Hot Rolling Of Aluminum Research Articles

Generalisation of the hydrodynamics model method for hot and cold strip rolling application

The present work constitutes a generalization of the hydrodynamic model used to predict the pressures and the rolling speeds during the hot rolling of aluminum and copper strips. The hydrodynamic model with a linear behavior (Newton viscous) of the materials shows good predictions in the literature but its applicability is questionable in non-linear cases, when the materials exhibit viscoplastic or plastic behavior. This work extends the model to accommodate non-linear cases commonly encountered in rolling models (viscoplastic and plastic behaviors). The obtained results are in good agreement with experimental data from the literature. The validated model can, therefore, be considered an enhanced hydrodynamic model for predicting pressures and velocities during both hot and cold rolling of thin strips.

The tribological behavior of PVD coated work roll surfaces during rolling of aluminum

The use of PVD coatings for the mitigation of roll wear caused by high friction and adhesion in the roll gap during hot rolling of aluminum has been investigated. A tribo-simulator with a roll-on-block configuration was used for rolling AA1100 blocks at 25°C and 450°C under dry and lubricated conditions respectively. Six types of coatings, TiN, TiCN, TiAlN, CrN, Cr and DLC, were applied to M2 steel rolls and their performances compared with an uncoated roll. The CrN coating displayed a good combination of low friction and good aluminum adhesion mitigation behavior. The Cr coating's coefficient of friction (COF) and its surface area fraction covered with transferred aluminum were among the highest. The TiAlN coating had the lowest COF under hot rolling conditions with evidence of an oxide layer that was observed to delaminate from the rest of the coating. The DLC coating displayed the highest COF during hot rolling but the lowest during cold rolling. It had one of the lowest aluminum transfers to its surface under both cold and hot rolling conditions. The high friction was attributed to the transfer of a carbonaceous layer from the DLC coating to the aluminum surface.

Developing environmentally friendly rolling lubricants

Swerea MEFOS pilot mill has been used as a rolling lubricant development tool. The objectives were to improve the lubrication during rolling and thereby improve the operation of the rolling mills. This was done taking into account both the technological aspect, rolling mill output, and the ecological aspect, investigating ways to use rolling lubricants that are more ecologic sustainable, i.e. alternatives to oil-based lubricants as well as the recycling/recovering of oil-based lubricants. Oil-in-water emulsions and an aqueous solution, by the producer termed a conditional emulsion, were tested where the lubricant formulation was altered to optimize the performance for hot rolling of aluminium. Cold-rolling tests were also run on steel coils, where the presence of rust protective oil was studied as well as the influence of aged emulsion behaviour compared with fresh emulsion. Finally, Sapa developed a vacuum evaporator system for recovering oil from dumped emulsion generated during aluminium hot rolling, followed by separation, centrifugation, and flocculation. The cleaned concentrates were reconditioned for reuse. The recycled and recovered emulsion was tested and compared with the original fresh emulsion in Swerea MEFOS pilot mill with results as good as the fresh emulsion.

Advances on Modelling of the Tool/Workpiece Interface during High Shear Processing

Understanding and prediction of physical phenomena in different scales at the same time that are taking place at the tool/workpiece interface during high shear processing is done in different ways combining the latest finite element (FE) and discrete element (DE) analysis technology. The high shear processing is observed during hot rolling of aluminium, when it produces a highly deformed subsurface layer; and also during friction stir welding (FSW), when it results in significant heat generation and flow. The FE analysis is used for macro-scale simulation while the DE method is applied to simulate meso-scale phenomena taking place in the thin, sometimes a few micron thicknesses, surface layer. Different FE models and numerical techniques combined with DE based transient dynamics approaches are discussed in this work.

Combined Discrete/Finite Element Multiscale Approach for Modelling of the Tool/Workpiece Interface during High Shear Processing: Hot Rolling and Friction Stir Welding Applications

The concept of combining the latest finite element (FE) and discrete element (DE) multiscale numerical technologies for modelling of the tool/workpiece interface during high shear processing is described. The potential of FE tools and techniques merged with DE based transient dynamics is highlighted. Linking of the modelling scales is based on transferring the corresponding boundary conditions from the macro model to the representative cell, considered as the meso- level model. This meso- model consists of a large number of bodies that interact with each other. The transfer processes are described by the system of diffusion and motion equations including contact detection and interaction solutions for particles integrated in time. Modelling of the tool/workpiece interface including both mixing of the oxide particles into the subsurface layer during hot rolling of aluminum and heat generation during friction stir welding (FSW) are considered.

A model for recrystallisation kinetics, texture and grain size applied to multipass hot rolling of an AlMgMn aluminium alloy

A physically based model for primary recrystallisation, including recrystallisation kinetics, grain size and texture evolution, during hot rolling of aluminium is presented. The model is based on extensive experimental investigations that have been directed towards identifying the nature of the nucleation sites for recrystallised grains of different crystallographic orientations. Particle stimulated nucleation and nucleation from cube bands and grain boundary regions have been incorporated in the model. The model has been applied to the hot rolling of an AlMgMn alloy processed in 13 passes. Reasonable model predictions have been obtained for cases of reversing rolling and a 3-stand tandem mill, including variations in the exit gauge temperature.

Patents: USA

The use of PVD coatings for the mitigation of roll wear caused by high friction and adhesion in the roll gap during hot rolling of aluminum has been investigated. A tribo-simulator with a roll-on-block configuration was used for rolling AA1100 blocks at 25 °C and 450 °C under dry and lubricated conditions respectively. Six types of coatings, TiN, TiCN, TiAlN, CrN, Cr and DLC, were applied to M2 steel rolls and their performances compared with an uncoated roll. The CrN coating displayed a good combination of low friction and good aluminum adhesion mitigation behavior. The Cr coating's coefficient of friction (COF) and its surface area fraction covered with transferred aluminum were among the highest. The TiAlN coating had the lowest COF under hot rolling conditions with evidence of an oxide layer that was observed to delaminate from the rest of the coating. The DLC coating displayed the highest COF during hot rolling but the lowest during cold rolling. It had one of the lowest aluminum transfers to its surface under both cold and hot rolling conditions. The high friction was attributed to the transfer of a carbonaceous layer from the DLC coating to the aluminum surface.

アルミ熱延における材料温度計算

Fundamental experiments on air cooling, spray cooling and hot rolling of aluminum are performed for determining the heat transfer coefficients in hot rolling. And using these heat transfer coefficients, the temperature change of aluminum strip in hot strip mill line is calculated by the method of finite differences. The calculation results show that except in the roll gap, there is almost no temperature difference between the surface and the cross section center of the strip in case of aluminum, unlike in case of steel.Therefore, for computer control, temperature model for calculating the mean strip temperature is necessary.

The Mechanism of Roll-Coating Buildup During Hot Rolling of Aluminum

An important limitation to the quality of rolled aluminum is the transference of metal from the slab to the roll and back to the surface of the slab during hot rolling, producing defects known as pickup. The way in which the buildup of roll-coating controls pickup has been studied using a small laboratory mill. The top roll of the mill was modified to take inserts which were ground in place to the same finish as the roll. The inserts could be removed between the rolling of one strip and the next so that the process of coating buildup could be followed in the scanning electron microscope. The distribution of aluminum on the surface of the roll-was mapped using the energy dispersive X-ray spectrometer attachment to the microscope. Additional chemical analysis of the coating was obtained by X-ray photo-electron spectroscopy. The coating built up initially as large isolated lumps streaked out in the rolling direction, which become overlaid with an accumulation of much smaller particles. The coaling was found ...

Inst. Metals Informal Discussion on Lubricants for Metal Working Operations in Non‐Ferrous Metal Industries

An informal discussion on the above subject was held by the Institute of Metals in January at Birmingham University, and the chair was taken by Mr. W. J. Thomas, M.I.Mech.E., Chairman of the Metallurgical Engineering Committee. The Institute are to be congratulated on bringing this meeting to discuss this important subject and its many problems. It is considered that, important as the discussion was, the major part of the time was not devoted to informal discussion. The morning, for example, was mostly devoted to some lengthy reading of problems in connection with the hot rolling of aluminium, there being no reference to the hot forging of aluminium or hot brass pressing which were subjects for which several visitors had travelled long distances to discuss. Many felt that they could not really afford their time to listen to just one or two individual problems, however serious they might be to those concerned. We give shortened versions of most of the discussion that took place. Some of the contributions have had to be seriously shortened to enable us to include the main points from most speakers. In our next issue we shall deal similarly with the discussion that followed on Lubricants for the Cold‐Rolling, and Cold‐Drawing of Non‐Ferrous Metals.