Андрей Ростиславович Фастыковский, д.т.н., профессор кафедры «Обработка металлов давлением и материаловедения. ЕВРАЗ ЗСМК»
Россия, 654007, Кемеровская область – Кузбасс, Новокузнецк, ул. Кирова, 42
Andrei R. Fastykovskii, Dr. Sci. (Eng.), Prof. of the Chair “Metal Forming and Metal Science. OJSC “EVRAZ ZSMK”
42 Kirova Str., Novokuznetsk, Kemerovo Region – Kuzbass 654007, Russian Federation
Владимир Анатольевич Вахроломеев, аспирант кафедры «Обработка металлов давлением и материаловедения. ЕВРАЗ ЗСМК»
Россия, 654007, Кемеровская область – Кузбасс, Новокузнецк, ул. Кирова, 42
Vladimir A. Vakhrolomeev, Postgraduate of the Chair “Metal Forming and Metal Science. OJSC “EVRAZ ZSMK”
42 Kirova Str., Novokuznetsk, Kemerovo Region – Kuzbass 654007, Russian Federation
Александр Григорьевич Никитин, д.т.н., профессор кафедры механики и машиностроения
Россия, 654007, Кемеровская область – Кузбасс, Новокузнецк, ул. Кирова, 42
Aleksandr G. Nikitin, Dr. Sci. (Tech.), Professor of the Chair of Mechanics and Machine Engineering
42 Kirova Str., Novokuznetsk, Kemerovo Region – Kuzbass 654007, Russian Federation
In modern industrial and civil construction, various rolled metal products are used in greater volumes. The largest share of them is occupied by rebar profiles produced at small-grade mills. The ever-growing demand for rebar rolling requires an increase in production volumes. The most promising technology in this regard is rolling – separation, which, with relatively low material costs, allows operating rolling mills to significantly increase the production volume of rebar profiles while reducing energy consumption. However, despite the obvious advantages of rolling – separation technology using non-drive dividing devices, it is very difficult to correctly determine the rational modes of conducting the process taking into account the peculiarities of production and equipment layout, which is due to insufficient theoretical knowledge. One of the main problems is determination of the permissible distance in the rolling cage – non-drive dividing device system. The conducted studies allowed us to propose a dependence for determining the maximum permissible distance in the rolling cage – non-drive dividing device system for reasons of longitudinal stability of the strip, taking into account the size and shape of cross-section of the split articulated profile, the nature of pinching, and the backstretch stress. It was experimentally established that when determining the permissible distance between rolling cage and non-drive dividing device, it is advisable to take the length reduction coefficient equal to 0.7.
В современном промышленном и гражданском строительстве в больших объемах используется различный металлопрокат, наибольшую долю в котором занимают арматурные профили, производимые на мелкосортных станах. Постоянно растущая потребность в арматурном прокате требует повышения объемов производства. Наиболее перспективна в этом плане технология прокатки – разделения, которая при относительно небольших материальных затратах позволяет на действующих прокатных станах существенно повысить объем производства арматурных профилей при снижении энергозатрат. Однако, несмотря на очевидные преимущества технологии прокатки – разделения с использованием неприводных делительных устройств, большие затруднения вызывает правильное определение рациональных режимов ведения процесса с учетом особенностей производства и компоновки оборудования, что связано с недостаточной теоретической изученностью. Одной из основных проблем является определение допустимого расстояния в системе прокатная клеть – неприводное делительное устройство. Проведенные исследования позволили предложить зависимость для определения максимально допустимого расстояния в системе прокатная клеть – неприводное делительное устройство из соображений продольной устойчивости полосы с учетом размера и формы поперечного сечения разделяемого сочлененного профиля, характера защемления, напряжения подпора. Экспериментально установлено, что при определении допустимого расстояния между прокатной клетью и неприводным делительным устройством коэффициент приведения длины целесообразно принимать равным 0,7.
Modern realities are characterized by the active growth in industrial and civil construction. Advanced construction technologies increasingly rely on the use of prefabricated structures made of reinforced concrete and metal products [1 – 3]. The constantly rising demand for construction metal products necessitates solutions that offer a short payback period, low costs for production re-equipment, and a significant increase in productivity. The rolling – separation technology meets all these requirements [4; 5]. Currently, the rolling – separation technology is developing in two directions, distinguished by where the longitudinal dividing occurs: either within the rolls of the rolling mill, which simultaneously forms and divides the articulated profile, or in a separate stand-alone non-driven dividing device. On most modern rolling mills, the second method is preferred, as separating the operations of forming the articulated profile and subsequent longitudinal separation in a separate stand-alone non-driven device significantly simplifies equipment setup [6 – 9]. However, this arrangement can lead to a potential loss of natural longitudinal stability if the distance between the rolling mill and the non-driven dividing device is chosen incorrectly. Currently, this issue is addressed through trial and error, which results in increased defective products and unforeseen downtime of the primary rolling equipment.
The use of 3D simulation methods does not allow for the assessment of the permissible distance that ensures natural longitudinal stability [
\[{l_{\max }} = \frac{{\pi \sqrt {Ei_{\min }^2} }}{{\sqrt {{\sigma _2}} k}},{\rm{at }}\frac{{{\sigma _2}}}{{{\sigma _s}}} \le 1,\]
where lmax is the maximum permissible distance between the rolling mill, which forms the articulated profile, and the non-driven dividing device, ensuring longitudinal stability; Е is the modulus of elasticity of the first kind, MPa; k is the coefficient of length reduction; imin is the minimum radius of the section inertia; σ2 is the support stress necessary for longitudinal division by the non-driven dividing device; σs is the resistance to deformation of the material being divided.
As can be seen from the presented dependency, the magnitude of the maximum permissible distance depends on the support stress necessary for longitudinal separation, the shape, and the area of the cross-section of the articulated profile, which are characterized by the minimum radius of inertia, the modulus of elasticity of the first kind, and the coefficient of length reduction. Among the factors considered, the coefficient of length reduction has a significant impact, varying from 0.5 to 2.0 depending on the nature of the clamping [
To determine the coefficient of length reduction during the implementation of the rolling – separation process, laboratory experiments were conducted. These experiments compared the critical force corresponding to the moment of loss of stability, obtained both theoretically using Euler’s equation and experimentally. The experimental and theoretical data obtained with coefficients of length reduction of 0.5 and 0.7 are shown in the figure.
According to the obtained data, when determining the natural longitudinal stability of the strip in the rolling mill – non-driven dividing device system, a coefficient of length reduction equal to 0.7 is required to achieve values closer to the experimental data. With a coefficient of length reduction of 0.7, the calculated data are 10 – 15 % less than the experimental data. In practical use, this provides a margin of safety when determining the permissible distance in the rolling mill–non-driven dividing device system.
Conclusions
A dependency has been derived that enables the estimation of the maximum permissible distance between the rolling mill stand and the non-driven dividing device, ensuring the longitudinal stability of the strip during the implementation of the rolling–separation technology. Experimentally, it has been established that the length conversion coefficient for the rolling–separation technology using a non-driven dividing device should reasonably be taken as 0.7.
The authors declare that there are no conflicts of interest present.