{"id":1386,"date":"2018-10-09T15:30:18","date_gmt":"2018-10-09T15:30:18","guid":{"rendered":"https:\/\/aboutfoundry.com\/?p=1386"},"modified":"2018-10-09T15:30:18","modified_gmt":"2018-10-09T15:30:18","slug":"lining-work-and-sintering","status":"publish","type":"post","link":"https:\/\/aboutfoundry.com\/en\/lining-work-and-sintering\/","title":{"rendered":"Lining work and sintering"},"content":{"rendered":"\n

The inner surface of the induction furnace coil and the ceramic upper construc-\ntion (upper concrete ring) must form a smooth surface, without any deposits,\nwhich tapers gradually to form a cone at the top. If a crucible removal device is\nused, the conicity should be 0.8%. When working with an outer lining with\napprox. 40 mm overlap at the bottom, the coil plastering should not be applied\nconically. In this case, the conicity of the outer lining is sufficient. The coil plas-\ntering and the outer lining are applied with a water content of 5 \u2013 8%. This mois-\nture leads to a long drying time, and thus also to extended starting times. In\norder to remove this moisture from the coil plastering and the outer lining quick-\nly, these can be dried out with a gas burner and the tamping form. The coil plas-\ntering can be dried out at a maximum of 150 \u00b0C and the outer lining at a maxi-\nmum of 350 \u00b0C in the lower area.\n<\/p>\n\n\n\n

The drying time in both cases should be at least 24 hours, if the outer lining has\nbeen cast immediately after application of the coil plastering, the drying time\nshould be at least 36 hours. The temperature increase should be between 30 to\n50 K\/h.\n<\/p>\n\n\n\n

If no burner is available, the drying can also be carried out inductively for medi-\num-frequency furnaces.\nIf neither gas nor inductive heating are to be used, the coil plastering and the\nouter lining should be allowed to dry out normally in air for approx. 12 hours,\nand then dried out for a further 24 hours with a 3 kW or 6 kW fan heater placed\non the bottom of the furnace, depending on the furnace size. Some customers use\nresistance-heated \u201cbaskets\u201d, which are supplied with a line through the furnace\nbottom. In the case of electrical heating, the heating should be carried out with\nthe furnace cover closed.\n<\/p>\n\n\n\n

Before applying the tamping compound, the inner surface of the coil is\n\u201cpapered\u201d with 0.5 mm of Cogemikanit or similar material up to the edge of the\nfurnace. Micanites with added flow materials are expensive, and provide hard-\nly any heating benefits.\n<\/p>\n\n\n\n

The furnace bottom with the bottom electrodes is now prepared for the applica- tion of the bottom compound. The tamping compound is filled in to such a level that the bottom electrodes can be tamped over to a depth of approx. 10 mm. This is usually carried out after manual ventilation using a bottom agitator, which is powered electrically or pneumatically. Agitation continues for 5 \u2013 10 minutes depending on the furnace size. For bottom thicknesses of over 350 mm the work should be carried out in 2 layers, paying special attention to the bottom elec- trodes. After the bottom agitator has been removed, the bottom height from the furnace edge must be checked and recorded. Now an outer ring is well keyed around the furnace bottom up to the cone of the tamping form (at least 15 mm), in order to provide a good connection to the crucible wall. The tamping form is installed, centred and fixed in place at the crucible edge using wooden wedges. The crucible wall is filled up to the edge of the furnace in layers of 300 to 400 mm. After every layer, \u201cNeptune zinc\u201d ventilation is carried out to ensure better final compaction. Compaction must now be carried out very carefully in the area of the bottom cone. For the crucible wall, the self-rotating wall agitator is used. This must be installed in the lowest possible position using a crane, and agitation applied in this area for approx. 5 minutes. Agitation then continues for 2, 3 or 4 minutes for furnaces with up to 800 mm diameter and 100 mm height difference, up to 1,200 mm diameter and 125 mm height difference and over 1,200 mm diam- eter and 150 mm height difference respectively. Since the crucible wall will be subjected to high mechanical stresses in the upper area, the greatest care must be exercised here. The upper 200 mm are compacted by hand after removal of the wooden wedges. Die tamping compound should finish approx. 50 \u2013 70 mm below the furnace edge. Tamping compound should be added continually during agitation to avoid the formation of layers between the compacted compound and the added compound. A thin patch layer is then applied to the ring of the crucible wall to prevent the tamping compound trickling out at the 1st tapping. The com- pound is not scraped out of the casting spout. In the case of disposable and per- manent templates, the casting spout should also be filled with compound in order to achieve a higher filling level during sintering. In the case of a disposable template, the compound is removed from the casting spout following completion of the sintering process, and the area dried with a welding burner. After approx. 10 minutes, this part of the tamping form becomes so soft that a \u201cbreakthrough\u201d can be made to the casting spout using a crowbar. The iron now flows into the casting spout and the furnace can be tipped for the 1st time.<\/p>\n\n\n\n

When using a permanent template, this must be provided with a supporting film\nof micanite or with a separating agent prior to installation. There are conical\ncomplete templates available, as well as folding templates.\nIn the case of the conical complete template, this is heated up to approx. 450 \u00b0C\nafter agitation at a rate of approx. 150 K\/h, and then cooled down after 1 hour\nto 200 \u00b0C with compressed air or cooling fans. To remove it, the template must\nbe pulled directly upward in a single movement. The folding permanent tem-\nplate is not heated, and is removed by folding in one of the 120\u00b0 segments.\nFollowing removal of the templates, an \u201cimpact protection\u201d layer of recycled\nmaterial is applied to the furnace bottom. The height of this layer should be 200\n\u2013 300 mm, depending on the furnace size. The crucible must now be filled up to\nthe casting spout as quickly as possible. No power should be switched to the\nfurnace during this time. Once the maximum filling level has been reached,\npower is switched to the furnace, providing a temperature increase of approx.\n100 K\/h, i.e. about 40 kW\/t, or 200 kW for a 5-t furnace. At this output, the melt\nis brought up to sintering temperature and maintained at this level for approx.\n2 hours. The 1st tapping is then carried out, and a total of 3 charges should be\nprocessed.\n<\/p>\n","protected":false},"excerpt":{"rendered":"

The inner surface of the induction furnace coil and the ceramic upper construc- tion (upper concrete ring) must form a smooth surface, without any deposits, which tapers gradually to form a cone at the top. If a crucible removal device is used, the conicity should be 0.8%. When working with an outer lining with approx. … Continue reading Lining work and sintering<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[2],"tags":[],"class_list":["post-1386","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"acf":{"adresse":"","telefon":"","e-mail":"","webseite":""},"_links":{"self":[{"href":"https:\/\/aboutfoundry.com\/en\/wp-json\/wp\/v2\/posts\/1386","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aboutfoundry.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/aboutfoundry.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/aboutfoundry.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/aboutfoundry.com\/en\/wp-json\/wp\/v2\/comments?post=1386"}],"version-history":[{"count":1,"href":"https:\/\/aboutfoundry.com\/en\/wp-json\/wp\/v2\/posts\/1386\/revisions"}],"predecessor-version":[{"id":1387,"href":"https:\/\/aboutfoundry.com\/en\/wp-json\/wp\/v2\/posts\/1386\/revisions\/1387"}],"wp:attachment":[{"href":"https:\/\/aboutfoundry.com\/en\/wp-json\/wp\/v2\/media?parent=1386"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aboutfoundry.com\/en\/wp-json\/wp\/v2\/categories?post=1386"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aboutfoundry.com\/en\/wp-json\/wp\/v2\/tags?post=1386"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}