DIN2391 St35.0 St37.0 St44.0 St45St52.0 BKW BKS GBK NBK Seamless Precision Cold Drawn Steel Tubes
Standard: DIN2391 Seamless Cold Drawn/Rolling Steel Tubes
Applications: for Auto industry / for machinery use / Oil Cylinder Tube / Motorcyle shock absorber
Auto shock absorber innder cylinder / Telescopic Cylinders
Size range: O.D.:6-350mm W.T.:1-50mm L:max12000mm
Materials:
The tubes are manufactured from electric steel or basic oxygenn stel, the melting and casting processes being at the discretion of the manufacturer.
The steel is cast as kiiled steel
Apperance:
Tubes have a smooth internal and external surface with the cold working process
Tube ends:
Square cut, no burrs
Steel Grade and Chemical Compositions:
| Steel Grade | C | Si | Mn | P | S | |
| max | max | max | max | |||
| ST35 | 0.17 | 0.35 | ≥0.40 | 0.025 | 0.025 | |
| ST45 | 0.21 | 0.35 | ≥0.40 | 0.025 | 0.025 | |
| ST52 | 0.22 | 0.35 | ≥1.60 | 0.025 | 0.025 |
| Mechanical properties at room temperature | ||||||||||
| Steel Grade | Minimum values for the delivery condition | |||||||||
| BKW | BKS | GBK | (+N) NBK | |||||||
| ST35 | 480 | 6 | 420 | 10 | 420 | 315 | 14 | 340-470 | 235 | 25 |
| ST45 | 580 | 5 | 520 | 8 | 520 | 375 | 12 | 440-570 | 235 | 21 |
| ST52 | 640 | 4 | 580 | 7 | 580 | 420 | 10 | 490-630 | 355 | 22 |
Note: Special steel grade is also available, according to customer request.
Final Supply Condition:
BK - Cold finish (hard)
Tubes do not undergo heat treatment following the final cold forming and, thus
have a rather high resistance to deformation
BKW - Cold finished(soft)
The final heat treatment is followe by cold drawing involving limited deformation.
Appropriate further processing allow a certain degree of cold forming (bending,
expanding)
BKS - Cold finished and stress-relieved
Heat treatment is applied following the last cold forming process. Subject to appropraite processing conditions, the increase in the residual stresses involved enables both forming and machining to a certain degree.
GKB - Annealed
The last cold forming process is followed by annealing in a controlled atmosphere.
NBK - Normalized
The last cold forming process is followed by annealing above the upper transformation point in a controlled atmosphere.
Testing:
1. dimensional chec
2. surface inspection
3. tensile test as DIN EN10002 Part 1
4. flattening test, as DIN EN10233
5. drift expanding test as DIN EN10234
