Hydrogen-induced-cracking resistant and sulphide-stress-cracking resistant steel alloy

Abstract

A steel alloy, for use in casing for oil and gas wells in low pH environments. The steel alloy has a carbon range by weight of 0.15% to 0.35%, a manganese range by weight of 0.60% to 1.10%, a molybdenum range by weight of 0.15% to 0.65%, a calcium range by weight of 0.0045% and a sulfur range by weight of less than 0.002%. The steel alloy also has, by weight, a chromium range of less than 0.50%, and an aluminum range of 0.010% to 0.080%.

What is claimed is:  
     
         1 . A rolled steel alloy characterized in that the alloy comprises by weight 
 a carbon range of 0.15% to 0.35%,    a manganese range of 0.60% to 1.10%,    a molybdenum range of at least 0.15%,    a calcium range of less than or equal to 0.0045%, and    a sulfur range of less than 0.002%;    wherein molybdenum is included in the alloy to harden the alloy, so as to enable boron and titanium to be substantially excluded from the alloy, thereby substantially precluding the formation of boron nitride and titanium nitride.    
     
     
         2 . A rolled steel alloy as defined in  claim 1 , further characterized in that 
 the carbon range by weight is 0.20% to 0.30%,    the manganese range by weight is 0.65% to 0.75%,    the molybdenum range by weight is 0.45% to 0.55%, and    the sulfur range by weight is less than 0.001%.    
     
     
         3 . A rolled steel alloy as defined in  claim 2 , further characterized in that the alloy comprises by weight 
 an aluminum range of 0.010% to 0.080%, and    a calcium range of 0.0020% to 0.0045%.    
     
     
         4 . A rolled steel alloy as defined in  claim 3 , further characterized in that the alloy comprises by weight 
 a chromium range of 0.2% to 0.3%.    
     
     
         5 . A rolled steel alloy as defined in  claim 4 , further characterized in that the alloy comprises by weight 
 a silicon range of 0.15% to 0.25%.    
     
     
         6 . A casing for transporting fluids such as oil, gas and steam, wherein the casing is made from a rolled steel alloy characterized in that said alloy comprises by weight 
 a carbon range of 0.15% to 0.35%,    a manganese range of 0.60% to 1.10%,    a molybdenum range of at least 0.15%,    a calcium range of less than or equal to 0.0045%, and    a sulfur range of less than 0.002%;    wherein molybdenum is included in the alloy to harden the alloy, so as to enable boron and titanium to be substantially excluded from the alloy, thereby substantially precluding the formation of boron nitride and titanium nitride.    
     
     
         7 . The casing of  claim 6  further characterized in that 
 the carbon range by weight is 0.15% to 0.30%,  
 the manganese range by weight is 0.65% to 0.75%  
 the molybdenum range by weight is 0.45% to 0.55%, and  
 the sulfur range by weight is less than 0.001%.  
 
     
     
         8 . The casing of  claim 7 , further characterized in that the alloy comprises by weight 
 an aluminum range of 0.20% to 0.040%, and    a calcium range of 0.0020% to 0.0045%.    
     
     
         9 . The casing of  claim 8  further characterized in that the alloy comprises by weight 
 a chromium range of 0.20% to 0.30%.  
 
     
     
         10 . The casing of  claim 9 , further characterized in that the alloy comprises by weight 
 a silicon range of 0.15% to 0.25%.    
     
     
         11 . The casing of  claim 6 , further characterized in that 
 the carbon range by weight is 0.18% to 0.27%,    the manganese range by weight is 0.70% to 0.95%,    the molybdenum range by weight is 0.35% to 0.55%, and    the sulfur range by weight is less than 0.001%.    
     
     
         12 . The casing of  claim 11 , further characterized in that the alloy comprises by weight 
 a chromium range of 0.20% to 0.30%.    
     
     
         13 . The casing of  claim 12  further characterized in that the alloy comprises by weight 
 an aluminum range of 0.020% to 0.040%, and  
 a calcium range of 0.0020% to 0.0045%.  
 
     
     
         14 . The casing of  claim 13 , further characterized in that the alloy comprises by weight 
 a silicon range of 0.15% to 0.25%.    
     
     
         15 . A method of transporting oil and gas extracted from oil and gas wells wherein a casing is installed to carry the oil and gas, said casing being made from a rolled steel alloy characterized in that said alloy comprises by weight 
 a carbon range of 0.15% to 0.35%,    a manganese range of 0.60% to 1.10%,    a molybdenum range of at least 0.15%,    a calcium range of less than or equal to 0.0045%, and    a sulfur range of less than 0.002%; and,    wherein molybdenum is included in the alloy to harden the alloy, so as to enable boron and titanium to be substantially excluded from the alloy, thereby substantially precluding the formation of boron nitride and titanium nitride.    
     
     
         16 . A rolled steel alloy as defined in  claim 1 , further characterized in that 
 the carbon range by weight is 0.18% to 0.27%,    the manganese range by weight is 0.70% to 0.95%,    the molybdenum range by weight is 0.35% to 0.55%, and    the sulfur range by weight is less than 0.001%.    
     
     
         17 . The rolled steel alloy as defined in  claim 16 , further characterized in that the alloy comprises by weight 
 an aluminum range of 0.020% to 0.040%, and    a calcium range of 0.0020% to 0.0045%.    
     
     
         18 . The rolled steel alloy as defined in  claim 17 , further characterized in that the alloy comprises by weight 
 a chromium range of 0.20% to 0.30%.    
     
     
         19 . The rolled steel alloy as defined in  claim 18 , further characterized in that the alloy comprises by weight 
 a silicon range of 0.15% to 0.25%.