Ultra-hard cold-worked steel alloy

Abstract

Embodiments relate to cold-worked steel alloys with improved strength, hardness and corrosion resistance useful for creating products, such as exterior vehicle body components. Processes for preparing cold-worked steel alloys are also described.

1 . A steel alloy composition, comprising:
 Fe;   a hardness is at least about 400 HV; and   an E pit -E ocp  corrosion resistance of at least about 500 mV in a 3 wt % sodium chloride aqueous solution.   
     
     
         2 . The composition of  claim 1 , wherein the hardness is about 420 HV to about 500 HV. 
     
     
         3 . The composition of  claim 1 , wherein the E pit -E ocp  corrosion resistance is about 520 mV to about 800 mV. 
     
     
         4 . The composition of  claim 1 , further comprising a yield strength of at least about 1100 MPa. 
     
     
         5 . The composition of  claim 1 , further comprising a ductility of at least about 60° bend angle at 1.6 mm thickness. 
     
     
         6 . The composition of  claim 1 , wherein martensite formation begins at about 260 K to about 340 K. 
     
     
         7 . The composition of  claim 1 , further comprising at least about 12 vol % martensite. 
     
     
         8 . The composition of  claim 1 , further comprising a yield strength of at least about 1200 MPa. 
     
     
         9 . The composition of  claim 1 , further comprising:
 Cr: 15-18 wt. %;   Ni: 4-8 wt. %;   Mn: 1.5-6 wt. %; and   Fe: Bal.   
     
     
         10 . The composition of  claim 9 , further comprising:
 N: at most about 0.25 wt. %.   
     
     
         11 . The composition of  claim 9 , further comprising:
 Mo: at most about 2 wt. %.   
     
     
         12 . The composition of  claim 9 , further comprising:
 C: at most about 0.03 wt. %;   Si: at most about 0.75 wt. %;   P: at most about 0.045 wt. %; and   S: at most about 0.03 wt. %.   
     
     
         13 . The composition of  claim 9 , further comprising:
 Cu: at most about 0.5 wt. %;   Co: at most about 0.8 wt. %;   Al: at most about 0.03 wt. %;   Ti: at most about 0.03 wt. %; and   B: at most about 0.05 wt. %.   
     
     
         14 . The composition of  claim 13 , further comprising at most about 0.05 wt. % of each of at least one additional element, and a total of at most about 0.15 wt. % of the at least one additional element. 
     
     
         15 . A process for preparing an alloy, comprising:
 casting a steel alloy comprising Fe;   performing a processing step on the steel alloy selected from the group consisting of hot working, annealing, pickling and combinations thereof to form a processed steel alloy; and   cold working the processed steel alloy to form a cold worked steel alloy with a hardness is at least about 400 HV and an E pit -E ocp  corrosion resistance of at least about 500 mV in a 3 wt % sodium chloride aqueous solution.   
     
     
         16 . The process of  claim 15 , wherein the processed steel alloy is cold worked to a thickness reduction of at least about 30%. 
     
     
         17 . The process of  claim 15 , wherein the cold worked steel alloy has a thickness of about 0.01 mm to about 4 mm. 
     
     
         18 . The process of  claim 15 , further comprises machining the cold worked steel alloy. 
     
     
         19 . The process of  claim 15 , wherein performing the processing step on the steel alloy comprises hot working and annealing the steel alloy, and wherein hot working is performed prior to annealing the steel alloy. 
     
     
         20 . The process of  claim 15 , wherein performing the processing step on the steel alloy comprises hot working and annealing the steel alloy, and wherein annealing is performed prior to hot working the steel alloy. 
     
     
         21 . (canceled) 
     
     
         22 . A vehicle comprising a vehicle body, wherein the vehicle body comprises the steel alloy composition of  claim 1 . 
     
     
         23 . The vehicle of  claim 22 , wherein the vehicle body comprises an exterior vehicle body, and wherein the exterior vehicle body comprises the steel alloy composition. 
     
     
         24 . The vehicle of  claim 22 , wherein the steel alloy composition is uncoated. 
     
     
         25 . The vehicle of  claim 22 , wherein a corrosion protective agent is not disposed over the steel alloy composition. 
     
     
         26 . The vehicle of  claim 25 , wherein the corrosion protective agent is paint. 
     
     
         27 . The vehicle of  claim 22 , wherein the vehicle is an electric vehicle comprising an electric motor.