RU50893U1 - THERMOSTAT - STEEL FILLING BUCKET - Google Patents

Abstract

The utility model relates to metallurgy, and in particular to the design of steel casting ladles used in the casting of metal into molds. The technical result of the claimed utility model is to reduce the heat loss of the metal during its soaking in the ladle, eliminating the formation of “cold metal” at the bottom of the steel ladle and in the steel teeming cup, improving the surface quality of the ingot obtained when casting metal into the molds, by maintaining the required range metal temperature. Thermostat - a steel pouring ladle contains a container with liquid metal, on the surface of which a heat-insulating mixture is placed, the tank is equipped with a heat-insulating lid. Between the lid, which does not touch the mixture, there is a protective atmosphere in the form of an oxygen-deficient atmosphere, the mixture contains a heat-insulating powder, the grains of which consist of expanded vermiculite or expanded perlite nuclei coated with soot carbon shells, and the powder layer height is:

h = (0,040-0,045) N, where:

h is the height of the powder layer;

H is the height of the molten metal in the tank.

Description

The utility model relates to metallurgy, and in particular to the design of steel casting ladles used in the casting of metal into molds.

Closest to the proposed thermostat - a steel pouring ladle designed for crushing metal into molds, is a device for warming the upper part of a steel ingot containing a container with liquid metal, for example, a mold, and a heat-insulating lid (see patent RU 2027539, MKI B 22 D 7 / 00, published on January 27, 1995, "Method for Insulating the Top of a Steel Ingot"), selected by the applicant as a prototype of the device.

In a known device for warming the upper part of a steel ingot, the heat-insulating cover is made, for example, of kaolin with a thin metal shell. The mold is equipped with a profitable extension or insulating liners. After filling the device with metal, it is closed with a lid until the ingot solidifies. After 1 / 3-2 / 3 of the total solidification time of the ingot, the lid is opened for a short time and the components of the exothermic mixture are poured into the mold. First, the component layer, which decomposes when heated with oxygen evolution, is filled up, then the component layer, during the interaction of which with the heat, is released. Immediately after this, the mold is again covered with a lid and held until the ingot solidifies.

The disadvantage of a device for warming the upper part of a steel ingot is the complexity of the design and the complexity

insulation of the upper part of the steel ingot. The complexity of the design lies in the fact that the heat-insulating liner inserted into the mold is made of soft heat-insulating material that does not allow providing an even end surface during the manufacture of the liner. The heat-insulating lid is also made of heat-insulating material, as a result of which it is difficult to ensure an even plane of contact between the closed lid and the heat-insulating liner and the edges of the device’s tank. From the above it follows that when the cover is installed on the heat-insulating liner there will be large gaps through which heat from the metal will be radiated. Therefore, the cover will not provide the necessary thermal insulation of the metal.

Another disadvantage is the increased complexity and requirements for ensuring safety when installing the lid, since at high metal temperature in the mold it is necessary to close and open it three to three times at a distance of 2-3 meters. Therefore, special manipulators are required, including special bunkers for filling the components of the exothermic mixture.

The disadvantage is the increase in heat loss of the metal due to the fact that the cover is made of kaolin, i.e. clay, which has greater thermal conductivity compared to the proposed heat-insulating mixture, and, as a consequence, the possibility of formation of defects on the surface of the ingots.

The technical result of the claimed solution is to eliminate these disadvantages of the prototype, namely: reducing heat loss of the metal when it is held in the ladle, eliminating the formation of "cold metal" at the bottom of the steel pouring ladle and

in a steel pouring can, improving the quality of the surface of the ingot obtained by casting metal into molds, by maintaining the set temperature of the metal within the required limits, simplifying the design.

The technical result of the utility model is aimed at eliminating these disadvantages of the prototype and is achieved by the following solution.

In a thermostat - a steel-pouring ladle containing a container with liquid metal, on the surface of which a heat-insulating mixture is placed, the tank is equipped with a heat-insulating lid, according to a utility model, a protective atmosphere in the form of an atmosphere with oxygen deficiency is contained between the lid that does not touch the mixture, the mixture contains heat-insulating powder, grains of which consist of expanded vermiculite or expanded perlite nuclei coated with soot carbon shells, and the height of the powder layer is:

h = (0,040-0,045) N, where:

h is the height of the powder layer;

H is the height of the molten metal in the tank.

The heat insulating mixture can be placed on the surface of the molten metal in a polypropylene container.

The height of the molten metal in the tank may be equal to the diameter of the steel pouring ladle.

The presence of a protective atmosphere in the form of an atmosphere with a lack of oxygen between the lid and the mixture prevents the access of oxygen to the upper part of the bucket between the metal mirror and the lid and creates the conditions for the process of converting the mixture on the metal surface to

heat-insulating powder in the form of grains with cores of molten vermiculite coated with soot carbon shells.

A protective environment is an atmosphere with a lack of oxygen between the lid that does not touch the mixture and the mixture prevents the interaction of oxygen with the mixture, which results in the formation of grains of heat-insulating powder with molten vermiculite cores coated with soot-carbon shells having low thermal conductivity of 0.16 W / m. hail. and bulk density of 160 kg / cubic meter.

The granulometric composition of the initial heat-insulating mixture placed on the surface of a liquid metal in a steel pouring ladle is as follows:

- fraction greater than 0.6 mm, i.e. 0.6-2.5 mm, 90% of the volume of expanded vermiculite or expanded perlite, a fraction of less than 0.6 mm and 2.5 to 5 mm is 10% of the volume of expanded vermiculite or expanded perlite, taken within 60- 70% of the total volume of the mixture;

- the fraction of 0.5-5.0 mm is 100% by weight of sawdust, taken within 30-40% of the total mass of the mixture.

The initial heat-insulating mixture on the surface of a liquid metal at elevated temperatures up to 1550-1600 ° C, with a tightly closed container lid, a protective environment - an atmosphere with a lack of oxygen between the metal mirror and the lid, is converted into a heat-insulating powder.

The conversion of the initial mixture into powder consists in the thermal decomposition of wood sawdust into carbon black at a temperature of 1550-1600 ° C with a lack of oxygen.

Sooty carbon envelops particles of expanded vermiculite / perlite, forming a powder whose grains contain

expanded vermiculite / perlite cores coated with soot carbon shells.

The heat-insulating powder reduces the bulk density of the mixture to 160 kg / cubic meter, increases the melting temperature to 1700 ° C, and reduces thermal conductivity at 1000 degrees. C to 0.16 W / m

For the optimal formation of kernels of grains of expanded vermiculite / perlite and soot carbon shells, it is necessary that the fractions of expanded vermiculite / perlite and fractions of wood sawdust have the following parameters:

- expanded vermiculite / perlite should have a fraction of 0.6-2.5 mm to ensure a minimum thermal conductivity of 0.045 W / m deg;

- wood sawdust should have fractions of 0.5-5 mm to ensure sufficient complete enveloping of expanded vermiculite / perlite and the formation of heat-insulating powder.

When the content of wood sawdust in the initial mixture is from 30% to 40% of its total volume, optimal enveloping of expanded vermiculite / perlite nuclei and optimal shell thickness around expanded vermiculite nuclei occurs, which increases the melting point and reduces the thermal conductivity of the mixture.

The height of the layer of heat-insulating powder of the mixture on the surface of the liquid metal in the range: h = (0,045-0,050) N, where:

h is the height of the powder layer;

N - the height of the liquid metal in the tank,

selected from the conditions of the minimum metal cooling rate in

bucket equal to 0, 20-0.22 degrees. C / min

The heat-insulating powder of the mixture protects the metal from cooling until the end of the casting of the metal into the molds,

preventing the formation of "cold metal" - scrap at the bottom of the bucket.

The placement of a heat-insulating mixture in a polypropylene container allows to simplify the technology of loading the mixture.

The table shows the characteristics obtained by testing the proposed device and device prototype.

Table Characteristics of the insulating mixture According to the proposed device According to the prototype Thermal conductivity at 1000 degrees. C, W / m, city 0.16 0.25 The cooling rate of the metal in the bucket, deg. C / min 0.2 0.31 Bulk density, kg / cubic meter, m 160 280

The essence of the proposed technical solution is illustrated by drawings.

Figure 1 shows a longitudinal section of a thermostat - steel pouring ladle.

Figure 2 shows a structural model of a heat-insulating powder, the grains of which contain kernels of expanded vermiculite / perlite, coated with shells of carbon black.

The claimed technical solution is as follows.

Thermostat - steel pouring ladle 1 contains a container with liquid metal 2 and a heat-insulating lid 5. On the surface of the metal 2 is placed a heat-insulating mixture 3.

The device operates as follows.

For thermal insulation of liquid metal, a heat-insulating mixture 3 containing 60-70% by volume of expanded vermiculite / perlite and 30-40% by volume of wood sawdust is fed into the tank of a thermostat - a steel-pouring ladle 1 with liquid metal 2. Create a protective atmosphere in the upper part of the bucket 1 in the form of an atmosphere 4 with a lack of oxygen. A mixture of 3, consisting of fractions of 0.6-2.5 mm of expanded vermiculite or perlite and fractions of 0.5-5.0 mm of wood sawdust, is placed on the surface of metal 2 at a temperature of 1550-1600 ° C.

The upper part of the tank is closed with a lid 5, which is not in contact with the mixture 3 and create a protective environment, maintaining in the upper part of the thermostat 1 an atmosphere with a lack of oxygen. A heat-insulating mixture packed in a polypropylene container (not shown in the drawing) is placed on the metal surface. On the surface of the metal 2, an insulating powder 6 is formed, the grains of which contain cores 7 of expanded vermiculite / perlite, coated with shells 8 of carbon black. The height of the layer of insulating powder is calculated from the condition: h = (0.040-0.045) N, where: h is the height of the powder layer;

H is the height of the liquid metal 2 in the tank, which is equal to the diameter of the thermostat 1. The resulting heat-insulating powder is kept on the surface of the metal until it is cast into the molds.

An example of a specific implementation.

An insulating mixture 3 containing 65% by volume of expanded vermiculite according to GOST 12865-67 and 35% by volume of wood sawdust was placed in the capacity of a thermostat - a steel-pouring ladle 1 with liquid metal 2. The heat-insulating mixture 3 was placed on the metal surface using a polypropylene container, after melting of which the mixture was poured onto the metal surface with a layer whose height was equal to 135-150 mm. The temperature on the metal surface was 1560 ° C. The height of the layer of heat-insulating powder was equal to 121-140 mm, it was calculated from the condition of equality of the height of the liquid metal to the diameter of the thermostat 1.

The upper part of the container was closed with a lid 5, not in contact with the mixture 3, a protective environment was created in the form of an atmosphere with a lack of oxygen. Sooty carbon, enveloping particles of expanded vermiculite, increased the melting temperature of the mixture to 1700 ° C. As a result, the grains of the heat-insulating powder consisted of cores 7 of expanded vermiculite, coated with cladding 8 of carbon black.

In the mixture, the fraction of expanded vermiculite 1.0 mm was 90%, the fraction 0.2 mm was 10% by weight of vermiculite. Wood sawdust fractions of 0.5-5.0 mm amounted to 100% by weight of wood sawdust.

Claims (3)

1. Thermostat - a steel pouring ladle containing a container with liquid metal, on the surface of which a heat-insulating mixture is placed, the tank is equipped with a heat-insulating cover, characterized in that a protective atmosphere in the form of an atmosphere with oxygen deficiency is contained between the cover not touching the mixture, the mixture contains heat-insulating powder , the grains of which consist of expanded vermiculite or expanded perlite nuclei coated with soot carbon shells, and the height of the powder layer is: h = (0,040-0,045) N, where h is the height of the powder layer; H is the height of the molten metal in the tank. 2. Thermostat - steel pouring ladle according to claim 1, characterized in that the mixture is placed on the surface of a liquid metal in a polypropylene container. 3. Thermostat - steel pouring ladle according to claim 1, characterized in that the height of the molten metal in the tank is equal to the diameter of the steel pouring ladle.