DIN 2391-81 Part 2 Seamless Precision steel tubes

DIN 2391-81 Part 2 defines the technical delivery conditions for seamless precision steel tubes according to DIN 2391 Part 1 which are made from the steel grades listed in section 5.
Field of application Chemical Composition Mechanical Properties Welded Steel Tubing Quality grade JIS Number...

This Standard defines the technical delivery conditions for seamless precision steel tubes according to DIN 2391 Part 1 which are made from the steel grades listed in section 5.

Tubes according to this Standard are mainly used where accuracy to dimension and, possibly, small wall thicknesses and good surface condition are required.

Chemical composition(%)
Grade

Mfg. Process

Chemical composition(%)

C
Si
Mn
P
S
Ni
Cr
Mo
Others
St30Si
S
0.10Max
0.30Max
0.55Max
0.040Max
0.040Max
-
-
-
-
St30A1
S
0.10Max
0.05Max
0.55Max
0.040Max
0.040Max
-
-
-
Al deoxydized
St35
S
0.17Max
0.35Max
0.40Max
0.050Max
0.050Max
-
-
-
-
St45
S
0.21Max
0.35Max
0.40Max
0.050Max
0.050Max
-
-
-
-
St52
S
0.22Max
0.55Max
1.60Max
0.050Max
0.050Max
-
-
-
-

Note: ①Cold-finished/hard ②Cold-finished/soft ③Annealed ④Normalized
Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)

Mechanical Properties(Mpa)
Grade

Material
number

Tensile Test MPa or N/mm2

Remaks
(Similar to JIS)

Possibility Temperature

Min Yield point

Tensile Strength

St30Si
1.0211
-
400Min
(STKM11)
-
355Min
-
285Min
215
295~420
St30Al
1.0212
-
400Min
(STKM11)
-
355Min
-
285Min
215
295~420
St35
1.0308
-
440Min
(STC38)
-
370Min
-
315Min
235
340~470
St45
1.0408
-
540Min
(STKM13)
-
470Min
-
390Min
255
440~570
St52
1.0580
-
590Min
(STKM19)
-
540Min
-
490Min
350
490~630

Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)

Welded Steel Tubing and pipe-Corresponding to DIN 2391-1
Wall thickness
s
Nominal dimension 0.5 0.8 1 1.2 1.5 1.8 2 2.2 2.5 2.8 3 4.5 5 5.5 6 7 8 9 10 12 14 16 18 20 22 25
Permissible deviation
Outside diameter da                                                    
Nominal dimension Permissible deviation                                                    
4 ±0.1

 

                                                 
5                                                    
6                                                    
7                                                    
8                                                    
9                                                    
10                                                    
12 ±0.08                                                    
14                                                    
15                                                    
16                                                    
18                                                    
20                                                    
22                                                    
25                                                    
26                                                    
28                                                    
30                                                    
32 ±0.15                                                    
35                                                    
38                                                    
40                                                    
42 ±0.20                                                    
45                                                    
48                                                    
50                                                    
55 ±0.25                                                    
60                                                    
65 ±0.30                                                    
70                                                    
75 ±0.35                                                    
80                                                    
85 ±0.40                                                    
90                                                    
95 ±0.45                                                    
100                                                    
110 ±0.50                                                    
120                                                    
130 ±0.70                                                    
140                                                    
150 ±0.80                                                    
160                                                    
170 ±0.90                                                    
180                                                    
190 ±1.0                                                    
200                                                    
220 ±1.20                                                    
240                                                    
260 ±1.30                                                    

1) For outside diameters of nominal dimensions 4 and 5 mm, the permissible deviation from the nominal dimension s of the wall thickness is ± 20 % For outside diameters of nominal dimensions 6 to 8 mm, the permissible deviation from the nominal dimension s of the wall thickness is ±15%.
 
  s/D
=1/60
  s/D
=1/40
   s/D
=1/20

Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)

Quality grade
The tubes are supplied in the following quality grades :
Grade Description
A
precision steel tubes intended primarily for mechanical stressing, without any particular quality requirement and without acceptance test certificate
B
precision steel tubes intended primarily for mechanical stressing, with special quirement and exclusively with acceptance test certificate
C
precision steel tubes with special requirement according to section 12. Theses requirements and corresponding tests must be agreed, with the customer having to specify his requirements at the time of enquiry and on ordering

Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)


Table 1. Steel grades

Quality grade
Steel grade
Code number
Material number
A and B
St 30 Si
St 30 Al
St 35
St 45
St 52
1.0211
1.0212
1.0308
1.0408
1.0580
C
All steel grades according to quality grade A and B, as well as other steels, e.g. according to
DIN 1651
DIN 17 100
DIN 17 200
DIN 17 210
DIN 17 211
DIN 17 212
Condition on delivery
The tubes are supplied in one of the conditions listed in table 3. Other conditions on delivery are specified in table 9 (quality grade C).
Table 3. Conditions on delivery
Term
Symbol
Explanation
Cold-finished/hard
(cold-finished as-drawn)
BK
No heat treatment after the last cold-forming process. The tubes therefore have only low deformability.
Cold-finished/soft
(lightly cold-worked)
BKW
After the last heat treatment there is a light finishing pass (cold drawing) With proper subsequent processing, the tube can be cold-formed (e.g. bent, expanded) within certain limits.
Annealed
GBK
After the final cold-forming process the tubes are annealed in a controlled atmosphere or under vacuum.
Normalized
NBK
The tubes are annealed above the upper transformation point in a controlled atmosphere or under vacuum.

Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)

Mechanical and technological properties

8.1. The mechanical properties depend on the condition on delivery as defined in table 3.

8.2. In technological testing (drift expandig test and flattening test) the samples must comply with the requirements of sections 11.2.3.2. and 11.2.3.3.

8.3. In the case of other steel grades and/or other conditions on delivery then those specified in tables 2, 3 and 8, the mechanical and technological properties must be mutually agreed. In these cases, the tubes are supplied according to quality grade C.

8.4. The steels listed in table 2 are deemed to be suitable for welding because of their chemical composition and metal lurgical treatment.

In the BK or BKW conditions on delivery, the mechanical properties are modified in the zone which has been subjectes to heating. This should be taken into account (see DIN 8528 Part 1) in assessing the weldability of a component.

Steel grade
Condition on delivery
Cold-finished/hard
(BK) 3)
Cold-finished/soft
(BKW) 3)
Annealed
(GBK) 3)
Normalized
(NBK)
Code
number
Material number
Tensile
strength

Rm
N/㎟

min

Elonga-
tion at
repture

A5(%)

min

Tensile
strength

Rm
N/㎟

min

Elonga-
tion at
repture

A5(%)
min

Tensile
strength

Rm
N/㎟

min

Elonga-
tion at
repture

A5(%)
min

Tensile
strength

Rm
N/㎟

Upper
yield point

ReH
N/㎟

min
Elongation
at repture

A5(%)
min
St 30 Si
1.0211
400
8
330
12
280
30
290 to 420
215
30
St 30 Al
1.0212
400
8
330
12
280
30
290 to 420
215
30
St 35
1.0308
440
6
370
10
315
25
340 to 470
235
25
St 45
1.0408
540
5
470
8
390
21
440 to 570
255
21
St 52
1.0580
590
4
540
7
490
22
490 to 630
355
22


3) The yield point for the annealed (GBK)condition on delivery is at least 50% of the (ultimate) tensile strength. Depending upon the degree of deformation in the drawing operation, the yield point of tubes delivered in the cold-finished/hard (BK)and cold-finished/soft(BKW) conditions, may be increased to a level close to the tensile strength. In calculating the yield point, the following values are recommended : cold-finished/hard condition on delivery ≥ 80% of the tensile strength, cold-finished/soft condition on delivery ≥ 70% of the tensile strength.

4) In the case of tubes of outside diameter ≤ 30 mm, the wall thickness of which is ≤ 3mm, the minimum value of the yield point is 10 N /㎟ lower.



Tech & Service of Seamless pipe

Seamless pipes are extensively applied for the nuclear device, gas, petrochemical, ship building and boiler industries. Seamless pipes dominates 65% of market share in Chinese boiler industry.

How to make seamless pipe(seamless pipe process)?
Hot Piercing Workshop
Piercing process
The cross roll piercing and pilger rolling process in the size range from approx. 250 to 660 mm outside diameter.
Precision cold drawn steel tube production process
Pipe weld cracks
often follow different mechanisms can be divided into two types of thermal cracking and cold cracking.
How to calculate a steel pipe and tube theoretic weight
Calculate a steel pipe?
Pipe fittings are necessary to join together pipes, or to change the direction of an existing pipe.
Pipe beveling
Pipe beveling is the process where an angle is formed between the edge of the end of a pipe or tube and a plane perpendicular to the surface.
Steel pipe cutting machine
Pipe cutting
Cutting tools have a grinding wheel piece cutting machine (also known as toothless saw), hand saw, cutter and other hand tools.
How to calculate a steel pipe and tube theoretic weight
Packing the steel pipes
There are probably hundreds of different methods for packing a pipe, and most of them have merit, but there are two principles that are vital for any method.
Condition on delivery:

It refers to the state of final plastic deformation or final heat treatment of the delivered product. The hot-rolled or cold drawn (rolled) state or manufacturing state generally delivered without heat treatment; the heat-treated state after heat treatment delivery, or the normalizing, tempering, solid solution, annealing according to the type of heat treatment status.

Delivery status Abbreviation Description

Cold-finished/hard
(cold-finished as-drawn)

BK No heat treatment after the last cold-forming process. The tubes therefore have only low deformability.
Cold-finished/soft
(lightly cold-worked)
BKW After the last heat treatment there is a light finishing pass (cold drawing) With proper subsequent processing, the tube can be cold-formed (e.g. bent, expanded) within certain limits.
Annealed GBK After the final cold-forming process the tubes are annealed in a controlled atmosphere or under vacuum.
Normalized NBK The tubes are annealed above the upper transformation point in a controlled atmosphere or under vacuum.

Delivery according to actual weight or delivery according to theoretical weight

  • Actual weight - at the time of delivery, the weight of its product is delivered according to the weighing (weighing) weight;
  • Theoretical weight - The weight of the product at the time of delivery is calculated from the nominal size of the steel.
 


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