High copper low alloy steel sheet

Abstract

A high copper low alloy steel sheet made by the steps comprising preparing a molten melt producing an as-cast low alloy steel comprising by weight, between 0.02% and 0.3% carbon, between 0.10% and 1.5% manganese, between 0.01% and 0.5% silicon, less than 0.04% sulfur, greater than 0.01% and less than or equal to 0.15% phosphorus, less than 0.05% aluminum, more than 0.20% copper, less than 0.03% tin, and less than 0.10% nickel, and the remainder iron and impurities resulting from melting, and solidifying the molten melt into sheet less than 10 mm in thickness in a non-oxidizing atmosphere to below 1080° C. The copper content may be between 0.2% and 2.0% by weight. The high copper low alloy steel may also have a corrosion index (I) of at least 6.0 in accordance with ASTM G101 where: I=26.01 (% Cu)+3.88 (% Ni)+1.20 (% Cr)+1.49 (% Si)+17.28 (% P)−7.29 (% Cu)(% Ni)−9.10 (% Ni)(% P)−33.39 (% Cu). The high copper low alloy steel may be produced by twin roll casting, and may have thickness less than 5 mm or less than 2 mm in thickness.

1 . A high copper low alloy steel sheet made by the steps comprising: 
 (a) preparing a molten melt producing an as-cast low alloy steel comprising 
 (i) by weight, between 0.02% and 0.3% carbon, between 0.10% and 1.5% manganese, between 0.01% and 0.5% silicon, less than 0.04% sulfur, greater than 0.01% and less than or equal to 0.15% phosphorus, less than 0.05% aluminum, more than 0.20% copper, less than 0.03% tin, and less than 0.10% nickel;  
 (ii) the remainder iron and impurities resulting from melting;  
   (b) solidifying and cooling the molten melt into a sheet less than 10 mm in thickness in a non-oxidizing atmosphere to below 1080° C.    
     
     
         2 . The high copper low alloy steel sheet as claimed in  claim 1  wherein the corrosion index (I) is at least 6.0 where: 
           I =26.01(% Cu)+3.88(% Ni)+1.20(% Cr)+1.49(% Si)+17.28(% P)−7.29(% Cu)(% Ni)−9.10(% Ni)(% P)−33.39(% Cu). 
     
     
         3 . The high copper low alloy steel sheet as claimed in  claim 1  wherein the total of the % by weight of copper is between 0.2 and 2.0.  
     
     
         4 . The high copper low alloy steel sheet as claimed in  claim 1  wherein the thickness of the sheet is less than 5 mm in thickness.  
     
     
         5 . The high copper low alloy steel sheet as claimed in  claim 1  wherein the thickness of the sheet is less than 2 mm in thickness.  
     
     
         6 . A high copper low alloy steel sheet made by the steps comprising: 
 (a) preparing a molten melt producing an as-cast low alloy steel comprising 
 (i) by weight, between 0.02% and 0.3% carbon, between 0.10% and 1.5% manganese, between 0.01% and 0.5% silicon, less than 0.04% sulfur, greater than 0.01% and less than or equal to 0.15% phosphorus, less than 0.05% aluminum, more than 0.20% copper, less than 0.03% tin, and less than 0.10% nickel;  
 (ii) The remainder iron and impurities resulting from melting;  
   (b) forming the melt into a casting pool supported on casting surfaces of a pair of cooled casting rolls having a nip therebetween;    (c) counter rotating the casting rolls to form a thin cast sheet of less than 10 mm in thickness extending downwardly from the nip; and    (d) cooling the cast sheet to below 1080° C. in a non-oxidizing atmosphere.    
     
     
         7 . The high copper low alloy steel sheet as claimed in  claim 6  wherein the corrosion index (I) is at least 6.0 where: 
           I =26.01(% Cu)+3.88(% Ni)+1.20(% Cr)+1.49(% Si)+17.28(% P)−7.29(% Cu)(% Ni)−9.10(% Ni)(% P)−33.39(% Cu). 
     
     
         8 . The high copper low alloy steel sheet as claimed in  claim 6  wherein the total of the percent by weight of copper is between 0.2 and 2.0.  
     
     
         9 . The high copper low alloy steel sheet as claimed in  claim 6  wherein the thickness of the thin cast sheet is less than 5 mm in thickness.  
     
     
         10 . The high copper low alloy steel sheet as claimed in  claim 6  wherein the thickness of the thin cast sheet is less than 2 mm in thickness.  
     
     
         11 . A method of making a high copper low alloy steel sheet comprising the steps of: 
 (a) preparing a molten melt producing an as-cast low alloy steel comprising 
 (i) by weight, between 0.02% and 0.3% carbon, between 0.10% and 1.5% manganese, between 0.01% and 0.5% silicon, less than 0.04% sulfur, greater than 0.01% and less than or equal to 0.15% phosphorus, less than 0.05% aluminum, more than 0.20% copper, less than 0.03% tin, and less than 0.10% nickel;  
 (ii) the remainder iron and impurities resulting from melting;  
   (b) solidifying the molten melt into sheet less than 10 mm in thickness in a non-oxidizing atmosphere to below 1080° C.    
     
     
         12 . The method of making a high copper low alloy steel sheet as claimed in  claim 11  wherein the corrosion index (I) is at least 6.0 where: 
           I =26.01(% Cu)+3.88(% Ni)+1.20(% Cr)+1.49(% Si)+17.28(% P)−7.29(% Cu)(% Ni)−9.10(% Ni)(% P)−33.39(% Cu). 
     
     
         13 . The method of making a high copper low alloy steel sheet as claimed in  claim 11  wherein the total of the percent by weight of copper is between 0.2 and 2.0.  
     
     
         14 . The method of making a high copper low alloy steel sheet as claimed in  claim 11  wherein the thickness of the thin cast strip is less than 5 mm in thickness.  
     
     
         15 . The method of making a high copper low alloy steel sheet as claimed in  claim 11  wherein the thickness of the thin cast strip is less than 2 mm in thickness.  
     
     
         16 . A method of making a high copper low alloy steel sheet comprising the steps of: 
 (a) preparing a molten melt producing an as-cast low alloy steel comprising 
 (i) by weight, between 0.02% and 0.3% carbon, between 0.10% and 1.5% manganese, between 0.01% and 0.5% silicon, less than 0.04% sulfur, greater than 0.01% and less than or equal to 0.15% phosphorus, less than 0.05% aluminum, more than 0.20% copper, less than 0.03% tin, and less than 0.10% nickel;  
 (ii) the remainder iron and impurities resulting from melting;  
   (b) forming the melt into a casting pool supported on casting surfaces of a pair of cooled casting rolls having a nip therebetween;    (c) counter rotating the casting rolls to form a thin cast sheet of less than 10 mm in thickness extending downwardly from the nip;    (d) cooling the cast sheet to below 1080° C. in a non-oxidizing atmosphere.    
     
     
         17 . The method of making a high copper low alloy steel sheet as claimed in  claim 16  wherein the corrosion index (I) is at least 6.0 where: 
           I =26.01(% Cu)+3.88(% Ni)+1.20(% Cr)+1.49(% Si)+17.28(% P)−7.29(% Cu)(% Ni)−9.10(% Ni)(% P)−33.39(% Cu). 
     
     
         18 . The method of making a high copper low alloy steel sheet as claimed in  claim 16  wherein the total of the percent by weight of copper is between 0.2 and 2.0.  
     
     
         19 . The method of making a high copper low alloy steel sheet as claimed in  claim 16  wherein the thickness of the thin cast strip is less than 5 mm in thickness.  
     
     
         20 . The method of making a high copper low alloy steel sheet as claimed in  claim 16  wherein the thickness of the thin cast strip is less than 2 mm in thickness.