NK/K F36|NK F36 STEEL PLATE

NK F36 steel plate, also written as KF36, K F36, ClassNK F36, NK Grade F36 or market name FH36, is the higher-strength hull structural steel of ClassNK (Nippon Kaiji Kyokai) Rules for the Survey and Construction of Steel Ships (IACS UR W11 higher-strength family) with 355 MPa minimum yield, 490-620 MPa tensile strength and Charpy V-notch toughness at -60°C [-76°F]. In the grade name, "F" is the toughness class, and "36" refers to the strength level (historically about 36 kgf/mm²); ClassNK mill certificates commonly use the K prefix (KF36), while FH36 is the common IACS market name with "H" for higher strength. Gangsteel, a steel plate exporter, supplies NK F36 / KF36 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 ClassNK hull structural steel rules. Official mill/certificate grade is typically KF36 (K F36); NK F36 and FH36 name the same class on this site. Verify the current ClassNK edition before ordering.

NK F36 / KF36 Chemical Composition (Heat Analysis)

 

Element	C	Mn	Si	P	S	Al (acid sol.)
NK F36 / KF36, %	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
NK F36 / KF36, %	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 / ClassNK (NK) 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 / ClassNK 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 / ClassNK hull structural steel rules. Product analysis applies only when specified; for a range, results may not vary both above and below it.

NK F36 / KF36 Mechanical Properties

 

Grade	Yield strength, min	Tensile strength	Elongation, min
NK F36 (KF36)	355 MPa [51 ksi]	490-620 MPa [71-90 ksi]	21%

Per IACS UR W11 / ClassNK 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 (-60°C [-76°F])

 

Thickness	Test temperature	Longitudinal, avg min	Transverse, avg min
t≤50 mm	-60°C [-76°F]	34 J	24 J
50<t≤70 mm	-60°C [-76°F]	41 J	27 J
70<t≤100 mm	-60°C [-76°F]	50 J	34 J

Per IACS UR W11 / ClassNK 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: F-class (K F36 / FH36) grades are supplied normalized or TMCP (often with Ni alloying for -60°C toughness); as-rolled delivery is not permitted. Optional extras by agreement include ultrasonic testing, Z-direction (Z15/Z25/Z35) through-thickness testing and third-party ClassNK survey.

Thickness Coverage

Higher-strength NK 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 NK F36

 

Society / Standard	Equivalent grade
NK (ClassNK)	NK F36 / KF36 (FH36)
LR (Lloyd's Register)	LR FH36 steel plate
ABS	ABS FH36 steel plate
CCS	CCS FH36 steel plate
ASTM A131/A131M	ASTM A131 FH36 steel plate
GL	GL FH36 steel plate
DNV	DNV F36 steel plate
BV	BV FH36 steel plate
KR	KR F36 steel plate
RINA	RINA FH36 steel plate

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

FAQ about NK F36 / KF36 Steel Plate

What is NK F36 (KF36) steel plate?

It is a higher-strength hull structural steel under ClassNK (Nippon Kaiji Kyokai) Rules for the Survey and Construction of Steel Ships (IACS UR W11), with 355 MPa minimum yield, 490-620 MPa tensile strength and Charpy toughness at -60°C [-76°F]. The mill certificate grade is typically KF36 (K F36); NK F36 and market name FH36 refer to the same strength/toughness class.

What does NK F36 / KF36 / FH36 stand for?

NK (ClassNK) is Nippon Kaiji Kyokai. The K prefix on the mill grade (KF36) is the ClassNK designation. The letter F is the toughness class (Charpy at -60°C [-76°F]), and 36 is the strength level (historically about 36 kgf/mm², now 355 MPa min yield). FH36 adds "H" for higher strength in common IACS market naming.

What is the yield strength of NK F36?

Minimum 355 MPa (51 ksi), tensile 490-620 MPa (71-90 ksi), elongation about 21% min.

What is the impact test temperature for NK F36 / KF36?

Charpy V-notch at -60°C [-76°F]. Longitudinal average minima are 34 J up to 50 mm, 41 J for 50-70 mm and 50 J for 70-100 mm.

What is the difference between NK F36 and other 36-class grades?

Same 355 MPa strength class. NK A36 (KA36) at 0°C [32°F]; NK D36 (KD36) at -20°C [-4°F]; NK E36 (KE36) at -40°C [-40°F]; NK F36 (KF36) at -60°C [-76°F]. Delivery condition follows the toughness letter rules.

What is the difference between NK F36 and NK F32?

Same F-class toughness (Charpy at -60°C [-76°F]). NK F36 is strength class 36 (355 MPa min yield); NK F32 is strength class 32 (315 MPa min yield).

Is NK F36 the same as ABS FH36 or LR FH36?

Requirements are essentially harmonized under IACS UR W11. ABS FH36, LR FH36, DNV F36, BV FH36 and ASTM A131 FH36 (where listed) are counterparts; dual certification is common when ordered with the required surveys.

Is NK F36 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 NK F36?

F-class (K F36 / FH36) grades are supplied normalized or TMCP (often with Ni alloying for -60°C toughness); as-rolled delivery is not permitted.

What thickness is available for NK F36?

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

Other NK Steel Plate Grades

NK Grade A steel plate | NK Grade B steel plate | NK Grade D steel plate | NK Grade E steel plate | NK A32 steel plate | NK A36 steel plate | NK A40 steel plate | NK D32 steel plate | NK D36 steel plate | NK D40 steel plate | NK E32 steel plate | NK E36 steel plate | NK E40 steel plate | NK F32 steel plate | NK F40 steel plate

Equivalent Class Society Grades

NK F36 / KF36 (FH36) corresponds to the same grade under the other IACS member classification societies and ASTM A131: LR FH36 steel plate, ABS FH36 steel plate, CCS FH36 steel plate, ASTM A131 FH36 steel plate, GL FH36 steel plate, DNV F36 steel plate, BV FH36 steel plate, KR F36 steel plate, RINA FH36 steel plate.