Rolling Process of reducing the thickness or changing the cross-section area of a long work piece by compressive forces.

accounts for about 90% of all metals produced by metalworking processes. forging operations produce discrete parts, where rolling operations produce continuous products. Engr 241

Plate > ¼” thick Ship hulls Bridges Boilers Engr 241

Sheet < ¼” thick Auto bodies Containers Appliances Engr 241

Aluminum foil candy wrapper = .0003” Engr 241

Gage numbers Smaller # = thicker sheet Engr 241

Ingot Initial form for rolling if not continuous Engr 241

Rolling Engr 241

Rolling Rolls Engr 241

Rolled Texture Engr 241

Unrolling and Straightening of Rolls (Maytag) Engr 241

Roll Loading Engr 241

Rolling Process Terminology (raw material) Bloom: square cross section of at least 6" on the side. (sheets) Billets: square cross section, smaller than bloom. (rod, pipe) Slab: rectangular in shape, rolled into plates and sheet. (rails, I-beams) Engr 241

Rolling Mills Two-high primary roughing (cogging mills). Engr 241

Three-high primary roughing (reversing mill). Direction reversed after each pass Engr 241

Four High & Cluster principal - (small diameter) rolls lower the roll forces and power requirements, but must be supported in order to reduce deflection. Engr 241

Rolling Mills Engr 241

Rolling Mills Tandem Rolling strip is rolled continuously through a number of strands (set of rolls with its own separate housing and controls) to smaller gauges with each pass. Group of Strands = train Engr 241

Roll Deflections forces cause roll deflection and roll flattening. Make roll dia larger at center Subject rolls to bending – apply moments at bearings Engr 241

Roll Deflections Forces can be reduced by: reducing friction. reducing contact area. smaller reductions per pass. rolling at elevated temperatures to reduce strength of material. Engr 241

Roll Materials Cast iron Cast steel Forged steel Aluminum Alloys Engr 241

Rolling Processes Flat-rolling hot or cold work (slabs, blooms, billets, or sheet metal). 3000 °F for refractory alloys. 2300 °F for alloy steels. 850 °F for aluminum alloys. Pack Rolling: two or more layers of metal rolled together (Al foil example) Engr 241

Flat-rolling (Cont.) Defects wavy edges – roll bends where strip is thinner along it’s edges Cracks – poor material ductility at the rolling temp alligatoring – non uniform deformation during rolling or defects in original billet Engr 241

Rolling Processes Engr 241

Shape Rolling structural shapes (I-beam, rails, etc.) requires specially designed rolls Engr 241

Ring Rolling ring (which is the part) placed between two rolls, to increase diameter. large rings for rockets, gearwheel rims, ball bearing and roller- bearing races, flanges, reinforcing rings for pipes, etc. Engr 241

Thread rolling cold-forming process where threads are formed on round rods by use of flat reciprocating dies which pass the part between them. no material loss. no cutting through grain line flow improves strength. Engr 241

Rotary Tube Piercing hot working process for making long, thick walled seamless tubing/pipe. round bar subjected to radial compressive forces causing tensile stresses toward the center of the bar. cavity forms from cyclic compressive stresses. Engr 241

Continuous casting Highly automated and productive Spray casting Molten metal sprayed over a rotating mandrel to produce seamless tubing and pipe Engr 241

Minimills Scrap – continuously cast and rolled into specific line of products located locally to scrap producer Engr 241