Perfect Insulating Materials for the Steel Industry. For more than 40 years Refratechnik has been developing products with this natural raw material. With the foundation of Refratechnik Casting in 1997 a re-orientation of Refratechnik’s activities, in this field, took place. The Casting experts have 25 years of experience in the production and application of biogenic silicas. This know-how has helped put Refratechnik Casting into a commanding position.

1. REFRATECHNIK
NERMAT® / SILIMAT®
Perfect insulating materials
for the steel industry

2. 22©Refratechnik Casting GmbH
NERMAT® / SILIMAT®
Biogenous silica
For more than 40 years
Refratechnik has been develop-
ing products with this natural raw
material. With the foundation of
Refratechnik Casting in 1997 a
re-orientation of Refratechnik’s
activities, in this field, took place.
The Casting experts have ­
25 years of experience in the
production and application of
biogenic silicas.
This know-how has helped put
Refratechnik Casting into a
­commanding position.
NERMAT® AF
Product examples
NERMAT® BF-LC NERMAT® BF-V
NERMAT® BF
NERMAT® AF-V
SILIMAT® GSILIMAT® GS

3. 33©Refratechnik Casting GmbH
Biogenous silica
Production and properties
Biomass power plant
Rice husks
Properties
Biogenous silica features a high
chemical purity and consists
of 94-96% SiO2. After a special
­combustion process, the main
­phases are amorphous silica,
­tridymite and cristobalite.
This explains the high ­melting
point of about 1650 °C.
During ­production, the volatile
­constituents are ­incinerated,
but without ­destroying the
­microporous structure of the
SiO2. It is this structure that leads
to the extremely low thermal
­conductivity as well as the low
bulk weight of biogenous silica.
Thermalconductivity[W/m·K]
Temperature [°C]
0.5
0.4
0.3
0.2
0.1
0
250 500 750 1000 1400
Thermal conductivity of biogenous silica
Microporous structure of SiO2
Production
The term ‘biogenous silica’ −
also known as rice husk ash −
indicates the products' source.
Biogenous silica is a natural,
­renewable raw material.
Rice husks are used in ­modern
biomass power plants as a
­quality-controlled source of
­energy. Hereby, the raw material
is burned in a carbon-neutral
­manner. This means that ­during
combustion, no more CO2 is
­released than the rice plant
absorbed from the atmosphere
during its growth – an aspect
that is gaining in importance
for raw materials in the future.

4. 44©Refratechnik Casting GmbH
Biogenous silica
Application
Thanks to its special properties,
biogenous silica is the ideal
and therefore most widely used
insulating material in the steel
industry.
Temperature
Covering layer thickness
Temperature
of the steel
melt
Other
insulating materials
Surface temperature of the hot
insulating material
Temperature difference up to 800 °C
Surface temperature of biogenous
silica covering layer
Biogenous
silica
Thermal insulating mechanism of biogenous silica
Steel casting ladle for continuous casting
For more than 30 years, NERMAT®
has been the classical material for
thermal insulation of tundishes,
steel casting ladles, blast furnace
runners and in the production
of rolling and forging ingots.
Therefore, it has set worldwide
standards in terms of quality and
efficiency.

5. 55©Refratechnik Casting GmbH
When applied to the surface of
the steel melt, the rice husk ash
forms a protective layer that
prevents contact between melt
and atmosphere, and thereby the
absorption of N2 and H2.
SILIMAT®NERMAT®
Finished rolling ingot
Tundish with NERMAT® covering
Operating principle of high-grade silica
O2,N2 T
Al2O3
NERMAT® solid
NERMAT®
protective layer
Liquid steel
Without insulating material With high-grade silica
insulating material
O2,N2

6. 66©Refratechnik Casting GmbH
SILIMAT® is the low-carbon
­version, with carbon contents
of min. < 0.1%. This light-coloured
biogenous silica is particularly
­recommended and used for the
production of ULC steel grades.
Our rice husk ash products
NERMAT® and SILIMAT® can be
used as a single layer covering,
or as a “sandwich” layer in com-
bination with our slag-forming
insulating materials REFRAFLUX®
and REFRAMAT®.
Depending on the manufacturing
process, various bulk weights of
our products are possible.
Biogenous silica
Application
Ladle
No thermal
diffusion
Al2O3
NERMAT®
NERMAT®
protective layer
Ladle
Thermal
diffusion
Al2O3
NERMAT®
REFRAFLUX®
synthetic
slag former
Example 1: Single-layer covering
Example 2: Sandwich covering layer
Technical data:
Quality Colour Max. grain size
[mm]
Bulk weight
[kg/m³]
Carbon content
[%]
NERMAT® AF Black 3 ~ 200 < 6
NERMAT® AF-V Black 4 ~ 160 < 6
NERMAT® BF Black 2 180-280 3-12
SILIMAT® G Grey 2 ~ 230 < 1.5
SILIMAT® GS Pink 2 ~ 300 < 0.1

7. 77©Refratechnik Casting GmbH
Refratechnik Casting GmbH
belongs to the Refratechnik Group,
one of the world's most impor-
tant manufacturers of refractory
­products.
The Refratechnik Group is certified according to:
ISO 9001 – Quality management systems, and
ISO 14001 – Environmental management systems.
Let´s talk about your goals.
We will find the right way.
The administration as well as
research & development depart-
ment are located in Düsseldorf
and at the Refratechnik parent
plant in Göttingen.

8. Ca1-009-11/2013
Refratechnik Casting GmbH
Schiessstrasse 58
40549 Düsseldorf
Germany
Phone +49 211 5858 0
Fax +49 211 5858 149
casting@refra.com
www.refra.com
Ca1-009-11/2013