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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 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.
Roll pass design can be considered a collective exercise since it involves more than one roll. Long product hot rolling consists of passing a previously heated billet between two rolls repeatedly until the design thickness is obtained. In order to keep the temperature of the billet from dropping to a temperature which is not conducive to its plasticity, several passes are usually required. Thus, the number of passes taken to reduce the billet to its final dimensions is determined by the geometry of the grooves cut in the passes, which is why an optimized roll pass design is essential to the efficiency and quality of the rolling process.
In order to give the desired shape, size and finish to the product, roll pass design must consider many factors including elastic properties of the workpiece material, type of lubricant used, design of rolls, possible reduction in length per pass, total number of passes required, maximum diameter of the billet, etc. The roll pass design also specifies the directions of working, size and shape of the rolls, number of passes and the speed of operation.
Roll pass design is the most important factor in the process of long product rolling. The objective of the roll pass design is to ensure continual stable operation of the mills and must comply with the quality requirements of the product. The design should be capable of producing a product which has the required dimensional accuracy and surface finish, as well as the necessary mechanical properties. The roll pass design involves long calculations and requires good experience and technical know-how in order to come up with an optimized design.
Roll pass design is an art which has been developed over many years, depending upon the experience and skill of the mill designers. The various elements involved in roll pass design include selection of pass series, pass geometry, re-pass scheduling and roll grooving for each pass. Apart from roll pass design, other important aspects include roll barrel design, roll material selection, roll barrel surface finish, roll barrel heat treatment, mill housings and bearings, and mill drives.
Roll pass design is a complex task that forms an integral part of the long product rolling process. Professionals involved in roll pass design must possess a good understanding of the fundamentals of rolling theory. In addition, they should have a good command of the software used for roll pass design, as well as knowledge of advanced topics such as stress and strain analysis, friction and lubrication, profile modification, groove design and mill layout. Roll pass design is essential for producing the desired shape and size of the rolled product, and when done properly can significantly impact the efficiency of the rolling process.
