Difference between S690Q and S690QL steel plate

The main difference between S690Q and S690QL steel plates lies in their guaranteed impact toughness testing temperature: S690Q requires toughness at -20°C, while S690QL requires it at a lower temperature of -40°C, indicating S690QL is better suited for colder conditions, both being high-strength quenched and tempered steels with 690 MPa minimum yield strength.

Chemical Composition

S690Q Chemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	N	B	Cr
S690 Q	0.20	0.80	1.70	0.020-0.025	0.010-0.015	0.015	0.005	1.50
	Cu	Mo	Nb	Ni	Ti	V	Zr
	0.50	0.70	0.06	2.0	0.05	0.12	0.15

Carbon Equivalent: Ceq = 【C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15】%

S690QL Chemical Composition

C	Si	Mn	P	S	B	Cr	Cu	Mo	N	Nb	Ni	Ti	V	Zr
0.20	0.80	1.70	0.020	0.010	0.005	1.50	0.50	0.70	0.015	0.06	2.0	0.05	0.12	0.15

Mechanical Property

Grade	S690Q Mechanical Property
Grade	Thickness	Yield	Tensile	Elongation	Min Impact Energy
S690 Q	mm	Min Mpa	Mpa	Min %	-20	30J
	3<t≦50	690	770-940	14	-20	30J
	50<t≦100	650	760-930	14	-20	30J
	100<t≦150	630	710-900	14	-20	30J

S690QL Mechanical Property

Plate thickness mm	Yield strength Reh (MPA)	Tensile strength Rm (MPA)	Elongation A5 % minimum	Impact strength J, minimum
3mm to 50mm	690	770 – 940	14	30 @ -40º C
50mm to 100mm	650	760 – 930	14	30 @ -40º C
100mm to 150mm	630	710 – 900	14	30 @ -40º C

Key Distinctions:

S690Q: High-strength structural steel with minimum yield strength of 690 MPa, guaranteed impact toughness at -20°C.

S690QL: Same strength (690 MPa) but with enhanced low-temperature performance, guaranteed impact toughness at -40°C.

Key Characteristics (Both Grades):

Strength: Minimum yield strength (ReH) of 690 MPa for typical thicknesses.

Heat Treatment: Both undergo quenching and tempering (Q+T).

Applications: Used in heavy vehicles, cranes, bridges, and other load-bearing structures where lightweight and strength are crucial.

In essence, the 'L' in S690QL signifies enhanced suitability for colder environments compared to S690Q.