Fire-resistant articles and compositions

Abstract

The present invention provides a refractory article for use in a feeder system in metal casting, and a composition for making the refractory article, the composition comprising a particulate refractory material, an oxidizing fuel, an oxidizer, a sensitizer, and a binder, the composition comprising 0.5 to 5 weight percent CaSO. 4 Includes.

Description

Technical Field

[0001] The present invention relates to refractory articles for use in metal casting and compositions for use in the manufacture of such refractory articles. Specifically, the present invention relates to fluorine-free compositions and refractory articles for use in metal casting, such as feeder sleeves.

Background Art

[0002] In a typical casting process, molten metal is poured into a preformed mould cavity that defines the shape of the casting. When the molten metal cools and solidifies, it shrinks and forms shrinkage cavities, resulting in unacceptable defects in the final casting. This is a well-known problem in the casting industry, and it is addressed by using feeders or risers integrated into the mould. Each feeder has an additional (usually sealed) volume or cavity that communicates with the mould cavity and allows molten metal to enter the feeder cavity from the mould cavity during casting. During solidification of the casting, the molten metal in the feeder cavity flows in the reverse direction into the mould cavity to compensate for the shrinkage of the casting.

[0003] For the casting to be properly fed and voids formed during metal shrinkage to be filled, the metal in the feeder cavity needs to remain molten for longer than the metal in the mould cavity. For this reason, feeders typically have a feeder sleeve made of a highly heat-insulating refractory material to reduce heat loss from the metal in the feeder cavity and keep it molten for longer. Also, exothermic feeder sleeves may be provided to actively heat the metal in the feeder cavity.

[0004] A heat-generating sleeve utilizes the thermite reaction, in which an oxidizing fuel (usually a metal such as aluminum) is oxidized by an oxidizing agent (typically iron oxide, manganese dioxide, potassium nitrate, or a combination thereof), generating heat at a temperature similar to that of molten metal. The thermite reaction is initiated by the heat of the molten metal as it enters the riser cavity and comes into contact with the fuel and oxidizing agent.

[0005] Heat-generating riser sleeves offer the advantage of allowing the use of significantly smaller risers for a given riser application or casting type. This is beneficial in that it reduces the amount of metal wasted in the riser, reduces the complexity of the castings that can be manufactured, and reduces the number of castings that can be manufactured per mold. Much effort has been put into optimizing heat-generating riser sleeves over the years. Key parameters commonly considered when evaluating new heat-generating sleeves include ignition time and maximum achievable temperature (T). max These are the energy required to initiate the exothermic thermite reaction, and the duration of the exothermic reaction (burning time). Increasing the amount of fuel and / or oxidizer does not necessarily increase the duration of the exothermic reaction. In many cases, not all of the fuel is consumed, so increasing the amount of fuel or oxidizer may not be economical or practical. To improve the efficiency of exothermic sleeves, sensitizers or initiators have been developed that reduce the energy required to initiate the exothermic thermite reaction.

[0006] In the foundry industry, fluoride-based initiators / sensitizers such as potassium cryolite (K3AIF6) and sodium cryolite (Na3AIFe6) are widely used and recognized as the most effective and practical sensitizers. However, there are environmental and technical problems due to the contamination of mold sand by fluoride-containing sleeve residues. Foundries are facing increasing problems with the disposal of waste sand containing fluoride in both dry waste and water-leaching components, resulting in rising costs for controlled disposal. Another problem is that the accumulation of fluoride residues in recycled mold sand reduces the refractory properties of the sand, leading to the formation of defects (known as "fish eyes") on the surface of the castings.

[0007] U.S. Patent No. 6,360,808 discloses a composition in which the reduction of fluoride levels is achieved by using aluminum dross as both an aluminum and fluoride source. U.S. Patent Publication No. 2009 / 0199991A1 discloses a metallocene-containing composition that can reduce fluoride levels. U.S. Patent No. 5,180,759 discloses the use of fluorinated organic polymers to reduce the total fluoride content of exothermic compositions. European Patent No. 1,543,897,B1 and U.S. Patent No. 6,972,059,B1 both disclose fluoride-free compositions. These use magnesium as an initiator, but magnesium is highly reactive, making the production and processing of exothermic mixtures difficult. CA974764 discloses a hot topping composition which, by reaction, forms a protective cover on the exposed surface of a casting ingot. CN106631051 discloses fire-resistant bricks or wall tiles for use as fire-resistant insulation materials and compositions for manufacturing them. RU2163579 discloses compositions for exothermic mortar used in the manufacture of fire-resistant walls.

[0008] In the case of riser sleeves manufactured via slurry routes, the need for insoluble materials makes it difficult to obtain technically feasible alternatives to fluoride sensitizers. Certain Group II chlorides that could potentially serve as substitutes for insoluble fluoride salts may exhibit the required insolubility, but are known to have low effectiveness as sensitizers and cannot meet the required performance requirements.

[0009] This invention was developed with these problems in mind. [Overview of the project]

[0010] In a first aspect of the present invention, a composition for producing a refractory article for use in metal casting is provided. The composition comprises a particulate refractory material, an oxidisable fuel, an oxidant, a sensitizer, and a binder. The composition contains 0.5 to 5% by weight of CaSO4.

[0011] In some embodiments, the fire-resistant composition contains 0.5 to 3% by weight or 1 to 2% by weight of CaSO4. [Modes for carrying out the invention]

[0012] The composition of the present invention comprises calcium sulfate (CaSO4), which acts primarily as a sensitizer and also as an oxidizing agent. The use of CaSO4 as a sensitizer shortens the ignition time of the exothermic thermite reaction and / or increases combustion efficiency, thus reducing or eliminating the use of fluoride sensitizers. Reducing the amount of fluoride sensitizer reduces fluorine contamination in the mold sand, thereby mitigating environmental and cost issues associated with the treatment of fluorine-contaminated sand and preventing the accumulation of fluorine in recycled mold sand, which can cause casting defects. In some embodiments, the composition comprises an oxidizing agent and / or a sensitizer in addition to calcium sulfate.

[0013] In the context of this invention, the terms "sensitizer" and "initiator" may be used interchangeably and will be understood to refer to substances that reduce the energy required to initiate the exothermic thermite reaction.

[0014] In some embodiments, the composition contains a sensitizer other than calcium sulfate in amounts of 4.0% by weight or less, 3.5% by weight or less, 3% by weight or less, 2.5% by weight or less, 2% by weight or less, 1.5% by weight or less, 1.25% by weight or less, 1.0% by weight or less, 0.5% by weight or less, or 0.25% by weight or less.

[0015] In some embodiments, the composition contains fluorine in amounts of 4.0% by weight or less, 3.5% by weight or less, 3% by weight or less, 2.5% by weight or less, 2% by weight or less, 1.5% by weight or less, 1.25% by weight or less, 1.0% by weight or less, 0.5% by weight or less, 0.4% by weight or less, 0.3% by weight or less, 0.2% by weight or less, 0.1% by weight or less, or 0.05% by weight or less. In some embodiments, the composition is substantially fluorine-free, i.e., the amount of fluorine in the composition is trace or less. Since fluorine compounds can be undesirable for casting quality and environmental reasons, it is preferable to minimize the amount of fluorine in the composition to maintain the desired properties of the thermite reaction.

[0016] In a preferred series of embodiments, the composition contains a water-insoluble fluorine compound. In some embodiments, the composition is fluorine-free or substantially fluorine-free. The inventors have found that water-insoluble fluorine compounds can also act as sensitizers. Water-insoluble fluorine compounds are particularly preferred because, for example, they do not contaminate the mold sand with fluorine (or fluorine compounds) during mold reclamation after the refractory articles formed from the composition have been used in a metal casting process.

[0017] In a preferred series of embodiments, the sensitizer comprises calcium fluoride (CaF2). Calcium fluoride is a water-insoluble mineral that has been found to act as a sensitizer in the thermite reaction. While we do not wish to be bound by theory, calcium fluoride is thought to act at least partially catalytically to prevent the formation of an oxide layer on the aluminum metal. In some embodiments, the sensitizer may include magnesium fluoride (MgF2).

[0018] It will be understood that the term “fluorine” as used herein is intended to mean any compound containing fluorine in ionic or covalent form, such as in the form of a fluoride. In this application, a “fluorine-free” product is a product that contains no fluorine at all, or only trace amounts of fluorine, regardless of its form, i.e., a product that contains neither fluorine nor fluoride.

[0019] The oxidizing agent oxidizes the oxidizing fuel as part of the thermite reaction. In this invention, CaSO4 can act as both an oxidizing agent and a sensitizer, but it will be understood that the term “oxidizing agent” as used herein is used to refer to any oxidizing agent present in a composition other than CaSO4. Suitable oxidizing agents include natural minerals, including iron oxide (Fe2O3, FeO and / or Fe3O4), ferrosilite (FeSiO3), manganese dioxide (MnO2), sodium nitrate (NaNO3), potassium nitrate (KNO3), sodium chlorate (NaClO3), potassium chlorate (KClO3), strontium sulfate (SrSO4), barium sulfate (BaSO4), titanium dioxide (TiO2), copper oxide (CuO), and combinations thereof.

[0020] In some embodiments, the oxidizing agent includes an oxidizing agent that is substantially insoluble in water. A substance is considered substantially insoluble in water if its solubility in water is less than 0.5 g / 100 ml at 20°C. The use of an insoluble oxidizing agent is advantageous because the refractory articles can be prepared from the composition using an aqueous slurry of the solid components and are suitable for production by the core shot method. Examples of oxidizing agents that are substantially insoluble in water include iron oxide, manganese dioxide, copper oxide, strontium sulfate, barium sulfate, and titanium dioxide.

[0021] In some embodiments, the oxidizing agent comprises one or more oxidizing agents selected from the group consisting of iron oxide (Fe2O4 and / or Fe3O4), ferrosilite (FeSiO3), potassium nitrate (KNO3), manganese dioxide (MnO2), titanium dioxide (TiO2), and copper oxide (CuO). In some embodiments, the oxidizing agent comprises a combination of iron oxide (Fe2O4 and / or Fe3O4), ferrosilite (FeSiO3), and potassium nitrate (KNO3).

[0022] In some embodiments, the composition contains an oxidizing agent in an amount of at least 2% by weight, at least 5% by weight, at least 10% by weight, at least 12% by weight, at least 15% by weight, at least 20% by weight, or at least 25% by weight. In some embodiments, the composition contains an oxidizing agent in an amount of 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 12% by weight or less, or 10% by weight or less. In some embodiments, the composition contains an oxidizing agent in an amount of 2-30% by weight, 5-25% by weight, or 10-20% by weight.

[0023] In some embodiments, the oxidizing fuel includes a metal. In some embodiments, the metal is selected from one or more of aluminum, magnesium, silicon, tin, zinc, and their alloys, either alone or in mixtures. In some embodiments, the oxidizing fuel includes aluminum and metallic silicon. Combinations of different oxidizing metals with different reactivity may help to adjust the properties of the thermite reaction (e.g., ignition time, burn time, maximum temperature, etc.). For example, without wishing to be constrained by theory, the inventors of the present invention have found that since silicon has a higher activation energy and also a higher energy output than aluminum, using a combination of metallic silicon and aluminum as the oxidizing fuel may help to balance the properties of the thermite reaction in the absence of a fluoride sensitizer.

[0024] The oxidizing fuel may be in the form of particulate material (e.g., fine powder, coarse powder, grindings or combinations thereof), foil, skimmings, dross or combinations thereof. In some embodiments, the oxidizing fuel comprises a combination of metal foil and particulate metal. In some embodiments, the oxidizing fuel comprises atomised powder, i.e., metal in a very fine powder form. The oxidizing fuel in atomised powder form may be more reactive than other forms of oxidizing fuel. By using the oxidizing fuel in different combinations of forms, the characteristics of the thermite reaction can be adjusted and the balance of these characteristics can be achieved in the absence of fluoride sensitizers.

[0025] In some embodiments, the oxidizing fuel comprises atomised powder, which comprises atomised aluminium, atomised silicon or combinations thereof. In some embodiments, the atomised powder comprises atomised aluminium at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt% or at least 95 wt%. In some embodiments, the atomised powder comprises atomised silicon at least 2 wt%, at least 5 wt%, at least 10 wt%, at least 20 wt%, at least 30 wt% or at least 40 wt%. In some embodiments, the atomised powder comprises 60 - 95 wt% atomised aluminium and 5 - 40 wt% atomised silicon.

[0026] The atomised aluminium powder may have a D90 particle size less than 150 μm, less than 140 μm, less than 130 μm, less than 120 μm, less than 110 μm or less than 100 μm, a D50 particle size less than 80 μm, less than 70 μm, less than 60 μm, less than 50 μm or less than 40 μm, and / or a D10 particle size less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm or less than 10 μm. In some embodiments, the oxidizing fuel comprises atomised aluminium powder having a D90 particle size less than 130 μm, a D50 particle size less than 60 μm, and a D10 particle size less than 20 μm.

[0027] The atomized silicon powder may have a D90 particle size of less than 65 μm, less than 55 μm, less than 45 μm, less than 35 μm, or less than 25 μm. In some embodiments, the oxidizing fuel comprises atomized silicon having a D90 particle size of less than 45 μm.

[0028] In some embodiments, the oxidizing fuel comprises atomized aluminum having a D90 particle size of less than 130 μm and atomized silicon having a D90 particle size of less than 45 μm.

[0029] In some embodiments, the oxidizing fuel comprises at least 20 wt%, at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, or at least 70 wt% of the atomized powder. In some embodiments, the oxidizing fuel comprises 80 wt% or less, 70 wt% or less, 60 wt% or less, 50 wt% or less, or 40 wt% or less of the atomized powder. In some embodiments, the oxidizing fuel comprises 20 - 80 wt%, 30 - 70 wt%, or 40 - 60 wt% of the atomized powder. The exact proportion of the atomized powder in the oxidizing fuel may depend on the types and proportions of the various metals used. For example, if the proportion of silicon is low or not used at all, a higher proportion of atomized aluminum is required.

[0030] In some embodiments, the composition comprises at least 5 wt%, at least 10 wt%, at least 15 wt%, at least 20 wt%, or at least 25 wt% of the oxidizing fuel. In some embodiments, the composition comprises 30 wt% or less, 25 wt% or less, 20 wt% or less, 15 wt% or less, or 10 wt% or less of the oxidizing fuel. In some embodiments, the composition comprises 5 - 30 wt%, 10 - 25 wt%, or 15 - 25 wt% of the oxidizing fuel.

[0031] The composition includes a particulate refractory material that acts as a filler and provides insulating properties. The particulate refractory material may be in the form of a powder, granules, fibers, or any combination thereof. In some embodiments, the particulate refractory material is selected from silica, olivine, alumina, aluminosilicate (including chamotte), pumice, magnesia, chromite, zircon, and combinations thereof.

[0032] Preferably, the composition contains particulate refractory material in an amount of at least 30% by weight, at least 35% by weight, at least 40% by weight, at least 45% by weight, or at least 50% by weight. In some embodiments, the composition contains particulate refractory material in an amount of 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, or 50% by weight or less.

[0033] Additionally or alternatively, particulate refractory material may be 1 g / cm³. 3 Less than 0.5 g / cm³ 3 This includes lightweight materials having a density of less than 1.5. Such lightweight materials are particularly useful for providing insulation. Suitable lightweight materials include perlite, diatomaceous earth, calcined rice husks (rice husk ash), fire-resistant fibers, fly ash floaters (hollow microspheres), cenospheres, other natural or synthetic hollow spheres (such as alumina, alumina silica, or aluminosilicate), and combinations thereof.

[0034] Suitable binders for use in the present invention include resins (e.g., phenol-formaldehyde resin or urea-formaldehyde resin), gums (e.g., gum arabic or xanthan gum), sulfite lye, starch, acrylic dispersions, colloidal silica, colloidal alumina, and combinations thereof. In some embodiments, the binder includes a combination of resin and starch. In some embodiments, the binder may include two or more types of starch. In some embodiments, one or more types of starch may include wheat starch, potato starch, corn starch, waxy maize starch, rice starch, soybean starch, tapioca starch, modified starch, cationic starch, heat-swellable starch, and combinations thereof. In some embodiments, one or more types of starch may be partially or entirely pre-gelatinized. In a series of embodiments, one or more starches include a combination of pre-gelatinized starch and pre-gelatinized starch, and it is preferable that both are wheat starch.

[0035] In a preferred series of embodiments, the binder is non-toxic and / or biodegradable. Starch is particularly preferred because it decomposes readily and does not contaminate the mold sand after use. The starch can be washed off, for example, during the regeneration of the mold sand, and does not require subsequent professional water treatment.

[0036] In some embodiments, the composition contains a binder in an amount of 0.5 to 5% by weight, or 1 to 4% by weight, or 1.5 to 3.5% by weight, or 2 to 3% by weight.

[0037] In some embodiments, the composition further comprises a carrier fluid, such as water. Preferably, the composition comprises a carrier fluid in which other components of the composition do not dissolve, so as to generate a slurry of suspended solid components for manufacturing refractory articles.

[0038] A second aspect of the present invention provides a refractory article for use in a feeding system in metal casting. The refractory article is formed from a composition described herein.

[0039] Fire-resistant articles can be manufactured by various methods, including slurry methods (vacuum forming) or core shooting methods (blowing or ramming). The choice of binder may depend on the method by which the fire-resistant article is manufactured.

[0040] In some embodiments, the refractory articles are heat-generating refractory articles. The refractory articles may include many products used in foundries to assist in the supply of risers to metal castings, such as riser sleeves (also simply known as “risers” or “sleeves”), and articles of other shapes that cover parts of the casting or mold assembly (e.g., riser boards, profile cores, heat-generating padding, and combinations of sleeves and cores).

[0041] In some embodiments, the fire-resistant article is a riser sleeve. The shape of the riser sleeve is not particularly limited. The riser sleeve may have a circular or elliptical cross-section, parallel or inclined sides, and may be openable and closable. In embodiments where the riser sleeve is closed, it may have a dome-shaped or flat cover. The riser sleeve may be cylindrical (i.e., having a circular cross-section and parallel sides) or truncated cone (i.e., having a circular cross-section and inclined sides).

[0042] In some embodiments, the fire-resistant article is a riser board, which may be in the form of a bonded mat. The bonded mat is wrapped around a riser pattern or deployed within a conventional riser sleeve. Alternatively, the riser board can be used as a riser cover placed over an open sleeve, and the shape of the board is determined by the shape of the riser sleeve. Typically, the riser cover has a circular or elliptical cross-section.

[0043] In some embodiments, the fire-resistant article is a Williams core (also known as a Williams wedge). The Williams core is an article with a sharply pointed edge, typically conical or wedge-shaped, and is positioned at the top of the closing sleeve to improve and stabilize the riser effect. The Williams core may be formed integrally with the riser sleeve or may be manufactured separately and then fixed inside the sleeve.

[0044] In some embodiments, the refractory article may include a combination of a sleeve component and a breaker core component that contacts a casting surface, the casting surface having a profile shape specifically designed to conform to the shape of a desired casting.

[0045] In some embodiments, the refractory article may include a profile shape known as a pad, which can be used to increase the feeding distance of the sleeve or to delay or control the solidification time of the casting beneath the pad by utilizing the pad's heat-generating properties. In one embodiment, the pad is used in combination with a sleeve component to form a single unit.

[0046] It will be understood that any of the optional features and embodiments described in relation to the first aspect may also be applied to the composition of the second aspect.

[0047] <Experimental Procedure> Standard cylindrical specimens were prepared using the Georg Fischer (+GF+) method. Green (uncured) riser sleeves were first prepared using the slurry method. Next, the green riser sleeves were finely chopped and thoroughly mixed using a flat-blade paddle mixer until the composition was uniform. A sample of the mixture was loosely packed into a cylindrical precision specimen (inner diameter 50 mm), placed on a +GF+ sand rammer (Type SPRA), and the mixture was compressed with three ramming motions. After confirming that the height was within tolerance marks, the specimen was removed using an ejector (stripping post). The specimen was then cured in a drying oven at 160°C for 90 minutes. The dimensions of the resulting cylindrical specimen were 50 mm x 50 mm.

[0048] The overall composition of the test specimen (on a solids basis) is as follows: Calcium sulfate: 0.5-5% by weight Fluorine-based sensitizer: 0-2% by weight Iron oxide (Fe3O4) oxidizing agent: 7-10% by weight Oxidizing agent containing potassium nitrate and ferrosilite: 10-20% by weight Aluminum: 10-20% by weight Silicon: 1-5% by weight Binder: 0.5-5% by weight High-density fire-resistant filler: 40-60% by weight Low-density fire-resistant filler: 0-5% by weight

[0049] Aluminum contains a mixture of aluminum foil, powder, and pulverized material. Silicon contains atomized silicon powder. High-density refractory fillers contain a mixture of sand, chamotte, pumice, and aluminosilicate materials, while low-density refractory fillers contain cenospheres.

[0050] The ratio of high-density refractory filler to low-density refractory filler was adjusted as appropriate so that the balance of all components totaled 100% by weight.

[0051] <Ignition time and burn time> Using an in-house testing apparatus (Amitec), a standard test specimen was placed on an electrically heated silicon carbide (SiC) plate, preheated, and maintained at 1400°C. Ignition time was measured from the time the test specimen was placed on the heating device until ignition (in seconds). Immediately after ignition, the test specimen was transferred to a sand bed and left there until it burned out. Burning time was measured as the time from ignition to the end of burning (reported in seconds).

[0052] The desirable ignition time and burn time vary depending on the application. A short ignition time is particularly useful for small riser sleeves where it is essential to supply riser molten metal to the casting very quickly. In large riser sleeves, a long burn time is useful because the casting is supplied for a long time, and the ignition time is less important.

[0053] <Maximum temperature and time exceeding 1150℃> An Al2O3 protective tube was inserted into the Green standard test specimen to a depth of 25 mm at its precise center. The test specimen was then dried, and a thermocouple was connected to a plotter inserted into the protective tube. The test specimen was ignited, and the maximum temperature reached (Tmax) and the time above 1150°C (t>1150°C) were recorded by the plotter.

[0054] In casting applications, riser sleeves serve a useful purpose only when the metal within the riser remains in a liquid state. Since the liquidus temperature of ferrous metals is in the 1150°C range, t > 1150°C can be a more accurate indicator of riser sleeve performance than burning time.

[0055] <Example 1> A series of test specimens were prepared and tested using compositions with varying proportions of fluorine-based sensitizers, as described above. The test results are shown in Table 1 below.

[0056] [Table 1]

[0057] The results indicate that compositions containing calcium sulfate achieve good exothermic performance even at low levels of fluoride sensitizer. Test specimens prepared using compositions with low fluoride content (E1 and E2) had slightly longer addition times and lower maximum temperatures than compositions with high fluoride content (E3), but significantly longer burning times and times exceeding 1150°C.

[0058] <Example 2> For the low-fluoride composition, a series of test specimens were prepared and evaluated by varying the ratio of atomized aluminum powder to coarse-grained aluminum. The test results are shown in Table 2 below.

[0059] [Table 2]

[0060] The results show how the reaction properties of low-fluoride refractory articles can be adjusted by varying the ratio of fine (highly reactive) aluminum to coarse (lowly reactive) aluminum. Generally, low-fluoride compositions show that a higher proportion of atomized aluminum powder results in shorter ignition times and longer burn times than those with a lower proportion of atomized aluminum powder.

[0061] <Example 3> The riser sleeves (E9, E10, and E11) according to the present invention were compared with a commercially available heat-generating riser sleeve (C1) made using the following composition:

[0062] [Table 3]

[0063] The riser sleeves prepared using compositions E1 to E3 exhibit similar riser performance to the commercially available riser sleeve C1, but with significantly less fluorine-based sensitizer. The inventors further found that the water-insoluble nature of the calcium fluoride used means there are no contamination issues during the regeneration of the mold sand after the metal casting process. By combining this with the use of biodegradable binders such as starch or xanthan gum, the environmental characteristics of the riser sleeves in the examples are greatly improved compared to commercially available riser sleeves.

Claims

1. A composition for producing refractory articles used in riser systems in metal casting, wherein the composition is 40-60% by weight of particulate fire-resistant material, 10-25% by weight of oxidizing metal fuel, 10-30% by weight of oxidizing agent, Sensitizers, and Contains a binder, 0.5–5% by weight of CaSO ４ , and A composition containing 1.5% by weight or less of fluorine.

2. The composition according to claim 1, wherein the composition contains 1.0% by weight or less of fluorine, or does not contain fluorine.

3. The composition according to claim 1, wherein the sensitizer comprises a water-insoluble fluorine compound.

4. The aforementioned fluorine compound is calcium fluoride (CaF ２ The composition according to claim 3, which is the same as the one described in claim 3.

5. The oxidizing agent is iron oxide (Fe ２ O ４ and / or Fe ３ O ４ ), ferrosilite (FeSiO ３ ), potassium nitrate (KNO ３ ), manganese dioxide (MnO ２ ), titanium dioxide (TiO ２ ), and copper oxide (CuO), and the composition according to claim 1, comprising one or more oxidizing agents selected from the group consisting of these substances.

6. The composition according to claim 1, wherein the oxidizing fuel comprises aluminum, and optionally the oxidizing fuel comprises aluminum foil and / or particulate aluminum.

7. The composition according to claim 1, wherein the oxidizing fuel comprises metallic silicon.

8. The composition according to claim 1, wherein the oxidizing fuel comprises atomized powder, and optionally the atomized powder comprises atomized aluminum and / or atomized silicon metal.

9. The composition according to claim 8, wherein the atomized powder comprises at least 60% by weight of atomized aluminum.

10. The composition according to claim 8, wherein the atomized powder contains at least 10% by weight of atomized silicon metal.

11. The composition according to claim 8, wherein the oxidizing fuel comprises at least 30% by weight of atomized powder.

12. The composition according to claim 1, further comprising a carrier fluid, optionally wherein the carrier fluid is water.

13. The composition according to claim 1, wherein the fire-resistant article is a heat-generating fire-resistant article.

14. A refractory article for use in a riser system in metal casting, wherein the refractory article is formed from the composition described in any one of claims 1 to 13.

15. The fire-resistant article according to claim 14, wherein the fire-resistant article is a riser sleeve.

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