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The hydrogen embrittlement susceptibility of high strength TRIP/TWIP steels with the tensile strength of 600 Mpa to 900 Mpa grade was investigated using cathodically hydrogen charged specimens. TWIP steels with full austenite structure show a lower hydrogen content than do TRIP steels. The uniform distribution of strong traps throughout the matrix in the form of austenite is considered beneficial to reduce the hydrogen embrittlement susceptibility of TWIP steels. Moreover, an austenite structure with very fine deformation twins formed during straining could also improve the ductility and reduce notch sensitivity. In Ubend and deep drawing cup tests, TWIP steels show a good resistance to hydrogen embrittlement compared with TRIP steels.Key words hydrogen embrittlement, TRIP steel, TWIP steel, mechanical property. 서 론

The texture and microstructure in Cu/Nb added ultra low carbon steels through the different thickness layer were studied after hot rolling. It was found that the two ultra low carbon steels all show the inhomogeneity of hot rolling texture and the Cu-added ultra low carbon steel was far more inhomogeneous than Nb-added one. In the center layer, the strong α fibre, γ fibre textures and the shear textures including {001}<110>, {111}<112> were founded. Near the surface, the α fibre texture and the orientation texture caused by a typical plane-strain deformation condition of bcc metals were observed.

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