PowerPoint PresentationSlide 2Flat Rolling ProcessFrictional ForcesFlat-Rolling PracticeFlat-Rolling Practice Con’tDefects in Rolled Plates & SheetsOther CharacteristicsSchematic Illustration of Various Roll arrangementsSchematic Illustration of various roll arrangements : (a) two-high; (b) three-high; (c) four-high; (d) cluster millShape-Rolling OperationsStages in Shape Rolling of an H-section part. Various other structural sections such as channels and I-beams, are rolled by this kind of process.Ring RollingRING ROLLINGThread RollingThread Rolling Con’tProduction of Seamless Pipe & TubingContinuous Casting & Integrated Mills & MinimillsContinuous Casting & Integrated Mills & Minimills Con’tSpray Casting : In spray casting the molten metal is sprayed over a rotating mandrel to produce seamless tubing and pipeTHE ENDChapter 13Rolling of MetalsThis chapter describes Flat rolling  Shape rollingProduction of seamless tubing & pipeRolling – process of reducing the thickness of a long work piecePlates – having thickness greater than 6mmSheets – generally less than 6mm thickIntroductionFlat Rolling ProcessFlat RollingFlat Rolling Process•Metal strip enters the roll gap•The strip is reduced in size by the metal rolls•The velocity of the strip is increased the metal strip is reduced in size•Factors affecting Rolling Process–Frictional Forces–Roll Force and Power RequirementFrictional ForcesFriction Forces acting on strip forces•Max Draft • h0-hf = µ2RRoll Force•F= W0.L.Yavg•L sqrt{R(h==o-hf)}Flat-Rolling PracticeFlat-Rolling Practice•Hot rolling–The initial break down of an ingot –Continuously cast slab–Structure may be brittle–Converts the cast structure to a wrought structure•Finer grains•Enhanced ductility–Reduction in defects•Continuous Casting –Is replacing traditional methods–Faster & betterProduct of the first hot-rolling operation - Bloom or slab –Square cross section of 150mm (6in) on one side–Processed father by shape rolling•I-beams•Railroad railsFlat-Rolling Practice Con’t•Billets – smaller than blooms and rolled into bars and rods•Cold rolling –carried out at room temperature–Produces sheet and strip metal–Better surface finish – less scale•Pack rolling – when two or more layers of metal are rolled togetherChanges in grain structure during hot-rollingDefects in Rolled Plates & SheetsDefects in Rolled Plates & Sheets•Undesirable–Degrade surface appearance–Adversely affect the strength•Sheet metal defects include:–Scale, Rust, Scratches, Gouges, Pits, & Cracks–May be caused by impurities and inclusions•Wavy edges – result of roll bending •Alligatoring – complex phenomenonOther CharacteristicsOther Characteristics•Residual stresses – produces: –Compressive residual stresses on the surfaces–Tensile stresses in the middle•Tolerances–Cold-rolled sheets: (+/- ) 0.1mm – 0.35mm–Tolerances much greater for hot-rolled plates•Surface roughness –Cold rolling can produce a very fine finish–Hot rolling & sand have the same range of surface finish•Gauge numbers – the thickness of a sheet is identified by a gauge numberSchematic Illustration of Various Roll arrangementsSchematic Illustration of Various Roll arrangementsSchematic Illustration of various roll arrangements : (a) two-high; (b) three-high; (c) four-high; (d) cluster millShape-Rolling OperationsShape-Rolling Operations•Various shapes can be produced by shape rolling–Bars–Channels–I-beams–Railroad rails•Roll-pass design requires considerable experience in order to avoid external and internal defectsStages in Shape Rolling of an H-section part. Various other structural sections such as channels and I-beams, are rolled by this kind of process.Ring RollingRing Rolling•A thick ring is expanded into a large diameter ring–The ring is placed between the two rolls –One of which is driven–The thickness is reduced by bringing the rolls together•The ring shaped blank my be produced by:\–Cutting from plate–Piercing–Cutting from a thick walled pipeVarious shapes can be produced by shaped rolls•Typical applications of ring rolling:–Large rings for rockets–Gearwheel rims–Ball-bearing and roller-bearing races•Can be carried out at room temperature•Has short production time•Close dimensional tolerancesRING ROLLINGRING ROLLING(a) Schematic illustration of Ring-rolling operation. Thickness reduction results in an increase in the part diameter. (b) Examples of cross-sections that can be formed by ring-rollingThread RollingThread Rolling•Cold-forming process•Straight or tapered threads are formed on round rods by passing the pipe though dies•Typical products include–Screws–BoltsThread Rolling Con’tThread Rolling Con’t•Threads are rolled in the soft condition•Threads may then be heat treated, and subjected to final machining or grinding•Uncommon or special-purpose threads are machinedProduction of Seamless Pipe & Tubing•Rotary tube piercing (Mannesmann process)–Hot-working process–Produces long thick-walled seamless pipe–Carried out by using an arrangement of rotating rolls•Tensile stresses develop at the center of the bar when it is subjected to compressive forcesContinuous Casting & Integrated Mills & MinimillsContinuous Casting & Integrated Mills & Minimills•Continuous casting–Advantages•Highly automated•Reduces product cost•Companies are converting over to this type of castingContinuous Casting & Integrated Mills & Minimills Con’tContinuous Casting & Integrated Mills & Minimills Con’tIntegrated Mills utilize everything from the production of hot metal to the casting and rolling of the finished productMinimills–Scrap metal is melted–Cast continuously–Rolled directly into specific lines of products–Each minimill produces one kind of rolled product•Rod•Bar•Structural steelSpray Casting : In spray casting the molten metal is sprayed over a rotating mandrel to produce seamless tubing and pipeTHE ENDTHE