drill collar

The drill collar is according to SY/T5144-1997 and API 7-1 " Specification for Rotary Drill Stem Elements" standard, the material uses AISI 4145H alloy structural steel to carry on the deep hole processing, before thread and spiral groove processing against the total cross-section to quenching and the tempering heat treatment. After thread examination qualified, and carries on cold rolling processing to the thread root and the slips, reduces the thread part fatigue failure to increase the drill collar service life.