DD243921A5 - BIG, PLASTIC, CARBON, FIRE-RESISTANT MASS - Google Patents

Abstract

A granular, plastic, carbon-containing refractory composition keeping workable for at least two months after the date of supply, for the lining of vessels for liquid steel such as casting ladles and transport ladles, by way of ramming, slingering or vibrating, comprises a granulated refractory material such as sintered and/or fused magnesia, spinel, magnesium silicate, zircon, corundum, alumina or andalusite, 1 to 20 percent by weight of a solid carbon carrier in the form of graphite, carbon black, ground coke powder, crushed carbon electrodes or the like or mixtures thereof, and 2 to 7 percent by weight of a stable thermosetting synthetic resin free of hardener, preferably a phenolic resin of the type Novolak or a modified phenolic resin, which is either present in the solid state as a finely ground powder, possibly with 2 to 7 percent by weight of a plasticizer, or dissolved in a non-aqueous solvent. If required, the composition can also contain an antioxidant in the form or 1 to 7 percent by weight of a metal powder and/or finely ground carbide.

Description

Field of application of the invention

The invention relates to a free-flowing, plastic, carbonaceous, refractory mass for lining containers for liquid steel.

Characteristic of the known technical solutions

Recently, the requirements for the refractory lining of steel drip pans and ladles have risen sharply. Due to the often much higher temperatures and longer residence times of the melt as a result of mostly downstream continuous casting, but also by the often laid in these pans metallurgical work, such as desulfurization and dephosphoric, there is very high stress on the lining materials, so that used in the past Delivery materials, such as acid adhesive sands, chamotte, bauxite, can only be used more limited.

At these increased stresses pan linings of magnesia, magnesiachromite and dolomite stones have prevailed. However, the material-specific properties of these basic rocks, such as high dilation, high thermal conductivity and low thermal shock resistance, require a very careful and therefore, due to the time-consuming, expensive laying of these materials. It is therefore desirable to reduce the high time required for the delivery of these containers by the use of basic, fire-resistant building masses.

The state of the art includes ladle delivery devices that are capable of automatically feeding and also compacting the delivery masses. These include the so-called Slingeranlagen and the automatic Pfannenstampfanlagen.

When Slingern the plastic mass undergoes a large acceleration at the end of a conveyor belt and is thus crown of the pans, d. H. the top pan edge, introduced down between a template and the most existing duration or insulating the pan.

This results in a short delivery time due to the large mass throughput. However, there is no uniform compression, as it comes to grain rebound and Kornentmischungen and thereby the formation of coarse grain nests. There is thus an inconsistent mass structure.

Automatic stirrer systems automate the otherwise manual ramming process. The material arrives in a stampable consistency directly in front of the overhung compressed air rammers and is then continuously compressed. This results in a controlled, automated compaction, a short delivery time, which is only about 10 to 20% of the time required for manual pounding. In contrast to the sprouted pans occur here no Kornentmischungen.

The ramming masses of basic basic materials with conventional inorganic bonding, such as silicate, sulfate, phosphate, chromate, which had previously been tested in this stamping process, did not give satisfactory results. Due to the present in these types of mass, mostly pronounced binding gaps in the course of heating by weakening of the chemical bond with not yet performed ceramification, it comes as a result of the high dilation of these basic materials to a layered flaking of the mass during operation. Also, the infiltration of slag and steel in the top mass layers have a very adverse effect and promote the tendency to flaking. In addition, when using such ramming masses a very high amount of time and energy required to achieve the setting required. Until removal of the template, the mass must be at least partially chemically solidified. The subsequent, about one to two days drying by means of gas burner or the like is extremely energy consuming while maintaining at least one temperature plateau until reaching the final strength.

Refractory ramming masses, which are provided with a Dünereser- or Pechzusatz to achieve the required plasticity, also prove to be unsuitable, because the occurring during drying Verqualmung this plasticizing additives prevents the use of tar and pitch for environmental reasons.

According to DE-OS 2806506 magnesia carbon stones are produced by sintering magnesia containing more than 90% by weight of MgO with carbon, e.g. Graphite, mixed in a ratio of 70 to 95 to 5 to 30, 2 to 6% by weight of novolak-phenolic resin solution, based on the weight of the magnesia-carbon mixture, and 8 to 20% by weight of a curing agent, based on the weight of the novolak-phenolic resin, adding the mixture to stones and drying them. Such, intended only for stone mixture is not suitable as ramming mass, because it is not storage stable in the unformed state. ,

According to the US-PS 4102694 is a mass of 100 parts by weight of powdered refractory material, 4 to 40 parts by weight of solid or liquid coal tar pitch or petroleum pitch, optionally with a proportion of tar or asphalt, and optionally 0.5 to 5 parts by weight of mineral powder, such as coke, or fiber material and optionally 0.1 to 10 parts by weight of thermosetting resin by a proportion of 10 to 35 parts by weight of liquid oil, such as mineral oil, in the form of a pumpable slurry used to repair furnace linings. This mass possessed of a mushy consistency is not suitable for compaction by means of pounding or the like, because it is not self-supporting and can not be switched off.

Object of the invention

With the invention, a mass is provided which is free-flowing, carbon-containing and refractory and which remains storable and processible for a long time. , -

Explanation of the essence of the invention

The object of the invention is the development of a free-flowing, carbon-containing, refractory mass, over a long time, for. B.

over two months or more, storable and processable in pans or the like. Liquid steel container ·

introduced and can be compacted by manual or automated pounding, by slinging or by shaking or vibrating and in the heating of which smoke is largely avoided.

This object is achieved according to the invention with a mass, the granular refractory material, 1 to 20 wt .-%, preferably 4 to 10 wt .-% of a solid carbon support in the form of graphite, carbon black, ground coke, electrode break or the like.

or mixtures thereof and from 2 to 7% by weight of a storage-stable, thermosetting, hardener-free synthetic resin, preferably a novolak type phenol resin.

According to one embodiment of the invention, the synthetic resin can be in solid, finely ground form, preferably in a grain size of less than 0.2 mm with a content of less than 50% by weight of less than 0.06 mm. In order to put the mass into a plastic state suitable for compaction by pounding, slinging or shaking, the addition of a lubricant and plasticizer is recommended in this case. As such means, in particular, liquid aliphatic hydrocarbon, namely naphthenbasisch ^ oil or paraffinic oil, or silicone oil into consideration. This lubricant can be added to the delivered in a dry, granular state mass prior to introduction into the container to be lined. In order to avoid this manipulation at the workplace, however, it is more favorable to mix the lubricant already in the production of the mass and to deliver the mass in the plastic state, wherein the mass expediently contains 2 to 7 wt .-% of lubricant.

According to a further embodiment of the invention, the synthetic resin may be dissolved in an anhydrous solvent, such as ethylene glycol or polyethylene glycol. In this case, the solvent acts simultaneously as a lubricant and plasticizer.

The composition according to the invention thus has an organic bond which, by using a storage-stable thermoset,

d. H. a thermosetting resin, in particular a phenolic resin and preferably such a novolak type, is achieved, wherein the addition of a curing agent is avoided. The phenolic resin may also be - e.g. with natural resins - be modified. The composition of the invention surprisingly binds in the heat without hardening.

This bond has the advantage that hardly occur during storage of the mass reactions and therefore a shelf life of at least two to three months and is achieved. When using liquid synthetic resins, eg. B. resoles, it may, however, in the storage and curing of the resins in the presence of about from the refractory material, specifically acting catalysts (especially divalent metal ions, such as Mg, Ca, Cd, Mn) come to chelate crosslinking reactions, whereby the shelf life of the mass is no longer given.

By using a synthetic resin of the type of phenolic resins in the composition of the invention, a higher yield of residual carbon is achieved than when using a liquid synthetic resin. This results in the lining produced with the composition of the invention during operation to form a reinforced coking structure, whereby increased strength at operating temperatures can be achieved. When using a synthetic resin of the phenolic resin type, there is also the advantage, compared to a liquid resin, that reduced dehydration occurs upon heating, which is important in non-hydration resistant refractory base material.

As mentioned, the use of a particular oily lubricating and plasticizing agent in an amount of 2 to 7 wt .-%, preferably 3 to 6Gew .-%, or a corresponding amount of anhydrous solvent in the case of the application of a dissolved synthetic resin for the Processing of the mass required plasticity achieved, the mass is free-flowing and has earth-moist consistency. In this case, the proportion of plasticizer in the case of compaction by pounding in the lower region of the above amount is generally selected in the middle region of the same in the case of slinging and in the upper region of this amount in the case of retting or vibrating. It is to be assumed that the composition according to the invention, as a result of the addition of oil or glycol, is less prone to bead mixtures during slaking than the known compositions.

The composition of the invention has a sufficient green strength so that it can be switched off immediately after compression. According to this property, it is also suitable for compression by means of a tamping machine, which is used without built-in template, in which only a mitwanderndes with the tamping, local stencil-like structure, z. B. in the form of a link belt, is provided.

As a refractory base material for the composition of the invention is especially sintered and / or fused magnesia, preferably having a MgO content of over 85Gew .-%. But it can also be used other refractory base materials, which have a sufficiently high erosion resistance to melting. These are, for example, spinel (such as magnesium aluminum spinel), magnesium silicate material (such as forsterite or olivine), zircon (zirconium silicate), corundum, alumina or andalusite. The refractory material is expediently used in a manner known per se in a granulation which ensures a relatively high packing density.

In order to obtain the highest possible content of residual carbon in order to reduce the wetting with the melt, but also with any existing molten slags, the mass has a proportion of a solid carbon support in the form of graphite, carbon black, ground coke / electrode breakage, Kohlegrus or the like. or mixtures thereof. In the case of carbon-bonded masses in the case of the frequently occurring oxidizing atmospheres, as a result of the erosion of the carbon skeleton, the strength values can be reduced, oxidation protection is required in these cases. As such, the mass may include metal powders such as aluminum, silicon, magnesium or alloys, and / or finely ground carbide such as silicon carbide or boron carbide in amounts of from 1 to 7 weight percent. The resulting in the oxidation of these substances metal oxides protect the carbon necessary for maintaining the bond and to protect against melting and slag infiltration from oxidation. Such substances are known as oxidation protection per se. At not exposed to the oxidizing effect installation sites, the oxidation protection can be omitted. The following examples show the composition of some prepared according to the invention · ready to work masses, which have a shelf life of about three months, a very good melt and slag resistance, a low dilatation and a very good thermal shock resistance.

embodiment Example 1:

Sintered magnesia with 97 wt% MgO and 0.2 wt% Fe ₂ O ₃

sintered magnesia 3-5 mm 10 wt .-% Sintermagnesiä 1-3 mm 36% by weight sintered magnesia 0.1-1 mm 15wt .-% sintered magnesia 0-0.1 mm 22% by weight novolak 4% by weight graphite 3% by weight soot 2% by weight magnesium powder 5 wt .-% silicone oil 3 wt .-%

Example 2:

Sintered magnesia with 86 wt% MgO and 3.5 wt% Fe ₂ O ₃

Sintered magnesia 0-3 mm 81% by weight

Novolac 5% by weight

Carbon black 5% by weight

Silicon carbide SiC 5% by weight

Paraffin oil 4% by weight

Example 3:

Zircon ZrSiO ₄ 0-5 mm 84% by weight

Electrode break 0-0.2 mm 8% by weight

Solution consisting of 37.5% by weight of novolak 8% by weight

and 62.5% by weight of ethylene glycol 8% by weight.

Claims (7)

Invention claim: A free-flowing, plastic, carbonaceous, refractory mass for lining liquid steel containers, characterized in that it comprises granular refractory material, 1 to 20% by weight, preferably 4 to 10% by weight, of a solid carbon support in the form of graphite, carbon black , ground coke flour, electrode breakage or the like or mixtures thereof, 2 to 7% by weight of a storage-stable, thermosetting, hardener-free synthetic resin, and a lubricating and plasticizing agent. 2. Composition according to item 1, characterized in that it contains as a synthetic resin, a phenolic resin, preferably of the novolac type, or a modified phenolic resin. 3., composition according to item 2 or 3, characterized in that the synthetic resin is in solid, finely ground form, preferably in a grain size of less than 0.2 mm with a content of less than 50% by weight of less than 0.06 mm. 4. Mass according to item 3, characterized in that it contains 2 to 7 wt .-% lubricant, such as liquid aliphatic hydrocarbon or silicone oil. ' 5. mass according to item 1 or 2, characterized in that the synthetic resin is dissolved in an anhydrous solvent such as a glycol. 6. Composition according to one of the items 1 to 5, characterized in that they sintered as a refractory material and / or. Fused magnesia, preferably with an MgO content of more than 85% by weight, spinel (such as magnesium aluminum spinel), magnesium silicate material (such as forsterite or olivine), zirconium, corundum, alumina or andalusite. 7. A composition according to any one of items 1 to 6, characterized in that it contains 1 to 7 wt .-% metal powder, such as aluminum, silicon, magnesium or alloys, and / or finely ground carbide, such as silicon carbide or boron carbide, as oxidation protection.