Chassis Engineering: S355 Structural Steel vs. Strenx 700E High-Yield Steel
355 MPa or 700 MPa minimum yield strength: how the chassis steel is chosen.
Every STU chassis starts from one of two steels: S355J2+N structural steel, used on most trailers, or Strenx 700E high-yield steel from SSAB, used where tare weight decides the payload.
Structural Yield Strength & Load-Bearing Calculations (355 MPa vs. 700 MPa)
The numbers in the names are minimum yield strengths: 355 MPa for S355J2+N and 700 MPa for Strenx 700E. Yield strength is the stress at which steel starts to deform permanently, so a beam in 700 MPa steel carries the same load with a thinner section. S355J2+N is normalised (+N) and impact-tested at −20 °C (J2), and it can be welded and repaired with standard procedures almost anywhere. Structural calculations are made to EN 1993 (Eurocode 3) for each configuration. Which steel a trailer gets depends on the design: the 6-Car Transporter uses S355J2+N with Strenx 700E as an option, the Multi-Axle Lowbed S355J2+N, S700MC PLUS or S960, and the Reel Cable Roller Trailer Strenx 700MC / S960Q.
Payload Optimisation: Achieving Up to 30% Unladen Tare Weight Reduction
Because a 700 MPa section can be thinner for the same load, a chassis designed in Strenx 700E weighs up to 30% less than the same chassis in S355J2+N. On a trailer limited by its permissible laden mass, such as a car transporter at 32,000 kg, every kilogram taken out of the chassis can be carried as cargo. The saving depends on the design and is calculated for each project. S355J2+N stays the better choice where low material cost and repairs with standard welding consumables matter more than tare weight.
Certified EN ISO 15614 Welding Standards & Quality Inspection
Welding procedures are qualified to EN ISO 15614. High-strength steels need their own procedures to keep their mechanical properties: preheating for plate thicker than 20 mm and a heat input typically limited to 0.8–2.5 kJ/mm. Production runs under an ISO 9001 quality management system in our 3,000 m² plant in Konya: see road certification.