**11. Metal processing**

The result of entrainment of bifilms during casting production results in huge losses in metals processing such as forging, rolling and extrusion. All these processes suffer from cracking of the processed metal, sometimes to the extent that the metal cannot be processed. Many steel ingots suffer from cracking during cooling. For this reason, fluted molds assist to disperse stresses across the faces of the ingot, although the technique is not especially successful for some steels. The break-outs of liquid steel from the cast strand during continuous-casting are almost certainly bifilm problems which is the reason this rather common disaster has remained unsolved. A number of Ni-alloy ingots are known for cracking at the first stroke of the forge, and rolled steels suffer edge cracking, longitudinal cracks, transverse cracks, internal cracks. Many metals suffer edge cracking during extrusion and rolling. Aluminum alloy semi-continuously cast slabs suffer cracks of all sorts, some measuring their length in meters across the slab face.

For those working in metal processing, valuable R&D has often been carried out to provide process 'windows' defining the limits of successful processing. Many such limits have been set by the onset of cracking. Processors would be delighted to see these limits eliminated. The processing of metals remains to be revolutionized.
