CR550LA - Cold-Rolled Micro-Alloyed Steel according to VDA 239-100

Quality	Standard	Possible coatings
CR550LA	VDA 239-100	UC, EG, GI, GA, AS, ZM

Quality

Testing direction	Yield Point R_e (MPa)	Tensil Strength R_m (MPa)	Elongation type 1 _A50 (in %)	Type 2 A₈₀ (in %)	Type 3 A₅₀ (in %)
L	550 – 670	600 – 780	≥ 11	≥ 11	≥ 12

Mechanical Properties

C %	Si %	Mn %	P %	S %	Al %	Ti %	Nb %	Cu %
≤ 0,14	≤ 0,60	≤ 1,80	≤ 0,030	≤ 0,025	≥ 0,015	≤ 0,15	≤ 0,10	≤ 0,20

Chemical properties

CR550LA is the highest strength grade in the family of cold-rolled micro-alloyed steels according to the VDA 239-100 standard. It represents the absolute pinnacle of performance achievable with conventional cold forming processes. With a minimum yield strength of 550 MPa, CR550LA is intended for components where every bit of additional strength counts to maximize passive safety.
The development of this material is a result of increasing demands for crash safety and presents engineers with new challenges in process and tooling technology. Its application is exclusively limited to the automotive industry, where its unique properties are utilized in specific, highly stressed components.

Properties

The mechanical properties of CR550LA are exceptional. The minimum yield strength (Rp0.2) is an impressive 550 MPa, which means an extremely high resistance to plastic deformation. The minimum tensile strength (Rm) is 600 MPa, ensuring extraordinary load-bearing capacity.
The elongation at break (A80) is a minimum of 11%. It’s important to emphasize that this formability is at the limit of what’s technically feasible. Manufacturing components from CR550LA therefore requires special forming technologies such as roll forming or stamping and bending, as deep drawing processes are hardly possible for complex geometries anymore.
The chemical composition follows the proven principle of low carbon content, supplemented by a high concentration of micro-alloying elements. These ensure a fine grain structure and high precipitation hardening, which are responsible for the extreme strength. Despite its high strength, the material retains excellent weldability, which is crucial for efficient series production.

Applications

Due to its extreme strength, CR550LA is used in the most critical areas of the vehicle body, where maximum stiffness and minimal deformation are paramount. Typical applications include:

Reinforcements in the door structure: Here, the material ensures excellent side impact protection with the lowest possible weight.

Safety-relevant profiles in the roof frame: These profiles are crucial for stability during a rollover.

Special reinforcements in the car body structure: In selected nodes and connections, CR550LA is used to manage local loads and increase the overall structural stiffness.

Seat rails and seatbelt anchorages: These components must withstand extreme forces in a crash, for which the high strength of CR550LA is ideal.

The use of CR550LA enables engineers to design components with even thinner wall thicknesses, making a maximum contribution to lightweight construction.

Conclusion

CR550LA according to VDA 239-100 represents the pinnacle of cold-rolled steel grades. It’s an ultra-high-strength material that meets the highest demands for passive safety and elevates lightweight construction in the automotive industry to a new level. Although its formability is restricted, it offers unparalleled strength that’s indispensable in certain applications.
For engineers and technicians working on the development of future technologies in body construction, CR550LA is a crucial tool to push the boundaries of safety, efficiency, and performance, and to shape the next generation of vehicles.