SU787484A1 - Method of producing carbon killer - Google Patents

Description

The invention relates to metallurgy and can be used in the preparation of carbonaceous deoxidizing agents for the refining treatment of liquid metals. A known method for producing graphitized and carbon materials used for refining liquid metals. After heat treatment, crushing, dosing, solid carbonaceous materials are mixed with coal-tar pitch in mixing machines. After pressing, the billet is cast in a gas furnace to a temperature of 1250-1350 ° C. The duration of firing varies from 100 hours for small products to 360 hours and more for large products. The purpose of such slow roasting is to obtain a high density and mechanical strength of the products, for which, in the range of temperatures at which the most intense gassing occurs, the heating rate is minimal and amounts to 3-150 s / h. Burnt billets after machining are carbon electrodes. In the production of graphite electrodes, baked blanks are further subjected to graphitization at 2600-280000 for several days. In the process of graphitization, the electrical resistivity sharply decreases and the thermal conductivity rises 12-15 times. The lack of use of graphitized and carbon electrodes for refining over-oxidized steel is associated with freezing the slag-metal crust on the surface of the block at the moment it is introduced into the metal. This is due to the high thermal conductivity of the materials used, due to the high density. In addition, relatively small porosity reduces the reactivity of these deoxidizers. Therefore, the onset of the reaction is delayed by 2-4 minutes. The cost of graphite and carbon electrodes is quite high (360-400 p / t and 200-230 p / t, respectively). The aim of the invention is to increase the porosity and reactivity of the deoxidizing agent, reducing its thermal conductivity. The goal is achieved by the fact that the burning of the deoxidizing agent is carried out by heating to a temperature of 320-450 0 at a speed of 130-200 0/4, then heated to 630,700 0 at a speed of 30-OO s / h and kept at this temperature for 1-2.5 hours The rate of temperature rise of 130200 C / h when heating blanks to 320 is due to the high porosity of the deoxidizer. At a temperature of .32COc, an intensive release of volatile substances begins during the coking of the binder, the coal tar pitch. At a temperature of HIGH, the intensity of the gas stream is noticeably reduced. At the same time, the rate of formation of volatile substances exceeds the rate of their filtration through the material, gases develop high pressures and form pores in deoxidation. Fluctuations in the heating rate values are due to the geometric dimensions of the blanks: lower heating rates correspond to a smaller diameter of the product. At a heating rate of more than 200 s, large pores and even discontinuities are observed in the product, which drastically reduces the mechanical strength of the products. With

g

Fricky,

Components

-20 + 10

Thermoanthracite -10 + 4

Thermoa; ntratsit (grinding) Coke (grinding) Coal tar

Table

; i

Hitch

Component content,%

kg mm

20024 i 4

16020 + 4

110 16 jf 4 290 40 + 4

24 + 4

240 speeds less than 1300s / h. Porosity is not developed in the amount of deoxidizer -. In the temperature range 450-700 0, the heating rate should be 50-100 ° C / h. When the heating rate is less than 50 ° C / h, the firing process is unnecessarily delayed, and the gas consumption increases. When firing in the second period with a heating rate greater than. necessary physical and mechanical properties of deoxidizing units will not be provided. When reaching 700 ° C, the isothermal aging should be 1-2.5 hours. This operation is final and is necessary to complete all processes of thermal decomposition of the charge. If the exposure time is less than 1 hour, incomplete removal of gases and volatile substances is possible in the inner layers of the block. The retention of the deoxidizing units for more than 2.5 hours, as well as the rise in temperature above, is impractical, since the properties of the deoxidizing agent do not change appreciably. Example. The deoxidizing units are made from the carbonaceous mass of the composition shown in Table 2. one.

The crushed coke and thermoanthracite are mixed with coal tar pitch (softening point b5-70 C) in mixers at 140-150 ° C for 15-20 minutes.

From the resulting mass, hollow blocks are made with an external internal 300 meter — 60 mm and a length of 500 mm. The blocks are prepared in detachable forms and fired in a gas furnace in carbon bed. The heating rate is adjusted by changing the supply of natural gas through the upper and lower burners. The heating temperature is controlled using thermocouples immersed in carbonaceous bed at a distance of 100,150 mm from the surface of the blocks.

The speed of the rise of the temperature of the blocks is reduced to 4500s; I support vl30-200C / 4. When the specified temperature is reached, the feed rate of natural gas is reduced and firing is carried out at a heating rate of 55-100 ° C / h. After 3 hours and 10 minutes, when the temperature of the blocks is reached, isothermal aging is carried out for 1 hour and 20 minutes and then the gas is turned off.

The firing mode and the results of testing carbonaceous scavengers are presented in Table. 2

table 2

Claims (1)

Claim A method of producing a carbon deoxidizer, including crushing, mixing, firing the components of the mixture, is characterized in that, in order to increase porosity and reactivity, reduce thermal conductivity, the firing of the deoxidizer is carried out by heating to a temperature of 320-450 ° C at a speed of 130-200 ° C / h, then heated to 630700 ° C at a speed of 50-100 ° C / h and kept at this temperature for 1.0-2.5 hours