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DIN2391 St35 NBK is the standard applicable to Seamless precision steel tubes

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DIN 2391 seamless precision tubes applications —Used in Hydraulic & pneumatic cylinder, Mechanical and Automotive engineering

Technical delivery conditions:

  • Part 1: Seamless cold drawn tubes.

Chemical Composition

StandardGradeChemical Components (%)
SymbolMaterial No.CSiMnPS
DIN2391St 351.0308≤0.17≤0.35≥0.40≤0.025≤0.025

Click to download the details of DIN2391 ST35 NBK seamless tubes.

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Delivery Conditions

The tubes shall be manufactured from cold drawn or cold rolled processes. The tubes shall be supplied in one of the delivery conditions as follows:

Cold finished (hard)BKTubes do not undergo heat treatment following the final cold forming and thus, have a rather high resistance to deformation.
Cold finished (soft)BKWThe final heat treatment is followed by cold drawing involving limited deformation. Appropriate further processing allows a certain degree of cold forming (e.g. bending, expanding).
Cold finished and stress-relievedBKSHeat treatment is applied following the last cold forming process. Subject to appropriate processing conditions, the increase in the residual stresses involved enables both forming and machining to a certain degree.
AnnealedGBKThe last cold forming process is followed by annealing in a controlled atmosphere.
NormalizedNBKThe last cold forming process is followed by annealing above the upper transformation point in a controlled atmosphere.

Mechanical Properties

Mechanical properties at room temperature
Steel GradeMinimum values for the delivery condition
Steel NameSteel NumberBKBKWBKSGBKNBK
RmA %RmA %RmReHA %RmA %RmReHA %
St 351.03084806420104203151431525340 to 47023525


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Inspection and test list for the DIN 2391 Standard

Inspection or test typesTest frequency
Internal testAcceptance test
Chemical analysisMM
Tensile testingMOne per tested batch
Flattening test or extension testMTwo per tested batch
Dimension verificationMM
Visual inspectionMM
NDT in order to identify leaksIndividualIndividual

Standard: DIN 2391

Description Name: DIN 2391 Seamless cold drawn tubes, DIN 2391 Seamless precision steel tubes, ST35 Precision tubes, ST45 Precision tubes, ST52 Precision tubes, Seamless precision tubes, DIN 2391 ST35 Seamless precision steel tubes, DIN 2391 ST45 Seamless precision steel tubes, DIN 2391 ST52 Seamless precision steel tubes, ST 52 Honed tubes, ST52 cylinder tubes


OD.: 4mm-89mm

W.T.: 0.6mm-20mm

Shape: Round

Production type: Cold drawn or cold rolled

Length: Single random length/ Double random length or as customer’s actual request max length is 10m

Grade:  St35


  • Mill test certificates will be issued according to EN10204.3
  • The tubes Shall be Seamless cold drawn or cold rolled.
  • The manufacture should have TS16949 certificate or ISO9000 certificate.

Protection and Packing:

  • Packed in wooden box or bundles protected with plastic paper, and suitably protected for sea-worthily delivery or as requested.
  • The tubes shall be delivered with a temporary corrosion protection. The type of protection shall be at the discretion of the manufacturer


apply to the Precision steel tubes used.

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Photos for DIN2391 ST35 NBK

DIN2391 ST35 NBK seamless tubes

DIN2391 ST35 NBK seamless tubes

DIN2391 ST35 NBK surface

DIN2391 ST35 NBK surface

DIN2391 ST35 NBK OD inspection

DIN2391 ST35 NBK OD inspection

DIN2391 ST35 NBK thickness inspection

DIN2391 ST35 NBK thickness inspection

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