DD223378A1 - DUST ARM, INSULATING DETERGENT FOR METALLURGICAL DAMAGES - Google Patents

Abstract

The invention relates to a low-dust, well-insulating covering for metallurgical Gefaesse such. B. Giesspfannen or Verteilergefaesse. The aim and object of the invention are to meet the demands made of a covering so complex that the effectiveness of the product is much better adapted to the practical requirements and thus the existing requirements for good insulation, low-dust addition, low slag formation, etc. is largely fair , According to the invention, the covering agent in spherical form consists of an intimate mixture of viable but still unexpanded slate or clay and high-melting additives and is coated with pure kaolin or corundum. The proportion of slate or clay is 60-90%, the proportion of high-melting additives at 10-40%. The refractory additives may consist of refractory clay, kaolin or corundum material. The means serves to cover the metal mirror in metallurgical vessels.

Description

Title of the invention

Low-dust, insulating covering agent for metallurgical vessels

Fields of application of the invention

The invention relates to a low-dust, well-insulating covering of natural resources, which is particularly well for covering metallurgical vessels, such. B. Transportbzw. Ladles, distribution vessels in continuous casting or feeder during molding, but also very good for covering the block heads in the rising calmed down casting in large molds (from 6 tons block weight) is suitable.

Characteristic of the known technical solutions

Known is the coverage of the after tapping of furnaces substantially almost slag-free metal levels in metallurgical vessels, such as pans or Verteilerrinnen with pure or mixed bulk materials, which are either independently powdered or in mixtures of powdery and granular materials. One of the exceptions to this is the widespread use of coked rice husks, which are present in the application - despite previous coking - essentially in their shell structure.

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The task of masking powders is that they

- when adding, spread as evenly as possible and evenly cover the metal surface,

- have a good insulating effect and thus minimize the heat emission via the metal mirror,

- tend to have little or no melt flow, since the required heat of fusion is spontaneously removed from the metal,

- do not react with the metal but still absorb enough inclusions,

- do not react with the lining of the vessels,

- at the addition despite the prevailing thermal buoyancy does not give or slightly dust.

Of the known solutions, none of the demands made meet the requirements in every respect. In the application, it is therefore necessary to decide which disadvantage is accepted for an indispensable advantage

 Known is the covering with coked rice husks, which isolate excellent due to the material structure and low bulk density

 As a disadvantage arise

the low flowability, d. H. the bad distribution, which has to be compensated by additional effort,

the risk of carburisation due to the higher G content of the covering agent in low-carbon steel grades,

the reaction of the pure SiC 2 content of the shells with the chamotte or basic food of the vessels,

the dust discharge when added as a result of the low density,

- the silicogenic character of the fine dusts, especially when emptying used containers.

Covers are also known by the release of fly ash and dusts or mixtures thereof with granular, loosening substances. Covers of this type insulate the metal surfaces especially against heat radiation. In. Low moisture content (less than 0.8 %) is usually a good to very good independent distribution. A disadvantage is the one hand, the significant dust discharge in the task of these funds on the vessels. On the other hand, these substances have a melting point lower than the liquid steel temperature, thereby forming a relatively thick layer of slag starting immediately after the task, though slowly progressing over time. The required heat of fusion, however, is removed from the steel immediately below. Measurements have shown that this results in cooling in a range of 15-30 cm from the steel surface of up to 25 ⁰ C. Since there is generally no appreciable temperature-compensating flow in the vessels after capping, this phenomenon at the end of casting may result in undesirable losses from bears, dying blocks or strands. The heat losses of such covers are thus usually much higher than in the case of substances with a melting point above the steel temperature, unless they have a high thermal conductivity.

In DT-OS 2 219 4-92 the cover is described with already expanded expanded clay spheres. By using this granular material, on the one hand, the dust is eliminated during the addition and on the other hand, a good uniform distribution is achieved. Disadvantage of this cover, however, is that expandable clays specified analysis melting points between 1210 and 1400 ° ü have, which are thus well below the liquid steel temperatures. Due to the significant difference in temperature, in spite of the reduced porosity of the sound,

Thermal conductivity was a strong slag layer formation, as already described. Laboratory investigations prove that the consequent spontaneous withdrawal of heat lasts approx. 10-15 min. And only then does the reduced thermal conductivity come into effect through the porous material. A further disadvantage is the fact that above the slag layer a strongly sintered layer is formed, over which only a thin layer (with time constantly decreasing) loosely original material rests with in technologically necessary works, like eg Temperature measurement in the distribution vessel, this layering is often so strong that the measurements are even prevented or even caused thereby holes in the cover do not close by itself.

In DT-OS 2 345 921 the cover is described with granules of different compositions. Once it is granules, which consist of already expanded materials, wherein the mixture is added to substances that volatilize at service temperature and leave for the insulation cavities. On the other hand, these are granules which are produced from the ground up residual material of the spent vessel delivery. Since such materials are significantly reduced by the inevitable in the use of iron or manganese oxide infiltration in the melting point and thus in turn lead to the formation of a slag zone, still a sheathing with carbon is proposed. Since such compact balls derive relatively much heat over the residence times of the steel under such covers, proposals are here to create artificial cavities in the material by the addition of volatilizing at high temperatures substances or glass or plastic balls with these masses envelop. However, the following facts can not be overlooked. Granules of the proposed materials inevitably lead to a stronger slag formation. This also applies to the carbon-coated grana

lien here once the slag formation is delayed in time, since first the carbon is oxidized, on the other hand there is the risk of carburizing the uppermost steel layer in the vessel, so that this material is not applicable to all steel brands. In addition to the heat of fusion, appropriate heat of vaporization is needed here to create the cavities. There is also the danger of strong, even unacceptable, odor nuisance in the case of these volatilizing substances. This occurs in the envelope of plastic balls in the form described, as a result of the non-existing supply of oxygen, the plastic chars with the release of pungent-smelling gases. The coating of glass beads is apart from the effort already therefore not recommended because these glasses melt well below 1000 ⁰ C and act on the refractory material as a superplasticizer. If the coating is not uniform and very thick, the amount of slag that forms is only increased. If the jacket is strong, the cavity effect decreases and does not fundamentally affect.

Object of the invention

The aim of the invention is to largely limit the disadvantages of known covering powder and to meet the demands placed on a covering so complex that the effectiveness of the product is much better adapted to the practical requirements.

Explanation of the essence of the invention

The invention has for its object to provide a covering that meets the existing requirements for good insulation, low-dust addition, the lowest possible formation of slag, low reaction with the jar and good self-sufficient distribution largely.

According to the invention, the low-dust, insulating covering means for metallurgical vessels is a material in spherical form consisting of an intimate mixture of 60 to 90 % expandable but still unblooded slate or clay and 10 to 40% of a high-melting additive. The refractory additive may be made of refractory clay, kaolin, corundum waste or corundum-containing material.

The invention is based on the use of expandable but still unexpanded substances whose flatulence only occurs during use. This is based on the finding that the swelling power of such substances is utilized to a much greater extent when the expansion temperature is reached rapidly, i. H. that the temperature gradient is high. Substances which are suitable according to the inventive solution are e.g. dried expanded clay and swelling schist. Particularly suitable are expanding scrapers, as they do not have to be dried consuming.

The inventive solution is further based on the knowledge gained that the melting temperature by adding suitable over 1600 - 1650 ⁰ G melting substances such. B, highly refractory chamotte or kaolin, which have a comparatively much higher thermal conductivity and therefore 'alone are not suitable as covering agents, can be increased to about 1580 ⁰ C and 1600 ⁰ C, without the swelling ability of the formed into granules mixture noteworthy is reduced. At the same time it has been found that such substances significantly improve the granularity of the material and increase the abrasion resistance. The addition may be 5-4%, preferably 10-25 % , of such substances. The melting point increase thus achieved simultaneously improves the flowability of the material at the high application temperatures.

According to the inventive solution, the mixture 0 to 5% »preferably 0.5 to 3j5 % carbon or carbonaceous substances, for. As coal or Koksabrieb, waste oils or suitable carbonates are admixed, the swelling ability

of the mixture, promote and increase it. If the bulk density of expanded clay or slate produced according to the present technology is 0.7-1.1 g / c.sup.-1, bulk densities of less than 0.5 and 0.4 g / cm.sup.-3 are achieved by taking advantage of the temperature gradient and adding such substances the balls consisting of the mixture with refractory clay powder or kaolin flour or corundum or corundum-containing substances in a thickness of 0.2 to 5 now, preferably 0.4 to 1.5 nra »be sheathed. According to the invention, the mixture may contain one or more organic or inorganic binders, such as phenolic resins, urea resins, carboxymethylcellulose, polyvinyl alcohol, sulfite waste liquor, dextrins, water glass, or even in an amount of 0.2-10%, preferably 0.5-5 % Increasing the compressive strength can be added.

Experiments have shown that in the granules according to the invention, the forming in the first 10 min. Slag layer is less than 10 % of the layer that forms in the cover with already expanded material. Furthermore, measurements have proven that the heat output over a constant area at the same bed height in the mixture according to the inventive solution by 20 - 35% lower. The spherical covering means according to the invention is in a dense sphere packing with a diameter of 0.5 to 15 nm, preferably 1.0 to 9.0 mm.

Experiments with coated granules according to the inventive solution have clearly shown that above the clearly pronounced swelling zone, the granules show no sintering or Yerfrittungserscheinungen. They are loosely and loosely next to each other, which causes places of the cover, which must be pierced by technologically-related work - such as temperature measurements, to cover themselves automatically after such work by Nachrieseln again. Furthermore, coated granules according to the invention can be used on all steel grades without danger of carburization.

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embodiment

The following examples are intended to illustrate the invention, it being understood under the term shale a at temperatures of 1100 to 13OO ⁰ G ⁰ G blähfähiger slate.

Example 1 Covers for metallurgical vessels

refractory clay (melting point greater than 1630 ⁰ G) 20 - 40 % slate unblooded 60 - 80 %

Humidity max. 0.6%

Grain size 1 - 15 mm

preferably 2 - 8 mm

Example 2

Covering means for distribution channels

Slate unblooded 70 - 85 % kaolin 10 - 25%

Carbon 0 - 5 %

Humidity max. 0.5%

Grain size. 1-5

Example 3

Covers for ladles and yards for all steel grades

Granules consist of a core and a coat

Core: slate / expandable clay (dry) 95.5 - 99% carbon / carbonaceous

Substances "4 - 4%

Humidity max. 0.5%

Grain size (core) 1.0 - β mm

Coat: kaolin '100 %

Sheath thickness · Ό, 4 - 1.5 mm

Grain size (total) 1 »8 - 9» 0 mm

Example 4,

Core: slate, swelling clay 75 - 85%

fireproof 'clay '" 14 - 24 %

Binder polyvinyl alcohol 1% moisture max. 0.5%

Grain size (core) 1.0 - 6.5 mm

Coat: corundum flour. 99.25%

Binder (Carboxylmethyl- 0.75%

cellulose)

Sheath thickness 0.25 - 1.0 mm

Grain size (total) 1.5 - 8.5 mm

Claims (4)

invention claim 1. Dust-poor, insulating covering means for metallurgical vessels, characterized in that it consists in spherical form of an intimate mixture of 60 to 90 % expandable, but still unexpanded slate or clay and a high-melting additive in a proportion of 10 to 40 % , that the in spherical form present mixture with pure kaolin, clay, corundum or corundum waste in a thickness of 0.2 to 5 mm, preferably 0.25 to 1.5 nm coated nim and that the mixture is still one or more organic or inorganic binder, such as Contains phenolic or urea resins, carboxymethylcellulose, sulfite liquor, dextrins, water glass and others in an amount of 0.2 to 10%, preferably '0.5 to 5 % . 2. Abdeckmittel according to item 1, characterized in that the refractory additive consists of refractory clay, kaolin, corundum material or corundum waste. 3. covering according to item 1 and 2, characterized in that the mixture up to 5%> preferably added 0.5 to 3> 5 % carbon or carbonaceous substances in the form of coal, briquette, Koksabrieb, waste oils or suitable carbonates are. 4. covering means according to item 1 to 3, characterized in that the Gemis'ch in the diameter of 0.5 to 15 mm, preferably from 1.0 to 9> 0 mm is present in dense sphere packing.