Sheet metal is normally cold-formed, but in some cases, for example bending or deep drawing, material can be heated, usually only locally, so that you can increase its formability.
Since sheet metal is using tensile or tensile-pressure forming, tools used are less loaded than during bulk forming. Product accuracy, particularly for thick sheet metal, is just not great, since surfaces are partially free and material is created across the easiest natural path. However, product accuracy could be significantly increased using ironing and fine blanking. In such cases, certain dimensions could be inside the tolerance class up to high tolerance.
On the whole, formability depends upon the content and the process involved. It is usually understood to be the capacity of an material to deform without the appearance of fracture or any other defect inside a forming process. Since tensile or tensile-pressure stresses happen in the information during sheet metal forming, and shear stresses occur during separation, the formability of sheet metal just isn't high. One of the most frequent criteria used for the formability of sheet metal are:
Fracturing, which occurs whenever a sheet metal is exposed to stretching (drawing), or shearing. In stretching, diffuse and localised necking appears ahead of fracture. In shearing, fracture might take place without prior thinning.
Wrinkling, buckling. In processes, where pressure stresses also occur in sheet metal, the fabric, unless appropriately limited, buckles. An average instance of this can be deep drawing, in which a workpiece's flange must be compressed between your die and the blankholder, or wrinkling will occur.
Undesirable surface textures can be displayed in many forms. Heavily deformed material, usually coarse grained, often develops a tough surface texture (orange peel). On top of products from materials using a pronounced yield point elongation, lines might appear (in irregular bands these are classified as Lüders lines).
