Bobbin (metallurgy)
As a billet in is iron smelting intermediates understood, be it which is still to be processed, or being processed. The term is based on the historical production of iron using racing furnaces .
Historical derivation of the term
In the historical pig iron production since the beginning of the Iron Age , lobes (also called "race iron" or today "iron sponge") were the spongy iron chunks produced in the racing furnace . These were created by direct reduction from the ore without melting the iron - so they were not pig iron in the current sense.
The iron produced in this way for at least 3500 years (the Hittites are the earliest evidence of this ) was relatively low in carbon at low temperatures and with skillful furnace management - in contrast to liquid pig iron from the blast furnace - but it contained very slag and was therefore porous . From the red-hot, zähweichen (pasty) iron pieces the still liquid slag was manually by forging means of sledge hammers on the anvil forged - that is "hammered out" symbolic or "pressed out", and the iron by this process sintered .
As a rule, further forming processes followed with further frequent forging and folding over of the material with repeated fire welding . The forging processes further decarburized the iron, the structure became largely homogeneous . This produced an iron that was very easy to forge, almost pure, which, as so-called wrought iron, corresponded to today's soft iron or pure iron.
By means of subsequent carburizing in the forge fire, the workpiece - already forged in shape - could be hardened in order to manufacture weapons, tools, etc.
Modern uses of the term
The forging of Damascus steel or the puddling process in the puddling furnace, which is hardly used any more, is based on the same working technique to this day . When Puddelverfahren by puddling also need the refined iron fragments prior to further processing into semi-finished products such as angle iron or flat steel rods are forged and welded fire. In both processes, the intermediate products before / during the forming process are called Luppe , in the puddling process historically also Dachel or Deul .
From the history out is referred to as billet and the hollow body indicated that in the production of steel pipes by skew rolls or in the pilgrim-step method from a hot steel cylinder (block, stick) - supported by a piercing mandrel - is formed between two co-rotating rollers.
Web links
- Manufacturing process for steel pipes (PDF; 1.46 MB)
Individual evidence
- ↑ Pure Iron . Angele website (machine builder and forge supplier). Retrieved May 30, 2016.
- ^ Luppe (1), in Meyers Großes Konversations-Lexikon, 6th edition 1905–1909. Accessed on May 30, 2016.