API 5L steel line pipe adopts different steel grades, generally are Gr.B, X42, X46, X52, X60, X70, X80. Some manufacturers are capable of manufacturing steel grade up to X100 and X120. As the steel line pipe grades higher, more strictly control on the carbon equivalent control, and higher mechanical strength performances.
More over, for the same grade API 5L pipe, seamless and welded chemical elements content is different, which welded pipe is required more strictly and lower on Carbon and Sulfur.
By different delivery condition, there are also As-rolled, normalizing rolled, thermomechanical rolled, normalizing formed, normalized, normalized and tempered, quenched and tempered.
For intermediate grades, API 5L pipe grade shall be in one of following description format:
1. The letter L followed by the specified minimum yield strength in Mpa. For example, L290 (X42) means the minimum yield strength is 290 Mpa. In case of PSL2 pipe, Suffix letter (R, N, Q or M) shall be added to describe the delivery condition;
2. The letter X follwed by a two or three digital number equal to the minimum yield strength in 1000 psi rounded down to the nearest integer and, for PSL2 pipe, the letter describing the delivery condition (R, N, Q, or M) consist with the above formats.