CN114317873A

CN114317873A - Steelmaking slagging process

Info

Publication number: CN114317873A
Application number: CN202111565974.0A
Authority: CN
Inventors: 王虎
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2022-04-12
Anticipated expiration: 2041-12-14
Also published as: CN114317873B

Abstract

The invention discloses a steelmaking slagging process, which comprises the following steps: carrying out slag remaining operation in a converter, adding scrap steel and molten iron, and adding a slagging material for blowing; after converting, carrying out slag splashing furnace protection operation after tapping; wherein, slag containing MgO is not added in the slagging converting process and the slag splashing furnace protecting operation process. The invention can realize the improvement of the steel scrap ratio or the iron-containing waste ratio, the reduction of the iron material consumption, the elimination of MgO in the slag, the convenient recycling of the steel slag and the realization of the efficient dephosphorization.

Description

Steelmaking slagging process

Technical Field

The invention relates to the field of steelmaking, in particular to a steelmaking slagging process.

Background

The basic tasks of steel making are decarburization, dephosphorization, desulfurization, harmful gas and inclusion removal, adjustment and component adjustment and the like, and the basic tasks of steel making are completed by means of oxygen supply, slagging, stirring, temperature rise and the like in the steel making process. The converter is the most important steelmaking equipment, the converter body consists of a furnace shell and a furnace lining, the furnace lining of the converter is formed by using bricks, tar dolomite and oil bricks from 60 to 70 years of the last century to using magnesia carbon bricks in 1990 and 1996, and the average furnace age of the converter is also improved from 170 and 540 to 924 and 3500. After 1996, a slag splashing furnace protection process is introduced into the domestic converter, namely molten steel slag is splashed and adhered to a furnace lining by high-pressure nitrogen after the slag at the end point of the converter is adhered to form a slag splashing layer so as to achieve the purpose of protecting the furnace lining. After the process is implemented, the furnace life of the converter in China at present is up to 3 ten thousand times.

The slag is a necessary product in the steel-making process and participates in metallurgical reactions, such as dephosphorization and desulfurization reactions, which are completed through a slagging process, and the purpose of converter steel-making slagging is to remove phosphorus and sulfur, reduce splashing, protect a furnace lining and reduce terminal oxygen. The four main components of the converter steelmaking slag system are CaO-SiO₂FeO-MgO, in which CaO, SiO₂The FeO and the FeO are main components for dephosphorization effect of molten steel. In generalThe slag contains 6-15% of MgO, and the MgO has the following effects:

firstly, lime dissolution in the initial smelting stage is accelerated, and early slagging is promoted.

Secondly, the SiO in the earlier furnace slag is reduced₂Erosion of the furnace lining.

Thirdly, slag materials containing MgO are added for slagging, so that the MgO content in the slag reaches a saturated state, the corrosion of the slag to a furnace lining can be reduced, and the slag splashing furnace protection operation is convenient. The determinant factor of the lining erosion is the activity of FeO in the slag, and the combination of MgO and FeO can improve the MgO concentration in the slag and reduce the erosion of FeO to the lining.

And fourthly, after slag splashing, MgO can also form periclase with a high melting point in the slag splashing layer, so that the erosion resistance of the slag splashing layer is improved.

As mentioned above, the adoption of MgO slag charge for slagging brings a series of advantages to converter steelmaking, and is particularly used for revolutionary changes of the furnace age brought by a slag splashing furnace protection process, so that the operation rate of the converter is greatly improved, and the capacity of the converter is greatly improved. Therefore, for decades, slagging using slag containing MgO in steel making has been a common consensus in the steel making field, and the skilled person has also focused great efforts on the specific research. For example, in chinese patent publication No. CN108330243A entitled s a method for reducing erosion of converter lining, slag MgO content was increased by adding dolomite and high-magnesium lime to the converter. And Chinese patent with publication number CN112981033A and name s, an automatic slag splashing control method and system for converter, wherein the content of end-point slag is adjusted to 10% -15%, and the MgO content in the end-point slag of converter blowing is adjusted to be supersaturated, so that the slag becomes sticky, and the slag splashing protection operation is facilitated.

However, since the MgO content in the slag is high, more MgO-containing slag such as dolomite needs to be added, which increases the amount of slag, increases the iron loss, consumes the heat energy for steel making, and lowers the scrap ratio. Empirical data on the effect of reducing the bath temperature by adding 1% coolant: 1 percent of dolomite is added, the cooling value is 20-24 ℃, 1 percent of scrap steel is added, the cooling value is 8-12 ℃, and the cooling value of the dolomite is more than 2 times of that of the scrap steel, which is shown in P123 of steelmaking science of Leya et al. Therefore, according to the value, 10 kg of dolomite is added in less steel per ton, more than 20 kg of steel per ton can be eaten, and the waste steel ratio of the converter is improved. In order to increase the scrap ratio of the converter, namely the ability of the converter to eat the scrap, a plurality of measures are also taken by the technical personnel in the field, one of the measures is to develop a plurality of exothermic agents such as aluminum, silicon and the like, as disclosed in a patent with the publication number of CN113005260A named as s-converter composite exothermic agent and a preparation method s, but the addition of the exothermic agents increases the steel-making cost, increases the slag quantity and has very limited increase of the scrap ratio. The Chinese patent with the publication number of CN112899431A and the name of s, which is a production process s for improving the ratio of converter scrap, discloses a process method for preheating scrap by using furnace gas in an elevated bunker, but the process is complex and is difficult to implement in actual production.

In addition, slag containing MgO used for steel making, such as light-burned dolomite, magnesium balls and the like, are produced from carbonate ore raw materials. On the one hand, natural resources are limited; on the other hand, thermal processing decomposition with carbonate ores consumes large amounts of heat energy and produces large amounts of CO2, increasing greenhouse gases.

In addition, the steel slag is a by-product of steel making, and the steel slag ultrafine powder can be used as a concrete blending material, but the MgO component in the steel slag and RO phase or periclase formed in the steel slag seriously affect the activity, stability and grindability of the steel slag, so that the steel slag can cause the problems of cracking and destruction of buildings and the like after being used as building materials, and the subsequent utilization of the steel slag is affected. Therefore, the technical proposal of the steel slag treatment process for reducing the MgO content in the steel slag is that after the slag is poured out of the furnace, powder is crushed and then MgO in the slag is reduced by a mineral separation device with high magnetic field strength, the treatment process investment is large, the recycling cost of the steel slag is increased, and the effect of removing MgO is not ideal, as disclosed in patent application with publication number sCN110937831As and with the patent name s of a process method s for reducing the magnesium content in the steel slag of a converter.

Therefore, the MgO-containing slag used for steelmaking brings a lot of benefits to steelmaking, but also has the problems of increasing the slag amount and iron loss in the steelmaking process, consuming steelmaking heat energy, reducing scrap ratio, increasing the recycling difficulty and cost of the steel slag and the like.

Disclosure of Invention

The invention aims to solve the problems of increased iron loss, steel-making heat energy consumption, scrap steel ratio reduction, increased utilization difficulty and cost of steel slag and the like in the steel-making process caused by MgO-containing slag used in the steel-making process at present. The invention provides a steelmaking slagging process, which does not add slag containing MgO during the whole slagging blowing process and the slag splashing furnace protection operation process of a converter, can realize the improvement of scrap steel ratio or iron-containing waste ratio, the reduction of iron material consumption, the elimination of MgO in furnace slag, the convenience of steel slag reutilization and the realization of the effect of high dephosphorization efficiency.

In order to solve the technical problem, the embodiment of the invention discloses a steelmaking slagging process, which comprises the following steps:

carrying out slag retention operation on the converter;

adding scrap steel and molten iron, adding slag making materials for slagging and blowing;

after converting, carrying out slag splashing furnace protection operation after tapping;

wherein, slag charge containing MgO is not added in the slagging converting process and the slag splashing furnace protecting operation process.

Further, the slag containing MgO comprises dolomite, light-burned dolomite, magnesite, high-magnesium lime and magnesium balls.

Furthermore, the slag containing MgO does not contain lime and limestone with MgO content less than 5 percent.

Further, the slagging material comprises one or more of lime, limestone, ore, sinter, return fines, pellets, iron scale, iron-dust-containing pellets, refining slag, bauxite, high-alumina powder, coal ash and fluorite.

As a specific implementation mode, when the converter double-slag remaining process is adopted, the steps are as follows:

s11: performing slag splashing furnace protection after the last furnace finishes steel discharging;

s12: after slag splashing is finished, the residual slag is completely left in the furnace, and the operation of completely remaining slag is adopted;

s13: adding scrap steel and molten iron;

s14: adding slag making material and blowing till the dephosphorization stage is finished;

s15: pouring out partial dephosphorization slag, and blowing in a decarburization stage until the end;

s16: tapping at the end point;

s17: slag splashing furnace protection operation;

s18: and (4) residue is remained.

Further, step S14 includes adding lime 0-10 kg/ton steel, FeO-containing slag material 15-45 kg/ton steel and/or Al-containing slag according to alkalinity of 1.0-1.6₂O₃Blowing 0-6 kg of slag material per ton of steel; in the decarburization period, according to the alkalinity of 2.0-3.5, 10-25 kg of lime and 10-30 kg of slag containing FeO are added per ton of steel to continue blowing till the end.

As a specific implementation mode, when the converter single slag process is adopted, the steps are as follows:

s21: discharging slag after the last furnace finishes discharging steel;

s22: leaving part of slag to implement slag splashing furnace protection operation;

s23: remaining slag in the furnace after the slag is splashed;

s24: adding scrap steel and molten iron, adding lime, slag containing FeO and/or Al in batches₂O₃Blowing the slag to a terminal point;

s25: tapping and deslagging;

s26: and (5) slag splashing and furnace protection operation.

Further, step S24 includes adding lime 20-45 kg/ton steel, FeO-containing slag charge 15-45 kg/ton steel and/or Al-containing slag charge according to the slag alkalinity 2.0-3.5₂O₃Blowing slag of 0-15 kg/ton steel.

Further, if the end-point slag is too thin, adding a carbonaceous reducing agent and then splashing slag when the gun is lifted after the converting is finished, during the tapping process, after the tapping or after partial slag is poured out, and adding a preset amount of lime or limestone during the splashing slag process.

Further, if the end-point slag is too thin, adding C or SiC, silicon mud balls or CaC after the blowing is finished₂And (3) reducing agent, stirring with nitrogen, after steel is discharged or part of slag is poured out, performing slag splashing furnace protection operation, and adding a preset amount of lime or limestone in the slag splashing process.

By adopting the technical scheme, the slagging blowing process is adoptedAnd slag containing MgO is not added in the slag splashing furnace protection operation, so that the effect of saving the slag containing the magnesium can be realized, and the consumption of production raw materials of the dolomite slag containing the magnesium, such as carbonate ore and the like, can be further reduced. Meanwhile, the energy consumption of calcination and the greenhouse gas CO during the processing of the magnesium carbonate material are greatly reduced₂And (4) discharging. The method can also realize the effects of reducing the slag amount, reducing the iron loss, increasing the scrap steel ratio or iron-containing waste materials, increasing the steelmaking capacity, having no MgO in the slag, having good dephosphorization effect, reducing the subsequent utilization cost, being better utilized and the like. In addition, high-level stock bins can be saved for other applications.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure. While the invention will be described in conjunction with the preferred embodiments, it is not intended that features of the invention be limited to these embodiments. On the contrary, the invention is described in connection with the embodiments for the purpose of covering alternatives or modifications that may be extended based on the claims of the present invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be practiced without these particulars. Moreover, some of the specific details have been left out of the description in order to avoid obscuring or obscuring the focus of the present invention. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below.

The steelmaking slagging process disclosed by the invention is applied to a converter with a magnesia carbon brick furnace lining. Specifically, the slag splashing protection operation is not carried out before the new furnace is blown for 900 times, and after the furnace is blown for 900 times, a fixed slag splashing layer is formed on the furnace lining of dozens of furnaces according to the traditional slag making process of MgO-containing materials, and the technical scheme disclosed by the embodiment is used. Or the technical scheme disclosed by the embodiment is directly adopted after the new furnace is in service for converting 900 furnaces.

The steelmaking slagging process disclosed by the embodiment of the invention comprises the following steps:

s1: carrying out slag retention operation on the converter;

s2: adding scrap steel and molten iron, and adding slag former for blowing;

s3: after converting, carrying out slag splashing furnace protection operation after tapping; wherein, slag containing MgO is not added in the whole slagging converting process and the slag splashing furnace protecting operation process.

Specifically, the MgO-containing slag includes dolomite, light-burned dolomite, magnesite, high-magnesium lime, magnesium balls and the like, but does not include lime and limestone with MgO content less than 5%.

Specifically, the slagging material comprises one or more of lime, limestone, ore, sinter, return fines, pellets, iron scale, iron-dust-containing pellets, refining slag, bauxite, high-alumina powder, coal ash, fluorite and the like.

Further, when the converter double-slag remaining process is adopted, the step S2 of adding the slag-making material for converting comprises adding 0-10 kg of lime per ton of steel, 15-45 kg of FeO-containing slag material per ton of steel and/or Al-containing slag according to the alkalinity of the primary slag of 1.0-1.6₂O₃Blowing 0-6 kg of slag charge per ton of steel, adding 10-25 kg of lime per ton of steel and 10-30 kg of slag charge containing FeO per ton of steel according to the alkalinity of 2.0-3.5 in the decarburization period, and continuously blowing till the end.

When the converter single slag process is adopted, in the step S2, the blowing process by adding the slag making material comprises the steps of adding 20-45 kg of lime per ton of steel, 15-45 kg of FeO-containing slag material per ton of steel and/or Al-containing slag according to the alkalinity of 2.0-3.5 of the slag₂O₃Blowing slag of 0-15 kg/ton steel.

Specifically, in step S3, after the end of converter blowing, when the viscosity of the slag at the end is appropriate, the slag is directly splashed and protected after the steel is discharged or a part of the slag is poured.

However, in the case that the slag at the end point is too thin after the end point of the converter blowing in some furnaces, the slag splashing can be performed after adding carbonaceous reducing agents such as coke particles, graphite-like particles and coal particles when the gun is lifted after the blowing is finished, during the tapping process, after the tapping or after partial slag is poured out, and the slag splashing operation can be continued to be completed by adding preset amount of lime or limestone during the slag splashing process, wherein the preset amount of lime or limestone is 1-4 kg/ton of steel.

As an alternative, for the heat with the slag too dilute at the end point, the furnace containing C or SiC, silicon balls or CaC can be added after the blowing is finished₂Reducing agent, and stirring with nitrogen gas to reduce FeO content in the slag and raise slag viscosity. After tapping or pouring out part of slag, carrying out slag splashing protection operation, adding a preset amount of lime or limestone in the slag splashing process, and continuing slag splashing operation until the slag splashing operation is finished, wherein the preset amount of lime or limestone can be 1-4 kg/ton of steel.

When the slag alkalinity R is 2.1-3.6 and TFe (total iron content) is 20%, the melting point of the slag is lowest when the MgO content in the slag is about 8%, and the melting point of the slag is increased along with the continuous reduction or continuous increase of the MgO content. The mechanism that the slag becomes sticky due to the supersaturated MgO content in the slag is that MgO with a high melting point is precipitated in the form of solid particles after being supersaturated in the slag, so that the friction force of the slag is increased, and the viscosity of the slag is increased. The same effect can be achieved by using lime instead of MgO to oversaturate CaO in the slag. Therefore, in the technical scheme of the application, MgO is not added, the effect of slag splashing protection is not affected, the slag FeO is reduced by adding reducing agents such as carbon and the like, and the end point thin slag is bonded by adding lime, so that the requirement of slag splashing protection technology on slag viscosity is met.

The slag forming by adding a proper amount of slag materials containing MgO can improve the fluidity of the slag and reduce the erosion of the slag to a furnace lining, and when the content of the slag materials exceeds the saturation degree of the slag materials, the slag becomes sticky, which is beneficial to the slag splashing protection operation and the improvement of the anti-erosion capability of a slag splashing layer. However, the effect of lowering the melting point of the slag, improving the fluidity of the slag and dissolving lime is far less than that of FeO, and the slag needs to be poured after the steel making. The added slag containing FeO not only has the function of dephosphorization by oxidation, but also can be reduced into molten steel. The slag splashing layer contains tricalcium silicate (melting point of C3S is 1900 deg.C) and dicalcium silicate (melting point of C2S is 2130 deg.C), total amount of the above two components is about 75% and small amount of periclase (melting point of 2800 deg.C), and the balance is low melting point component FeO (melting point of 1370 deg.C), 2 CaO. Fe₂O₃(C2F) phase(melting point 1220 ℃ C.).

Specifically, the difference between the converting reaction processes with and without adding MgO slag is as follows:

when oxygen blowing is started in converter smelting, Si element and part of Fe element in molten iron are firstly oxidized to generate SiO₂And FeO, a large amount of iron oxide present in the slag, the reaction formula is as follows:

2[Fe]+O₂＝2(FeO) (1)

[Si]+O₂＝SiO₂ (2)

2FeO+[Si]＝SiO₂+2[Fe] (3)

CaO and FeO belong to a cubic crystal system, and are in favor of FeO and SiO when solid lime exists₂Permeation and diffusion along the capillaries of the lime towards the inside thereof causes the lime to melt and the slag basicity starts to rise.

At the initial stage of blowing, when the alkalinity is 1, SiO in the slag₂The content can reach about 30 percent at most, when the free SiO₂Not fully bound with CaO:

in the presence of MgO, due to SiO₂The acid is large, and the calcium magnesium olivine inevitably reacts with MgO in a furnace lining or a slagging auxiliary material to form low-melting-point calcium magnesium olivine (CaO, MgO and SiO)₂) And magnesium multiflower rose pyroxene (3 CaO. MgO. SiO)₂) A mineral phase, which is about 80% to 90% of the entire mineral phase, and the reaction equations (4) and (5):

MgO+SiO₂+CaO＝CaO·MgO·SiO₂ (4)

2(CaO·MgO·SiO₂)+CaO＝3CaO·MgO·2SiO₂+MgO (5)

the blowing is continued, the FeO content is increased, the lime slaking slag is benefited, and CaO and magnesium rosepside (3 CaO. MgO. SiO)₂) Reacting to generate dicalcium silicate, and replacing a periclase phase (MgO), wherein the reaction formula is (6):

3CaO·MgO·2SiO₂+CaO＝2(2CaO·SiO₂)+MgO (6)

in the later stage of converting, iron oxide in the slag becomes acidic oxide (Fe) with the continuous increase of alkalinity, CaO content and TFe content₂O₃) By reaction with a portion of CaOGenerating low melting point calcium ferrite (CaO. Fe)₂O₃、2CaO·Fe₂O₃) Phase, the equations (7) and (8):

CaO+Fe₂O₃＝CaO·Fe₂O₃ (7)

2CaO+Fe₂O₃＝2CaO·Fe₂O₃ (8)

when no MgO is present in the slag, equations (4) and (5) become the following reaction processes:

FeO+SiO₂+CaO＝CaO·FeO·SiO₂ (9)

2(CaO·FeO-SiO₂)+CaO＝3CaO·FeO·2SiO₂+FeO (10)

with increasing slag basicity, the dissolved CaO does not need to replace MgO, especially at lower basicities R1.0-1.6 with full retained slag (basicity R2.0-R3.5) and with sufficient FeO-containing slag charge addition, reaction (9) (10) quickly shifts to reactions (11), (12) and (13):

(3CaO·FeO-2SiO₂)+CaO＝2(2CaO·SiO₂)+FeO (11)

CaO+Fe₂O₃＝CaO·Fe₂O₃ (12)

2CaO+Fe₂O₃＝2CaO·Fe₂O₃ (13)

in the presence of MgO, the reaction (4) produces forsterite (CaO. MgO. SiO)₂) Melting point of 1450 deg.C, reaction (5) to produce Mg-R-P-O (3 CaO. MgO. multidot.2SiO)₂) The melting point was 1550 ℃. In the absence of MgO, reaction (9) produces fayalite (CaO. FeO. SiO)₂) Melting point 1205 ℃ and calcium-iron-multiflora rose-stone (3 CaO. FeO. 2 SiO) produced by reaction (10)₂) The melting point of 1350 ℃ is higher than that of the reaction (9) and the reaction (10) in the absence of MgO, so that the melting points of the reaction (4) and the reaction (5) in the presence of MgO are 200 ℃ and 300 ℃. Therefore, at the initial stage of blowing (at a temperature of 1300 ℃ to 1400 ℃), since no MgO exists, the slag does not contain a forsterite phase and a perovskite phase, and a ferulonite phase (CaO. FeO. SiO) and a ferulonite phase (3 CaO. FeO. 2 SiO)₂) The melting point is lower and the fluidity is better. Along with the melting of lime, the alkalinity is improved, the link of gradually replacing MgO by CaO does not exist, and instead, the calcium-iron olivine (CaO. FeO. SiO)₂) Calcium-iron-dog rose-stone (3 CaO. FeO. 2 SiO)₂) The FeO in the steel slag is replaced by CaO, so that the FeO activity of the steel slag is greatly improved. Because there is no intermediate link in which MgO is replaced by CaO, the FeO activity of the slag after the replacement of FeO is improved, and the slag remaining operation and the added FeO-containing slag charge are added, CaO-FeO-SiO with low melting point can be quickly formed at the initial stage of blowing₂And (4) slag system. That is, FeO, (CaO. Fe) is formed under the condition of low alkalinity (R1.0-1.6)₂O₃)、(2CaO·Fe₂O₃)、(2CaO·SiO₂) The slag system of the phase, all the mineral phases are dephosphorized phases or solid phosphorus phases, so that the low-alkalinity slag in the initial stage of blowing has high-efficiency dephosphorizing capability.

Therefore, the initial slag with alkalinity of R1.0-R1.6 is quickly formed under the condition of no or little lime addition in the initial stage of blowing, and the strong dephosphorization capability is achieved under the condition of lower temperature (< 1400 ℃).

More (2 CaO. SiO) is formed under the condition of high alkalinity at the later stage of converting₂)、(3CaO·SiO₂)、FeO、(CaO·Fe₂O₃)、(2CaO·Fe₂O₃) Without periclase phase (MgO), the final slag with basicity of 2.0-3.5 is also more dephosphorizing. MgO has no dephosphorization effect, and the melting point of the formed mineral phase is 200-300 ℃ higher than that of the mineral phase formed by similar FeO. Therefore, under the same alkalinity, no MgO exists in the slag, no CaO, FeO and MgO are combined, and more free CaO and FeO exist in the slag, namely the activity of CaO and FeO is improved, so that no MgO is used for slagging and blowing, the slagging speed is higher, and the dephosphorization capability of the slag is stronger.

The implementation of the technical scheme is established on the basis of the slag splashing furnace protection process, and the degree of erosion of a slag splashing layer is slight at the initial stage of converter blowing; along with the continuous increase of the converting temperature, the melting point of the slag splashing layer is approached or exceeded, the slag splashing layer can generate the split melting phenomenon, namely along with the continuous increase of the temperature in the converting process, the low melting point components FeO (the melting point is 1370 ℃) and 2CaO FeO (C) in the slag splashing layer₂F) The phase (melting point 1220 ℃) melts and flows downAnd a high melting point of C₃S、C₂S, MgO phase remaining fixed to the furnace lining, where C₃S+C₂About 75% S and about 3-5% periclase phase. After multiple times of slag splashing circulation, a sintering layer and a bonding layer are formed on the side of the magnesia carbon brick due to chemical corrosion reaction, and the bonding layer is mainly solidified with C₂S、C₃S, MgO the melting point of the high melting point phase is obviously higher than the end slag of the converter, which can effectively resist the high temperature slag scouring in the later stage of converter blowing. The new slag splashing layer formed by each slag splashing on the surface of the bonding layer in the slag splashing layer can be melted to different degrees, but the next furnace is sprayed again, and the composition of the new slag splashing layer is consistent with that of the slag in the converting process.

According to the technical scheme, the furnace slag does not contain MgO, and a formed new slag splashing layer naturally does not contain MgO. And the corrosion of FeO in the slag to the furnace lining is mainly the chemical corrosion reaction of FeO in the slag and C and MgO in the magnesia carbon brick or MgO in a slag splashing layer. If MgO and C are not contained in the slag splashing layer, the chemical erosion reaction of FeO in the slag on the MgO and C in the slag splashing layer of the furnace lining can not occur. At the same time, a slag having a basicity of 2.0 to 3.5 is formed at the end point, in which the high-melting phase (C) is formed₂S+C₃S) can reach 75% or more, and has the function of resisting the scouring of high-temperature slag, thereby completely meeting the efficacy of slag splashing and furnace protection.

Therefore, the technical scheme of the application is applied to the steelmaking furnace with the furnace lining made of the magnesia carbon bricks, and under the precondition that the slag splashing protection furnace is provided, the material containing MgO is saved, the dephosphorization effect is better, all conditions of the slag splashing protection furnace are met, and the effect of the slag splashing protection furnace can be achieved.

Further, if Al is added to the slag system according to smelting requirements₂O₃The components can form an iron-aluminum-calcium salt phase, the desulfurization capacity of the slag system can be greatly improved, a better flowing state of slag can be kept in the smelting process, and splashing in the blowing process is reduced; meanwhile, the activity of the slag is greatly improved, and the utilization of the steel slag is facilitated.

According to the technical scheme, only slag materials such as lime and the like are added in the steelmaking process of the converter, and only slag materials containing FeO and/or slag materials containing Al are added according to smelting requirements₂O₃Slag or otherwiseSlag charge, not adding MgO slag charge, making the MgO content in the slag from 6% -15% to zero, forming a slag system without MgO and taking CaO-SiO2-FeO as the main component, having the following benefits:

1. and magnesium-containing slag is saved. According to conservative calculation of small slag quantity, for example, the production practice of the small slag quantity rapid dephosphorization of a large-scale converter is s < metallurgy journal >2010.10 period, and the amount of MgO in the slag poured out of each ton of steel is as follows: the slag amount was 83.5 kg/ton steel 8.28% (MgO content in slag) 6.91 kg/ton steel. According to the proportion of 35 percent of dolomite containing MgO, 6.91/35 percent of light-burned dolomite is added into the steel per ton, namely 19.7 kg/ton of steel, and the CaO amount brought in the dolomite is subtracted (19.7 x 40 percent, namely 7.89 kg/ton of steel), so that 19.7-7.89 percent of light-burned dolomite can be subtracted from the steel per ton, namely 11.8 kg/ton of steel. According to the unit price of light-burned dolomite of 600 yuan/ton, the cost can be reduced by 7 yuan/ton steel. The annual steel yield of a 100-ton converter is 164 ten thousand tons: (24h 60min 365 days)/32 min 100 ton/furnace, (smelting period 32 min/furnace), the dolomite cost is saved by 164 ten thousand tons 7 yuan/ton steel-1148 ten thousand yuan/year.

2. The magnesium slag such as dolomite can be saved, and the consumption of production raw materials of the magnesium slag such as carbonate ore can be reduced. Meanwhile, the energy consumption of calcination and the emission of greenhouse gas CO2 during the processing of the magnesium carbonate material are greatly reduced.

3. The amount of slag is reduced. The slag amount can be reduced by 11.8 kg/ton steel by 20% without using dolomite (the ignition loss of the dolomite is 20%) -9.41 kg/ton steel. The slag amount of a 100 ton converter is reduced by 9.41 kg/ton steel 164 ten thousand ton/year divided by 1000 kg/ton to 1.5 ten thousand ton/year in production year.

4. Increasing scrap ratio or iron-containing scrap. According to the cooling effect of dolomite and scrap steel, 11.8 kg of dolomite per ton of steel is subtracted without adding a heat generating agent and the like, the scrap steel ratio is improved by 11.8 x 2 to 23.6 kg per ton of steel, or an iron oxide material can be added additionally, and the scrap steel ratio of the converter is improved.

5. The steel-making capacity is increased. Under the condition of the same furnace capacity, 11.8 kilograms of dolomite are less added per ton of steel, 11.8 kilograms of steel can be added per ton of steel, 1 ton of steel can be produced per furnace by 100 tons of converters, according to the average profit of 450 yuan per ton of steel (the average profit of the steel per half a year in 2021), the profit of 450 yuan can be created per furnace by one 100 tons of converters (the average profit of 6 months in 2021), and the profit of 450 yuan 45-20250 yuan can be created per day by multiplying 24 hours by 60 minutes and dividing by 32 minutes (the smelting period is 32 min/furnace). 20250 yuan can be created in one year, 365 days per year 7391250 yuan, that is, more than 700 ten thousand yuan can be created in one 100 ton converter.

6. The lime consumption is reduced. Under the condition of lower alkalinity (1.0-1.6), no MgO in the slag consumes CaO and FeO, and the slag has better dephosphorization capability under the condition of low alkalinity, so that no MgO-containing slag charge is added, and the lime consumption is correspondingly reduced.

7. The slag does not contain MgO, and the cost for removing MgO is not needed when the subsequent slag is reused, so that the slag is better utilized.

Taking the steel yield of China exceeding 10 million tons in 2020 as an example, wherein 9 million tons of converter smelting needs to be counted by adding slag containing MgO, the scheme of the application can realize the purposes of saving light-burned dolomite by 11.8 kilograms per ton of steel by 9 million tons to 1062 million tons per year, correspondingly reducing the consumption of the dolomite above 2 million tons, the burning energy consumption and the emission of greenhouse gas, reducing the emission and the treatment of the steel slag above 1 million tons, saving the cost of the light-burned dolomite by 600 yuan/ton 1062 million tons per year to 63.7 million yuan per year, saving the consumption of the steel materials by 1062 million tons per year to 20% (the iron content of the slag) by 3000 yuan/ton of waste steel by 96.1 million yuan per year; yield improvement yield: 1 ton/100 ton converter 9 hundred million tons 450 yuan/ton steel 40.5 hundred million yuan/year. The total benefits are 200 billion year-created benefits, wherein the benefits brought by the increase of the ratio of scrap steel and the price difference of the scrap steel and the molten iron are not included; the scrap steel ratio is greatly improved, and the conditions of iron ore price increase and scrap steel surplus are relieved. Therefore, the slagging and the steelmaking without the MgO slag charge are beneficial to dephosphorization, do not influence slag splashing and furnace protection operation, and have great economic benefit and social benefit.

The effects of the technical scheme of the application are detailed in the following by each embodiment and comparative example of the double-slag and single-slag process:

the double-slag and slag remaining process comprises the following steps:

when the [ Si ] of the molten iron is more than 0.5 percent, a double-slag and slag-remaining process is generally adopted. The process comprises the following steps:

s13: adding scrap steel and molten iron;

s14: blowing till the dephosphorization stage is finished;

s15: pouring out the dephosphorized slag, and blowing at the decarbonization stage until the end;

s16: tapping at the end point;

s17: slag splashing furnace protection operation;

s18: and (4) residue is remained.

In the following, specific examples are further illustrated, the steelmaking equipment is a 120-ton converter, and the molten iron conditions are shown in table 1:

example 1

And after the steel is discharged from the previous furnace, slag splashing and furnace protection operation is carried out, and after slag splashing, the residual slag is completely left in the furnace, and the operation of leaving the slag completely is adopted. Adding 26t of scrap steel, 110t of molten iron, 3.5t of iron sheet and no lime. The converter mouth is shaken upwards to a zero position, the lower lance is ignited, after the oxygen lance is ignited successfully, the lance is quickly lowered to a nozzle to blow to a metal liquid level of 1.2m and a lower lance position, and the oxygen supply intensity is 3.02Nm³Min. t. The initial slag alkalinity is controlled to be 1.2-1.6, and the TFe content is less than 18%. Blowing oxygen for 4min, 10s, supplying oxygen for 23% of the total amount, lifting the lance while adding sludge pellets for 0.5t, then discharging slag, discharging the slag with the amount of 63%, and deslagging to obtain a slag sample. After slag discharging, the converter mouth is shaken upwards to a zero position, and continuous blowing is carried out for 3min, and lime is added in two batches for 3.5 t. Oxygen supply intensity 3.8Nm³The/min. t, the gun position is carried out in high-low. Adding 600kg of iron scale, 600kg of iron scale and 600kg of iron scale when oxygen is supplied for 50%, 60% and 70% in the blowing process, continuing blowing for 9min and ending at 15s, wherein the end point temperature is 1631 ℃, tapping and taking a slag sample.

In the embodiment, the end-point slag alkalinity is 3.2, TFe 12%, even though no MgO exists in the slag, the viscosity of the slag is proper, the slag is directly splashed and protected after the steel is discharged, the slag splashing time is 2min to 20s, the slag splashing effect is good, and the slag is completely remained in the next furnace after the slag splashing. The relevant slagging process parameters and results of this example are detailed in tables 2-4.

Example 2

The slagging process is essentially the same as in example 1. The relevant process parameters and results of the slagging blowing of this example are detailed in tables 2-4. In the embodiment, the end-point slag alkalinity is 3.1, the TFe is 16%, the end-point temperature is 1635 ℃, even though no MgO exists in the slag, the viscosity of the slag is proper, the slag is directly splashed to protect the furnace after steel is discharged, the slag splashing time is slightly 3min 01s, the slag splashing effect is good, and all slag is left in the next furnace after slag splashing.

Example 3

The slagging process was substantially the same as in example 1. The difference from the embodiment 1 is that 0.8 ton of lime is added after the blowing in the early stage of converting because the molten iron has high Si and low alkalinity of the remained slag. The relevant process parameters and results of slagging blowing in this example are shown in tables 2-4. In the embodiment, the end-point slag alkalinity is 2.5, the TFe is 18%, the end-point temperature is 1652 ℃, the slag is dilute, after steel is discharged, 120 kg of carbon powder is added before slag splashing, slag splashing furnace protection operation is carried out for 2min, the TFe content in the slag is reduced, the melting point of the slag is improved, 220 kg of lime is added in the slag splashing process, the slag is further sticky, slag splashing is continued for 50s, and a good slag splashing furnace protection effect is achieved. The slag remains in the furnace for the next furnace operation.

Example 4

The slagging process was substantially the same as in example 1, except that 0.88t of bauxite was added before blowing, as in example 1. Blowing oxygen for 4min08s to provide 25% of total oxygen supply due to Al in the slag₂O₃The content is high and reaches 6.23 percent, the slag fluidity is good, the low-lance blowing is completed, the lance is not lifted to blow the slag, the slag is directly discharged after the lance is lifted, and the slag sample is taken after the slag is poured. After deslagging, the converter mouth is shaken upwards to a zero position, the slag material is added, and blowing is continued for 9min02s, wherein the end point temperature is 1651 ℃.

The end-point slag alkalinity of the embodiment is 2.4, TFe 22%, the slag is rare, after steel is discharged, 150 kg of carbon powder is added before slag splashing, slag splashing is carried out for 2min, the TFe content in the slag is reduced, the melting point of the slag is improved, then 200 kg of lime is added in the slag splashing process, the slag is further sticky, slag splashing is continued for 50s, the slag splashing furnace protection effect is good, and the slag is left in the furnace for the next furnace operation. The relevant process parameters and results of the slagging blowing of this example are shown in tables 2-4.

Comparative example 1:

to the lastAnd (3) after the steel is discharged from the furnace, slag at the end point is splashed to protect the furnace, splashed to dry and solidified and then is completely left in the furnace, the operation of reserving the whole slag is adopted, 107 tons of molten iron are added, 19 tons of scrap steel and 2.2 tons of iron sheet are added: after the operations of adding molten iron, adding scrap steel and iron sheet are finished, the gun is put down for ignition, after the oxygen gun is successfully ignited, the gun is quickly lowered to the low gun position where the spray head is 1.2m above the metal liquid level for blowing, and the oxygen supply intensity is 3.0Nm³Min.t, no slag charge is added, the early-stage slag alkalinity is controlled to be 1.4, the MgO content is less than 7.5 percent, and the TFe content is less than 18 percent. Blowing oxygen for 5min2s, stopping blowing, lifting the lance, adding sludge pellets for 0.48t, and discharging slag, wherein the amount of discharged slag is 60% of the total amount of slag. And (6) taking a slag sample. After deslagging, the converter mouth is shaken upwards to a zero position, 3.75t of lime is added in two batches within 3 minutes of blowing, 1.4t of light-burned dolomite is added together with the first batch of lime, and the oxygen supply intensity is 3.6Nm³The/min. t, the gun position is carried out in high-low-high. 500kg, 500kg and 500kg of iron scales are respectively added when 50%, 60% and 70% of oxygen is supplied in the blowing process, the blowing is continued for 10min by a gun, the time is 01s, the end point temperature is 1656 ℃, tapping is carried out, and sampling is carried out, wherein the components of the sample are shown in Table 4. Slag alkalinity is 3.3, TFe 22%, slag is dilute, 300 kilograms of raw dolomite are added into the furnace after steel is discharged, slag splashing protection operation is started, and the slag splashing time is 3min02 s. The slag remains in the furnace for the next furnace operation. The relevant slagging process parameters and results of this example are detailed in tables 2-4.

TABLE 1 composition and temperature of molten irons of examples and comparative examples

TABLE 2 amount of charge in dephosphorization phase in the example of the two-slag-remaining method

As can be seen from Table 2 above, in examples 1 to 4 in which no MgO slag was added, the steel charge, scrap ratio and iron-containing scrap (scale term in the above table) ratio were increased as compared with comparative example 1 in which MgO slag was added, using the two-slag remaining process.

TABLE 3 main component and phosphorus content of semisteel of dephosphorized slag in each example

TABLE 4 amount of slag, oxygen supply time, main component of decarburization slag, molten steel [ P ] and iron and steel consumption in decarburization period of each example

As can be seen from tables 3 and 4 above, in examples 1 to 4 in which the MgO slag is not added, the blowing time in the dephosphorization period is short (oxygen supply time is short) and the dephosphorization efficiency is improved, compared with comparative example 1 in which the MgO slag is added, by using the double slag remaining process; the molten steel has low terminal point P% and high dephosphorization rate; the consumption of steel materials is reduced, and the consumption of lime is reduced; and the slag is free of MgO.

The single slag process comprises the following steps:

the single slag process comprises the following steps:

s21: discharging slag after the last furnace finishes discharging steel;

s23: remaining slag in the furnace after the slag is splashed;

s25: tapping and deslagging;

s26: and (5) slag splashing and furnace protection operation.

The following examples are provided to illustrate the molten iron conditions of the examples in Table 5 below.

Example 5

The specific slagging process is as follows:

after the steel is discharged from the previous furnace, 50% of slag is poured out, 50% of slag is left, slag splashing protection operation is carried out, and residual slag is left in the furnace after splashing. 20.2t of scrap steel is added, 110t of molten iron is added, 3t of iron sheet is added, the converter mouth is shaken upwards to the zero position, the lower lance is ignited, after the oxygen lance is ignited successfully, the constant-pressure lance position changing operation is adopted, the oxygen supply flow is 3.6Nm/t/min, the smelting lance position is controlled to be 1.2-1.8 m, 0-36% of oxygen supply is carried out, 5.4t of lime is added in three batches, the total amount of the lime is 5.4t, 600kg of iron sheet oxide is added when 40%, 50%, 60% and 70% of oxygen supply are carried out respectively, and the blowing is carried out for 14min06 s. In the embodiment, when the smelting of the converter is finished, the end point temperature is 1628 ℃, the end point phosphorus is 0.009%, the alkalinity of the final slag is 3.0, the TFe of the final slag is 15%, the viscosity of the slag after tapping is proper, the slag is directly splashed after partial slag is poured out, the slag splashing time is 2min and is 20s, and the slag is left in the next furnace operation after splashing.

The relevant process parameters and results of slagging blowing are shown in tables 6 and 7.

Example 6

The slagging process was as in example 5. Except that 1.9t of bauxite was charged to the converter along with the first batch of lime after the start of the blow. Slag alkalinity at the end of blowing of 3.1, TFe 13%, Al₂O₃10 percent, the end temperature is 1636 ℃, the slag is dilute, part of the slag is poured out after tapping, 150 kg of carbon powder is added into the furnace, 250 kg of lime particles are added when slag splashing is carried out for 2min, and the slag is left in the furnace for the next furnace operation after slag splashing is carried out for 55 s.

Example 7

The slagging process was as in example 5. The alkalinity of the slag at the blowing end point is 3.1, TFe19 percent, the end point temperature is 1648 ℃, and the slag is thinner. And after the steel is discharged, pouring out partial slag, adding 120 kg of carbon powder into the furnace, adding 200 kg of lime stone particles when slag splashing is carried out for 2.0min, and after slag splashing is carried out for 1min, keeping the slag in the furnace for the next furnace operation.

The relevant process parameters and results of slagging blowing are shown in tables 5, 6 and 7.

Example 8

The slagging process was as in example 5. The final slag alkalinity is 2.5, TFe 25%, the final temperature is 1657 ℃, and the slag is dilute. And after steel is discharged, 140 kg of carbon powder is added into the furnace, 200 kg of lime is added when slag splashing is carried out for 2min, and after slag splashing is continued for 50s, slag is left in the furnace for the next furnace operation.

Comparative example 2

The slagging process was as in example 5. Except that 1.32t of light burned dolomite was added with the first batch of lime. The basicity of the slag at the blowing end point is 3.4, TFe 18%, the end point temperature is 1663 ℃, and the slag is relatively dilute. After the steel is discharged, 135 kg of carbon powder is added into the furnace, 220 kg of raw dolomite is added when slag splashing is carried out for 2min, and after slag splashing is carried out for 50s, the slag is left in the furnace for the next furnace operation.

TABLE 5 molten iron composition and temperature of each of examples and comparative examples

Examples	C/％	Si/％	Mn/％	P/％	S/％	T/℃
							Example 5	4.3	0.40	0.23	0.110	0.021	1295
Example 6	4.5	0.42	0.32	0.100	0.025	1310
							Example 7	4.4	0.32	0.15	0.112	0.018	1298
Example 8	4.6	0.38	0.18	0.130	0.015	1320
							Comparative example 2	4.5	0.37	0.13	0.131	0.017	1323

TABLE 6 Single-slag method of each example and comparative example of the metal charge and slag charge

As can be seen from Table 6 above, in examples 5 to 8 in which no MgO slag was added, the steel charge, the scrap ratio, and the iron-containing scrap (in the above table, iron oxide increased by about 20 kg/t) ratio were increased as compared with comparative example 2 in which MgO slag was added.

TABLE 7 Single-slag method examples and comparative examples end-point slag main component and other smelting parameters

As can be seen from Table 7 above, in examples 5 to 8 in which a single slag process was employed and no MgO slag was added, the blowing time was short (oxygen supply time was short) and the dephosphorization efficiency was high, compared with comparative example 2 in which MgO slag was added; the molten steel has low end point P%, low iron and steel material consumption and no MgO in slag.

Therefore, no matter the double-slag remaining process or the single-slag process is adopted, compared with the comparative examples of the corresponding processes, the embodiment adopting the technical scheme of the invention has basically consistent slagging process, only MgO-containing slag is not added in the blowing process of the embodiment adopting the technical scheme of the invention, and 10 kg/ton of steel light-burned dolomite is added in the comparative examples, so that according to the analysis and comparison of the tables 1 to 7, the technical scheme of the invention can realize the improvement of the loading capacity, the scrap ratio or the iron-containing scrap ratio; the blowing time is short, and the dephosphorization efficiency is high; the molten steel has low terminal point P% and high dephosphorization rate; the consumption of steel materials is reduced, and the consumption of lime is less; the slag containing MgO is not added, and the slag does not contain MgO, so that the subsequent slag utilization is facilitated, the later-period utilization cost is reduced, and the like.

According to the observation of 100-furnace slag splashing protection operation, no matter the slag-remaining double-slag process or the single-slag process, the slag splashing protection operation is normal, and the slag splashing layer protection effect is good.

While the invention has been described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing is a more particular description of the invention than is possible with reference to the specific embodiments, which are not to be construed as limiting the invention. The process modifications made by those skilled in the art based on the principles of the present invention to the process parameters and details such as slag basicity, slag charge and charge time, oxygen supply parameters, etc. should be within the scope of the claims appended hereto.

Claims

1. A steelmaking slagging process is characterized by comprising the following steps:

carrying out slag retention operation on the converter;

wherein, slag containing MgO is not added in the slagging converting process and the slag splashing furnace protecting operation process.

2. The steelmaking slagging process according to claim 1, wherein the MgO-containing slag includes dolomite, light burned dolomite, magnesite, high magnesium lime, magnesium balls.

3. The steelmaking slagging process according to claim 1, wherein the MgO-containing slag does not include lime and limestone having an MgO content of < 5%.

4. The steelmaking slagging process according to claim 1, wherein the slagging material comprises one or more of lime, limestone, ore, sinter, return fines, pellets, scale, iron-containing dust pellets, refinery slag, bauxite, high alumina fly ash, fluorite.

5. The steelmaking slagging process according to claim 1, wherein, when a converter double slag remaining process is adopted, the steps are as follows:

s13: adding scrap steel and molten iron;

s16: tapping at the end point;

s17: slag splashing furnace protection operation;

s18: and (4) residue is remained.

6. The steelmaking slagging process according to claim 5, wherein step S14 includes adding lime 0-10 kg/ton steel, 15-45 kg/ton steel with FeO slag and/or Al with the basicity of the primary slag of 1.0-1.6₂O₃Blowing 0-6 kg of slag material per ton of steel; in the decarburization period, according to the alkalinity of 2.0-3.5, 10-25 kg of lime and 10-30 kg of slag containing FeO are added per ton of steel to continue blowing till the end.

7. The steelmaking slagging process according to claim 1, wherein, when a converter single slag process is adopted, the steps are as follows:

s21: discharging slag after the last furnace finishes discharging steel;

s23: remaining slag in the furnace after the slag is splashed;

s25: tapping and deslagging;

s26: and (5) slag splashing and furnace protection operation.

8. The steelmaking slag-making process as claimed in claim 7, wherein the step S24 includes adding lime in an amount of 20-45 kg/ton steel, 15-45 kg/ton steel of slag containing FeO and/or Al in accordance with the basicity of slag of 2.0-3.5₂O₃Blowing slag of 0-15 kg/ton steel.

9. The steelmaking slag making process as claimed in claim 1, wherein if the slag at the end point is too thin, slag splashing is performed after adding the carbonaceous reducing agent or lime or limestone when the lance is lifted at the end of converting, during the tapping, after the tapping or after pouring out a part of the slag, and a predetermined amount of lime or limestone is added during the slag splashing.

10. The steelmaking slagging process according to claim 1, wherein if the end point slag is too dilute, after the end of the blow, C or SiC, silicon balls or CaC are added₂And (3) stirring by using nitrogen gas, after steel is discharged or part of slag is poured out, performing slag splashing furnace protection operation, and adding a preset amount of lime or limestone in the slag splashing process.