must be prepared for optimum earthing at the crucible bottom. Earthing in the casting spout is only effective after the 1st casting. In order to earth the crucible, a spiral with at least 5 windings of 3 mm wire is installed in the furnace bottom. This spiral is then covered with fine-grain graphite powder to a level such that the graphite clay crucible reaches its installation height after a few rotations. The back-fill compound is then filled in and compacted. Finally, the upper edge of the back-fill compound is sealed off with a patch, so that the back-fill compound cannot trickle out when the crucible is tipped. Prior to the 1st charging with scrap or molten material, the crucible should be heated up inductively at an output of approx. 40 kW/250 kg of crucible weight. The crucible should have a light red colour approx.100mm below the crucible edge. Fine material (preferably chips) should now be placed in the bottom and normal scrap filled in on top. The 1st charge can now be melted.
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