CS238719B1 - Refractory material for linings, especially monolithic linings of metallurgical equipment - Google Patents

Abstract

Refractory material intended for working masonry linings of metallurgical equipment, possibly for refractory monolithic linings, cast, steamed, or cast, which consists of 70 to 92% of aggregate and 8 to 30% of cement-based binder. The essence of the solution lies in the fact that the binder contains 0.01 to 4.5% by weight of a water-soluble lignin derivative, e.g. alkali metal or alkaline earth metal lignin sulfonate and 0.005 to 2.25% by weight of a water-soluble alkali metal silicate or alkali metal or alkaline earth metal carbonate or hydrogen carbonate, the remainder being cement clinker free of gypsum, with a specific surface area of 220 to 1,000 m2/kg.

Description

(54) Refractory for linings, in particular monolithic linings of metallurgical installations

Refractory material intended for working masonry linings of metallurgical equipment, eventually for refractory monolithic linings, cast, stewed, event. methane, which consists of 70 to 92% grit and 8 to 30% cement-based binder. The principle of the solution consists in that the binder contains 0.01 to 4.5% by weight. % of a water-soluble lignin derivative, e.g. an alkali metal or alkaline earth metal linginsulfonate, and 0.005 to 2.25 wt. water-soluble alkali metal silicate or alkali metal or alkaline earth metal carbonate or acid carbonate, the rest of the gypsum-free cement clinker, with a specific surface area of 220 to 1 000 m ² / kg.

The invention relates to refractory materials intended for working masonry linings of metallurgical installations, eventually for refractory monolithic linings, cast, stewed or cast iron. metané.

Refractory compositions based on hydraulic binder systems are known, such as Portland cement, high-speed Portland cement, slag-portland cement, aluminous cement, barium cement, or chemical binder systems such as phosphate or the like.

The Portland cement refractory compound has been widely used in the construction of heat or hot-air aggregates. The main components of this mass are ground mineral additives and fillers, which are characterized by sufficient heat resistance. However, the use of this refractory composition with Portland cement is limited to a temperature limit of 1200 ° C and is not used for linings, refractory minerals or erasure of metallurgical vessels that come into contact with liquid metal, especially steel. A considerable disadvantage of all refractory materials with a hydraulic binder system is the relatively high amount of water or other solutions supplied during the refractory composition itself, which adversely affects the stability of the properties of these refractory materials immediately after their manufacture. However, the instability of crystalline hydrates, especially portlandites at high temperatures, is more severe. Refractory concrete with Portland cement and inert additives can withstand temperatures of 1,200 to 1,300 ° C, and under a heat load of 0.2 MPa / cm 2, 1,100 to 1,200 ° C, depending on the type of filler used. Refractory materials with aluminous cements are characterized by the fact that their hydration does not give rise to free calcium oxide hydrate, which is unstable at temperatures above 500 ° C and therefore aluminous cement-based refractory materials can be used in conditions where the temperature reaches 1,400 ° C . However, the applicability at higher temperatures is paid for by the higher raw material price and the increased requirements for the drying regime. Finally, refractory materials ηε based on high-alumina cements with high refractory fillers can withstand temperatures up to 1700 ° C and can come into contact with liquid metal, including steel. However, their price is disproportionately high.

The above-mentioned disadvantages do not have a refractory mass containing cement-based binder in an amount of 8 to 30% by weight of the mixture and an abrasive in an amount of 70 to 92% by weight of the mixture, such as zirconium, corundum, fireclay or dolomite, magnesite, magnesite, chromium, chromite, individually or in combination. According to the invention, the binder contains 0.01 to 4.5 wt. % of a water-soluble lignin derivative, e.g., an alkali metal or alkaline earth metal lignin sulfonate, and 0.005 to 2.25 wt. water-soluble alkali metal silicate or alkali metal or alkaline earth metal carbonate or acid carbonate, the rest of the gypsum-free cement clinker, with a specific surface area of 220 to 1000 m / kg. Preferably, the water-soluble sulfonated condensation product of mono- or polyhydric phenols with formaldehyde in an amount of 0.005 to 2.25% by weight is used to increase the pot life of the refractory. cement clinker.

An advantage of the inventive refractory composition is the ease of availability of the raw materials used. When using a gypsum-free ground clinker in the refractory composition of the invention, the amount of water required to prepare the mixture is at least 1/3 lower than in the treatment of Portland or aluminate cements hitherto used, which guarantees improved stability of the refractory composition during gradual heating to working temperatures. The microstructure of the refractory composition according to the invention is of a monolithic nature, unlike the microstructure of a Portland cement composition. Massive portlandite crystals are missing in the microstructure of the mass according to the invention. The Portlandite in the refractory composition of the present invention is substantially less than in the microstructure of the Portland cement composition. The Portlandite is finely dispersed. The properties of the inventive refractory composition with Portland-free, cementless clinker are obviously affected by the absence of gypsum sulphate. Indeed, sulphate anions reduce the viscosity and surface tension of silicate melts. Thus, in the absence of gypsum, a higher viscosity melt is formed in the composition according to the invention, which contributes to increasing the mechanical properties of the composition at high temperatures, as illustrated by the following examples of use.

EXAMPLE 1 A refractory composition was prepared, the sanding of which consisted of 35% by weight. % magnesitchrom and 52 wt. magnesite and 13 wt. binders. The binder consisted of a finely ground gypsum-free cement clinker having a specific surface area of 700 m. kg called Portland clinker,

1.5 wt. % potassium carbonate and 0.5 wt. sodium lignisulfonate. In order to extend the pot life, sulfonated phenol formaldehyde condensate was also added in an amount of 0.1% by weight of Portland clinker. The mass was mixed to contain 5.5 wt. humidity. The refractory was used in a 20 t steel ladle. A layer of refractory material with a thickness of 200 mm was crushed onto the working brick lining. After eighteen hours of free curing in air, the mass strength reached a pressure above 4.5 MPa. cm ^-2 . Further, the mass was dried at a temperature of up to 200 ° C for twelve hours and heated at about 900 ° C for eight hours before the first melting. After casting the first melting from the ladle, the surface of basic refractory cast was well sintered. Thirty steel melts with a temperature of about 1,640 ° C were monitored in a ladle. The refractory compound has proven its suitability for both carbon and alloy steel and fully complies with the requirements of off-furnace steel refining in a ladle.

Example 2

The refractory mass was prepared by mixing 85 wt. magnesitchrom and 15% by weight binders. The binder consisted of finely ground gypsum-free cement clinker with a specific surface area of 900 m. kg ^- 0.5 wt. potassium bicarbonate and 1% sodium lignin sulfonate. To influence the solidification rate, sulfonated phenol-formaldehyde condensate was added in an amount of 0.3% by weight of said Portland clinker. The casting was made of two-ton steel ladles. The ladle was operationally used to cast steel at a temperature of 1,640 ° C and withstood 35 melts without damage.

Example 3

In practice, the use of the refractory composition with the grit of Examples 1 and 22 bonded with 21% by weight has also been verified. finely ground Portland clinker without gypsum with a specific surface of 800 m. kg ^- ', with an addition of 2% by weight. % sodium bicarbonate and 1.5 wt. sodium lignin sulphonate by weight of Portland clinker and with the addition of 0.5% sulphonated phenol-formaldehyde condensate to retard solidification. The mass was used as a protective tundish layer cast and tamped in a continuous steel casting machine, the layer thickness applied to the masonry fireclay layer of the tundish lining was 10-30 mm.

Example 4

The refractory compound is also suitable for compacted and cast linings of chill heads for casting of steel ingots at a casting temperature of approx. 1,600 ° C. For this use, a refractory composition of 80% by weight was tested. of fireclay and 20 wt. binders. Binder

-1 consisted of finely ground Portland clinker without gypsum, with a specific surface of 300 m. kg, 0.75 wt. % of sulfonated phenol-formaldehyde condensate and 2.75 wt. potassium carbonate. The lining lasted without damage 28 casting.

Example 5 A refractory composition of 90% by weight was prepared. Corundum slag and 10% by weight binders. The binder consisted of fine ground gypsum-free clinker with a specific surface area of 500 m ² . kg ^- 0.5 wt. % potassium carbonate, 1.0 wt. sodium ligninsulfonate.

To influence the solidification rate, a 0.4% by weight finely ground clinker sulfonated phenol-formaldehyde condensate was added to the pi'idene water mixture. The mixing mass contained 7% moisture when mixed. The use of a shotcreting material to repair an oven operating at temperatures of 900 to 1100 ° C increased the oven life by 20 ° C.

2387t9

The refractory mass is suitable both for linings of metallurgical vessels coming into contact with liquid metal, as well as in the construction of heat or hot-air aggregates operating in the temperature range of 600 to 1,400 ° C or during their repair performed by gunning or the like.

Claims (2)

SUBJECT OF THE INVENTION Refractory mass for linings, in particular monolithic linings of metallurgical vessels, consisting of an agglomerate based on, for example, magnesite-chromium in an amount of 70 to 92% by weight and from 8 to 30% cement-based binder, characterized in that the binder contains 0.01 to 4.5 wt. % of a water-soluble lignin derivative, e.g., an alkali metal or alkaline earth metal lignin sulfonate, and 0.005 to 2.25 wt. water-soluble alkali metal silicate or alkali metal or alkaline earth metal carbonate or acid carbonate, the remainder of the gypsum-free cement clinker having a specific surface area of 220 to 1000 m / kg. 2. A refractory composition as claimed in claim 1 comprising a water-soluble sulfonated condensation product of phenols with formaldehyde in an amount of 0.005 to 2.25% by weight. cement clinker.