Steels_ Metallurgy and Applications, Third Edition

196 Steels: Metallurgy and Applications

and therefore a minimum level of manganese must be maintained, particularly in

linepipe for arctic service.

Certain alloy additions are also effective in improving the resistance to HIC,

notably copper and nickel. At pH levels above 5, these elements form protective

films which prevent the diffusion of hydrogen into the steel. However, at pH

levels below 5, these protective films are not formed and therefore these alloy

additions show little advantage in the NACE test, outlined earlier. On the other

hand, copper additions of 0.2-0.3% are extremely beneficial in preventing HIC,

as determined by the B P test.

In summary, linepipe steels with resistance to HIC embody the following

features:

1. Low levels of carbon, sulphur and phosphorus.


2. Additions of calcium or rare earth metals to globularize the sulphide inclu-
   sions.


3. Low levels of oxide inclusions.


4. Freedom from segregation so as to avoid bainitic or martensitic bands.


5. Additions of small amounts of copper or chromium.

References

1. Hall, E.O. Proc. Phys. Soc. Series B, 64, 747 (1951).


2. Petch, N.J. Proc. Swampscott Conf., MIT Press, p. 54 (1955).


3. Pickering, F.B. Physical Metallurgy and the Design of Steels, Applied
   Science Publishers.


4. Piekering, F.B. and Gladman, T. ISI Special Report 81 (1961).


5. Irvine, K.J., Piekering, F.B. and Gladman, T. JISI, 205, 161 (1967).


6. Gladman, T., Dulieu, D. and Mclvor, I.D. In Proc. MicroAlloying 75,
   (Washington, 1975), Union Carbide, p. 25 (1975).
   7'. Vanderbeck, R.W. Weld J., 37 (1958).


7. Sellars, C.M. In Proc. HSLA Steels: Metallurgy and Applications (eds
   Gray, J.M., Ko, T., Zhang Shouhua, Wu Baorong and Xie Xishan) (Beijing,

1985. ASM.

9. Tamura, I., Ouchi, C., Tanaka, T. and Sekine, H. Thermomechanical
   Processing of High Strength Low Alloy Steels, Butterworths (1988).


10. Cuddy, L.J. In Proc. Thermomechanical Processing of Microalloyed
    Austenite (eds Deardo, A.J., Ratz, G.A. and Wray, P.J.) (Warrendale Pa,

1982. Met. Soc. AIME (1982).

11. Cohen, M. and Hansen, S.S. In Proc. HSLA Steels: Metallurgy and Applica-
    tions (eds Gray, J.M., Ko, T., Zhang Shouhua, Wu Baorong and Xie Xishan)
    (Beijing, 1985) ASM (1985).


12. United States Steel Technical Report- Corrosion Performance of Mn-Cr-
    Cu-V Type USS Cor-Ten High Strength Low Alloy Steel in Various Atmo-
    spheres, February 1965, Project No. 47.001-001 (7) and 47.001-003 (3).