www.ireng.org Meeting the unique demands on kiln furniture
The story is similar when it comes to kiln furniture, which is subject to intense demands on its performance including the effects of rapid heating and cooling, making materials choice and design absolutely critical.
There are many systems available in various materials which are suitable for lower temperature processing. However, demands from within the industry for kiln furniture led Morgan to develop a new high-performance nitrite- bonded silicon carbide material suitable which can withstand temperatures of up to 1,500ºC (2,732ºF).
The material, known as Halsic-N™, combines the properties of proven materials such as silicon carbide (SiC) and silicon nitride (Si3N4) in a microstructure which delivers strength, excellent refractory properties and resistance to oxidation and thermal shock.
Standard designs include setter plates, beams and supports, while components can also be produced to individual customer specifications.
Thermocouple protection tubes made from Halsic-N™ are ideal for the melting of non-ferrous metals such as aluminium and magnesium, where its strong metal-repelling characteristics help ensure long service life and optimized performance.
With flexural strength of 160MPa, Halsic-N™ can even be coated with a specially formulated coating for the firing of porcelain or technical ceramics.
The shape of things to come?
When it comes to fired refractory shapes, the need to employ best practice is equally pronounced. While it is recognised that these products are generally used only once and so need to withstand a single firing, they are generally subject to rapid heating and cooling and so need to be strongly resistant to thermal shock. More and more frequently they are used with expensive cast metals and superalloys, an area where material loss as a result of a failed consumable is not acceptable due to the high material costs involved.
Technical Paper
Once again, material quality is paramount. Even under high-temperature firing, it is crucial that oxidisation of consumable products is kept to an absolute minimum to prevent contamination of the materials being processed. This means purity of consumable products is vital and so another area where rigorous investigation of suppliers’ raw materials sourcing and manufacturing processes represents time well spent.
The best options for inert and vacuum furnaces
As detailed above for ceramic furnace consumables, high temperature inert and vacuum furnaces pose similar challenges for purchasers and designers. In these ultra-high temperature furnaces, which are capable of reaching temperatures of 3000ºC (5432ºF), designing the proper insulation solution of carbon or graphite felt, and carbon or graphite rigid board, is incredibly important, as the costs of these heat treating processes play an increasing role in the expansion of high-end technologies such as solar and semiconductor products. There are a variety of standard materials available designed specifically for these applications. Many of these materials can also be enhanced in a number of ways to provide the process or furnace designer with additional options. For instance, felt products can be specifically designed to provide enhanced insulation performance or longer life. The rigid board products offered by Morgan include a standard material as well as a low thermal conductivity material, RGB-LTC, for energy improvements across many applications. In addition, for use in harsher environments, specially developed coatings can be applied to improve life or reduce friability. Purity of the insulation is also vital for product performance. Many levels of purity can be supplied, offering the designer even more options. Whatever the application or need, providing a specific solution to solve a specific problem is key in providing the best cost of ownership for the purchasing company.
Product specification and system design are not areas where processors should feel they are on their own. The leading manufacturers of these systems are keen to be more than just suppliers and to work in a strategic and collaborative way with customers, gaining a deep understanding of their individual application requirements, then assisting with system design and recommending and supplying the most appropriate consumables, whether these be standard products or need to be developed on a bespoke basis.
They will even partner with installers to help ensure best design practices and that issues such as poor sealing around doors, for example – an issue which can rapidly negate the investment made in a premium product – are avoided. A good installer will ensure the very best is obtained from the product selected.
Above all, consumables should not be treated as commodities – they are vital tools without which effective processing cannot take place.
For further furnace. information visit
www.morganthermalceramics.com/kiln-
May 2016 Issue
ENGINEER THE REFRACTORIES
15
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