Tapping (metallurgy)
The tapping (more rarely also tapping ) is the periodic opening of the shutter of a blast furnace in the iron and steel works . This enables the liquid pig iron to run out of the blast furnace.
For this purpose, the lower closure of the blast furnace, the so-called tap hole or bunghole , is opened with a long, compressed air-operated chisel and the batch of pig iron and slag emerge. On the stage of the blast furnace, a channel was previously formed from sand, concrete or bricks in order to let the molten iron run into the so-called “ fox ”. The fox is a siphon , which is basically a gutter with two drains, in which the pig iron is separated from the slag due to the different density. At the end of the fox, the pig iron passes over a hole in the ground for transport by torpedo car or an ingot caster, which however is used only in exceptional cases. The reason for this is the associated loss of energy, so that this process is normally only used in the event of disturbances in normal removal via torpedo pans. Slab casting from pig iron is not feasible, since solidified pig iron is not deformable due to the ledeburit content. The slag runs off through the siphon and is used as raw material, for example as blast furnace slag . Once the batch in the blast furnace has been emptied, the bunghole is closed again using an oversized syringe with a fast- setting cement or so-called tap-hole clay ( English tap-hole clay , plastic lumps with ceramic and organic components).
The blast furnace operator quickly takes several samples during tapping. After cooling in the water bath, these are broken with a blow of the hammer. The experienced blast furnace operator can immediately recognize the quality of the pig iron at the break point.
The racking is one of the most dangerous jobs in the metallurgical plant. The ironworkers have to protect themselves with shiny silver, aluminized protective clothing , aprons and masks from the radiation of the pig iron, which is glowing red at 1400–1600 ° C.
In addition to blast furnace tapping, other metallurgical units are also referred to as tapping when they are emptied. Examples would be the LD converter or the tapping of an electric arc furnace .
Individual evidence
- ↑ H. Schoppa: What the blast furnace operator needs to know about his work . Verlag Stahleisen., Düsseldorf 1992, ISBN 3-514-00443-9 .