The structure and mechanical properties formed in the soft L63 brass band commercially produced using transverse flux induction heating

Abstract

This paper looks at the structure and mechanical properties formed in a steel band while it is processed to the soft state using a variety of different adopted and pilot processes that involve Transverse Flux Induction Heating (or, TFIH). Varying concentrations of copper were examined: 62.5 ± 0.2 and 64 ± 0.2 %. After semicontinuous casting and cutting to length, ingots were heated in a continuous gas furnace. Hot-rolled bands with the thicknesses of 5 and 8 mm were coiled and the coils were air- or water-cooled. A portion of the coils was annealed in a batch furnace and cooled down in the same way. After the bands were cold-rolled down to 2.0, 2.2 or 2.4 mm, they were coiled and the coils were annealed in the batch furnace or treated by TFIH technique in the most intense mode. The second rolling cycle was conducted using the adopted processes and reaching the thicknesses of ~0.6, 0.8 and 1.0 mm and various degrees of deformation. After that, the band was subjected to varying annealing modes of the TFIH process. It was found that the key factor contributing to a higher ultimate strength includes a significant concentration of β-phase, which tends to rise as the concentration of copper goes down. At the same time, rapid cooling after TFIH annealing does not lead to any significant rise or decrease in the β-phase concentration. Thus, the key factor for the ultimate strength to rise includes the β-phase that forms as a result of hot rolling and remains through a sequence of TFIH cycles. It was established that the process involving hot rolling followed by cold rolling in two or more passes and at least one intermediate annealing cycle in a batch furnace and a final continuous TFIH annealing cycle ensures the soft state in the L63 band. Compared with the process that involves final batch annealing, this process offers better energy efficiency with the minimal lengthwise variation of properties.The authors would like to express their heartfelt gratitude to V. M. Mikhalev, S. N. Polyaev, A. A. Sozontov, I. V. Kharitonova, A. V. Koloshnitsyn, V. G. Igoshin, F. G. Bikmetova, L. V. Mashinina, T. V. Budneva and other employees of the Kirov Non-Ferrous Metals Processing Plant who contributed to this research.