EN 10305-1 E255 seamless precision steel tubes are cold drawn seamless tubes in non-alloy quality E255 1.0408 precision steel tube grade, built for machinery, automotive and hydraulic parts that need tight OD and wall tolerances without a second machining pass. The grade name pins one number: the normalized (+N) minimum yield is 255 MPa (37,000 psi); order it stress-relieved (+SR) and that same tube reaches 375 MPa (54,400 psi). Which number you design to decides how much wall you pay for.
E255 is the middle rung of the EN 10305-1 carbon ladder - 20 MPa above E235 (1.0308) and 100 MPa below E355 (1.0580) - so it buys a little more margin than E235 without jumping to E355's cost. We supply it across OD 4–380 mm, wall 0.5–25 mm, in all five delivery conditions, with EN 10204 3.1 certification. Send your OD × wall and delivery condition for a quote.
Technical Specifications
| Parameter | Capability |
|---|---|
| Standard | EN 10305-1:2016 (Seamless cold drawn tubes for precision applications) |
| Steel grade / number | E255 / 1.0408 (St45 equivalent) |
| E255 dimensional tolerances OD 4–380 WT 0.5–25 | OD 4–380 mm (0.16–14.96 in); wall 0.5–25 mm (0.020–0.98 in) |
| Wall thickness tolerance | ±10% or ±0.1 mm, whichever is greater |
| Outside-diameter tolerance | ISO 7606 class 7 (standard), 8 or 9 available |
| Straightness | ≤ 0.0015 × length (ReH ≤ 500 MPa); ≈ 0.5–1 mm/m typical |
| Length | Random 3–12 m, exact length or cut-to-size on request |
| Surface finish | Bright drawn (Ra ≤ 1.6 µm for +A/+N); oiled or phosphate coated |
| E255 delivery condition +C +LC +SR +A +N | Cold drawn hard (+C), soft (+LC), stress relieved (+SR), annealed (+A), normalized (+N) |
| Certification | EN 10204 3.1; third-party inspection available |
Chemical Composition
The E255 chemical composition below is the cast-analysis limit per EN 10305-1:2016, Table 3. Carbon is capped at 0.21% to keep the steel weldable and fine-grained; the wide manganese band (0.40–1.10%) is what lets the same heat serve both drawn and normalized routes.
| Element | E255 (1.0408) max | Note |
|---|---|---|
| Carbon (C) | 0.21 | Low-carbon, weldable |
| Silicon (Si) | 0.35 | Deoxidation |
| Manganese (Mn) | 0.40–1.10 | Wide band supports drawn and normalized routes |
| Phosphorus (P) | 0.025 | Cleanliness limit |
| Sulfur (S) | 0.025 | Cleanliness limit |
| Aluminium (Al, total) | ≥ 0.020 (when killed) | Fine-grain practice |
Mechanical Properties
The E255 mechanical properties by delivery condition below are room-temperature minimums per EN 10305-1:2016, Table 4. Note the yield appears only for +SR and +N; for +C and +LC the standard defines yield as a fraction of tensile (≈0.8 Rm and ≈0.7 Rm), which is why those conditions are specified by tensile and elongation.
| Delivery condition | Rm, MPa (min) | ReH, MPa (min) | A, % (min) |
|---|---|---|---|
| +C (cold drawn, hard) | 580 | - (≈0.8 Rm) | 5 |
| +LC (cold drawn, soft) | 520 | - (≈0.7 Rm) | 8 |
| +SR (stress relieved) | 520 | 375 | 12 |
| +A (annealed) | 390 | - | 21 |
| +N (normalized) | 440–570 | 255 | 21 |
Tubes with OD ≤ 30 mm and wall ≤ 3 mm take a 10 MPa lower ReH minimum; for OD > 160 mm the +SR ReH floor is 420 MPa. These are standard Table 4 footnotes, not optional upgrades.
Choosing the Delivery Condition
| Condition | Yield, MPa | Use it when |
|---|---|---|
| +SR | 375 | Welded/bent parts, hydraulic barrels, any load where you want the highest yield at low cost |
| +N | 255 | Non-stressed or lightly loaded parts, lowest price, best formability |
| +A | - (Rm 390) | Heavy machining needing soft stock |
| +LC / +C | - (Rm 520 / 580) | Parts stay as-drawn and are not welded |
St45 and E255 Are the Same Steel
If a drawing calls out St45 = E255 (1.0408), it is asking for the same tube - St45 is the legacy DIN 2391 name, E255 the current EN 10305-1 designation, same chemistry and same normalized 255 MPa yield. Use St45 when matching an old print, and write E255 / 1.0408 on new orders so the certificate lines up with the current standard. For the naming decode and procurement write-up, see our St45 designation explainer (planned).
Across standards the nearest neighbours are DIN 2391 St45 and E255 equivalent ASTM A519 1020 - but the A519 match is by strength band only. A519 1020 allows Mn 0.30–0.60 %, narrower than E255's 0.40–1.10 %, so confirm chemistry and condition before treating the certificates as interchangeable. Other routes: GOST 9567-75 (20), GB/T 3639 (20#), BS 6323-4, NF 699.
Applications
E255 tubes go where dimensions and a predictable yield matter more than high strength. Five application groups cover most orders:
Hydraulic and pneumatic cylinders
Cold drawn +SR or +N tubes are honed or SRB-finished into cylinder barrels; the stable yield and straightness keep bore geometry after welding.
Mechanical and automotive structures
Axles, seat rails, steering columns and chassis sleeves use the tight tolerances to cut machining scrap.
General engineering and machined parts
Bushings, spacers and sleeves are cut and turned from +A or +N stock where softness aids chip control.
Gas springs and shock components
Smooth drawn bores and controlled wall give consistent stroke performance.
Pressure-rated small assemblies
Where wall and yield are matched to a known pressure, +SR gives the highest margin per kilogram of the five conditions.
Why Source E255 Precision Tubes from GNEE
Five delivery conditions in stock range, OD 4–380 mm, wall 0.5–25 mm.
EN 10204 3.1 certificates with heat and cast traceability on every length.
EN ISO 10893 NDT (eddy current / flux leakage / ultrasonic) by agreement.
Technical team confirms the grade, condition and edition before quotation; third-party inspection supported.
Quality Control and Testing
Chemistry and tensile. Cast analysis plus room-temperature tensile per EN 10305-1, Table 3/4.
Longitudinal NDT. EN ISO 10893 NDT - eddy current (EN ISO 10893-2, level E3), flux leakage (EN ISO 10893-3, level F3) or ultrasonic (EN ISO 10893-10, level U3B) by agreement.
Dimension and surface. 100% OD/wall check and full-length surface inspection; flattening or flaring tests where specified.
Certificate. EN 10204 3.1 with heat and cast traceability; third-party witness available.
Test and inspection
Packaging and shipping
Send your OD × wall, delivery condition and quantity - our technical team will confirm the specification and return a quotation with lead time within 24 hours.
Request an E255 Precision Tube Quote
FAQ
What is EN 10305-1 E255 and what does the number mean?
E255 (material number 1.0408) is a non-alloy quality steel for cold drawn seamless precision tubes under EN 10305-1:2016. The "255" is the minimum upper yield strength in the normalized (+N) condition - 255 MPa (37,000 psi). The same tube in the stress-relieved (+SR) condition reaches 375 MPa, so the name reflects only one of its delivery states.
Is E255 the same as St45?
Yes. E255 and St45 are the same steel under material number 1.0408. St45 is the legacy DIN 2391 name; E255 is the current EN 10305-1 designation. They share the same chemistry and the same normalized 255 MPa yield. Use St45 when matching an old drawing, and write E255 / 1.0408 on new orders so the certificate matches the current standard.
Why does E255 show two yield strengths, 255 MPa and 375 MPa?
Because the yield depends on the delivery condition, not the grade alone. In the normalized (+N) condition the minimum upper yield is 255 MPa; in the stress-relieved (+SR) condition it is 375 MPa - a 120 MPa gap from cold work plus stress relief. Design to the value of the condition you actually order. A +SR tube carries about 47% more pressure at the same wall, or needs roughly 32% less wall for the same pressure.
What delivery condition should I choose for E255 precision tubes?
Pick by what the tube undergoes next. Welded or bent parts and hydraulic barrels usually take +SR (375 MPa, stable dimensions, good weldability). Non-stressed or lightly loaded parts can use +N (255 MPa, lowest cost). +C and +LC are for parts that stay as-drawn and are not welded. +A is for heavy machining where softness helps chip control.
What are the dimensions and tolerances of E255 precision tubes?
EN 10305-1 covers OD 4–380 mm (0.16–14.96 in) and wall thickness 0.5–25 mm (0.020–0.98 in). Wall tolerance is ±10% or ±0.1 mm, whichever is greater. Outside-diameter tolerance is taken from ISO 7606 classes 7/8/9. Straightness is ≤ 0.0015 × length for ReH ≤ 500 MPa. Bright (+A/+N) surfaces reach Ra ≤ 1.6 µm.
Is E255 equivalent to ASTM A519 1020?
Approximately, by strength band, but not identical in chemistry. ASTM A519 1020 (C 0.18–0.23 %, Mn 0.30–0.60 %) sits in the same yield range as E255, yet E255 allows Mn 0.40–1.10 %. For a like-for-like substitution confirm the manganese and the delivery condition, and do not assume the certificates are interchangeable without checking the order spec.
What certificate and non-destructive testing come with E255 tubes?
Each order ships with an EN 10204 3.1 inspection certificate tracing heat and cast numbers. Longitudinal defect inspection follows EN ISO 10893-2 (eddy current, level E3), EN ISO 10893-3 (flux leakage, level F3) or EN ISO 10893-10 (ultrasonic, level U3B). Third-party inspection is available on request.
Can E255 be supplied above 380 mm outside diameter?
EN 10305-1 scopes seamless cold drawn precision tubes up to 380 mm OD. For larger diameters the right route is a different standard - EN 10297-1 (machinery tubes) or EN 10305-4 for hydraulic and pneumatic systems, where E255 is supplied in the +N condition only. State the application so the mill quotes the correct certificate basis.
