Apparatus for producing annealed steels and process for producing said steels

Abstract

An apparatus for producing annealed steels and annealed steels produced thereby.

1 . An apparatus for producing annealed steels comprising:
 a. an uncoiler for uncoiling steel strip material   b. a heating zone comprising:
 i. a heating section comprising:
 A. a first heating unit comprising of radiant tube burners or an induction furnace for heating the steel strip to a temperature of between 400 to 600° C., and 
 B. a second heating unit comprising one or more transversal induction furnaces for further heating the steel strip to an annealing temperature of between 500° C. to about 1000° C.; 
 
 ii. a soaking step for soaking the steel strip for a period of at most 120 seconds; 
 iii. a cooling step comprising a slow cooling zone, a fast cooling zone, and a third cooling zone, wherein the slow cooling zone is for cooling the steel strip from the annealing temperature to the fast cooling start temperature and wherein the fast cooling zone is for quickly cooling the steel strip from the fast cooling start temperature to a cooling stop temperature of about 300° C. and wherein the third cooling zone is for cooling the steel strip from the second cooling stop temperature to a temperature of between ambient temperature and 100° C.; 
   c. an optional reheating zone   d. an optional tailor annealing zone for local heat treating one or more zones areas in the longitudinal direction of the strip   e. a final cooling zone   f. a coating zone comprising:
 optionally a pickling and/or activation step 
 optionally a first cleaning step 
 an electrolytic coating step 
 optionally a second cleaning step 
 optionally a drying step 
   g. a coiler for coiling the annealed strip material.   
     
     
         2 . The apparatus according to  claim 1 , wherein the heating zone comprises a first heating unit comprising radiant tube burners for heating the steel strip to a temperature of at most about 500° C. 
     
     
         3 . The apparatus according to  claim 2 , wherein the second heating unit comprises a first transversal induction furnace for further heating the steel strip to a temperature of up to about 800° C. and a second transversal indication furnace for further heating the steel strip to an annealing temperature of at most about 1000° C. 
     
     
         4 . The apparatus according to  claim 1 , wherein the cooling rate in the fast cooling zone is at least 50° C./s. 
     
     
         5 . The apparatus according to  claim 1 , wherein the reheating zone comprises a longitudinal induction furnace for reheating the steel strip to a temperature of between 350 and 550. 
     
     
         6 . The apparatus according to  claim 1 , wherein the reheating zone comprises a partial heating zone comprises a transversal induction furnace for uniformly or locally reheating the steel strip to a temperature of between 700 to 900° C. 
     
     
         7 . The apparatus according to  claim 1 , wherein the apparatus comprises a tailor annealing zone for local heat treating one or more areas in the longitudinal direction of the strip. 
     
     
         8 . The apparatus according to  claim 1 , wherein galvanisation of the steel is performed in the electrolytic coating step. 
     
     
         9 . A process for producing an advanced high strength steel using the device according to  claim 1  comprising:
 a. uncoiling steel strip material using an uncoiler 
 b. heating the steel strip in a heating zone comprising:
 i. a heating section comprising:
 A. heating the steel strip to a temperature of between 400 to 600° C. in a first heating unit comprising radiant tube burners or an induction furnace, and 
 B. further heating the steel strip to an annealing temperature of between 500° C. to about 1000° C. in a second heating unit comprising one or more transversal induction furnaces; 
 
 ii. a soaking step for soaking the steel strip for a period of at most 120 seconds; 
 iii. a cooling step comprising a slow cooling zone, a fast cooling zone, and a third cooling zone, wherein the slow cooling zone cools the steel strip from the annealing temperature to the fast cooling start temperature and wherein the fast cooling zone quickly cools the steel strip from the fast cooling start temperature to a cooling stop temperature of about 300° C., and wherein the third cooling zone cools the steel strip from the second cooling stop temperature to a temperature of between ambient temperature and 100° C.; 
 
 c. optionally reheating in an optional reheating zone 
 d. optional tailor annealing in an optional tailor annealing zone for local heat treating one or more zones areas in the longitudinal direction of the strip 
 e. cooling in a final cooling zone 
 f. coating in a coating zone comprising:
 optionally a pickling and/or activation step 
 optionally a first cleaning step 
 an electrolytic coating step 
 optionally a second cleaning step 
 optionally a drying step 
 
 g. coiling the annealed strip material using a coiler for coiling the annealed strip material. 
 
     
     
         10 . The process of  claim 9 , comprising producing a tailor annealed advanced high strength steel with varying properties over the width of the strip as a result of local heat treating one or more areas or zones in the longitudinal direction of the strip using the tailor annealing zone for local heat treating one or more areas in the longitudinal direction of the strip. 
     
     
         11 . The process according to  claim 10 , wherein the zones with the desired variations of the mechanical properties over the width of the strip and parallel to the rolling direction are at least 50 mm wide. 
     
     
         12 . The process according to  claim 9 , wherein the strip is electrolytically galvanised in-line. 
     
     
         13 . The process according to  claim 9 ,
 wherein the strip is heated to an intermediate temperature of between 400 and 600° C. in the first heating unit and heated to a temperature of at most 1000° C. in second heating unit,   soaked for at most 120 s and   cooled in the cooling section in a slow cooling section from the soaking temperature to the fast cooling start temperature of just above Ar3   followed by cooling from the temperature just above Ar3 to a temperature of about 300° C. in the fast cooling section at a cooling rate of at least 50° C./s   followed by cooling the strip in the third cooling section to a temperature below the temperature where no further transformation takes place.   
     
     
         14 . The process according to  claim 9 , wherein the strip is a cold-rolled steel strip heated to intermediate temperature of between 400 and 600° C. in the first heating unit and heated to temperature of between 600 and 700° C., heat treated for 10 to 60 s followed by cooling to produce a recovery annealed cold-rolled high strength steel. 
     
     
         15 . Annealed steel produced using the apparatus of  claim 1 . 
     
     
         16 . Annealed steel produced using the process of  claim 9 . 
     
     
         17 . The apparatus according to  claim 1 , wherein the reheating zone comprises a longitudinal induction furnace for reheating the steel strip to a temperature of between 400 and 500° C. 
     
     
         18 . The apparatus according to  claim 1 , wherein the reheating zone comprises a partial heating zone comprises a transversal induction furnace for uniformly or locally reheating the steel strip to a temperature of between 750 to 850° C. 
     
     
         19 . The apparatus according to  claim 1 , wherein the apparatus comprises a tailor annealing zone is located behind the heating zone. 
     
     
         20 . The process of  claim 9 , comprising producing a tailor annealed advanced high strength steel with varying properties over the width of the strip as a result of local heat treating one or more areas or zones in the longitudinal direction of the strip using galvanisation of the steel performed in the electrolytic coating step. 
     
     
         21 . Annealed steel produced according to the process of  claim 9 .