4.3 Magnetic properties
4.3.1 Measurements of relative magnetic permeability
Drill collars shall have a relative magnetic permeability less than 1,010. Each certification of relative magnetic permeability shall identify the test method. The manufacturer shall also state whether tests have been performed on individual collars or on a sample that qualifies a product lot. One lot is defined as all material with the same form from the same heat processed at one time through all steps of manufacture.
4.3.2 Field gradient measurement
The magnetic field in the bore of new drill collars shall exhibit deviation from a uniform magnetic field not exceeding士0,05 μT. This shall be measured with a magnetoscope and differential field probe having its magnetometers oriented in the axial direction of the collar. A strip-chart record showing differential field along the entire bore of the collar shall be part of the certification of each collar.
5. Corrosion resistance requirements (for austenitic steel collars of 12 % chromium or more)
Austenitic stainless-steel collars are subject to cracking due to the joint action of tensile stress and certain specific corrosive agents. This phenomenon is called stress-corrosion cracking.
Resistance to intergranular corrosion shall be demonstrated by subjecting material from each collar to the corrosion test specified in ASTM A 262 Practice E. At the discretion of each supplier, the test specimen may have an axial orientation, in which case it shall be taken from within 12,7 mm (0.5 in) of the bore surface, or it may have a tangential orientation, in which case its midpoint shall be within 12,7 mm (0.5 in) of the bore surface.
Under some environmental circumstances, steels may be subject to transgranular stress-corrosion cracking. Tendencies vary with different compositions, but additional resistance may be provided by surface treatments that lead to compressive residual stress.
6. Marking
Non-magnetic drill collars conforming to this part of ISO 10424 shall be die-stamped with the following information:
a) the manufacturerʼs name or identifying mark;
b) outside diameter;
c) bore;
d) non-magnetic identification (non-magnetic drill collar NMDC);
e) connection designation;
f) "ISO 10424-1".
NOTE The drill collar number consists of two parts separated by a hyphen. The first part is the connection number in the NC style. The second part, consisting of 2 (or 3) digits, indicates the drill collar outside diameter in units and tenths of inches, drill collars with 209.6 mm, 241,3 mm and 279,4 mm outside diameters are shown with 6 5/8, 7 5/8 and 8 5/8 REG connections, since there are no NC connections in the recommended range of bending-strength ratios.
The example below illustrates these marking requirements. Locations of the markings and the application of additional markings shall be specified by the manufacturer.
EXAMPLE A 209,6 mm (8 1/4 in) collar, with 71,4 mm (2 13/16 in) bore, manufactured by A B Company, shall be stamped:
AB Co. (or mark) 209,6 71,4 NMDC 6 5/8 REG ISO 10424-1
