Vyatka State University, Kirov, Russia:

M. Z. Pevzner, Professor at the Department of Metals Processing, Candidate of Technical Sciences, Associate Professor, e-mail: mikhailpevzner@yandex.ru
D. G. Sergeev, Acting Head of the Department of Mechanical Engineering Technology, Candidate of Technical Sciences, Associate Professor

This paper examines the effect of the thickness h, the deformation reached during the last cold rolling operation ε and the final normalized annealing mode v on the mechanical properties of brass band. The paper looks at the correlation between the ultimate strength σ_в, elongation and hardness HV in terms of their meeting the specification. The production of L68 brass band involved semi-continuous casting, hot rolling to the thickness of 6 mm and cold rolling to h = ~0.56–0.96 mm with intermediate annealing at H = 1.5–2.7 mm ensuring the deformation ε within 62 to 72%. The intermediate and final continuous annealing lines are equipped with three-phase TFIH (Transverse Flux Induction Heating) units. An intermediate annealing mode has been established that ensures the grain size of 40–80 μm. The strip travel speed was varied as follows during final annealing: ν = 30–46 m/min. The authors determined the stochastic dependences of the properties on ν , h and ε, as well as the annealing modes that are necessary to achieve each property. Actual correlations HV(σ_в), δ(σ_в) within the specified ranges were considered versus the properties of the band produced by deformation. It was established that the cold rolling process, together with the heat treatment mode, has an effect on the properties of annealed band and, vice versa, on the heat treatment mode that is necessary to achieve the required properties. With hardness being the same, the induction heat annealed brass band has a higher ultimate strength в than the band produced by normalized final deformation. As a result, the linear relationship σ_в = f(HV) of the rolled band produced by normalized final annealing is shifted in relation to the optimum position of such relationship within the specified limits adopted in the period when the rolled band was exclusively produced by final deformation. Consequently, the final annealing mode ranges that are necessary for achieving certain properties within the specified ranges, do not match, thus making the task of having the resulting properties hit the above ranges more challenging. Thus, it is proposed to use online control and annealing control to eliminate rejects, and to use the annealing mode-required property relationships obtained from the given data for setting up the initial process mode.

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