LR Grade A Steel Plate | Grade A Shipbuilding Steel Plate

LR Grade A steel plate, also called LR/A, LR/A, Lloyd's Register Grade A or simply Grade A ship steel plate, is the basic ordinary (general) strength hull structural steel under Lloyd's Register Rules for Ships (IACS UR W11 ordinary-strength family). All four ordinary grades A, B, D and E share 235 MPa minimum yield and 400-520 MPa tensile strength; the grade letter sets the toughness requirement. Gangsteel, a steel plate exporter, supplies LR Grade A general strength steel plate for ship hulls, decks, bulkheads, barges and general marine structures.

Data source: Per IACS UR W11 (ordinary/higher-strength hull structural steel) as adopted in Lloyd's Register Rules for Ships. Verify the current LR edition before ordering.

LR/A Chemical Composition (Heat Analysis)

 

Grade	C, max	Mn	Si	P, max	S, max	C + Mn/6, max
LR/A	0.21	≥2.5×C	0.50	0.035	0.035	0.40

Per IACS UR W11 / LR Rules for Ships (ordinary-strength hull structural steel). Ni, Cr, Mo and Cu are to be determined and reported. Carbon equivalent: Ceq = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 (%); crack sensitivity: Pcm = C + Si/30 + Mn/20 + Cu/20 + Ni/60 + Cr/20 + Mo/15 + V/10 + 5B (%). 依据 IACS UR W11 / LR Rules for Ships.

Product Analysis (Check Analysis)

 

IACS UR W11 / LR Rules for Ships do not separately tabulate product (check) analysis limits for ordinary-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 ABS MW Pt2 referencing ASTM A6 chemical tolerances).

Element	Heat analysis limit	Product analysis (heat ± A6)
C	0.21 max	0.25 max (heat + A6 over-max)
Mn	≥2.5×C	min-only; no A6 product band keyed to upper limit
Si	0.50 max	0.56 max
P	0.035 max	0.045 max
S	0.035 max	0.045 max
C + Mn/6	0.40 max	calculated from heat analysis
Ni, Cr, Mo, Cu	to be determined and reported	-

依据 IACS UR W11 / LR Rules for Ships. Product analysis applies only when specified; for a range, results may not vary both above and below it.

LR/A Mechanical Properties

 

Grade	Yield strength, min	Tensile strength	Elongation, min
LR/A	235 MPa [34 ksi]	400-520 MPa [58-75 ksi]	22%

Per IACS UR W11 / LR Rules for Ships. 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 (+20°C when required)

 

Thickness	Test temperature	Longitudinal, avg min	Transverse, avg min
t≤50 mm	Not required	-	-
50<t≤70 mm	+20°C [68°F]	34 J	24 J
70<t≤100 mm	+20°C [68°F]	41 J	27 J

Per IACS UR W11 / LR Rules for Ships. Grade A plates t ≤ 50 mm normally have no Charpy requirement; testing at +20°C applies above 50 mm.

Delivery Condition and Deoxidation

Deoxidation: Killed or semi-killed (t≤50 mm); killed (t>50 mm). Delivery condition: As-rolled (AR), controlled rolled (CR), normalized (N) or TMCP depending on thickness and purchaser requirements. Normalized or TMCP is common above 50 mm. Optional extras by agreement include ultrasonic testing, Z-direction (Z15/Z25/Z35) through-thickness testing and third-party LR survey.

Thickness Coverage

Ordinary-strength LR grades are commonly supplied from about 6 mm to 100 mm thick (wider/thicker by agreement with LR). Width 1500-4000 mm and length 6000-18000 mm are typical mill ranges.

Equivalent Steel Grades of LR/A

 

Society / Standard	Equivalent grade
LR (Lloyd's Register)	LR/A
ABS	ABS A steel plate (AB/A)
CCS	CCS A steel plate
ASTM A131/A131M	ASTM A131 Grade A steel plate
DNV	NV A
GL	GL-A
BV	BV/A
NK / KR / RINA	K A / R A / RI/A

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

FAQ about LR Grade A Steel Plate

What is LR Grade A steel plate?

It is an ordinary-strength hull structural steel under Lloyd's Register Rules for Ships (IACS UR W11 family), with 235 MPa minimum yield and 400-520 MPa tensile strength.

What does the letter A mean in LR Grade A?

Grade A is the basic ordinary hull grade; Charpy impact is normally not required up to 50 mm and is tested at +20°C above that.

What is the yield strength of LR Grade A?

Minimum 235 MPa (34 ksi), with tensile strength 400-520 MPa (58-75 ksi) and elongation about 22% min.

Does LR Grade A require impact testing?

Not for t ≤ 50 mm. Above 50 mm, Charpy V-notch at +20°C applies: 34 J longitudinal / 24 J transverse for 50-70 mm, and 41 J / 27 J for 70-100 mm.

Is LR Grade A the same as ABS Grade A or ASTM A131 Grade A?

Requirements are essentially harmonized under IACS UR W11. ABS and ASTM A131 Grade A are counterparts; plates can be dual-certified when ordered with the required society survey and marking.

Is LR Grade A weldable?

Yes. Low carbon and controlled carbon equivalent give good weldability with standard shipyard procedures; preheat depends on thickness, Ceq and restraint.

What thickness is available for LR Grade A?

Typical mill supply is about 6-100 mm thick, 1500-4000 mm wide and 6000-18000 mm long; thicker or wider plates by agreement with LR.

What is the difference between LR Grade A and Grade B?

Both have the same strength. Grade B has a higher Mn minimum (0.80% vs 2.5×C), tighter Si, and Charpy at 0°C, while Grade A usually needs no impact test up to 50 mm.

Other LR Steel Plate Grades

LR Grade B steel plate | LR Grade D steel plate | LR Grade E steel plate | LR AH32 steel plate | LR AH36 steel plate | LR AH40 steel plate | LR DH32 steel plate | LR DH36 steel plate | LR DH40 steel plate | LR EH32 steel plate | LR EH36 steel plate | LR EH40 steel plate | LR FH32 steel plate | LR FH36 steel plate | LR FH40 steel plate

Equivalent Class Society Grades

LR Grade A corresponds to the same grade under the other IACS member classification societies and ASTM A131: CCS Grade A steel plate, ABS Grade A steel plate, ASTM A131 Grade A steel plate, GL Grade A steel plate, DNV Grade A steel plate, NK Grade A steel plate, RINA Grade A steel plate.