Rapid quench line

Abstract

A rapid quenching line can be suitable for use with hot coil at, or above the metal strip's recrystallization point. Hot coil can be uncoiled by a low tension uncoiler using a non-contacting hold-down device. The metal strip coming off the hot coil is rapidly quenched (e.g., at rates of at or above 100° C./s or 200° C./s) through multiple quenching zones. Coolant can be removed, such as with an air knife and/or a wiper (e.g., an ultra-compliant wiper). Steam can be collected from earlier quenching zones and be repurposed to provide humid air to the metal strip, such as at regions where the temperature of the metal strip is at or below the Leidenfrost point. The cooled metal strip can pass through a bridle to increase the tension in the metal strip before the metal strip is optionally lubricated and then recoiled or otherwise further processed.

1 . A system, comprising:
 a low-tension unwinding unit for receiving and unwinding a metal coil of metal strip;   a non-contacting hold-down device positioned adjacent the low-tension unwinding unit to provide force on the metal strip towards the center of the metal coil during unwinding of the metal coil;   a set of quenching zones for cooling the metal strip, wherein the set of quenching zones provides sufficient coolant to reduce a temperature of the metal strip by a rate of at least 30° C. per second;   a coolant removal unit positioned downstream of the set of quenching zones; and   a bridle unit positioned downstream of the coolant removal unit for increasing tension in the metal strip.   
     
     
         2 . The system of  claim 1 , wherein the low-tension unwinding unit comprises insulation disposed to retain heat within coiled portions of the metal coil. 
     
     
         3 . The system of  claim 1 , wherein the low-tension unwinding unit comprises a heat source for providing heat to coiled portions of the metal coil, wherein the heat source is coupled to a controller for maintaining the metal coil at or above a threshold temperature. 
     
     
         4 . The system of  claim 1 , wherein the non-contacting hold-down device comprises at least one of:
 one or more magnets for generating a changing magnetic field through the metal strip, or   a nozzle for blowing heated air against the metal strip.   
     
     
         5 . The system of  claim 4 , wherein the changing magnetic field is configured distribute the force over time across a width of the metal strip. 
     
     
         6 . (canceled) 
     
     
         7 . The system of  claim 1 , further comprising:
 a flatness measurement unit positioned to measure a flatness of the metal strip; and   a controller coupled to the flatness measurement unit and the set of quenching zones to adjust delivery of the coolant based on measured flatness of the metal strip.   
     
     
         8 . The system of  claim 1 , further comprising a stabilization system positioned upstream of the set of quenching zones to introduce a wave into the metal strip. 
     
     
         9 . The system of  claim 1 , wherein the metal strip remains supported without mechanical contact between the metal coil and the coolant removal unit. 
     
     
         10 . The system of  claim 1 , wherein the set of quenching zones comprises a steam reclamation module for redirecting humid air from at least one of the set of quenching zones to the metal strip at a location downstream of the at least one of the set of quenching zones. 
     
     
         11 . The system of  claim 1 , wherein the location downstream of the at least one of the set of quenching zones is a location where the temperature of the metal strip is at or below a Leidenfrost point. 
     
     
         12 . The system of  claim 1 , further comprising:
 a pre-quench heating unit positioned downstream of the low-tension uncoiling unit; and   a controller coupled to the pre-quench heating unit to heat the metal strip to a target temperature prior to the metal strip entering the set of quenching zones.   
     
     
         13 . The system of  claim 1 , wherein the non-contacting hold-down device is positioned to provide the force on the metal strip at a location at or adjacent to where the metal strip falls away from the metal coil due to gravity. 
     
     
         14 . A method, comprising:
 unwinding a hot metal coil using a low-tension unwinder, wherein unwinding the hot metal coil comprises applying a non-contacting hold-down force to the hot metal coil and permitting metal strip of the hot metal coil to fall away from the metal coil;   rapidly quenching the metal strip in a set of quenching zones, wherein rapidly quenching the metal strip comprises applying coolant to the metal strip to reduce a temperature of the metal strip at a rate of at least 100° C. per second;   removing the coolant from the metal strip; and   applying downstream tension to the metal strip.   
     
     
         15 . The method of  claim 14 , further comprising maintaining an initial temperature of the hot metal coil at the low-tension unwinder. 
     
     
         16 . The method of  claim 14 , further comprising preheating the metal strip immediately prior to rapidly quenching the metal strip. 
     
     
         17 . The method of  claim 14 , wherein applying the non-contacting hold-down force comprises at least one of:
 generating a changing magnetic field through the metal strip; or   blowing heated air against the metal strip.   
     
     
         18 . (canceled) 
     
     
         19 . The method of  claim 14 , further comprising:
 measuring flatness of the metal strip; and   adjusting delivery of the coolant based on the measured flatness.   
     
     
         20 . The method of  claim 14 , further comprising inducing a wave in the metal strip without contacting the metal strip. 
     
     
         21 . The method of  claim 14 , further comprising:
 capturing steam from at least one of the quenching zones; and   redirecting the captured steam towards the metal strip.   
     
     
         22 . The method of  claim 21 , wherein redirecting the captured steam comprises redirecting the capture steam towards the metal strip at a location where a temperature of the metal strip is at or below the Leidenfrost point.