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

Abstract

A method for treating a steel strip uses a treatment liquid in a treatment station having at least a spray section, an immersion section, and a common collector for the liquid, the steel. strip including stainless steel, top surface, and a bottom surface, and being continuous, oriented substantially horizontally, both in its 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, first, spraying the liquid, using one or more spray nozzles, onto the steel strip's top and bottom surfaces while in the spray section and, second, immersing the steel strip in the liquid while in the immersion section, wherein, while treating the steel strip, continuous pumping the liquid out of the common collector and through both the spray section and the immersion section.

1 . A method for treating a steel strip, using a first treatment liquid in a first treatment station, the treatment station including a first treatment tank including a first spray section, and a first immersion section, and a first common collector for the first treatment liquid,
 the steel strip including stainless steel, 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 first treatment station in a transport direction parallel to the longitudinal direction of the steel strip;   spraying, using spraying nozzles, the first treatment liquid onto the top and bottom surfaces of the steel strip while the steel strip is in the first spray section;   immersing the steel strip in the first treatment liquid while the steel strip is in the first immersion section; and   while treating the steel strip, continuously pumping the first treatment liquid is out of the first common collector and through both the first spray section and the first immersion section.   
     
     
         2 . The method of  claim 1 , wherein the first 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 first treatment liquid while located within the effective spray length,
 wherein the first 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 versus 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 first spray section is located upstream or downstream of the first immersion section. 
     
     
         5 . The method of  claim 1 , further comprising, using a second treatment liquid in a second treatment station including a second treatment tank including a second spray section, a second immersion section, and a second common collector for the further treatment liquid;
 transporting the steel strip continuously through the second treatment station in the transport direction;   spraying, using spray nozzles, the second treatment liquid onto the top and bottom surfaces of the steel strip while the steel strip is in the second spray section;   immersing the steel strip in the second treatment liquid while the steel strip is in the second immersion section of the further treatment station; and   while treating the steel strip, continuously pumping the second treatment liquid out of the second common collector and through both the second spray section and the second immersion section,   wherein the spraying and immersing in the second treatment liquid precede or follow the spraying and immersing in the first treatment liquid.   
     
     
         6 . The method of  claim 5 , wherein the first treatment liquid and/or the second 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,   MeCl 2  in a concentration range from 30 g/L to 300 g/L.   
     
     
         7 . A system for treating a steel strip including stainless 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, using a treatment liquid in a treatment station, the system comprising:
 a treatment station including a treatment tank including a spray section, an immersion section, and a common collector for the treatment liquid: and   spray nozzles configured to spray that the treatment liquid onto the top and bottom surfaces of the steel strip,   wherein the system is configured to transport 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, 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 of the treatment station.   
     
     
         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 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 according to one of  claim 7 , wherein, along the transport direction of the steel strip, the spray section is located upstream or downstream of the immersion section. 
     
     
         10 . The system of  claim 7 , wherein the common collector 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 second treatment liquid in a second treatment station including a second treatment tank including a second spray section, a second immersion section, and a second common collector for the second treatment liquid; and   second spray nozzles configured to spray the second treatment liquid onto the top and bottom surface of the steel strip,   wherein the system is configured such that the steel strip is transported continuously through the second treatment station in the transport direction such that   the second treatment liquid is sprayed onto the top and bottom surfaces of the steel strip while the steel strip is in the second spray section, and such that   the steel strip is immersed in the second treatment liquid while the steel strip is in the second immersion section,   wherein the system is configured such that the second treatment liquid is continuously pumped out of the second common collector and through both the second spray section and the second immersion section.   
     
     
         13 . The system of  claim 11 , further comprising:
 a third treatment liquid in a third treatment station including a third treatment tank including a third spray section, a third immersion section, and a third common collector for the third treatment liquid.   
     
     
         14 . The system of  claim 12 , wherein the treatment liquid and/or the second 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   MeCl 2  in a concentration range of from 30 g/L to 300 g/L.