Modelling heat transfer during hot rolling of steel strip

Colás, Rafael

doi:10.1088/0965-0393/3/4/002

Cited by 67 publications

(39 citation statements)

References 13 publications

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“…Other authors [25][26][27][28][29] use empirical equations that incorporate the contribution from convection and radiation. Most researchers consider that the oxide layer is made exclusively of wustite, and the heat transfer rate from the strip to the surrounding media is computed through a thermal barrier with the thermophysical properties of this species.…”

Section: Modellingmentioning

confidence: 99%

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Modelling the Spalling of Oxide Scales During Hot Rolling of Steel Strip

et al. 2008

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Production of hot rolled steel strip is carried out at temperatures at which oxidation is prone to occur. The oxide crust is subjected to stresses that are originated while growing or are due to the difference between the thermal expansion coefficients of steel and oxide. It is considered that the oxide crust will be in tension when the temperature at the surface of the steel increases and in compression when it decreases. These stresses may cause cracking, buckling and spalling of the oxide. Oxidation to hematite occurs very rapidly once the crust is detached from the surface of the steel, and, in some cases oxide dust clouds will be formed. A model was developed to predict the magnitude and nature of the stresses within the oxide layer considering the temperature changes that take place while the material is being rolled. The model predicts that the oxide crust will deform when compressed and may cause its spalling and, once this occurs it will be expected to form oxide dust clouds.

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Section: Modellingmentioning

confidence: 99%

“…Most researchers consider that the oxide layer is made exclusively of wustite, and the heat transfer rate from the strip to the surrounding media is computed through a thermal barrier with the thermophysical properties of this species. The heat flow through the oxide (H ox ) is then computed as [27]:…”

Section: Modellingmentioning

confidence: 99%

Modelling the Spalling of Oxide Scales During Hot Rolling of Steel Strip

et al. 2008

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“…7) The phenomena taken into account to describe thermal changes during this process are radiation and conduction to the surrounding media, conduction to the work rolls, forced convection and boiling of water used for descaling and interstand cooling, adiabatic heating produced during deformation and heat conduction within the stock. The finite difference model described elsewhere 9,[14][15][16][17] is used in this work, the cross-sectional area of the strip is divided into small cells of equal size to approximate the equations for conduction. The model takes advantage of symmetry, so computations are carried out in only one quadrant after assuming equal condition on top and bottom and lateral surfaces.…”

Section: Modellingmentioning

confidence: 99%

“…The general discussion on the thermal portion of the model, and the mathematical expressions used to compute the evolution can be found elsewhere. 9,[14][15][16][17] The procedure used to determine microstructural evolution evaluates whether or not dynamic recrystallization was achieved during a given pass depending on rolling conditions such as temperature, strain rate, reduction, etc. If the critical strain was surpassed, the dynamically recrystallized fraction and the corresponding grain size are calculated, allowing for metadynamic recrystallization during the interpass time.…”

Section: Modellingmentioning

confidence: 99%

Hot Rolling of Light Gauge Steel Strip

Zambrano‐Robledo¹,

Delgado²,

Guerrero‐Mata³

et al. 2003

ISIJ International

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Production of hot rolled thin gauge steel strip in a compact six-stand mill was studied by means of mathematical modelling and on site measurements. Data obtained during processing low carbon steel strip ranging from 1.06 to 2.68 mm in final outgoing thickness included speeds, reductions and separation forces at each of the six stands. The mean flow stress during rolling was calculated from the rolling loads, assuming adhesive conditions within the roll-gap, and by means of a mathematical model that accounts for strain hardening and the occurrence of various dynamic restoration phenomena during deformation. It was found that the values of the mean flow stress values, independently of the way they were obtained, varied as a function of both, strain rate and temperature, being possible to derive a unique formulation to describe their behaviour.

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“…Published heat-transfer simulations assume a constant HTC across the width of a sprayed product. 5,6 However, high-pressure flat-jet descaling nozzles are arranged in one or more rows because the product to be descaled is usually wider than the spray width of a single nozzle, and a more intense cooling occurs in the areas where the surface is sprayed with the water from more than one nozzle. 7,8 This area is called the overlap area as water streams from two adjacent nozzles, overlapping in the direction parallel to the product movement.…”

Section: Introductionmentioning

confidence: 99%

Overcooling in overlap areas during hydraulic descaling

Pohanka¹,

Votavová²

2016

Mater. Tehnol.

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The production and processing of high-quality grades of steel are connected with the oxidation at high temperatures. Unwanted scales are formed on the steel surface, which is usually heated to over 900°C. These scales are often removed by hydraulic descaling during the production. In most cases where long, flat products are produced, one row of descaling nozzles is used. As these flat jet nozzles are arranged in a row, the water spray from one nozzle interferes with the spray from the neighboring nozzles. This zone is called an overlap area and often even more scales remain here after the descaling process. An increased amount of the scales left behind results in a lower quality of a final product. A typical configuration with an inclination and twist angle of 15°was studied. Heat-transfer coefficients (HTC) and surface temperatures were measured in the overlap area and compared with the values obtained from undisturbed areas. It was found that the overlap area is grossly overcooled. The results were compared with a new configuration, where the twist angle was changed to 0°, and it was found that the overcooling was significantly reduced. The temperature measurement showed that an increased thickness of the scales in the overlap area can also be caused by surface overcooling because the scales change the material properties with the temperature, and they are therefore more difficult to remove. The new configuration with the twist angle of 0°seems promising for improving the quality of hydraulic descaling. Keywords: scales, steel, water, hydraulic descaling, overlapping, temperature, heat-transfer coefficient, surface Proizvodnja in predelava visoko kvalitetnih jekel je povezana z oksidacijo pri visokih temperaturah. Neza`eljene {kaje nastajajo na povr{ini jekla, ki se ga obi~ajno segreva nad 900°C. Te {kaje se med proizvodnjo pogosto odstranjujejo s hidravli~nim raz{kajanjem. V ve~ini primerov, ko se proizvaja dolge, plo{~ate proizvode, se uporablja ena vrsta raz{kajevalnih {ob. Ker so {obe s plo{~atim curkom razporejene v vrsti, vodni curek iz ene {obe vpliva na vodni curek sosednjih {ob. To podro~je se imenuje podro~je prekrivanja in pogosto na tem podro~ju ostane ve~{kaje po od{kajanju. Pove~an dele`preostale {kaje pa povzro~a slab{o kvaliteto kon~nega proizvoda. Analizirana je bila zna~ilna postavitev z naklonom in kotom zasuka 15°. Na podro~ju prekrivanja je bil izmerjen koeficient prenosa toplote (HTC) in temperatura povr{ine ter primerjava s podatki iz neprizadetih podro~ij. Ugotovljeno je, da so podro~ja prekrivanja mo~no podhlajena. Rezultati so bili primerjani z novo konfiguracijo, kjer je bil kot zasuka 0°in ugotovljeno je, da se je podhladitev mo~no zmanj{ala. Meritve temperature so pokazale, da je pove~ana debelina {kaje v podro~ju prekrivanja lahko tudi posledica podhladitve povr{ine, ker {kaja s temperaturo spreminja lastnosti materiala in se jo zato tudi te`je odstrani. Zdi se, da bo nova postavitev, s kotom zasuka 0°, omogo~ila izbolj{anje kvalitete hidravli~nega raz{kajanja.

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Modelling heat transfer during hot rolling of steel strip

Cited by 67 publications

References 13 publications

Modelling the Spalling of Oxide Scales During Hot Rolling of Steel Strip

Modelling the Spalling of Oxide Scales During Hot Rolling of Steel Strip

Hot Rolling of Light Gauge Steel Strip

Overcooling in overlap areas during hydraulic descaling

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