S690QL / 1.8928 high-strength structural steel

What S690QL is

S690QL is a weldable structural steel in the 690 MPa class to EN 10025-6. The strength comes from the mill quenching and tempering the plate – hence the Q in the designation. L means that the impact toughness is documented at −40 °C. It is a structural steel and not a quenched and tempered steel for shafts: it is bought on strength class, thickness and impact toughness class, and it is not treated like S355 in the workshop.

Typical applications

Cranes, booms and slender structures where S355 becomes too thick. The point is the weight: the same load can be carried with thinner plate when the yield strength is almost twice that of S355. Welded structures, plate and bar where 690 MPa is what the calculation requires.

• Cranes and booms
• Slender steel structures and sections
• Plate and bar for welded structures with high demands on weight

Delivery condition and dimensions

S690QL is supplied quenched and tempered from the mill to EN 10025-6. We source the material from European partners as plate, flat bar and round bar, cut to your dimensions and ship the certificate with it. From a single cut piece to full plates – no minimum charge, so you do not have to buy a full format to get what you are missing. State thickness or cross-section, format or length, quantity and which impact toughness class the certificate is to document. Stock status is confirmed on enquiry.

Heat treatment and mechanical properties

The condition is the mill's: hardening and tempering are done before the plate leaves the mill, and that is what the certificate documents. The nominal yield strength is 690 MPa, with impact toughness at −40 °C for QL. The steel should therefore not be re-heat-treated by the customer, and the heat input during cutting and welding is kept under control. If the structure requires impact toughness at −60 °C, it is S690QL1 / 1.8988, the same 690 MPa class with a colder certificate. The analysis to EN 10025-6 is a set of ceiling values, not a fixed recipe; the exact alloying is the mill's.

Machining

Cutting to size with controlled heat input. Thermal cutting, bending and other cold forming follow a stricter procedure than for S355, because the strength lies in the heat treatment. We cut flat bar and round bar on the band saw and cut plate to drawing. State the cutting method and any requirements for edges on the enquiry.

Welding

S690QL is welded, but with a stricter procedure than S355 and with controlled heat input. It is not S355 workshop welding. The welding procedure must be in place before the material is specified – that is the price of the weight you save.

Certificates and documentation

S690QL can be supplied with a material certificate to EN 10204, depending on producer, dimension and the requirements specified for the delivery. On welded structures it is the analysis, the strength class and – where the standard requires it – the impact toughness that the certificate must show. EN 10204 3.1 can be supplied on a wide range of our materials, and 3.2 is ordered when the project requires a third party. The certificate carries the name the mill has issued.

Designations

S690QL is the EN designation to EN 10025-6; the Werkstoffnummer is 1.8928. S stands for structural steel, 690 for the nominal yield strength in MPa, Q for quenched and tempered and L for impact toughness at −40 °C. S690QL1 / 1.8988 is the same class with impact toughness at −60 °C. Drawings that specify a trade name for the 690 class we translate into the W.Nr. the mill can carry on the certificate.

• S690QL / 1.8928 – EN 10025-6, impact toughness at −40 °C
• S690QL1 / 1.8988 – same 690 MPa class, impact toughness at −60 °C
• S890QL / 1.8983 and S960QL / 1.8933 – the next steps up in yield strength

Limits and alternatives

It is not a quenched and tempered steel for shafts – if the part is to be hardened, it is 42CrMo4 or 34CrNiMo6. Do not treat it like S355 in the workshop. S690QL1 when −60 °C is to be documented. S890QL and S960QL when the yield strength has to go further up and the section even slimmer. S460NL when S355 becomes too thick but S690QL is more than the job requires. S355J2 downwards when 355 MPa is sufficient and welding is to be straightforward.