Difference between S690Q and S960Q - Knowledge

S690Q and S960Q are ultra-high-strength, quenched and tempered structural steel plates manufactured to the European standard EN 10025-6. The "Q" suffix designates their Quenched and Tempered delivery condition. These grades represent the premium tier of structural steels, engineered for the most extreme applications where maximizing strength-to-weight ratio and reducing structural mass are critical, such as in advanced mobile crane booms, heavy-haul transport frames, high-performance military vehicles, and specialized components for offshore and mining where payload or dynamic load capacity is paramount.

Key Differences:

The primary distinction is their ultimate strength level. S690Q offers a minimum yield strength of 690 MPa, while S960Q provides a substantially higher yield strength of 960 MPa. This represents nearly a 40% increase, positioning S960Q at the forefront of commercially available high-strength steel, enabling the greatest potential for weight reduction and performance.

Achieving this extreme strength requires a highly advanced and precisely controlled alloy design for S960Q. Its chemical composition involves significantly higher levels of carbon, manganese, and critical alloying elements such as chromium, nickel, molybdenum, and boron, processed under stringent quenching and tempering parameters. Consequently, S960Q has a dramatically higher carbon equivalent (Ceq) and crack susceptibility compared to S690Q. This translates to exponentially greater fabrication challenges. Welding S960Q is exceptionally restrictive and complex: it demands specially developed, ultra-high-strength welding consumables with precise matching, meticulous control of very high preheating temperatures (often above 200°C), extremely low and controlled heat input, strict interpass temperature windows, and is virtually always followed by mandatory, carefully specified post-weld heat treatment (PWHT) to mitigate hydrogen cracking and attempt to restore toughness in the inevitably softened heat-affected zone.

Chemical Composition

S690QChemical 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

S960QChemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	N	B	Cr
S960 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

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

Grade	S960Q Mechanical Property
Grade	Thickness	Yield	Tensile	Elongation	Min Impact Energy
S960 Q	mm	Min Mpa	Mpa	Min %	-20	30J
	3<t≦50	960	980-1150	10	-20	30J
	50<t≦100	910	920-1000	10	-20	30J
	100<t≦150	860	870-980	10	-20	30J