Q355NB High Strength Low Alloy Structural Steel

Name: Q355NB High Strength Low Alloy Structural Steel
Brand: Cehe Steel
SKU: Q355NB

Compliant with GB/T 1591-2018 | Normalized / Normalized Rolled (N) Delivery

Normalized (N) Grade B 20°C Impact Fine Grain Steel

4.1 Designation System

Format: Q + Minimum Upper Yield Strength + Delivery Condition Code + Quality Grade (B, C, D, E, F)

Example Q355NB: Q = Yield strength, 355 = Minimum yield value (MPa), N = Normalized/Normalized rolling, B = Quality grade B

Note 1: Normalized condition includes normalized + tempering. N code represents both normalized and normalized rolling.

Note 2: Q + minimum upper yield strength + delivery condition code = "Steel grade".

For Z-direction property: Add suffix like Q355NBZ25

7.3 Delivery Condition

Q355NB steel is supplied in Normalized (N) or Normalized Rolling (N) condition.

Note: Normalized condition includes normalized + tempering. Normalized rolling is a rolling process where final deformation is carried out in a certain temperature range to achieve a condition equivalent to normalized.

Table 3 Chemical Composition (Ladle Analysis) — Normalized Q355NB

Grade	Quality	C max	Si max	Mn	P max	S max	N max	Alt min	Microalloy	Additional
Q355N	B	0.20	0.50	0.90-1.65	0.030	0.025	0.012	0.015	Nb+V+Ti≤0.22^b	—

^a For normalized/normalized rolled steel: Al ≥0.015%, Nb+V+Ti ≤0.22% (fine grain elements).

^b For normalized steel (Q355NB), the total content of Nb, V, Ti shall not exceed 0.22%.

^c Nitrogen content analysis may be omitted if guaranteed by supplier.

^d Product analysis tolerance according to GB/T 222.

^e For supply of commercial steel billets, lower limit of chemical composition may be agreed upon.

^f When thickness direction performance (Z-direction) is required, sulfur content shall comply with GB/T 5313.

Table 4 Carbon Equivalent CEV (max) — Normalized Q355NB

Grade	Quality	≤63mm	>63-100mm	>100-250mm	>250-400mm	Note
Q355N	B	0.43	0.45	0.45	Agreement	^a

^a For thickness >250-400mm, CEV value shall be agreed upon between supplier and purchaser.

Table 9 Tensile Properties — Normalized Q355NB

Thickness (mm)	Upper Yield Strength (MPa) min	Tensile Strength (MPa)	Elongation A% min	Note
≤16	355	470-630	22	^a
>16-40	345
>40-63	335
>63-80	325
>80-100	315	470-630
>100-150	295	470-630
>150-250	285	450-600	22	^b
>250-400	275	450-600	22	^b

^* When yield point is not obvious, Rp0.2 may be used instead of upper yield strength.

^a For plates and coils with nominal width ≥600mm, transverse specimens; for other steel products, longitudinal specimens.

^b For thickness >150-400mm, only applicable for quality grade D and higher (not for Grade B).

Table 11 Charpy V-Notch Impact Test — Q355NB

^a For nominal thickness ≥6mm or diameter ≥12mm, impact test shall be performed. Standard specimen: 10×10×55mm. For smaller sizes: 10×7.5×55mm (75% of specified value) or 10×5×55mm (50% of specified value). Impact test takes longitudinal specimens by default. Transverse specimens may be taken by agreement. When the supplier does not specify the test temperature, grade B shall be tested at 20°C.

Table 12 Bending Test (180°) — Q355NB

Quality Grade	Test Temperature	Longitudinal KV2 (J) min	Transverse KV2 (J) min	Note
B	20°C	34	27	^a

Thickness (mm)	Bending Diameter D	Note
≤16	D = 2a (a = specimen thickness)	^a
>16-100	D = 3a	^a

^a For plates and coils with nominal width ≥600mm, transverse specimens; for other steel products, longitudinal specimens. If the supplier can guarantee bending test qualification, the test may be omitted.

Appendix A International Grade Comparison — Q355NB

GB/T 1591-2018	EN 10025-3	ISO 630-3	Previous GB/T 1591-2008	Note
Q355NB (Normalized)	S355N	—	Q345B (Normalized)	^a

^a Q355NB replaces Q345B normalized grade with improved mechanical properties (increased by 10-15 MPa). EN 10025-3 S355N is the European equivalent for normalized fine grain structural steel.

CEV formula: CEV(%) = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15

Note: Carbon equivalent (CEV) based on ladle analysis.

Product Page: Q355NB Grade Comparison

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