3. Choice of shades

Once the shape of the product has been defined, the choice is made according to the stresses of the construction or part. It is obviously advantageous in general to choose grades with high yield strengths to reduce weight and material costs, but this must take into account problems of stability, thickness limits (for corrosion, for example) and processing constraints such as weldability or forming.

As far as stability is concerned, limitations arise from simple buckling under compression, but also from other instabilities such as torsional buckling. Serviceability conditions play a part in the choice of grades if stresses change: this is the case for fatigue, but also...