Difference between S355G8+N and S355G7+N steel plate

Jan 14, 2026 Leave a message

The main difference is that S355G8+N is a higher-specification offshore structural steel than S355G7+N, both under EN 10225, with the 'G' number indicating increasing quality/toughness requirements (G8 better than G7); both are normalized ('+N') for enhanced properties, but S355G8+N generally offers superior toughness, particularly Charpy V-notch impact values at low temperatures, making it better for demanding offshore platform roles than S355G7+N.

S355G7+N Steel plate Chemical Composition

S355G7+N Chemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	Al	N
S355G7+N	0.14	0.15-0.55	1.0-0.01	0.02	0.01	0.0055	0.01
	Nb	V	Ti	Cu	Cr	Ni	Mo
	0.04	0.06	0.025	0.3	0.25	0.5	0.08

S355G8+N Steel plate Chemical Composition

S355G8+N Chemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	Al	N
S355G8+N	0.14	0.15-0.55	1.0-0.01	0.02	0.01	0.0055	0.01
	Nb	V	Ti	Cu	Cr	Ni	Mo
	0.04	0.06	0.025	0.3	0.25	0.5	0.08

S355G7+N Steel plate Mechanical Properties

S355G7+N high strength property
Grade		Mechanical Property			Charpy V Impact Test
Grade	Thickness	Yield	Tensile	Elongation	Degree	Energy 1	Energy 2
S355G7+N	mm	Min Mpa	Mpa	Min %	-40	J	J
	t≤50	355	470-630	22%		50	50
	50＜t≤63	355	470-630	22%		50	50
	63＜t≤100	325	490-630	22%		50	50
Note: Energy 1 is transverse impact test, Energy 2 is longitudinal

S355G8+N Steel plate Mechanical Properties

Grade	S355G8+N Mechanical Properties (min)
	Tensile Strength		Yield Strength						Elongation A
	Thickness (mm)		Thickness t - mm						Elongation A
	≤100	>100	≤16	16<t≤25	25<t≤40	40<t≤63	63<t≤100	100<t≤150	%
S355G8+N	470/630	460/620	355	355	345	335	325	320	22

Key difference
Grade (G7 vs. G8): The 'G' in the designation refers to offshore steel grades, with higher numbers (like G8) signifying more stringent requirements, especially for toughness and impact strength, crucial for harsh marine environments.
Performance: S355G8+N provides better ductility and fracture resistance (toughness) compared to S355G7+N, crucial for resisting crack propagation in offshore structures.
Application: Both are used for offshore platforms, but G8 is preferred for more critical areas needing higher safety margins, while G7 serves broader structural roles.
Similarities
Base Grade (S355): Both offer a minimum yield strength of 355 MPa (hence '355').
Condition (+N): Both are supplied in the Normalized condition (N), a heat treatment that refines grain structure, improving strength and toughness.
Standard: Both conform to the European standard EN 10225 for offshore steels.