Crude Steel

Crude Steel  Crude steel is the term used for the first solid steel product which is produced during the solidification of liquid steel in a steel melting shop. Crude steel is part of saleable steel when it is supplied to customers for its use or for further processing. Crude steel is normally processed into finished steel either by rolling or by forging processes. World steel association also includes liquid steel which goes into production of steel castings under crude steel for statistical purpose. Various common types of crude steel products (Fig 1) include (i) ingot, (ii) slab, (iii) bloom, (iv) billet, (v) round, and (vi) dog bone section. Crude steel products are also semi-finished products since they need further processing for the production of finished steel. Fig 1 Common types of crude steel products Ingot Ingot is the product obtained by pouring liquid steel into cast iron mould of a shape appropriate for the subsequent processing generally by hot rolling or forging into semi-finished or finished products. The shape generally resembles a truncated pyramid or truncated cone. The side surfaces can be corrugated and the corners are more or less rounded. Depending on its subsequent conversion requirements, ingot can be dressed and/or hot scarfed or cropped. The usual cross section of ingot is square, rectangular, round, oval, or polygon. Ingots with square cross section are used for rolling into billets, rails and other structural sections, whereas, ingots with rectangular cross section, are generally used for rolling into flat products. These ingots usually have a width which is two times or higher than the thickness. Round ingots are used for the production of seamless pipes. Polygonal ingots are used to produce tyres, and wheels etc. Low capacity steel melting shops with induction furnaces produce very...

Roll Pass Design Jun18

Roll Pass Design

Roll Pass Design  Long products are normally rolled in several passes, whose numbers are determined by the ratio of the initial input steel material (square or round billet or bloom) and final cross section of finished product. The cross section area is reduced in each pass and form and size of the steel material being rolled gradually approach to the desired profile. Rolling is carried out between grooved rolls. Two opposite grooves in the collaborating rolls form a pass, which corresponds to a work piece’s cross section shape expected after the pass. After every pass, the cross section decreases and its shape becomes closer to a shape of the final product. Development of subsequent pass shapes and its proper location on the rolls is called the roll pass design. Roll pass design is an essential part of long product rolling process, since the long products are rolled between the shaped rolls in the long product rolling mills. Roll pass design generally means the cutting of grooves in the roll body through which steel to be rolled is made to pass sequentially to get the desired contour and size. The primary objective of the roll pass design is to ensure production of a product of correct profile within the tolerance limits, free of defects, with good surface quality and the required mechanical properties. In addition, economic condition must be achieved while rolling the product, for example, maximum productivity at the lowest cost, optimum energy utilization, easy working conditions for the rolling crew and minimum roll wear. Roll pass design is a set of methods for determining the dimensions, shape, number, and type of arrangement of rolling mill passes. Roll pass design also includes the calculation of pressing forces and their distribution on the roll passes. Several   passes are made for each section; a square or round billet or bloom acquires a specified form on each successive pass. The roll passes are designed to avoid excessive stresses in the steel being rolled, since such stresses can lead to the formation of cracks and other flaws. Roll pass design is based on the characteristics of initial input...