EP1222982B1

EP1222982B1 - Lining for ladles, tundishes and similar receptacles used in the iron and steel industry

Info

Publication number: EP1222982B1
Application number: EP02000486A
Authority: EP
Inventors: Luigi Ture
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-01-16
Filing date: 2002-01-08
Publication date: 2005-04-20
Anticipated expiration: 2022-01-08
Also published as: ES2240577T3; EP1222982A2; DE60203744D1; DE60203744T2; ITBA20010004A1; ATE293504T1; EP1222982A3

Abstract

Lining for ladles, tundishes and similar receptacles used in the iron and steel industry, comprising some layers of refractory bricks joined together with alumina- or zircon-based stuccos treated with a carbon additive.

Description

Technical field

The present invention relates to one-piece lining for ladles, tundishes and similar receptacles used in iron and steel industry. It comprises one or more layers of refractory bricks, which are joined together on every contact surfaces with a low-expansion, heat resistant stucco, said stucco being treated with a carbon-based additive as the one described in the European patent No. 0505542.
As known, steel production process comprises several phases: molten metal from the blast furnace is taken to steel meting shop where further reduction of impurities is done in converters. The liquid steel is taken into ladles and afterwards in other containers or tundishes. Ladles are metal receptacles lined with refractory bricks and a refractory wall, which is in contact with the molten metal and must be periodically replaced (rebricking). Tundishes are containers made of steel and lined with some brick layers coated with 3-4 cm, highly refractory materials.
These containers have some drawbacks: steel infiltration into the refractory materials, persistent adhesion of steel to the ladles or buckets inner walls. Experts try to overcome these problems lining the ladles walls with special refractory bricks and binding materials, as described in the French Patent FR2296485. That lining comprises a layer of insulating material applied to the metal shell of the ladle, an intermediate layer of refractory material and a working layer. Moreover, in the Japanese Patent JP 63 119971, a lining for a ladle which comprises a heat insulating layer, two layers of lining brick and a working layer of bricks has been disclosed, but no mention how to build up the lining is available.
Therefore, up to now nobody has effectively solved the problem. Moreover, said receptacles and, in particular, ladles and buckets are subjected to oxidation of the metal sheets with the consequent reduction of the wall thickness; lastly, also the carbon-based bricks subjected to slags attack, are oxidized. With time and at a temperature ranging between 800°C and 1000°C, oxygen decarburises the bricks, lowering their mechanical resistance, and causing wear and carbon release in the produced steel.

Disclosure of the invention

The invention solves the above mentioned problems being characterised as a one-piece lining comprising some layers of refractory bricks joined together with alumina- or zircon-based stuccos. These stuccos, treated with a carbon additive already described and claimed in the European patent No. 0505542, are thermal resistant and have a low coefficient of thermal expansion.
These and other advantages will be pointed out in the detailed description of the invention that will refer to the figures 1 and 2 of the tables 1/1. Both are examplifying and not restrictive.

Way of carrying out the invention

Fig. 1 describes a practical, preferred but not restrictive example, how said coating can be applied to a ladle surface.
The lining consists of a not penetrable wall pattern made of horizontal and vertical joints with suitable binding materials that makes a real barrier to the liquid steel. In figure 1, (1) is the ladle metal shell, on which a first 2-mm layer of protective, binding and insulating stucco (2) is applied. According to a preferred embodiment, this material can be composed of aluminum silicate, sand and ceramic fibers. Afterwards, a first protective layer (3) made of slabs or bricks (flat or with a proper curvature) is laid on said stucco (2) and joined together with the alumina- and/or zirconium-based, low expansion stucco (5). Before the next protective layer is laid, a further layer of the material (5) is applied on the bricks surface. Said stucco layer must be applied gradually, on small portions of the wall (some square meters), to avoid its complete hardening before the bricks are laid down. Then, the bricks (4) are laid down, joined with the same material (5). The most important part of the coating is a layer (6) made of the very same material of the layer (5). Said layer, which acts as a strong barrier to molten steel or cast iron infiltrations, can have a thickness of approximately 2 mm and must be applied on the whole surface; then it must dry completely (about 4-8 hours, according to the external temperature) before laying the final layer of the wall (7).
As already mentioned, said stuccos (5), (6) are additivated with an additive described in the European Patent 0505542. Said additive for bonding agents with insulating, impermeabilizing and antishrink properties, comprising a mixture of carbonates which, expressed as their respective oxides, comprises in weight percentages, 0 to 1% Fe₂O₃, 65 to 80% CaO, 20 to 30% SiO₂, 0 to 2% Al₂O₃ and 0 to 1% MgO.
The additivated stucco (5), (6) will be prepared in liquid form, mixing the components with an appropriate amount of water, so as to obtain a final mix in the form of a mortar; at least one resin selected from epoxy, acrylic, phenolic, polyurethane, or other resins known for uses with bonding agents will be added; then the composition will to be heated.
Summarizing, the advantages of such coating system are: the reduction of infiltrations due to the stucco interlayers that cool down the molten steel which solidifies into thin sheets easily removable; reduction of maintenance time and longer lifetime of the refractory materials; reduction of ladles cracking and leakage; lower temperature of the shell external surface and, consequently, lower steel heat losses. Finally, the use of such insulating and heat resistant coating for such receptacles avoids the oxidation of the sheet metal walls, their thickness reduction and allows a lower carbon release in the produced steel, in particular if carbon bricks are used.

Claims

Process to build up a one-piece lining for ladles, tundishes and similar receptacles used in iron and steel industry, said lining consisting of one or more layers of refractory material, a working lining and several layers of alumina- and/or zirconium-based binding materials (5), (6), the binding material comprising an additive comprising a mixture of carbonates which, expressed as their respective oxides, comprises in weight percentages, 0 to 1% Fe₂O₃, 65 to 80% CaO, 20 to 30% SiO₂, 0 to 2% Al₂O₃ and 0 to 1% MgO, the process comprising following steps:

applying a first layer of protective, binding and

insulating stucco (2), based on ceramic or alumina fibers, on the ladle metal shell (1);

laying a first protective layer (3) made of slabs or bricks, flat or with a proper curvature, joined together with the binding material (5), on said stucco (2);

applying a layer of the binding material (5) on the bricks surface, gradually, on small portions of the wall to avoid its complete hardening before the bricks of the next protective layer are laid down;

laying the bricks of a further protective layer (4), joined with the same binding material (5);

applying a layer (6), made of the very same binding material as the layer (5) on the whole surface;

drying layer (6) completely;

applying the bricks of the final layer of the wall (7).
Lining for ladles, tundishes and similar receptacles used in the iron and steel industry, obtainable by the process according to the claim 1, consisting of:

a first layer of protective and insulating material (2), approximately 2-mm thick, based on ceramic or alumina fibers, applied on the ladles metal sheets (1) as a binding stucco;

a first protective brick layer (3), laid on the said material (2) and joined together by a material (5);

a layer of the same binding material (5), approximately 2-mm thick, applied as a binding stucco on the first layer of bricks;

a further protective brick layer (4), joined with the same binding material (5);

a layer (6) made of the same binding material as the layer (5);

a final working lining (7), wherein the binding material (5), (6) is alumina- and/or zirconium-based binding material comprising comprising an additive comprising a mixture of carbonates which, expressed as their respective oxides, comprises in weight percentages, 0 to 1% Fe₂O₃, 65 to 80% CaO, 20 to 30% SiO₂, 0 to 2% Al₂O₃ and 0 to 1% MgO.
Lining according to the claim 2, characterized by the fact that said materials of layers (5), (6) containing alumina, zirconium silicate and/or other alkaline or acid elements.
Lining according to the claim 2 or 3, characterized by the fact that said materials of layers (5), (6) present heat resistance up to 1700 °C.