Introduction to Manufacturing Chapter 13: Rolling

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

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 Three-high Four High & Cluster primary roughing (cogging mills). Three-high primary roughing (reversing mill). 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 Rolling forces cause deflection and roll flattening. Crown: thicker in the center than the edges. Chamber: thicker in the edges than center. Spreading: increase of width after rolled. 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 (P. 327) wavy edges zipper cracks edge cracks alligatoring Engr 241

Rolling Processes Shape Rolling (P. 331) Ring Rolling (P. 332) structural shapes (I-beam, rails, etc.) requires specially designed rolls Ring Rolling (P. 332) 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

Rolling Processes Thread rolling (P. 333) 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

Rolling Processes Rotary Tube Piercing (P. 334) 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