Formula for ‘Spread’ in Hot Flat Rolling

Abstract

An experimental investigation has been made to compare the elongation and the lateral spreading which occur during hot rolling of rectangular sections (i.e. slab or bar) between plain rolls. The results did not agree with predictions made from existing formulae for ‘spread’, and a new formula is presented which was derived empirically from the results and is of a form logically to be expected from a consideration of the factors likely to affect spread. This formula takes into account the ratio of the width of the stock to the length of the arc of contact during rolling, the ratio of the roll radius to thickness of the stock, the width to thickness ratio of the stock and the draft (or reduction). A modified formula has also been devised to take into account not only the geometrical variables but also changes in rolling temperature, steel composition, roll and bar surface condition, and speed of rolling (strain rate).