Welded and sized precision steel tubes

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:

• 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 - 40 x 1,5

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 - 40 x 1,5 X 4000

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 - 20 x 1,5 x 4000 - 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

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 10 233;
• e) a drift expanding test, as specified in DIN EN 10 234.

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 50 049 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 50 049 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 of the testing agency if the inspection is carried out by a third party.
Tubes shall be tested at the manufacturer's works. Production 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 8. 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 10 002 Part 1.

10.2.2.2 Flattening test

The flattening test shall be carried out, as specified in DIN EN 10 233, 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 34 and St 37, and 0,07 for steel grades St 44 and St 52. After testing, the samples shall be inspected for cracks.

10.2.2.3 Drift expanding test

Annealed and normalized tubes shall be submitted to the drift expanding test as described in DIN EN 10 234 until the maximurr expansion specified in table 7 is reached. After testing, the samples shall be inspected for cracks.

Table 7: Percentage expansion

Steel grade	Final supply condition	Percentage expansion for a wall thickness, in mm,
		up to 4	above 4
RSt 34-2 RSt 37-2 St 44-2 St 52-3	Normalized or annealed	20 18 15 15	15 12 10 10

10.2.2.4 Measurement of surface roughness

The surface roughness shall be measured axially outside the weld zone by using electric stylus instruments as specified in DIN 4768. 10.2.2.5 Dimensional check The tube dimensions Shalt be measured with suitable techniques. 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 lighting 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 appropriate non-destructive test methods (e.g. eddy current testing in accordance with Stahl-Eisen-Prilfblatt (Iron and steel testing specifications) 1925).

10.2.2.8 Non-destructive testing

If freedom from imperfections is of particular significance, ultrasonic testing as specified in Stahl-Eisen-Priifblatt 1917, should be carried out. If necessary, this test may be carried out along the weld.

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 submitted 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 acceptance 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 50 049.

Table 8: Scope of testing

Type of test or inspection			Scope of testing1)	Responsible for testing
No.		Cf. subclause
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 from one sample tube per batch.	Subject to agreement.
3	Drift expanding test	10.2.2.3	One test piece, taken from one sample tube per batch.	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 9: 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 1614 Parts 1 and 2, DIN 1623 Parts 2 and 3, or DIN 1624.
2	Tubes for pipelines.	As specified in DIN 1626, DIN 1628, or DIN 8964 Parts 1 and 2.
3	Other geometry and surface.	Tubes with an outside diameter smaller than 4 mm and greater than 159 mm, with a non-circular cross section, subject to other tolerances than those specified in DIN 2394 Part 1, other tolerance positions or special requirements regarding the surface conditions straightness and squareness of pipe ends.
4	Final supply condition other than specified in table 4.	Tempered
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 table 4;
• e) the dimensions;
• f) the inspector's mark, where tubes are supplied with an inspection document.

Further markings shall be the subject of agreement.

13 Bundling

The type of bundling shall be subject to agreement.

14 Complaints

Warranty claims may only be raised if they are based on the technical delivery conditions of this standard, or on any further agreement reached.
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 1614 Part 1 - Hot roiled mild unalloyed steel sheet and strip for cold reducing; technical delivery conditions

DIN 1614 Part 2 - Hot rolled mild unalloyed steel sheet and strip for cold forming; technical delivery conditions

DIN 1623 Part 2 - Cold reduced mild unalloyed steel sheet and strip for cold forming; technical delivery conditions

DIN 1623 Part 3 - Cold reduced mild unalloyed steel sheet and strip for vitreous enamelling; technical delivery conditions

DIN 1624 - Cold reduced mild unalloyed steel strip in widths not exceeding 650 mm; technical delivery conditions

DIN 1626 - Welded, circular, unaLgyed steel tubes subject to special requirements; technical delivery conditions

DIN 1628 - High performance welded, circular, unalloyed steel tubes; technical delivery conditions

DIN 2394 Part 1 - Welded and sized precision steel tubes; dimensions

DIN 4768 - Determination of surface roughness parameters R_a, R_a, and R_max, using electric stylus instruments; concepts and measuring conditions

DIN 8528 Part 1 - Weldability of metallic materials; concepts

DIN 8964 Part 1 - Elements of hermetic and semi-hermetic refrigeration systems; testing

DIN 8964 Part 2 - Elements of hermetic and semi-hermetic refrigeration systems; requirements

DIN 17 120 - Welded circular steel tubes for structural steelwork; technical delivery conditions

DIN 17 123 - Welded circular fine grain steel tubes for structural steelwork; technical delivery conditions

DIN 17 172 - Steel pipes for conveying combustible liquids and gases; technical delivery conditions

DIN 17 174 - Welded circular tubes made from steels with low temperature toughness; technical delivery conditions

DIN 17 177 - Electric pressure-welded steel tubes with elevated temperature properties; technical delivery conditions

DIN 17 178 - Welded circular fine grain steel tubes subject to special requirements; technical delivery conditions

DIN 17 457 - Welded circular austenitic stainless steel tubes subject to special requirements; technical delivery conditions

DIN 50 049 - Inspection documents for the delivery of metallic products

DIN 17 178 - Tensile testing of metallic materials; method of test at ambient temperature (including Amendment AC 1:1990)

DIN EN 10027 Part 1 - Designation systems for steels; steel names and principal symbols

DIN EN 10 027 Part 2 - Designation systems for steel; numerical system

DIN EN 10 233 - Metallic materials; tube; flattening test

DIN EN 10 234 Metallic materials; tube; drift expanding test

Stahl-Eisen-Priifblatt 1917*) - Zerstdrungsfreie Prutung elektrisch preBgeschweiBter Rohre aus terrltischen Stan/en (Non-destruc-tive testing of pressure welded ferritic steel pipes)

Stahl-Eisen-Prtlfblatt 1925*) - Elektromagnetische Priltung von Rohren гит Nachwels der Dichthett (Eddy current testing of tubes for leak tightness)

*) Obtainable from Vertag Stahleisen mbH, Postfach 10 51 64, D-40042 Dlisseldorf.

Other relevant standard

DIN EN 10 021 - General technical delivery conditions for steel and iron products

Previous editions

DIN 2394: 1938-07,1942-10, 1957-07;
DIN 2394-2 :1981-08.

Amendments

In comparison with the August 1981 edition, this standard has been revised in form and substance and the following amendments have been 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, D, 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 has been specified. Steel grades RSt 34-2, RSt 37-2 and St 44-2 may be killed by aluminium only.
• f) A table covering permitted deviations of the product analysis from the specified ladle analysis has been included (cf. table 3).
• g) The final supply conditions have partly been amended.
• h) The specifications for surface appearance have been completely revised.
• i) With reg'ard to deviations from straightness, a distinction has been made between localized deviations and deviation running along the entire tube length.
• k) The requirements for tube ends have been amended.
• l) Specifications regarding divergence between the quantity ordered and the actual consignment apply to orders for exact lengths only.
• m) 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.
• n) A table covering the scope of testing has been included (cf. table 8).
• o) The requirements regarding the performance of test pipes submitted to flattening and drift expanding tests have been amended.
• p) The procedures regarding the measurement of surface roughness, dimensional checks and surface inspections, as well as leak tightness tests and non-destructive testing have been altered.

International Patent Classification

В 21 С 037/06
F 16 L 009/02
G 01 В 021/30
G 01 N 033/20