Some Examples of Industrial Applications of Ultra-High Purity Steels

Abstract
In the last decade, the evolution and control of steelmaking practice have enabled drastic reductions to be made in the impurity content of low alloy steels (mainly S, P, O, N and H) and the resulting superclean steel products have seen their in-service behaviour greatly improved. The following examples concerning CLI products are presented : 1 - The reduction of S content by a factor of more than ten and the control of O content have considerably reduced the Hydrogen Induced Cracking (HIC) sensitivity of the C-Mn steel grades for the storage of oil and gas in sour environments. 2 - Superclean Ni Cr Mo V steel grades for turbine rotors shafts have a very low sensitivity to lower nose temper embrittlement. 3 - Thick (>100 mm) plates or forgings in Mn Ni Mo steel grade used for nuclear pressure vessels welded by the electron beam process offer high toughness in fused areas when S + P are reduced to less than 30 ppm. 4 - Steel grades very close to pure iron have been developed to improve the performance of magnetic circuits in large accelerators.