Justification and selection of cooling schemes for rolls of a sheet rolling mill based on mathematical modeling of heat exchange processes between rolls and a strip

Abstract

Trishevsky O. I., Saltavets M. V., Kondrashchenko V. O. Justification and selection of cooling schemes for rolls of a sheet rolling mill based on mathematical modeling of heat exchange processes between rolls and a strip. Material working by pressure. 2020. № 1 (50). Р. 307-314.

The features of the equipment and technological processes for obtaining hot-rolled sheet on broad-band mills in Ukraine and industrialized countries such as the USA, Germany, France, Italy, Austria, Japan are considered.  The main trends in the improvement of technology and equipment are determined in order to reduce energy consumption, cost of manufactured products and increase their competitiveness abroad. The main ones are: ensuring the stability of the parameters of the technological process of sheet rolling through the use of modern designs of rolling mills, equipping them with appropriate instrumentation and automation of the technological process, as well as improving the technology of rolling and cooling through the use of compact ultra-high-speed strip cooling units, which are installed between the roughing and finishing groups of stands, as well as after the finishing group before the coilers. The use of this technology of ultra-high-speed strip cooling during rolling makes it possible to obtain hot-rolled steel sheet with stable mechanical properties when rolling ultra-thin sheets.  The results of theoretical studies of the thermal state of work rolls during hot rolling of a sheet are presented on the example of the finishing stand of mill 2250 of the Alchevsk metallurgical plant.  Recommendations are given on the use of effective roll cooling schemes. In particular, two new schemes for their cooling are proposed: a) promising; b) economic.  When using a promising scheme for supplying water to the roll, the temperature rise in one cycle is halved and amounts to 5–6 °C. An essential difference of the economical method of water supply is that the temperature field of the roll is stabilized when the length of the forced cooling zone is reduced by 25 %, due to which makes it possible to reduce the amount of water for cooling.  The durability of the rolls is increased by 10 % due to the stabilization of the thermal state.