drill collar:

Ф89 Ф105 Ф121 Ф146 Ф159 Ф165 Ф178 Ф203

It's  made from rolled or forged AISI4145H chrome-molybdenum steel. The content of chemical composition and microelement is controlled effectively throughout the whole process. According to its different figures and materials, it can be divides into three types:

 Type A (columnar): made from ordinary alloy steel, both inside and outside of the cross section of the pipe are cycloidal.

Type B (spiral): made from ordinary alloy steel, with a spiral chute on the outer surface of the pipe

 Type C (non-magnetic): made from stainless alloy-steel of low magnetic permeability, both inside and outside of the cross section of the pipe are rounded.

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