Difference between S690QL1 and S890QL1

S690QL1 and S890QL1 are ultra-high-strength, quenched and tempered structural steel plates manufactured according to the European standard EN 10025-6. The designation indicates their minimum yield strength (690 MPa and 890 MPa respectively) and the "QL1" suffix specifies their delivery condition: Quenched (Q) and Tempered (T) with longitudinal (L1) impact toughness testing. These grades are engineered for highly stressed components in demanding applications such as heavy construction machinery (crane booms, truck chassis), mining equipment, and advanced structural frameworks where extreme strength-to-weight ratio and good toughness are critical.

Key Differences:

The primary distinction is their strength level. S690QL1 offers a minimum yield strength of 690 MPa, while S890QL1 provides a substantially higher yield strength of 890 MPa (and a correspondingly higher tensile strength). This makes S890QL1 suitable for the most extreme load-bearing applications, enabling maximum weight reduction in design.

Achieving this higher strength grade requires a more precise and stringent alloy composition, typically with higher levels of carbon, manganese, and micro-alloying elements like chromium, nickel, molybdenum, and boron during the quenching and tempering process. Consequently, S890QL1 has a significantly higher carbon equivalent (Ceq) and crack susceptibility compared to S690QL1. This results in exponentially greater challenges in fabrication, especially welding. Welding S890QL1 demands extremely strict procedures: the use of specially matched, ultra-high-strength consumables, meticulous control of preheating (often above 150°C) and interpass temperatures, very low heat input, and almost always mandatory post-weld heat treatment (PWHT) to restore toughness in the heat-affected zone and prevent hydrogen-induced cracking. 

Chemical Composition

Mechanical Property