CCS AH550 (A550) Steel Plate – Properties & Equivalents

CCS AH550 (also written CCS A550, CCS/A550, CCS Grade A550 or AH550 steel plate) is a high-strength steel for welded marine and offshore structures certified by the China Classification Society (CCS) to CCS Rules for Materials and Welding (2024), Part 1, Chapter 3, Section 4 (High Strength Steels for Welded Structures). The number 550 is the minimum yield strength in MPa (up to 50 mm), tensile strength is 640–820 MPa, and the letter A sets the Charpy V-notch test temperature of 0°C. It is delivered thermo-mechanically rolled (TM) or quenched and tempered (QT) and corresponds to grade AH550 in IACS UR W16.

Gangsteel, a steel plate exporter, supplies CCS AH550 plate with CCS class certificates; the requirements below are taken directly from the current CCS rules.

Related CCS grades: CCS DH550 steel plate, CCS EH550 steel plate, CCS FH550 steel plate, CCS AH500 steel plate, CCS AH620 steel plate.

CCS AH550 chemical composition

CCS AH550 chemical composition, heat (ladle) analysis, % max unless stated, by delivery condition

Element	Heat analysis, TM	Heat analysis, QT
C	≤ 0.16	≤ 0.18
Mn	1.00–1.70	≤ 1.70
Si	≤ 0.60	≤ 0.80
P	≤ 0.025	≤ 0.025
S	≤ 0.015	≤ 0.015
Al (total)	≥ 0.02	≥ 0.018
Nb	≤ 0.05	≤ 0.06
V	≤ 0.12	≤ 0.12
Ti	≤ 0.05	≤ 0.05
Ni	≤ 2.00	≤ 2.00
Cu	≤ 0.55	≤ 0.50
Cr	≤ 0.50	≤ 1.50
Mo	≤ 0.50	≤ 0.70
N	≤ 0.025	≤ 0.015

 

Source: CCS Rules for Materials and Welding (2024), Part 1, Chapter 3, Table 3.4.3.2 (same values as IACS UR W16 Rev.3). Notes: Nb+V+Ti ≤ 0.26% and Mo+Cr ≤ 0.65% (not applicable to QT); total Al/N ≥ 2:1 unless other nitrogen-binding elements are used; Ni above 2.00% may be approved by CCS; boron, if added, ≤ 0.005%. CCS specifies the chemical composition as a heat (ladle) analysis only; the Rules give no product (check) analysis tolerances for these plates, so no product-analysis column is shown. If a product analysis is required, agree the tolerances in the order.

CCS AH550 mechanical properties and impact test

CCS AH550 tensile and Charpy V-notch requirements

Thickness (mm)	Yield ReH min (MPa)	Tensile Rm (MPa)
3 ≤ t ≤ 50	550	640–820
50 < t ≤ 100	530	640–820
100 < t ≤ 250	490	590–770

CCS AH550 elongation and impact energy

Elongation A5 min, T (%)	Elongation A5 min, L (%)	Charpy test temp.	KV avg min, T (J)	KV avg min, L (J)
16	18	0°C	37	55

Source: CCS Rules for Materials and Welding (2024), Part 1, Chapter 3, Table 3.4.7.4. Plates over 600 mm wide are impact tested transversely (T value applies). For N/NR and TM plates one impact test is taken from each piece; for QT plates from each individually heat-treated piece. Above 50 mm, impact specimens are taken at t/4 and t/2.

CCS AH550 maximum carbon equivalent (plates)

Delivery condition	Ceq t ≤ 50 mm	Ceq 50 < t ≤ 100 mm	Ceq 100 < t ≤ 250 mm	CET	Pcm
TM	0.48	0.50	0.54	0.34	0.25
QT	0.56	0.60	0.64	0.36	0.28

Table 3.4.3.4. Ceq = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15; CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40 (H460 and above, at the mill’s option); Pcm may be used for TM and QT steels with C ≤ 0.12%. n/a = not applicable.

CCS AH550 thickness range and delivery condition

CCS AH550 maximum plate thickness by delivery condition

Delivery condition	Max plate thickness (mm)
TM	150
QT	150

Table 3.4.6.2. Thicker plates (N over 250 mm, QT over 150 mm) need special consideration by CCS. Yield and tensile requirements fall in steps above 50 mm and 100 mm, as shown in the table above.

CCS AH550 equivalent grades

CCS AH550 equivalent grades of other classification societies

Standard / society	Equivalent grade
IACS UR W16	AH550
ABS	AB/AQ56
DNV	VL A550
LR	LR AH55
ASTM A131	no equivalent (A131 stops at the 40 strength level)

The IACS member societies use the same unified requirements, so these grades match in chemistry and properties. A plate still needs the certificate of the vessel’s own class society; one plate can carry dual or multiple class certification only when each society’s surveyor witnesses the tests.

CCS AH550 FAQ

Is CCS A550 the same as CCS AH550?

Yes. CCS lists the grade as AH550; A550 is a common shorthand for the same steel.

What is the yield strength of CCS AH550?

Minimum 550 MPa up to 50 mm, 530 MPa for 50–100 mm and 490 MPa for 100–250 mm. Tensile strength is 640–820 MPa (up to 100 mm).

What is the impact test temperature of CCS AH550?

0°C, with a minimum average of 37 J transverse or 55 J longitudinal.

What is CCS AH550 equivalent to?

AH550 in IACS UR W16, ABS AB/AQ56, DNV VL A550 and LR AH55. ASTM A131 has no grade at this strength.

How is CCS AH550 supplied?

TM (including TM with accelerated cooling or direct quenching and tempering) or QT. The chemistry and carbon-equivalent limits depend on the delivery condition.

What is the maximum thickness of CCS AH550 plate?

Up to 150 mm in TM or QT condition; thicker plates need special consideration by CCS.

What is the CEV of CCS AH550?

Ceq maximum for plates up to 50 mm is 0.48% (TM), 0.56% (QT). Higher limits apply to thicker plates.

What is the difference between CCS AH550 and the A, D, E and F grades of the same strength?

The strength requirements are identical; only the Charpy test temperature changes (0, −20, −40 or −60°C), and E/F grades have tighter P and S limits.

Equivalent steel grade of CCS/A550
DNV	GL	LR	BV	ABS	NK	KR	RINA
NV A550	GL-A550	LR/AH55	BV/A550	ABS/AQ56	K A56	R A56	RI/A550

If you need more stock steel plates in shipbuilding steel plate, please click warehouse sizes.

Related steel grades: CCS/A500, CCS/AH36, CCS/EH32,CCS/D

 

CCS Steel Plate Grade
General Strength	CCS/A	CCS/B	CCS/D	CCS/E
High Strength	CCS/A32	CCS/D32	CCS/E32	CCS/F32
	CCS/A36	CCS/D36	CCS/E36	CCS/F36
	CCS/A40	CCS/D40	CCS/E40	CCS/F40
Extra Strength	CCS/A420	CCS/D420	CCS/E420	CCS/F420
	CCS/A460	CCS/D460	CCS/E460	CCS/F460
	CCS/A500	CCS/D500	CCS/E500	CCS/F500
	CCS/A550	CCS/D550	CCS/E550	CCS/F550
	CCS/A620	CCS/D620	CCS/E620	CCS/F620
	CCS/A690	CCS/D690	CCS/E690	CCS/F690