Method for hot rolling and for heat treatment of a steel strip

Abstract

The invention relates to a process for hot rolling and for heat treatment of a strip ( 1 ) of steel. To make it possible to produce high-strength and very high-strength strips having satisfactory toughnesses more economically in a continuous production plant, the process provides the steps: a) heating of the slab to be rolled; b) rolling of the slab to the desired strip thickness; c) cooling of the strip ( 1 ), with the strip ( 1 ) having a temperature above ambient temperature (T 0 ) after cooling; d) rolling up of the strip ( 1 ) to produce a coil ( 2 ); e) rolling off of the strip ( 1 ) from the coil ( 2 ); f) heating of the strip ( 1 ); g) cooling of the strip ( 1 ) and h) transport of the strip ( 1 ) to a further destination, with the strip ( 1 ) having a temperature above ambient temperature (T 0 ) before heating as per step T).

1 . A method for hot rolling and for heat treatment of a strip of steel, the method comprising the steps of:
 a) heating the slab to be rolled;   b) rolling the slab to the desired strip thickness;   c) cooling the strip, wherein after cooling the strip has a temperature above the ambient temperature;   d) coiling the strip into a coil;   e) uncoiling the strip from the coil;   f) heating the strip;   g) cooling the strip and   h) removing the strip,   wherein before the heating according to step f), the strip has a temperature above the ambient temperature and wherein when carrying out step d), the coil is located at a coiling station and that when carrying out step e), it is located at an uncoiling station spatially remote from the coiling station, wherein the coil is transported from the coiling station to the uncoiling station between steps d) and e) in a thermally insulated manner.   
   
   
       2 . (canceled) 
   
   
       3 . The method according to  claim 1  wherein step e) directly follows step d). 
   
   
       4 . The method according to  claim 1  wherein during cooling or after cooling according to step c) and/or according to step g), the strip is subjected to a straightening process. 
   
   
       5 . The method according to  claim 1  wherein between the uncoiling according to step e) and the heating according to step f), the strip is subjected to a straightening process. 
   
   
       6 . The method according to  claim 1  wherein between the heating according to step f) and the removal according to step h), the strip is subjected to a straightening process. 
   
   
       7 . The method according to  claim 4  wherein the straightening process is effected by deflecting the strip around base, deflecting, driving or other rollers. 
   
   
       8 . The method according to  claim 5  wherein the straightening process is carried out by means of a skin-pass frame. 
   
   
       9 . The method according to  claim 1  wherein the strip is subjected to a straightening process during the heating according to step f). 
   
   
       10 . The method according to  claim 1  wherein the cooling of the strip according to step c) comprises a laminar cooling and intensive cooling. 
   
   
       11 . The method according to  claim 1  wherein the cooling of the strip according to step g) comprises a laminar cooling. 
   
   
       12 . The method according to  claim 1  wherein the cooling of the strip according to step c) and/or according to step g) takes place in zones over the width of the strip. 
   
   
       13 . The method according to  claim 1  wherein the cooling of the strip according to step g) comprises air cooling. 
   
   
       14 . The method according to  claim 1  wherein the cooling of the strip according to step g) is carried out by means of a high-pressure bar so that cleaning and/or descaling of the strip takes place at the same time. 
   
   
       15 . The method according to  claim 1  wherein the heating of the strip according to step f) comprises inductive heating. 
   
   
       16 . The method according to  claim 15  wherein the inductive heating of the strip takes place in an inert gas atmosphere. 
   
   
       17 . The method according to  claim 1  wherein the heating of the strip according to step f) is effected by direct flame impingement of the strip. 
   
   
       18 . The method according to  claim 17  wherein the direct flame impingement of the strip is effected by a gas jet comprising at least 75% oxygen in which a gaseous or liquid fuel is mixed. 
   
   
       19 . The method according to  claim 18  wherein the direct flame impingement is effected by a gas jet comprising pure oxygen. 
   
   
       20 . The method according to  claim 1  wherein the removal of the strip according to step h) comprises coiling the strip. 
   
   
       21 . The method according to  claim 1  wherein the removal of the strip according to step h) comprises pushing off plate-like cut portions of the strip. 
   
   
       22 . The method according to  claim 1  wherein before the cooling according to step c) the strip has a temperature of at least 750° C. 
   
   
       23 . The method according to  claim 1  wherein after the cooling according to step c) and before coiling according to step d), the strip has a temperature of at least 25° C. and at most 400° C., preferably between 100° C. and 300° C. 
   
   
       24 . The method according to  claim 1  wherein after the heating according to step f), the strip has a temperature of at least 400° C., preferably between 400° C. and 700° C. 
   
   
       25 . The method according to  claim 1  wherein the heating of the strip according to step f) is effected so that the strip has different temperatures over its width. 
   
   
       26 . The method according to  claim 1  wherein after the cooling according to step g) and before removal according to step h), the strip has a temperature of at most 200° C., preferably between 25° C. and 200° C. 
   
   
       27 . The method according to  claim 1  wherein the steps e) to g) are carried out in reversing mode for which a coiling station located after the cooling according to step g) is used. 
   
   
       28 . The method according to  claim 1  wherein the flatness of the strip and/or the temperature of the strip is measured at least at two locations in the strip treatment installation for monitoring the quality of the strip. 
   
   
       29 . The method according to  claim 1  wherein the running speed of the strip through the strip treatment installation, the in particular zone-related strip heating, the adjustment of the straightening rolls and/or the in particular zone-related cooling are controlled or regulated by a process model. 
   
   
       30 . The method according to  claim 1  wherein during passage through the strip treatment installation, the strip is held under a defined strip tension at least in sections by means of drivers. 
   
   
       31 . (canceled) 
   
   
       32 . The method according to  claim 1  wherein a strip tension is built up by means of drivers before and after the cooling of the strip. 
   
   
       33 . The method according to  claim 1  wherein a strip is guided transversely to its longitudinal axis by means of a lateral guidance. 
   
   
       34 . The method according to  claim 33  wherein the lateral guidance takes place in the area of the cooling of the strip. 
   
   
       35 . The method according to  claim 34  wherein the lateral guidance takes place in the area of the laminar cooling of the strip. 
   
   
       36 . The method according to  claim 32  wherein lateral guidance of the strip takes place before the driver and opens after passing the strip head and closes at the strip end. 
   
   
       37 . The method according to  claim 1  wherein a measurement of the strip temperature is made by means of a low-temperature radiation pyrometer. 
   
   
       38 . The method according to  claim 1  wherein a measurement of the strip temperature is made before, inside and/or after the cooling and/or heating devices.