RU2663447C2 - Method for drying and heating steel casting ladle lining - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy. As a source of thermal energy for drying and heating the lining of the steel casting ladle, a low-temperature plasma generated in a plasma torch using an inert plasma-forming gas is used. Plasmatron is introduced into the ladle through the hole in the lid vertically along the axis of the bucket until the point at the bottom end of the plasmatron is removed from the bottom of the bottom of the ladle by a distance equal to 0.5–0.6 of the average bucket diameter. Heating of the lining is carried out in two stages, the first of which carries out the drying of the lining, and in the second stage the lining is heated to reach a working temperature of 1,600–1,650 °C. Then the power of the plasma torch increases and melts the working surface of the liner, while the plasmatron moves from top to bottom along the vertical axis of the bucket.

EFFECT: increase in the resistance of the lining is provided.

1 cl, 2 ex

Description

The invention relates to metallurgy and can be used for drying and heating the lining of steel pouring ladles.

Currently, the lining of steel pouring ladles at most metallurgical enterprises is heated at the drying and heating stands using gas-air burners. The highest temperature of the working surface of the lining of ladles after such heating is 1200 ° C. For heating, an empty bucket is installed under the lid, with a burner installed in it, while the evacuation of exhaust gases is carried out through the gas duct. (Modern burner devices (designs and specifications): Reference publication. Vintovkin A.A. et al. - M.: Mashinostroenie-1, 2001. - 496 p.

The closest analogue to the claimed invention, adopted as a prototype, is a method of drying and heating a steel pouring ladle (RF patent No. 2119844) using a gas-air burner mounted in a lid. The distance from the lower end of the burner to the inner surface of the lid is from 0.001 to 0.2 m. Heating is carried out in two stages. On the first, the bucket is dried, and on the second, the lining is heated to 800-1200 ° C. The main disadvantage of this method is the low maximum surface temperature of the lining, which does not exceed 1200 ° C. This leads to a decrease in the resistance of the lining due to thermomechanical stresses arising from the contact of the lining with liquid metal having a temperature of 1600-1650 ° C. In addition, the accumulation of heat by an insufficiently heated ladle lining requires overheating of the melting in the steelmaking unit before it is discharged into the ladle. Also, the location of the burner in the upper part of the bucket does not allow uniform heating of the lining along the height of the bucket, which reduces the resistance of the lining and leads to additional heat loss of metal in the bucket. And when using carbon-containing refractories for lining the bucket, the oxidizing atmosphere in the inner space of the bucket leads to carbon burnout from the surface layer of refractories, which reduces their resistance.

The problem to which the claimed invention is directed, is to develop a method of drying and heating the lining of a steel pouring ladle that does not have the above disadvantages.

To solve this problem, a method has been developed for drying and heating the lining of a steel pouring ladle, covered with a lid, including placing a source of thermal energy in the inner space of the steel pouring ladle, and heating the lining, carried out in two stages, in the first of which the lining is dried. According to the invention, a low-temperature plasma is used as a source of thermal energy, generated in a plasmatron using an inert plasma-forming gas, while the plasmatron is introduced vertically along the axis of the bucket into the bucket through the hole in the lid until the lower end of the plasmatron reaches a point remote from the bottom of the bottom of the bucket equal to 0.5-0.6 of the average diameter of the bucket. At the second stage, the lining is heated until a temperature of 1600-1650 ° C is reached on its working surface. After the stage of heating the lining, the plasma torch power is increased to melt the working surface of the lining, while the plasmatron is moved from top to bottom along the vertical axis of the bucket.

The technical result is to increase the durability of the lining and reduce energy costs during the smelting and after-treatment of steel.

An increase in the lining resistance is achieved by heating the lining at the rated power of the plasma torch until the temperature of the working surface of the ladle lining reaches 1600-1650 ° C and the inert gas is used to generate plasma.

After heating, the layer of the working surface of the lining is melted at a plasma torch power increased relative to the power during the heating of the lining to form a protective layer of refractories, while the plasmatron is moved from top to bottom along the vertical axis of the bucket to uniformly melt the surface layer of refractories, which improves their slag resistance and abrasion resistance and increases the durability of the lining of the bucket.

Reducing energy costs in the smelting and out-of-furnace processing of steel occurs due to a decrease in the heat loss of the metal during heat storage by the lining when released into the ladle. To do this, in the second stage, heating is carried out at rated power until the temperature of the working surface of the lining of the bucket is reached up to 1600-1650 ° C. The temperature of the lining is selected so as to reduce the temperature gradient between the lining and the hot metal poured into the ladle having a temperature of 1600-1650 ° C. Thus, the heat loss of the metal is reduced, which leads to lower energy costs during steelmaking and after-furnace treatment of steel.

The method is as follows. The newly lined bucket is fed to the drying stand and closed with a lid, then the plasmatron is lowered vertically along the axis of the bucket through the hole in the lid until the bottom end of the plasmatron reaches a point that is 0.5-0.6 distance from the bottom of the bottom of the bucket from the average diameter of the bucket. The location of the plasma torch is selected so that the plasma jet is at the same distance from the walls and bottom of the bucket. With a different arrangement of the plasma torch (less than 0.5 or more than 0.6 of the average diameter), uneven heating of the lining of the bottom and the wall of the bucket will be observed, which will not allow to achieve a technical result. An electric voltage is supplied to the plasmatron and, using an inert plasma-forming gas, a plasma discharge is generated.

At the first stage of the process, the ladle lining is dried. The temperature regime and the drying time are selected depending on the type and thickness of the refractory lining. At the second stage, heating is carried out at rated power until the temperature of the working surface of the lining of the bucket reaches 1600-1650 ° C. The temperature of the lining is selected so as to reduce the temperature gradient between the lining and the hot metal poured into the ladle having a temperature of 1600-1650 ° C. In addition, at such a temperature in the heating of the lining, the heat loss of the metal is reduced due to the accumulation of heat by the lining when it is discharged into the ladle, which leads to a reduction in energy costs during steelmaking and after-furnace treatment of steel.

One of the options of this drying and heating method is that after heating, the layer of the working surface of the refractory lining is melted at the plasma torch power increased relative to the power during the heating of the lining to form a protective layer of refractories, while the plasmatron is moved from top to bottom along the vertical axis bucket to obtain an equal height bucket melted layer of the lining. Reflowing the surface layer of refractories can increase their slag resistance and abrasion resistance, which will lead to an increase in the durability of the lining of the bucket.

It is known that during drying and heating of carbon-containing linings in an oxidizing atmosphere at a temperature above 500-600 ° C, carbon burns out from the surface layer of refractories, which leads to their loosening and a decrease in resistance. Since an inert gas is used as the plasma-forming gas, a neutral atmosphere is created in the ladle during drying and heating, which prevents the oxidation of carbon and, therefore, increases the durability of the carbon-containing lining.

Example 1

The method was experimentally implemented at OJSC SKB Sibelectroterm. A plasmatron was installed in the lid of a bucket with a capacity of 3 tons with a lining (ShKU-39 brand).

The distance from the cathode nozzle of the plasma torch to the bottom of the bucket was set equal to 0.45 m. Then a plasma discharge was turned on at 0.5 rated power to remove moisture from the lining. After drying the lining for 1 hour, the plasma discharge power was increased to the nominal value and the working layer of the lining was heated to a temperature of 1600 ° C. Further, according to paragraph 2 of the formula of the proposed method, the layer of the working surface of the lining was melted.

To do this, they increased the plasma discharge power to 1.3 nominal and moving the plasmatron along the vertical axis, uniformly melted the walls of the lining of the bucket.

A lining sample was taken for chemical and phase analysis. The surface of the refractory was coated with a glass phase with zero open porosity of 2-4 mm thickness. At a thickness of 5-6 mm from the surface, the phase composition corresponds to unchanged chamotte. Thus, the molten lining acquires increased resistance, without losing its refractory and heat-insulating properties.

Example 2

The lining of a bucket with a capacity of 3 tons with periclase-carbon lining (type MC95 / 10 according to ISO 10081-3) was dried and heated according to paragraph 1. of the formula of the proposed method. Macro and microscopic analysis of a brick sample showed that carbon burnout from the refractory is practically absent, the thickness of the decarburized layer did not exceed 2 mm. At the same time, according to (Matveev M.V. Increasing the durability of periclase-carbon lining of steel casting ladles based on the use of resource-saving heating technologies: abstract of dissertation of the candidate of technical sciences: 05.16.02 / Matveev Maxim Valerievich - Novokuznetsk. 2013. - 22 C.) when drying periclase-carbon lining with a gas burner, the thickness of the decarburized layer reaches 8-10 mm Considering that during the first few heats this layer is usually completely impregnated with metal and slag, and also that the average wear rate of PU linings is 1.5 mm per melt, the use of new drying technology will increase the lining resistance by 6-7 heats or 10-15 %

Claims (2)

1. The method of drying and heating the lining of a steel pouring ladle, covered with a lid, comprising placing a source of thermal energy in the inner space of the steel pouring ladle and heating the lining, carried out in two stages, the first of which carry out the drying of the lining, characterized in that the heat source is used low-temperature plasma generated in a plasmatron using an inert plasma-forming gas, while the plasmatron is introduced into the bucket through a hole in the lid vertically along the axis of the bucket until the lower end of the plasma torch reaches a point remote from the lower point of the bottom of the bucket by a distance equal to 0.5-0.6 from the average diameter of the bucket, and in the second stage, the lining is heated until a temperature of 1600-1650 ° C is reached on its working surface. 2. The method according to p. 1, characterized in that after the stage of heating the lining increase the power of the plasma torch to melt the working surface of the lining, while the plasma torch is moved from top to bottom along the vertical axis of the bucket.