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September 1994

DIN 2394 Part 2

Welded and sized precision steel tubes
Technical delivery conditions

ICS 23.040.10

Supersedes August 1981 edition.

Descriptors: Tube, steel tube, precision tube, technical delivery conditions.

GeschweiBte maBgewalzte Prazisionsstahlrohre; technische Lieferbedingungen

In keeping with current practice in standards published by the International Organization for Standardization (ISO), a comma has been used throughout as the decimal marker.

Dimensions in mm

1 Scope and field of application

1.1 This standard specifies technical delivery conditions for welded and sized precision steel tubes of the dimensions listed in DIN 2394 Part 1, which are made from the steel grades listed in clause 4.
Such tubes are mainly used where accuracy to size and, possibly, a small wall thickness, a particular surface condition and specific mechanical properties are required.

1.2 This standard does not cover:

  • welded, circular, unalloyed steel tubes subject to special requirements (cf. DIN 1626);
  • high performance welded, circular, unalloyed steel tubes (cf. DIN 1628);
  • welded circular steel tubes for structural steelwork (cf. DIN 17 120);
  • welded circular fine grain steel tubes for structural steelwork (cf. DIN 17123);
  • welded circular tubes made from steels with low temperature toughness (cf. DIN 17174);
  • electric pressure-welded steel tubes with elevated temperature properties (cf. DIN 17177);
  • welded circular fine grain steel tubes subject to special requirements (cf. DIN 17 178);
  • welded circular austenitic stainless steel tubes subject to special requirements (cf. DIN 17 457);
  • teel pipes for conveying combustible liquids and gases (cf. DIN 17172).

Subject to agreement, tubes of dimensions specified, in DIN 2394 Part 1 and in compliance with one of the standards listed above may be ordered in quality grade C.

2 Quality grades

Tubes shall be supplied in the following quality grades: for precision steel tubes, that do not require an inspection certificate and thus are not subject to special requirements, grade A;
for precision steel tubes subject to special requirements, grade C.
In accordance with the stated demands of the purchaser, such special requirements and the relevant test methods shall be subject of agreement. Table 9 lists possible additional requirements (for grade C).

3 Order details and options

The following information shall be supplied by the purchaser:

  • a) the quantity, in metres;
  • b) a reference to this standard;
  • c) the quality grade;
  • d) the steel grade;
  • e) the final supply condition;
  • f) the outside and wall thickness;
  • g) the type of tube length to be supplied;
  • h) any inspection document agreed upon.

Designation for 1 000 m welded precision steel tubes, made of RSt 37-2 steel, welded and sized (BKM), with an outside diameter, D, of 40 mm and a wall thickness, T, of 1,5 mm, in random lengths:

1000 m tube DIN 2394 — RSt 37-2 BKM — 40x1,5

Designation for 1 000 m quality grade С welded precision steel tubes, made of RSt 37-2 steel, normalized (NBK), with an out-side diameter, D, of 40 mm and a wall thickness, T, of 1,5 mm, in exact lengths of 4 000 mm, where the interior burr has been removed by cutting (IG):

1000 m tube DIN 2394 — С — IG — RSt 37-2 NBK — 40x1,5x4000

Designation for 1 000 rn quality grade С welded precision steel tubes, made of St 37.8 steel, normalized (NBK), with an outside diameter, D, of 20 mm and wall thickness, T, of 1,5 mm, in exact lengths of 4 000 mm, produced to the limit deviations specified in DIN 2394 Part 1, complying with the technical delivery conditions specified in DIN 17177 and supplied with type 3.1.В inspec-tion certificate as specified in DIN 50 049:

1000 m tube DIN 2394 — С — 20x1,5x4000 — DIN 17177 — St 37.8 NBK — 3.1.B

Unless otherwise specified, tubes shall be supplied in quality grade A and in lengths as specified in subclause 9.3.

4 Materials

The tubes shall be manufactured from electric steel or basic oxygen steel, the melting and casting processes being at the discretion of the manufacturer.
The steel shall be cast as killed steel. If a particular deoxidation procedure is requested, this shall be agreed upon at the time of ordering. Table 1 lists relevant steel grades.

Table 1: Steel grades

Quality grade
Steel grade
Previous designation used in Germany
as in DIN EN 10027-1
as in DIN EN 10027-2
A
S205G2T
S235JRG2
S275JR
S355J2G3
1.0034
1.0038
1.0044
1.0570
RSt 34-2
RSt 37-2
St 44-2
St 52-3
C
All grades as for quality grade A, and any other steel grades.

5 Chemical composition

5.1 Ladle analysis

The chemical composition of the steels dealt with in this standard shall be as specified in table 2. Small departures from these specifications are permissible if they do not impair the performance of the steel.

5.2 Product analysis

When a product analysis is carried out on finished tubes, the permitted deviations given in table 3 shall apply to the ladle analysis specified in table 2.

Table 2: Chemical composition of steel grades shown on ladle analysis

Steel grade
Chemical composition, as a percentage by mass
Symbol
Material number
С
max.
Si
max.
Mn
max.
P
max.
S
max.
Al
RSt 34-2
1.0034
0,15
0,30
0,60
0,025
0,025
1)
RSt 37-2
1.0038
0,17
0,30
0,70
0,025
0,025
1)
St 44-2
1.0044
0,21
0,30
1,10
0,025
0,025
1)
St 52-3
1.0570
0,22
0,35
1,60
0,025
0,025
=>0.020
The following alloying elements may be added:
Nb: <= 0,03 %; Ti: <= 0,03 %; V: <= 0,05%; Nb + Ti + V: <= 0,05 %.
1) This steel grade may be killed by aluminium only (aluminium content 0,020% or more).

Table 3: Permitted deviations of the product analysis from the specified ladle analysis

Element
Permitted deviations from the specified limits of the ladle analysis, as a percentage by mass
C
+0.02
Si
+0.03
Mn
+0.06
P
+0.005
S
+0.005
Nb
+0.01
Ti
+0.01
V
+0.01

6 Final supply conditions

Tubes are to be supplied in one of the final supply conditions specified in table 4.

Table 4: Final supply conditions

Designation
Symbol
Description
Welded and sized
BKM
Tubes do not undergo heat treatment following welding and sizing and thus have a rather high resistance to deformation.
Annealed
GBK
Sizing is followed by annealing in a controlled atmosphere.
Normalized
NBK
Sizing is followed by annealing above the upper transformation point in a controlled atmosphere.

7 Mechanical properties

7.1 The mechanical properties are a function of the final supply condition (cf. table 4) and shall comply with table 4.

7.2 When tested as described in subclauses 10.2.2.2 and 10.2.2.3 tubes shall show no cracks.

7.3 In the case of steel grades and/or final supply conditions other than those specified in tables 2 and 4, the required mechanical properties shall be subject to agreement. Such tubes shall be supplied in quality grade C.

7.4 On the basis of their chemical composition and the way they have been processed, the steels listed in table 2 are to be regarded as weldable. It should, however, be noted that, due to subsequent welding, the mechanical properties of tubes in the BKM condition are modified in the area of the tube which has been subjected to heat.

Table 5: Mechanical properties of tubes at ambient temperature

Final supply condition
Welded and sized (BKM)1)
Annealed (GBK)1)
Steel grade
Material designation
Material number
Minimum tensile strength, Rm, in N/mm2 Minimum elongation at fracture, A5, as a percentage Minimum tensile strength, Rm, in N/mm2 Minimum elongation at fracture, A5, as a percentage
RSt 34-2
1.0034
330
8
300
28
RSt 37-2
1.0038
390
7
315
25
St 44-2
1.0044
440
6
390
21
St 52-3
1.0570
540
5
490
22

Final supply condition
Normalized (NBK)
Steel grade
Material designation
Material number
Tensile strength, Rm, in N/mm2 Tensile strength, ReH2), in N/mm2 Minimum elongation at fracture, A5, as a percentage
RSt 34-2
1.0034
310 to 410
205
28
RSt 37-2
1.0038
340 to 470
235
25
St 44-2
1.0044
410 to 540
255
21
St 52-3
1.0570
490 to 630
355
22

1) The yield strength for the annealed (GBK) condition shall be equal to at least 50 % of the tensile strength. Depending on the extent of deformation, the yield strength of tubes delivered in the (BKM) condition may come close to reaching the tensile strength. Calculations should be based on a minimum value of 70 % of the tensile strength.
2) For tubes with an outside diameter up to 30 mm and a wall thickness up to 3 mm, the minimum yield strength may be 10 N/mm2 lower.

8 Appearance

8.1 Tubes shall have a smooth internal and external surface consistent with the sizing process. Except for the weld zone, the arithmetical mean deviation of the profile, R,, will be 6,3 um or less. If particular significance is given to the surface appearance, tubes may be made from cold-rolled steel strip. This shall be subject of agreement at the time of ordering and shall apply for quality grade С tubes.

8.2 The exterior weld flash shall be removed. For tubes with a wall thickness, 7, of up to 1,5 mm, the interior weld flash shall not exceed 0,8 mm in height and not be higher than 0.6 Г for tubes with a wall thickness greater than 1,5 mm. Where, subject to agreement, the interior flash is to be dressed by machining (this being indicated by the symbol IG in the order designation), the residual flash shall not be higher than 0,3 mm and the remaining wall thickness no less than the minimum value specified in this standard.

8.3 Slight surface imperfections such as scabs or gouges, resulting from the manufacturing process, are permitted provided the inner and outer diameters, after dressing, continue to meet the specified requirements. If freedom from imperfections is of particular significance, an appropriate non-destructive test method (such as eddy current or ultrasonic testing) shall be agreed (cf. subclause 10.2.2.8).

8.4 Tubes in the BKM condition that have not undergone heat treatment are generally covered by a lubricant or grease film on their inner and outer surfaces. Agreement shall be reached concerning its removal. Tubes that have undergone heat treatment, i. e. tubes in the GBK or NBK condition, may show signs of scorching, but shall be free of loose scale.

8.5 Whe're, with regard to subsequent surface treatment (such as galvanizing), special requirements are to be met concern- ing the surface preparation grade of tubes, such requirements shall be agreed upon at the time of ordering.

8.6 In compliance with commercial practice, the tubes shall be supplied with provisional corrosion protection. If a particular form of corrosion protection, or none whatsoever, is requested, this shall be stated in the order.

9 Dimensions and limit deviations

9.1 Diameter and wall thicknesses

DIN 2394 Part 1 shall apply for the dimensions of welded and sized precision steel tubes.

9.2 Stralghtness

Tubes with an outside diameter exceeding 15 mm shall not deviate from straightness by more than 0,25 % of the total length. Tubes with a yield strength greater than 500 N/mm2 shall not deviate from straightness by more than 0,3 % of the total length. Localized deviations shall not exceed 3 mm/m and shall be measured as the distance between the tube surface and a chord linking two random points 1 000 mm apart.
Tubesof exact lengths shall not deviate from straightness by more than 0,3 % of the tube length.
In compliance with commercial practice, tubes with an outside diameter of up to 15 mm shall be supplied straightened. As establishing the straightness of such tubes might prove to be difficult, the straightness testing procedure shall be subject to agreement.
More stringent requirements regarding straightness shall be subject to agreement and shall apply for quality grade С tubes.

9.3 Lengths

Unless otherwise specified by the purchaser at the time of ordering, tubes shall be supplied as random lengths between 5 m and 7 m.
The number of tubes in lengths from 2 m to below 5 m hall not exceed 10 % of the quantity ordered and shall be supplied in separate bundles.
Cut lengths shall allow for deviations of +/- 500 mm of the length ordered, short lengths of 2 000 mm or more being supplied in separate bundles up to a maximum of 10 % of the quantity ordered. Exact lengths comply with the following limit deviations:

for lengths up to 500 mm: +20 mm;
for lengths above 500 mm up to 2 000 mm: +30 mm;
for lengths above 2 000 mm up to 5 000 mm: +50 mm;
for lengths above 5 000 mm up to 7 000 mm: +100 mm.
For lengths greater than 7 000 mm, limit deviations shall be subject to agreement.

9.4 Tube ends

Tube ends shall be cut nominally square to the tube axis and shall be free from excessive burrs, as may result from the cutting process. Such burrs may cause a change in diameter, exceeding the limit deviations specified in DIN 2394 Part 1.
Agreement regarding the finishing of ends of tubes of exact length is mandatory.

9.5 Divergence between quantity ordered and consignment

Where tubes of exact length have been ordered, deficient supplies shall not be permitted. However, excess supplies shall be permissible in compliance with the specifications given in table 6.

Table 6: Excess supplies

Quantity ordered, in metres
Percentage deviation
Up to 500
+ 20
Above 500 up to 2 000
+ 15
Above 2 000
+ 10

Measurement of surface roughness

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