Engineering
S355J2+N and Strenx 700E: what the steel grade means for your trailer
Two grades cover most of what a lowbed chassis is made from. Both are structural steels, both are weldable, and the difference between them shows up as payload rather than as anything visible on a finished trailer.
S355J2+N: the structural baseline
S355J2+N is a normalised structural steel with a minimum yield strength of 355 MPa and guaranteed impact toughness at minus 20 degrees Celsius. It is predictable, widely available, and forgiving to weld and repair anywhere in the world.
For the majority of standard lowbeds it is exactly the right material. There is no engineering benefit in upgrading a chassis that is already comfortably within its design envelope.
Strenx 700E: strength that converts into payload
Strenx 700E is a high-strength structural steel with a minimum yield of 700 MPa, roughly double that of S355. In practice that allows thinner sections in the main beams for the same load-bearing capacity.
The result is a chassis that can be up to thirty per cent lighter. Every kilogram saved in the structure is a kilogram of legal payload gained, on every single trip the trailer makes.
Where the upgrade pays for itself
It pays where you are limited by weight rather than by space: heavy machinery transport, multi-axle configurations, and any operation that regularly runs close to its legal axle limits.
It pays much less on trailers that are typically loaded well under capacity, where the extra material cost buys payload that never gets used.
What it demands in return
High-strength steel is less tolerant of poor fabrication. Heat input during welding has to be controlled, preheating and interpass temperatures matter, and field repairs need consumables and procedures matched to the grade.
This is a manufacturing question rather than an operator one, but it is worth asking any supplier how they weld it and how a damaged beam would be repaired.
The practical answer
Use S355J2+N as the default and specify Strenx 700E where the extra payload has a measurable value to your operation. Mixed construction, with high-strength material in the main beams and standard structural steel elsewhere, is common and entirely sound engineering.
