SU1704909A1 - Method of treating molten metal stream when filling tundish from ladle - Google Patents

Abstract

The invention relates to metallurgy, specifically to steelmaking, can be used when casting steel from a ladle into a mold or on a casting machine when casting from steel coke into industrial grade and allows improving the quality of the metal by increasing the degree of degassing during the casting process. Processing the molten metal jet during the razling of the ladle into the metal receiver includes the supply of protective gas from the bottom of the ladle around the metal jet in the form of an outer annular divergent jet to the perimeter of the metal receiver and the inner annular converging jet in the zone of metal entering the metal acceptor to its jet and differs from The known method in that the protective gas in the form of an outer annular jet is supplied in the amount of 80-90% of the total gas flow rate at an outflow rate of GO- 80 m / s, and in the form of an internal annular jet is supplied to lichestve ooschego 10-20% of the gas flow rate with the lapse of 7-12 m / s with the magnitude of the total gas flow rate of the metal stream 60-80 m3 / h. 1 dw., 2 tab. /) ftvsrl,

Description

The invention relates to metallurgy. namely, to the production of plastics, and can be used when casting metal, for example, when casting steel from shell into a mold, or on UN PC when casting from coal into a tundish.

A specific feature of the process of casting steel from a ladle into a mold is the additional contact of a metal jet with ambient air, which results in the second oxidation of metal. so to naskchtseni.o his lhpom and hydrogen. Good quality broomstick / ner / np is associated with the output inf inf mvM, which is non-existent and it is especially oxygen-rich, that is. lodorod

Studies have found that the oxygen content in steel during casting increases by an average of 1.5–2 times, while the content of non-metallic inclusions increases, on average, by -10% VP. Oxidation of the metal at resilk. To leads to an increase in the number of surface cracks, corrosion of easily acidic components and, ultimately, to a decisive deterioration in product quality. The simplest affinity of a fusion is the memory of a memellall from a kitten, 1 d of air.

tbrerien way to protect the jet of rlsplaolenchgo Gn.m.zlll. including under--chuin Ch, D

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id -iJ,

CH5

jo

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Vtnogo r from.) Or l; d - ;; .. nr1,: gdzpm ";; mdo a circle of converging jet around a stream of metal, coming in P. CHGGYALLOPROIMN / :.

Such a T (lmcrcrcrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrk). Of the i - rrr. About a tray of ambient air to an act, a different jet of inert gas and taking a modest: - 1 already vog.dulno-imortnogo gas mixture about the pirkostkom glimpiro rotoro. Pr. Gzchom method is almost not as good as the cavity oxidation OHRUZH5KN.: IM AIR,

There is also a known method of protecting a metal jet, inlet / gas by gas inert gas from the bottom of a scoop, in the form of two annular jets, outer and inner air jets, creating roses around the jet of molten metal, while the speed of the inner gas jet in the dvz and the whip of roses exceeds speed of an external gas jet. And although in this solution the internally active gas jet is protected by a more passive outer gas jet, it has a significant disadvantage in that the external ejection jet interacts with the convective flow of ambient air, which leads to mutual transverse penetration and displacement, which leads to a leakage into the active internal jet an inert gas of an air-inert gas mixture, while creating a sufficient degree of oxidation potential of the space surrounding the jet of molten metal.

In connection with this. that a stream of matalpe creates a significant rarefaction around itself in the outflow zone, the external and internal gas streams flowing in parallel are actively sucked into the stream of metal, which leads to it (and gzz modesting with it in both longitudinal and transverse directions, more recently, oxidizing; i components.

We are close to us on our technical essence and the effect achieved, which is similar to our solution, which is / 1 sssssb .Tb and metal jet processing for the p-k ryngke from a ladle in .oonpvif i::; . Protect the shit from Dmi | 1 d oniiin around metal-metal D as n-pulgyng circular flow-through, 2: F; - ::. r,: .l Oh h, th ..- (. follow up structure 1. Co “iacHc ukzlnnomu.) in h; yt: -;; -, tno (0 1L. vii. in the inner pi riHcrocxOASiiv.:nxn (downstream is streamed on

of the metal by way of their escape, and the other part of the gas in the open air flow directs the creation of the outer protective sheath.

This technical solution has the following disadvantages. The external flow of an inert gas at w ICOKOCKOPOCTHOM outflows through a nozzle Lival is largely saturated with oxygen from the surrounding

0 air due to suction in the outflow zone, where the active dilution zone is formed, while reducing the non-oxidizing potential of the containment shell.

Amplification of longitudinal oscillations in a circular annular jet cuts the convective flow of ambient air transversely in direction from penetration into the interjet cavity, but actively involves sucked air in the outflow zone.

The jets are in a longitudinal-oscillatory process, which aggravates the process of mixing inert gas with air in the direction of the jet's motion. 3 additionally reduces the non-oxidizing potential of the protective jet and will expel the degree of air penetration into the melt.

High velocity gas flow requires the use of high energy gas parameters such as pressure and flow rate up to

0 300 m / h, which reduces the cost-effectiveness of processing and safety in the process of both operation and its transportation due to possible leaks in the service area. During the outflow through the nozzle, Laval acquires the mode of critical outflow of the gas jet, which leads to a decrease in its temperature potential and to the possibility of cooling the jet of molten metal, which in turn complicates

0 casting process and reduces the quality of IU. talla.

The implementation of this method requires a structurally complex device, which further reduces the cost-effectiveness of metal processing during the casting process. High-frequency oscillations of an internal converging gas jet result in saturation of the metal jet with oxygen both from the space between the metal jet and the external protective jet, and by activating mass transfer in the specified space and transferring a part of the oxygen sucked into the external jet.

The listed disadvantages are

5 significant as in the chain to preserve a significant degree of oxidation of the space eo. Around the stream of the melted metal, which impairs the KYACHOSTO ingot, n features. Of the mass of steel grades. no, ingots are characterized by a significant defect on the crack, the presence of rather large non-metallic inclusions, a high content of nitrogen and hydrogen.

The aim of the invention is to improve the quality of the metal by increasing the processing efficiency by increasing the degree of degassing during the casting process.

This goal is achieved by that the protective gas in the form of an outer annular jet is supplied in the amount of 80-90% of the total gas flow at an outflow rate of 60-80 m / m, and in the form of an internal annular jet is supplied in the amount of 10-20% of the total gas flow rate with a flow rate of 7–12 m / s with a total gas flow rate of 60–80 m / h for a metal stream.

The drawing shows schematically a casting ladle 1 with an outlet channel 2 through which a stream of molten metal 3 expires, around which an external annular divergent flow of protective gas 4. is directed and directed to the perimeter of the mold 5, and the internal annular convergent protective gas flow b, aimed at the metal stream in the zone of its entry into the mold, the total flow of protective gas per metal stream being 60-80 m3 / h. 80-90% of the total flow rate of the gas entering the device at an outflow rate of 60-80 m / s is fed to the formation of the external jet, and 10-20% of the gas is fed to the formation of the internal jet at a speed of 7-12 m / s. An inert gas, for example, argon, is used as the protective gas.

The formation of an internal gas flow with the specified parameters and directionality results in the presence of an external gas flow with the specified parameters and directionality towards soft and uniform enveloping of the metal jet with sequential introduction of gas into the liquid metal during its casting both through the jet and through the melt mirror in the mold. Such introduction of gas into cast steel contributes to the formation of fine gas bubbles in it, which ensure a sufficiently effective mixing of the metal in the cavity of the mold, contributing to its refinement. Effective metal treatment with an internal gas flow is possible with simultaneous supply of external flow in the direction of the mold perimeter at the indicated jet outflow rates and reduced gas flow rate. In this case, in the space under the external gas stream, a low-dilution area with an optimal gas-dynamic regime is created, where gas bubbles are released from the cast metal mirror in the mold and a pair of its components, resulting in the active and uniform degassing of the liquid steel, which prevents the penetration of ambient air. in this area and contributes to the removal of excess gases emitted by an external jet of inert gas into the outer space.

With the lower Goanich value of the flow of protective gas equal to 60 m3 / h, the scrap reject in the proposed method is reduced by 1.3-1.5 times, and the content of nonmetallic inclusions decreases 1.8-2.0 times on average.

Reducing the total gas flow less than the lower proposed limit leads to a decrease in the flow rates of gas jets, which violates the gas-dynamic mode in the area under the outer annular jet, reduces its continuity and non-oxidative potential, which creates a possibility for local oxygen penetration into the molten metal and reduces its processing efficiency gas.

With the upper limit value of the protective gas flow rate equal to 80 m3 / h, the scrap reject is reduced by 1.5-1.7 times, and non-metallic inclusions are rather small.

Exceeding the total gas flow above the proposed limit leads to an increase in the flow rates of gas jets, which activates the interaction of the internal gas stream with the metal, exceeds the melt gas saturation in the mold, increases the size of gas bubbles and bubbling in general, as well as splashing onto the mold surface, increases air leakage to the outer stream. This enlarges non-metallic inclusions and degrades the surface of the ingot due to the development of cracking.

With the lower boundary value of the outflow velocity of the outer jet equal to 60 m / s, the protective gas almost reaches the horizontal plane of the inlet end of the mold, thus eliminating lateral penetration of ambient air into the mold cavity.

The lowering of the lower limit of the velocity of the outflow of the outer jet leads to its deformation and the possibility of the flow of ambient air into the cavity of the mold.

With the upper boundary value of the speed of the outflow of the outer jet, equal to 80 m / s, air inflow into the zone of the outflow of the jet

insignificant (1-2%) l inertness of the AFP / Tmich protective shell remains.

Exceeding - the speed limit of the outflow of a drug jet stream leads to active choke 1 / spine and n-e-psg -. gas consumption.

At the bottom, the output of the jet is 7 m / s, treated with s-h-x x -teric-h with the absence of pyni i ,, x 1 nl-about-it small non-metallic: s-s C1 ; i. with tem, small inclusions raaog: g: ;;. distributed over the height of the ingot,: then pr, i -.0.411 g to increase the mechanical LNG, -:;. from the rolled section.

Reduction nmhz.zg: -: shred-zlch enu flow rates -hrg: -: L will reduce uniformity. gas jet of metal, creates a local gas-saturated region and a / dko 1 r-v-rr nne.

With the upper boundary-,) value of the internal jet outflow rate of 12 m / s, the metal is poured out with an almost continuous stream, and if the ksosh is properly centered above the mold, the metal spraying on the walls of the mold is insignificant, which leads to the location of the near-surface layer of the ingot and its; As a result of small inclusions and to with n vi x z k iy, the struck surface of captivity

Exceeding the zerhmego limit of the speed of the internal flow of the gun increases the spray spray. metal, reduces the contact of the gas with the metal stream during its expiration, which, in centr, impairs the treatment of the steel with gas.

Processing the metal jet with an internal convergence with an inert gas jet with the proposed parameters with the obligatory presence of an external expanding gas jet significantly enhances the mass transfer from the metal receiver cavity, especially with its developed dimensions, for example, in the cavity of the sheet mold or in the cavity of the shell. This leads to increased mixing of the liquid metal in the volume of the metal receiver, which averages the temperature and composition of the metal, and therefore improves the quality of the ingot due to the uniform distribution of nonmetallic inclusions, including nitrides, as well as the remaining gases in the volume of the ingot .

Thus, a set of distinctive pop-marks significantly increases the processing efficiency due to an increase in the degree of de-sesation — even at relatively low costs. Hr – 5k in the known methods — the flow rate of argon is up to 300 m3 / h, then 5 the proposed solution is only 60-80 m3 / h, with this h metal significantly

not only oxygen is reduced, but also nitrogen and hydrogen.

Example. The method was carried out under the conditions of the open-hearth shop of the Cherepovets Metallurgical Plant.

Initial data:

the object of casting is a ladle with a 300-ton casting capacity;

PID casting - casting is conducted from the top of the ladle into the mold;

the number of molds in the composition of 36 pieces;

outlet diameter 60 mm;

mold characteristics: sheet, with an entrance section of 455x820 mm;

ingot weight 11.30 tons;

Characteristics of cast steel - quiet crack-resistant type marks 15Х-45Х. 18HGT. 47GT;

the distance between the outlet end of the outlet channel and the inlet end of the mold 300 mm;

the characteristic of inert gas is argon with a pressure in the casting zone of 1.5-2.0 these;

total inert gas flow rate per metal stream 60-80 m3 / h;

nozzle characteristic: annular nozzles, smooth, equidirectional;

flow rate of external inert jet 60-80 m / s;

flow rate of the inner inert jet of 7-t2 m / s.

The results of experimental-industrial testing of the proposed method.

In order to compare the results, the casting was carried out with two ladles: in a known manner and proposed. The total number of spilled buckets 50.

The crack rejects by OTK reduced by an average of 1.5 times, which corresponds well with the metallographic analysis data, showing a sharp decrease in the oxide content (1.8-2.2 times) and gas analysis data, indicating a decrease in nitrogen content on ID- 20% and hydrogen content by 20-40% (see Table 1).

When reducing the total gas flow less than the proposed lower limit, for example at 50-59 m / h, the crack reject in both methods is identical in magnitude, and the content of non-metallic inclusions in ingots spilled by the proposed method decreases slightly (by 5-8%) .

With an increase in the total gas consumption over the proposed upper limit, for example, at 81-90 m / h, the reduction of scrap rejects practically does not occur and the size of non-metallic inclusions increases (by 20-30%).

Table 1

When the speed of the outflow of the outer jet is less than the proposed lower limit, for example, at 50–59 m / s, the gas jet does not reach the mold and the amount of sucked air into the internal cavity increases by 8–14%.

With an increase in the speed of the outflow of the outer jet more than the proposed perne-limit, for example, at 81-90 m / s, the amount of sucked air in the zone of the outflow of the jet increases by 10-20% and the inertia of the jet decreases.

When the flow rate of the internal jet is less than the proposed lower limit, for example, 5-6 m / s, focal large non-metallic inclusions are observed in the ingot body.

When increasing the flow rate of the internal jet more than the proposed upper limit, for example at 13-15 m / s. the degree of metal spraying on the walls of the mold and into the outer space of the casting zone increases, which enlarges the near-surface nonmetallic inclusions, complicates the casting process and increases the oxidation of dispersed metal particles.

Argon consumption by a known method 200-300 m / h. on the proposed - 60-80 m3 / h.

Marriage on a crack decreases on average by 1.5 times, the content of oxides - by 1.8-2.2 times, the nitrogen content - by 10-20% and the hydrogen content - by 20-40% (see Table 2).

By reducing the total gas consumption less than the proposed lower limit, for example at 50-59 m3 / h, the crack yield in both methods is identical in magnitude (2.63% is known. 2.59 is proposed), and the content of non-metallic inclusions in ingots spilled by the proposed method, decreases slightly (the area occupied by oxides decreases from 12.8 to 12.0 mm2.

When increasing the total gas flow more than the proposed upper limit, for example at 81-90 m / h. the reduction of marriage at the crack practically does not occur in the increase in the size of non-metallic inclusions

20-30% (from 100-110 to 120-130 microns

By reducing the flow rate of HC

a jet stream less than offered

5 th limit, for example at 50-59 m / s

gas jet does not reach the mold

the amount of air sucked inside

the new cavity increases by 0-14% (from 4.5-4, i

to 5.0-5.2%).

0 When increasing the flow rate at the jet stream over the proposed upper limit, for example, at 81-90 m / s, the amount of sucked air in the jet outflow zone increases by 10-20% (from 4.55 4.6 to 5.1-5 , 3%). and CTpyv inertness is reduced.

With a decrease in the flow rate of the internal jet less than the proposed limiting limit, for example at 5-6 m / s, focal large (up to 150 microns) non-metallic inclusions in the ingot body are observed.

When increasing the flow rate of the internal jet more than the proposed upper limit, for example at 13-15 m / s,

5, the degree of spattering of metal onto the walls of the mold and into the outer space of the casting zone increases, which enlarges the near-surface nonmetallic inclusions (up to 140-150 µm), complicates the process

0 casting and increases the oxidation of dispersed metal particles.

Claims (1)

The invention of the method for treating a jet of molten metal when casting from a ladle into a metal lore receiver, comprising the supply of protective gas from the bottom of the ladle around the jet of metal in the form of an annular divergent and annular inner convergent jets, characterized in 0 that, in order to improve the quality of the metal by increasing the degree of degassing during the casting process, the outer annular jet is supplied to the perimeter of the metallographic receiver with the flow rate of protective gas 60-00 5 m / s and its flow rate 80-90% of the total protective gas flow, and the inner annular jet is fed to the metal jet to the zone of its entry into the metal receiver at a speed of 7-12 m / s and flow rate 10-20% of the total protective gas flow, which is 60-80 m / h. npoflr «i-.ie, P. | table 2 Managment Inert