KR/R A40|KR A40 STEEL PLATE

KR A40 steel plate, also written as RA40, R A40, KR Grade A40 or market name AH40, is the higher-strength hull structural steel of Korean Register (KR) Rules for the Classification of Steel Ships (IACS UR W11 higher-strength family) with 390 MPa minimum yield, 510-650 MPa tensile strength and Charpy V-notch toughness at 0°C [32°F]. In the grade name, "A" is the toughness class, and "40" refers to the strength level (historically about 40 kgf/mm²); KR mill certificates commonly use the R prefix (RA40), while AH40 is the common IACS market name with "H" for higher strength. Gangsteel, a steel plate exporter, supplies KR A40 / RA40 plates cut to size for shipbuilding, offshore platforms and marine structures.

Data source: Per IACS UR W11 (ordinary/higher-strength hull structural steel) as adopted in KR Class hull structural steel rules. Official mill/certificate grade is typically RA40 (R A40); KR A40 and AH40 name the same class on this site. Verify the current KR Class edition before ordering.

KR A40 / RA40 Chemical Composition (Heat Analysis)

 

Element	C	Mn	Si	P	S	Al (acid sol.)
KR A40 / RA40, %	0.18 max	0.90-1.60	0.10-0.50	0.035 max	0.035 max	0.015 min
Element	Nb	V	Ti	Cu	Cr	Ni / Mo
KR A40 / RA40, %	0.02-0.05	0.05-0.10	0.02 max	0.35 max	0.20 max	0.40 max / 0.08 max

Per IACS UR W11 / Korean Register (KR) hull structural steel rules (higher-strength grades). Nb, V and Al grain-refining elements may be used singly or in combination; when used in combination the individual minima do not apply. Where acid-soluble Al is not less than 0.015%, the Si minimum does not apply. Carbon equivalent: Ceq = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 (%).

Product Analysis (Check Analysis)

 

IACS UR W11 / KR Class rules do not separately tabulate product (check) analysis limits for higher-strength grades. When product analysis is required, the finished plate shall meet the heat limits subject to ASTM A6/A6M Table A permitted variations (same practice as other IACS societies).

Element	Heat analysis limit	Product analysis (heat ± A6)
C	0.18 max	0.22 max
Mn	0.90-1.60	0.81–1.72
Si	0.10-0.50	0.04–0.56
P	0.035 max	0.045 max
S	0.035 max	0.045 max
Al (acid sol.)	0.015 min	no A6 Table A tolerance; product value not tabulated
Nb	0.02-0.05	0.010–0.060
V	0.05-0.10	0.040–0.110
Ti	0.02 max	0.03 max
Cu	0.35 max	0.38 max
Cr	0.20 max	0.24 max
Ni	0.40 max	0.43 max
Mo	0.08 max	0.09 max

Per IACS UR W11 / KR Class hull structural steel rules. Product analysis applies only when specified; for a range, results may not vary both above and below it.

KR A40 / RA40 Mechanical Properties

 

Grade	Yield strength, min	Tensile strength	Elongation, min
KR A40 (RA40)	390 MPa [57 ksi]	510-650 MPa [74-94 ksi]	20%

Per IACS UR W11 / KR Class hull structural steel rules. Yield and tensile values apply for the full thickness range covered by the grade (typically up to 100 mm for these ship plates).

Charpy V-Notch Impact Requirements (0°C [32°F])

 

Thickness	Test temperature	Longitudinal, avg min	Transverse, avg min
t≤50 mm	0°C [32°F]	39 J	26 J
50<t≤70 mm	0°C [32°F]	46 J	31 J
70<t≤100 mm	0°C [32°F]	55 J	37 J

Per IACS UR W11 / KR Class hull structural steel rules. Average of three full-size Charpy V-notch specimens; not more than one value below the average and none below 70% of it. Longitudinal values shown; transverse values apply when required by the rules or purchase order. Thicker plates (above 100 mm) may be supplied by agreement with adjusted impact requirements.

Delivery Condition and Deoxidation

Deoxidation: Killed, fine-grain practice. Delivery condition: A-class (R A40 / AH40) grades may be as-rolled, controlled rolled, normalized or TMCP depending on thickness; thicker plates usually N or TMCP. Optional extras by agreement include ultrasonic testing, Z-direction (Z15/Z25/Z35) through-thickness testing and third-party KR survey.

Thickness Coverage

Higher-strength KR A/D/E/F 32/36/40 plates are commonly supplied from about 6 mm to 100 mm thick (up to 150 mm by agreement). Width 1500-4000 mm and length 6000-18000 mm are typical.

Equivalent Steel Grades of KR A40

 

Society / Standard	Equivalent grade
KR (Korean Register)	KR A40 / RA40 (AH40)
LR (Lloyd's Register)	LR AH40 steel plate
ABS	ABS AH40 steel plate
CCS	CCS AH40 steel plate
GL	GL AH40 steel plate
DNV	DNV A40 steel plate
BV	BV AH40 steel plate
NK	NK A40 steel plate
RINA	RINA AH40 steel plate

IACS member societies harmonize ordinary and higher-strength hull grades under UR W11; dual certification (for example KR + ABS, or KR + ASTM A131) is common when ordered that way.

FAQ about KR A40 / RA40 Steel Plate

What is KR A40 (RA40) steel plate?

It is a higher-strength hull structural steel under Korean Register (KR) Rules for the Classification of Steel Ships (IACS UR W11), with 390 MPa minimum yield, 510-650 MPa tensile strength and Charpy toughness at 0°C [32°F]. The mill certificate grade is typically RA40 (R A40); KR A40 and market name AH40 refer to the same strength/toughness class.

What does KR A40 / RA40 / AH40 stand for?

KR is Korean Register. The R prefix on the mill grade (RA40 / R A40) is the KR designation. The letter A is the toughness class (Charpy at 0°C [32°F]), and 40 is the strength level (historically about 40 kgf/mm², now 390 MPa min yield). AH40 adds "H" for higher strength in common IACS market naming.

What is the yield strength of KR A40?

Minimum 390 MPa (57 ksi), tensile 510-650 MPa (74-94 ksi), elongation about 20% min.

What is the impact test temperature for KR A40 / RA40?

Charpy V-notch at 0°C [32°F]. Longitudinal average minima are 39 J up to 50 mm, 46 J for 50-70 mm and 55 J for 70-100 mm.

What is the difference between KR A40 and other 40-class grades?

Same 390 MPa strength class. NK A40 (KA40) at 0°C [32°F]; NK D40 (KD40) at -20°C [-4°F]; NK E40 (KE40) at -40°C [-40°F]; NK F40 (KF40) at -60°C [-76°F]. Delivery condition follows the toughness letter rules.

What is the difference between KR A40 and NK A32?

Same A-class toughness (Charpy at 0°C [32°F]). KR A40 is strength class 40 (390 MPa min yield); NK A32 is strength class 32 (315 MPa min yield).

Is KR A40 the same as ABS AH40 or LR AH40?

Requirements are essentially harmonized under IACS UR W11. ABS AH40, LR AH40, DNV A40, BV AH40 and ASTM A131 AH40 (where listed) are counterparts; dual certification is common when ordered with the required surveys.

Is KR A40 weldable?

Yes. Controlled carbon and Ceq give good weldability; preheat may be required for thick sections depending on Ceq and restraint.

What heat treatment is required for KR A40?

A-class (R A40 / AH40) grades may be as-rolled, controlled rolled, normalized or TMCP depending on thickness; thicker plates usually N or TMCP.

What thickness is available for KR A40?

Typical supply is about 6-100 mm thick (up to 150 mm by agreement), 1500-4000 mm wide and 6000-18000 mm long.

Other KR Steel Plate Grades

KR Grade A steel plate | KR Grade B steel plate | KR Grade D steel plate | KR Grade E steel plate | KR A32 steel plate | KR A36 steel plate | KR D36 steel plate | KR D40 steel plate | KR E32 steel plate | KR E36 steel plate | KR E40 steel plate | KR F32 steel plate | KR F36 steel plate | KR F40 steel plate | KR D63 / RD63 steel plate

Equivalent Class Society Grades

KR A40 / RA40 (AH40) corresponds to the same grade under the other IACS member classification societies and ASTM A131: LR AH40 steel plate, ABS AH40 steel plate, CCS AH40 steel plate, GL AH40 steel plate, DNV A40 steel plate, BV AH40 steel plate, NK A40 steel plate, RINA AH40 steel plate.