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DIN 2391 Seamless Precision Steel Tubes

St30si, St30Al, St35, St45, St52

DIN2391 St30Si, St30Al, St35, St45, St52 is the standard applicable to Seamless precision steel tubes.

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DIN 2391 Seamless Precision Steel Tubes in bundles

DIN 2391 Seamless Precision Steel Tubes

DIN2391 Part 2 specifies dimensions for cold finished, seamless precision steel tubes and is to be used in conjunction with DIN2391 part2 which states the relevant technical delivery conditions. The preferred sizes listed in standard are mainly used in mechanical and automotive engineering.

Where steel tubes of dimensions specified in this standard are to comply with the technical delivery conditions listed in subclause 1.2 of DIN 2391 Part 2.

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

Chemical Composition

StandardGradeChemical Components (%)
SymbolMaterial No.CSiMnPS
DIN2391St 30 Si1.0211≤0.10≤0.10≤0.55≤0.025≤0.025
St 30 Al1.0212≤0.10≤0.05≤0.55≤0.025≤0.025
St 351.0308≤0.17≤0.35≥0.40≤0.025≤0.025
St 51.0408≤0.21≤0.35≥0.40≤0.025≤0.025
St 521.058≤0.22≤0.55≤1.60≤0.025≤0.025

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.

Delivery Condition Symbol in accordance with EN10305 and DIN2391.

Symbol in accordance with EN 10305 Symbol in accordance with DIN2391

Mechanical Properties.

Mechanical properties at room temperature
Steel GradeMinimum values for the delivery condition
Steel NameSteel NumberBKBKWBKSGBKNBK
RmA %RmA %RmReHA %RmA %RmReHA %
St 30 Si1.02114308380123802801628030290 to 42021530
St 30 Al1.02124308380123802801628030290 to 42021530
St 351.03084806420104203151431525340 to 47023525
St 451.0408580552085203751239021440 to 57025521
St 521.0580640458075804201049022490 to 63035522

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.

Size: 6mm-350mm.

W.T.: 0.8mm-50mm.

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: St30 Si, St30 Al, St35, St45, St52.


The following marking shall be shown on a label attached to the bundle:

  • the manufacturer’s name or trade mark;
  • the specified dimensions;
  • the number of this European Standard;
  • the steel name or number;
  • the cast number;
  • the delivery condition;
  • in the case of specific inspection, an identification number (e. g. order or item number) which permits the correlation of the product or delivery unit to the related document.


  • 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.

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

DIN 2391 BK Seamless Precision Steel Tubes

DIN 2391 BK Seamless Precision Steel Tubes

DIN 2391 NBK Seamless Precision Steel Tubes

DIN 2391 NBK Seamless Precision Steel Tubes

DIN2391 Package Photos, Wooden Cases with steel frame

DIN2391 Package Photos

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