Difference between S460Q and S690Q steel plate

S460Q and S690Q are ultra-high-strength, quenched and tempered structural steel plates manufactured to the European standard EN 10025-6. The "Q" suffix indicates their Quenched and Tempered delivery condition, which provides a high strength-to-weight ratio. These grades are designed for heavily loaded, critical welded structures where weight reduction is paramount, such as in high-performance mobile cranes, heavy transport vehicles, advanced construction machinery, and some specialized mining equipment.

Key Differences:

The defining distinction is their dramatic difference in strength. S460Q offers a minimum yield strength of 460 MPa, while S690Q provides a substantially higher yield strength of 690 MPa. This 50% strength increase makes S690Q suitable for the most extreme load-bearing applications, enabling maximum structural efficiency.

Achieving this ultra-high strength grade requires a fundamentally different and more stringent alloy design for S690Q. Its chemical composition involves significantly higher levels of carbon, manganese, and critical alloying elements such as chromium, nickel, molybdenum, and often boron. Consequently, S690Q has a vastly higher carbon equivalent (Ceq) and crack susceptibility compared to S460Q. This results in an exponential increase in fabrication difficulty. Welding S690Q is exceptionally complex and restrictive: it demands specially matched, ultra-high-strength welding consumables, meticulous control of preheating (often requiring temperatures above 150°C), extremely low heat input, strict interpass temperature limits, and is almost always followed by mandatory post-weld heat treatment (PWHT) to restore toughness and prevent hydrogen-induced cracking in the heat-affected zone. 

Chemical Composition

Mechanical Property