For magnesite and aluminium oxide refractories liquid resole resin, liquid novolac or liquid/powdered novolac resins can be used. Two resins are particularly recommended for magnesite carbon and alumino-silicate bonding: PF-5311 – Liquid resole PF-4012 – Powdered novolac
PF-5311 has a tightly controlled molecular weight distribution and high wetting ability. It provides rapid mixing 14 and high CCS and carbon yield. It can be used as the sole binder if friction presses are used, but hydraulic presses usually require the addition of PF-4012 powdered novolac to achieve the required green strengthDolomite For dolomite refractories, which are sensitive to water, a combination of special liquid novolac and powdered novolac resin are normally used. SQH® can offer the following proven system for dolomite bonding: UK-7007 – Liquid resin UK-6515 – Powdered resin
Isostatically shaped products include submerged entry nozzles (SEN), monobloc stoppers, shrouds etc. The mix should be very free flowing to prevent in-homogeneity when mould filling. Use of furfural as a wetting agent, plus high molecular weight powdered phenolic resin in a rotary mixer yields a free flowing, partially pelletised mix. The partial pelletisation affords a type of pre-compression and allows her easy mould filling and pressing. Unlike normal shaped refractories, after isostatic pressing the green uncured mouldings are cured to a maximum temperature of around 200ºC, then the cured resin binder is carbonised by pyrolysis in a reducing atmosphere at 800 - 1,000ºC. To prevent distortion the mouldings require adequate support, and an oven temperature profile that balances reduction in resin viscosity with increasing temperature, with the increase in resin molecular weight with cure.
PF-5408 – Liquid resin PF-5030 – Liquid resin UK-3370 – Powder resin
Slide Gates
use alumina oxide – zirconium oxide refractories and are usually produced using a liquid resole or novolac resin combined with the addition of a high molecular weight powdered resin. If liquid novolac resins are used an addition of hexamine will be required, (10 - 14%) based on solid novolac. Normal phenolic resin systems lose strength around 400 - 550ºC due to the carbonisation process. SQH® new silicone modified resin UK-5455, provides a useful increase in strength over this critical temperature region.
Unshaped Refractories Phenolic resins can be used to produce a range of unshaped refractory mixes.
Blast Furnace Tap-hole Clay
The wide range of cure and plasticity properties possible with phenolic resins means that it is possible to design resin systems to match specific tap-hole clay requirements.
Ramming and Vibratory Compaction Mixes Liquid novolac or modified resole resins with hexamine additions can be used to produce ramming mixes. For dry, free flowing vibratory mixes, novolac powders with low dust levels are available. The hexamine level required can be varied to match the application
Impregnation Both fired and resin bonded shaped refractories properties can be improved by impregnation at ambient temperatures with low viscosity liquid resins or novolac solutions. Impregnation is usually carried out in a vacuum/pressure vessel to ensure complete impregnation. Solid novolacs allow impregnation to be carried out at elevated temperatures.