Method for producing strips of metal, and production line for performing the method

Abstract

The invention relates to a method of and a plant for making hot-rolled strips of cast metal, wherein the cast strip is subjected as a rough strip to at least a first step for momogenizing the grain structure in a protective gas and the cast strip is then subjected to at least a further heat-treatment step before it is rolled to reduce its thickness. After the thickness reduction the cast strip is subjected to a second step of homogenization or recrystallization of its grain structure before finally the strip is passed to a cutter and a finished rolled hot piece is severed from the following strip.

1 . A method of making hot-rolled strips of cast steel, where a cast steel strip is subjected as a rough strip to at least one heat-treatment step and subsequently wound or stacked as a hot strip, the method comprising the steps of sequentially:
 subjecting the rough strip obtained from the casting step in a protective gas atmosphere to an upstream step of homogenizing its structure by maintaining a temperature at approximately 900 to 1000° C., by reducing the temperature by approximately 200° C., or by increasing the temperature by approximately 250° C.;   subjecting the homogenized rough strip to at least one additional heat-treatment step by maintaining the temperature at 880 to 940° C., by reducing the temperature by approximately 50° C., or by increasing the temperature by approximately 50° C.;   subjecting the heat-treated rough strip to a hot-rolling step having at least one pass, with the rough strip undergoing a reduction in thickness of less than 49%;   subjecting the hot-rolled rough strip to a downstream homogenization step or recrystallization of its structural composition, by maintaining the temperature at approximately 700 to 900° C., by reducing the temperature by approximately 100° C., or by increasing the temperature by approximately 50° C.; and   passing the rough strip through a cutter that is synchronized with the transport or belt speed to cut the strip into pieces of rolled hot strip.   
     
     
         2 . The method according to  claim 1 , wherein the casting step is decoupled from the rolling step. 
     
     
         3 . The method according to  claim 1  wherein the transport speed of the rough strip is influenced by a mass-flow controller. 
     
     
         4 . The method according to  claim 1 , further comprising the step, before the hot rolling, of
 subjecting the rough strip to an upstream heat-treatment step by maintaining the temperature at approximately 880 to 940° C., by reducing the temperature by approximately 50° C., or by increasing the temperature by approximately 50° C.   
     
     
         5 . The method according to  claim 1 , further comprising the step, after the hot rolling, of
 subjecting the rough strip to an upstream heat-treatment step by maintaining the temperature at approximately 880 to 940° C., by reducing the temperature by approximately 50° C., or by increasing the temperature by approximately 50° C.   
     
     
         6 . The method according to  claim 1 , further comprising the step, after the hot rolling, of
 subjecting the rough strip to an upstream homogenization step for the recrystallization of the rough strip at the edges, by maintaining the temperature at approximately 700 to 900° C., by reducing the temperature by approximately 100° C., or by increasing the temperature by approximately 50° C.   
     
     
         7 . The method according to  claim 6 , wherein the upstream homogenization step, precedes passing the rough strip through the cutter, the method further comprising the step after cutting of
 winding or stacking the cut pieces of the rough strip as hot strip.   
     
     
         8 . A plant for carrying out the method of  claim 1 , the plant comprising:
 at least one casting machine for producing a cast rough strip of a predetermined thickness;   at least one conveyor for transporting the cast strip;   at least one homogenization zone in which the temperature is maintained, reduced, or increased in order to to influence the structural composition of the cast rough strip;   at least one additional temperature zone in which the temperature is maintained, reduced, or increased;   at least one upstream roll stand for partial deformation of the rough strip;   at least one cutter;   at least one winding or stacker;   an upstream homogenization zone downstream of the casting machine and in which the temperature is maintained, reduced, or increased;   a temperature controller downstream of the upstream homogenization zone for maintaining the temperature, reducing the temperature, or increasing the temperature;   an upstream roll stand downstream of the temperature controller reducing the rough strip in thickness of less than 49% in at least one pass;   a downstream homogenization zone downstream of the roll stand in which the temperature is maintained, reduced, or increased in order to obtain a recrystallization of the hot strip at least at the edges; and   a cutter downstream of the downstream homogenization zone having a working speed synchronized with the speed of the conveyor and with the rolled rough strip being separated from the rough strip as a hot strip.   
     
     
         9 . The plant according to  claim 8 , wherein the casting step is decoupled from the rolling step. 
     
     
         10 . The plant according to  claim 8  further comprising:
 a mass-flow controller comprised of a dancer roll or a looper downstream of the upstream homogenization zone. 
 
     
     
         11 . The plant according to  claim 8 , further comprising:
 a mass-flow controller relative to the transport direction of the rough strip between an upstream rough strip conveyor and a downstream rough strip conveyor.   
     
     
         12 . The plant according to  claim 11 , further comprising
 an upstream temperature controller and a mass-flow controller downstream relative to the transport direction of the belt of the upstream homogenization zone, the mass-flow controller being provided upstream of the downstream temperature controller.   
     
     
         13 . The plant according to  claim 12 , further comprising:
 a conveyor between the upstream temperature controller and the mass-flow controller or between the mass-flow controller and the downstream temperature controller.   
     
     
         14 . The plant according to  claim 8 , further comprising:
 a coiler or a stacker is provided downstream of the cutter.