Difference between LR DH40 and LR DH42 steel plate

Dec 18, 2025 Leave a message

The main difference between LR DH40 and LR DH42 steel plates lies in their strength and toughness levels, with "D" indicating high strength, "H" signifying heat treatment, and the number (40 vs. 42) pointing to their minimum yield strength (around 390 MPa vs. 420 MPa) and enhanced low-temperature impact properties, making DH42 suitable for colder, harsher marine conditions than DH40, while both offer excellent weldability for shipbuilding.

LR: Lloyd's Register (the classification society specifying the standard).

D: High Strength Steel.

H: Heat Treated.

40 / 42: Indicates the minimum yield strength (in kgf/mm²) and corresponding toughness.

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

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