Rolling of steel in Hot Strip Mill Dec03

Rolling of steel in Hot Strip Mill...

Rolling of steel in Hot Strip Mill Hot strip mills in these days are either conventional hot strip mills or strip mills for rolling thin slabs. The primary function of the conventional hot strip mill (HSM) is to reheat the semi-finished steel slabs (rolled or continuously cast) to the rolling temperatures and then to roll them thinner and longer through a series of rolling mill stands driven by large motors and finally coiling up the lengthened steel sheet for its easy handling and transport. Coils are produced with an inside diameter of 750 mm on the coilers, with  an outside diameter of up to 2400 mm and with the limitations of coil weight up to 220 kg per cm width. The hot strip mill supplies coils for cold rolling mill, strip shearing and slitting units as well as a finished product for shipment directly to the customers. Most material is transported out of the mill area by an automated coil handling system to the storage aisle. Attributes imparted to the strip by the hot rolled strip mill include surface quality, thickness, width, and flatness control as well as strip profile. Rolling of steel slabs in hot strip mill consists of several sub-processes and at the end of them the final product ‘hot rolled coil’ is produced. The main sub-processes are (i) heating of steel slabs in the reheating furnace, (ii) descaling of the heated slab and its sizing in sizing press, (iii) rolling in the roughing mill and secondary descaling, (iv) rolling in the finishing mill, (v) control cooling of the hot rolled strip and (vi) coiling of the rolled strip. Reheating of the slab Critical to the hot strip mill is the reheating furnace. Modern hot strip mills are equipped with state of...

Main Features of a modern Hot Strip Mill Dec22

Main Features of a modern Hot Strip Mill...

Main Features of a modern Hot Strip Mill The objective of a hot strip mill (HSM) is to reheat and roll thick slabs into thin strip with a wide range of thickness. Because of its huge size and large investment a hot strip mill need to have a life time of several decades. The mill must be capable of meeting the market demands for a wide range of steel grades, in particular, high strength and advanced high strength steels (AHSS) with good cold formability and with superior strip properties. The mill should be able to meet the following requirement High mill availability coupled with high productivity and high yields. Meeting the need of low maintenance. Meeting the need of lower energy consumption. Improved product quality by meeting close thickness and profile tolerances as needed by the modern day customers, through powerful controls and adjustments. These tolerances may be much closer than specified in various international standards. More flexible rolling schedules to ensure short delivery times and economical rolling of smaller lot sizes. For achieving these demanding requirements, many important features are incorporated in the modern conventional hot strip mills. Some of these are described below. Reheating furnace – Modern hot strip mills are equipped with energy efficient walking beam furnaces which are normally computerized controlled. These reheating furnaces uniformly heat the slabs to the target temperatures at the required production rates and without skid marks and without cold spots. These furnaces are capable of receiving cold or hot slabs as the charge material in the furnace. Descalers – Descalers are a must in hot strip mills for attaining good surface quality. Present day descalers employ state of the art nozzle technology with highly effective application of high pressure water (upto 400 bars). Descalers are...