阅读说明：本技术 一种钢水rh真空精炼炉中氧含量的控制方法 (Method for controlling oxygen content in molten steel RH vacuum refining furnace ) 是由 解文中 牛金印 吴发达 石知机 王军 宋健 何宏涛 张明 于 2020-06-02 设计创作，主要内容包括：本发明涉及炼钢技术领域,具体来说是一种经RH真空脱碳钢水氧含量的控制方法,其特征在于,所述钢水进入RH真空精炼炉前在转炉中进行钢水的初步炼制；所述控制方法适用于转炉炼钢阶段；通过控制转炉初炼钢水的氧含量来控制后续进入RH真空精炼炉中钢水的氧含量。本发明公开了一种经RH真空脱碳钢水氧含量的控制方法,本发明通过在转炉炼钢工序对初炼钢水氧含量进行控制,可以避免在RH真空精炼炉精炼工序再次对钢水氧含量进行控制,从而降低RH真空精炼炉脱碳结束后钢水氧含量,进而降低铝切丸消耗、减少钢中夹杂物、提高钢材的质量。(The invention relates to the technical field of steelmaking, in particular to a method for controlling the water oxygen content of RH vacuum decarburization steel, which is characterized in that the preliminary refining of molten steel is carried out in a converter before the molten steel enters an RH vacuum refining furnace; the control method is suitable for the converter steelmaking stage; the oxygen content of the molten steel which enters the RH vacuum refining furnace subsequently is controlled by controlling the oxygen content of the primary molten steel of the converter. The invention discloses a method for controlling the oxygen content of water subjected to RH vacuum decarburization, which can avoid controlling the oxygen content of molten steel again in the refining process of an RH vacuum refining furnace by controlling the oxygen content of initial steelmaking water in the steelmaking process of a converter, thereby reducing the oxygen content of the molten steel after decarburization of the RH vacuum refining furnace is finished, further reducing the consumption of aluminum cutting shots, reducing inclusions in steel and improving the quality of steel.)

1. A control method for the water oxygen content of RH vacuum decarburization steel is characterized in that the preliminary refining of molten steel is carried out in a converter before the molten steel enters an RH vacuum refining furnace; the control method is suitable for the converter steelmaking stage; the oxygen content of the molten steel which enters the RH vacuum refining furnace subsequently is controlled by controlling the oxygen content of the primary molten steel of the converter.

2. The method for controlling the water oxygen content of RH vacuum decarbonized steel according to claim 1, which comprises the following steps:

(1) oxygen determination operation is carried out on the molten steel at the smelting end of the converter, and the oxygen is measuredEnd point molten steel actual oxygen content omega O]_{% end point}；

(2) According to the oxygen content of molten steel at the smelting end point of the converter and according to the formula omega O]_{% excess}＝ω[O]_{% end point}-△ω[O]_％-ω[O]_{% target}Calculating the actual excess oxygen content of the molten steel at the end point of the converter;

ω[O]_{% excess}: the content of the excess oxygen to be removed in the molten steel is called excess oxygen for short;

ω[O]_{% end point}: the oxygen content of molten steel at the end point of the converter, namely the oxygen determination value before the end point tapping;

△ω[O]_％: under the condition of no deoxidation, the oxygen content change value of the molten steel in the process from the tapping of the end point of the converter to the molten steel entering the RH vacuum refining furnace;

ω[O]_{% target}: the converter steelmaking process needs to be controlled to meet the optimal oxygen content target value of the primary molten steel required by the RH vacuum refining furnace;

when omega [ O ]]_{% excess}When the oxygen content is more than zero, the situation shows that the excess oxygen exists in the molten steel of the converter, the molten steel in the converter needs to be subjected to carbon powder deoxidation operation, and the process is switched to the next step:

(3) according to the actual excess oxygen content omega O of molten steel at the smelting end point of the converter]_{% excess}Calculating the carbon powder consumption required for removing the part of the excess oxygen;

(4) and carrying out carbon powder deoxidation operation in the steel tank in the converter tapping process.

3. The method for controlling the water oxygen content of RH vacuum decarbonized steel according to claim 2, wherein in the step (2), when omega [ O ] is measured]_{% excess}When the oxygen content is zero, the converter molten steel has no excess oxygen and can directly enter the next process if the oxygen content is omega O]When the% excess is less than zero, the actual oxygen content of the molten steel in the converter is lower than the required value, and oxygen needs to be supplied to the converter to properly increase the oxygen content of the molten steel.

4. The method for controlling the oxygen content of RH vacuum decarburized water according to claim 2, wherein the deoxidized carbon powder in the step (4) is added to the steel pot before tapping of the converter.

5. The method for controlling the water oxygen content of RH vacuum decarburized steel according to claim 4, wherein the deoxidation carbon powder is required to be completely added within 30 seconds before tapping of molten steel.

6. The method for controlling the water oxygen content of RH vacuum decarbonized steel according to claim 2, characterized in that the smelting end point ω [ O ] of the converter in the step (2)]_{% excess}Not less than 0.

7. The method for controlling the water oxygen content of RH vacuum decarbonized steel according to claim 6, characterized in that ω [ O ] is controlled by controlling the converter smelting end point carbon content]_{% end point}Numerical values.

8. The method for controlling the water oxygen content of RH vacuum decarbonized steel according to claim 7, characterized in that the end point carbon content of the converter, ω [ C ], is required]_{% end point}≤m_{Terminal point}/(△ω[O]_％+ω[O]_{% target})。

9. The method for controlling the water oxygen content of RH vacuum decarbonized steel according to claim 2, characterized in that the amount of carbon powder required for removing excess oxygen in step (3) is: the dosage of deoxidized carbon powder (Kg) is omega [ O ]]_{% excess}×10000(ppm)/6(ppm/Kg)。

Technical Field

The invention relates to the technical field of steel making, in particular to a method for controlling the water oxygen content of RH vacuum decarburization steel.

Background

At present, when producing ultra-low carbon steel grades such as ultra-low carbon automobile plates, ultra-low carbon cold rolled silicon steel and the like, the common process flow is as follows: molten iron pretreatment → converter → argon blowing station → RH → continuous casting, molten iron is added into the converter after the molten iron pretreatment deep desulfurization treatment, meanwhile, a proper amount of low-sulfur scrap steel is added for smelting under the premise of ensuring heat balance, primary molten steel smelted by the converter is refined in an RH vacuum refining furnace through the argon blowing station, and the refined qualified molten steel is conveyed to the continuous casting for casting. The RH vacuum refining furnace is used for further reducing carbon in molten steel to produce ultra-low carbon steel by utilizing the principle that [ C ] and [ O ] in the molten steel can further react to generate CO gas under the vacuum condition, and the reaction formula is [ C ] + [ O ] ═ CO }.

Therefore, the RH vacuum refining furnace has certain requirements on the oxygen content (namely the initial oxygen content) of the primary molten steel provided by the converter, and firstly, the RH vacuum decarburization requirements are met, and the carbon in the molten steel can be guaranteed to be removed to the range required by steel grade; and secondly, the residual oxygen content in the molten steel is required to be as low as possible after the RH vacuum decarburization is finished, so that the consumption of aluminum cutting shots during subsequent final deoxidation is reduced, the total amount of an aluminum deoxidation product Al2O3 is reduced, further, the Al2O3 inclusions in the steel are reduced, and the quality of the steel is improved.

Generally, the range of the RH vacuum refining furnace for the oxygen content of the primary molten steel is 400-800 ppm, the optimal range is 500-700 ppm, and the fluctuation is small, under the prior art condition, the converter often has large fluctuation of the oxygen content of the primary molten steel due to various factors such as furnace conditions, raw material conditions, operation and the like, and meanwhile, effective countermeasures are lacked, so that the ideal requirement of the RH vacuum refining furnace for the oxygen content of the primary molten steel cannot be met.

In the patent document (CN 106191376B), an ultra-low carbon aluminum killed steel vacuum carbon-adding pre-deoxidation process is adopted, firstly, a steel sample is taken before vacuum treatment to measure the oxygen content and temperature of molten steel, and the oxygen content in a station and the oxygen return amount in slag are measured to calculate the carbon powder amount required by pre-deoxidation; adding carbon powder into molten steel in batches for deoxidation; adding the last batch of carbon powder 3-5 min before the end of the decarburization period, wherein the interval of each batch is 1-2 min; 3-5 min after the last batch of carbon powder is added, sampling and determining oxygen, and controlling the oxygen content to be 50-250 ppm; calculating the amount of the added aluminum pills according to the oxygen determination result, and sampling 5-7 min after aluminum addition; and (5) after 20-25 min, fixing oxygen, sampling and finishing the whole deoxidation treatment. The patent is a remedy measure when the oxygen content of primary molten steel provided by a converter steelmaking process is higher than the required range, namely, carbon powder is added under the vacuum condition of an RH vacuum refining furnace refining process for pre-deoxidation to reduce the oxygen content of the molten steel, and the deoxidized carbon powder needs to be added in small quantities in batches, so that the molten steel refining period of the RH vacuum refining furnace is influenced, the production efficiency is reduced, if the adding amount of the carbon powder is not properly controlled, the safe production is also influenced, moreover, the process of the RH vacuum refining furnace without the condition of adding the carbon powder is limited, and therefore, the key to producing the ultra-low carbon steel is to control the oxygen content of the primary molten steel.

The process cannot solve the difficult problem of controlling the oxygen content of the initial steelmaking water from the steelmaking source, so that the problem to be solved urgently is how to control the oxygen content of the initial steelmaking water to meet the requirement of the RH vacuum refining furnace when the converter steelmaking process is used for producing ultra-low carbon steel as the last process of the refining process.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a method for controlling the oxygen content of RH vacuum decarbonized water.

In order to achieve the purpose, the invention adopts the technical scheme that:

a control method for the water oxygen content of RH vacuum decarburization steel is characterized in that the preliminary refining of molten steel is carried out in a converter before the molten steel enters an RH vacuum refining furnace; the control method is suitable for the converter steelmaking stage; the oxygen content of the molten steel which enters the RH vacuum refining furnace subsequently is controlled by controlling the oxygen content of the primary molten steel of the converter.

A control method for the water oxygen content of RH vacuum decarbonized steel comprises the following steps:

(1) oxygen determination operation is carried out on the molten steel at the smelting end point of the converter, and the actual oxygen content omega O of the molten steel at the end point is measured]_{% end point}；

(2) According to the oxygen content of molten steel at the smelting end point of the converter and according to the formula omega O]_{% excess}＝ω[O]_{% end point}-△ω[O]_％-ω

[O]_{% target}Calculating the actual excess oxygen content of the molten steel at the end point of the converter;

ω[O]_{% excess}: the content of the excess oxygen to be removed in the molten steel is called excess oxygen for short;

ω[O]_{% end point}: the oxygen content of molten steel at the end point of the converter, namely the oxygen determination value before the end point tapping;

△ω[O]_％: under the condition of no deoxidation, the oxygen content change value of the molten steel in the process from the tapping of the end point of the converter to the molten steel entering the RH vacuum refining furnace;

ω[O]_{% target}: the converter steelmaking process needs to be controlled to meet the optimal oxygen content target value of the primary molten steel required by the RH vacuum refining furnace;

when omega [ O ]]_{% excess}When the oxygen content is more than zero, the situation shows that the excess oxygen exists in the molten steel of the converter, the molten steel in the converter needs to be subjected to carbon powder deoxidation operation, and the process is switched to the next step:

(3) according to the actual excess oxygen content omega O of molten steel at the smelting end point of the converter]_{% excess}Calculating the carbon powder consumption required for removing the part of the excess oxygen;

(4) and carrying out carbon powder deoxidation operation in the steel tank in the converter tapping process.

In the step (2), when ω [ O ]]_{% excess}When the oxygen content is zero, the converter molten steel has no excess oxygen and can directly enter the next process if the oxygen content is omega O]When the% excess is less than zero, the actual oxygen content of the molten steel in the converter is lower than the required value, and oxygen needs to be supplied to the converter to properly increase the oxygen content of the molten steel.

And (4) adding the deoxidized carbon powder into a steel tank in the early stage of converter tapping.

The deoxidizing carbon powder is required to be put in 30 seconds before molten steel tapping.

The smelting end point omega [ O ] of the converter in the step (2)]_{% excess}Not less than 0.

Controlling omega O by controlling the carbon content at the smelting end point of the converter]_{% end point}Numerical values.

The end point carbon content omega C of the converter is required]_{% end point}≤m_{Terminal point}/(△ω[O]_％+ω[O]_{% target})。

The carbon powder dosage required for removing the excess oxygen in the step (3) is as follows: the dosage of deoxidized carbon powder (Kg) is omega [ O ]]_{% excess}×10000(ppm)/6(ppm/Kg)。

The invention has the advantages that:

the invention discloses a method for controlling the oxygen content of water subjected to RH vacuum decarburization, which can avoid controlling the oxygen content of molten steel again in the refining process of an RH vacuum refining furnace by controlling the oxygen content of initial steelmaking water in the steelmaking process of a converter, thereby reducing the oxygen content of the molten steel after decarburization of the RH vacuum refining furnace is finished, further reducing the consumption of aluminum cutting shots, reducing inclusions in steel and improving the quality of steel; the control method disclosed by the invention effectively improves the control precision of the converter steelmaking process on the oxygen content of the primary steelmaking water, meets the requirement of the RH vacuum refining furnace refining process on the oxygen content of the primary steelmaking water, creates favorable conditions for the next process and improves the production efficiency of ultra-low carbon steel;

drawings

The following is a brief description of the various views of the present specification:

FIG. 1 is a flow chart of a process for producing ultra-low carbon steel.

FIG. 2 is a flow chart of the operation of the present invention.

Detailed Description

The following description of preferred embodiments of the invention will be made in further detail with reference to the accompanying drawings.

A control method for the water oxygen content of RH vacuum decarburization steel is characterized in that the preliminary refining of molten steel is carried out in a converter before the molten steel enters an RH vacuum refining furnace; the control method is used in the converter steelmaking stage; controlling the oxygen content of the molten steel which enters an RH vacuum refining furnace subsequently by controlling the oxygen content of the primary molten steel of the converter; the invention discloses a method for controlling the oxygen content of water subjected to RH vacuum decarburization, which can avoid controlling the oxygen content of molten steel again in the refining process of an RH vacuum refining furnace by controlling the oxygen content of initial steelmaking water in the steelmaking process of a converter, thereby reducing the oxygen content of the molten steel after decarburization of the RH vacuum refining furnace is finished, further reducing the consumption of aluminum cutting shots, reducing inclusions in steel and improving the quality of steel; in other words, the method changes the traditional control mode of the oxygen content of molten steel, and the oxygen content in the molten steel is controlled at the steelmaking stage of the converter, so that the subsequent pre-deoxidation by adding carbon powder in the refining process of the RH vacuum refining furnace is avoided; because carbon powder is added in the refining procedure of the RH vacuum refining furnace for pre-deoxidation; not only influences the molten steel refining period of the RH vacuum refining furnace and reduces the production efficiency, but also causes adverse effects on safe production if the adding amount of the carbon powder is improperly controlled, and moreover, the process of the RH vacuum refining furnace without the condition of adding the carbon powder is limited, namely the refining process of the RH vacuum refining furnace by adding the carbon powder for pre-deoxidation has no universality; the invention can solve the problem of controlling the oxygen content of the primary steelmaking water from the steelmaking source by controlling the oxygen content of the primary steelmaking molten steel in the early stage.

The invention is characterized in that under the condition that the working conditions of the same or similar converters are the same, molten steel from the end point of the converter to the end of the converter is fed into an RH vacuum refining furnace through an argon blowing station, and the oxygen content change value of the molten steel is △ omega O under the condition that the molten steel is not deoxidized]_％Substantially constant, according to the formula ω [ O ]]_{% excess}＝ω[O]_{% end point}-△ω[O]_％-ω[O]_{% target}And calculating the terminal excess oxygen content of the converter, and removing the excess oxygen by adopting a proper amount of high-quality carbon powder according to the calculation result so as to achieve the aim of accurately controlling the oxygen content of the primary molten steel.

Formula omega [ O ]]_{% excess}＝ω[O]_{% end point}-△ω[O]_％-ω[O]_{% target}The method comprises the following steps:

ω[O]_{% excess}Excess oxygen content to be removed in the molten steel, referred to as excess oxygen;

ω[O]_{% end point}The oxygen content of molten steel at the end point of the converter, namely the oxygen determination value before the end point tapping;

△ω[O]_％-the value of the oxygen content variation of the steel from tapping at the end of the converter to feeding into the RH vacuum refining furnace without deoxidation;

ω[O]_{% target}The converter steelmaking process needs to be controlled to meet the optimal oxygen content target value of the primary molten steel required by the RH vacuum refining furnace.

When the excess oxygen content omega [ O ] of molten steel is calculated according to the above formula, the following three conditions exist as the calculation result:

1.ω[O]_{% excess}If the oxygen content is more than 0, indicating that the excess oxygen exists in the converter molten steel, a proper amount of high-quality carbon powder is needed to remove the excess oxygen;

2.ω[O]_{% excess}When the value is 0, the converter molten steel has no excess oxygen and does not need to be deoxidized;

3.ω[O]_{% excess}And < 0, indicating that the actual oxygen content of the molten steel in the converter is lower than a required value, and oxygen supply supplementary blowing of the converter is required to properly improve the oxygen content of the molten steel.

Under the condition of the prior art, the converter can not accurately control the excess oxygen content of the molten steel at the end point to be omega O]_{% excess}0; and at the end point the excess oxygen content of molten steel is omega O]_{% excess}When the oxygen content of the molten steel is less than 0, the converter needs oxygen supply and supplementary blowing to properly improve the oxygen content of the molten steel, and the oxygen content of the molten steel needs to be determined and the excess oxygen content is calculated again after the supplementary blowing is finished, and the operations are repeated, so that the production efficiency, the end-point hit rate, the furnace condition, the consumption and the like of the converter are influenced to a certain extent; therefore, in actual operation, the excess oxygen content of molten steel at the end point of the converter is expressed as ω [ O ]]_{% excess}Is more than or equal to 0 and is matched as much as possible according to actual conditions

ω[O]_{% excess}And (5) controlling.

In order to achieve the purpose, the invention adopts the specific technical scheme that the method comprises the following steps:

1. the smelting end point of converter is controlled according to omega O% excess not less than 0, and omega O% excess is reduced as far as possible.

From the carbon oxygen concentration product: under a certain temperature and pressure, the product of the mass percent concentration of carbon and oxygen in the molten steel is a constant, i.e. m is omega [ C%]_％·ω[O]_％M is constant regardless of the concentrations of reactants and products.

The product of carbon and oxygen concentration is expressed as m ═ ω [ C ]]_％·ω[O]% or m [% C]·[％O]

Under the condition that the working conditions of the same or similar converters are the same, the smelting end point pressure of the converter is basically constant, and the fluctuation of the end point temperature of the molten steel among the super-low carbon steel smelting furnaces of the converter is not large, so the carbon-oxygen concentration product m of the end point molten steel_{Terminal point}＝ω[C]_{% end point}·ω[O]_{% end point}The value is basically constant, and the decisive effect on the final molten steel oxygen content is the final molten steel carbon content which can be determined by oxygen supply amount of oxygen lance, oxygen supply time, calculation of decarburization speed and flame observation of furnace mouth, so that the final molten steel carbon content omega [ C ] of converter can be controlled]_{% end point}Can control the oxygen content omega O at the end point of the converter]_{% end point}Further control omega [ O ]]_{% excess}。

ω[C]_{% end point}Determining a control range:

due to omega [ O ]]_{% excess}＝ω[O]_{% end point}-△ω[O]_％-ω[O]_{% target}

m_{Terminal point}＝ω[C]_{% end point}·ω[O]_{% end point}

To make omega O]_{% excess}≥0

Then omega [ C]_{% end point}≤m_{Terminal point}/(△ω[O]_％+ω[O]_{% target})

M in the above formula is m in the same converter under the same or similar working conditions_{Terminal point}、△ω[O]_％、ω[O]_{% target}Substantially constant, omega C]_{% end point}The control range can be determined by calculation.

Therefore, to achieve this step the converter smelting end point is scaled to omega [ O ]]_{% excess}Not less than 0 and reducing [ O ] as much as possible]_{Excess of}The purpose of the control is that the control is carried out,can control the end point carbon omega C of the converter]_{% end point}≤m_{Terminal point}/(△ω[O]_％+ω[O]_{% target}) And pressing ω [ C ] if conditions permit]_{% end point}As close to m as possible_{Terminal point}/(△ω[O]_％+ω[O]_{% target}) And (5) controlling.

A control method for the water oxygen content of RH vacuum decarbonized steel comprises the following steps: (1) oxygen determination operation is carried out on the molten steel at the smelting end point of the converter, and the actual oxygen content omega O of the molten steel at the end point is measured]_{% end point}；

(2) According to the oxygen content of molten steel at the smelting end point of the converter and according to the formula omega O]_{% excess}＝ω[O]_{% end point}-△ω[O]_％-ω

[O]_{% target}Calculating the actual excess oxygen content of the molten steel at the end point of the converter;

ω[O]_{% excess}: the content of the excess oxygen to be removed in the molten steel is called excess oxygen for short;

ω[O]_{% end point}: the oxygen content of molten steel at the end point of the converter, namely the oxygen determination value before the end point tapping;

△ω[O]_％: under the condition of no deoxidation, the oxygen content change value of the molten steel in the process from the tapping of the end point of the converter to the molten steel entering the RH vacuum refining furnace;

ω[O]_{% target}: the converter steelmaking process needs to be controlled to meet the optimal oxygen content target value of the primary molten steel required by the RH vacuum refining furnace;

when omega [ O ]]_{% excess}When the oxygen content is more than zero, the situation shows that the excess oxygen exists in the molten steel of the converter, the molten steel in the converter needs to be subjected to carbon powder deoxidation operation, and the process is switched to the next step:

(3) according to the actual excess oxygen content omega O of molten steel at the smelting end point of the converter]_{% excess}Calculating the carbon powder consumption required for removing the part of the excess oxygen;

(4) and carrying out carbon powder deoxidation operation in the steel tank in the converter tapping process.

And (3) feeding the primary molten steel into an RH vacuum refining furnace for oxygen determination through an argon blowing station.

The above is the main control method, and the specific embodiment is as follows:

the implementation steps and the operational control points of the invention are further explained by the following examples of smelting ultra-low carbon steel in a 120t converter. The embodiment is a 120t converter, but the invention is not limited to the 120t converter, but is applicable to converters with all tonnages.

When the 120t converter is used for smelting the ultra-low carbon steel, the process requires that the converter tapping amount is controlled according to 128-132 (t/furnace), and the average tapping amount is 130 t/furnace.

The reaction formula of the carbon powder deoxidation is [ C ] + [ O ] ═ CO }, the carbon content of the selected carbon powder is 93%, and theoretically, 1Kg of carbon powder can remove [0] from about 9.5ppm of molten steel.

That is 1000000 × (1 × 93% × 16)/(12 × 130 × 1000) ≈ 9.5ppm, the practical data statistics result shows that 1Kg of carbon powder can only remove 6ppm of [ O ] on average due to certain loss of carbon powder deoxidation, so the dosage (Kg) of the deoxidized carbon powder is ω [ O ]% and is excessive × 10000(ppm)/6 (ppm/Kg).

Under the current working condition of a 120t converter, molten steel enters an RH vacuum refining furnace from the end point tapping to the end point tapping of the converter through an argon blowing station, and the oxygen content of the molten steel is averagely reduced by 200ppm, namely △ omega O under the condition that the molten steel is not deoxidized]% 0.02, i.e. 200 ppm; the RH vacuum refining furnace requires 400-800 ppm of oxygen content of primary molten steel, the optimal range is 500-700 ppm, the optimal control target is set to 600ppm, namely omega [ O ]]_{% target}When the carbon-oxygen concentration product of the ultra-low carbon steel grade smelted by the converter under the current working condition is 0.06, the average value is 0.0039, and the m end point/(△ omega [ O ]]％+ω[O]% target)

＝0.0039/(0.02+0.06)

＝0.04875≈0.05。

Therefore, in order to control the converter smelting end point to be more than or equal to 0% in terms of omega [ O ] excess and to reduce the [ O ] excess as much as possible, the converter end point carbon is controlled to be less than or equal to 0.05 in terms of omega [ C ] percent end point and to be as close to 0.05 as possible when conditions permit.

The following is a specific embodiment of the invention applied to the smelting of ultra-low carbon steel in the 120t converter;

in the above embodiment, the invention sets the control target for the oxygen content of the water in the initial steelmaking of the ultra-low carbon steel to be 600ppm, the actual maximum is 616ppm, the minimum is 585ppm, the control precision is within +/-16 ppm, and the set target with the expected control precision within +/-50 ppm is completely achieved.

Preferably, the deoxidized carbon powder in the step (4) is added into the steel tank as early as possible in the early stage of converter tapping; adding carbon powder into the steel tank to react with oxygen in the molten steel: [C] and (2) reacting with { CO }, wherein the CO gas as a product can strongly stir the molten steel in the floating and removing process, and if the deoxidized carbon powder is added too late, the molten steel in the steel tank is easy to tumble and overflow out of the steel tank under the action of the carbon-oxygen reaction, so that an accident is caused. In the early tapping stage of the converter, less molten steel is in the steel tank, the free space is large, and the deoxidized carbon powder is added into the steel tank in the early tapping stage, so that accidents can be effectively avoided.

The invention adopts high-quality carbon powder to deoxidize the molten steel in the steel tank, the carbon powder is added into the steel tank in the early stage of converter tapping and generates with oxygen in the molten steel: [C] the product is CO gas, no residue exists in the molten steel, and the CO gas has the functions of degassing, inclusion and molten steel purification in the floating and removing process; meanwhile, the stirring effect of the floating CO gas on the molten steel further promotes the melting of the slag charge added into the steel tank, and the slag charge is prevented from lumping; the addition of the deoxidized carbon powder calculated according to the invention has a certain weak carburization effect, the carburization amount is reduced along with the increase of the end-point carbon content of the converter, and the carburization is obvious when the carbon content of the molten steel is less than 0.035%, therefore, the carbon content in the molten steel reaches the ideal control range of (0.04% -0.05%) while the molten steel is deoxidized by using a proper amount of carbon powder, which can just meet the requirement of carbon-oxygen coordination of the RH vacuum refining furnace on the initial refining of the molten steel, is favorable for further reducing the oxygen content of the molten steel after the decarburization is finished, and effectively controls the oxygen content of the molten steel within 250ppm after the decarburization is finished.

The converter tapping time is the time from the beginning of converter tapping to the end of tapping, generally 3-6 minutes, the tapping time of a new tapping hole is longer, the tapping hole is eroded by molten steel and slag along with the increase of the using times of the tapping hole, and the inner diameter of the tapping hole is increased, so that the tapping time of an old tapping hole is shorter. Preferably, the deoxidized carbon powder is controlled to be put in the steel tapping within 30 seconds, and the aim is to ensure that the deoxidized carbon powder is added into a steel tank as early as possible in the early stage of the steel tapping of the converter and reacts with [ O ] in molten steel as soon as possible so as to avoid accidents caused by the fact that the deoxidized carbon powder is added too late.

Preferably, in the step (2) of the present invention, the smelting end point ω [ O ] of the converter is]_{% excess}Not less than 0; avoiding the need of carrying out oxygen supplement operation on the molten steel again when the oxygen content is less than 0, and reducing the trouble of the working procedure.

Preferably, in the invention, the omega [ O ] is controlled by controlling the carbon content at the smelting end point of the converter]_{% end point}A numerical value; can be used for omega [ O ]]_{% end point}Controlling the numerical value of (1); the method is convenient for actual production needs.

It is clear that the specific implementation of the invention is not restricted to the above-described embodiments, but that various insubstantial modifications of the inventive process concept and technical solutions are within the scope of protection of the invention.