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Product Bulletin - Aluminum Heat Treatment
Aluminum Annealing Furnace Systems
Aluminium AnnealingClick here for comprehensive bulletin in .pdf format: http://www.secowarwick.com/alumprocess/bulletins/af-502-2.pdf
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Coil Annealing Furnaces |
SECO/WARWICK provides custom engineered aluminum (aluminium) coil and foil annealing furnaces with capacities ranging from single coil modular furnaces to multi-zone furnaces with tight zone control. We have the experience, knowledge and talent to manufacture efficient furnaces with exceptional temperature uniformity and unique charging techniques to fit the most demanding application. SECO/WARWICK continues to develop technologies to improve equipment performance and efficiency. Two significant improvements for coil and foil processing include:
- Mass Flow design, to protect load surfaces that are vulnerable to damage during high atmosphere flow.
- Vortex Flow Jet Heating System that reduces cycle time by taking advantage of the high heat transfer produced through convection heating.
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Single Zone Annealing Furnaces |
Temperature Uniformity
SECO/WARWICK's annealing furnaces exploit several different designs to ensure temperature uniformity. SECO/WARWICK holds patents for innovations oncontrolling airflow recirculation over various sized loads, increasing heat transfer and uniformity. Our furnaces incorporate both vertical airflow with specifically designed vertical baffles on each side of the load or the high-velocity directed mass flow system. In either case, the vertical baffles improve air stream uniformity and separate the load from direct heat radiation. Radiant tubes for either gas fired burners or electric heating elements provide indirect heating, protect the load from direct heat radiation, and maximize temperature uniformity.
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Temperature Uniformity Profiles |
Aluminum (aluminium) annealing requires an advanced convective heating system to obtain the shortest possible cycle without any loss of quality in the material. Quality problems typically appear at the strip edges, and are represented by non-uniform material properties like hardness, and discolorations of the strip surface, as in the case of 5xxx and 7xxx alloys caused by Mg- or Mn-bleeding, cracking of residual milling oil from coil degreasing, or coil surface melting. These problems are caused by overheating at the coil edge resulting from non uniform impingemen of the air flow. The governing parameter describing the temperature uniformity of a convective heating system is the ratio of maximum to minimum heat transfer coefficient (HTC). This parameter limits the heat up time since the smaller the HTC ratio the higher the average temperature that can be obtained without exceeding the maximum tolerable local heat transfer.
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Nozzle Jet Array |
The Vortex Flow Jet Heating System incorporates arrays of 4 round inclined nozzle jets that generate a spiral vortex motion of air that results in high heat transfer without producing hot spots in the coil. The high volume flow of this nozzle system in conjunction with a unique semi-axial fan design allows the coil to be heated more uniformly by a larger mass of atmosphere.The effective thermal conductivity in a strip coil is much lower in the radial direction than in the axial direction, therefore, the most effective way of heating the coil is through the edges of the coil wraps. The difference between the thermal conductivity for the two directions is caused by the heat insulating effect of the gas and milling oil layers in the coil between the strip layers.
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| Infrared picture of aluminum (aluminium) coil |
Analysis of the infrared picture, equally scaled, indicates that a more uniform surface temperature can be achieved by using the new Vortex Flow Jet Heating System.The coil surface temperature uniformity profiles present an overview of temperature uniformity for the entire heat up cycle. These profiles demonstrate that a better surface uniformity is achieved using the vortex nozzle system. The HTC ratio calculation based on the above data is 1.25 for the vortex nozzle system. For aluminum (aluminium) alloys of lower thermal conductivity, this parameter is expected to be even higher.
- Reduced heat-up time without local overheating
- Improved uniformity of material properties
- Minimizes local cracking and staining of milling oil
- Reduced electrical consumption because the fan operates at a lower speed rather than a higher volume flow
More information on this technology is located at this link: http://www.secowarwick.com/metalminutes/jetheatingalcoils/jetheatingalcoils.pdf
R1 5/9/2006 Updated information to include Vortex Jet Heating System and Images
R2 9/15/2006 Added .pdf brochure link
P. O. Box 908 180 Mercer Street Meadville, PA 16335-6908 USA
Phone (814)332-8400 - Fax (814)724-1407
info@secowarwick.com
©1995-2008 SECO/WARWICK Corporation All Rights Reserved.
The latest design, materials and equipment specifications should be obtained from the company before any reliance is placed on the enclosed since changes may occur due to product improvement.
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