Most tube problems we see from new customers do not come from bad steel. They come from a specification that was not fully spelled out. Two orders can both say "seamless tube, EN 10216" and receive two completely different products. Here is how to read the standard so your next order arrives exactly as intended.
The grade: E235 or E355
EN 10216 series covers seamless steel tubes for pressure purposes. The "E" number is the minimum yield strength in MPa. E235 (the successor of St 37) yields at 235 MPa; E355 (successor of St 52) yields at 355 MPa.
- E235 — general structural and mechanical tubing, easy to bend and weld. Right for frames, guards and low-load structures.
- E355 — the default choice for crane structures, hydraulic cylinders, booms and pinned joints, where the tube itself carries load.
If your drawing is silent on grade, tell us the application. Recommending the correct grade is part of the quotation — not an upsell.
The delivery condition: +N, +A or +SR
The suffix after the grade describes the heat treatment state in which the tube leaves the mill:
- +N (normalized) — uniform grain structure, the standard for E355 structural and hydraulic use.
- +SR (stress relieved) — lower residual stress, useful where machining distortion must stay small.
- +A (annealed) — softest condition, easiest for cold forming and deep machining.
Machinability, distortion and final strength all depend on this letter. A tube delivered +A and one delivered +N of the same grade will machine — and behave — differently.
Tolerances: outside diameter, wall and straightness
EN 10216 gives standard tolerance classes, but crane builders usually need better than standard. Typical requirements we work to:
- OD tolerance down to ±0.5% for tubes that enter machined assemblies
- Wall thickness selected to guarantee minimum wall after honing or skiving
- Straightness specified when tubes run through long machining operations
What to confirm before you order
- Grade and delivery condition (e.g. E355+N)
- Standard vs tighter tolerances for OD, ID and wall
- Required documents — EN 10204 3.1 certificates with heat-number traceability ship with every HCGR order as standard
- Length: random lengths, fixed lengths or cut-to-size with end finishing
Send us the drawing or the application description. We quote within 24 hours, with the grade, condition and tolerances written out clearly — so what arrives is what you specified.
Need these parts made to your drawing? Send your specification — clear quotation within 24 hours, EN 10204 3.1 certificates as standard.
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