A refining light treatment process based on tapping process metallurgy

Abstract

The application discloses a refining light treatment process based on tapping process metallurgy, which comprises the following steps: hot metal desulfurization pretreatment, converter smelting, converter tapping metallurgy and refining light treatment; the converter tapping metallurgy step comprises the following steps: adding refining slag or furnace slag modifier along with the steel flow during tapping; the material adding sequence of SiMn deoxidized steel in the tapping process is as follows: pre-melted slag material, lime, silicon manganese, aluminum block and alloy; the material adding sequence of Al deoxidized steel in the tapping process is as follows: aluminum block, pre-melted slag material, lime, silicon manganese and alloy; the pre-melted slag material is added when 1 / 5-2 / 5 of the steel is tapped, and the adding amount is 2.0-5.0 kg / t·steel; the lime is added after the pre-melted slag material, and the adding amount is 1.5-5.0 kg / t·steel; after the steel is tapped, the top slag modifier is added on the slag surface, and the adding amount is 0.5-3.0 kg / t·steel. The LF / RH furnace treatment time of the process is controlled to be less than 20 minutes, so that the molten steel refining time is greatly shortened, the material consumption, temperature loss and refractory loss are reduced, and meanwhile, the molten steel quality and cleanliness and the castability of the continuous casting molten steel are ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of molten steel refining process in the metallurgical industry, and particularly relates to a refining light treatment process based on metallurgy in the tapping process. BACKGROUND

[0002] Steel refining treatment is a key process for producing high-quality steel. LF / RH furnace, as the most commonly used secondary refining equipment in the steelmaking process, is widely used in various steel plants. However, there are some problems in the LF / RH furnace treatment process, such as long treatment time, high power consumption, large consumption of auxiliary raw materials and refractory materials, high cost, unstable rhythm control, difficulty in matching with efficient continuous casting, easy absorption of oxygen and nitrogen in molten steel during the treatment process, and many inclusions, which increase the production cost and make the quality unstable, and reduce the economic benefits of steel manufacturers.

[0003] With the over-supply of the steel market, reducing production cost and improving quality are the urgent needs of each steel company. However, the increasingly stringent quality and cost requirements of steel grades have contradicted the LF / RH furnace treatment. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a refining light treatment process based on metallurgy in the tapping process, which can effectively reduce the refining treatment load of the LF / RH furnace.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows: it includes hot metal desulfurization pretreatment, converter smelting, converter tapping metallurgy and refining light treatment steps.

[0006] The converter tapping metallurgy step: adding refining slag or slag modification along with the steel flow during tapping; the material addition sequence of SiMn deoxidized steel during the tapping process is: pre-melted slag material→lime→silicon manganese→aluminum block→alloy, and the material addition sequence of Al deoxidized steel during the tapping process is: aluminum block→pre-melted slag material→lime→silicon manganese→alloy; the pre-melted slag material is added when 1 / 5 to 2 / 5 of the steel is tapped, and the addition amount is 2.0 to 5.0 kg / t·steel; lime is added after the pre-melted slag material, and the addition amount is 1.5 to 5.0 kg / t·steel; top slag modifier is added on the slag surface after the steel is tapped, and the addition amount is 0.5 to 3.0 kg / t·steel;

[0007] The refining light treatment step: LF light treatment or RH light treatment is adopted; the LF light treatment is one-time aluminum deoxidation, the oxygen [O] in the steel before adding aluminum is controlled to be 40 to 100 ppm, the molten steel is soft blown for 8 minutes or more after adding aluminum, and the LF light treatment time is 15 to 20 minutes; the RH light treatment, the initial carbon / oxygen ratio [C] / [O] of the RH station is 0.75 to 1.35, the oxygen content [O] of the molten steel before RH final deoxidation is ≤150 ppm, and the RH light treatment time is 15 to 20 minutes.

[0008] Further, the converter tapping metallurgical step controls the CaO / Al2O3 ratio in the ladle slag to be 1.6-2.0 before the refining light treatment step.

[0009] Further, the LF light treatment is controlled in stages in terms of stirring intensity of the ladle bottom argon blowing: 30-50 W / t in the heating stage, 300-500 W / t in the desulfurization stage, 100-200 W / t in the alloying stage, and 30-50 W / t in the soft blowing stage.

[0010] Further, the converter tapping metallurgical step requires that the molten steel be deoxidized to form white slag as soon as possible, the white slag basicity R=1.5-2.0, and the FeO%+MnO% in the white slag≤1wt%.

[0011] Further, the molten iron desulfurization pretreatment step desulfurizes the molten iron to be fed into the converter to a sulfur content≤the target sulfur content of the steel grade.

[0012] The beneficial effects produced by the above technical solution are as follows: the present application makes full use of the good thermodynamic and kinetic conditions in the converter tapping process, optimizes the tapping process metallurgy and operation, advances the molten steel refining process to the tapping process, modifies the slag at tapping, realizes the deoxidation and precise alloying of the molten steel or simultaneously adds refining slag with the steel flow, advances the slagging and deoxidation in the LF / RH furnace, and realizes the LF / RH furnace light treatment; the LF / RH furnace treatment time is controlled to be within 20 minutes, greatly shortening the molten steel refining time (the LF / RH furnace treatment molten steel refining time is generally 40-60 minutes), reducing material consumption, temperature loss, and refractory loss, while ensuring the molten steel quality and cleanliness and the castability of the continuous casting molten steel; the present application shortens the refining time, reduces the consumption of deoxidizers, ferroalloys, and refractories, reduces the inclusions in the steel, improves the molten steel quality, improves the comprehensive economic benefits, and, after repeated field tests and long-term mass production, reduces the cost per ton of steel by more than 30 yuan under the premise of not affecting the quality of the cast slab, becoming an important means for low-cost production of high-quality steel grades; it has important significance and broad application prospects for promoting the further simplification of the process in the steel industry and realizing high-efficiency, low-cost, low-pollution, and high-quality steel production. DETAILED DESCRIPTION

[0013] The present application will be further described in detail below in combination with specific embodiments.

[0014] The present application is based on the refining light treatment process of the tapping process metallurgy, which includes molten iron desulfurization pretreatment, converter smelting, converter tapping metallurgy, and refining light treatment steps, and is suitable for all converter smelting steel grades, and the process of each step is described as follows.

[0015] 1) Hot metal desulphurization pretreatment: In order to reduce the desulphurization load of converter and LF / RH furnace, hot metal desulphurization pretreatment process is adopted, and the desulphurization is carried out to the sulfur content of the converter molten iron ≤ the target sulfur content of the steel grade; in the subsequent refining light treatment step, the desulphurization amount of the molten steel in the LF light treatment process is ≤ 60 ppm, and the molten steel is not desulphurized in the RH light treatment process.

[0016] 2) Converter smelting: the oxygen content [O] of the converter tapping molten steel is 100-500 ppm, the tapping temperature is 1640-1680 ℃, and the converter tapping slag amount is ≤ 2 kg / t.

[0017] 3) Converter tapping metallurgy: the converter tapping metallurgy process is in accordance with the process principle that the molten steel refining starts as soon as the tapping starts, and fully utilizes the good thermodynamic and kinetic conditions in the converter tapping process to advance the molten steel refining process to the molten steel tapping process, and the refining slag or slag modification is added with the steel flow at the time of tapping to realize the advancement of LF / RH furnace slagging and deoxidization.

[0018] Due to the different characteristics and quality requirements of different steel grades, the refining processes adopted are also different. Therefore, corresponding tapping process metallurgy processes are developed according to the characteristics and quality requirements of different steel grades.

[0019] (1) The material addition sequence of SiMn deoxidized steel in the tapping process is: pre-melted slag material → lime → silicon manganese → aluminum block → alloy → top slag modifier. The material addition sequence of Al deoxidized steel in the tapping process is: aluminum block → pre-melted slag material → lime → silicon manganese → alloy → top slag modifier.

[0020] (2) Tapping ladle slag modification to realize the advancement of LF / RH furnace slagging and deoxidization: tapping ladle slag modification refers to adding aluminum-containing pre-melted slag material into the ladle during the converter tapping process to quickly form slag, so as to reduce the TFe in the ladle slag, so that the effect of the ladle slag can be achieved in the secondary refining to inhibit the secondary oxidation of the molten steel and reduce the oxygen content in the molten steel, thereby effectively preventing the defects caused by Al2O3 inclusions in the rolling process.

[0021] The addition amount of the above pre-melted slag material, lime and top slag modifier needs to be adjusted according to the converter tapping slag amount, the ΣFeO content of the final slag and the target oxygen content of the molten steel: the pre-melted slag material is added when the tapping is 1 / 5-2 / 5, and the amount is 2.0-5.0 kg / t·steel; the lime is added after the pre-melted slag material, and the addition amount is 1.5-5.0 kg / t·steel; the top slag modifier is added on the slag surface after the tapping is completed, and the addition amount is 0.5-3.0 kg / t·steel.

[0022] High fluidity of slag: The CaO / Al2O3 ratio of the ladle slag should be maintained at 1.6-2.0 before the light refining and at 1.2-1.6 after the light refining, so as to ensure the low viscosity, low melting point and high adsorption capacity of Al2O3 of the slag during the light refining.

[0023] Weak oxidizability of slag: Before the light refining, the TFe in the ladle slag should be ≤6wt% for the ultra-low carbon steel with C%≤0.01wt%, and should be ≤3wt% for the medium-low carbon steel with 0.01wt%<C%≤0.3wt%, so as to reduce the oxygen content in the molten steel.

[0024] 4) Light refining: LF light refining or RH light refining is adopted.

[0025] (1) LF light refining: One-time aluminum deoxidation is adopted, the oxygen content in the steel before the aluminum addition is controlled at 40-100ppm, and the soft blowing of the molten steel is controlled at 8min or more after the aluminum addition, so as to ensure the cleanliness of the molten steel and to solve the problems of no slagging, no desulfurization and no calcium treatment during the LF refining.

[0026] The stirring intensity of the ladle bottom argon blowing is controlled in stages: 30-50W / t in the heating stage, 300-500W / t in the desulfurization stage, 100-200W / t in the alloying stage and 30-50W / t in the soft blowing stage.

[0027] The LF light refining time is 15-20min.

[0028] (2) RH light refining: The initial carbon / oxygen ratio [C] / [O] is 0.75-1.35 when the RH is entered. The principle is that the main decarburization reaction is C+O=CO, and the [C] / [O] is 12 / 16=0.75. Since the oxygen in the steel comes from the molten steel, the slag, the refractory and the oxygen in the inhaled air, the highest natural decarburization efficiency is obtained when the [C] / [O] is 0.75-1.35 according to our production practice, which corrects the technical bias of the fixed value of [C] / [O]=0.75 calculated based on the carbon-oxygen reaction in the traditional theory and is beneficial to improve the decarburization efficiency. The oxygen content in the molten steel before the RH terminal deoxidation is controlled at ≤150ppm, which is beneficial to improve the cleanliness of the molten steel. The RH light refining time is 15-20min.

[0029] (3) During the LF light refining or the RH light refining, the deoxidized slag is required to be formed as soon as possible. The slag sample is taken after the complete melting of the slag after the addition of the slag material, and the color and properties are observed after slight cooling, so as to judge the deoxidation and composition of the slag, which is beneficial to quickly adjust the composition of the slag and maintain the white slag operation.

[0030] White slag basicity (R) standard: Quaternary basicity R = (CaO% + MgO%) / (SiO2% + Al2O3%) = 1.5~2.0; White slag oxidizability standard: (FeO% + MnO%) ≤ 1wt%; White slag color and property judgment standard: The slag color is white or slightly yellow, and the slag is smooth and easy to break after being taken out and cooled, which is the ideal slag condition.

[0031] Example 1: The refining light treatment process based on the tapping process metallurgy adopts the following specific process.

[0032] A certain full-process steel plant produces 380CL wheel steel of Al-deoxidized medium and low carbon steel grade by 1650 continuous casting machine + 2050 hot rolling.

[0033] 1) Hot metal desulfurization pretreatment: desulfurization to the sulfur content of 0.0012% in the converter tapping molten iron, and the target sulfur content of the steel grade is ≤0.006%.

[0034] 2) Converter smelting: the oxygen content [O] in the converter tapping molten steel is 300ppm, the tapping temperature is 1640~1660℃, and the converter tapping slag amount is 2kg / t.

[0035] 3) Converter tapping metallurgy: aluminum deoxidization is adopted in the tapping process, tapping starts→aluminum block is added→tapping to 1 / 5 and pre-melted slag is added, then lime is added→tapping to 1 / 3 and silicon manganese is added→tapping to 2 / 3 and other alloys are added→tapping ends and top slag modifier is added. The converter tapping alloy is added according to the finished product composition requirements of the steel grade: pre-melted slag 4.0kg / t·steel, lime is added to the converter tapping slag, the addition amount is 4.5 kg / t steel; the top slag modifier is added on the slag surface after tapping, the addition amount is 2.0kg / t·steel; the CaO / Al2O3 ratio of the ladle slag is maintained at 1.8 before refining light treatment, and TFe of the ladle slag is 3wt%.

[0036] 4) Refining light treatment: LF light treatment is adopted; one-time aluminum deoxidization is adopted, the oxygen content in the steel before adding aluminum is controlled to be 40ppm, and the molten steel is soft blown for 10min after adding aluminum; the stirring intensity of the ladle bottom argon blowing is controlled in stages: 40W / t in the heating stage, 400W / t in the desulfurization stage, 100W / t in the alloying stage, and 50W / t in the soft blowing stage; the white slag quaternary basicity R is 1.5~1.7, and the white slag oxidizability (FeO% + MnO%) is 0.9wt%. The LF light treatment time is 18 minutes; the CaO / Al2O3 ratio of the ladle slag after refining light treatment is 1.5.

[0037] 5) Technical effect: traditional converter smelting + LF process, LF furnace adds aluminum deoxidation, slag making, stirring desulfurization and calcium treatment, the treatment cycle is generally about 70 min. The above LF light treatment process of the embodiment does not make slag, does not desulfurize, and does not calcium treatment, and the treatment cycle is 18 min, which significantly shortens the LF refining time and saves the cost. Under the traditional LF process, the sulfur content of the molten iron and the terminal point of the molten steel in the converter is 0.0243% and 0.0213% respectively, and after the LF desulfurization, the sulfur content in the molten steel is 0.0046%. The molten iron desulfurization pretreatment of the embodiment can control the sulfur content of the molten iron to be less than or equal to 0.0015%, and after the LF light treatment, the sulfur content in the molten steel is 0.0033%. The sulfur content of the molten steel in the LF outlet and the tundish under the light treatment process of the embodiment is lower, which fully meets the quality requirements.

[0038] The LF light treatment process of the embodiment does not make slag, does not desulfurize, and does not calcium treatment, which reduces the generation of steel slag reaction and inclusions. The intermediate package total oxygen content under the LF light treatment process of the embodiment is 5 ppm lower than that under the traditional process; the LF light treatment process does not make slag, has less power transmission, and has a short treatment time, which can effectively control the nitrogen increase of the molten steel, and is 10 ppm lower than the traditional process. It can be seen that the LF light treatment process of the method is obviously superior to the traditional process in the control of oxygen and nitrogen content.

[0039] Comparing the inclusion rating results of the 380CL material sample under the method and the traditional process: the inclusion rating of the D class of the material sample under the LF light treatment process of the embodiment is 1.0, and the inclusion rating of the Ds class is 0.5, which is better than the inclusion rating of the B class, the inclusion rating of the D class and the inclusion rating of the DS class under the traditional LF process, which are 0.5, 1.0 and 0.5 respectively. The reason is that the step-by-step deoxidization and the use of silicon, manganese and carbon for pre-deoxidization after the furnace are beneficial to reduce the size and number of inclusions.

[0040] Embodiment 2: The refining light treatment process based on the metallurgy of the tapping process adopts the following specific process.

[0041] A full-process steel plant 1650 continuous casting machine + 2050 hot rolling produces plate hot coil SPHE-Ti3, which belongs to an Al deoxidized ultra-low carbon steel grade.

[0042] 1) Molten iron desulfurization pretreatment: desulfurization to 0.002% of the sulfur content of the molten iron in the converter, and the target sulfur content of the steel grade is less than or equal to 0.010%.

[0043] 2) Converter smelting: the oxygen content [O] of the molten steel in the converter tapping is 400 ppm, the tapping temperature is 1660-1680℃, and the slag amount of the converter tapping is 1.8 kg / t.

[0044] 3) Converter tapping metallurgy: tapping process using aluminum deoxidation. Deoxidizing aluminum ingot is added at the beginning of tapping, the amount is 1.4 kg / t steel; pre-melted slag material is added at 2 / 5 of the tapping, the amount is 5.0 kg / t steel; lime is added with synthetic slag after 2 / 5 of the tapping, the amount is 5.0 kg / t steel. Silicon-manganese alloy is added at 3 / 5 of the tapping. The top slag modifier is added on the slag surface after the tapping, the amount is 3.0 kg / t steel. The CaO / Al2O3 ratio of the ladle slag is maintained at 1.8-2.0 before the refining light treatment, and the TFe in the ladle slag is 6wt%.

[0045] 4) Refining light treatment: RH light treatment is used. The initial carbon / oxygen ratio [C] / [O] is 1.35 at the RH inlet, and the oxygen content [O] of the molten steel before the RH final deoxidation is 120 ppm. The RH light treatment time is 18 minutes. The white slag four-element basicity R is 1.5-1.7, and the white slag oxidizability (FeO%+MnO%) is 0.5wt%. The CaO / Al2O3 ratio of the ladle slag after the refining light treatment is 1.6.

[0046] 5) Technical effect: The traditional process flow is: hot metal desulfurization and slagging pretreatment → combined blown converter smelting → LF refining → RH refining → slab continuous casting. Due to the influence of the ladle slag modification process and the large amount of argon stirring, the average total oxygen content in the molten steel after the LF refining is 42 ppm; after the RH treatment, the average total oxygen content in the molten steel is 20 ppm. The cleanliness of the molten steel using the method is greatly improved compared with the traditional double process. After using the method, the LF slag modification, slagging, and molten steel heating operations are reduced, the refractory, power, and alloy costs are saved, and the comprehensive cost is greatly reduced. More importantly, in the case of high production capacity, the tension between the converter and the refining is relieved, and the LF refining process is more stable and smooth.

[0047] Example 3: The refining light treatment process based on the tapping process metallurgy uses the following specific process.

[0048] A certain full-process steel plant 1650 continuous casting machine + 2050 hot rolling produces hot coil structural steel Q235B, which belongs to SiMn deoxidized medium and low carbon steel.

[0049] 1) Hot metal desulfurization pretreatment: desulfurization to 0.005% of the sulfur content of the hot metal into the converter, and the target sulfur content of the steel grade is ≤0.015%.

[0050] 2) Converter smelting: the oxygen content [O] in the converter tapping molten steel is 200 ppm, the tapping temperature is 1640-1660℃, and the converter tapping slag amount is 1.6 kg / t.

[0051] 3) Converter tapping metallurgy: Q235B tapping process using SiMn deoxidation, tapping to 1 / 5 plus pre-melted slag material, then adding lime→ tapping to 1 / 3 plus silicon manganese→ tapping to 2 / 3 plus aluminum block→ tapping to 4 / 5 plus other alloy→ end of tapping plus top slag modifier. Converter tapping alloy is added according to the composition requirements of the finished product: pre-melted slag material 2.0 kg / t·steel, converter tapping slag material is added lime, the amount is 1.5 kg / t steel; top slag modifier is added on the slag surface after tapping, the amount is 0.5 kg / t·steel; the CaO / Al2O3 ratio of the ladle slag is maintained at 1.6-1.8 before refining light treatment, and the TFe of the ladle slag is 2.8wt%.

[0052] 4) Refining light treatment: LF light treatment is used; one-time aluminum deoxidation, control the oxygen [O] in the steel before adding aluminum = 60 ppm, soft blowing of the molten steel for 8 min after adding aluminum; control the stirring intensity of the ladle bottom argon blowing in stages: 30 W / t in the heating stage, 300 W / t in the desulfurization stage, 150 W / t in the alloying stage, and 30 W / t in the soft blowing stage; white slag four-element basicity R = 1.5, white slag oxidizability (FeO% + MnO%) = 1.0wt%. The LF light treatment time is 15 minutes; the CaO / Al2O3 ratio of the ladle slag after refining light treatment is 1.2.

[0053] 5) Technical effect: The traditional converter smelting + LF treatment process, LF furnace aluminum deoxidation, slag making, stirring desulfurization and calcium treatment, the treatment period is generally about 60 min. The above-mentioned LF light treatment process of the embodiment does not make slag, does not desulfurize, and does not calcium treatment, the treatment period is 15 min, which significantly shortens the LF refining time and saves the cost.

[0054] The LF light treatment process of the embodiment does not make slag, does not desulfurize, and does not calcium treatment, which reduces the steel slag reaction and the generation of inclusions. The LF light treatment process of the embodiment has a full oxygen content of the tundish that is 6 ppm lower than that of the traditional intermediate treatment process; the LF light treatment process of the embodiment does not make slag, has less power consumption, and has a short treatment time, which can effectively control the nitrogen increase of the molten steel, and is 15 ppm lower than that of the traditional intermediate treatment process. It can be seen that the LF light treatment process of the method is obviously superior to the traditional intermediate treatment process in the control of oxygen and nitrogen content.

[0055] Comparing the inclusion rating results of Q235B material samples under the method and the traditional process: the LF light treatment process of the embodiment has a B-type inclusion rating of 0.5 and a Ds-type inclusion rating of 1.0, which is better than the B-type inclusion rating of 1.0 and the DS-type inclusion rating of 1.5 of the traditional LF intermediate treatment process; the reason is that the step-by-step deoxidation and the use of silicon, manganese and carbon for pre-deoxidation after the furnace are beneficial to reduce the size and number of inclusions.

[0056] Example 4: The refining light treatment process based on the tapping process metallurgy uses the following specific process.

[0057] A certain full-process steel plant 1650 continuous casting machine + 2050 hot rolling production plate hot coil SPHC, which belongs to Al deoxidized low carbon steel grade.

[0058] 1) Hot metal desulfurization pretreatment: desulfurization to the sulfur content of the converter into the furnace molten iron 0.005%, the target sulfur content of the steel grade is ≤0.012%.

[0059] 2) Converter smelting: the oxygen content of the converter tapping molten steel is [O]=500ppm, the tapping temperature is 1650-1670℃, and the converter tapping slag amount is 1.9kg / t.

[0060] 3) Converter tapping metallurgy: aluminum deoxidation is used in the tapping process. The deoxidizing aluminum ingot is added at the beginning of tapping, the addition amount is 1.4kg / t·steel; the pre-melted slag material is added at 1 / 3 of the tapping, the addition amount is 3.5kg / t·steel; the lime is added with the synthetic slag after 1 / 3 of the tapping, the addition amount is 4.0kg / t·steel. Silicon-manganese alloy is added at 3 / 5 of the tapping. The top slag modifier is added on the slag surface after the tapping, the addition amount is 2.0kg / t·steel. The CaO / Al2O3 ratio of the ladle slag is maintained at 1.6-1.8 before the refining light treatment, and the TFe of the ladle slag is 2.0wt%.

[0061] 4) Refining light treatment: RH light treatment is used. The initial carbon / oxygen ratio [C] / [O] of RH is 0.75; the oxygen content of the molten steel before RH final deoxidation is [O]=150ppm. The RH light treatment time is 15 minutes. The white slag four-element basicity R is 1.5-1.7, and the white slag oxidizability (FeO%+MnO%) is 0.8wt%. The CaO / Al2O3 ratio of the ladle slag after the refining light treatment is 1.4.

[0062] 5) Technical effect: the traditional process flow is: hot metal desulfurization and slagging pretreatment → combined blown converter smelting → LF refining → LF calcium treatment → slab continuous casting. The traditional process is affected by the slag modification process and the large argon amount stirring of production organization, and the average total oxygen content in the molten steel after the LF refining is 48ppm; by using the embodiment, the average total oxygen content in the molten steel after the RH treatment is 22ppm. The cleanliness of the molten steel by using the method is greatly improved compared with the traditional double process. After using the method, the LF slag modification, slagging, molten steel heating and canceling Ca wire feeding operations are reduced, the refractory, power and alloy costs are saved, the comprehensive cost is greatly reduced, and more importantly, in the case of high production capacity, the tension between the converter and the refining is relieved, and the tension of the LF refining process is also relieved, which is more conducive to the stable and smooth operation of the production organization.

[0063] Example 5: The refining light treatment process based on the tapping process metallurgy uses the following specific process.

[0064] A certain full-process steel plant 1650 continuous casting machine + 2050 hot rolling production of hot coil structural steel Q235B, belongs to SiMn deoxidized medium and low carbon steel.

[0065] 1) hot metal desulfurization pretreatment: desulfurization to the sulfur content of the converter into the furnace molten iron 0.008%, steel target sulfur content is ≤0.015%.

[0066] 2) converter smelting: converter tapping molten steel oxygen content [O]=100ppm, tapping temperature 1650~1670℃, converter tapping slag amount 1.8kg / t.

[0067] 3) converter tapping metallurgy: Q235B tapping process using SiMn deoxidation, tapping to 1 / 5 plus pre-melted slag material, then add lime→tapping to 1 / 3 plus silicon manganese→tapping to 2 / 3 plus aluminum block→tapping to 4 / 5 plus other alloy→tapping end plus top slag modifier. Converter tapping alloy according to the steel product composition requirements: pre-melted slag material 3.0kg / t·steel, converter tapping slag material plus lime, the amount of addition is 3.0kg / t steel; top slag modifier is added on the slag surface after tapping, the amount of addition is 1.5kg / t·steel; the CaO / Al2O3 ratio of the ladle slag is maintained at 1.8~2.0 before refining light treatment, and the TFe of the ladle slag is 2.7wt%.

[0068] 4) refining light treatment: LF light treatment is used; one-time aluminum addition for deoxidation, the oxygen content in the steel before aluminum addition is controlled to [O]=100ppm, and the molten steel is soft blown for 12min after aluminum addition; the stirring intensity of the ladle bottom argon blowing is controlled in stages: 50W / t in the heating stage, 500W / t in the desulfurization stage, 200W / t in the alloying stage, and 40W / t in the soft blowing stage; the white slag four-element basicity R=1.5, and the white slag oxidizability (FeO%+MnO%)=1.0wt%. The LF light treatment time is 18 minutes; the CaO / Al2O3 ratio of the ladle slag after the refining light treatment is 1.3.

[0069] 5) technical effect: the traditional converter smelting + LF process, LF furnace aluminum addition for deoxidation, slag making, stirring desulfurization and calcium treatment, the treatment period is generally about 60min; while the above-mentioned LF light treatment process of the embodiment does not make slag, does not desulfurize, and does not calcium treatment, the treatment period is 18min, which significantly shortens the LF refining time and saves the cost. The LF light treatment of the embodiment reduces the steel slag reaction and the generation of inclusions, and the total oxygen content in the tundish is 7ppm lower than that in the traditional process; the nitrogen content in the molten steel can be effectively controlled, which is 14ppm lower than that in the traditional process. The B class inclusion rating of the material sample obtained in the embodiment is 0.5, and the Ds class inclusion rating is 1.0.

[0070] Example 6: the refining light treatment process based on the tapping process metallurgy uses the following specific process.

[0071] A certain full-process steel plant 1650 continuous casting machine + 2050 hot rolling production plate hot coil SPHE-Ti3, belongs to Al deoxidized ultra-low carbon steel grade.

[0072] 1) Hot metal desulfurization pretreatment: desulfurization to the sulfur content of the converter into the furnace molten iron 0.007%, the target sulfur content of the steel grade is ≤0.010%.

[0073] 2) Converter smelting: the oxygen content of the converter tapping molten steel [O]=350ppm, the tapping temperature is 1655-1670℃, and the converter tapping slag amount is 2.0kg / t.

[0074] 3) Converter tapping metallurgy: aluminum deoxidation is used in the tapping process. The deoxidizing aluminum ingot is added at the beginning of tapping, the addition amount is 1.5kg / t·steel; the pre-melted slag material is added at 1 / 3 of the tapping, the addition amount is 2.5kg / t·steel; lime is added with synthetic slag at 1 / 3 of the tapping, the addition amount is 3.5kg / t·steel. Silicon-manganese alloy is added at 3 / 5 of the tapping. The top slag modifier is added on the slag surface after the tapping, the addition amount is 1.0kg / t·steel. The CaO / Al2O3 ratio of the ladle slag is maintained at 1.7-1.9 before refining light treatment, and the TFe of the ladle slag is 5.6wt%.

[0075] 4) Refining light treatment: RH light treatment is used. The initial carbon / oxygen ratio [C] / [O]=1.0 before RH deoxidation, the oxygen content of the molten steel [O]=130ppm. The RH light treatment time is 20 minutes. The white slag four-element basicity R=1.8-2.0, the white slag oxidizability (FeO%+MnO%)=0.7wt%. The CaO / Al2O3 ratio of the ladle slag is 1.4 after refining light treatment.

[0076] 5) Technical effect: by using this embodiment, the average total oxygen content in the molten steel after RH treatment is 20ppm, and the cleanliness of the molten steel is greatly improved compared with the traditional double process.

Claims

1. A refining light treatment process based on tapping process metallurgy, characterized in that: It includes hot metal desulphurization pretreatment, converter smelting, converter tapping metallurgy and refining light treatment steps; The converter tapping metallurgy step: adding refining slag or slag modifier with the steel flow when tapping; the SiMn deoxidized steel is added in the following order during tapping: pre-melted slag material→lime→silicon manganese→aluminum block→alloy, and the Al deoxidized steel is added in the following order: aluminum block→pre-melted slag material→lime→silicon manganese→alloy; the pre-melted slag material is added when 1 / 5-2 / 5 of the steel is tapped, and the addition amount is 2.0-5.0 kg / t·steel; the lime is added after the pre-melted slag material, and the addition amount is 1.5-5.0 kg / t·steel; the top slag modifier is added on the slag surface after the steel is completely tapped, and the addition amount is 0.5-3.0 kg / t·steel; The refining light treatment step: LF light treatment or RH light treatment is used; the LF light treatment, one-time aluminum deoxidation, control the oxygen [O] in the steel before adding aluminum to be 40-100 ppm, soft blowing of the molten steel for 8 min or more after adding aluminum, and the LF light treatment time is 15-20 minutes; the RH light treatment, the initial carbon / oxygen ratio [C] / [O] when entering the RH is 0.75-1.35, the oxygen content [O] of the molten steel before RH final deoxidation is ≤150 ppm, and the RH light treatment time is 15-20 minutes.

2. A refining light treatment process based on metallurgy of tapping process as claimed in claim 1 wherein: The converter tapping metallurgy step, the CaO / Al2O3 ratio in the ladle slag before the refining light treatment step is controlled to be 1.6-2.

0.

3. A refining light treatment process based on metallurgy of tapping process as claimed in claim 1 wherein, During the LF light treatment, the stirring intensity of the ladle bottom argon blowing is controlled in stages: 30-50 W / t in the heating stage, 300-500 W / t in the desulphurization stage, 100-200 W / t in the alloying stage, and 30-50 W / t in the soft blowing stage.

4. A refining light treatment process based on metallurgy of tapping process as claimed in claim 1 wherein: The refining light treatment step, the molten steel deoxidation requires white slag to be formed as soon as possible, the white slag basicity R is 1.5-2.0, and the FeO%+MnO% in the white slag is ≤1 wt%.

5. A refining light treatment process based on metallurgy of tapping process according to any one of claims 1-4, characterized in that: The hot metal desulphurization pretreatment step, the sulfur content of the hot metal after desulphurization is ≤the target sulfur content of the steel grade.