Sunny Steel offers an extensive range of seamless precision steel tubes. The seamless precision steel tubes can be used for a wide range of precision mechanical spare for car and cylinder accord to standard DIN2391/ EN10305-1/ GB/T3639-2009.
Seamless Precision Steel Tubes according to EN 10305-1
- Standard: DIN2391 part 2 , DIN EN10305-1, DIN17175 etc;
- Material: ST35,ST45,ST52.
- Manufacturing method: cold-rolled / cold-drawn
- Delivery condition: BK,BKS,SR,GBK,NBK.
- Certificate
- Factory Certification: 2.2 according to EN
- Acceptance Test Certificate:3.1 according to EN 10204
- Packing:
- in bundles tied with steel strips. External packing by wooden cases if the wall thickness/OD ratio is low.
- Oil-coating is generally necessary especially for export.
- Application:
Used in hydraulic & pneumatic cylinder ,automobile and other mechanical device .Feature: high precision and high brightness, the inner and outer surface of the tubes have high cleanness without oxid, mechanical properties of the final tubes also come out excellent, promising no leakage under high pressure, no deformation after cold-bent and no cracks when flaring and flattening, ensuring the efficient operation in all service.
DIN 2391-81 Part 2 Seamless Precision steel tubes(DIN2391-81)
Standard DIN 2391 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.
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(%)
| Code number | Material number | Mfg. Process | C max | Si max | Mn max | P max | S max |
| St35 | 1.0308 | S | 0.17 | 0.35 | 0.4 | 0.05 | 0.05 |
| St45 | 1.0408 | S | 0.21 | 0.35 | 0.4 | 0.05 | 0.05 |
| St52 | 1.0508 | S | 0.22 | 0.55 | 1.6 | 0.05 | 0.05 |
Mechanical and technological properties
| Code number | Material number | Cold-finished hard(BK) | Cold-finished/soft (BKW) 3) | ||
| Rm(Mpa) | A(%) | Rm(Mpa) | A(%) | ||
| St 35/E235 | 1.0308 | 480 | 6 | 420 | 10 |
| St 45 | 1.0408 | 580 | 5 | 520 | 8 |
| St 52/E355 | 1.0508 | 640 | 4 | 580 | 7 |
| Code number | Cold finished (soft)(BKW) | Annealed (GBK) | Normalized (NBK) | |||||
| Rm(Mpa) | ReH (Mpa) | A(%) | Rm(Mpa) | A(%) | Rm (Mpa) | ReH (Mpa) | A(%) | |
| St 35/E235 | 420 | 315 | 14 | 315 | 25 | 340-470 | 235 | 25 |
| St 45 | 520 | 375 | 12 | 390 | 21 | 440-570 | 255 | 21 |
| St 52/E355 | 580 | 450 | 10 | 490 | 22 | 490-630 | 355 | 22 |
Note:
- 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.
Quality grade
The tubes are supplied in the following quality grades :
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.
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.
Condition 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. |
