Curiosity is part of our DNA. We would not be the EXPERTS ON FIRE if we had not continuously developed further. We are permanently busy with innovative developments and continuous improvement of refractory products and casting auxiliaries at our site in Krefeld. A competent and innovative team of metallurgists, mineralogists, chemical engineers, ceramic engineers and technicians, and chemistry lab technicians is working in an optimally equipped research center. We strive to improve the performance of our existing products and to develop new ones – from raw materials to final products all the way to end-use specific holistic refractory concepts. Obviously, market and customer needs always serve as orientation for our way forward. In our development work it is understood that we always have to keep one eye focused on costs, performances, and possible product interaction with customer processes.
We develop new ideas and innovative solutions for production, raw material sourcing, distribution, application technology, and constructional design. For the determination of product characteristics, our technology center is equipped with state-of-the-art chemical, mineralogical, microscopic and thermal analyzing methods and apparatus.
It is not only the experts of the Technology Center that perform research and look for new solutions, but also the members of the INTOCAST GROUP OF EXPERTS at their respective sites. In this way, we are able to offer our customers in all areas the best suitable products and solutions in line with INTOCAST quality standards.
Research Papers
Michel Cichocki, Joachim Angelkort, Natalie Fröse, Storm Higgins, Manfred Knoll, Marcel Mix
Intocast AG, Westpreußenstr. 30, 47809, Krefeld, Germany
ABSTRACT
In recent years, silica sol solutions have been increasingly used as cement-free binders in refractory unshaped products. The silica sol solutions are aqueous colloidal dispersions of nanoscale amorphous SiO2 particles. Compared to conventional high alumina cement-bonded concretes, the silica sol-bonded products are characterized by good alkali and acid resistance. The main advantage, however, is that no calcium aluminate hydrate phases are formed during the setting process and thus these concretes can be heated much faster.
A major disadvantage of silica fume solutions is that they must be stored in separate containers, protected from frost and light. To avoid this, a new system in which the silica sol formation takes place "in-situ" in the refractory matrix is introduced. For this purpose, a microscale amorphous SiO2 powder is mixed directly into the refractory mass. By adding water, the silica sol formation is generated within the matrix. This eliminates many of the major disadvantages of using aqueous silica sol solutions. The addition of < 1.0 % of this binder leads to good green strengths of the refractory castable. To compare the binding of cement-free and cement-containing refractories, the physical and chemical properties of a nearly pure alumina product was tested. For this purpose, all tests were carried out on the cement containing products and their non-cement counterparts bonded by liquid sol-gel or by the in-situ sol-gel formation. Furthermore, an example of application will be given proving the efficiency of the in-situ sol-gel technique for practical use.
Sasan Otroj*, Manfred Knoll
Intocast AG, Germany
ABSTRACT
Angelkort*, M. Cichocki, S. Higgins, Y. Lakotta-Weinhold, N. Fröse, M. Mix
Intocast AG, Westpreußenstr. 30, 47809, Krefeld, Germany
ABSTRACT
Four additives (a sodium polyphosphate, microsilica, titania and zirconia) were tested in a magnesia alumina castable to investigate their influence on the spinel formation at high temperatures. The impact of the additives is studied with respect to both the amount of spinel formed in the burned castable and the microstructure established by the spinalization.
Dilatometric measurements conducted on the castables allowed to determine the onset temperature of the spinel formation, which was indicated by a strong increase of the linear thermal expansion. For phosphate-containing samples, the expansion associated with the spinelization occurred already ~100 °C below the temperature at which the corresponding expansion was observed for the additive-free reference sample.
Furthermore, by a heat-treatment of the castables at 1200 °C or 1500 °C, the phosphate-containing samples developed notably higher amounts of spinel than the reference sample. The phosphate addition in these samples also results in a remarkably larger increase of the sample volume during the heat treatment and comparatively lower mechanical strengths of the burned samples. The SiO2, TiO2, or ZrO2 additions influenced the physical properties of the castable in a substantially smaller degree than the addition of sodium phosphate, and they also exerted a smaller effect on the spinelization in the castable than the latter one.
Anton Yehorov, Olena Volkova,
TU Bergakademie Freiberg, Freiberg, Germany
Marcel Mix, Natalie Froese
Intocast AG, Westpreußenstraße 30, 47809 Krefeld, Germany
ABSTRACT
The present work experimentally studied the corrosion behavior of MgO-C ladle refractory exposed to molten slag during steel refining. The corrosion of ladle refractories, especially at the slag line, causes issues that require maintenance and repair and can even lead to melt outages.
ABSTRACT
The setting of cement pastes containing calcium aluminate cements (CACs) can be accelerated by additions of selected alkali metal or alkaline earth metal compounds. In this work, the accelerating effects of Li2CO3, MgCO3 and a sodium alginate are studied on basis of quantity-dependent changes in the phase assemblage of hydrated CAC samples (water cement ratio w/c = 1). The samples were hydrated for 24 hours and then used to measure X-ray diffraction data. In quantitative phase analyses, employing the measured data, the sample compositions were determined.
Generally, the first hydrate phases which crystallize during the CAC hydration at room-temperature are C2AH8(2CaO·Al2O3·8H2O), CAH10 (CaO·Al2O3·10H2O) and AH3 (Al(OH)3). In samples whose dry mixtures possess a Li2CO3content of 0.0 to 0.03 wt%, all three hydrate phases crystalize during the initial hydration. The CAH10 content in these samples, however, decreases drastically with increasing Li2CO3 addition. In samples with a Li2CO3 content of 0.04 wt% or higher, the CAH10 phase is absent. The phase amounts of C2AH8, AH3, C3AH6 and a Li2CO3-containing layered double hydroxide (LDH) also depend on the added amount of Li2CO3. While CAC samples containing ~0.1 wt% Li2CO3 develop particularly high amounts of C2AH8 during hydration, a further increase of the Li2CO3 amount is associated with a decrease in the C2AH8 amount and an increase in the C3AH6 amount. The inversely correlated formation of C2AH8 and C3AH6 seems to result from a transition of C2AH8 into C3AH6.
Compared to additions of Li2CO3, additions of MgCO3 or sodium alginate induce much smaller changes in the phase composition of the hydrating CAC and are not associated with a suppression of the CAH10 formation.
ABSTRACT
In this paper, the effective parameters on increasing the durability of pitch-bonded MgO-C bricks used in the trunnion area of the steel converter has been studied. In this relation, the durability of the pitch-bonded MgO-C bricks containing B4C, and carbon fiber and different types of magnesia and graphite has been compared together. For this reason, the thickness measurement of remainder bricks by use of laser has been considered as durability of bricks and has been used to compare their wear rates. Besides, the physical, mechanical, and thermo-mechanical properties, microstructure, thermal expansion during the thermal cycle and the oxidation resistance of these bricks has been investigated. The results showed that the purity and crystal size of magnesia grains, the purity of graphite and B4C addition have a great effect on the durability of pitchbonded MgO-C bricks used in the trunnion area of the steel converter.
Joachim Angelkort*,1, Natalie Fröse1, Manfred Knoll1, Bernd Epstein2, Stephan Fromm2, Ingo Hofmann2
1 - Intocast AG, Westpreußenstraße 30, 47809 Krefeld, Germany
2 - VGT-Dyko GmbH, Großalmeroder Str. 18, 37247 Großalmerode, Germany
ABSTRACT
Large or complex-shaped bodies of nitride-bonded SiC-based ceramics can successfully be produced from thixotropic castables by burning of semi-finished products in a nitrogen atmosphere. To reduce the fragility of the semi-finished products, typically composed to about 90% of silicon carbide and silicon metal, a calcium aluminate cement (CAC) might be admixed in the castables serving as a binder. The presence of calcium-rich phases, however, can result in the formation of calcium silicates during the nitridation and alter drastically the physical properties of the nitride-bonded SiC ceramics.
In this work, the influence of a CAC admixed into thixotropic castables is studied in respect to its effect on the phase composition and the physical properties of nitride-bonded SiC ceramics produced from the castables. To determine the phase composition of the ceramics, quantitative phase analyses were carried out using measured powder X-ray diffraction data. Standardized test methods were applied to measure the cold modulus of rupture (CMOR) and the cold crushing strength (CCS) of the nitrided samples. The microstructures of the samples were investigated by scanning electron microscopy. Additionally, water vapor oxidation tests were undertaken to probe the oxidation resistance of the samples.
Joachim Angelkort*,1, Natalie Fröse1, Manfred Knoll1, Bernd Epstein2, Ingo Hofmann2
1 - Intocast AG, Westpreußenstraße 30, 47809 Krefeld, Germany
2 - VGT-Dyko GmbH, Großalmeroder Str. 18, 37247 Großalmerode, Germany
ABSTRACT
To complement the production method of SiC-based ceramics fabricated by ramming, a thixotropic no cement (NC) mass was developed allowing for the production of nitride-bonded SiC-ceramics with a complex shape or large size. Nitrided specimens casted from this mass exhibited a similar strength as it can be observed for nitrided specimens of pressed or rammed products. Within this work the properties of nitrided ceramics produced from both a thixotropic and a ramming mass are compared. Moreover, experimental findings derived by electron microscopic studies as well as results of X-ray diffraction investigations on samples of nitride-bonded SiC-ceramic are presented. The influences of some additives on the phase formation during the nitridation and on the resulting microstructure are discussed.
Joachim Angelkort*, Manfred Knoll, Angelina Reichert
Intocast AG, Westpreußenstraße 30, 47809 Krefeld, Germany
ABSTRACT
Aluminum hydroxide is used as a cementitious phase in the production of refractory linings. Fast heating of these types of linings can cause a spallation by abrupt water release. To facilitate a continuous evaporation of water during heating, the intergranular space of the microstructure of the linings is often enlarged by the use of organic aggregates possessing a bulky molecule structure. Insertion of ions into the crystal structure of aluminum hydroxide, a so-called intercalation, can possibly also influence the dehydration behavior of the linings. As the intercalation of aluminum hydroxide results into a widening of the distance between the Al(OH)3 layers, the amount of water molecules transferring between crystal and surrounding medium increases concomitantly with the insertion of ions.
Different intercalation compounds and their synthesis are described in the literature. While many of the corresponding articles report about the synthesis of intercalation products originating from insertion of lithium salts into the crystal structures of Al(OH)3, there is little information about the successful intercalation of magnesium salts. From economical point of view, however, an intercalation of magnesium salts would be more favorable than the use of lithium compounds. Recently, we were able to crystalize the new intercalation compounds [LiAl2(OH)6] CH3O2·nH2O, [MgAl4(OH)12](CH3O2)2·nH2O and [MgAl4(OH)12] (NO3)2·nH2O by heating aqueous suspensions of aluminum hydroxide and metal salts. To determine the dehydration behavior of the synthesized samples, thermogravimetric measurements were carried out. X-ray diffraction experiments were evaluated to relate changes of the dehydration behavior with changes of the crystal structure accompanying the intercalation.
Marcel Mix - Intocast AG, Pempelfurtstr. 1, 40880 Ratingen, Germany
Manfred Knoll - Intocast AG, Westpreußenstr. 30, 47809 Krefeld, Germany
Joachim Angelkort - Intocast AG, Westpreußenstr. 30, 47809 Krefeld, Germany
Michael Gestal - Intocast AG, Pempelfurtstr. 1, 40880 Ratingen, Germany
Mag-Carbon bricks as working lining combined with a monolithic or a masonry permanent lining is recently the “state of the art” and the most frequently used refractory lining of steel ladles. The technology of the lining has been established over many years and is undoubtedly a guarantee for the successful metallurgical treatment resulting in prolonged service lives. The excellent corrosion resistance of this refractory lining in the slag zone is particularly noteworthy.
Also known for many years but rarely practiced, is the use of a completely monolithic lining as working lining in combination with bauxite bricks as permanent lining employing vibration or self flow casting compounds based on alumina or alumina magnesia according to the "Endless Lining System". This casting method possesses clear advantages in terms of material consumption, flexibility and effectiveness to increase the availability of the ladles and is associated with positive ecological aspects.
Particularly nowadays, in a time when the market shows a rapid rise of raw material costs, especially for basic materials, cost optimization is mandatory to maintain competitiveness. An expertise of the two lining systems of the steel ladle offers the possibility to combine them and to adjust the desired properties of the lining. Therefore the key of success is the combination of different systems to the so called “HYBRID LADLE”.
The result is the best technical and commercial solution for steelmaking in terms of operational safety, the demand of refractory materials as bricks and masses, the service of personnel, the availability of refractory materials and a contribution to environmental protection that should not be underestimated.
J. Angelkort *, M. Knoll, A. Reichert
Intocast AG, Westpreußenstr. 30, 47809 Krefeld, Germany
C. Wöhrmeyer
Kerneos GmbH, Centroallee 275, 46047 Oberhausen, Germany
M. Szepizdyn
Kerneos Research Center Europe, 1 rue le Chatelier, 38090 Vaulx-Milieu, France
ABSTRACT
In recent years the quality requirement for steel has increased significantly. The performance of steel can be penalized if for example the hydrogen content is higher than specified by the producer. In modern steel plants the tundish is the last vessel in which liquid steel is in direct contact with refractory materials. To investigate the rehydration process of a refractory material used in the production of tundish linings, different experiments were performed on samples of calcium aluminate-bonded low-cement castables and the pure cement constituting the binder of the castable. To achieve a high extent of rehydration, the samples were exposed to experimental conditions which were extremely humid and did not correspond to the conditions encountered by the refractory materials of the tundish in reality.
To determine the amount of chemically bound water present in samples of the low-cement castable after rehydration, the weights of non-rehydrated samples were compared with the weights of rehydrated samples after drying. The water release was also investigated by conducting thermogravimetric analysis. X-ray diffraction patterns were measured on a sample of pure calcium aluminate cement (CAC) to determine the phases compos-ing the matrix of the castable. Changes of the phase composition caused by casting, heating and rehydration were studied.
Our experiments show that the extent of rehydration of samples of the low-cement castable is influenced by the relative humidity (RH) of the atmosphere in which the samples were rehydrated and the height of the temperature attained for pre-heating the samples. While samples rehydrated for two weeks in an artificial atmosphere possessing 70 %RH contained maximal 0.3 wt% bound water, samples exposed for two weeks to an atmosphere of 100 %RH or stored under water incorporated up to 1.9 wt% bound water. Castable samples that have been pre-heated at 1200°C didn’t show any significant rehydration even after storage under water.
