Development and Experimental Testing of the Technology for Producing Deformed Bars of Alloy D16T from Continuously Casting Billets of Small Diameter with Low Elongation Ratios

Abstract

The article describes the development and pilot-industrial testing of the technology for producing bars from aluminum alloy D16T obtained by radial-shear rolling (RSR) from continuously cast billets (CCB) with a diameter of 72 mm in several passes. The actual dimensions of the rolled bars were within ±0.16 mm for all bar diameters, which is significantly less than the diameter tolerance stipulated by the requirements of GOST 21488–97. According to the results of tensile tests, the values of ultimate strength, conventional yield strength, relative elongation, and relative reduction were determined. The requirements of the regulatory documents for the ultimate strength and relative elongation for the D16T alloy are satisfied with a total elongation ratio of more than 4.2. In terms of plastic properties, the obtained bars are 2.1–2.5 times higher than the requirements of GOST in the entire range of investigated elongation ratios, starting from 2.07. At the same time, there is an increase in the relative elongation by 5.7–6.8 times in comparison with the initial cast state. The performed analysis of the microstructure and morphology of the secondary phases showed that, with a decrease in the diameter of the bar (with an increase in the total elongation ratio), the average particle size of the α(AlFeMnSi) phase insoluble in the aluminum matrix decreases, which is a consequence of the development of deformation processes during rolling. Additional grinding of inclusions during deformation processing can significantly reduce the possible negative effect of the insoluble phase on the mechanical properties of the resulting bars, in particular, on the property of plasticity. The analysis of the microstructure showed that the bars after rolling and heat treatment do not have cracks, looseness, delamination, and other defects and meet the requirements of GOST 21488–97.