Non-magnetic drill collar are made of a kind of low-carbon high chrome-manganese alloy steel. They will achieve their mechanical performance via refining and forging on the basis of strict chemical constituent proportioning with outstanding low permeability, high level of mechanical performance, outstanding resistance to inter-granular corrosion and cracking, and strong wearability.  

When the magnetic intensity is   A/m, the relative permeability of the non-magnetic drill collar is  1.010.  
Magnetic induction intensity of the non-magnetic drill within any 100mm space between the internal holes of non-magnetic drill collar.