S690QL Steel

S690QL steel is a quenched and tempered, high-strength structural steel plate supplied to EN 10025-6. It is used by engineers, fabricators and manufacturers producing cranes, lifting equipment, heavy machinery and load-bearing structures where lower strength steel may add unnecessary weight or lack the required toughness. At P&D Northern Steels, we supply this grade from our Oldham base with in-house cutting to size and UK-wide delivery. We have supported steel users since 1972, giving customers experienced guidance, dependable service and straightforward access to the plate they need.

Contact us with your required thickness, dimensions and quantity to discuss availability and your project requirements.

Understanding the S690QL Designation

Each part of the grade name identifies an important material characteristic:

• S identifies it as structural steel.
• 690 refers to a minimum yield strength of 690 MPa for plate up to 50 mm thick.
• Q means the material is supplied in a quenched and tempered condition.
• L confirms specified impact properties at temperatures down to minus 40°C.

The minimum yield strength reduces for thicker plate in accordance with the standard. Engineers should check the complete mechanical properties for the thickness being considered rather than applying the 690 MPa figure to every plate.

Quenching and tempering creates a fine grain structure that combines high strength with toughness. This gives designers an alternative to thicker sections of lower strength structural steel where component weight, available space or load capacity creates a limitation.

High Strength Without Unnecessary Weight

The main advantage of this material is its ability to support heavily loaded components without relying on excessively heavy sections. Subject to appropriate engineering calculations, its strength can allow thinner or lighter designs than may be possible with conventional structural steel.

This can be particularly useful in mobile equipment. Reducing the weight of a crane boom, trailer or machinery component may improve payload capacity and make the wider assembly more efficient. In fixed structures, smaller sections may help designers work within tight dimensions while maintaining the required load-bearing performance.

Higher strength does not mean every component can automatically be made thinner. Deflection, fatigue, buckling, connections and local stresses must also be considered. Any reduction in thickness should be approved by the responsible engineer.

S690QL Steel Properties

S690QL belongs to the wider family of high-strength steel grades used in demanding structural and engineering applications. Its defining characteristics include:

1. High yield strength: The minimum yield strength of 690 MPa for plate up to 50 mm supports components exposed to substantial loads.
2. Low temperature toughness: The QL designation provides specified impact performance at minus 40°C.
3. Heat-treated condition: Quenching and tempering develops the required balance of strength and toughness.
4. Weight reduction potential: Its strength can support lighter designs when confirmed through suitable calculations.
5. Weldability: The plate can be welded using an appropriate procedure, consumables and heat controls.
6. Formability: Bending and forming are possible with suitable equipment, working methods and bend radii.

This grade is not inherently weathering or corrosion resistant. Plate exposed to rain, saltwater, chemicals or other aggressive conditions may require an appropriate primer, paint or protective coating.

Performance in Low Temperature Conditions

Steel can become more vulnerable to brittle fracture as temperatures fall. This makes impact properties an important consideration for outdoor structures, offshore equipment and machinery operating in cold environments.

The wider S690Q, S690QL and S690QL1 steel plate family provides specified impact properties at different temperatures. S690Q is specified at minus 20°C, while the L designation extends this to minus 40°C. S690QL1 extends the specified temperature further to minus 60°C. The correct grade depends on the lowest design temperature, operating conditions and relevant project standard.

Common Uses for S690QL Plate

This material is suited to components where high loads, controlled weight and dependable toughness must work together. Typical applications include:

• Mobile crane booms and lifting arms
• Earthmoving and excavation equipment
• Load-bearing parts for heavy plant
• Truck chassis and specialist trailers
• Bridge components and supporting structures
• Drilling and materials handling machinery
• Offshore support structures
• Energy and infrastructure equipment
• Highly stressed industrial frameworks

Within heavy engineering, the grade may be specified only for the parts of an assembly that experience the highest loads or most demanding operating conditions. Other structural grades can then be used where the additional strength is not required.

Welding, Forming and Thermal Cutting

S690QL is weldable, but its high strength and heat treated condition require greater control than standard mild steel. A qualified welding procedure should account for plate thickness, carbon equivalent, joint design, restraint and expected operating conditions.

Fabrication may require low hydrogen consumables, controlled heat input and specific preheating or interpass temperatures. Excessive heat can alter the properties achieved through quenching and tempering. The material certificate, relevant welding standards and manufacturer guidance should therefore be reviewed before work starts.

Cold forming requires suitable machinery and carefully selected bend radii. The plate has greater resistance to forming than a lower strength grade and may produce more springback. Thermal cut edges intended for welding or use in critical areas may also require preparation and inspection in line with the project specification.

Plate Supply and Cutting Support

We supply S690QL steel plate from our Oldham base for projects throughout the UK. Availability can vary according to thickness, plate size and quantity, so customers should discuss specific requirements with our team.

Our in-house gas cutting to size service allows plate to be supplied in dimensions that suit the application. This can reduce waste, limit unnecessary handling and save preparation time in the fabrication workshop.

To help us assess a requirement accurately, please provide:

• Grade and applicable standard
• Required thickness
• Length and width
• Quantity
• Delivery location
• Certification or traceability requirements
• Any project-specific testing requirements

We can discuss arranging other processing services through our external partners where needed.

Certification, Traceability and Testing

Certification requirements should be established before material is selected and processed. Depending on the order and specification, EN 10204 3.1 or 3.2 certification can be supplied where required. Traceability and marking requirements can also be agreed at the enquiry stage.

Where additional material testing or inspection is required, we can discuss arranging this through our sister company or another appropriate approved route. These requirements should be confirmed in advance so that the correct documentation and testing process can be established.

Our quality certificates include ISO 9001:2015 certification for the quality management system supporting our material supply and customer service.

Why Work With P&D Northern Steels?

We are experienced steel stockholders and have supplied steel plate since 1972. We understand the importance of correct specifications, reliable availability and clear communication.

Our customers benefit from:

• More than five decades of steel stockholding experience
• In-house cutting to size
• Support for single plate and larger quantity requirements
• Delivery throughout the UK
• Certification and traceability options where required
• Additional services arranged through external partners

Our team supports fabricators, engineers, contractors and manufacturers that need dependable plate supply and straightforward service.

FAQs

Discuss Your S690QL Steel Requirements

Tell us the thickness, dimensions and quantity you need, along with any cutting, documentation or delivery requirements. Call us on 01706 848811 or contact us online to discuss your project.