نورد فلزات (rolling of metals)

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5لقاع” آه ومتلامك 3-8 ‏لكا‎ / a le MMe ea} تدارا ۱ * Cold rolling * Forces and geometry relationships in rolling ٠ 511770170 379 ‏5أق/ز/‎ 0] 10/|[779 /030: 901110 1365 ٠ ‏ات‎ Ce Hat) + Theories of cold rolling + Theories of hot rolling ۱ ne el a 

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Objectives + This chapter provides information on different types of metal rolling processes which can also be divided in to hot and cold rolling process. » Mathematical approaches are introduced for the understanding of load calculation in rolling processes. + Finally identification of defects occurring during and its ‏0009و‎ 2۲6 ۰ 1 

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into 1) hot rolling and 2) cold rolling. 9 : The process 5 plastically deforming metal by passing it between rolls. * Rolling is the / forming process, which pede high production and close control of final product. . Mi 3 ‏کت زیت‎ to high ا ا ‎the friction RU aoe Rd‏ .عع 2]]ناة أهاعممر ووو عورم ومالامها Note: rolling processes can be mainly divided 

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Introduction- Hot and cold rolling processes CM MC eo Cole nol ingots into 2۳0 ‏عاعاالط‎ ‎is generally done by hof-rolling. ‏از و۱‎ eile rolling into plate, sheet, rod, bar, ‏انه بعمام‎ Cold rolling * The cold-rolling of metals has foe NoMa cela Mae aa providing sheet, strip, foil with ‏ليب ب ات ينا‎ ‏یت ات سوت‎ ern ۱ tee 

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۱۱0۱۱۱۱۱ 112/115 ؤمأكأة 160ا0 تس دا 

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Terminology ۳ + Bloomis the product of first breakdown of ingot (eros a(x Se ‏ها ات تست‎ ‏بات‎ Cressi ‏كت ل‎ ea COR TLIO m ۰ Slab _ is the hot rolled ingot amy (cross sectional area > 100 cm? and with a width > rolling Ec) Pema aoc Ue MUIR RU eto) ات ار ل ل ان ‎products‏ * Strip _ is the product with a thickness < 6 mm and width < 600 mm. 

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ولاه القالا Upper Rack ‏ام‎ Up Ral «۹ Lower Rage 

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Method to reduce roll deflection Backing bearing —_ Housing Driven roll -—— Driven roll Bearing shaft First Second. intermediate intermediate 7 roll roll . 5 Strip Driven roll ~~ Work roll Driven roll 

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1۷۵/۵1 5۳۳2۳۱96۵۱ 01 ۲01۱۵۲5 10۲ ۲۵۱۱/۱۵ ۱/6 تست ترا ‎eae cd‏ هه ما 0ع۲نداجر ‎۱ ۳ ‏ترا ‎atl‏ مر وا ۳ ‏| ‏واله؟ منماء هط ‎ ‏عط درق عارهبلا :71 ‏00 ‏رطا وااه؟ عجا «اوناهرطة و ‎Ce ‏م‎ ۵۴ ۳۵۹۵ n ‎ ‎ome ed ee ec] ed eed rolls. ‎ ‎Consist of upper and ۱ ‏وت‎ nee ell ice aad rotates by friction. ‎ 

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Typical arrangement of rollers for rolling mills Continuous rolling PaO EB ‏نیا‎ 200 each set is called a stand. Sau Re Tevet ۵7۳6۲6۲ ‏عع)[۷6/۵۵‎ 2 001 stage in the mill. A four stand continuous mill or tandem mil. Peete ‏ا‎ hd each stand is equal to the output speed of preceding stand. * The uncoiler and windup reel not only feed the stock into the rolls and coiling up the final product but also provide back tension and front tension to the strip. the final product but also provide back tension and front tension to the strip. 

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او ‎surrounded by a large number of planetary rolls.‏ لوت حت لع وات اتا ۱2 31اناعءك 3 أناه 5مع51/8 ]ا 35 5|360 عطأا م1 ‎path between the backing rolls and the slab.‏ ٠ ‏عالقا ما قع5هع 6/1]5: /[7/قاع7قام أه ]لقم لاعوع كم‎ contact with the work piece, another pair of rolls makes contact and repeat that reduction. ٠ ‏متأ را ع1‎ 02 series of small reductions by each pair of rolls. Therefore, the planetary mill can hot reduces a slab directly to strip in one pass through the mill. + The operation requires feed rolls to introduce the slab into the mill, and a pair of on the exit to improve the surface finish. Planetary mill 

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Rolling mills Rolling mill is a machine or a factory for shaping metal by passing it through rollers A rolling mill basically consists of ‏تس‎ ات ‎these parts‏ ات رها رات ار ‎a drive (motor) for applying power to the rolls and controlling the speed‏ + ‎ ‎+ Requires very rigid construction, large motors Modern rolling mill 0 ‏لعا‎ oN Acari eA) ‎power (MN). ‏| كك يي ع لكت ‎Flr Meola ate manly‏ ‎ ‎ ‎oes} ‎+ engineering design 5 8 palate 9 + Huge capital investment ‎ ‎ ‎ ‎ ‎ ‎ ‎ 

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Different types of rolling processes There are different types of rolling processes as listed below; * Continuous rolling BCU ‏ال‎ ‎CREB meme Ome ‏ا‎ * Ring rolling Oe ‏ل‎ CM ee el meet ale Rem Lace Le | * Thread rolling 

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156 ‏لة ات یات رت‎ increase in length and with little increase in width. + The material in the centre of the sheet is constrained in the z direction (across ‏(أعع50 عط ]0 اللا عط‎ 300 6 on each side of ۱ ‏کات کت ات رات‎ ‏رت کیت هن تیا‎ ‎ae ees) elled‏ ره نیرازس زیر ‎Eee BC Beet ney‏ ‎longer and not wider.‏ ‎ ‎+ Otherwise we would need the width oO ‏ات‎ to roll down a steel ingot to make tin plate! ‎ 

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+ Using circular wedge rolls. + Heated bar is cropped to length and ‏.15ا0؟ معع ع0 یت ات۱‎ ٠» OER ON eRe i.e (ote Transverse rolling 

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٠ ‏ا و0اااه؟ لامع أه عمط اداععمة لم‎ which flat slap is progressively bent ‏ماما‎ 1 s by passing it through a series Bac oe + No appreciable change in the thickness of the metal during 00 process. + Suitable for producing moulded 5601008 ‏۲اناوع۳۳] عج طعناو‎ 0 channels and trim. 

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A variety of sections can be produced by roll forming process using a series of forming rollers in a continuous method to roll the metal sheet to a specific shape Seo uve ‏ات‎ Ce - partition beam - ceiling panel - roofing panels. - steel pipe - ‏35م 6/أ01770أنا‎ - household appliances رع الاأأاانا؟ اهاعم - - door and window frames - other metal products. 

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Ring rolling 5 Sel esas} 

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* Ring rolls are used for tube rolling, ‏وم‎ ۵9۰ + Ring rolls are made of spheroidized ‏وا اروت ات زره ت۱۱‎ alloy cast steel base. ee ‏انا اد‎ ee ee | ۱۱ ee) 

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اه ترا ‎between a free turning inside rol anda‏ ات تفت أعممتطا ممناععة عط رات سا ات9 ‎while increasing the ring diameter.‏ wav shape co kr Relative strain in ring can LD. ROLL 0.0. ROLL 

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Ring Rolling ‘ler ro8 — \ Edging rols ‏یک‎ 10 2) ۰ To make a larger and thinner ring from the original ring * Usually a hot rolling process for large rings and cold rolling for small rings + Typical applications: bearing races, steel tires, rings for pressure vessel. 

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ec ‏اس‎ is introduced between the rolls and compacted into a ’, which is subsequently sintered and subjected to further hot-working and/or cold working and annealing cycles. Powder rolling wil - Cut down the initial hot-ingot breakdown step (reduced capital investment). - Economical - metal powder is cheaply produced during the extraction process. - Minimise contamination in hot-rolling. Provide with a minimum of preferred orientation. 

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roughing mit Lode © Continuous Hot rolling Finishing casting ‘ail coils of hot rolled aver cooling ‘uid rollers ‎(iM oNs\muirete ties 9‏ اا اه ‎rolling mills within the same process.‏ ‎‘wa + Usually for steel sheet production. 

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Thread rolling See eee coke au Ue ema Hef blank. As the blank rolls against the in-feeding die faces, the material is displaced to form the roots of the thread, and the displaced material flows radially CL ROU UR ‏ا‎ SPUR ‏ل‎ oe eel ad ‏ما ععاوام واه‎ ۲ 16 6305. ٠ ‏ها لداعت آ0 /نا10! لهتكاج عطأ لاط لعمم1 ذأ لجعرطأا ع1‎ ‘the work piece. The grain structure of the material is not ‏لبا‎ to follow the thread form. + Rolled threads are produced in a single pass at ‏رت کت‎ oMeN LK CMa CRN Une cede mul) a cut thread. It has a greater resistance to arene UW RM ote Melty eee strength. Also the surface is burnished and work ‏سا ی و گت‎ ead 

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022220110001 تا ل ل ‎OF‏ increasing length due to a reduction of (6 ۱ ‏یر هت‎ RU ROR Kale de a) ‏تاك تلن‎ 4 Deeg) سا ل ی ۱ ‎fe) Aa Recon eee ON arte te)‏ ‎Ue om‏ Hot rolled coil produced on strip mill 

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= Cold rolling is carried out under ‏اها۲60/۵‎ elm Care 0 introduces work hardening. + The starting material for cold-rolled steel sheet is pickled hot-rolled breakdown coil Sire ‏ار ارات رای یهار‎ + The total reduction achieved by cold-rolling generally will vary from about 50 to 90%. + The reduction in each stand should be distributed uniformly without falling much below the maximum reduction for each pass. + Generally the lowest percentage reduction is taken place in the last pass. ۳ to permit better control of flatness, gage, and surface finish. 

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Cold-rolling * Cold rolling provide products with ‏الها مأ عنال) 11111517 ع 13آنا5 101املا5‎ temperature > no oxide scales) + Better dimensional tolerances compared with hot-rolled products due ‏ما‎ ۱۵55 106۲۲۱2۵۱ 0۰ ۱93۶۰ ‏ات ات‎ eR ice) hot-rolled strip, or in the case of certain copper alloys itis cold-rolled directly from the cast state. Cold rolled metals are rated as ‘temper’ Semel (ema ‏دا‎ ‎harden, still more workable. ٠» ©2117 ‏وت 35 0 06101131100 05 30001004 تعحاوانا : 10جذ!‎ normal to rolling direction without fracturing + Half hard : Can be bent up to 90°. ‏الل ل ان الحا لك ل لتك نفك‎ Can be bent up to 45°. Cold rolled strips 

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Fundamental concept of metal rolling 1( 6 ‏ع5 300 5ااه؟ عط عع بطع أع112ره‎ metal is a part of a circle. 2( 156 ‏لعمء‎ aca) theory, but in reality 42 varies along the arc of ‏کرو‎ 3) The ee is considered to deforn ‏کت 1 ءام‎ rolling. 4( 6 Mero telnet eli) 6۲ 2 In practical the volume might ec eR ae Roker Mold lee ‎rolling direction‏ درز ‎ee‏ سا در( ‎and n 01‏ ‎ ‎ ‎ ‎ey 20۳۵۱ 10 ‏عط‎ ‎rolling direction is not distorted. ‎ 

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Problems and defects in rolled products Defects from cast ingot before rollin Defects other than cracks can result from defects introduced during the ingot stage of production. » Porosity, cavity, blow hole occurred in the cast ingot will be closed up during the rolling process. + Longitudinal stringers of non-metallic inclusions or pearlite banding are related to melting and solidification practices. In severe cases, these teckel ROMO ‏يي‎ cecilia Nace ecm ‏طاودهتاع‎ ۱ 6 ‏تا یر‎ 

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Defects during rolling | There are two aspects to the problem of the shape of a sheet. ولح ا ل ا لك لل ا ا ‎controlled with modern gage control system.‏ fa 7 ‎cert‏ ل يل ف للك تنك ‎ ‎ ‎ 

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+ The roll gap must be perfectly parallel to produce sheets/plates ‏اس یت سل‎ 5 ‎LiKe 8)‏ لل ل لك “لك رز ‎elongation of one part in 10,000 between different locations in the‏ ‎sheet can cause waviness.‏ ‎More elongated More elongated in along edges the centre ‎Perfectly flat ‎ 

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« Thicker centre means the edges would be plastically elongated more than the centre, normally called / es. * This induces the residual stress pattern of compression at the edges 200 ‏اع امع 1۱6 وطما2 طم9ععا‎ ‎elec eet a (d) or edge‏ ار .(©) 200 ص0 ۱ 

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+ Thicker edges than the centre means the centre would be plastically elongated more than the edges, resulting in lat 920 «The residual stress pattern is now under compression in the centreline and ۱ eck oh + This may cause edge cracking (c), 8) As 

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1116/1655 117625101811111] أ1١‎ 0111105 005 000 Neko by using two opposing ‏تاو رت‎ aimed at opposite sides of a ]21961 76 560507 ۱22۵/95 ‏را‎ 856/1507 separation distance to yield a eee ee eeu cold strip mills ۷ 0۷ ۱6251۲60 5 ۲1611695 ۰ ارفا ةا thickness following the first stand is usually fedback to adjust the gap Aine Rm URIS eC ae + Gauge control in subsequent stands usually is achieved by controlling the ‏حو “ل يع ان »لعن ل 1 لاله‎ relative roll speed in successive stands or the coiler speed. * Gauge control through control of ۱۱۸۱۰۸۱۰۱۰۱۰ ‏دا‎ ety time than control through change in roll setting. 

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Torque and power ۱۳۱۸۰۱ ‏رت‎ eer) ROE Rec m en ue eS ‏ات راتس‎ olay لام 300 5اا0؟ عط ها ار ۱2۰۱۰۱۵ نت رات The power is spent principally in four ways 1) The energy needed to deform the metal. 10168 /003ل©1] 6لا 01/6/0070 10 86080 /إ60610 16 (2 3) The power lost in the pinions and power-transmission system. 4) Electrical losses in the various motors and generators. 

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A picture of the scale-down rolling mill used in the lab: Adjusting, Screw Rolls Housing/ Stand 26 

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Equipment Calibration numbers 

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Roll Piercing — Compressive fore ‏نی‎ 0 : C2 Tensile stiesses \ ‏سر‎ ‎= 0 ‏للجم بلسي‎ 7 \— Finished tube fa) + Hot working process * Production of Seamless thick-wall tubes 

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