drill collars Size Range: 3-1/8--11 Cylindrical, spiral,No thread galling, gluing and failure

Size Range    3-1/8——11

Brief Introduction

Hengshan drill collars are made of AISI 4145 H or 4145 H modified alloy steel. The chemical composition is controlled strictly during the refining and forging process. It can be divided into the following three types according to the appearance and material:                                                                                  

Type A(Cylindrical)   Be Made of alloy steel and the cross sections of the inside and outside pipe are both round.

Type B(Spiral)  Be Made of alloy steel and the outside pipe has spiral grooves.

Mechanical Properties

A type and B type drill collar

OD		Yield Strength MPa	Tensile Strength MPa	Elongation %	Brinell Hardness HB	Impact APV J
mm	in
79.4~171.4	31/8~63/4	≥758	≥965	≥13	285~341	≥54
177.8~279.4	7~11	≥689	≥930	≥13	285~341	≥54

C type drill collar 

OD		Yield Strength MPa	Tensile Strength MPa	Elongation %	Brinell Hardness HB	Impact APV J
mm	in
79.4~171.4	31/8~63/4	≥758	≥827	≥18
177.8~279.4	7~11	≥689	≥758	≥20

Usage     As an important part of drill stem, drill collar can supply the drilling pressure for the drill bit and increase the rigidity of drill stem.