Effect of coarse grain band on the ridging severity of 409L ferritic stainless steel

• Examined the formation of ridging defect in ferritic stainless steel.
• Presence of coarse grain bands in rolled sheet was correlated with ridging.
• Coarse grain bands form by the incomplete breakdown of cube oriented crystals.
• Hot-band annealing at 940 °C homogenized the grain sizes and prevented ridging.
• Uniform ferrite grain size distribution is necessary to prevent ridging.

A systematic study has been carried out to identify the cause of ‘ridging behavior’ in 409L grade ferritic stainless steel by studying the sequential changes taking place in the microstructure and crystallographic texture during industrial processing of this steel. Coarse grain sized bands comprised of primarily cube oriented ferritic grains have been found to form inside the cold-rolled and annealed sheets. A direct correlation has been found between the severity of coarse-grain banding and ridging phenomenon. In order to overcome the ridging defect by restricting the formation of coarse grain sized bands, hot-band annealing at sufficiently high temperature (~ 940 °C) has been found to be necessary, prior to the cold-rolling and annealing operation.

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