PRECISION COLD DRAWN SEAMLESS STEEL TUBE

Dimensions
The dimensions of precision tubes are given in the tables 1–6.
Tubes shall be ordered:
1. by outside diameter and inside diameter
2. by outside diameter and wall thickness
3. by inside diameter and wall thickness
Tolerances
1. Values according to standards
• outside and inside diameter - see tables in standards (for outside
diameter < 0,5% D) – for delivery conditions BK and BKW
• tolerances for tubes in delivery conditions BKS, GBK, NBK are
higher in dependence on wall thickness rate (1–2 x)
• out of roundness is included in the tolerances of diameter
• tolerances of the wall thickness is ±10%
• eccentricity is included in the tolerances of wall thickness
2. Tubes with small tolerances – see Table No. 2
3. Tolerances by agreement
4. Dimensions and tolerances according to standard ASTM A450
(Tubes) – Table 3 and 4 – basis for values is created:
a) wall thickenss in BWG
b) tube weight depends on wall thickness tolerances – tube weight
values shown in the table are applied for average wall thickness
(±10%). Tube weight is calculated according to formula. Tube
weight for minimum wall thickness (–0 +20%) = formula x 1,1
c) tube weight is given in lb/ft (Table3) or kg/m (Table 4)
Lengths
Kinds of lengths (current deliveries):
• production 3–7 (9) m
• fixed ±500 mm
• precise – tolerances –0 + x mm (x = by agreement)
– max. length = 15,4 m
– conversion: 1 m = 3,2808 ft
1 ft = 0,3048 m
Straightness
ReH 500 MPa – max. 0,0020 L (2 : 1000)
Steel grades
Steel is produced in electric arc furnace and is fully killed. Steel grades
are shown in the survey table of standards and in the table of chemical
composition and mechanical properties (values are informative
only).
Delivery conditions and heat treatment
BK (+C) Cold finished/hard (cold finished as drawn). No heat
treatment after the last cold forming process
BKW (+LC) Cold finished/soft (lightly cold worked). After the last
heat treatment there is a light finishing pass (cold drawing).
BKS (+SR) Cold finished/stress relieve annealed. After the final
cold forming process the tubes are stress relieve annealed.
GBK (+A) Annealed. After the final cold forming process the tubes
are annealed in a controlled atmosphere.
NBK (+N) Normalized. After the final cold forming process the tubes
are annealed above the upper transformation point in
a controlled atmosphere.
Additional requirements – Value of C-equivalent:
Ceq = C + Mn/6 + (Cr+Mo+V)/5 + (Ni + Cu)/15
Surface condition
Tube surface corresponds to the standards and depends on the method
of tube manufacturing and method of heat treatment.
Value of raughness Ra