Heavy weight drill pipes are manufactured from AISI 4142H-4145H modified drill collar material according to SY/T 5146-1997, thick-walled pipe called integral heavy weight drill pipe was developed to provide a gradual transition from the heavy weight drill collars to the relatively light weight drill pipe. This intermediate weight pipe has a wall thickness of approximately, and it helps prevent stress concentration at the top of the drill collars. It also reduce torque and differential pressure sticking. It is intended primarily for directional drilling. Because it bends easily, it simplifies directional control and  minimizes connection fatigue problems common to high angle or horizontal drilling. The reduced number of pipe failures and increased drill stem service also make it appropriate for some straight hole applications.