Difference Between P355N and P355NH

Nov 27, 2025 Leave a message

The main difference is their intended use: P355N is for room-temperature applications, while P355NH is a normalized steel specifically for elevated temperature service. While both share similar mechanical properties at room temperature, P355NH is designed to retain strength and properties at higher temperatures, making it suitable for applications like pressure vessels in hot environments.

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Chemical Composition for P355N and P355NH

P355N Chemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	Al(min)	N
P355N	0.20	0.50	0.9-1.70	0.03	0.025		0.02
	Cr	Cu	Mo	Nb	Ni	Ti	V
	0.30	0.30	0.08	0.005	0.50	0.03	0.10

Carbon Equivalent: Ceq = 【C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15】%

P355NH Chemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	Al(min)	N
P355NH	0.20	0.50	0.9-1.70	0.03	0.025		0.02
	Cr	Cu	Mo	Nb	Ni	Ti	V
	0.30	0.30	0.08	0.005	0.50	0.03	0.10

Carbon Equivalent: Ceq = 【C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15】%

Mechanical Property for P355N and P355NH

Grade		P355N Mechanical Property
Grade	Thickness	Yield	Tensilmie	Elongation	Impact Energy(KV J) min
P355N	mm	Min Mpa	Mpa	Min %	-20°	0°	+20°
	≤ 16	355	490-630	22	40	47	55
	16> to ≤35	355	490-630	22	40	47	55
	35> to ≤50	345	490-630	22	40	47	55
	50> to ≤70	325	490-630	22	40	47	55
	70> to ≤100	315	470-610	21	40	47	55
	100> to ≤150	295	450-590	21	40	47	55

Grade		P355NH Mechanical Property
Grade	Thickness	Yield	Tensilmie	Elongation	Impact Energy(KV J) min
P355NH	mm	Min Mpa	Mpa	Min %	-20°	0°	+20°
	≤ 16	355	490-630	22	47	55	63
	16> to ≤35	355	490-630	22	47	55	63
	35> to ≤50	345	490-630	22	47	55	63
	50> to ≤70	325	490-630	22	47	55	63
	70> to ≤100	315	470-610	21	47	55	63
	100> to ≤150	295	450-590	21	47	55	63