Method and system of treating a carbon steel strip, especially for a pickling treatment

Abstract

A method, for treating a steel strip with a treatment liquid in a station having at least a spray section, an immersion section, and a common collector for treatment liquid, the steel strip having carbon steel with top and bottom surfaces and being a continuous steel strip, oriented substantially horizontally, both in longitudinal and transverse directions, involves transporting the steel strip continuously through the station in a transport direction parallel to the steel strip's longitudinal direction; spraying treatment liquid with spray nozzles onto the steel strip's top and bottom surfaces while in the spray section of the station; immersing the steel strip in the treatment liquid while in the immersion section of the station; and, while treating the steel strip, continuously pumping the treatment liquid out of the common collector and through both the spray section and the immersion section of the station.

1 : A method for treating a steel strip using a first treatment liquid in a treatment station having at least a treatment tank with a spray section and an immersion section, and a common collector for the first treatment liquid,
 the steel strip including carbon steel, and having a top surface, and a bottom surface, and being a continuous steel strip, oriented substantially horizontally, both in its longitudinal and transverse directions,   the method comprising:   transporting the steel strip continuously through the treatment station in a transport direction, the transport direction being parallel to the longitudinal direction of the steel strip;   spraying, using spray nozzles, the first treatment liquid onto the top and bottom surfaces of the steel strip while the steel strip is in the spray section;   immersing the steel strip in the first treatment liquid while the steel strip is in the immersion section; and   while treating the steel strip, continuously pumping the first treatment liquid out of the common collector and through both the spray section and the immersion section.   
     
     
         2 : The method of  claim 1 , wherein the spray section includes an effective spray length in parallel to the longitudinal direction of the steel strip such that, during the spraying, the top and bottom surfaces of the steel strip receive the treatment liquid while located within the effective spray length,
 wherein the immersion section includes an effective immersion length in parallel to the longitudinal direction of the steel strip such that, during the immersing, the steel strip is immersed with its top and bottom surfaces in the first treatment liquid while located within the effective immersion length,   wherein the effective spray length and the effective immersion length have a ratio in a range of from 30:70 to 70:30.   
     
     
         3 : The method of  claim 2 , wherein the effective spray length and hence the ratio of the effective spray length vs. the effective immersion length is varied by activating only a part of the spray nozzles. 
     
     
         4 : The method of  claim 1 , wherein, along the transport direction of the steel strip, the spray section is located upstream or downstream of the immersion section. 
     
     
         5 : The method of  claim 1 , further comprising, using a further treatment liquid in a further treatment station, the further treatment station including a further treatment tank including a further spray section and a further immersion section, and the further treatment station including a further common collector for the further treatment liquid;
 transporting the steel strip continuously through the further treatment station in the transport direction;   spraying, using spray nozzles, the further treatment liquid onto the top and bottom surfaces of the steel strip while the steel strip is in the further spray section;   immersing the steel strip in the further treatment liquid while the steel strip is in the further immersion section; and   while treating the steel strip, continuously pumping the further treatment liquid out of the further common collector and through both the further spray section and the further immersion section,   wherein the spraying and immersing with the further treatment liquid are preceding or subsequent to the spraying and immersing with the first treatment liquid.   
     
     
         6 : The method of  claim 5 , wherein the first and/or the further treatment liquid comprises
 hydrochloric acid in a concentration in a range of from 150 g/L to 250 g/L,   FeCl 3  in a concentration in a range of from 10 g/L to 35 g/L, and   FeCl 2  in a concentration in a range of from 30 g/L to 300 g/L.   
     
     
         7 : A system for treating a steel strip using a treatment liquid in a treatment station, the system comprising:
 the treatment station including a treatment tank including a spray section, an immersion section, and a common collector for the treatment liquid,   wherein the steel strip includes carbon steel, and has top surface, and a bottom surface, and is a continuous steel strip oriented substantially horizontally, both in its longitudinal and transverse directions,   wherein the system is configured to transport the steel strip continuously through the treatment station in a transport direction parallel to the longitudinal direction of the steel strip, such that   the treatment liquid is sprayed onto the top and bottom surfaces of the steel strip while the steel strip is in the spray section, and   the steel strip is immersed in the treatment liquid while the steel strip is in the immersion section,   wherein the system is configured such that the treatment liquid is continuously pumped out of the common collector and through both the spray section and the immersion section,   wherein the system includes spray nozzles such that the treatment liquid is sprayed onto the top and bottom surfaces of the steel strip using the spray nozzles.   
     
     
         8 : The system of  claim 7 , wherein
 the spray section includes an effective spray length in parallel to the longitudinal direction of the steel strip such that the top and bottom surfaces of the steel strip receive the treatment liquid while being located within the effective spray length,   wherein the immersion section includes an effective immersion length in parallel to the longitudinal direction of the steel strip such that the steel strip is immersed, with its top and bottom surfaces, in the treatment liquid while being located within the effective immersion length,   wherein the effective spray length and the effective immersion length have a ratio in a range of from 30:70 to 70:30.   
     
     
         9 : The system of  claim 7 , wherein, along the transport direction of the steel strip, the spray section is located upstream or downstream with respect to the immersion section. 
     
     
         10 : The system of  claim 7 , wherein the common collector of both the spray section and the immersion section is separated from the treatment tank of the treatment station. 
     
     
         11 : The system of  claim 7 , wherein the common collector is integrated with the treatment tank. 
     
     
         12 : The system of  claim 7 , further comprising:
 a further treatment liquid in a further treatment station including a further common collector for the further treatment liquid and a further treatment tank including a further spray section and a further immersion section,   wherein the system is configured such that the steel strip is transported continuously through the further treatment station in the transport direction such that   the further treatment liquid is sprayed onto the top surface of the steel strip and onto the bottom surface of the steel strip while the steel strip is in the further spray section of the further treatment station,   the steel strip is immersed in the further treatment liquid while the steel strip is in the further immersion section of the further treatment station,   wherein the system is configured such that the further treatment liquid is continuously pumped out of the further common collector and through both the further spray section and the further immersion section of the further treatment station,   wherein the system includes further spray nozzles such that the further treatment liquid is sprayed onto the top and bottom surfaces of the steel station using the further spray nozzles.   
     
     
         13 : The system of  claim 7 , further comprising:
 a third treatment liquid in a third treatment station including a third common collector for the third treatment liquid, and a third treatment tank including a third spray section and a third immersion section.   
     
     
         14 : The system of  claim 13 , wherein the treatment liquid and/or the further treatment liquid and/or the third treatment liquid comprises
 hydrochloric acid in a concentration range of from 150 g/L to 250 g/L,   FeCl 3  in a concentration range of from 10 g/L to 35 g/L, and   FeCl 2  in a concentration range of from 30 g/L to 300 g/L.