Raw materials:
A drill collar is made of structure steel alloy forged or rolled from AISI 4145H.
Processing and thermal treatment of deep-holes：
The
drill collar is processed and made as per Standard API SPEC 7. Thermal
treatment is conducted over the whole length of the products to ensure
that its mechanic performance can meet the provisions under the Standard
API SPEC 7. Its Brinell hardness ranges between 285 and 341. And impact
energy of its Charpy V-shaped notch can be 40 ft-lb at a temperature of
20oC±5oC 1 inch below the surface of the pipe.
Traceability:
During the entire process of the
making of a drill collar, complete data from performance tests for the
processing of each part including roughcast, thermal treatment and
connecting thread will be kept for reference. A separate number will be
affixed to each single part.
Required testing procedures:
All the drill collars
will be tested according to the API Standard. Testing of surface
dimensions and ultrasonic wave and magnetic particle testing over the
whole length of a product will be included.
Cold forming of thread bases：
Cold rolling must be
done for the bolt root and elevator recess of a drill collar. Thus, the
bearing capacity of the upper radius will be increased via reducing
crack diffusion to increase fatigue strength of a drill collar and
extend the service life.
Phosphating or brass plating:
Phosphating or brass
plating will be conducted for all screw threads to increase their
corrosion resistance and avoid thread jamming of drilling tools.
Dimensions for slip, elevator groove and elevator through-holes of the drill collar (API RP 7G)
Our
company may, as per users’ requirements, process slips and elevator
grooves on drill collars. Hoisting joints and safety grips are not
required for the grooves to ensure safety during operations. The
dimensions and shapes of the slips and elevator grooves all comply with
the provisions under the Code API RP 7G.
Screw thread protector:Our company may, as per
users’ requirements, provide steel or plastic-steel ring thread
protectors (thread protector) for our products.