Bake-Hardenable (BH) Steels

A bake-hardenable steel is any steel that exhibits a capacity for a significant increase in strength through the combination of work hardening during part formation and strain aging during a subsequent thermal cycle such as a paint-baking operation.  These steels are made in the following grades:  

	BH180
	BH210
	BH240

Any steel with adequate carbon and/or nitrogen in solution to cause strain-aging may be classified as bake-hardenable.  In general, bake-hardenable steels are aluminum-killed steels with an adequate amount of aluminum to combine with the nitrogen as Aluminum Nitride (AlN).

A combination of relatively low yield strength prior to manufacturing and a high in-part strength after forming and paint baking makes bake-hardenable steels ideal for applications where dent and palm printing resistance is important.  This material can be used in relatively deep draw or stretching operations.  Due to the high in-part strength, bake-hardenable parts are also good candidates for downgaging, which is important for weight reduction efforts.

When using bake-hardenable steel, the amount of strain introduced during the forming process will largely dictate the final strength of the part.  Since automotive parts, specifically exposed body panels, have a wide array of designs, there will be a corresponding disparity in the amount of strain introduced in these varying geometries.  As a result, when using bake-hardenable steel, it is important to design an adequate amount of strain into a part in order to fully utilize this material’s dent resistant characteristics.

• Weldability – Low carbon level makes bake-hardenable steel a good welding candidate.

• Fatigue Performance – If used properly, bake-hardenable steels have a high yield strength after forming and baking, which means it will have a good resistance to fatigue. 

• Denting – Bake-hardenable steels were designed for dent resistance.

• Applications  –  Bake-hardenable materials provide customers with a material that is capable of reducing the amount of dents and dings found on today’s cars.  These materials have the formability requirements needed to produce most exterior applications.  These exterior parts benefit from the work and bake hardening kicks that are experienced during processing.  These parts include doors, deck lids, quarter panels, fenders, hoods and roofs.

Increase in yield strength during forming and baking of bake-hardenable steels

Typical Properties for BH 180 MPa:(Back to top)

Typical Properties for BH 210 MPa:(Back to top)

Typical Properties for BH 240 MPa: (Back to top)