1. An aluminum adding method for RH vacuum refining ultra-low carbon steel is characterized in that: in the RH vacuum refining process; (1) when the carbon content in the molten steel reaches a target value, if the temperature of the molten steel does not reach the outbound target temperature, adding aluminum and blowing oxygen to raise the temperature, wherein the aluminum adding amount required by the temperature rise is calculated by adopting the following formula (I):

Al_{heating of}=C_{Heating Al}X molten steel quantity x delta T (I)

In the formula:

Al_{heating of}: the amount of aluminum added for heating is kg;

molten steel amount: weight of molten steel, t;

Δ T: desired total temperature rise, ° c;

C_{heating Al}: the heating coefficient of the aluminum is 0.033 kg-Al/t DEG C;

(2) in the refining process, when the carbon content in the molten steel reaches a target value and the temperature of the molten steel reaches an outbound target temperature, or after the temperature in the step (1) is raised to reach the outbound target temperature, detecting the oxygen level of the molten steel at the moment; calculating the aluminum adding amount according to the following formula (II), and adding aluminum particles at one time;

Alt=（8×10^-7）Oxy²+0.001*Oxy+0.016+0.001Als/η （Ⅱ）

in the formula:

and (3) Alt: calculated aluminum adding amount, kg/t;

oxy: the detected oxygen level of the molten steel is ppm;

and Als: the target acid-soluble aluminum content of the ultra-low carbon steel is ppm;

eta: the yield of aluminum in alloying is 68-75 percent.

2. The method of aluminizing an ultra-low carbon steel by RH vacuum refining according to claim 1, wherein: in the step (1), the oxygen blowing amount when the temperature is raised by adding aluminum oxygen blowing is calculated by adopting the following formula (III):

Q=Al_{heating of}*0.88/1.429/O_{2 utilization ratio} （Ⅲ）

In the formula:

q: oxygen blowing amount, m³；

Al_{Heating of}: the amount of aluminum added for heating is kg;

O_{2 utilization ratio}: the oxygen utilization rate is selected from 60-80%.

3. The method of aluminizing an ultra-low carbon steel by RH vacuum refining according to claim 1, wherein: the degree of vacuum of the RH refining was controlled to 2.5mbar or less.

4. The method of aluminizing an ultra-low carbon steel by RH vacuum refining according to claim 1, wherein: the thickness of the slag at the beginning of RH refining and smelting is less than or equal to 200 mm.

5. The method for aluminizing an ultra-low carbon steel by RH vacuum refining according to any one of claims 1 to 4, wherein: the aluminum content in the ultra-low carbon steel is less than or equal to 1000 ppm.

Background

In the RH refining process, molten steel is alloyed to meet the requirements of target components, but the high oxygen level of the molten steel cannot meet the control index of higher alloy yield, and the accurate control of the oxygen level in the molten steel by using aluminum as a strong deoxidizer is particularly important. Meanwhile, the precise control of acid-soluble aluminum in steel is related to whether the steel grade plan, the product performance stability and the like are changed, so that the accurate calculation of the adding amount of aluminum not only can ensure the stability of the target components of qualified molten steel, but also can reduce the cost of molten steel per ton of steel.

Patent application CN201410388214.0 "a method for adding aluminum to smelt iron chromium-aluminum alloy", said aluminum adding process is carried out in a VOD furnace, specifically comprising the following steps: smelting iron chromium-aluminum products by adopting stainless steel smelting processes such as VOD (vacuum oxygen decarburization) and the like, wherein the process comprises the following steps: electric furnace + VOD smelting method, intermediate frequency furnace + VOD, converter + VOD and electric furnace + AOD + VOD smelting method, etc. (there may be other smelting furnaces behind the VOD furnace); the molten steel smelted in the first step meets certain requirements on components, temperature and slag quantity; in the second step of smelting in the VOD furnace, the amount of slag in the smelting process of the VOD furnace is controlled; according to the measures of good air isolation capability in the vacuum metallurgy process, increasing the stirring strength in the reduction period and the like, the yield of the aluminum is improved to more than 80 percent. The method is an aluminum adding method adopted when smelting iron-chromium-aluminum alloy by a VOD furnace, is not suitable for an RH refining process and is also not suitable for smelting ultra-low carbon steel.

Disclosure of Invention

The invention aims to solve the technical problem of providing an aluminum adding method for RH vacuum refining ultra-low carbon steel, which is stable in aluminum adding and high in aluminum supplementing hit rate.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: in the RH vacuum refining process; (1) when the carbon content in the molten steel reaches a target value, if the temperature of the molten steel does not reach the outbound target temperature, adding aluminum and blowing oxygen to raise the temperature, wherein the aluminum adding amount required by the temperature rise is calculated by adopting the following formula (I):

Al_{heating of}=C_{Heating Al}X molten steel quantity x delta T (I)

In the formula:

Al_{heating of}: the amount of aluminum added for heating is kg;

molten steel amount: weight of molten steel, t;

Δ T: desired total temperature rise, ° c;

C_{heating Al}: the heating coefficient of the aluminum is 0.033 kg-Al/t DEG C;

(2) in the refining process, when the carbon content in the molten steel reaches a target value and the temperature of the molten steel reaches an outbound target temperature, or after the temperature is raised in the step (1) and the outbound target temperature is reached, detecting the oxygen level of the molten steel at the moment; calculating the aluminum adding amount according to the following formula (II), and adding aluminum particles at one time;

Alt=（8×10^-7）Oxy²+0.001*Oxy+0.016+0.001Als/η （Ⅱ）

in the formula:

and (3) Alt: calculated aluminum adding amount, kg/t;

oxy: the detected oxygen level of the molten steel is ppm;

and Als: the target acid-soluble aluminum content of the ultra-low carbon steel is ppm;

eta: the yield of aluminum in alloying is 68-75 percent.

In the step (1), the oxygen blowing amount when the temperature is raised by adding aluminum and blowing oxygen is calculated by the following formula (III):

Q=Al_{heating of}*0.88/1.429/O_{2 utilization ratio} （Ⅲ）

In the formula:

q: oxygen blowing amount, m³；

Al_{Heating of}: the amount of aluminum added for heating is kg;

O_{2 utilization ratio}: the oxygen utilization rate is selected from 60-80%.

The vacuum degree of RH refining is controlled to be 2.5mbar or less.

The slag thickness at the beginning of RH refining smelting is less than or equal to 200 mm.

The aluminum content in the ultra-low carbon steel is less than or equal to 1000 ppm.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: the method realizes accurate calculation and feeding through an operation program, considers the influence of the vacuum degree on the aluminum absorption rate and the influence of the slag layer thickness on the aluminum feeding amount in the RH refining process, and can accurately calculate the aluminum feeding amount required in the molten steel. The method can accurately add aluminum, avoid adding aluminum for many times, improve the hit rate of adding aluminum for one time, improve the hit rate of supplementing aluminum for one time to more than 92 percent, and effectively improve the hit rate by more than 12 percent compared with the prior art; the method can ensure primary aluminum supplement, improve the hit rate of the primary aluminum supplement, meet the requirements of the components required by molten steel, reduce the fluctuation of Als components in the steel and reduce the alloy loss. The method can control the threshold value of the calculated value of the aluminum content of the end point and the actual measured value to be +/-50 ppm, accurately and quickly realize the control of the feeding amount of the RH refining, and provide guidance for the refining. The invention carries out smelting according to the process requirements of oxygen level, molten steel amount, slag layer thickness, vacuum degree control and the like, realizes the stability of RH refining feeding, improves the hit rate of primary aluminum supplement, meets the component requirements of molten steel, reduces the fluctuation of Als components in steel and reduces alloy loss; has popularization and application value for the smelting production of the actual steel mill.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments.

The aluminum adding method for RH vacuum refining ultra-low carbon steel adopts the following processes: (1) in the process of RH refining ultra-low carbon steel, the vacuum degree is controlled to be 2.5mbar or less; the slag thickness is less than or equal to 200mm at the beginning of RH refining smelting; the aluminum content in the ultra-low carbon steel is less than or equal to 1000ppm, and the steel types comprise IF steel such as SPHETi-3, SPHE-3 and the like.

(2) In the RH refining process, when the carbon content in the molten steel reaches the target value of the steel grade, the temperature drop in the RH treatment process before the molten steel is discharged, the temperature drop of the molten steel during alloy addition and the temperature rise during aluminum addition are considered, and the temperature of the molten steel at the time is not less than the discharge temperature of the steel grade. If the temperature of the molten steel meets the above conditions, detecting the oxygen level of the molten steel at the moment; calculating the aluminum adding amount according to the following formula (II), and adding aluminum particles at one time through a high-position bin;

Alt=（8×10^-7）Oxy²+0.001*Oxy+0.016+0.001Als/η （Ⅱ）

in the formula:

and (3) Alt: calculated aluminum adding amount, kg/t;

oxy: the detected oxygen level of the molten steel is ppm;

and Als: the target acid-soluble aluminum content of the ultra-low carbon steel is ppm;

eta: the yield of aluminum in alloying is 68-75%, preferably 70%.

(3) In the RH refining process, after the carbon content in the molten steel reaches the target value of the refined steel grade, if the temperature of the molten steel is lower than the outbound temperature, aluminum blowing oxygen is added for heating.

The aluminum adding amount required for temperature rise is calculated by adopting the following formula (I) in one step:

Al_{heating of}=C_{Heating Al}X molten steel quantity x delta T (I)

In the formula:

Al_{heating of}: the amount of aluminum added for heating is kg;

molten steel amount: weight of molten steel, t;

Δ T: desired total temperature rise, ° c;

C_{heating Al}: the heating coefficient of aluminum, 0.033 kg. Al/t. degree.C.

The oxygen blowing amount at the time of heating by blowing oxygen with aluminum was calculated by the following formula (III):

Q=Al_{heating of}*0.88/1.429/O_{2 utilization ratio} （Ⅲ）

In the formula:

q: oxygen blowing amount, m³；

Al_{Heating of}: the amount of aluminum added for heating is kg;

O_{2 utilization ratio}: the oxygen utilization rate is calculated according to 60-80%.

After heating up by adding aluminum and blowing oxygen, raising the temperature to reach the target temperature of leaving the station, and detecting the oxygen level of the molten steel at the moment; calculating the aluminum adding amount according to the following formula (II), and adding aluminum particles at one time through a high-position bin;

Alt=（8×10^-7）Oxy²+0.001*Oxy+0.016+0.001Als/η （Ⅱ）

in the formula:

and (3) Alt: calculated aluminum adding amount, kg/t;

oxy: the detected oxygen level of the molten steel is ppm;

and Als: the target acid-soluble aluminum content of the ultra-low carbon steel is ppm;

eta: the yield of aluminum in alloying is 68-75%, preferably 70%.

Example 1: the aluminum adding method for RH vacuum refining ultra-low carbon steel adopts the following specific process.

(1) The produced ultra-low carbon steel is SPHETi-3, and the components of the steel are required to be shown in the following table 1; the total amount of molten steel in the furnace is 200 t; the outbound temperature is required to be 1611-1636 ℃, and the target carbon content is 0.003%.

Table 1: the SPHETi-3 steel grade requires (wt%)

In table 1, the balance of the components is Fe and inevitable impurities.

(2) Starting RH refining through a jacking system, and vacuumizing until the vacuum degree reaches 1.8 mbar; the thickness of the molten steel slag of the furnace is 100 mm. C content is measured by sampling to reach 0.0025 percent, and the target carbon content is achieved; the temperature of the molten steel at the moment is measured to be 1622 ℃, the temperature meets the outbound target temperature, and the temperature is raised without adding aluminum and blowing oxygen; the oxygen level was 301ppm and the target aluminum content was 350 ppm. Calculated according to the above formula (II): alt = (8 × 10)^-7）Oxy²+0.001*Oxy+0.016+0.001Als/η=(8×10^-7)301²+0.001 × 301+0.016+0.001 × 350/0.7=0.0725+0.301+0.016+0.5= 0.8895; 0.8895 x 200=177.9kg of aluminum particles are added, and 178kg of aluminum particles are added at one time through an overhead bunker; and sampling after 3 minutes, wherein the measured Al content is 340ppm, the deviation between the calculated value of the end point aluminum content and the actual measured value is 10ppm, the components reach the standard, and the aluminum particle waste is not caused.

Example 2: the aluminum adding method for RH vacuum refining ultra-low carbon steel adopts the following specific process.

(1) The produced ultra-low carbon steel is SPHETi-3, and the components of the steel are required to be as shown in the table 1; the total amount of the furnace molten steel is 205 t; the outbound temperature is required to be 1611-1636 ℃, and the target carbon content is 0.0030%.

(2) Starting RH refining through a jacking system, and vacuumizing until the vacuum degree reaches 2.0 mbar; the thickness of the molten steel slag of the furnace is 95mm, and the C content is measured by sampling to reach 0.0028 percent, so that the target carbon content is achieved; the temperature of the molten steel is measured to be 1600 ℃, aluminum blowing oxygen is required to be added for heating, and the temperature is expected to be increased to 1621 ℃. Calculating according to the formula (I) and the formula (III): al (Al)_{Heating of}= C_{Heating Al}X molten steel amount × Δ T =0.033 × 205 × 21=142kg, Q = Al_{Heating of}*0.88/1.429/O_{2 utilization ratio}=142*0.88/1.429/0.6=146m³(ii) a According to the calculated amount, 142kg of aluminum is added, and the oxygen blowing amount is 146m³(ii) a Sampling after 3 minutes, and measuring the temperature to 1620 ℃, wherein the temperature meets the outbound target temperature; the oxygen level was 246ppm and the target aluminum content was 350 ppm. Calculated according to the above formula (II): alt = (8 × 10)^-7）Oxy²+0.001 × Oxy +0.016+0.001Als/η =0.0484+0.246+0.016+0.5= 0.8104; adding 0.8104 x 205=166.1kg of aluminum particles, and adding 166kg of aluminum particles at one time through an overhead bunker; sampling is carried out after 3 minutes, the measured Al content is 352ppm, the deviation between the calculated value of the end point aluminum content and the actual measured value is 2ppm, the components reach the standard, and the aluminum particle waste is not caused.

Example 3: the aluminum adding method for RH vacuum refining ultra-low carbon steel adopts the following specific process.

(1) The produced ultra-low carbon steel is SPHETi-3, and the components of the steel are required to be as shown in the table 1; the total amount of molten steel in the furnace is 202 t; the outbound temperature is required to be 1611-1636 ℃, and the target carbon content is 0.0030%.

(2) Starting RH refining through a jacking system, and vacuumizing until the vacuum degree reaches 2.5 mbar; the thickness of the molten steel slag of the furnace is 120mm, and the C content is measured by sampling to reach 0.0030 percent, so that the target carbon content is reached; the temperature of the molten steel at this time was 1602 ℃, and it was necessary to increase the temperature by blowing oxygen with aluminum, and it was expected that the temperature was increased to 1615 ℃. According to the above formula (I)) Calculating by the formula (III): al (Al)_{Heating of}=0.033*202*13=86.7kg、Q=86.7*0.88/1.429/0.8=66.7m³(ii) a According to the calculated amount, 86.7kg of aluminum is added, and the oxygen blowing amount is 66.7m³(ii) a Sampling after 3 minutes, and measuring the temperature to 1617 ℃, wherein the temperature meets the outbound target temperature; at this time, the oxygen level was 283ppm, and since this furnace was the first furnace, the target aluminum content was 50ppm higher than that of the conventional furnace, the target aluminum content was set to 400 ppm. Calculated according to the above formula (II): alt = (8 × 10)^-7)283²+0.001 × 283+0.016+0.001 × 400/0.7=0.0641+0.283+0.016+0.5714= 0.9345; adding 0.9345 x 202=188.8kg of aluminum particles, and adding 189kg of aluminum particles at one time through an overhead bunker; sampling is carried out after 3 minutes, the measured Al content is 405ppm, the deviation between the calculated value of the end point aluminum content and the actual measured value is 5ppm, the components reach the standard, and the aluminum particle waste is not caused.

Example 4: the aluminum adding method for RH vacuum refining ultra-low carbon steel adopts the following specific process.

(1) The produced ultra-low carbon steel is SPHETi-3, and the components of the steel are required to be as shown in the table 1; the total amount of molten steel in the furnace is 200 t; the outbound temperature is required to be 1611-1636 ℃, and the target carbon content is 0.0030%.

(2) Starting RH refining through a jacking system, and vacuumizing until the vacuum degree reaches 2.2 mbar; the thickness of the molten steel slag of the furnace is 200mm, and the C content is measured by sampling to reach 0.0027 percent, so that the target carbon content is achieved; the temperature of the molten steel is measured to be 1610 ℃, aluminum blowing oxygen is required to be added for raising the temperature, and the temperature is desirably raised to 1630 ℃. Calculating according to the formula (I) and the formula (III): al (Al)_{Heating of}=0.033*200*20=132kg、Q=132*0.88/1.429/0.7=116.1m³(ii) a According to the calculated amount, 132kg of aluminum is added, and the oxygen blowing amount is 116m³(ii) a After 3 minutes sampling was performed and the temperature was determined to be 1629 deg.C, which met the outbound target temperature, at which point the oxygen level was 268ppm and the target aluminum content was 350 ppm. Calculated according to the above formula (II): alt = (8 × 10)^-7)268²+0.001 × 268+0.016+0.001 × 350/0.68=0.0575+0.268+0.016+0.5147= 0.8562; 0.8562 x 200=171.24kg of aluminum particles are required to be added, and 171kg of aluminum particles are added at one time through an overhead bunker; sampling after 3 minutes, measuring that the Al content is 346ppm, the deviation of the calculated value of the end point aluminum content and the actual measured value is 4ppm, the components reach the standard and do not causeThe aluminum particles are wasted.

Example 5: the aluminum adding method for RH vacuum refining ultra-low carbon steel adopts the following specific process.

(1) The produced ultra-low carbon steel is SPHE-3, and the components of the steel are required to be shown in the following table 2; the total amount of the furnace molten steel is 203 t; the outbound temperature is required to be 1611-1636 ℃, and the target carbon content is 0.0040%.

SPHE-3 Steel grade composition requirements (wt%) as set forth in Table 2

In table 2, the balance of the components is Fe and inevitable impurities.

(2) Starting RH refining through a jacking system, and vacuumizing until the vacuum degree reaches 1.9 mbar; the thickness of the molten steel slag of the furnace is 110mm, and the C content is measured by sampling to reach 0.0038 percent, so that the target carbon content is reached; the temperature of the molten steel is measured to be 1612 ℃, the temperature meets the outbound target temperature, and the temperature is raised without adding aluminum and blowing oxygen; the oxygen level was 280ppm and the target aluminum content was 350 ppm. Calculated according to the above formula (II): alt = (8 × 10)^-7)280²+0.001 × 280+0.016+0.001 × 350/0.7=0.0627+0.280+0.016+0.50= 0.8587; 0.8587 × 203=174.3kg of aluminum particles are added, and 174kg of aluminum particles are added at one time through an overhead bunker; and sampling after 3 minutes, wherein the measured Al content is 342ppm, the deviation between the calculated value of the end point aluminum content and the actual measured value is 8ppm, the components reach the standard, and the aluminum particle waste is not caused.

Example 6: the aluminum adding method for RH vacuum refining ultra-low carbon steel adopts the following specific process.

(1) The produced ultra-low carbon steel is SPHE-3, and the component requirements of the steel are shown in the table 2; the total amount of the furnace molten steel is 205 t; the outbound temperature is required to be 1611-1636 ℃, and the target carbon content is 0.0040%.

(2) Starting RH refining through a jacking system, and vacuumizing until the vacuum degree reaches 2.0 mbar; the thickness of the molten steel slag of the furnace is 105mm, and the C content is measured by sampling to reach 0.0038 percent, so that the target carbon content is reached; the temperature of the molten steel is measured to be 1598 ℃, and the temperature is increased by adding aluminum and blowing oxygen, and is expected to be increased to 1615 ℃. According to the above formula (I)) Calculating by the formula (III): al (Al)_{Heating of}=0.033*205*17=115kg、Q=115*0.88/1.429/0.7=101.2m³(ii) a According to the calculated amount, 115kg of aluminum is added, and the oxygen blowing amount is 101.2m³(ii) a Sampling after 3 minutes, and measuring the temperature to 1614 ℃, wherein the temperature meets the outbound target temperature; the oxygen level was 266ppm and the target aluminum content was 350 ppm. Calculated according to the above formula (II): alt = (8 × 10)^-7)266²+0.001 × 266+0.016+0.001 × 350/0.7=0.0566+0.266+0.016+0.50= 0.8386; 0.8386 x 205=171.9kg of aluminum particles are added, 172kg of aluminum particles are added at one time through an overhead bunker; sampling is carried out after 3 minutes, the measured Al content is 355ppm, the deviation between the calculated value of the end point aluminum content and the actual measured value is 5ppm, the components reach the standard, and the aluminum particle waste is not caused.

Example 7: the aluminum adding method for RH vacuum refining ultra-low carbon steel adopts the following specific process.

(1) The produced ultra-low carbon steel is SPHE-3, and the component requirements of the steel are shown in the table 2; the total amount of the furnace molten steel is 204 t; the outbound temperature is required to be 1611-1636 ℃, and the target carbon content is 0.0040%. .

(2) Starting RH refining through a jacking system, and vacuumizing until the vacuum degree reaches 2.2 mbar; the thickness of the molten steel slag of the furnace is 200mm, and the C content is measured by sampling to reach 0.0036 percent, so that the target carbon content is reached; the temperature of the molten steel at this time was measured to be 1603 ℃ and the temperature was increased by blowing oxygen with aluminum, desirably to 1618 ℃. Calculating according to the formula (I) and the formula (III): al (Al)_{Heating of}=0.033*204*15=101kg、Q=101*0.88/1.429/0.8=77.7m³(ii) a According to the calculated amount, 101kg of aluminum is added, and the oxygen blowing amount is 77.7m³(ii) a Sampling after 3 minutes, and measuring the temperature to 1616 ℃, wherein the temperature meets the outbound target temperature; the oxygen level was 290ppm and the target aluminum content was 350 ppm. Calculated according to the above formula (II): alt = (8 × 10)^-7)290²+0.001 × 290+0.016+0.001 × 350/0.7=0.0673+0.290+0.016+0.5= 0.8733; adding 0.8733 × 204=178.2kg of aluminum particles, and adding 178.2kg of aluminum particles at one time through an overhead bunker; sampling is carried out after 3 minutes, the measured Al content is 345ppm, the deviation between the calculated value of the end point aluminum content and the actual measured value is 5ppm, the components reach the standard, and the aluminum particle waste is not caused.

Example 8: the aluminum adding method for RH vacuum refining ultra-low carbon steel adopts the following specific process.

(1) The produced ultra-low carbon steel is SPHE-3, and the component requirements of the steel are shown in the table 2; the total amount of molten steel in the furnace is 202 t; the outbound temperature is required to be 1611-1636 ℃, and the target carbon content is 0.0040%.

(2) Starting RH refining through a jacking system, and vacuumizing until the vacuum degree reaches 2.5 mbar; the thickness of the molten steel slag of the furnace is 160mm, and the C content is measured by sampling to reach 0.0040 percent, so that the target carbon content is reached; the temperature of the molten steel was 1608 ℃ at this time, and it was necessary to raise the temperature by adding aluminum and blowing oxygen, and it was desired to raise the temperature to 1625 ℃. Calculating according to the formula (I) and the formula (III): al (Al)_{Heating of}=0.033*202*17=113.3kg、Q=113.3*0.88/1.429/0.6=116.3m³(ii) a According to the calculated amount, 113.3kg of aluminum is added, and the oxygen blowing amount is 116.3m³(ii) a Sampling after 3 minutes, and measuring the temperature to 1626 ℃, wherein the temperature meets the outbound target temperature; the oxygen level was 278ppm and the target aluminum content was 350 ppm. Calculated according to the above formula (II): alt = (8 × 10)^-7)278²+0.001 × 278+0.016+0.001 × 350/0.75=0.0618+0.278+0.016+0.4667= 0.8225; adding 202=166.1kg of aluminum particles 0.8225 in need, and adding 166kg of aluminum particles at one time through an overhead bunker; sampling is carried out after 3 minutes, the measured Al content is 353ppm, the deviation between the calculated value of the end point aluminum content and the actual measured value is 3ppm, the components reach the standard, and the aluminum particle waste is not caused.