Superior Comprehensive Mechanical Properties of a Low-Carbon Medium Manganese Steel for Replacing AISI 4330 Steel in the Oil and Gas Industry

• Published in: Materials 2023-01, Vol.16 (2), p.490
• Main Authors: Sun, Xinjun, Liu, Gang, Liang, Xiaokai, Tong, Shuai
• Format: Article
• Language: English
• Subjects: Austenite; Carbon; Carbon 12; Carbon content; Cementite; Compact tension; Copper; Crack propagation; Ductility; Fatigue cracks; Fatigue failure; Fatigue strength; Fatigue tests; Fracture mechanics; Gas industry; Iron carbides; Low carbon steels; Low temperature; Low temperature resistance; Manganese steel; Manganese steels; Mechanical properties; Metal fatigue; Microstructure; Nickel chromium molybdenum steels; Scanning electron microscopy; Stress intensity factors; Temperature; Tempered martensite; Tensile strength; Tension tests; Yield stress
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16020490

A low-carbon medium manganese steel (0.12C-3.13Mn) containing Cr, Ni, Mo, V, and Cu elements was designed to replace the AISI 4330 steel applied in the oil and gas industry. The mechanical properties, microstructures, and fatigue crack growth rate were comparatively analyzed using uniaxial tension tests, microstructure characterization, and compact tension with fatigue crack growth characterization. The results showed that the ductility and -40 °C impact energy of 0.12C-3.13Mn steel were better than AISI 4330 steel (from 115 J to 179 J), while the yield strength of 957 MPa of the former was lower than the latter of 1060 MPa after being subjected to the same tempering process. The microstructure of 0.12C-3.13Mn steel was composed of a mixture of tempered martensite, reversed austenite, and nanosized precipitation particles, while the microstructure of S4330 steel contained ferrite and large-size Fe C with lath and near-spherical morphologies. Compared to Cr-rich Fe C, (V, Mo)C and Cu-rich particles have smaller sizes and, thus, provide more strengthening increment, leading to a higher yield ratio. The impressive fatigue-resistance property was obtained in 0.12C-3.13Mn steel because the threshold value was 5.23 MPa*m compared to the value of 4.88 MPa*m for S4330 steel. Even if the fatigue crack grew, the stress intensity factor range of 0.12C-3.13Mn steel was obviously wider than that of AISI 4330 steel due to the presence of reversed austenite and secondary cracks. Overall, the AISI 4330 steel could be replaced with the designed 0.12C-3.13Mn steel due to the similar strength and better ductility, low-temperature toughness, and fatigue-resistance property.