Cooling facility and method

Abstract

A cooling method for a rolling ingot of aluminium alloy after metallurgical homogenization heat treatment of said ingot and before hot rolling, characterized in that cooling by 30 to 150° C. is performed at a rate of 150 to 500° C./h, with a thermal differential of less than 40° C. throughout the treated portion of the ingot is disclosed. A facility allowing use of said method and said implementation is also disclosed.

1 . A method of cooling an aluminum alloy rolling ingot after a metallurgical homogenization heat treatment of said ingot at a homogenization temperature, optionally between 450 to 600° C., and prior to hot rolling,
 wherein the aluminum alloy rolling ingot has a format of dimensions from 250 to 800 mm in thickness, from 1000 to 2000 mm in width, and from 2000 to 8000 mm in length; a top surface, a bottom surface, and four side surfaces, wherein the top and bottom surfaces have a larger surface area than the side surfaces; and a head and a foot corresponding to extremities in a longitudinal direction, 
 wherein cooling, by a cooling value of 30 to 150° C., is performed at a rate of from 150 to 500° C./h, with a thermal differential of less than 40° C. over the entire ingot cooled from the homogenization temperature thereof. 
 
     
     
         2 . The method of  claim 1 , wherein cooling is carried out in at least two phases:
 a first spraying phase in which the ingot is cooled in a chamber equipped with a spray system comprising ramps of nozzles for spraying cooling liquid or spray under pressure, divided into upper and lower parts of said chamber, so as to spray the larger top and bottom surfaces of said ingot, and   a complementary phase of thermal equalization in still air, in a tunnel with interior reflective walls, lasting from about 2 to about 30 minutes, depending on the fonnat of the ingot and the cooling value.   
     
     
         3 . The method of  claim 2 , wherein the spray system guides the cooling liquid or spray under pressure to the ingot edges where the cooling liquid or spray under pressure is discharged in form of a cascade without touching the ingot's side surfaces. 
     
     
         4 . The method according to  claim 2 , wherein the spraying and thermal equalization phases are repeated and for an overall average cooling of more than 80° C. 
     
     
         5 . The method according to  claim 2 , wherein the cooling liquid or spray under pressure is water. 
     
     
         6 . The method according to  claim 2 , wherein the head and the foot of the ingot, corresponding to 300 to 600 mm at ends thereof, are cooled less than the rest of the ingot. 
     
     
         7 . The method according to  claim 2 , wherein cooling of the head and foot is modulated by turning the ramps of nozzles on or off. 
     
     
         8 . The method according to  claim 2 , wherein the spraying phases and not therma equalization are repeated, and in that the head and foot of the ingot are cooled differently from the rest of the ingot in at least one of the spray phases. 
     
     
         9 . The method according to  claim 8 , wherein a first spray phase is performed with zero heel, or continuous spraying of the ingot followed, without a first thermal equalization phase, by a second spray phase with a heel of a pair of ramps, thereby allowing to reduce the duration of a final equalization phase necessary for thermal balancing of the ingot. 
     
     
         10 . The method according to  claim 2 , wherein transverse thermal uniformity of the ingot is ensured by modulating spraying in the ingot width by switching the nozzles or spray nozzles on or off, or screening said spraying. 
     
     
         11 . The method according to  claim 1 , wherein the nozzles produce full cone jets with an angle of between 45 and 60°, and lower nozzle axes are oriented normally to the bottom surface of the ingot. 
     
     
         12 . A facility for cooling an aluminum alloy rolling ingot after a metallurgical homogenization heat treatment of said ingot at a homogenization temperature, comprising:
 a spray chamber comprising ramps of nozzles for spraying cooling liquid or spray under pressure, arranged in upper and lower parts of said chamber, so as to spray two large surfaces, top and bottom, of said ingot,   wherein upper nozzle ramps are paired in the direction of movement of the ingot;   in any given pair, the upper ramps are inclined such that:   jets of the two paired nozzle ramps are oriented in opposition to one another;   the jets have a normal edge to the upper surface of the ingot;   an equalization tunnel in still air on leaving the spray chamber, in a tunnel whose internal walls and roof are made of an internally reflective material, allowing equalization of the ingot by heat diffusion in said ingot, the core warming the surfaces.   
     
     
         13 . The facility according to  claim 12 , wherein:
 the cooling liquid or spray nozzles of the cell produce full cone jets with an angle of between 45 and 60°.   
     
     
         14 . The facility according to  claim 12 , wherein:
 lower nozzle axes are oriented normally to the lower surface of the ingot.   
     
     
         15 . The facility according to  claim 12 , wherein:
 an overlap of jets of the two paired ramps is between ⅓ and ⅔ of the width of each jet, and optionally substantially half.   
     
     
         16 . The facility according to  claim 12 , wherein an envelope of the two paired nozzle ramps so formed has an M profile. 
     
     
         17 . The facility according to  claim 12 , wherein:
 pairs of upper and lower nozzle ramps are placed substantially face-to-face, so that upper and lower spray lengths are substantially equal and opposite each other.   
     
     
         18 . The facility according to  claim 12 , wherein the entire facility, spray chamber and equalization tunnel are controlled by a thermal model encoded on a PLC, the thermal model determining the settings of the facility according to the temperature estimated by thermal measurement at the start of the spray chamber and according to the target output temperature, optionally at a start temperature for hot rolling. 
     
     
         19 . The facility according to  claim 12 , wherein:
 wherein the aluminum alloy rolling ingot has a format of dimensions from 250 to 800 mm in thickness, from 1000 to 2000 mm in width, and from 2000 to 8000 mm in length; a top surface, a bottom surface, and four side surfaces, wherein the top and bottom surfaces have a larger surface area than the side surfaces; and a head and a foot corresponding to extremities in a longitudinal direction,   and wherein the spray system guides the cooling liquid or spray under pressure to the ingot edges where the cooling liquid or spray under pressure is discharged in form of a cascade without touching the ingot's side surfaces.   
     
     
         20 . A method for treating an ingot in a facility according to  claim 12 , comprising:
 centering the ingot at an entrance to the facility;   measuring upper surface temperature of the ingot;   calculation by the PLC, using the thermal model, of the spray chamber settings depending on the input temperature and the target output temperature, optionally target cooling of the ingot, including determining the number of ramps activated, the number of nozzles activated at the ingot edges, speed of movement of the ingot within the spray chamber, starting and stopping the spraying ramps, and the holding time in the equalization tunnel;   moving the ingot continuously through the spray chamber, with upper and lower spraying according to the PLC calculations;   transfer of the ingot from the spray chamber to the equalization tunnel; and   holding the ingot in the equalization tunnel for a period determined by the PLC.