Sensitive, water-cooled copper coils in induction furnaces are protected by a concrete wall (coil grout) against refractory (thermal insulation). Removal of the worn refractory material with a hammer drill is expensive and dangerous. A tear resistant mica-based layer of mica enables separation from residual (sintered) refractory mass from the concrete wall as it is pushed out and hence protects the coil, enlonges service life of the refractory in the crucible and reduces maintenance costs.
Effective application for coreless induction coil furnaces
Mica-based linings are flexible and easy to handle, and have replaced asbestos in most
countries of the world paying attention to non-hazardous products to maintain the health of foundry personnel.
Glasfibre reinforced, non-toxic and generally delivered on Roll, 1.000mm wide and 25m long (25sqm per roll). They serve as:
- Slip-Plane mica with high tensile strength
- Saftey-Layer protecting the coil against refractory material
- Separating-Layer gas diffusion barrier
- Isolation-Layer electrical and thermal protection
Newform Combi G (Mica/High-temperature paper made of CaSi),
Newform Foil PGM (Phlogopite/Muscovite mica reinforced with a glasfiber mat)
When lining induction coil furnaces, SiO2-based refractory material is inserted locally into the crucible and compacted to form the thermal insulation of Coil from smelt. The approximately 10 cm thick insulation degenerate, depending on the nature of the smelt, after some 200 applications (2-6 weeks with Medium Frequency Furnaces).
Removal of the old, used, mass and slag and relining of crucible furnaces with heat insulation demands caution and experience. Getting the coil grout surfaces then sufficiently smooth, so that no defects in the coil wall arise, is labor- and time consuming.
Newform provides an asbestos-free and biodegradable mica-based layer to serve as slip-plane. The insulating material consists of glasfiber reinforced mica paper laminated with heat-resistant binder to Calcium Silicate paper if required (at larger furnaces, where the wall is rather uneven).
This, generally 100cm wide and odorless "wallpaper" are delivered on a 25 m long roll. They are cut to required size and vertically mounted on the coil side of the crucible furnace (Fig. 1) and fixed at the top with glue (watery and halogen free) or tape. Mica side shows to the interior of the furnace (Fig. 2). The mica coating ensures good sliding between the refractory material and the coil grout.
Insulation fiber Newform Combi G is a flexible, cold formed laminate comprised of phlogopite and calcium silicate fiber with a special silicon binder. The approximately 2.4-2,5mm thick fiber for the isolation of induction furnaces tolerate temperatures up to 1,050°C, compensates surface unevenness of the, only 2 cm thick, concrete wall and thus reduces cavities.
Newform Foil PGM, is about 0,4-0.5mm thick, glassfiber reinforced and preferably used for smooth interior walls of the furnace to be found in smaller than 2ton furnaces usually.
Effective and health- and ecologically harmless
The asbestos-free insulation fibers and insulation foils for induction furnaces are based on Muscovite or Phlogopite mica (Fig. 3). Mica is a layered silicate with a high electrical resistance. It is heat resistant and in addition resistant to almost all media, such as alkalis, gases, oils and acids.
According to Hazardous Substances 91/155/EEC Regulation, mica has no health risks, both in storage and during installation and removal. Thus, no special measures have to be taken in respect of the removal of the insulation fibers and insulation films for induction furnaces. The material decomposes in nature into its individual components and can be safely disposed as construction debris and municipal waste landfills.
Newform has now expanded its product portfolio for the foundries and distributes adjacent products for the melting shop, like special software for optimized charging of used materials and alloys. It operates in 20 countries with a network of agents and partners, who know the local language and the corresponding national markets.
In Brazil Newform successfully cooperates with Z-Tech from Blumenau.
Autor und picture provider: David S. Gower, Newform
www.newform.de Tel.: 06151-605210 davidg(at)newform.de