DE10354261A1 - Unshaped refractory products, especially refractory concrete, with non-oxide components - Google Patents

Abstract

Refractory mass, containing a coarse-grained refractory component (so-called coarse grain) and / or a medium-grained refractory component (so-called medium-sized grain) and / or a fine-grained refractory component (so-called flour) and / or a fine-grained refractory component (so-called fine grain), characterized in that the mass is carbon-free and comprises a refractory boron-containing, nitrogen-free component.

Description

The invention relates to unshaped refractory products, in particular refractory concrete, with non-oxide components.

Refractory unshaped products are one of the high-revenue product areas for the steel industry. The amount of unshaped products in refractory production in the EU is currently around 43%. Japan is a pioneer in this regard, where the mass share is almost 60%. The proportion of unshaped refractory materials on the total production of refractory materials is over in the US 55%. Due to the clear technical and economic Refractories are gaining increasing advantages in industry Meaning and oust stone deliveries in many areas.

The main material group of the unshaped products are refractory concretes (refractory concretes). Refractory concretes are mixtures of refractory aggregates and Binders, usually delivered dry and after the addition of Water or other liquid processed. They are installed by casting with vibration, casting without Vibration (self-flow), by poking or, if necessary, by pounding. binding and hardening take place without heating. After hardening, Drying and heating up results in a furnace lining, which is compared with fireproof masonry is particularly low in gaps and is therefore also called "monolithic" will (3). Prefabricated parts can also be made from refractory concrete that are usually thermally pretreated or prebaked.

The usual modern liquefied ones Refractory concrete with its low mixing water requirement (up to this to 3.5% by weight) contain aggregates with grain sizes up to 10 mm, a small proportion of calcium aluminate cement (3-5% by weight) very finely Additives such as microsilica and / or clays of different primary crystal sizes (more specific Surface) and fineness, liquefier and setting regulator. Low-cement vibration refractory concrete with one need correct grain structure a water addition of 3.5 to 6 wt .-%. In the case of self-flowing refractory concrete the water addition is in the range of 4.5 to 7% by weight.

The calcium aluminate cement used as a binder in the hydraulically bound refractory concretes often represents the weakest link in the structure of the refractory concretes. The reason for this is the relatively low-melting eutectics in the CaO-Al ₂ O ₃ -SiO _{2 system} . In order to reduce these negative effects, many efforts have been made to reduce the cement content. As a result, low-cement refractory concretes or refractory concretes with an extremely low cement content were developed, see above. Parallel to the technological development of refractory concrete based on calcium aluminate, the search for new binder systems to replace calcium aluminate cement continues. The technologically relevant developments are:
In basic concretes - Mg (OH) ₂ and barium aluminate cement Active Al ₂ O ₃ . Its use improves concrete properties such as resistance to temperature changes (TWB) and fracture toughness.
Combination of microsilica with active Al ₂ O ₃ - this leads to the formation of mullite and thus to the improvement of the thermomechanical properties and TWB
Phosphate binding, primarily based on monoaluminum phosphate
water glass
resins

Various additives are used to improve the properties of the refractory concrete and its application behavior. For example, the addition of steel fibers that have a positive influence on mechanical strength and TWB is widespread (Genrong, L .; Hongliang, Z .: Influence of stainless steel fiber addition on flexural strength and thermal shock resistance of refractor castables. Int. Coll. Aachen , 1992). A ZrO ₂ and / or Cr ₂ O ₃ addition in turn increases the corrosion resistance (Boquan, Z .; Hongxi, Z .: Study on slag resistance of magnesia / zirconia-based castables. Stahl Eisen (2001), pp. 68-70; Miyaji, T .; Sakamoto, S .; Kudo, E .: Role of Cr ₂ O ₃ in Al ₂ O ₃ -Cr ₂ O ₃ castables for waste melting furnaces. Taikabutsu Overseas 22 (2002) 2, pp. 118-121 ).

The use of monolithic refractory linings has the following advantages:
Possibility of mechanizing the delivery and thus reducing the assembly time
Lack of joints that accelerate penetration of the lining and thus corrosion
Improve steel cleanliness
Reduction of delivery costs by up to 50%
Reduction of specific consumption

Among all unshaped refractories the fire concrete and gate locking compounds are suitable for mechanization and automation of delivery best. The ramming masses and plastic masses, which also belong to the group of unshaped products not so cheap in that regard. Modern refractory concrete achieves property values that those of Exceed refractory bricks can.

The advantages of using monolithic infeeds represent a great incentive for their increased use in practice, both in technical and economic terms. In the meantime Unshaped refractory products and the prefabricated components made from them have been introduced in practically all areas of application of refractory materials and sometimes replace the refractory molded materials or are alternative materials. In the iron and steel industry as the largest buyer of refractory products, the consumption of refractory concrete is also greatest. Apart from converters, there is hardly a plant in the entire production line in which no unshaped refractory products are used.

This development demands from the Refractory industry the development of new more powerful Materials and technologies. One of the most important demands and Challenges in the manufacture and use of a monolithic Refractory lining is hiring one if possible low mixing water content. A too high water content leads to Deterioration of porosity and the strength of the refractory concrete. In addition, drying is one monolithic brick lining a very complex and sometimes complicated undertaking. In the case of an improper tour, you can major damage e.g. due to material explosion due to excessive water vapor pressure occur. So is the reduction of the mixing water content from this point of view one of the goals of the further development of the Refractory concretes.

The most important task is that Improve corrosion resistance unshaped products, in particular refractory concrete. castables are usually characterized by good corrosion resistance out. Among other things, due to a small pore diameter especially in self-fluxing Fireproof conditional. In many areas of application e.g. in the But this is still not enough for the steel industry, so that one for opportunities looking for further improvement. One of them is integration into the material structure the carbon content. Graphite is primarily used and soot. Similar to in the case of shaped stones, the carbon phase brings a considerable Increase in corrosion resistance. Due to the poor wettability by water, however, larger amounts of carbon not just put it in a fire concrete. Carbonaceous Need concrete even higher ones Mixing water quantities, but what the difficulties described above entails drying. There is a certain remedy here Use of surface active Substances. Mostly unsolved So far, the protection of carbon from burnout is over the structure a fire concrete.

After carbon oxidation arise in the material structure Pores that affect corrosion resistance. The usual in molded MAGCARBON (magnesia carbon) stones metallic antioxidants can only be used to a limited extent. Since the Concrete suspensions can have a basic character Metal powder with the ingredients and additives dissolved in the mixing water react. The resulting hydrogen poses a potential hazard (Hara, T .; Yasuda, N .; Sugiyama, K .; Shimizu, I .: Gas evolution of silicon-containing castables. Taikabutsu Overseas 22 (2002), 2, 114-117).

Against this background, it is the Object of the present invention, refractory unshaped masses in particular Refractory concrete available to make the one, in comparison to conventional products, clear improved corrosion resistance have and on an industrial scale and can be manufactured economically.

The task is solved by a refractory mass containing a coarse-grained refractory component (so-called coarse grain) and / or a medium-grain refractory component (so-called medium grain) and / or a fine-grained refractory component (so-called flour) and / or a fine-grained refractory component (so-called fine grain) characterized in that the mass is carbon-free and comprises a refractory boron-containing, nitrogen-free component.

Carbon-free means in the sense the present invention that no unbound carbon, e.g. in the form of graphite, soot and the like, present in the material is. The invention thus also includes refractory masses and materials, made using a carbonaceous binder, e.g. Resin, Tar, pitch are made. Even masses with shares in chemical bound carbon, e.g. in refractory carbides, e.g. Silicon carbide are part of the invention.

All typical, oxidic and non-oxidic, acidic and basic raw materials, or their combination, are used as coarse-grained, medium-grained, fine-grained and fine-grained refractory components. Basic metal oxides such as sintered, melted magnesia, sintered, melted spinel, sintered dolomite, sintered lime, olivine or forsterite are particularly preferred. Masses based on Al ₂ O ₃ with variable SiO ₂ and / or SiC fractions are also advantageous. Combinations of these raw materials can also be present.

A particularly suitable fire-resistant boron-containing, nitrogen-free component is a compound selected from the group boron carbide B ₄ C, refractory borides and their mixtures. Refractory borides are preferably CaB ₆ , TiB ₂ , and ZrB ₂ . It has been shown that a mixture of several boron-containing, nitrogen-free compounds can also be used advantageously. The boron-containing, nitrogen-free compound is preferably present in amounts from 0.1 to 30% by weight, particularly preferably from 0.5 to 10.0% by weight.

The composition according to the invention preferably comprises an additive. In the context of the invention, additives are preferably metal powders, non-oxides such as nitrides, carbides, silicides, oxynitrides, oxycarbides, metal fibers, plastic fibers and carbon fibers, preferably the metal powders Al, Mg, Si and non-oxides such as SiC, AlN , Si ₃ N ₄ , AlON, SiAlON. The additives are preferred in amounts of 0.5 to 30 wt .-%.

Below are coarse-grained in the sense of the present Invention preferably grain sizes ≥ 1 mm, especially preferably 1-10 mm to understand. Grains of 0.2 to <1 mm are preferred as the middle grain 0.2 to 0.5 mm, for use.

Below are fine-grained in the sense of the present Invention preferably grits 0.02 to <0.2 mm, to understand particularly preferably 0.02 to 0.1 mm. This grain fraction is usually referred to as flour in technical parlance.

Reactive refractories are the finest grain Components with an average grain size <15 μm, preferably <5 μm to understand. For example, calcined alumina, reactive alumina, finely ground, refractory raw materials, microsilica, refractory clay, Clay.

The unshaped refractory compositions according to the invention can be bound hydraulically, chemically or ceramic. To this All binder systems typical in refractory technology are suitable for this purpose. Hydraulic binding is preferably carried out by means of a refractory cement preferably a calcium aluminate cement in an amount up to 25% by weight, preferably 1 to 10% by weight, for use.

Depending on the chemical composition of the refractory raw materials, all liquid binders common in the refractory industry are suitable for chemical bonding, ie as binders, both water-free and water-containing, for example resins, tar, pitch. Lignin sulfonate (sulfite liquor), polyvinyl alcohol, phosphates, MgSO ₄ solution, water glass, levulinic acid. The amount of binder is preferably between 0.1 and 50% by weight, preferably between 1 and 10% by weight.

Ceramic bond arises in the masses according to the invention when heating up to temperatures> 700 ° C. This The process is supported by the use of fine grain fractions.

Depending on the type of binding the masses with up to 40 wt .-%, preferably <10 wt .-%, water turned on.

To reduce the water content and / or to improve the rheological properties of the masses, is the use of different additives, e.g. condenser, Setting regulator, dispersant, advantageous. The share of this Additive is in the range up to max. 5% by weight, preferably <1.5% by weight.

The coarse-grained component is preferably located in quantities <90 % By weight particularly preferably in amounts of 15 to 80% by weight.

The medium grain component is preferably in quantities <40 % By weight, particularly preferably in amounts of 3 to 20% by weight.

The fine-grained component is preferably in quantities <95 % By weight, particularly preferably in amounts of 5 to 80% by weight.

The fine-grained component is preferably in amounts of <50 % By weight, particularly preferably in amounts of 0.1 to 35% by weight.

To enhance the effect of the boron-containing components or to improve the material properties, special metallic and / or non-oxidic substances can be added to the refractory compositions according to the invention. These are preferably compounds selected from the group of metal powders Al, Mg, Si and non-oxides such as SiC, AlN, Si ₃ N ₄ , AlON, SiAlON.

For the purpose of reinforcing and / or improving the structure the drying process is also an addition of metal fibers from Advantage.

The carbon-free refractory compositions according to the invention are characterized by a number of positive properties. conditioned due to the relatively high thermal conductivity of boron additives they have an improved compared to masses without additives Thermal shock resistance.

Show due to the high affinity for oxygen the boron-containing compounds have good oxidation resistance in the material structure. This Behavior is achieved by forming passivation layers on the Material surface, which make contact with oxygen more difficult. The added boron-containing substances become bad from ionic melts wetted, which limits the wetting by molten slag. This improves the corrosion resistance and contributes to the increase the durability of these new refractory materials.

Corrosion resistance the new masses also have a positive effect on the formation of fireproof, stable Oxides due to the reaction of the borides with oxygen. Since the Reactions with a partially considerable Volume increase, lead they condense the structure of the material, which in turn improves it corrosion resistance and contributes to the strength of the delivery.

Borides and boron carbide are in the Able to reduce the critical components of metallurgical slags and thereby their aggressiveness to reduce.

A high compression of the material structure is important for the corrosion resistance of the refractory materials. This can be improved, among other things, by an appropriate grain distribution. The following grain structure has proven to be advantageous for the offset according to the invention:
Coarse grain component: <90% by weight> 0.2 mm. Portions of 15 to 80% by weight of the grain fraction 1-10 mm are preferred.
Medium grain component: <40% by weight of the grain fraction 0.2 to 1 mm. Portions of 3 to 20% by weight of the grain fraction 0.2-0.5 mm are preferred.
Fine grain component: <95% by weight <0.2 mm, preferably 5 to 80% by weight
Fine grain component: <50% by weight <15 μm, preferably 0.1 to 35% <5 μm
Boron-containing, nitrogen-free compound: 0.1 to 30% by weight -325 mesh (<45 μm), preferably 0.5 to 5% by weight.

The production of the refractory compositions according to the invention preferably at the refractory manufacturer or on-site at the refractory user in the following steps:

Production of a homogeneous Mixture of the above refractory components in the above parts by weight.

Addition of a binder and / or Additives and / or mixing water and further homogenization of the Mince.

Addition of aggregates and others Homogenization of the batch. If necessary, the mixture becomes substances added, which take on certain functions in the finished masses. Examples are metal powder and non-oxide materials such as carbides, Nitrides, silicides, metal fiber, plastic fiber, carbon fiber, which resistance to oxidation, Strength drying behavior, corrosion resistance and resistance to temperature changes further improve the material.

The homogenized mixture is ready for use and can be done using techniques familiar in refractory technology, e.g. To water, Vibrate, spray, gate lock, pound, etc., into a monolithic Refractory lining or a functional mass processed become.

From the refractory compositions according to the invention can prefabricated components are also manufactured. To do this, do the same as above described manufactured masses in a metal, or wood, or Brought plastic mold. By subsequent vibrating, pounding, The mass can be pressed additionally be compressed. After curing the component is shaped and dried at 80 to 700 ° C and / or annealed. If necessary, the dried or tempered Component to be burned. The firing conditions depend essentially on the chemical and mineralogical composition of the refractory mass as well as the shape and geometry of the component. After drying or tempering or The prefabricated components according to the invention are fire ready for use.

The unshaped refractory compositions according to the invention can in the ovens and plants of the non-ferrous industry, steel industry, cement industry, Glass industry waste incineration plants etc. are used.

The manufacture and the properties of the products according to the invention will be explained below with some examples. With the offsets of the Examples, as is customary in ceramics, a "basic offset" is first produced, which already gives 100. In order to obtain variations, additives are added to this basic offset added in different amounts. Get% of their data to the 100 value of the basic approach.

example 1

4 self-flowing corundum concretes with variable B ₄ C components were produced. Their composition and grain structure were as follows:

All raw materials and additives are under the names given by ALCOA Germany available.

The raw materials and additives were mixed with variable B ₄ C components, -325 mesh (<45 μm), from Wacker Chemie GmbH, Munich, and mixing water. It was shown that with increasing B ₄ C content the amount of water required. becomes lower. Standard test specimens 50 × 50 mm were produced from the masses. The test specimens were produced by pouring them into a plastic mold, curing them at room temperature for 24 hours, and then drying them at 110 ° C. for 24 hours. The dried test specimens were characterized by the determination of the cold compressive strength, KDF, (DIN EN 9935), bulk density, RD, (DIN EN 993) and open porosity, OP, (DIN EN 993). The results obtained are summarized in the table below.

The results show that the amount of mixing water in the concretes according to the invention can be reduced by adding boron carbide. Corundum concrete with a relatively high B ₄ C content also has good property values.

Example 2

A bauxite refractory concrete was made with the following composition:

In the sintered bauxite (sinter bauxite) it is a commercially available Product. Sintered corundum T60, calcined alumina CTC 50, alumina cement CA 270 and additives can e.g. about can be obtained from ALCOA Germany.

2% by weight of boron carbide from Wacker Chemie GmbH, Munich, were added to the mixture. The mixture was then made into a concrete with 5.7% by weight of mixing water. Cylindrical test crucibles for testing corrosion resistance were made from the concrete. As shown in Example 1, the production was carried out by pouring the liquefied concrete into a plastic mold. The casting mold was constructed in such a way that a round recess with a diameter of 30 mm and a depth of 10 mm was created on one side of the test cylinder. The depression was used to hold a test metal melt. After curing at room temperature, 24 h and drying at 110 ° C, 24 h, 20 g of pure aluminum powder were placed in the well of the crucible. The crucible was then aged at 800 ° C for 72 hours in an electric oven with no air. After cooling, the test crucible was examined for any signs of corrosion, such as chemical reaction with the metal and infiltration of the metal into the material structure. For comparison, a crucible test was made from the same refractory concrete without the addition of B ₄ C and examined under the same conditions. The bauxite B ₄ C refractory concrete according to the invention showed no infiltration and a significantly better corrosion resistance compared to the Al melt compared to the material without boron carbide. Example 3

The spinel raw materials are a sintered Al ₂ O ₃ -rich magnesium aluminum spinel, which is available from

ALCOA Germany can. Also the other components, calcined spinel / alumina CTC 55, alumina cement and additives can be obtained from this company become.

3% by weight of zirconium boride from Wacker Chemie GmbH, Munich, were added to the mixture. The mixture was then made into a concrete with 5.2% by weight of mixing water. Cylindrical test crucibles for testing corrosion resistance were made from the concrete. For this purpose, the concrete was filled into a plastic mold and then compacted on a vibrating table. The shape was constructed in such a way that a round recess with a diameter of 30 mm and a depth of 10 mm was created on one side of the test cylinder. The deepening was used to hold a test slag. After curing at room temperature / 24 h and drying at 110 ° C / 24 h, 20 g of a ladle slag from the steel industry were placed in the well of the crucible. The crucible was then fired in air at 1500 ° C for 6 hours in an electric furnace. After cooling, the test crucible was examined for any signs of corrosion, such as chemical reaction with the slag and its infiltration into the material structure. For comparison, a crucible test was made from the same refractory concrete without ZrB ₂ and examined under the same conditions. The spinel concrete according to the invention with ZrB ₂ addition showed a significantly better infiltration and corrosion resistance compared to the material without addition.

Example 4

A chemically bound, basic mass with the following composition was produced:

It is the magnesia sinter a sintered high purity magnesia, e.g. from NEDMAG. Titanium boride (e.g. titanium diboride) can e.g. from Wacker Chemie GmbH, Munich can be obtained.

The components were homogenized dry and subsequently by mixing with 12% by weight Na water glass to form a sprayable mass edited. The mass was burned on a magnesia stone applied and at 1550 ° C Burned for 2 hours. After the fire, the mass adhered very strongly to the stone surface good and showed very good resistance to oxidation and corrosion across from a steel converter slag. The mass is suitable for carrying out both cold and hot repairs of refractory deliveries.

Example 5

Al ₂ O ₃ -SiC ramming mass with phosphate bond

A chemically bound Al ₂ O ₃ -SiC mass with the following composition was produced:

Sintered corundum raw materials can be from can be obtained from ALCOA Germany.

A product from ESK-SiC GmbH was used as silicon carbide powder and a commercially available product was used as silicon powder. The components were dry-homogenized with 3% by weight of ZrB ₂ (from Wacker Chemie GmbH, Munich) and then by mixing with 6.5% by weight of a monoaluminum phosphate solution (50% strength) from BUDENHEIM prepared a ramming mass. Test specimens with a diameter of 50 mm and a height of 50 mm were produced from the mass by stamping in a steel mold. A round recess with a diameter of 30 mm and a depth of 10 mm was pressed in on one side of the test cylinder during the pressing process to accommodate the test slag. In the recess. 20 g of a steel converter slag were placed. The crucible was then fired at 1500 ° C in an electric furnace for 6 hours in air. For comparison, a crucible was made from the offset without ZrB ₂ and tested under the same conditions. After cooling, the test crucibles were examined for any signs of corrosion, such as chemical reaction with the slag and its infiltration into the material structure. The Al ₂ O ₃ -SiC ramming mass with ZrB ₂ showed a much better infiltration and corrosion resistance compared to the material without addition.

Example 6

A self-flowing corundum concrete B ₄ C and steel fiber additive with the following composition was examined.

The sources of supply of the raw materials, Additives and additives are as mentioned in the previous examples.

The raw materials and additives were premixed dry with 2.0% by weight of steel fibers (D = 0.3mm, length = 20mm) and then processed into a concrete with 6.7% by weight of mixing water. Standard test specimens 50 × 50 mm were made from the concrete. The test specimens were produced by pouring them into a plastic mold, curing them at room temperature for 24 hours, and then drying them at 110 ° C. for 24 hours. The dried test specimens were characterized by the determination of the cold compressive strength, KDF, (DIN EN 9935), bulk density, RD, (DIN EN 993), open porosity, OP, (DIN EN 993) and temperature change resistance TWB (DIN EN 993-11). For comparison, test specimens without the addition of steel fibers were produced and examined under the same conditions. After drying, the test specimens had the following characteristic values:

The results show that through the steel fiber additive the thermal shock resistance of the concretes according to the invention can be improved.

Claims (15)

Refractory mass containing a coarse-grained refractory Component (so-called coarse grain) and / or a medium-grain refractory component (so-called medium grain) and / or a fine-grained refractory component (so-called flour) and / or a fine-grained refractory component (so-called fine grain) characterized in that the mass is carbon-free and comprises a refractory boron-containing, nitrogen-free component. Composition according to claim 1, characterized in that the coarse-grained, middle grain, fine-grained, and fine-grained refractory component selected is from the group of, oxidic and non-oxidic, acidic or basic raw materials. Composition according to claim 2, characterized in that the refractory components are selected from the group of basic metal oxides such as sintered, fused magnesia, sintered, melted spinel, sintered dolomite, sintered lime, olivine or forsterite, the masses based on Al ₂ O ₃ a variable SiO ₂ and / or SiC component and their combinations. Composition according to one of claims 1 to 3, characterized in that that the nitrogen-free component containing boron is selected from the group boron carbide, refractory borides and mixtures thereof. Composition according to one of Claims 1 to 4, characterized in that that the boron-containing, nitrogen-free component in amounts of 0.1 up to 30 wt .-% is present. Composition according to one of claims 1 to 5, characterized in that that it also comprises an additive that is preferably selected from the group metal powder, non-oxides such as e.g. Nitrides, carbides, silicides, Oxynitrides, oxycarbides, metal fibers, plastic fibers and carbon fibers. Composition according to claim 6, characterized in that the additive is present in amounts of 0.5 to 30 parts by weight. Composition according to one of claims 1 to 7, characterized in that that they also have a binder, preferably one in the refractory industry Common liquid Binder includes. Composition according to one of claims 1 to 8, characterized in that that they also contain an additive, preferably selected from the group of plasticizers, Setting regulator and dispersant includes. Composition according to one of claims 1 to 9, characterized in that that the coarse-grained refractory components in quantities <90 % By weight is present. Composition according to one of claims 1 to 10, characterized in that the medium grain refractory component is present in amounts of <40 wt .-%. Composition according to one of claims 1 to 11, characterized in that that the fine-grained refractory component is present in amounts of <95 wt .-%. Composition according to one of claims 1 to 12, characterized in that that the finest grained refractory component is present in amounts of <50 wt .-%. Composition according to one of claims 1 to 13, characterized in that it also contains water preferably comprises in an amount of up to 40% by weight. Composition according to one of claims 1 to 14, characterized in that that they also contain additives such as Condenser, setting regulator, Dispergiermittelumfasst.