198205, г. Санкт-Петербург,
Таллинское шоссе, д. 198, корп.2, этаж 2, офис 205
тел. +7 (812) 325-23-47, 325-23-45, 325-23-46, 327-18-80
факс +7 (812) 325-2347

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.

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