Iron sheet is usually depicted on rolling mills .
The latter have two rollers and are equipped with a device to lift the sheet back after each pass through the rollers, or the rollers rotate in both directions (reversing or sweeping mills); however, rolling mills with three rollers are also used and the sheet is allowed to pass between the lower and middle roller in one direction and between the middle and upper roller in the other direction. Lintel (the thinnest iron sheet up to 0.1 mm thick) is made from flat iron by cutting it into pieces and stretching them glowing to a length corresponding to the width of the sheet to be made.
The lintels are then red-hot crossed into a second rolling mill so that the sheet length gradually emerges from their width. When it reaches a certain thickness, you bend it in the middle with a hammer, immerse it in clay water, insert several into each other and gradually roll them out completely while glowing repeatedly. The lintel plate, which is destined to be tinplate, is freed from annealing chip with sulfuric acid , annealed in closed pots and, after cooling, rolled under hardened steel rollers.
The stronger boiler plate is made in the same way from pieces of iron ( slabs ) that have been welded together from raw rods under a steam hammer . Heavy sheets are welded together under the rolling mill from two or more pre-rolled sheets. The strongest iron sheets are armor plates 0.3 m thick and more. The finished sheets are trimmed at the edges, namely the armor plates on slotting machines or planing machines , all the rest with scissors of various designs. Ordinary sheet iron ( black sheet ) is tinned to protect against rust and thus transformed into tinplate or galvanized (galvanized iron sheet), see Tinning and galvanizing .
- Meyer's Lexicon from 1888 , Volume 5, Page 5469