Microstructure and Mechanical Properties of Nb-API X70 Low Carbon Steel

The oil and gas production has grown steadily, the care with its transportation grid needs to be maintained expanded. pipeline used in transport of by-product requires materials high mechanical strength, toughness, fatigue resistance. chemical composition distribution, amount, morphology final microconstituents steel are paramount importance once it will directly influence properties. fracture toughness is one most important properties for suitability usage, literature pipelines study does not present tests such as crack tip opening displacement (CTOD), a steady controlled growth behavior, evaluate toughness. This compares API 5L X70 between two plates different Nb content, 0.06 0.09 wt.% by CTOD tests. response was correlated grain size distribution. parameter assess at 25 °C ? 60 °C. microstructures were similar. matrices composed ferrite, bands secondary products, including degenerated pearlite. Results showed prone formation bimodal microstructure, coarse fine grains, due addition Nb. High-Nb presented better than normal-Nb low-temperature.