerated defects on the surface and ribs than that in the center. By usingscanning electron microscopy (SEM) and energy spectrum analysis, it is found thatthe dark agglomerated defects is mainly oxide inclusions and intermetallic compound,the gray agglomerated defects is mainly the enrichment of micro pores.3. Studying the law of hydrogen change in the holding furnace from pouringfurnace to the furnace charge finish, thus determine the optimal time interval ofholding furnace refining. Then selecting three parameter of holding furnace refiningtime, determine the optimal time of the holding furnace refining.4. By optimizing the hydrogen remove process in the holding furnace, theagglomerated defects in the cast-rolling texture reduced, the mechanical properties oftwo-zero foil billet improved.5. On the basis of optimizing the hydrogen remove process in the holdingfurnace, regulating the slag remove process of cast-rolling production, change thesecondary ceramic filtering plate from the past50meshes to60at the same time. Bya lot of experimental verification, the agglomerated defects of cast-rolling texture arealmost eliminated, and the mechanical properties of the two-zero foil billets areimproved.6. According to the customers’ feedback, when foil rolling the two-zero foilbillets which produced by the company the rate of strip breakage and pinhole offinished products declined obviously, conform to the requirements of the customers.