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DNV EH32 offshore platform steel plate composition

The difficulty in the development of DNV EH32 offshore platform steel plate is not only the high toughness, excellent aging, good weldability and lamellar tearing resistance, but also the uniformity of all performance indexes of the whole steel plate head, middle tail and transverse and longitudinal.

When Nb, V, Ti, Cu, Ni microalloys are added to DNV EH32 offshore platform steel plate, Nb can produce significant grain refinement and medium precipitation strengthening, and the strong effect of grain refinement is related to the recrystallization of Nb (CN) precipitation delayed austenite during rolling. V is the strengthening element in steel. Due to the precipitation strengthening of VC, V (CN), the strength of DNV EH32 offshore platform steel plate can be significantly improved. V can improve the ductile brittle transition temperature, and its content is generally controlled below 0.10%. The effect of V on grain refinement is not as good as that of Nb in controlled rolling, but its precipitation strengthening effect is significant, which is stronger than that of Nb. Therefore, adding V to the steel requiring higher strength can have a good effect. Ti can produce strong precipitation strengthening effect, so that the strength of DNV EH32 offshore platform steel plate can be improved, and it can also prevent austenite recrystallization. The content of Ti is generally controlled below 0.02%. It can produce grain refining effect and improve the yield strength of DNV EH32 offshore platform steel plate, but it has little contribution to toughness. Cu not only has no effect on the hardness and toughness of the HAZ, but also can improve the strength of the base metal and the toughness at low temperature, especially the corrosion resistance. Ni can effectively improve the low-temperature toughness of DNV EH32 offshore platform steel plate. With the increase of Ni content in the steel, the transition temperature of toughness and brittleness is significantly reduced, and the low-temperature toughness is significantly improved.

Reduce the content of phosphorus and sulfur, and improve the plastic toughness of DNV EH32 offshore platform steel plate. Phosphorus content mainly affects the plasticity of steel. Sulfur is a free cutting element. After the formation of manganese sulfide in steel, especially in low temperature rolling, the anisotropy of steel increases with the rolling direction, which is unfavorable to the transverse impact toughness and plasticity, and even to the delamination of steel plate.

Good weldability is very important for DNV EH32 offshore platform steel plate. In order to ensure its good weldability, carbon equivalent should be strictly controlled. Among them, reducing carbon content has the most significant effect on controlling carbon equivalent, and reducing carbon content can also effectively improve low-temperature impact toughness.