EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

Thanks to the extremely high stiffness of BSS Sizing Stands, we introduce the concept of “sizing stands” not only in special steel rolling mills (SBQ or alloyed steel), where the tolerance of the final products must be very tight, but also in rebar or wire rod rolling mills. This means a very high final product quality and a better product marketability, in fact the quality improvement does not involve higher production cost, even better, using BSS Sizing Stands, the operational cost are reduced. In the modern market, the flexibility in the production range becomes a relevant factor for the increase of market shares or even for the survival of the plant. Precisely for this purpose, BSS Sizing Stands gives the best flexibility to the rolling mill, in fact a rolling mill which was born for rebar production, could be easily upgraded and converted in to a special steel rolling mill, for the production of high valued steel grades. In the finishing mill, installing the BSS Stands with a shorter barrel length (monogroove) and tungsten carbide rolling rings, a final tolerance of 1/6 DIN can be easily achieved. Furthermore, a block of 3 BSS Stands, can be used as a sizing block, in Horizontal – Vertical – Horizontal arrangement, with a dedicated roll pass design made of oval – round – round sequence. All the bar sizes will be rolled and finished on the above mentioned block, adopting the “single family” roll pass concept, regarding the roughing, intermediate and pre-finishing mill. In wire rod mills, it is very important that the entry stock of the fast finishing block, have not only the required section and the required diameters as per roll pass design, but especially must have a constant section all along the whole bar. This is a key factor for the final quality of the wire rod, in fact if the section of the entry round bar is not constant, the low section reduction ratio in the finishing block may not be able to correct such shape defect, resulting in a poor quality which is not acceptable especially if the wire rod will be processed in a drawing lines. The installation of a 3-stands sizing block made of BSS Stands before the wire rod finishing block can be a very good solution for high quality wire rod production, guaranteeing an entry bar already with tight tolerance. The stiffness and the rigidity of the BSS Sizing Stands are due to: - Ring-holder shafts mounted on double support - Eccentric gap regulation, which allows the gap setting every 5 µm - Rolling load distributed on stand housing (monolithic), so the reaction surface is increased respect other common stands (no tie rods or cantilevered rolls) - Shorter stress path compared to housingless stands - Flexotorsional problems practically eliminated, due to the double support and the patented ring-holder shaft design - Unique design for the elimination of the bearings backlash, for a better control of the final tolerances and for a perfect bar shape. In fact, the backlash of the upper bearing of the Horizontal stands is eliminated as well as for both bearings in Vertical stands. Of course the rigidity of BS Stands means the achievement of very tight tolerance on the rolled stock, but it involves other advantages, such as: 1) Final product tolerance up to 1/6 DIN 2) For each billet, the rolled bar incoming and outgoing of each passes has almost the same section, also if the starting temperature of the billet is different (colder billet causes higher mechanical yielding and section changing), so the stress of the guides is reduced and their working life will be increased. 3) Possibility of performing thermo-mechanical rolling 4) Increased head-to-tail tolerance 5) Possibility to produce more added value products even in a rebar rolling mill, installing the BSS Sizing Block or replacing the rolling unit of existing stands with a new BSS rolling units designed in order to fit in the existing mills.