Steels for sour service environments
Embodiments of the present application are directed towards steel compositions that provide improved properties under corrosive environments. Embodiments also relate to protection on the surface of the steel, reducing the permeation of hydrogen. Good process control, in terms of heat treatment working window and resistance to surface oxidation at rolling temperature, are further provided.
1. A steel composition, comprising:
carbon (C) between about 0.15 and 0.40 wt. %;
manganese (Mn) between about 0.1 and 1 wt. %;
chromium (Cr) between about 0.4 and 1.5 wt. %;
molybdenum (Mo) between about 0.1 and 1.5 wt. %;
wherein the average packet size, d packet of the steel composition, the precipitate size of the steel composition, and the shape factor of the precipitates are selected to improve the sulfur stress corrosion resistance of the composition;
wherein the average packet size, d packet of the steel composition is less than about 3μm;
wherein the composition possesses precipitates having a particle diameter, d p , greater than about 70 nm and which possess an average shape factor of greater than or equal to about 0.62; and
wherein the shape factor is calculated according to 4Aπ/P 2 , where A is area of the particle projection and P is the perimeter of the particle projection.
2. The steel composition of claim 1 , wherein the yield stress of the steel composition ranges between about 120 to 140 ksi.
3. The steel composition of claim 1 , wherein the sulfur stress corrosion (SSC) resistance of the composition is about 720 h as determined by testing in accordance with NACE TM0177, test Method A, at stresses of about 85% Specified Minimum Yield Strength (SMYS) for full size specimens.
4. The steel composition of claim 1 , wherein the steel is formed into a pipe.
5. The steel composition of claim 1 , further comprising aluminum (Al) up to about 0.1 wt. %.
6. The steel composition of claim 1 , further comprising titanium (Ti) up to about 0.05 wt. %.
7. The steel composition of claim 1 , further comprising vanadium (V) up to about 0.05 wt. %.
8. The steel composition of claim 1 , further comprising silicon (Si) between about 0.15 and 0.5 wt. %.