What are difference between LR DH40 and LR DH42 steel plate？

Dec 19, 2025 Leave a message

LR DH40 and LR DH42 are grades of high-strength, low-alloy (HSLA) steel plates used primarily in shipbuilding, with the main difference being their yield strength and potentially slight variations in composition and impact toughness, where the '42' signifies a higher strength level (around 420 MPa minimum yield) than the '40' (around 400 MPa), both meeting Lloyd's Register (LR) specifications for marine applications.

Chemical Composition

LR DH40 high Strength Chemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	Al	N
LR DH40	0.18	0.05	0.9-1.6	0.035	0.035	0.015
	Nb	V	Ti	Cu	Cr	Ni	Mo
	0.02-0.05	0.03-0.10	0.02	0.35	0.20	0.40	0.08

LR DH42 extra high Strength Chemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	Al	N
LR DH42	0.20	0.55	1.70	0.030	0.030	0.015	0.020
	Nb	V	Ti	Cu	Cr	Ni	Mo
	0.02-0.05	0.03-0.10	0.02

Mechanical Property

LR DH40 high strength property
Grade		Mechanical Property			Charpy V Impact Test
Grade	Thickness	Yield	Tensile	Elongation	Degree	Energy 1	Energy 2
LR DH40	mm	Min Mpa	Mpa	Min %	-20	J	J
	t≤50	390	510-650	20%		26	39
	50＜t≤70	390	510-650	20%		31	46
	70＜t≤100	390	510-650	20%		37	55
Note: Energy 1 is transverse impact test, Energy 2 is longitudinal

LR DH42 extra high strength property
Grade		Mechanical Property			Charpy V Impact Test
Grade	Thickness	Yield	Tensile	Elongation	Degree	Energy 1	Energy 2
LR DH42	mm	Min Mpa	Mpa	Min %	-20	J	J
	t≤50	420	530-680	20%		28	42
	50＜t≤70	420	530-680	20%		28	42
	70＜t≤100	420	530-680	20%		28	42
Note: Energy 1 is transverse impact test, Energy 2 is longitudinal

LR: Denotes compliance with Lloyd's Register (LR), a major classification society for marine structures.

DH: Indicates a specific strength grade for hull construction, generally meaning high tensile strength.

40 vs. 42: This number refers to the minimum yield strength in megapascals (MPa).

LR DH40: Minimum yield strength of approximately 400 MPa.

LR DH42: Minimum yield strength of approximately 420 MPa.

In essence: DH42 is a stronger grade of steel than DH40, offering slightly better mechanical properties, making it suitable for areas requiring higher strength within shipbuilding standards.