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EN 10120 P355NB steel, also written as P355NB (1.0557), DIN EN 10120 P355NB and BS EN 10120 P355NB, is a non-alloy quality steel delivered as sheet and strip up to 5 mm thick for welded gas cylinders. Gangsteel (HENAN GANG IRON AND STEEL) produces and exports P355NB coil, slit strip, cut sheet and circular blanks with EN 10204 3.1/3.2 certificates for cylinder makers.
Data source: EN 10120:2017 (supersedes EN 10120:2008), Clause 6 and Tables 1 and 3. The current edition covers five grades: P245NB, P265NB, P310NB, P355NB, HCT600XB. The main change against 2008 is the addition of the cold-rolled dual-phase grade HCT600XB. Always confirm the edition named on the purchase order.
| C max | Si max | Mn | P max | S max | Al total min | N max | Nb max | Ti max |
|---|---|---|---|---|---|---|---|---|
| 0.20 | 0.50 | ≥ 0.70 | 0.025 | 0.015 | 0.020 | 0.009 | 0.050 | 0.03 |
Al total may partly be replaced by Nb ≤ 0.050% and/or Ti ≤ 0.03%, reported on the inspection document. N may be up to 0.012% when Al total / N ≥ 2.2 or when Nb and/or Ti are added. Elements not listed may not be intentionally added without the purchaser's agreement, except for finishing the cast. Product analysis deviations follow Table 2 of the standard.
| Thickness e (mm) | Upper yield strength ReH min (MPa) | Tensile strength Rm (MPa) | Elongation min (%) |
|---|---|---|---|
| e < 3 | 355 | 510–620 | 19 (A80, L0 = 80 mm) |
| 3 ≤ e ≤ 5 | 355 | 510–620 | 24 (A5.65√S0) |
Values apply to transverse test pieces in the normalized or normalizing rolled condition, even when the strip is delivered hot rolled, so the cylinder keeps its properties after normalizing. Table 3 of EN 10120 also gives guidance on heat treatment; Gangsteel quotes the actual normalizing range on the order confirmation.
EN 10120 lists three usual delivery conditions: hot rolled and normalized (N, including normalizing rolling), hot rolled (AR) and cold rolled. N delivery is used for cylinders that are only stress relieved after welding; AR delivery is only for cylinders normalized after welding. P355NB is normally ordered as N or AR hot-rolled pickled and oiled strip.
EN 10120 applies to sheet and strip up to 5 mm. Gangsteel supplies P355NB typically from about 1.5 to 5 mm (HCT600XB in thinner cold-rolled gauges), as coil, slit coil, cut sheet or circular blanks, with tolerances to EN 10051 (hot rolled) or EN 10131 (cold rolled). Each test unit is checked for cast analysis and transverse tensile properties, and EN 10204 3.1 or 3.2 documents are issued; SGS, BV, TUV or Lloyd's inspection can be arranged.
P355NB is the highest-strength NB grade for lightweight welded cylinders, high-pressure industrial gas cylinders, fire extinguishers and vehicle LPG tanks where weight saving matters. Weldability is a key requirement of the standard, so the chemistry is kept lean in carbon and sulphur for MAG and submerged-arc welding of cylinder seams.
| Standard | Comparable grade (approximate) |
|---|---|
| EN 10120 | P355NB / 1.0557 |
| Former and international grades | DIN 17155 19Mn6 (closest former grade), NF A36-211 BS 4, UNI 7355 Fe E 35 KR, BS 5045 Type E, JIS G3116 SG365 |
| Other EN 10120 grades | P245NB | P265NB | P310NB | HCT600XB |
Equivalents are engineering references only; chemistry limits, test direction and delivery condition differ, so dual certification requires the stricter combined limits on the order and the mill certificate.
EN 10120 P355NB (steel number 1.0557) is a non-alloy quality steel supplied as sheet and strip up to 5 mm thick for the manufacture of welded gas cylinders. It is ordered to EN 10120:2017, which superseded EN 10120:2008, and the general delivery conditions of EN 10021 also apply.
EN 10120 covers sheet and strip only, with a maximum thickness of 5 mm, so P355NB is normally delivered as hot-rolled or cold-rolled coil, slit coil or cut sheet and circular blanks rather than heavy plate. Buyers often search for it as gas cylinder steel plate, but the product form on the order should be sheet or strip.
The cast analysis of P355NB is C 0.20% max, Si 0.50% max, Mn ≥ 0.70%, P 0.025% max and S 0.015% max, with Al total at least 0.020%, N 0.009% max, Nb 0.050% max and Ti 0.03% max.
P355NB must reach an upper yield strength ReH of at least 355 MPa and a tensile strength of 510–620 MPa. Minimum elongation is 19% on A80 for thickness below 3 mm and 24% on A5.65√S0 for 3 to 5 mm, tested on transverse samples in the normalized condition.
P355NB is usually supplied hot rolled and normalized or normalizing rolled (N) when the cylinder is only stress relieved after welding, or hot rolled (AR) when the finished cylinder is normalized after welding. Cold rolled delivery is also possible, and the condition must be stated on the order.
Former and international designations that correspond to P355NB include DIN 17155 19Mn6 (closest former grade), NF A36-211 BS 4, UNI 7355 Fe E 35 KR, BS 5045 Type E, JIS G3116 SG365. These are engineering comparisons only, so the order and certificate should name EN 10120 P355NB.
P355NB is the highest-strength NB grade for lightweight welded cylinders, high-pressure industrial gas cylinders, fire extinguishers and vehicle LPG tanks where weight saving matters.
State the quantity, product form, nominal dimensions, EN 10120, the steel name P355NB or number 1.0557, the delivery condition and the inspection document, for example: 10 t sheet 600 x 1200 x 4.0 EN 10120 P355NB normalized and oiled EN 10204-3.1.
Gangsteel supplies EN 10120 P355NB with an EN 10204 3.1 inspection certificate showing cast analysis and transverse tensile results per test unit, and 3.2 certificates with third-party inspection are available on request.
EN 10120 Hub | EN 10120 P245NB | EN 10120 P265NB | EN 10120 P310NB | EN 10120 P355NB | EN 10120 HCT600XB | DIN 17155 | EN 10028-4 | Boiler Steel Plate | Pressure Vessel Steel Plate
