Experimental Study of Interfacial Heat Flux and Surface Temperature by Inverse Analysis with Thermocouple (Fully Embedded) during Hot Steel Strip Rolling

International Journal of Solids and Structures

2015

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a b s t r a c tIn this paper a semi-analytical inverse Cauchy problem is presented for a finite cylinder with a cylindrical hole under the surface called the detecting roll. Applications to latent flatness defect detection during rolling process are considered. A steel strip wraps at a known angle around the detecting roll. The presented inverse method aims at evaluating the residual stress profile of the strip. The inputs are the displacements and free surface traction at the hole surface and the outputs are the resultant forces per unit length in the contact between the strip and the roll, thus by equilibrium of the strip the residual stress profile is inferred. This paper is based on plane complex elasticity with conformal mapping techniques. Several 2D-computations are performed at several axial positions. This work is theoretical, the measurement device is not available and technical issues are not broached. Some numerical examples with synthetic data are provided in order to evaluate accuracy and noise sensitivity. Results encourage further investigations and technical developments.

Section: Introductionmentioning

confidence: 96%

Inverse Cauchy method with conformal mapping: Application to latent flatness defect detection during rolling process

International Journal of Solids and Structures

2015

Self Cite

“…Aluminium killed grade strips (initial width/thickness = 100mm/60mm) were rolled on a hot pilot mill in 2-high configuration with the top work roll equipped with slot and drilled temperature sensors (work roll outer radius = 234.5 mm). The distance d of the slot sensor 'A' and the drilled sensor C1 have been evaluated respectively to 0.51 mm and 0.58 mm under roll surface with a calibration procedure using hot water sprayed on each sensor [2]: inner roll radius = outer roll radius -sensor's distance to roll surface. Temperature signals during rolling have been stored using a data acquisition system (16 bits-sampling frequency: 3-5 kHz).…”

Section: Hot Pilot Mill Trialsmentioning

confidence: 99%

“…2 different heat transfer and temperature models are used to exploit roll temperature sensors: -model n°1: a 2D semi-analytical temperature evolution model [2][3] 5) because of air in the sensor. -model n°2: a numerical finit difference roll gap heat transfer model for the strip coupled with a finit difference 1D roll temperature evolution model [4] is used in direct mode: the roll surface boundary condition HTC roll-bite is used as input of the roll temperature model to match predicted and measured temperatures at inner roll radius.…”

Section: Heat Transfer Modelsmentioning

confidence: 99%

Analysis of Roll Gap Heat Transfers in Hot Steel Strip Rolling through Roll Temperature Sensors and Heat Transfer Models

Legrand

Labbe

et al. 2012

KEM

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Analysis of roll gap heat transfers in hot steel strip rolling through roll temperature sensors and heat transfer models. Key Engineering Materials, 2012Materials, , 504-506, pp.1043Materials, -1048 Abstract. This paper presents an analysis of roll bite heat transfers during pilot hot steel strip rolling. Two types of temperature sensors (drilled and slot sensors) implemented near roll surface are used with heat transfer models to identify interfacial heat flux, roll surface temperature and Heat Transfer Coefficient HTC roll-bite in the roll bite. It is shown that: -the slot type sensor is more efficient than the drilled type sensor to capture correctly fast roll temperature changes and heat fluxes in the bite during hot rolling but its life's duration is shorter. -average HTC roll-bite is within the range 15-26 kW/m 2 /K: the higher the strip reduction (e.g. contact pressure) is, the higher the HTC roll-bite is.-scale thickness at strip surface tends to decrease heat transfers in the bite from strip to roll. -HTC roll-bite is not uniform along the roll-strip contact but seems proportional to contact pressure. -this non uniform HTC roll-bite along the contact could contribute to decrease thermal shock (so roll thermal fatigue) when the work roll enters the roll bite, in comparison to a uniform HTC roll-bite . -Heat transfer in the roll bite is mainly controlled by heat conduction due to the huge roll-strip temperature difference, while heat dissipated by friction at roll-strip interface seems negligible on these heat transfers.

“…Two different heat transfer models are used to analyze roll temperature sensors measurements: -model n°1: a 2D semi-analytical temperature evolution model [2][3] As the model is analytical, it considers thermal properties independent of temperature: (thermal conductivity) = 17.3 W/m/K and D (thermal diffusivity) = 4.2 mm 2 /sec. These values, determined by calibration, correspond to average thermal properties of solder material used in the slot sensor.…”

Section: Heat Transfer Modelsmentioning

confidence: 99%

Characterization of Roll Bite Heat Transfers in Hot Steel Strip Rolling and their Influence on Roll Thermal Fatigue Degradation

Legrand

Horský

et al. 2013

KEM

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Abstract.A temperature sensor with a thermocouple placed at ~0.5 mm from roll surface is used in hot rolling conditions to evaluate by inverse calculation heat transfers in the roll bite. Simulation analysis under industrial hot rolling conditions with short contact lengths (e.g. short contact times) and high rolling speeds (7 m./sec.) show that the temperature sensor + inverse analysis with a high acquisition frequency (> 1000 Hz) is capable to predict accurately (5 to 10% error) the roll bite peak of temperature as well as the roll surface temperature evolution all around the roll rotation. However as heat flux is more sensitive to noise measurement, the peak of heat flux in the bite is under-estimated (20% error) by the inverse calculation and thus the average roll bite heat flux is also interesting information from the sensor (these simulation results will be verified with an industrial trial that is being prepared). Rolling tests on a pilot mill with low rolling speeds (from 0.3 to 1.5 m./sec.) and strip reductions varying from 10 to 40% have been performed with the temperature sensor. Analysis of the tests by inverse calculation show that at low speed (<0.5 m./sec.) and large contact lengths (reduction: 30 to 40%), the roll bite peak of heat flux reconstructed by inverse calculation is correct. At higher speeds (1.5 m./sec.) and smaller contact lengths (reduction : 10-20%), the reconstruction is incorrect: heat flux peak in the bite is under-estimated by the inverse calculation though its average value is correct. The analysis reveals also that the Heat Transfer Coefficient HTC roll-bite (characterizing heat transfers between roll and strip in the bite) is not uniform along the roll bite but is proportional to the local rolling pressure. Finally, based on the above results, simulations with a roll thermal fatigue degradation model under industrial hot rolling conditions show that the non-uniform roll bite Heat Transfer Coefficient HTC roll-bite may have under certain rolling conditions a stronger influence on roll thermal fatigue degradation than the equivalent (e.g. same average) HTC roll-bite taken uniform along the bite. Consequently, to be realistic the roll thermal fatigue degradation model has to incorporate this non-uniform HTC roll-bite .2