Steels for sour service environments

1. A steel composition, comprising:

carbon (C) between about 0.2 and 0.3 wt. %;

manganese (Mn) between about 0.1 and 1 wt. %;

silicon (Si) between about 0 and 0.5 wt. %;

chromium (Cr) between about 0.4 and 1.5 wt. %;

molybdenum (Mo) between about 0.1 and 1 wt. %;

niobium (Nb) between about 0 and 0.1 wt. %;

aluminum (Al) between about 0 and 0.1 wt. %;

calcium (Ca) between about 0 and 0.01 wt. %;

boron (B) less than about 100 ppm;

titanium (Ti) between about 0 and 0.05 wt. %;

tungsten (W) between about 0.1 and 1.5 wt. %;

vanadium (V) between about 0 and no more than about 0.05 wt. %;

copper (Cu) between about 0 and no more than about 0.15 wt. %;

oxygen (O) less than about 200 ppm;

nitrogen (N) less than about 0.01 wt. %;

sulfur (S) less than about 0.003 wt. %; and

phosphorus (P) less than about 0.015 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 3 μm;

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 steel composition satisfies the equation Mo/10+Cr/12+W/25+Nb/3+25*B between about 0.05 wt. % and 0.39 wt. %.

3. The steel composition of claim 1 , wherein the yield stress of the steel composition ranges between about 120 to 140 ksi.

4. 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.

5. The steel composition of claim 1 , comprising:

carbon (C) between about 0.2 and 0.3 wt. %;

manganese (Mn) between about 0.2 and 0.5 wt. %;

silicon (Si) between about 0.15 and 0.4 wt. %;

chromium (Cr) between about 0.4 and 1 wt. %;

molybdenum (Mo) between about 0.3 and 0.8 wt. %;

niobium (Nb) between about 0.02 and 0.06 wt. %;

aluminum (Al) between about 0.02 and 0.07 wt. %;

calcium (Ca) between about 0 and 0.01 wt. %;

boron (B) between about 10 and 30 ppm;

titanium (Ti) between about 0.1 and 0.03 wt. %;

tungsten (W) between about 0.2 and 0.6 wt. %;

vanadium (V) between about 0 and no more than about 0.05 wt. %;

copper (Cu) between about 0 and no more than about 0.08 wt. %;

oxygen (O) less than about 200 ppm;

nitrogen (N) less than about 0.01 wt. %;

sulfur (S) less than about 0.002 wt. %; and

phosphorus (P) less than about 0.010 wt. %.

6. The steel composition of claim 1 , wherein the steel is formed into a pipe.

7. A steel composition, comprising:

carbon (C), molybdenum (Mo), chromium (Cr), tungsten (W), niobium (Nb), and boron (B);

the amount of each of the elements provided, in wt. % of the total steel composition, such that the steel composition satisfies the formula:

Mo/10+Cr/12+W/25+Nb/3+25*B between about 0.05 and 0.39 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.

8. The steel composition of claim 7 , wherein the steel composition satisfies the equation Mo/10+Cr/12+W/25+Nb/3+25*B between about 0.10 wt. % and 0.26 wt. %.

9. The steel composition of claim 7 , wherein the steel composition exhibits a substantially linear relationship between mode I sulfide stress corrosion cracking toughness (K ISSC ) and yield strength.

10. The steel composition of claim 7 , wherein the microstructure of the steel composition comprises greater than about 95 vol. % martensite and less than about 5 vol. % bainite, on the basis of the total volume of the steel composition.

11. The steel composition of claim 7 , comprising:

carbon (C) between about 0.2 and 0.3 wt. %;

chromium (Cr) between about 0.4 and 1 wt. %;

molybdenum (Mo) between about 0.3 and 0.8 wt. %;

niobium (Nb) between about 0.02 and 0.06 wt. %;

boron (B) 10 to 30 ppm;

tungsten (W) between about 0.2 and 0.6 wt. %;

on the basis of the total weight of the steel composition.

12. The steel composition of claim 11 , further comprising:

manganese (Mn) between about 0.2 and 0.5 wt. %;

silicon (Si) between about 0.15 and 0.4 wt. %;

aluminum (Al) between about 0.02 and 0.07 wt. %;

calcium (Ca) between about 0 and 0.005 wt. %;

titanium (Ti) between about 0.01 and 0.03 wt. %;

vanadium (V) between about 0 and no more than about 0.05 wt. %;

copper (Cu) between about 0 and no more than about 0.15 wt. %;

oxygen (O) less than about 200 ppm;

nitrogen (N) less than about 0.006 wt. %;

sulfur (S) less than about 0.002 wt. %; and

phosphorus (P) less than about 0.01 wt. %.

13. A steel composition, comprising:

carbon (C) between about 0.2 and 0.3 wt. %;

manganese (Mn) between about 0.1 and 1 wt. %;

chromium (Cr) between about 0.4 and 1.5 wt. %;

silicon (Si) between about 0.15 and 0.5 wt. %;

molybdenum (Mo) between about 0.1 and 1 wt. %;

tungsten (W) between about 0.1 and 1.5 wt. %;

niobium (Nb) between about 0 and 0.1 wt. %; and

boron (B) less than about 100 ppm;

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 3 μm;

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.

14. The steel composition of claim 13 , further comprising aluminum (Al) up to about 0.1 wt. %.

15. The steel composition of claim 13 , further comprising titanium (Ti) up to about 0.05 wt. %.

16. The steel composition of claim 13 , further comprising vanadium (V) up to about 0.05 wt. %.

17. The steel composition of claim 13 , further comprising nitrogen (N) less than about 0.01 wt. %.

18. The steel composition of claim 13 , wherein the resulting steel has a yield strength between 120 to 140 ksi.

19. The steel composition of claim 13 , 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.