Strip Temperature Research Articles

Assessing the stability of rolling

By plotting histograms and calculating the variation coefficient of the primary drive’s torque in the cells of a continuous rolling mill, the stability of the process may be assessed. The elastic torques and motor torques in cells 5–7 of the 1680 mill in strip rolling were measured simultaneously at OAO Zaporozhstal’, and the results were statistically analyzed. The motor’s electromagnetic torque reflects the frequency properties of the transient process in the mechanical system of the drive and the reaction to technological perturbations, such as variation in strip temperature. By superposition of the motor’s torque histograms and calculation of the torque’s variation coefficient, the stability of rolling in the cells of a continuous mill may be qualitatively and quantitatively estimated. Numerical estimates of the rolling stability are presented for strip batches with and without intermediate coiling devices.

A multiscale coupled Monte Carlo model to characterize microstructure evolution during hot rolling of Mo-TRIP steel

A multiscale modelling framework has been proposed to characterize microstructure evolution during hot strip rolling of transformation-induced plasticity (TRIP) steel. The modelling methodology encompasses a continuum dislocation density evolution model coupled with a lumped parameter heat transfer model which has been seamlessly integrated with a mesoscale Monte Carlo (MC) simulation technique. The dislocation density model computes the evolution of dislocation density and subsequently constitutive flow stress behaviour has been predicted and successfully validated with the published data. A lumped-parameter transient heat transfer model has been developed to calculate the average strip temperature in the time domain. The heat transfer model incorporates the effect of plastic work for different strain rates in the energy conservation formulation. A coupled initial value problem solver has been developed to integrate the system of stiff ordinary differential equations in the time domain to predict dislocation density and temperature profiles simultaneously. The temporal evolution of microstructure during hot rolling of TRIP steel is simulated by the MC method incorporating thermal and dislocation density data from the continuum models. Simulated microstructural maps, kinetics of recrystallization and grain size evolution have been generated in a 200×200 lattice system at different strain rates and temperatures. The simulation code has been implemented in a high-performance grid computing network. The predicted temporal evolution of grain size, recrystallized fractions and flow stress have been validated with the published literature and found to be in good agreement, confirming the predictive capability of the integrated model.

Study on Warpage of Strip in Continuous Annealing Line by Virtual Layer Method

The effects of various input parameters on the warpage of strip were investigated and discussed. Three theoretical techniques, including virtual layers method (VLM), energy balance method (EBM), and finite element method (FEM), were adopted to evaluate the distributions of plastic strain, temperature, and stress of the strip, respectively. The longitudinal residual warpage can then be calculated accordingly. It was found that the cooling condition in cooling section plays a key role on the residual warpage of strip, which is possibly to be controlled within an accepted range by applying a suitable cooling scheme in this section.

Intelligent Setting Method of Laminar Cooling Process for Hot Rolled Strip

In order to improve the control accuracy of the coiling temperature of strip in the laminar cooling process when working condition is varying, an intelligent setting method of the cooling water volume is researched in this paper. The strip coiling temperature mechanism model is built firstly. Secondly, the key model parameters are identified with case-based reasoning (CBR) technology to improve the model accuracy. Lastly, the cooling water volume setting method based the model is proposed where disturbance input method is applied. The simulation result showed that the proposed method can improve the strip coiling temperature accuracy when the operation condition is changing. The strip coiling temperature accuracy can be improved due to the CBR technology which can adjust the key model parameters according to the varying operation condition. So, the setting values based the improved model are adjusted with the changing working condition, with self-adaptive ability.

Influence of O2 – plasma ambience and growth temperature on the oxidation of Mo-metal and volatilization of oxides

In this communication, we investigated role of the oxygen plasma on the oxidation of Mo strip surface (source of Mo) and volatilization of formed oxide species. Molybdenum oxide thin films are deposited on Si substrate simultaneously by using the volatilized oxide species as vapor source. A special setup is designed to create stable discharge oxygen plasma. Both the Mo strip surface and oxide films deposited on Si substrates at different temperatures are characterized independently. The presence of well indexed and intense peaks corresponding to MoO3 and Mo8O23 oxide phases in x-ray diffraction (XRD) patterns of metals strips, heated at different temperatures in oxygen plasma ambience has been considered as proof of oxidation of Mo-strip surface. The reduction in peaks intensity with increase in metal strip temperature indicates high rate of oxidation and oxide volatilization. It is observed that film formation on silicon substrate could not take place without oxygen plasma even at 500ºC. The scanning electron microscopy (SEM) studies of Mo strips as well as the films deposited on Si substrates, at different temperatures are showing the modifications in surface morphology and agreed with the XRD results. Both Raman and FTIR observations of Mo strip are also in consonance with the XRD and SEM findings. The occurrence of oxidation of Mo metal and volatilization of oxide species at this low temperature 300ºC is reported for the first time.

Thermo-electromagnetic properties of a magnetically shielded superconductor strip: theoretical foundations and numerical simulations

Numerical simulations of thermo-electromagnetic properties of a thin type-II superconductor strip surrounded by open cavity soft-magnetic shields and exposed to an oscillating transverse magnetic field are performed by resorting to the quasistatic approximation of a vector potential approach in conjunction with the classical description of conduction of heat. The underlying definition of the superconducting constituent makes use of an extended ‘smoothed’ Bean model of the critical state, which includes the field and temperature dependence of the induced supercurrent as well. The delineation of the magnetic shields exploits the reversible-paramagnet approximation in the Langevin form, as appropriate for magnetizations with narrow Z-type loops, and considers induced eddy currents too. The coolant is envisaged as acting like a bath that instantly takes away surplus heat. Based on the Jacobian-free Newton–Krylov approach and the backward Euler scheme, the numerical analysis at hand is tailored to the problem of a high width/thickness aspect ratio of the superconductor strip. Assigning representative materials characteristics and conditions of the applied magnetic field, the main findings for a practically relevant magnet configuration include: (i) an overall rise of the maximum temperature of the superconductor strip tending to saturation in a superconducting thermo-electromagnetic steady state above the operating temperature, magnetic shielding lending increased stability and smoothing the temperature profile along the width of the superconductor strip; (ii) a washing out of the profile of the magnetic induction and a lowering of its strength, a relaxation of the profile of the supercurrent density and an increase of its strength, a tightening of the power loss density and a reduction of its strength, all inside the superconductor strip. The hysteretic ac loss suffered by the superconductor strip is seen to be cut back or, at most, to converge on that of an unshielded strip, thermo-electromagnetic coupling merely playing an insignificant part thereby.

Low-temperature vacuum stripping of CO2 from aqueous amine solutions using thin-film silicalite-filled PDMS composite membranes

Carbon dioxide (CO2) recovery by vacuum stripping technology using membranes was studied as an alternative to the desorption process at low temperatures (below 120°C) in conventional aqueous amine absorption process. Composite membranes were prepared by coating hydrophobic silicalite-filled polydimethylsiloxane (PDMS) layers on polyethylene (PE) porous supports and used as new membrane strippers for CO2 recovery to prevent the typical pore wetting problem of hydrophobic porous membranes. Aqueous 30wt% solutions of monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) were used as absorbents in the desorption process. CO2 fluxes were measured under various operation conditions, such as different vacuum pressures, stripping temperatures, CO2 loadings, types of amine solutions and operation time. CO2 stripping fluxes increased with increasing temperature and CO2 loading of amine solutions as well as with decreasing stripping pressures because of the enhanced upstream and downstream driving forces. CO2 stripping fluxes were much higher in the TEA and DEA solutions than in the MEA solutions. The thin-film silicalite-filled PDMS composite membranes showed excellent long-term stability in the vacuum stripping process when compared with porous polytetrafluoroethylene (PTFE) membranes.

Experimental study of the effect of spray inclination on ultrafast cooling of a hot steel plate

The ultrafast cooling that occurs during high mass flux air-atomized spray impingement on a hot 6 mm thick stainless steel plate has been studied experimentally in terms of the nozzle inclination between 0° and 60°. The average mass flux of water used in the study accounts to 510 kg/m2 s. The coolants used in the study are pure water and surfactant water of 600 ppm concentration. The initial temperature of the plate has been maintained at 900 °C, which is the temperature of a hot strip on run-out table in steel industry. The transient surface heat flux and temperature histories have been estimated by an inverse heat solver using measured temperature input data. Heat transfer results demonstrates that optimum cooling efficiency (~2.76 MW/m2, 194 °C/s) for pure water has been achieved at 30° nozzle orientation. The inclined nozzle has not been found beneficial when surfactant water is used as the coolant.

Study on Thermal Response to Instantaneous Heat Generation in LN2 Chamber for HTS-FCL

This paper describes the thermal response of a high-temperature superconducting (HTS) wire model to instantaneous heat generation in a pressurized liquid nitrogen chamber for an HTS fault current limiter. A dc impulse power input to a stainless steel strip is adopted to simulate the quench state of the HTS wire. The test sample is submerged in the liquid nitrogen, which maintains a 77 K temperature with operating pressures of 101, 250, 400, and 600 kPa. Three different levels of dc current are supplied to the test sample during 50 ms for each operating condition. The boiling phenomena are captured with a high-speed camera and the surface temperature of the sample strip is measured to investigate the recovery process. From the captured video, the suppression of bubble generation is clearly observed as increasing operating pressure, especially for the lower heat flux condition. From the measurement of temperature, temperature rise of sample strip during heat generation decreases with increasing operating pressure except for the higher heat flux. For the recovery process, increasing operating pressure delays the recovery of the sample strip, but recovery time is within a few seconds for all cases.

Three-Dimensional Finite Element Based Analysis of the Strip Temperature Distribution in Finishing Mill of a Hot Strip Mill

Three-Dimensional Finite Element Based Analysis of the Strip Temperature Distribution in Finishing Mill of a Hot Strip Mill

Efficient CO2 absorption and low temperature desorption with non-aqueous solvents based on 2-amino-2-methyl-1-propanol (AMP)

In the present study, an efficient process for CO2 capture using some AMP–alkanolamine blends, namely DEA, MDEA, MMEA, DIPA, in non-aqueous solvents has been described. The solvents used are mixtures of ethylene glycol or 1,2-propandiol with either methanol or ethanol. Additionally, either pure 1-propanol or diethylene glycol monomethyl ether have been also employed. Throughout the whole set of experiments, the amine solutions were continuously circulated in a closed cycle between the absorber (set at 20°C) and the desorber (set at 65, 70, 75, 80°C). The CO2 absorption efficiency at equilibrium is in the range 73.1–95.9%. The carbon containing species in the amine–CO2–alcohol equilibria were analyzed by 13C NMR spectroscopy showing that they originate from alcohol and/or amine carboxylation. The AMP–DEA–1-propanol–CO2 system gives a solid compound that has been identified as the carbamate derivative of AMP, [(AMPH)(AMPCO2)], from its 13C solid state NMR spectrum and confirmed by single crystal X-ray structure determination. [(AMPH)(AMPCO2)] instantaneously dissolves in methanol, ethanol and ethylene glycol affording the respective monoalkyl carbonate. The lower stripping temperature of the studied absorbents offers several potential advantages with respect to conventional aqueous solutions of the same alkanolamines, yet preserving comparable efficiency.

Study on Water-Based Paint Stripper for Tinplate

A novel water-based paint stripper was prepared for white, metallic ink and varnish coated on the tinplate steel surface. The effect of accelerator and surfactant on stripping efficiency was investigated with the types and dosage of the accelerator and surfactant, the stripping temperature and stirring up condition. The highest stripping efficiency was achieved with the stripper composited by (mass fraction) 35% benzyl alcohol, 6% propanediol carbonate, 10% formic acid, 2% cetyl tri-methyl ammonium bromide (CTMAB) and 47% distilled water, respectively. This paint stripper had low volatility, and was not easy to burn. Scanning electron microscopy (SEM) test indicated that the paint stripper had little corrosive effect on tinplates.

The Improvement of Laminar Cooling System for Hot Rolled Strip Base on Rolling Process

Hot strip cooling temperature and its cooling rate is get by strip cooling system and coiling temperature of hot rolled strip is an important parameter on its performance index. It presents laminar cooling system of the 700 mm hot strip mill and the mill rolling process is present, the laminar cooling system is analyzed on the rolling theory and techniques. The laminar cooling system and its problems are present. The improvement programs of laminar cooling system are present, The control system of laminar cooling system is present combining feed-forward main control and feed-backward self-learning control, and measuring instruments is reinstall and water valves is improved. It could be a reference for the similar mill units and new building rolling mills.

Influence of the Finite Element Model on the Inverse Determination of the Heat Transfer Coefficient Distribution over the Hot Plate Cooled by the Laminar Water Jets / Wpływ Modelu Metody Elementów Skonczonych Na Współczynnika Wymiany Ciepła Wyznaczany Z Rozwiazania Odwrotnego Procesu Laminarnego Chłodzenia Płyty Metalowej

The industrial hot rolling mills are equipped with systems for controlled cooling of hot steel products. In the case of strip rolling mills the main cooling system is situated at run-out table to ensure the required strip temperature before coiling. One of the most important system is laminar jets cooling. In this system water is falling down on the upper strip surface. The proper cooling rate affects the final mechanical properties of steel which strongly dependent on microstructure evolution processes. Numerical simulations can be used to determine the water flux which should be applied in order to control strip temperature. The heat transfer boundary condition in case of laminar jets cooling is defined by the heat transfer coefficient, cooling water temperature and strip surface temperature. Due to the complex nature of the cooling process the existing heat transfer models are not accurate enough. The heat transfer coefficient cannot be measured directly and the boundary inverse heat conduction problem should be formulated in order to determine the heat transfer coefficient as a function of cooling parameters and strip surface temperature. In inverse algorithm various heat conduction models and boundary condition models can be implemented. In the present study two three dimensional finite element models based on linear and non-linear shape functions have been tested in the inverse algorithm. Further, two heat transfer boundary condition models have been employed in order to determine the heat transfer coefficient distribution at the hot plate cooled by laminar jets. In the first model heat transfer coefficient distribution over the cooled surface has been approximated by the witch of Agnesi type function with the expansion in time of the approximation parameters. In the second model heat transfer coefficient distribution over the cooled plate surface has been approximated by the surface elements serendipity family with parabolic shape functions. The heat transfer coefficient values at surface element nodes have been expanded in time by the cubic-spline functions. The numerical tests have shown that in the case of heat conduction model based on linear shape functions inverse solution differs significantly from the searched boundary condition. The dedicated finite element heat conduction model based on non-linear shape functions has been developed to ensure inverse determination of heat transfer coefficient distribution over the cooled surface in the time of cooling. The heat transfer coefficient model based on surface elements serendipity family is not limited to a particular form of the heat flux distribution. The solution has been achieved for measured temperatures of the steel plate cooled by 9 laminar jets.

An approximate fast finite element analysis of temperature distribution in rolling

In the present work, finite element analysis-based approach has been presented to estimate the temperature in the roll and the strip. Heat generation due to plastic deformation and friction is calculated employing flow formulation-based finite element analysis. The heat generated is used as input in the thermal analysis of roll and strip. Temperature distribution is carried out using finite element software ABAQUS 6.10. The heat partition between roll and strip is accomplished by matching the average temperature of roll and strip at the interface. The proposed method is validated with the experimental results available in literature and a good agreement is found. The proposed approach can be applied to hot as well as cold rolling and is computationally faster compared to existing finite element-based approaches.

A new test rig for studies of degradation of CO2 absorption solvents at process conditions; comparison of test rig results and pilot plant data for degradation of MEA

SINTEF Materials and Chemistry has recently designed an advanced laboratory test rig for studies of solvent degradation. This solvent degradation test rig (SDR) emulates the process conditions observed in an absorber/stripper configuration designed for CO2 capture. Aqueous solvent is degraded by cycling in a combined absorber and stripper setup with realistic temperatures and CO2 loadings of the solvent in addition to a defined synthetic flue gas mixture. A 14 week test campaign with degradation of 30wt.% 2-ethanolamine (MEA) was performed in the rig. Comparison between group methodology and specific nitrosamine analysis of the solvent showed that 42% of the nitrosamines were unidentified species. This indicates that many of the MEA degradation products are likely precursors for nitrosamine formation. Two nitrosamines were identified in the solvent; nitrosodiethanolamine (NDELA) and the nitrosamine of the degradation product N-(2-hydroxyethyl)-glycine (HEGly): nitroso-(2-hydroxyethyl)-glycine (NHEGly). 56% of the total nitrosamine was identified as NHEGly, while 2% was NDELA. Nitrosodimethylamine (NDMA) was detected in the absorber gas emission, but was below the quantification limit in the solvent. Results indicate that the degradation of nitrosamines and nitramine in the solvent is highly temperature dependent, and that the levels of total nitrosamines and MEA-nitramine are significantly reduced by elevated stripper temperature. The results show that the SDR results give a realistic picture on the solvent degradation to be expected in a real CO2 capture plant; degradation products formed in the SDR MEA solvent reflects those previously found in pilot plant studies. This demonstrates how the SDR enables bench-scale studies of solvent process degradation previously only available from pilot plant studies. SDR results should provide valuable input to health and environmental risk evaluations for different solvent systems for CO2 capture.

Evaluation of amine-blend solvent systems for CO2 post-combustion capture applications

This work evaluates amine-blend solvent systems for CO2 post-combustion capture applications for a 600 MWe conventional coal-fired power plant. The equilibrium-based Aspen Plus® absorption/desorption simulation tool was used for this evaluation. The total amine blends concentration was kept at the value of 30wt% for all different systems. Monoethanolamine (MEA) and diethanolamine (DEA) of weight variation of 3, 5, 10 and 15% are blended with 2-amino-2-methylpropanol (AMP), and methyldiethanolamine (MDEA). Fixed cross heat exchanger approach temperature of 10°C and stripper bottom temperature of 120°C are used as design specifications. These design specifications are used to screen each blend without CO2 loading through sensitivity analysis. The AMP with 3, 5, 10 and 15wt% blended DEA (the activator) was found to require lesser reboiler duty in comparison with 30wt% MEA, with lowest value of 3.17GJth/tonCO2 for 5wt% DEA activation. The promising four blends are further optimized using varying CO2 loadings. The blend of 5wt% DEA and 25wt% AMP with lean loading of 0.07 molCO2/molblend requires the lowest reboiler duty of 3.03GJth/ton-CO2 and lowest recirculation rate of 14.882m3/ton. Absorber temperature profiles indicate temperature changes depend significantly on the lean loading. Stripper temperature profile shows that temperature swing is pronounced at the bottom, suggesting that CO2 desorption takes place more at the lower stages.

Thermal Analysis of Strip in Multi-bending Process After Hot Rolling

The thermal histories of steel strips in a multi-bending process after hot rolling were clarified by numerical analysis in order to investigate the appropriate conditions for grain refinement. The temperature oscillates cyclically at the strip surface, whereas the temperature amplitude is relatively small at the center of thickness. The temperature distribution in the strip thickness direction depends on the transfer speed and cooling conditions, that is, air or water cooling. In industrial production, water-cooling equipment would be necessary in order to cancel the accumulated heat generation caused by bending deformation and to maintain the strip temperature in the appropriate range for grain refinement.

Analysis of Radiative Heat Transfer in an Indirect-Fired Strip Annealing Furnace based on Integral Equations

A dynamical model of a tunnel furnace for strip annealing is proposed. The continuous furnace has a uniform cross section and is divided into several heating zones, where the local temperatures are used as model inputs. The presented model is tailored to control and optimization applications and takes into account the most important underlying physical phenomena, i.e., the energy balance of the strip and the heat transfer due to radiation. For determining the radiative heat transfer, radiation balances in the form of integral equations are used. Approximate solutions of these equations are obtained by means of the method of weighted residuals. To facilitate an accurate representation of the strip temperature, the strip motion is described based on Lagrangian coordinates, which is especially useful for capturing the temperature transition at welded joints between consecutive strips. The capabilities of the model are explored in simulation studies.

Modeling of Strip Temperature in Rapid Cooling Section of Vertical Continuous Annealing Furnace

The strip temperature is affected by many factors in rapid cooling section (RCS) of the vertical continuous annealing furnace (VCAF). They can be divided into four types: the physical properties of cooling gas, the geometry characteristics of configuration of cooling equipment, the heat transfer between the strip and the cooling gas, and the conductivity of the strip. It aims to model the strip temperature in the cooling section based on the fundamental heat transfer theory and the four aspects factors. The model for transient Nusselt number is obtained by considering Reynolds number, Prandtl number and geometry characteristics of RCS. Then cooling model of the strip transient temperature is built by Nusselt number, heat transfer coefficient and heat conductivity of the strip. The results are compared with the data from production line. The comparisons indicate that the model can well predict cooling temperature of the strip. It is hoped that the proposed model can be used for design and control of the vertical continuous annealing furnace.