Non-magnetic drill collar is the use of a low carbon high chromium manganese alloy steel, it is the ratio of chemical composition after rigorous refining and achieve its mechanical properties by forging, has good low permeability, high strength mechanical properties, excellent resistance to intergranular corrosion cracking performance and excellent abrasion resistance. When the magnetic field intensity of 1 x 105/4 PI A/m, non-magnetic collar relative permeability is less than 1.010 R.

Non-magnetic drill collar bore along arbitrary 100mm apart from the strength of a magnetic field gradient is less than or equal to 0.05 mu T.

Since all magnetic measuring instruments are measuring the borehole's geomagnetic field in the direction of measuring the borehole, the measuring instrument must be a non magnetic environment. However, during the drilling process, drilling tools are usually magnetic and magnetic, which affect the magnetic measurement instruments, and can not get the correct data of borehole trajectory measurement. The non-magnetic drill collar can be applied to the non-magnetic environment, and has the characteristics of drill collar in drilling. A considerable number of non magnetic drill collar products have been included in the API standard in 1990. According to the samples of foreign products and products, China has formulated the SY/T 5145-86 "non magnetic drill collar" standard.

The interference magnetic field line on the magnetic drill collar has no influence on the location of the measuring instrument. Therefore, the magnetic drill collar creates a non-magnetic environment for the magnetic measurement instrument, and ensures that the data measured by the magnetic measurement instrument is the real earth magnetic field information.

The use of rolled or forged AISI4145H Cr - Mo bonded steel is made to effectively control the content of chemical components and trace elements. The drill collar (drillcollar) is at the bottom of the drill string and is the main component of the lower drill assembly. Its main features are large wall thickness (generally 38~53mm, equivalent to 4~6 times the thickness of the drill pipe), with greater gravity and stiffness.