ch13 metal rolling

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Metal Rolling ProcessesMetal Rolling Processesand Equipmentand Equipment

Text Reference: “ManufacturingText Reference: “ManufacturingEngineering and Technology”,Engineering and Technology”,

, ,, ,Chapter 13Chapter 13



changing the cross section of a longchanging the cross section of a long

through a set of rollsthrough a set of rolls



FIGURE 13.1FIGURE 13.1 Schematic outline of various flatSchematic outline of various flat--rolling and shaperolling and shape--

.. ..



--

.. --process. (b) Friction forces acting on strip surfaces. (c) Rollprocess. (b) Friction forces acting on strip surfaces. (c) Roll

force,force, FF, and torque,, and torque, TT, acting on the rolls. The width of the, acting on the rolls. The width of the

, , , ., , , .

13.5.13.5.



FIGURE 13.3FIGURE 13.3 Schematic illustration of various roll arrangements: (a) four Schematic illustration of various roll arrangements: (a) four--highhighrolling mill showing various features. The stiffness of the housing, the rolls, and therolling mill showing various features. The stiffness of the housing, the rolls, and theroll bearings are all important in controlling and maintaining the thickness of the rolledroll bearings are all important in controlling and maintaining the thickness of the rolledstrip; (b) twostrip; (b) two--high mill; (c) threehigh mill; (c) three--high mill; and (d) cluster (or high mill; and (d) cluster (or Sendzimir Sendzimir ) mill.) mill.



--

Using smaller diameter rolls to reduce theUsing smaller diameter rolls to reduce thecontact areacontact area

Taking smaller reductions per pass to reduceTaking smaller reductions per pass to reduce

the contact areathe contact area

Rolling at elevated temperatures to lower theRolling at elevated temperatures to lower the

strength of the materialstrength of the material

Applying front and/or back tensions to the strip Applying front and/or back tensions to the strip



..

caused by roll forces. (b) Bending of rolls ground withcaused by roll forces. (b) Bending of rolls ground withcamber, producing a strip with uniform thickness throughcamber, producing a strip with uniform thickness throughthe stri width. Deflections have been exa erated for the stri width. Deflections have been exa erated for clarity.clarity.



FIGURE 13.5FIGURE 13.5 Spreading in flat rolling. Note that similar spreading canSpreading in flat rolling. Note that similar spreading can

..



FIGURE 13.6FIGURE 13.6 Changes in the grain structure of cast or of largeChanges in the grain structure of cast or of large--graingrain

wrou ht metals durin hot rollin . Hot rollin is an effective wa towrou ht metals durin hot rollin . Hot rollin is an effective wa to reduce grain size in metals for improved strength and ductility. Castreduce grain size in metals for improved strength and ductility. Cast

structures of ingots or continuous castings are converted to a wroughtstructures of ingots or continuous castings are converted to a wrought

structure by hot working.structure by hot working.



Hot Rollin leaves a rou h mill scale on surfaceHot Rollin leaves a rou h mill scale on surface

Remove HR mill scale by:Remove HR mill scale by: Acid etching (“pickling”) Acid etching (“pickling”)

Water blastingWater blasting

GrindingGrinding

finer surface finish (absence of mill scale)finer surface finish (absence of mill scale)

better dimensional tolerancesbetter dimensional tolerances

enhanced mechanical properties (due to strainenhanced mechanical properties (due to strainhardening)hardening)



Improved productivityImproved productivity

u u ee u uu u ee u u

Matte, satin sideMatte, satin side – – foilfoil--toto--foil contactfoil contact hiny, bright sidehiny, bright side – – oiloil--toto--roll contact due toroll contact due to

high contact stresses with polished rollshigh contact stresses with polished rolls



FIGURE 13.7FIGURE 13.7 (a) A method of roller leveling to flatten rolled sheets.(a) A method of roller leveling to flatten rolled sheets.

..



FIGURE 13.8FIGURE 13.8 Schematic illustration of typical defects in flat rolling:Schematic illustration of typical defects in flat rolling:

a wav ed es; b zi er cracks in the center of the stri ;a wav ed es; b zi er cracks in the center of the stri ;(c) edge cracks; and (d) alligatoring.(c) edge cracks; and (d) alligatoring.



FIGURE 13.9FIGURE 13.9 (a) Residual stresses developed in rolling with small(a) Residual stresses developed in rolling with small--diameter diameter

rolls or at small reductions in thickness per pass. (b) Residual stressesrolls or at small reductions in thickness per pass. (b) Residual stresses

-- ..Note the reversal of the residual stress patterns.Note the reversal of the residual stress patterns.



number number The smaller the number the thicker the sheetThe smaller the number the thicker the sheet

Several numbering systems are used,Several numbering systems are used,

de endin on t e of sheet metal beinde endin on t e of sheet metal beinclassified (steel, copper, aluminum, etc.)classified (steel, copper, aluminum, etc.)

Rolled sheets of nonRolled sheets of non--ferrous material are alsoferrous material are also

identified by thickness changes during rolling,identified by thickness changes during rolling,such as ¼ hard, ½ hard, etc.such as ¼ hard, ½ hard, etc.



FIGURE 13.10FIGURE 13.10View of a rollin mill.View of a rollin mill. Source:Source: Courtes of Is at Inland.Courtes of Is at Inland.



FIGURE 13.11FIGURE 13.11 An exam le of a tandem An exam le of a tandem--rollin o eration.rollin o eration.



FIGURE 13.12FIGURE 13.12 Steps in the shape rolling of an ISteps in the shape rolling of an I--beam part. Variousbeam part. Various

other structural sections, such as channels and rails, also are rolled bother structural sections, such as channels and rails, also are rolled bthis kind of process.this kind of process.



FIGURE 13.13FIGURE 13.13 Two examples of the rollTwo examples of the roll--forging operation, also knownforging operation, also known

asas crosscross--rollin .rollin . Ta ered leaf s rin s and knives can be made b thisTa ered leaf s rin s and knives can be made b thisprocess.process. Source:Source: After J. Holub. After J. Holub.



FIGURE 13.14FIGURE 13.14 (a) Production of steel balls by the skew(a) Production of steel balls by the skew--rollingrolling

process. (b) Production of steel balls by upsetting a cylindrical blank.process. (b) Production of steel balls by upsetting a cylindrical blank.

..subsequently are ground and polished for use in ball bearings.subsequently are ground and polished for use in ball bearings.



FIGURE 13.15FIGURE 13.15 (a) Schematic illustration of a ring(a) Schematic illustration of a ring--rolling operation.rolling operation.

Thickness reduction results in an increase in the part diameter. (b)Thickness reduction results in an increase in the part diameter. (b)

rolling.rolling.



FIGURE 13.16FIGURE 13.16 ThreadThread--rolling processes: (a) and (b) reciprocating flatrolling processes: (a) and (b) reciprocating flat

dies; (c) twodies; (c) two--roller dies; (d) A collection of threadroller dies; (d) A collection of thread--rolled parts maderolled parts made

..Manufacturing Corp.Manufacturing Corp.



FIGURE 13.17FIGURE 13.17 (a) Features of a machined or rolled thread. Grain flow(a) Features of a machined or rolled thread. Grain flow

in (b) machined and (c) rolled threads. Unlike machining, which cutsin (b) machined and (c) rolled threads. Unlike machining, which cuts

,,strength because of cold working and favorable grain flow.strength because of cold working and favorable grain flow.



FIGURE 13.18FIGURE 13.18 Cavity formation in a solid, round bar and its utilizationCavity formation in a solid, round bar and its utilization

in the rotar tube iercin rocess for makin seamless i e andin the rotar tube iercin rocess for makin seamless i e andtubing. (See also Fig. 2.9.)tubing. (See also Fig. 2.9.)



FIGURE 13.19FIGURE 13.19 Schematic illustration of various tubeSchematic illustration of various tube--rollingrolling

without a mandrel; and (d) pilger rolling over a mandrel and a pair of without a mandrel; and (d) pilger rolling over a mandrel and a pair of

shaped rolls. Tube diameters and thicknesses also can be changed byshaped rolls. Tube diameters and thicknesses also can be changed by

other rocesses, such as drawin , extrusion, and s innin .other rocesses, such as drawin , extrusion, and s innin .



Process of reducin thickness or chan in crossProcess of reducin thickness or chan in cross

section by compressive forces applied through asection by compressive forces applied through aset of rollsset of rolls

Rolling Mills may have a variety of rollRolling Mills may have a variety of roll

configurations; threeconfigurations; three--high, tandem, etc.high, tandem, etc. Continuous casting into semiContinuous casting into semi--finished productsfinished products

has economic benefitshas economic benefits

,,with complete sequence of rolling and formingwith complete sequence of rolling and formingactivities. Minimills utilize scrap metal.activities. Minimills utilize scrap metal.

ch13 metal rolling

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