CN113249544A

CN113249544A - Process for quenching and tempering steel slag into refining slag and deoxidizing and desulfurizing molten steel

Info

Publication number: CN113249544A
Application number: CN202110429134.5A
Authority: CN
Inventors: 王虎
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-04-16
Filing date: 2021-04-16
Publication date: 2021-08-13

Abstract

The invention discloses a deoxidation and desulfurization process for tempering steel slag into refining slag and molten steel, which comprises the following steps of: adding raw materials including molten iron, waste steel, lime and light-burned dolomite into a steelmaking furnace, and carrying out slagging blowing according to the slag alkalinity of 2.5-3.5 and the MgO content of 5-8%; adding Al-containing material to a steel-making furnace in batches₂O₃Adding a reducing agent, and stirring slag by nitrogen for 3-6 minutes at the same time, wherein the components of the end-point slag of the steel-making furnace are controlled as follows: r2.5-3.5, Al₂O₃18-26 percent of MgO, 5-8 percent of (FeO + MnO) < 3.0 percent and P2O5 < 0.5 percent; and tapping with slag. The invention can realize the tempering of the steel slag into the refining slag at the blowing end point of the converter, reduce the cost of the refining slag and further realize the purpose of refining the steel slagAnd the technical effects of no slag blocking, slag carrying and steel tapping, molten steel deoxidation, desulfurization and no rephosphorization of the molten steel are achieved.

Description

Process for quenching and tempering steel slag into refining slag and deoxidizing and desulfurizing molten steel

Technical Field

The invention belongs to the field of steelmaking, and particularly relates to a deoxidation and desulfurization process for tempering steel slag into refining slag and molten steel.

Background

In general, in the steelmaking process, the main task is to remove C and P in molten steel, and [ S ] and [ O ] remain in the molten steel, after the steelmaking smelting of many steel types, the molten steel needs to be subjected to external slag washing or external refining for deoxidation and desulfurization, and the external slag washing or refining needs to be added with synthetic refining slag.

At present, the synthetic refining slag can be divided into a material distribution type, a sintering type and a premelting type according to different processing modes. The material preparation method is characterized in that slag materials such as lime, light-burned bauxite, calcium carbide or fluorite and the like are added into a steel ladle according to a proportion, and the problems of slow slag forming time, high power consumption, large molten steel temperature drop, short white slag keeping time, poor desulfurization effect and the like exist. The sintering type synthetic refining slag is formed by sintering below the melting point temperature of slag charge, the slag forming speed is high, but gas is brought into molten steel due to pores, and the quality of steel billets is affected.

The pre-melting type synthetic refining slag needs to be pre-melted and processed in a heating device, has the advantages of low melting point, high slag forming speed, small heat loss, strong deoxidation and desulfurization capacity and the like, and has the problems of high energy consumption and high cost. Therefore, the refining slag with the best molten steel quality improvement effect at present has the highest energy consumption and the highest cost, and the steel-making cost can be greatly increased.

Meanwhile, the FeO content in the converter blowing end slag and the oxygen content of the molten steel are higher, the FeO content in the end slag and the oxygen activity of the molten steel are the root of inclusions in the steel, and the FeO in the slag is easy to react with acid-soluble aluminum in the molten steel to generate inclusions in the casting process to cause molten steel pollution. And the steel slag and the oxygen-containing substances in the molten steel influence the desulfurization effect, so the slag is required to be blocked when the steel is tapped from the converter, but in the actual production, the slag is difficult to be completely blocked, a part of the steel slag always enters the molten steel during tapping, molten steel rephosphorization is easy to cause, and in the process of tapping deoxidation or slag washing refining, because the tapping time is short and reaction cannot be fully performed, the FeO of the top slag is difficult to be reduced to be less than 3% after the molten steel is deoxidized or the slag is washed, so the desulfurization effect of the slag washing or refining is influenced.

In order to reduce the FeO content in the end-point slag and the oxygen in the molten steel, the technical scheme is to reduce the FeO content in the slag to reduce the oxygen activity in the molten steel and realize gasification dephosphorization of the slag, but as the FeO reduction content in the slag is reduced, the slag gradually becomes sticky and the reaction is gradually terminated, the residual amount of FeO in the slag is still high, phosphorus also remains a lot, the reduction range of the oxygen in the molten steel is limited, and S in the molten steel is not reduced.

Meanwhile, the phenomenon of rephosphorization of molten steel can occur due to weak oxidizability or reduced slag alkalinity along with the reduction of FeO content in the process of removing FeO, and some measures are generally taken to prevent rephosphorization by increasing the FeO content in slag. For example, in "a method for reducing the amount of rephosphorization during converter steelmaking" (201010260158.4), it is proposed that FeO powder is added into the converter and stirred with oxygen during the converter-like process to make FeO in the slag > 15% to prevent the steel from being returned to the converter, etcAnd (5) returning phosphorus by water. In addition, in order to ensure that the alkalinity of the slag is reduced and the lime dosage is reduced, SiO2 and Al in the furnace charge for converter steelmaking₂O₃The content is strictly limited.

Therefore, FeO and P2O5 in the final slag of steel making are practically difficult to be removed completely, and rephosphorization is also a problem in the process of removing FeO, and excessive residual FeO and P2O5 in the final slag limits the use of high added value in the final slag.

Disclosure of Invention

The invention provides a deoxidation and desulfurization process for quenching and tempering steel slag into refining slag and molten steel, which aims to solve the problems of deficiency and high production cost of the existing synthetic refining slag and the problem of how to deeply reduce FeO and P2O5 in the steel slag by using converter smelting end-point slag without causing molten steel rephosphorization, so that the steel slag is quenched and tempered into the refining slag at the converter blowing end-point, the purpose of not stopping slag and tapping is achieved, the technical effects of deoxidation and desulfurization of the molten steel, not rephosphorization of the molten steel and reduction of the cost of the refining slag are achieved.

The technical scheme of the invention is as follows:

a deoxidation and desulfurization process for tempering steel slag into refining slag and molten steel is characterized in that raw materials including molten iron, scrap steel, lime and light-burned dolomite are added into a steel furnace, and slagging and blowing are carried out according to the alkalinity of the slag of 2.5-3.5 and the MgO content of 5-8%, and the deoxidation and desulfurization process comprises the following steps:

adding Al-containing material to a steel-making furnace in batches₂O₃The method comprises the following steps of adding a reducing agent into the materials and the reducing agent, stirring slag by using nitrogen, and controlling the components of the end-point slag of the steel-making furnace to be as follows after the nitrogen stirring is finished: r2.5-3.5, Al₂O₃18-26 percent of MgO, 5-8 percent of (FeO + MnO) < 3.0 percent and P2O5 < 0.5 percent;

and tapping with slag.

Further, Al is added to the converter₂O₃The specific steps of the materials and reducing agent are as follows:

adding part of Al into the converter in one time or in batches before the converter blowing is finished₂O₃Material, adjusting slag to Al before blowing is stopped at converting end₂O₃The content is 9% -16%;

stopping blowingThen, part of Al is added into the furnace₂O₃The material and the first reducing agent or the second reducing agent, and simultaneously, the oxygen lance is switched from oxygen to nitrogen, and the slag is stirred by the nitrogen for about 20-60';

then adding the rest Al₂O₃Continuously stirring the slag for 1-4 min by using nitrogen, controlling the alkalinity of the slag to be R2.5-3.5, and controlling the slag to be Al₂O₃ 18％-26％，MgO 5％-8％，(FeO+MnO)＜3.0％，P2O5＜0.5％。

Further, Al is added into the arc furnace₂O₃The specific steps of the materials and reducing agent are as follows:

adding Al into the furnace in one step or in steps before the initial stage of blowing or the end of the oxidation period₂O₃Material, slag Al before blowing out₂O₃Adjusting the content to 9% -16%;

after the oxidation period is over, part of the Al is added into the furnace₂O₃The material and the first reducing agent or the second reducing agent, and at the same time, the oxygen lance is switched from oxygen to nitrogen or directly uses a gas lance to stir the slag by nitrogen or gas for about 20-60';

then adding the rest Al₂O₃Continuously stirring the slag with nitrogen or coal gas for 1-4 min to control the slag components to be R2.5-3.5, and Al₂O₃18-26％，MgO5-8％，(FeO+MnO)＜3.0％，P2O5＜0.5％。

Further, the Al content is₂O₃The material is one of bauxite, refining slag or metal calcium slag.

Furthermore, the addition amount of the reducing agent is 2-8 kg/ton steel, and the reducing agent contains Al₂O₃The material addition amount is 8-20 kg per ton steel.

Further, the reducing agent is divided into a first reducing agent and a second reducing agent, wherein the first reducing agent is one of coal particles, coke particles, graphite and other carbonaceous materials; the second reducing agent is one or two of silicon mud, aluminum iron, aluminum particles, aluminum ash, calcium carbide, silicon carbide and CaSi;

the adding amount of the first reducing agent C is 0-2 kg/ton steel, and the adding amount of the second reducing agent C is 2-8 kg/ton steel.

Further, the nitrogen gas may be replaced with coal gas.

A process for refining steel slag includes adding raw materials including molten iron, waste steel, light-burned dolomite and lime into converter, blowing for slagging with basicity of slag being 1.3-2.2 and MgO 5-8%, and adding Al-contained raw materials to steel-smelting furnace in batches₂O₃Adding a reducing agent and stirring slag by nitrogen gas;

controlling the components of the initial slag of the converter as follows: r0.8-2.0, Al₂O₃8-16％、MgO5-8％、(FeO+MnO)＜3.0％、P2O5＜0.5％。

Further, the Al-containing material is added into the steelmaking furnace in batches₂O₃The steps of material and reducing agent include:

adding part of Al into the converter in one time or in batches before the end of the initial blowing period of the converter₂O₃Material, slag Al before blowing out₂O₃The content is controlled to be 3-10%;

after blowing is stopped, Al is added into the furnace₂O₃The material and the first reducing agent or the second reducing agent, and simultaneously, the oxygen lance is switched from oxygen to nitrogen, and slag is stirred by the nitrogen for 20-60';

then adding the rest Al₂O₃Continuously stirring the slag for 1-4 minutes by using the materials and the second reducing agent;

and (4) discharging initial slag, water quenching and magnetic separation.

Further, the Al content is₂O₃The material is one of bauxite, refining slag or metal calcium slag; the reducing agent is divided into a first reducing agent and a second reducing agent, wherein the first reducing agent is coal particles, coke particles, graphite and other carbonaceous materials; the second reducing agent is one or two of silicon mud, aluminum iron, aluminum particles, aluminum ash, calcium carbide, silicon carbide and CaSi.

Further, the adding amount of the first reducing agent C is 0-2 kg/ton of steel, and the adding amount of the second reducing agent C is 2-8 kg/ton of steel; the Al-containing component₂O₃The material addition amount is 8-20 kg per ton steel.

The technical scheme of the application has at least the following beneficial effects:

1. the technical scheme of the invention is that the steel slag is modulated in the converter steelmaking process, the steel slag is gradually quenched and tempered into refining slag, the equipment and reaction conditions of steelmaking are utilized, additional equipment and factory building are not needed, the production cost of the synthetic slag is greatly reduced, and the steel slag is utilized with high added value.

2. According to the invention, after the converter is finished, the steel slag is tempered into synthetic slag, so that slag stopping is not needed during steel tapping, and the slag stopping cost is saved; meanwhile, during tapping, partial steel slag and molten steel can be mixed for tapping, the steel slag carries out slag washing on the molten steel, a ladle refining process after a furnace can be cancelled for a plurality of steel types, the modification of top slag of the ladle is not needed, the cost of externally adding and synthesizing refining slag, a modifier or a desulfurizer is saved, and the pollution is reduced; meanwhile, the molten steel dephosphorization, deoxidation and desulfurization are realized by utilizing the self process of steel making, the process is reduced, the processing time and cost are reduced, and the quality of the molten steel is improved.

3. Because Al is added by using aluminum reducing agent or reducing agent₂O₃The auxiliary materials are modified through reaction, the melting point of the furnace slag is reduced, the temperature of the furnace slag is greatly increased, and Al in the furnace slag is controlled₂O₃10-25 percent of MgO and 5-8 percent of MgO, FeO and MnO in the slag are basically reduced, P2O5 is gasified, the phosphorus return during tapping is avoided, and the yield of molten steel and manganese elements is greatly improved.

4. The steel slag left in the ladle after the slag washing is poured can be used for slag washing of the next tapping furnace, and the refining cost is further reduced.

5. Slag Al in converting process₂O₃High content (9-14%), good fluidity of steel slag, low alkalinity control R2.5-3.2, no drying and splashing in the smelting process, and reduced blowing loss.

6. The invention greatly reduces the FeO content in the end-point slag, thereby reducing the oxygen activity of the molten steel, and no deoxidizing agent such as silicon, aluminum and the like is needed in the tapping process, so that no acid reaction product is generated, the alkalinity of the slag discharged is not reduced, and the desulfurization effect is good.

7. The end-point slag of the invention has low FeO content and low oxidability, and simultaneously contains a certain amount of MgO, so that the slag plays a role in heat preservation and simultaneously reduces the corrosion of the ladle lining.

Detailed Description

The technical scheme of the application is described in detail by combining specific embodiments as follows:

the invention discloses a deoxidation and desulfurization process for tempering steel slag into refining slag and molten steel, which comprises the following technical scheme that the tempering process aiming at the initial slag of a converter comprises the following steps:

adding molten iron, waste steel, lime, light-burned dolomite and other raw materials into the converter, slagging and blowing according to the slag alkalinity of 1.3-2.2 and the MgO 5-8%, wherein in actual operation, lime can be omitted according to the slag alkalinity and the slag amount; by batchwise addition of Al-containing substances to the steel-making furnace₂O₃Adding a reducing agent and stirring the slag with nitrogen for 3-6 minutes; controlling the components of the initial slag of the converter as follows: r0.8-2.0, Al₂O₃ 8-16％、MgO 5-8％、(FeO+MnO)＜3.0％、P2O5＜0.5％。

And discharging initial slag, water quenching, and magnetically separating to remove iron. So as to obtain the synthetic refining slag with low alkalinity.

The quenching and tempering process aiming at the converter end-point slag and the electric furnace steel slag comprises the following steps:

adding molten iron, waste steel, lime, light-burned dolomite and other raw materials into a converter or an electric furnace, slagging and blowing according to the slag alkalinity of 2.5-3.5 and MgO5-8 percent, and adding Al-containing raw materials into a steelmaking furnace in batches₂O₃Adding a reducing agent and stirring the slag with nitrogen for 3-6 minutes; controlling the components of converter end-point slag or electric furnace end-point oxidizing slag as follows: r2.5-3.5, Al₂O₃18-26％、MgO 5-8％、(FeO+MnO)＜3.0％、P2O5＜0.5％。

Tapping steel with slag, then tapping the final slag, water quenching, magnetic separation and iron removal to obtain the medium and high alkalinity synthetic refining slag.

In the two processes, the reducing agent is added in an amount of 2-8 kg per ton of steel. The reducing agent is divided into a first reducing agent and a second reducing agent. The first reducing agent is coal particles, coke particles, graphite and other carbonaceous materials; the second reducing agent is one or two of silicon mud, aluminum iron, aluminum particles, aluminum ash, calcium carbide, silicon carbide and CaSi.

The Al-containing component₂O₃The material is one of bauxite, refining slag, metal calcium slag and the like.

The adding amount of the first reducing agent is 0-2 kg/ton steel, the adding amount of the second reducing agent is 2-8 kg/ton steel, and the second reducing agent contains Al₂O₃The material addition amount is 8-20 kg per ton steel. When the amount of the slag is too large or the oxidability of the slag is too high, a small amount of a first reducing agent C can be added firstly to reduce the cost of the reducing agent, and meanwhile, the reducing agent cannot be excessive, so that the increase of the C in the molten steel is prevented; and the second reducing agent has enough reduction reaction to generate enough heat to increase the temperature of the slag.

Meanwhile, the nitrogen in the technical scheme can be replaced by coal gas.

In the scheme, the nitrogen stirring can be performed by a top blowing gun or a bottom blowing gun.

In addition, fluorite can be properly added in the technical scheme of the invention to increase CaF2 in the slag, so that the refining slag with CaF2 is formed.

At present, the refining slag contains CaO-CaF₂Slag system, CaO-Al₂O₃Slag system, CaO-Al₂O₃-CaF₂Slag system, CaO-CaF₂-MgO-SiO₂The slag systems have advantages and disadvantages. And CaO-CaF₂the-MgO-SiO slag system is also a slag system which is widely applied at present, and the R2.5-3.0 slag has the strongest desulfurization capability. According to the technical scheme, the steel slag can be tempered into the slag system which is most widely applied to the current synthetic refining slag, and the refining slag with different alkalinity can be tempered by different tempering processes of initial slag and key slag.

In specific applications, the following cases are divided:

in the specific scheme I, the quenching and tempering process for the initial slag comprises the following steps:

the converter carries out double-slag remaining operation. Adding molten iron, waste steel, lime or not, light-burned dolomite and other raw materials, and slagging and blowing according to the slag alkalinity of 1.3-2.2 and the MgO content of 5% -8%.

Adding part of Al into the converter in one time or in batches before the end of the initial blowing period of the converter₂O₃Material, slag Al before blowing out₂O₃The content is controlled to be 3-10%.

After blowing is stopped, Al is added into the furnace from a high-level stock bin₂O₃The material and the first reducing agent or the second reducing agent, while the lance is switched from oxygen to nitrogen, the slag is stirred with nitrogen for 20 "-60", and then the remainder of the Al-containing slag is added₂O₃The materials and the second reducing agent continue to stir the slag for 2-5 minutes.

Controlling the slag component to be R0.8-2.0, Al₂O₃8％-16％，MgO 5％-8％，(FeO+MnO)＜3.0％，P₂O₅Is less than 0.5 percent. Then slag is discharged, water quenching and magnetic separation are carried out to remove metallic iron, and then the low-alkalinity synthetic refining slag is obtained.

In the second concrete scheme, the quenching and tempering process aiming at the converter end slag comprises the following steps:

the converter carries out slag retention operation. Molten iron, waste steel, lime, light-burned dolomite and other raw materials are added into the converter, and slagging and blowing are carried out according to the slag alkalinity of 2.5-3.5 and MgO 5-8%.

Adding a part of Al into the converter from an overhead bunker in one time or in batches before the initial stage or the end point of the converter blowing₂O₃Material, adjusting slag basicity to Al before blowing is stopped at converting end₂O₃9％-16％。

After blowing is stopped, part of Al is added into the furnace from an overhead bunker₂O₃The material and the first reducing agent or the second reducing agent, while the lance is switched from oxygen to nitrogen, the slag is stirred with nitrogen about 20-60 ″, and then the remainder of Al is added₂O₃Stirring the slag with nitrogen for 2-5 min to control the slag component to R of 2.5-3.5, preferably 3.0, and Al as the second reducing agent₂O₃The content is 18-26%, the MgO content is 5-8%, the FeO + MnO content is less than 3.0%, and the P2O5 content is less than 0.5%. Tapping steel with slag, then deslagging, water quenching, magnetic separation and iron removal to obtain the medium-high steelSynthetic refining slag of alkalinity.

Detailed description of the invention

Adding molten iron, scrap steel, lime, light-burned dolomite and other raw materials into the electric arc furnace, and carrying out slag burden smelting according to the slag alkalinity of 2.5-3.5 and the MgO content of 5% -8%. Before the oxidation period is finished, the slag flows or does not flow, and Al is added into the furnace in one step or in steps before the blowing initial stage or the oxidation period is finished₂O₃Material, slag Al before blowing out₂O₃The content is adjusted to 9 to 16 percent. After the oxidation period is over, part of the Al is added into the furnace₂O₃The material and the first reducing agent or the second reducing agent, and at the same time, the oxygen lance is switched from oxygen to nitrogen or directly by a gas lance, slag is stirred by nitrogen or gas for about 20-60 ″, and then the rest Al is added₂O₃The material and the second reducing agent are continuously stirred with nitrogen or coal gas for 2 to 5 minutes, and the slag component is controlled to be R2.5 to 3.5, Al₂O₃18-26 percent of MgO, 5-8 percent of (FeO + MnO) < 3.0 percent and P2O5 < 0.5 percent. Tapping steel with slag, then deslagging, water quenching, and magnetic separation and iron removal to obtain the medium-high alkalinity synthetic refining slag.

In the technical scheme of the invention, Al is added step by step₂O₃The material is gradually reduced to replace lost FeO, and the reducing agent and the gas are stirred to gradually reduce and gasify P2O5 so as to reduce the gradual stickiness of the slag while the slag Al is reduced₂O₃The problem of rephosphorization possibly caused by the reduction of 2CaOSiO2 phase with increased content is solved, and the slag temperature is increased by utilizing the heat release of the reduction reaction to ensure that the slag fluidity is always in a good state in the whole process of reduction tempering until FeO and P2O5 are reduced and disappeared.

Therefore, the technical scheme of the application realizes that FeO in the slag is reduced to the maximum extent and P2O5 is gasified in the steelmaking process, solves the technical problem that the FeO content is reduced and the rephosphorization problem is contradictory in the prior steel slag, and utilizes the prior equipment and the prior conditions to temper the steel slag into the refining slag by one-step tempering in the steelmaking process, thereby greatly reducing the processing cost of the refining slag. Meanwhile, during tapping, the steel slag after quenching and tempering can be used for realizing molten steel refining, S and O are removed, the steel slag is in place in one step, and a plurality of steel types can cancel the ladle refining process after the furnace; because the FeO content in the steel slag is reduced, slag stopping is not needed during steel tapping, and phosphorus is not returned, so that the working procedure and the cost are saved.

Aiming at the specific embodiment of the first scheme:

example 1

50 tons of converter and 8.3 tons of scrap steel with 48.2 tons of molten iron loading. And carrying out double-slag remaining operation of the converter. Adding scrap steel to mix molten iron, blowing the molten iron by a lance, adding 300 kg of refining slag, blowing 5 '30' later dephosphorizing slag with the components of FeO 14.3%, CaO 38.79%, SiO227.6%, MgO 4.97%, P2O 53%, Al2O 36.2%, MnO 3.1%, R1.4 and slag temperature 1330 ℃. 600 kg of SiC particles are added from a high-level bunker. Meanwhile, the oxygen lance is switched to nitrogen, the slag 3' is stirred by the nitrogen, slag is discharged after blowing is stopped, the temperature of the discharged slag is 1520 ℃, water quenching is carried out, and after the metallic iron is removed by magnetic separation, the low-alkalinity synthetic refining slag is obtained: r1.2, CaO 45.5%, SiO237.6%, MgO 6.3%, Al₂O₃8.2％，P2O5 0.2％，(FeO+MnO)1.9％。

In this example, 300 kg of refining slag was added after the converter was opened, and Al in the initial slag component₂O₃The refining content reaches 6.2%, and a better phosphorus absorption effect is still achieved under the condition of alkalinity of 1.4: P2O53.5 percent. This is because the slag temperature control is low (below 1330 ℃) and the equilibrium coefficient of phosphorus is so high that less 2CaOSiO2 phase in the slag has sufficient capacity to absorb phosphorus. Although the slag temperature is low, Al in the slag₂O₃The 6.2% content makes the slag viscosity low at this temperature, and makes less 2CaOSiO2 in the slag be exerted more effectively.

Example 2

50 tons of converter and 8.3 tons of scrap steel with 47.7 tons of molten iron loading. Adopts double-slag residue remaining operation. Alkaline slag such as lime is not added from the initial stage of blowing to the initial stage of slag pouring. Adding molten iron and scrap steel, blowing to 3 '30' desiliconized slag containing 14.7% FeO, 35.2% CaO, 236.3% SiOx, 5.5% MgO, P2O52.2% Al₂O₃3.5%, MnO 3.01%, R0.96. 50 kg of coke particles are added from an overhead bunker while the blowing is stopped, the slag is stirred by nitrogen for 50 ", then 300 kg of aluminum ash balls are added to continue stirring the slag for 3' 30 ″, and the blowing is stopped and the slag is dischargedAnd the slag temperature is 1525 ℃, water quenching is carried out, and the low-alkalinity synthetic refining slag is obtained after the metallic iron is removed through magnetic separation: r1, CaO 36.1%, SiO236.7%, MgO 6.3%, Al₂O₃8.1％，P2O5 0.4％，(FeO+MnO)1.5％。

In the embodiment, 50 kg of coke particles are added after the initial blowing of the converter is finished, so that the FeO content of the slag is reduced by about 30 percent, the phosphorus is not returned, the subsequent aluminum ash consumption can be reduced, and the cost is saved. The aluminum ash contains 38 percent of Al and Al₂O₃45 percent. Adding 50' of coke particles, adding aluminum ash, continuing stirring the slag with nitrogen to reduce and gasify P2O5, and reducing and completely discharging FeO and MnO.

Example 3

50 tons of converter and 47.3 tons of molten iron loading 7.9 tons of scrap steel. Adopts double-slag residue remaining operation. Adding molten iron, adding scrap steel, blowing, and adding 500 kg of lime and 300 kg of bauxite in batches. Blowing to 6 '40' dephosphorized slag containing 15.6% FeO, 43.2% CaO, 220.6% SiOx, 6.5% MgO, P2O53.2% Al₂O₃6.2%, MnO 3.0%, R2.1. And (3) stopping blowing, adding 70 kilograms of coke particles from an overhead bunker while stopping blowing, stirring 40 "of slag by using nitrogen, adding 200 kilograms of aluminum ash balls, continuously stirring 3' 30" of slag, stopping blowing, discharging slag, wherein the slag discharging temperature is 1646 ℃, performing water quenching, removing metallic iron through magnetic separation, and obtaining low-alkalinity synthetic refining slag: r2.0, CaO 49.8%, SiO224.1%, MgO 8.5%, Al₂O₃15.3％，P2O5 0.3％，(FeO+MnO)2％。

The technical scheme of the first scheme is a process method for the initial slag of the converter, so that the steps of removing sulfur and oxygen from molten steel in the later period of converter steelmaking are not involved, and the comparison of various data records after converter tapping is not needed.

The specific embodiment of the second scheme is as follows:

example 4

50 tons of converter, 49 tons of molten iron loading, 8.8 tons of scrap steel and 45 steel grades. The slag-remaining single-slag operation mode is adopted, 1.75 tons of lime, 0.45 ton of light-burned dolomite, 0.2 ton of bauxite and 0.4 ton of iron sheet are added in batches after molten iron is added and blown. The first batch was added 1/2 of the total amount and the balance was added over 8 minutes. Blowing to 12' and adding bauxite from an overhead binBlowing was stopped after 0.2 ton. The final slag components are 8.6 percent of FeO, 52.5 percent of CaO, 214.6 percent of SiOx, 5.4 percent of MgO, P2O53.2 percent of Al₂O₃15.3%, MnO 2.80%, R3.6. The end temperature is 1540 ℃. Adding 100 kilograms of SiC granules from an overhead bunker while stopping blowing, stirring 50 ' of slag by nitrogen, adding 400 kilograms of aluminum ash balls, continuously stirring 3 ' 30 ' of slag, stopping blowing, discharging slag at the temperature of 1656 ℃, performing water quenching, and obtaining medium-high alkalinity synthetic refining slag after removing metallic iron through magnetic separation: alkalinity is R3.0, CaO 53.3%, SiO217.2%, MgO 5.6%, Al₂O₃23.1%, P2O50.3%, 1.8% of (FeO + MnO). And tapping without slag blocking and slag carrying. Then pouring out the residual slag to be used as the synthetic refining slag of other furnaces. The content of FeO in slag before and after the slag conditioning treatment of the blowing end point slag and the molten steel [ O ] before and after the slag washing][S]The content changes are shown in Table 1. The total amount of inclusions and the particle size distribution of the inclusions in the billet are shown in Table 2.

Example 5

50 tons of converter and 8 tons of scrap steel with 48 tons of molten iron. Steel grade 45 steel. And adopting a slag remaining single slag operation mode. Adding waste steel, adding molten iron, blowing, and adding 2 tons of lime, 0.5 ton of light-burned dolomite, 0.35 ton of ore and 0.35 ton of sheet iron into the converter in three batches within 4.5 minutes. 1/2 for the first batch, 1/3 for the second batch, and the balance added over 8 minutes. Blowing to 11 ' 20 ' 0.4 ton of bauxite is added into the converter, and blowing is continued for 40 '. The blowing end slag comprises 10.5 percent of FeO, 50.6 percent of CaO, 216.8 percent of SiOx, 5.3 percent of MgO, P2O53.4 percent of Al₂O₃13.2%, MnO 2.87%, R3.0. The end temperature is 1550 ℃. And (3) stopping blowing, adding 40 kg of coke particles from a high-level bunker, stirring 40 ' of the slag by using nitrogen at the same time, adding 600 kg of aluminum ash balls, continuously stirring 4 ', 20 ' of the slag, stopping blowing, discharging the slag, keeping the slag temperature at 1653 ℃, performing water quenching, and performing magnetic separation to obtain medium-high alkalinity synthetic refining slag: alkalinity is R3.0, CaO 52.1%, SiO217.3%, MgO 5.2%, Al₂O₃24.5%, P2O50.3%, 2.1% of (FeO + MnO). And tapping without slag blocking and slag carrying. Then pouring out the residual slag to be used as the synthetic refining slag of other furnaces.

The content of FeO in the slag before and after the quenching and tempering treatment of the slag at the blowing end point and the content change of [ O ] [ S ] in the molten steel before and after the slag washing are shown in Table 1. The total amount of inclusions and the particle size distribution of the inclusions in the billet are shown in Table 2.

Example 6

50 tons of converter, 49 tons of scrap steel and 28 tons of molten iron are charged. Steel grade 45 steel. And adopting a slag remaining single slag operation mode. Adding waste steel, adding molten iron, blowing, and adding 2.2 tons of lime, 0.5 ton of light-burned dolomite, 0.35 ton of ore and 0.35 ton of sheet iron into the converter in three batches within 4.5 minutes. 1/2 for the first batch, 1/3 for the second batch, and the balance added over 8 minutes. Blowing to 11' 10 ", adding 0.5 ton of bauxite into the converter, continuing blowing for 50", and then stopping blowing. The blowing end slag comprises 8.9 percent of FeO, 56.6 percent of CaO, 217.2 percent of SiOx, 5.1 percent of MgO, P2O53.6 percent of Al₂O₃14.3%, MnO 2.13%, R3.3. The end temperature is 1530 ℃. And (3) after blowing is stopped, adding 0.2 ton of SiC granules and 0.3 ton of aluminum ash balls into an overhead bunker, stirring 5 '30' by using nitrogen, stopping blowing, discharging residues, wherein the temperature of the discharged residues is 1641 ℃, performing water quenching, and performing magnetic separation to obtain medium-high alkalinity synthetic refining slag: alkalinity of R3.0, CaO 52.8%, SiO217.6%, MgO 4.9%, Al₂O₃24.2%, P2O50.35%, 1.9% of (FeO + MnO). And tapping without slag blocking and slag carrying. Then pouring out the residual slag to be used as the synthetic refining slag of other furnaces.

The specific embodiment for scheme three:

example 7

110 ton ultra high power arc furnace. 105 tons of iron and steel materials, and 42 tons of molten iron. The ingredients are controlled according to about 3.0 slag alkali and 6 percent of MgO, 2 tons of lime and 0.4 ton of light-burned dolomite. Charging, melting and oxidizing, blowing till no slag flows before oxidation is finished, adding 0.4 ton of bauxite, continuing blowing for 60', stopping blowing, then adding 0.2 ton of bauxite and 60 kilograms of carbon powder, stirring for 1 minute by using nitrogen, then adding 0.3 ton of bauxite and 0.3 ton of SiC particles, and stirring slag for 5 minutes by using nitrogen. Slag R3.0, CaO 52.8%, SiO217.6%, MgO 4.9%, Al are obtained₂O₃24.2％，P2O5 0.15％，(FeO + MnO) 2.5%. Tapping steel with slag, and then obtaining synthetic refining slag of the refining process after water quenching, crushing and magnetic separation of the discharged slag.

Example 8

110 ton ultra high power arc furnace. 106 tons of steel materials, and 46 tons of molten iron. The ingredients are controlled according to about 3.0 slag alkali and 6 percent of MgO, 2.2 tons of lime and 0.54 ton of light-burned dolomite. Charging, melting and oxidizing, blowing till a small part of slag flows before the oxidation is finished, adding 0.45 ton of bauxite, continuing to blow for 1 minute, stopping blowing, then adding 0.3 ton of bauxite and 50 kg of carbon powder, stirring for 1 minute by using nitrogen, then adding 0.3 ton of bauxite and 0.3 ton of silicon mud particles, and continuing to stir the slag for 3 minutes by using nitrogen. Obtaining the smelting slag R3.0, CaO 51.2 percent, SiO216.8 percent, MgO 5.3 percent and Al₂O₃25.2%, P2O50.38%, 2.1% of (FeO + MnO). And tapping with slag. Then pouring out the slag, and carrying out water quenching, crushing and magnetic separation to obtain the synthetic refining slag.

The contents of FeO and molten steel [ P ] in the slag before and after the thermal refining of the slag at the blowing end point and the change of the contents of molten steel [ O ] [ S ] before and after the slag washing are shown in Table 1. The total amount of inclusions and the particle size distribution of the inclusions in the billet are shown in Table 2.

TABLE 1 change in FeO and P contents in slag before and after the conditioning of the slag at the blowing end point and O S contents in molten steel before and after the slag washing

TABLE 2 Total amount of inclusions and particle size distribution of inclusions in billet

As can be seen from Table 1, in examples 4 to 8, the reduction of the content of (FeO) in the slag before/after the final-point slag quenching and tempering was reduced by 85 to 90%, and the content of [ P ] in the molten steel was not changed; the [ O ] in the molten steel is reduced by about 65 percent, and the [ O ] in the molten steel is further reduced by about 70 percent after slag washing to 10-35 ppm; the S removal rate of the molten steel after slag washing reaches 50-71%, and the molten steel [ S ] after slag washing is reduced to 0.0075-0.0137%.

Table 2 shows that the total amount of inclusions in the steel billet is reduced by about 50% from 10(mg.10kg-1) to 5(mg.10kg-1) in the slag washing and the non-slag washing of the embodiment; and the grain size of the inclusions is finer.

In conclusion, by the technical scheme, the steel slag is modified in the steel making process, so that the steel slag can be prepared into the refining slag, the FeO content of the end-point slag and the oxygen content in molten steel can be greatly reduced, the yield of the molten steel is improved, and the total amount of inclusions in steel billets can be reduced. Meanwhile, the steel can be tapped with slag, molten steel is further deoxidized and desulfurized, and the quality of the molten steel is improved. The process can reduce the steel-making process, reduce various costs, achieve multiple purposes, and have very strong practical value and economic value.

The technical solutions and the implementation effects of the present invention are further described by the embodiments, but the scope of the present invention is not limited thereto. Any improvements, modifications, substitutions, combinations, and simplifications made based on the principle and spirit of the invention should be construed as equivalents and are included in the scope of the claims of the present invention.

Claims

1. A deoxidation and desulfurization process for tempering steel slag into refining slag and molten steel is characterized in that raw materials including molten iron, scrap steel, lime and light-burned dolomite are added into a steel furnace, and slagging and blowing are carried out according to the alkalinity of the slag of 2.5-3.5 and the MgO content of 5-8%, and the process comprises the following steps:

adding Al-containing material to a steel-making furnace in batches₂O₃The method comprises the following steps of adding a reducing agent into the materials and the reducing agent, stirring slag by using nitrogen, and controlling the components of the end-point slag of the steel-making furnace to be as follows after the nitrogen stirring is finished: r2.5-3.5, Al₂O₃18-26 percent of MgO, 5-8 percent of (FeO + MnO))＜3.0％、P2O5＜0.5％；

And tapping with slag.

2. The process for refining and refining steel slag into refining slag and deoxidizing and desulfurizing molten steel as claimed in claim 1, wherein Al is added to the converter₂O₃The specific steps of the materials and reducing agent are as follows:

after blowing is stopped, part of Al is added into the furnace₂O₃The material and the first reducing agent or the second reducing agent, and simultaneously, the oxygen lance is switched from oxygen to nitrogen, and slag is stirred by the nitrogen for about 20-60';

then adding the rest Al₂O₃Continuously stirring the slag for 1-4 min by using nitrogen, controlling the alkalinity of the slag to be R2.5-3.5, and controlling the slag to be Al₂O₃18％-26％，MgO 5％-8％，(FeO+MnO)＜3.0％，P2O5＜0.5％。

3. The process for refining and refining steel slag and deoxidizing and desulfurizing molten steel as claimed in claim 1, wherein Al is added to the inside of the electric arc furnace₂O₃The specific steps of the materials and reducing agent are as follows:

then adding the rest Al₂O₃Continuously stirring the slag with nitrogen or coal gas for 1-4 min to control the slag componentsIn R2.5-3.5, Al₂O₃18-26％，MgO 5-8％，(FeO+MnO)＜3.0％，P2O5＜0.5％。

4. The process for refining and refining steel slag into refining slag and deoxidizing and desulfurizing molten steel as set forth in any one of claims 1 to 3, wherein the Al content₂O₃The material is one of bauxite, refining slag or metal calcium slag.

5. The process for refining steel slag into refining slag and deoxidizing and desulfurizing molten steel as claimed in claim 1, wherein the amount of said reducing agent added is 2-8 kg/ton of steel, and contains Al₂O₃The material addition amount is 8-20 kg per ton steel.

6. The process for refining steel slag into refining slag and deoxidizing and desulfurizing molten steel according to claim 4, wherein the reducing agent is divided into a first reducing agent and a second reducing agent, and the first reducing agent is one of coal particles, coke particles, graphite and other carbonaceous materials; the second reducing agent is one or two of silicon mud, aluminum iron, aluminum particles, aluminum ash, calcium carbide, silicon carbide and CaSi;

7. The process for refining steel slag into refining slag and deoxidizing and desulfurizing molten steel as claimed in any one of claims 1 to 3, wherein the nitrogen gas can be replaced by coal gas.

8. A process for tempering steel slag into refining slag, adding raw materials including molten iron, waste steel, light-burned dolomite and lime into a converter, and blowing according to slag making with the alkalinity of 1.3-2.2 and MgO 5-8%, and is characterized in that:

by batchwise addition of Al-containing substances to the steel-making furnace₂O₃Adding a reducing agent and stirring slag by nitrogen gas;

controlling the components of the initial slag of the converter as follows: r0.8-2.0, Al₂O₃8-16％、MgO 5-8％、(FeO+MnO)＜3.0％、P2O5＜0.5％。

9. The process for refining and tempering steel slag into steel slag according to claim 7, wherein Al is added to the steel-making furnace in batches₂O₃The steps of material and reducing agent include:

and (4) discharging initial slag, water quenching and magnetic separation.

10. The process for refining steel slag into refined slag according to claim 7 or 8, wherein said Al-containing slag₂O₃The material is one of bauxite, refining slag or metal calcium slag; the reducing agent is divided into a first reducing agent and a second reducing agent, wherein the first reducing agent is coal particles, coke particles, graphite and other carbonaceous materials; the second reducing agent is one or two of silicon mud, aluminum iron, aluminum particles, aluminum ash, calcium carbide, silicon carbide and CaSi.

11. The process for refining steel slag according to claim 9, wherein the first reducing agent C is added in an amount of 0 to 2 kg/ton of steel, and the second reducing agent C is added in an amount of 2 to 8 kg/ton of steel; the Al-containing component₂O₃The material addition amount is 8-20 kg per ton steel.