Press hardening steel with combination of superior corrosion resistance and ultra-high strength

Abstract

A steel composition is provided. The steel composition includes 0.02-0.45 wt. % carbon (C), 0-8 wt. % manganese (Mn), 0-8 wt. % nickel (Ni), 11-17 wt. % chromium (Cr), 1-3 wt. % silicon (Si), and a balance of iron (Fe). The combined concentration of the Mn and Ni is 2-8 wt. %. The steel composition is configured to form a surface oxide layer including oxides of at least one of the Cr or the Si after being subjected to press hardening. Press-hardened steel (PHS) fabricated from the steel composition and a method of fabricating a (PHS) component from the steel composition are also provided.

What is claimed is: 
     
         1 . A steel composition comprising:
 carbon (C) at a concentration of greater than or equal to about 0.02 wt. % to less than or equal to about 0.45 wt. %;   manganese (Mn) at a concentration of greater than or equal to 0 wt. % to less than or equal to about 8 wt. %;   nickel (Ni) at a concentration of greater than or equal to 0 wt. % to less than or equal to about 8 wt. %;   chromium (Cr) at a concentration of greater than or equal to about 11 wt. % to less than or equal to about 17 wt. %;   silicon (Si) at a concentration of greater than or equal to about 1 wt. % to less than or equal to about 3 wt. %; and   a balance of iron (Fe),   wherein the combined concentration of the Mn and the Ni is greater than or equal to about 2 wt. % to less than or equal to about 8 wt. %.   
     
     
         2 . The steel composition according to  claim 1 , wherein the steel composition is configured to form a surface oxide layer comprising oxides of at least one of the Cr or the Si after being subjected to press hardening. 
     
     
         3 . The steel composition according to  claim 1 , further comprising:
 molybdenum (Mo) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %;   tungsten (W) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %;   aluminum (Al) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %;   copper (Cu) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %; or   combinations thereof,   wherein, when the Cu and the Mo are both present in the steel composition, the combined concentration of the Cu and the Mo is less than or equal to about 5 wt. %.   
     
     
         4 . The steel composition according to  claim 3 , comprising the Cu, wherein the surface oxide layer further comprises oxides of the Cu after being subjected to press hardening. 
     
     
         5 . The steel composition according to  claim 1 , further comprising:
 vanadium (V) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. %;   niobium (Nb) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. %;   titanium (Ti) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. %; or   combinations thereof,   wherein, when at least two of the V, the Nb, or the Ti are present in the steel composition, the combined concentration of the at least two of the V, the Nb, or the Ti is less than or equal to about 0.5 wt. %.   
     
     
         6 . The steel composition according to  claim 1 , wherein the steel composition is in the form a coiled sheet. 
     
     
         7 . A press-hardened steel (PHS) comprising:
 an alloy core comprising:
 carbon (C) at a concentration of greater than or equal to about 0.02 wt. % to less than or equal to about 0.45 wt. %; 
 manganese (Mn) at a concentration of greater than or equal to 0 wt. % to less than or equal to about 8 wt. %; 
 nickel (Ni) at a concentration of greater than or equal to 0 wt. % to less than or equal to about 8 wt. %; 
 chromium (Cr) at a concentration of greater than or equal to about 11 wt. % to less than or equal to about 17 wt. %; 
 silicon (Si) at a concentration of greater than or equal to about 1 wt. % to less than or equal to about 3 wt. %; 
 molybdenum (Mo) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %; 
 tungsten (W) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %; 
 aluminum (Al) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %; 
 copper (Cu) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %; and 
 a balance of iron (Fe), 
 wherein the combined concentration of the Mn and the Ni is greater than or equal to about 2 wt. % to less than or equal to about 8 wt. %, and 
 wherein the combined concentration of the Cu and the Mo is greater than 0 wt. % to less than or equal to about 5 wt. %; and 
   an oxide layer formed on a surface of the alloy core during hot forming of the PHS, the oxide layer comprising oxides of at least one of the Cr, the Si, or the Cu.   
     
     
         8 . The PHS according to  claim 7 , wherein the combined concentration of the Cr and the Si is greater than or equal to about 15 wt. % to less than or equal to about 20 wt. %. 
     
     
         9 . The PHS according to  claim 7 , further comprising an element selected from the group consisting of:
 vanadium (V) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. %;   niobium (Nb) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. %;   titanium (Ti) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. %; and   combinations thereof,   wherein, when at least two of the V, the Nb, or the Ti are present in the steel composition, the combined concentration of the at least two of the V, the Nb, or the Ti is less than or equal to about 0.5 wt. %.   
     
     
         10 . The PHS according to  claim 7 , wherein the oxide layer is uniform and continuous. 
     
     
         11 . The PHS according to  claim 7 , wherein the oxide layer has a thickness of greater than or equal to about 5 nm to less than or equal to about 10 μm. 
     
     
         12 . The PHS according to  claim 7 , comprising a strength of greater than or equal to about 500 MPa to less than or equal to about 2000 MPa. 
     
     
         13 . The PHS according to  claim 7 , wherein the alloy core comprises a prior austenite grain size of less than or equal to about 20 μm. 
     
     
         14 . An automobile part comprising the PHS according to  claim 7 . 
     
     
         15 . A method of fabricating a press-hardened steel (PHS) component, the method comprising:
 heating a blank to a temperature of greater than or equal to about 850° C. to less than or equal to about 950° C. to form a heated blank, the blank comprising a steel composition comprising:
 carbon (C) at a concentration of greater than or equal to about 0.02 wt. % to less than or equal to about 0.45 wt. %; 
 manganese (Mn) at a concentration of greater than or equal to 0 wt. % to less than or equal to about 8 wt. %; 
 nickel (Ni) at a concentration of greater than or equal to 0 wt. % to less than or equal to about 8 wt. %; 
 chromium (Cr) at a concentration of greater than or equal to about 11 wt. % to less than or equal to about 17 wt. %; 
 silicon (Si) at a concentration of greater than or equal to about 1 wt. % to less than or equal to about 3 wt. %; 
 molybdenum (Mo) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %; 
 tungsten (W) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %; 
 aluminum (Al) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %; 
 copper (Cu) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. %; and 
 a balance of iron (Fe), 
 wherein the combined concentration of the Mn and the Ni is greater than or equal to about 2 wt. % to less than or equal to about 8 wt. %, and 
 wherein the combined concentration of the Cu and the Mo is greater than 0 wt. % to less than or equal to about 5 wt. %; 
   transferring the heated blank through air to a die, wherein the heated blank cools by greater than or equal to about 150° C. to less than or equal to about 250° C. during the transferring;   pressing the heated blank into the die to form a structure having a predetermined shape; and   quenching the structure to a temperature of less than or equal to about a martensite finish (M f ) temperature of the steel composition and greater than or equal to about room temperature to form the PHS component,   wherein the PHS component comprises:
 an alloy core comprising the C, the Mn, the Ni, the Cr, the Si, the Cu, the Mo, and the Fe; and 
 an oxide layer formed on a surface of the alloy core, the oxide layer being continuous and uniform and comprising oxides of at least one of the Cr, the Si, or the Cu, and 
   wherein the PHS component is formed without descaling and is free of a coating.   
     
     
         16 . The method according to  claim 15 , wherein the steel composition and the alloy core further comprise an element selected from the group consisting of:
 vanadium (V) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. %;   niobium (Nb) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. %;   titanium (Ti) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. %; and   combinations thereof,   wherein, when at least two of the V, the Nb, or the Ti are present in the steel composition, the combined concentration of the at least two of the V, the Nb, or the Ti is less than or equal to about 0.5 wt. %.   
     
     
         17 . The method according to  claim 15 , wherein the method is free of a secondary heat treatment after the quenching. 
     
     
         18 . The method according to  claim 15 , further comprising heat treating the PHS component, the heat treating comprising:
 heating the PHS component to a temperature of greater than or equal to about 100° C. to less than or equal to about 300° C. for greater than or equal to about 1 minute to less than or equal to about 100 minutes.   
     
     
         19 . The method according to  claim 15 , wherein the blank is substantially free of a coating. 
     
     
         20 . The method according to  claim 15 , wherein the PHS component is an automobile part selected from the group consisting of a battery tray component, a bed liner, a wheel, a pillar, a bracket, a bumper, a roof rail, a rocker rail, a rocker, a control arm, a beam, a tunnel, a step, a subframe member, a pan, a panel, and a reinforcement panel.