Patent Publication Number: US-2011049773-A1

Title: Heat retention tunnel for processing coils of hot rolled bar and rod products

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 61/237,443 filed on Aug. 27, 2009 entitled HEAT RETENTION TUNNEL FOR PROCESSING COILS OF HOT ROLLED BAR AND ROD PRODUCTS which is incorporated by reference in its entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to hot rolling mills producing bar and rod products, where coils of the hot rolled products are temporarily held for retarded cooling in enclosed tunnels. 
     BACKGROUND DISCUSSION 
     A coil handling system employing retarded cooling tunnels is disclosed in U.S. 2008/0019805A1, the description of which is herein incorporated by reference. In this system, the tunnels are provided with adjustable side louvers to assist in controlling cooling rates. 
     A deficiency of this system lies in the non-uniform cooling of the coils, which produces unacceptable variations in mechanical and metallurgical properties of the material. These variations are caused in part by unwanted air flow through the system, resulting in uneven convective cooling. 
     In addition to the heat loss due to uneven convective cooling, there is also a significant amount of heat loss due to radiation from the surfaces of the coils. This is most significant on the outside diameters of the coils, which have the most surface area. Some portions of the outside coil diameters “see” portions of the outside diameters of adjacent coils which are at approximately the same temperature and therefore absorb relatively little radiant energy. However, there are significant portions of the outside diameters that “see” cooler surfaces, e.g., the tunnel insulation and other parts of the structure, and therefore those outside portions lose significantly more radiant energy. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, the conventional retarded cooling tunnels are modified to reduce uneven convective and radiant cooling of the coils being processed. Uneven convective cooling is reduced by providing barrier plates beneath the conveyor path to retard upward flow of ambient air, and uneven radiant cooling is reduced by providing heat reflective panels along the sides of the conveyor path. 
     These and other features and attendant advantages of the present invention will now be described in further detail with reference to the accompanying drawings, wherein: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is across sectional view through a heat retention tunnel embodying the concepts of the present invention; 
         FIG. 2  is a vertical sectional view taken along line  2 - 2  of  FIG. 1 , with the coils and conveyor eliminated in order to better view the positions of the heat reflective and barrier panels; and 
         FIG. 3  is a horizontal sectional view taken along line  3 - 3  of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to the accompanying drawings, a heat retention tunnel embodying the concepts of the present invention is generally depicted at  10 . The tunnel includes side walls  12  and a roof  14 , the interior surfaces of both being preferably lined with insulating panels  16 . A conveyor  18  defines a transport path extending along the length of the tunnel. The conveyor includes modules with driven rollers  20  arranged to support and propel pallets  22  into and through the tunnel. The pallets include stems  24  projecting vertically and axially through coils  26  of hot rolled product supported on the pallets. The tunnel side walls and roof are provided with pivotal louvres  28  which are adjustable between closed positions (as depicted by solid lines) and open positions (as depicted by broken lines). 
     In accordance with one aspect of the present invention, heat reflective panels  30  line the interior surfaces of the side walls  12 . The heat reflective panels overlie the insulating panels  16 , and have heights at least equal to the tallest coils being processed. The panels  30  are fabricated from a heat resistant material, a preferred candidate being stainless steel. Although not shown, it is to be understood that the ends of the tunnel are closed by entrance and exit doors that are also lined with heat reflective panels  30 . 
     In accordance with another aspect of the present invention, barrier panels  32  underlie the transport path along which the coils are being conveyed. The barrier panels are configured and arranged to retard any upward flow of ambient air through the tunnel. 
     In light of the foregoing, it will be appreciated by those skilled in the art that the heat reflective panels  30  promote uniform radiant cooling by reflecting heat radiating from the surface portions of the coils  26  facing the tunnel side walls. A similar effect is produced between confronting surface portions of coils arranged successively along the transport path, the net effect being more uniform overall radiant cooling of the coils. 
     The barrier panels  32  retard upward flow of ambient air, thus promoting a more uniform top to bottom convective cooling of the coils.