API 5L X60 pipeline steel is required to have high toughness

API 5L X60 pipeline steel is the steel grade specified by API 5L, its chemical composition is C ≤ 0.28, Mn ≤ 1.40. API 5L X60 pipeline steel has two levels: API 5L X60 PSL1 and API 5L X60 PSL2. For API 5L X60 PSL1 steel, the min. yield strength is 414 MPA, and the min. tensile strength is 547 MPA. For API 5L X60 PSL2 steel, the min. yield strength is 414 MPA, and the min. tensile strength is 565 MPA. API 5L X60 pipeline steel is equivalent to Chinese material L415.

API 5L X60 pipeline steel is mainly used in pipelines to transport oil and natural gas. The natural gas pipelines have especially high operating pressure, which requires high toughness of API 5L X60 pipeline steel. When the defect of high-pressure gas pipeline causes the leakage of high-pressure gas, and the ability of high-pressure gas expansion and release is greater than the energy required for fracture propagation, the defect will continue to expand. At present, drop weight tear test (DWTT) is used to evaluate the brittle fracture of pipeline steel in domestic and foreign steel mills.

In order to meet the requirements of tensile properties and fracture toughness of thick API 5L X60 pipeline steel, Nb, V, Ti and other alloy elements can be added as required.