API 5D Drill Pipe Steels
General Description
The steel grade of oil drill pipe refers to the grade of drill pipe steel, which is determined by the yield strength of the drill pipe steel. API (American Petroleum Institute) divides drill pipe steel grades into five grades: D, E, 95(X), 105(G), 135(S). The higher the drill pipe steel grade, the greater the yield strength of the pipe, and the greater the various strengths of the drill pipe. In the strength design of the drill string, it is recommended to increase the strength of the drill string by increasing the steel grade, instead of increasing the thickness of the wall.