Effect by Heat Treatment on DBTT of 20 Steel

Addressing the operation conditions for the 20 steel freezing pipes as used for coal mining industry, and using applicable standard for cryogenic pipes for reference, the tensile property and low temperature impact toughness of the as-hot rolled pipes and pipes as normalized variably are tested and analyzed, and the Origin software is used to fit the DBTT (ductile brittleness transformation temperature) curve. Result of the analysis reveals that after being normalized at 860 ℃, 880 ℃ and 910 ℃, the DBTT of the 20 steel drops to -30~-20 ℃, and the grain size of the normalized structure is more coarse than that of the as-hot rolled structure, whereas the post-normalization low temperature impact property of the steel is remarkably increased.