Steel types

As well as solid-solution strengthening, steel manufacturers can use a range of techniques to make higher-performance steels. These techniques include grain refinement, work hardening, precipitation hardening and heat treatment.

Using these techniques, sheet steels can be developed with the ideal combination of formability and strength for specific automotive applications. For example, Fig. 3 below demonstrates the range of formability (elongation) and yield strength for a wide range of automotive sheet steel types. (Yield strength is defined as the point at which the steel begins to permanently stretch or deform.)

Each ellipse below represents the grades available within each steel type or ‘family’. The name for each family – see Table 2 – reflects the method by which the steel achieves its formability or strength.

Fig. 4 below illustrates the properties of three different grades of sheet steel, and identifies where in a vehicle structure they are most likely to be found.

The highest strength steel shown here has a yield strength (at point X) of 800N/mm² – roughly equal to eight tonnes per square centimetre.