8 Appearance
8.1 Tubes shall have a smooth internal and external sur-
face consistent with the cold working process. As a result, the arithmetical
mean deviation of the profile, Ra, will be 6,3 цт or less. Lower Ra values shall
be subject to agree- ment for quality grade С tubes.
NOTE: For technical reasons, it is not always possible to obtain a smooth
surface on tubes with an internal diameter of less than
15 mm.
8.2 Slight surface imperfections such as scabs or gouges, resulting
from the manufacturing process, are per- mitted provided the inner and outer
diameters, after dress- ing, continue to meet the specified requirements. Scabs,
laps or laminations are not permitted.
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).
8.3 As a result of cold working, tubes that have not under- gone heat
treatment, i.e. tubes in the BK or BKW condition, are generally covered by a
lubricant or grease film on their inner and outer surfaces. An agreement shall
be made con- cerning its removal. Tubes that have undergone heat treatment,
i.e. tubes in the BKS, GBK or NBK condition, may show signs of scorching, but
shall be free of loose scale.
8.4 Where, with regard to subsequent surface treatment (such as galvanizing),
special requirements are to be met concerning the surface preparation grade
of tubes, such requirements shall be agreed upon at the time of ordering.
8.5 In compliance with commercial practice, the tubes shall be supplied
with provisional corrosion protection. If a particular form of corrosion protection
(e.g. galvanizing as specified in DIN 50960 Part 1), or none whatsoever, is
re- quested, this shall be stated in the order.
9 Dimensions and limit deviations
9.1 Diameter and wall thicknesses
DIN 2391 Part 1 shall apply for the dimensions of seamless precision steel
tubes.
If one of the limit deviations for the diameter is to be zero, the limit deviation
for the wall thickness shall be equal to 10% of the mean wall thickness calculated
using the for-mula given in clause 2 of DIN 2391 Part 1.
9.2 Straightnesss
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
1000 mm apart.
Tubes of 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 straight-ened. As establishing the straightness of
such tubes might prove to be difficult, the straightness measuring 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 be-tween 4 m and 7 m.
The number of tubes in lengths from 2 m to below 4 m shall not exceed 15% of
the quantity ordered and shall be sup-plied in separate bundles.
Cut lengths shall allow for deviations of + 500 mm of the length ordered, short
lengths of 2000mm or more being supplied in separate bundles up to a maximum
of 10% of the quantity ordered.
Exact lengths are subject to the following limit deviations:
- for lengths up to 500 mm: +20 mm;
- for lengths above 500 mm up to 2000 mm: +30 mm;
- for lengths above 2000 mm up to 5000 mm: +50 mm;
- for lengths above 5000 up to 7000 mm: +100 mm.
- For lengths greater than 7000 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
2391 Parti.
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 7.
Table 7: Excess supplies
Quantity ordered, in metres
|
Percentage deviation
|
Up to 500
|
+20
|
Above 500 up to 2 000
|
+15
|
Above 2 000
|
+10
|
10 Testing
10.1 Tubes to be supplied without inspection document (quality
grade A)
As part of internal control, the manufacturer shall submit tubes
to:
- a) a dimensional check;
- b) a surface inspection;
- c) a tensile test, as specified in DIN EN 10002 Part 1;
- d) a flattening test, as specified in DIN EN 10233;
- e) a drift expanding test, as specified in DIN EN 10234.
Flattening and drift expanding tests shall only be carried out on annealed
or normalized tubes made of the steel grades listed in table 2 if testing does
not adversely affect the tube diameter and wall thickness.
Subject to agreement, a type 2.2 inspection document in compliance with DIN
50049 shall be issued.
Additional tests shall be subject to agreement. They are relevant for quality
grade С steels.
10.2 Tubes to be supplied with inspection document
(quality grade C)
Should a DIN 50049 inspection certificate be required for quality grade С steel
tubes, this shall be agreed upon at the time of ordering. The order shall state
the type of document requested and the name the testing agency if the inspection
is carried out by a third party.
Tubes shall be tested at the manufacturer's works. Produc-tion shall not be
unduly disturbed if inspection is carried out by experts who are not employed
by the manufacturer.
10.2.1 Scope of testing
Tubes shall be tested by batches. For details, see table 9. For the purpose
of testing, tubes shall be divided according to steel grade, final supply condition
and size, into batches each comprising 200 units. Remainders of up to 20 units
may be distributed uniformly across the other batches, remainders ranging from
20 to 200 units and consignments of less than 200 units being considered a whole
batch.
10.2.2 Procedure
All tests shall be carried out at ambient temperature.
10.2.2.1 Tensile test
The tensile test shall be carried out as specified in DIN EN 10002 Parti.
10.2.2.2 Flattening test
The flattening test shall be carrried out, as specified in DIN EN 10233, on
annealed and normalized tubes, the wall thickness of which
is less than 15% of the outside diameter. The test pieces
or tube ends shall be flattened until a specified distance
between platens, H, is reached. This distance, in mm, is to
be calculated on the basis of the following equation:
where Т is the wall thickness, in mm; D is the outside diameter of the tube,
in mm; с is a constant, which is 0,09 for steel grades St 30 and St 35, and
0,07 for steel grades St 45 and St 52.
After testing, the samples shall be inspected for cracks.
Table 8: Percentage expansion
Steel grade
|
Final supply condition
|
Percentage expansion for a wall thickness, in mm, of
|
up to 4
|
above 4
|
St 30 Si
St 30 Al
St 35
St 45
St 52
|
Normalized or annealed
|
20
20
18
15
15
|
15
15
12
10
10
|
10.2.2.3 Drift expanding test
The drift expanding test shall be conducted until the maxi-mum
expansion specified in table 8 is reached. It shall be carried out, as described
in DIN EN 10 234, on annealed and normalized tubes with a maximum outside diameter
of 150 mm and a wall thickness of up to 9 mm.
After testing, the samples shall be inspected for cracks.
10.2.2.4 Measurement of surface roughness
The surface roughness shall be measured axially by using electric
stylus instruments as specified in DIN 4768.
10.2.2.5 Dimensional check
The tube dimensions shall be measured with suitable tech-niques.
The type and scope of the dimensional checking of tubes of exact length shall
be subject to agreement.
10.2.2.6 Surface inspection
The appearance of the outer and, if possible, inner tube surface
shall be examined visually under appropriate light-ing conditions by an inspector
having normal vision. If so agreed, another method of checking the appearance
may be used. The type and scope of surface inspection of tubes of exact length
shall be subject to agreement.
10.2.2.7 Leak tightness test
The tubes shall be tested for leak tightness by using appro-priate
non-destructive test methods (e.g. eddy current testing in accordance with Stahl-Eisen-Prufblatt
(Iron and steel testing specification) 1925*)).
10.2.2.8 Non-destructive testing
If freedom from imperfections is of particular significance, eddy
current testing as specified in PRP 02-74 may be car-ried out, primarily to
detect transverse defects. The ultra-sonic test, as specified in Stahl-Eisen-PrQfblatt
1915, is usually conducted to detect longitudinal defects.
10.2.3 Retests
10.2.3.1 Tubes not satisfying the requirements when tested
as specified in subclauses 10.2.2.1 to 10.2.2.3 shall be rejected. Two further
tubes shall be taken from the batch concerned in place of the rejected sample
tube and submit- ted for testing. If one of these two tubes does not fulfill
the requirements, the entire batch shall be considered not to comply with the
standard.
10.2.3.2 If the defects or deficiencies established can
be made good by means of heat treatment or other suitable measures, the supplier
shall be given the opportunity to present a batch which was rejected for renewed
accept- ance inspection. If the test pieces still fail to satisfy the requirements,
the entire batch shall be considered not to comply with the standard.
10.3 Inspection documents
The inspection documents to be issued shall comply with DIN 50049.
Table 9: Scope of testing
No.
|
Type of test or inspection
|
Cf. subclause
|
Scope of testing1)
|
Responsible for testing
|
1
|
Tensile test
|
10.2.2.1
|
One test piece, taken from one sample tube per batch.
|
Subject to agreement.
|
2
|
Flattening test
|
10.2.2.2
|
One test piece, taken at one end of sample tube specified
under item No.1.
|
Subject to agreement.
|
3
|
Drift expanding test
|
10.2.2.3
|
One test piece, taken at one end of sample tube specified
under item No.1.
|
Subject to agreement.
|
4
|
Measurement of surface roughness
|
10.2.2.4
|
If agreed upon, one test piece taken from one sample tube
specified under item No. 1 .
|
Manufacturer
|
5
|
Dimensional check
|
10.2.2.5
|
All tubes.
|
Subject to agreement.
|
6
|
Surface inspection
|
10.2.2.6
|
All tubes.
|
Subject to agreement.
|
7
|
Leak tightness test
|
10.2.2.7
|
If agreed, all tubes.
|
Manufacturer
|
8
|
Non-destructive test
|
10.2.2.8
|
If agreed, all tubes.
|
Manufacturer
|
1) Applies to random lengths and multiples
of cut and exact lengths.
|
11 Quality grade С
Table 10: Special requirements (examples)
Line
|
Special requirement
|
Features and/or technical delivery conditions
|
1
|
Steel grades other than specified in table 1.
|
As specified in DIN 1651, DIN EN 10025, DIN EN 10083 Parts
1 and 2, or DIN 17210.
|
2
|
Tubes for pipelines.
|
As specified in DIN 1629, DIN 1630, or DIN 2445 Part 2.
|
3
|
Other geometry and surface.
|
Tubes with an outside diameter smaller than 4 mm and greater
than 260 mm, with a non-circular cross section, subject to other tolerances
than those specified in DIN 2391 Part 1 , other tolerance positions or
special requirements regarding the surface condition, straightness and
squareness of pipe ends.
|
4
|
Final supply condition other than specified in table 4.
|
Tempered; annealed to obtain specific microstructure.
|
5
|
Other mechanical properties.
|
Deviations regarding the mechanical properties specified
in table 5.
|
12 Marking
A durable tag, containing the following information, shall be
securely attached to each bundle:
- a) the manufacturer's mark;
- b) the relevant standard (technical delivery condition) and quality grade;
- c) steel grade, in compliance with table 1;
- d) the final supply condition, in accordance with tale 4;
- e) the dimensions;
- f) the inspector's mark, where tubes are supplied with an inspection document.
Further markings shall be subject to agreement.
13 Bundling
The type of bundling shall be subject to agreement.
14 Complaints
Warranty claims may only be raised if based on the techni-cal
delivery conditions specified here or on any further agreement. The purchaser
shall give the supplier the opportunity of judging whether the complaint is
justified, by submitting the tube objected to and samples of the other tubes
supplied.
Standards and documents referred to
DIN 1629 - Seamless, circular, unalloyed steel pipes subject to
special requirements; technical delivery conditions
DIN 1630 - High performance seamless, circular, unalloyed steel
tubes; technical delivery conditions
DIN 1651 - Free cutting steel; technical delivery conditions
DIN 2391 Part 1 - Seamless precision steel tubes; dimensions
DIN 2445 Part 2 - Seamless precision steel tubes subject to fatigue
loading, rated for a pressure of 64 to 400 bar
DIN 4768 - Determination of surface roughness parameters Ra,
Rz, and Rmax, using electric stylus instruments; concepts
and measuring conditions
DIN 8528 Part 1 - Weldability of metallic materials; concepts
DIN 17121 - Seamless circular steel stubes for structural steelwork;
technical delivery conditions
DIN 17124 - Seamless circular fine grain steel tubes for structural
steelwork; technical delivery conditions
DIN 17172 - Steel pipes for conveying combustible liquids and
gases; technical delivery conditions
DIN 17173 - Seamless circular tubes made from steel with low temperature
toughness; technical delivery conditions
D|N 17175 - Seamless tubes with elevated temperature properties;
technical delivery conditions
D|N 17179 - Seamless circular fine grain steel tubes subject to
special requirements; technical delivery conditions
D|N 17204 - Seamless circular tubes made from steels for quenching
and tempering; technical delivery conditions
DIN 17210 - Case hardening steel; technical delivery conditions
DIN 17458 - Seamless circular austenitic stainless steel tubes
subject to special requirements; technical delivery conditions
DIN 50049 - Inspection documents for the delivery of metallic
products
DIN 50 960 Part 1 - Electroplated and chemically applied coatings;
designation and information in technical documentation
DIN EN 10 002 Part 1 - Tensile testing of metallic materials;
method of test at ambient temperature (including Amendment AC 1:1990)
DIN EN 10025 - Hot rolled unalloyed structural steel products;
technical delivery conditions (including Amendment A1:1993)
DIN EN 10027 Part 1 - Designation systems for steel; steel names
and principal symbols
DIN EN 10027 Part 2 - Designation systems for steel; numerical
system
DIN EN 10083 Part 1 - Quenched and tempered steels; technical
delivery conditions for special steels
DIN EN 10083 Part 2 - Quenched and tempered steels; technical
delivery conditions for unalloyed quality steels
DIN EN 10233 - Metallic materials; tube; flattening test
DIN EN 10234 - Metallic materials; tube; drift expanding test
Stahl-Eisen-Prufblatt 1915**) - Ultraschallprufung auf
Langsfehler von Rohren aus warmfesten Stahlen (Ultrasonic testing for stani
bisen ггито,ап > ,ongitudini?, imperfections in steel tubes with elevated temperature
properties)
Stahl-Eisen-Prufblatt 1925**) - Elektromagnetische Prufung
von Rohren zum Nachweis der Dichtheit (Eddy current testing of tubes for
leak tightness)
PRP 02-74*) - Prufblatt fur die Wirbelstromprufung von Prazisionsstahlrohren
(Specification regarding the
Other relevant standard
DIN EN 10021 - General technical delivery conditions for steel
and iron products eddy current testing of seamless precision steel tubes)
Previous editions
DIN 2391 Part 2:1940-06, 1957-11, 1967-07, 1981-07.
*) Obtainable from Fachvereinigung Prazisionsrohrwerke e.V. Postfach
300364, D-40403 Dusseldorf.
**) Obtainable from Vertag Stahlelsen mbH, Postfach 10 51 64, D-40042 Dusseldorf.
Amendments
In comparison with the July 1981 edition, this standard has been
revised in form and substance and the following amendments made:
- a) Quality grade В has been dropped and grades A and С redefined.
- b) The outside diameter, the inside diameter and the wall thickness have
been referred to as D, Dl and T, respectively, and
the order details changed accordingly.
- c) The use of SM steel and unkilled casted steel is no longer specified
for precision steel tubes.
- d) Grade С tubes may be made from other steels if these are suitable (cf.
table 1).
- e) In table 2 the maximum permissible P and S contents were brought into
line with the state of the art and the addition of further alloying elements
specified.
- f) A table covering permitted deviations of the product analysis from the
specified ladle analysis has been included (cf. table 3).
- g) The BKS 'cold formed and stress-relief annealed' condition has been included
and the descriptions provided for the other final supply conditions amended.
- h) Mechanical properties of tubes in the BKS condition have been specified
and the minimum values regarding the tensile strength for BK and BKW conditions
increased.
- i) The specifications for surface appearance have been completely revised.
- j) With regard to deviations from straightness, a distinction has been made
between localized deviations and deviations along the entire tube length.
- k) Random lengths have been limited to a range between 4 m and 7 m.
- I) The requirements for tube ends have been amended.
- m) Specifications regarding divergence between the quantity ordered and
the actual consignment now apply to orders for exact lengths only.
- n) Leak tightness tests are no longer specified for quality grade A tubes.
If delivery conditions require leak tightness, tubes shall be supplied in
quality grade C.
- o) A table covering the scope of testing has been included (cf. table 9).
- p) The requirements regarding the performance of test pipes submitted to
flattening and drift expanding tests have been amended.
- q) The procedures regarding surface roughness measurement, dimensional checks
and surface inspections, as well as leak tightness tests and non-destructive
testing have been altered.
International Patent Classification
F 16 L 009/02
G 01 В 021/30
G 01 N 033/20
|