Difference between LR DH62 and LR DH55 steel plate - Knowledge

LR DH62 and LR DH55 are shipbuilding steel grades (LR = Lloyd's Register), differing mainly in strength and toughness: DH62 offers higher yield strength (around 355 MPa) and better low-temperature impact toughness than DH55 (around 315 MPa), making DH62 suitable for colder climates or higher stress areas, while DH55 is a general-purpose, high-tensile structural steel for less demanding applications. The 'D' denotes deep-cold toughness, 'H' means high tensile, and the numbers (55, 62) relate to minimum yield strength (e.g., 55 ksi/380 MPa, 62 ksi/430 MPa), with DH62 being stronger/tougher.

Chemical Composition

LR DH55 extra high Strength Chemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	Al	N
LR DH55	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

LR DH62 extra high Strength Chemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	Al	N
LR DH62	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 DH55 extra high strength property
Grade		Mechanical Property			Charpy V Impact Test
Grade	Thickness	Yield	Tensile	Elongation	Degree	Energy 1	Energy 2
LR DH55	mm	Min Mpa	Mpa	Min %	-20	J	J
	t≤50	550	670-830	18%		37	55
	50＜t≤70	550	670-830	18%		37	55
	70＜t≤100	550	670-830	18%		37	55
Note: Energy 1 is transverse impact test, Energy 2 is longitudinal

LR DH62 extra high strength property
Grade		Mechanical Property			Charpy V Impact Test
Grade	Thickness	Yield	Tensile	Elongation	Degree	Energy 1	Energy 2
LR DH62	mm	Min Mpa	Mpa	Min %	-20	J	J
	t≤50	620	720-890	17%		41	62
	50＜t≤70	620	720-890	17%		41	62
	70＜t≤100	620	720-890	17%		41	62
Note: Energy 1 is transverse impact test, Energy 2 is longitudinal

LR DH55 Steel

Strength: Good high tensile strength (Yield ~315 MPa / 45 ksi).

Toughness: Excellent weldability and formability.

Application: General structural uses in shipbuilding, hull structures, and general construction.

LR DH62 Steel

Strength: Higher yield strength (Yield ~355 MPa / 51 ksi) than DH55.

Toughness: Superior low-temperature impact toughness (Charpy V-notch).

Application: Areas requiring higher strength or better performance in colder conditions, such as critical hull sections.

Key Difference Summary

Strength: DH62 > DH55.

Toughness: DH62 > DH55 (especially at low temps).

Use: DH62 for tougher, colder environments; DH55 for general needs