A method of determining the manganese iron type of ultra-low carbon steel

Abstract

The application discloses a method for determining the type of manganese iron of ultra-low carbon steel, relates to the technical field of ultra-low carbon steel refining, and aims at solving the problem of high cost of manganese iron added in the production of ultra-low carbon steel. According to the oxygen content of the molten steel entering a station, it is determined whether the molten steel can meet the requirement of the target oxygen content after removing the oxygen consumption of decarburization; according to the temperature of the molten steel entering the station, it is determined whether the molten steel can meet the requirement of the target temperature after the temperature change caused by the deoxidization and temperature rise, natural temperature drop and the addition of metal; if both of the two requirements are met, high-carbon manganese iron is added in the early stage of decarburization, and aluminum particles are added after the decarburization to deeply deoxidize the molten steel; if at least one of the two requirements is not met, high-carbon manganese iron cannot be used, and low-carbon alloy is used for alloying after a period of deep deoxidization; the application can determine the type of manganese iron according to the conditions of the molten steel entering the RH, and the high-carbon manganese iron is used for alloying when the specific conditions are met, thereby achieving the effect of significantly reducing the cost.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ultra-low-carbon-steel molten steel refining, in particular to a method for determining the manganese-iron type of ultra-low-carbon steel. BACKGROUND

[0002] Ultra-low-carbon steel is a kind of steel with a carbon content of less than 0.0030% in molten steel, and has excellent deep-drawing performance, and is widely used in the fields of automobile processing and sheet processing. In a steel mill, the ultra-low-carbon steel is produced by adopting a “converter-RH-continuous casting” process path. The RH refining furnace is a kind of high-efficiency refining equipment, and has multiple refining functions such as decarburization, degassing, uniform composition, temperature adjustment and inclusion removal. When the ultra-low-carbon steel is smelted by the RH, the molten steel is first subjected to deep decarburization by using the carbon-oxygen reaction under the vacuum state, and the time consumption of this stage is generally about 12-20 minutes. When it is judged that the carbon content of the molten steel is less than 0.0020%, the decarburization process is ended. Then, aluminum is added to the molten steel for deep deoxidation. After the deoxidation is completed, manganese-iron alloy (such as metallic manganese) with very low carbon content and titanium-iron alloy are added to the molten steel for alloying. After the alloying and a period of circulation, the vacuum is broken.

[0003] The key to smelting the ultra-low-carbon steel by the RH is to control the carbon content of the molten steel and the RH outgoing temperature. At present, it is a common control strategy to improve the decarburization effect in the RH decarburization period and to reduce the alloying carbon in the alloying period. In order to ensure the decarburization effect, the oxygen content of the molten steel at the end of the RH decarburization should not be too low, and it is generally required to be greater than 200 ppm. The heat generated by the oxygen in the deoxidation process can compensate for the temperature of the molten steel. In the RH smelting process, if the oxygen content at the inlet is too high, the oxygen content of the molten steel at the end of the RH decarburization will be too high, and a large amount of inclusions will be generated after the deoxidation, which will deteriorate the quality of the molten steel. If the oxygen content at the inlet is too low, the self-oxygen of the molten steel is insufficient to ensure the decarburization or to compensate for the temperature of the molten steel, and the oxygen should be blown by the RH top lance, so as to finally ensure that the carbon content of the RH and the temperature of the molten steel meet the requirements.

[0004] Manganese is one of the main strengthening elements in steel materials, and the addition of manganese can improve the strength and hardness of the steel. When the ultra-low-carbon steel is smelted by the RH, the manganese alloying is realized by adding manganese-iron alloy. According to the different carbon contents of the manganese-iron alloy, the manganese-iron alloy is divided into high-carbon manganese iron (containing about 7% of carbon), medium-carbon manganese iron (containing about 1.0-1.5% of carbon), low-carbon manganese iron (containing about 0.5% of carbon) and metallic manganese (containing about 0.025% of carbon). Generally speaking, the lower the carbon content, the higher the price. In August 2023, the market prices of the high-carbon manganese iron, the medium-carbon manganese iron, the low-carbon manganese iron and the metallic manganese were 5593 yuan / ton, 7397 yuan / ton, 9215 yuan / ton and 13274 yuan / ton respectively. According to the calculation, for every increase of 0.01% of the manganese content, the cost order of different types of manganese iron is: high-carbon manganese iron < medium-carbon manganese iron < low-carbon manganese iron < metallic manganese.

[0005] Currently, in the metallurgical industry, ultra-low carbon steel production practices require specific ferromanganese types and timing of addition (primarily requiring a very high carbon content) to prevent the addition of ferromanganese from increasing the carbon content of the molten steel. Manganese with a carbon content of no more than 0.03% is generally used and added after deoxidation. Furthermore, with the recent downturn in the steel industry, steel mills are pursuing extreme low costs. Clearly, innovating ultra-low carbon steel smelting processes and replacing expensive ferromanganese with inexpensive ferromanganese alloys is a pressing issue for steelmakers. Summary of the Invention

[0006] The object of the present invention is to provide a method for determining the type of ferromanganese in ultra-low carbon steel, so as to solve the problem of high cost of ferromanganese added in the production of ultra-low carbon steel.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for determining the type of ultra-low carbon ferromanganese steel, comprising the following specific steps:

[0008] According to the addition of high carbon ferromanganese during alloying, the high carbon ferromanganese M required to achieve the target manganese content in molten steel 高碳锰铁 The carbon content in the molten steel is converted into the carbon content in the molten steel [C] 高碳锰铁 , in order to determine the oxygen consumption Q for decarburization 脱碳耗氧 ;

[0009] According to the oxygen content of molten steel entering the station [O] 进站 , judge whether it can meet the target oxygen content Q at the end of decarburization after removing the oxygen consumption of decarburization 脱碳结束目标氧 requirements;

[0010] According to the molten steel inlet temperature T 进站 , judge that after deoxidation and heating T 脱氧升温值 , natural cooling T 自然温降 and the temperature change T caused by adding metal 合金 After that, can the target temperature T of RH treatment be met? 目标 requirements;

[0011] If both requirements are met, high carbon ferromanganese is added in the early stage of decarburization, and aluminum particles are added after decarburization to perform deep deoxidation of the molten steel.

[0012] If at least one of the two does not meet the requirements, high carbon ferromanganese cannot be used, and low carbon alloying should be used after deep deoxidation for a period of time.

[0013] Preferably, after the converter is finished tapping, steel samples are taken from the ladle to analyze the carbon content of the molten steel [C] 进站 , Manganese content [Mn] 进站 Before the RH process begins, the steel entering the station is measured by an oxygen meter. 进站 , oxygen content [O]进站 .

[0014] Preferably, whether the target oxygen content at the end of decarburization meets the requirement is determined by the following calculation: [O] 富余 =[O] 进站 -Q 脱碳耗氧 -Q 脱碳结束目标氧 , calculated [O] 富余 ≥0 is satisfied.

[0015] Preferably, the oxygen consumption for decarburization Q 脱碳耗氧 =([C] 进站 +[C] 高碳锰铁 )×η1, η1 is the decarburization oxygen consumption coefficient, which is related to the vacuum pump and vacuum tank parameters and is between 0.7-1.2 according to the parameters; the target oxygen content Q at the end of decarburization 脱碳结束目标氧 The specific value is determined according to the steel grade requirements.

[0016] Preferably, whether the target temperature at the end of RH treatment meets the requirement is determined by the following calculation: T 富余 =T 目标 +T 合金 +T 自然温降 -T 脱氧升温值 -T 进站 , calculated T 富余 ≤0 is satisfied.

[0017] Preferably, the deoxidation temperature is T 脱氧升温值 =[O] 脱碳结束 ÷η2, where η2 is the deoxidation temperature rise coefficient, [O] 脱碳结束 To end the decarburization process, oxygen content in molten steel is [O] 脱碳结束 =[O] 进站 -Q 脱碳耗氧 ; RH treatment end target temperature T 目标 The specific value is determined according to the ultra-low carbon steel process, and the natural cooling T 自然温降 and the temperature change T caused by adding metal 合金 The values ​​are obtained by calculation or experiment.

[0018] Preferably, the early stage of decarburization refers to 3-6 minutes after RH extraction is started.

[0019] Preferably, the chemical composition of the RH molten steel of the ultra-low carbon steel is, by mass fraction, C≤0.0030%, Si≤0.03%, 0.10%≤Mn≤0.40%, P≤0.050%, S≤0.015%, and 0.020%≤Als≤0.070%.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The method for determining the type of ferromanganese for ultra-low carbon steel has simple and easy operation steps and basically does not change the process. The corresponding ferromanganese alloy type can be selected according to the conditions of molten steel entering RH. Under the premise of meeting the qualified carbon content of molten steel, the cost of RH ferromanganese alloy can be reduced, and the oxygen content of molten steel at the end of decarburization can be reduced, thereby improving the cleanliness of molten steel.

[0022] 2. This method for determining the type of ferromanganese in ultra-low carbon steel utilizes ingenious process design and metallurgical expertise. Taking advantage of the fact that oxygen is a very strong decarburizer under vacuum conditions and has a good decarburization effect, when the oxygen content of certain heats of molten steel is high when entering RH, oxygen can be used to remove the carbon introduced by high-carbon ferromanganese during decarburization. This allows high-carbon ferromanganese to replace metallic manganese without affecting the control of carbon content at the RH endpoint, thus achieving the goal of using high-carbon ferromanganese for manganese alloying in ultra-low carbon steel and achieving a significant cost reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the judgment logic of the present invention. DETAILED DESCRIPTION

[0024] See Figure 1 , a method for determining the type of ultra-low carbon ferromanganese steel, comprising the following specific steps:

[0025] According to the addition of high carbon ferromanganese during alloying, the high carbon ferromanganese M required to achieve the target manganese content in molten steel 高碳锰铁 The carbon content in the molten steel is converted into the carbon content in the molten steel [C] 高碳锰铁 , in order to determine the oxygen consumption Q for decarburization 脱碳耗氧 ;

[0026] First: According to the oxygen content of molten steel entering the station [O] 进站 , judge whether it can meet the target oxygen content Q at the end of decarburization after removing the oxygen consumption of decarburization 脱碳结束目标氧 requirements;

[0027] The specific calculation can be determined as follows: 富余 =[O] 进站 -Q 脱碳耗氧 -Q 脱碳结束目标氧 , calculated [O] 富余 ≥0 is satisfied; for reference, the oxygen consumption of decarburization Q 脱碳耗氧 =([C] 进站 +[C] 高碳锰铁 )×η1, η1 is the decarburization oxygen consumption coefficient, which is related to the vacuum pump and vacuum tank parameters, and is generally between 0.7-1.2 according to the parameters; the target oxygen content Q at the end of decarburization 脱碳结束目标氧 The specific value is determined according to the steel grade requirements.

[0028] Second: According to the molten steel inlet temperature T 进站 , judge that after deoxidation and heating T 脱氧升温值 , natural cooling T 自然温降 and the temperature change T caused by adding metal 合金 After that, can the target temperature T of RH treatment be met? 目标 requirements;

[0029] The specific calculation can be determined as follows: T 富余 =T 目标 +T 合金 +T 自然温降 -T 脱氧升温值 -T 进站 , calculated T 富余 ≤0 is satisfied. For reference, the deoxidation temperature T 脱氧升温值 =[O] 脱碳结束 ÷η2, where η2 is the deoxidation temperature rise coefficient (oxygen and aluminum can produce a chemical reaction. 100ppm of oxygen is removed by aluminum particles. The heat released causes the temperature of the molten steel to rise by 4 degrees. Therefore, the coefficient η2 is 25). 脱碳结束 To end the decarburization process, oxygen content in molten steel is [O] 脱碳结束 =[O] 进站 -Q 脱碳耗氧 ; RH treatment end target temperature T 目标 The specific value is determined according to the ultra-low carbon steel process, and the natural cooling T 自然温降 and the temperature change T caused by adding metal 合金 The values ​​are obtained by calculation or experiment.

[0030] If both of the above requirements are met, high carbon ferromanganese is added in the early stage of decarburization (generally 3-6 minutes after RH pumping is started), and aluminum particles are added after decarburization to perform deep deoxidation of the molten steel;

[0031] If at least one of the above two items does not meet the requirements, high carbon ferromanganese cannot be used. After deep deoxidation for a period of time, low carbon alloying should be used (such as metallic manganese with low carbon content, electrolytic manganese, etc. The alloying at this time is a general process, so it will not be described in detail).

[0032] As is known, after the steel is tapped from the converter, a steel sample is taken from the ladle to analyze the carbon content of the molten steel. 进站 , Manganese content [Mn] 进站 Before the RH process begins, the steel entering the station is measured by an oxygen meter. 进站 , oxygen content [O] 进站 .

[0033] The ultra-low carbon steel process mainly targeted by the present invention meets the following conditions: the chemical composition of the RH outgoing molten steel is calculated by mass fraction: C≤0.0030%, Si≤0.03%, 0.10%≤Mn≤0.40%, P≤0.050%, S≤0.015%, 0.020%≤Als≤0.070%.

[0034] In order to further illustrate the content of the present invention, the present invention will be further described below by taking the smelting of IF steel in a 300TRH refining furnace as an example.

[0035] Example 1:

[0036] The IF steel grade of RH smelting is: DC06, and the composition requirements of RH air-breaking molten steel are:

[0037]

[0038] Molten steel volume: 308 tons;

[0039] This embodiment is implemented through the following steps:

[0040] Step 1: After the converter is finished tapping, take a steel sample from the ladle and analyze the carbon content of the molten steel [C] 进站 320ppm, manganese content [Mn] 进站 0.05%;

[0041] Step 2: Before the RH process begins, the molten steel is measured by an oxygen meter to measure the molten steel inlet temperature T 进站 1624℃, oxygen content [O] 进站 715ppm;

[0042] Step 3: Calculate the weight of high carbon ferromanganese M required to achieve the target manganese content of 0.14% in molten steel 高碳锰铁 According to metallurgical expertise, 411 kg of high carbon ferromanganese is required. The carbon content of 411 kg of high carbon manganese is converted to the carbon content of molten steel [C]. 高碳锰铁 93ppm;

[0043] Step 4: Determine the type of ferromanganese alloy:

[0044] 1. Consider the oxygen content [O] 进站 Is decarbonization sufficient?

[0045] 1.1. Calculation of decarbonization oxygen consumption Q 脱碳耗氧 :Q 脱碳耗氧 =(320+93)×0.9=372ppm, where 0.9 is the decarburization oxygen consumption coefficient;

[0046] 1.2. Determine the target oxygen content Q at the end of decarburization according to the steel grade requirements 脱碳结束目标氧 250ppm;

[0047] 1.3.[O] 富余 =[O] 进站 -Q 脱碳耗氧 -Q 脱碳结束目标氧 = 715 - 372 - 250 = 93 ppm;

[0048] 2. Consider the temperature of molten steel into the station T 进站 Whether enough to hit the RH broken empty temperature:

[0049] 2.1. According to the steel grade DC06 and the pouring sequence, determine the target temperature T 目标 of RH treatment is 1580℃;

[0050] 2.2. The natural temperature drop T 自然温降 of DC06 steel during RH treatment is considered as 30℃;

[0051] 2.3. According to the metallurgical knowledge, the change of molten steel temperature T 合金 caused by adding high-carbon ferromanganese and ferrotitanium in this furnace is 5℃;

[0052] 2.4. Calculate the oxygen content of molten steel at the end of decarburization [O] 脱碳结束 , [O] 脱碳结束 = [O] 进站 - Q 脱碳耗氧

[0053] = 715 - 372 = 343 ppm;

[0054] 2.5. Calculate the temperature rise value of molten steel after removing the oxygen content at the end of decarburization, T 脱氧升温值 = [O] 脱碳结束 ÷ η

[0055] 2 = 343 / 25 = 14℃, where 25 is the deoxidization temperature rise coefficient;

[0056] 2.6. Calculate the temperature surplus T 富余 = T 目标 + T 合金 + T 自然温降 - T 脱氧升温值 - T 进站

[0057] = 1580 + 5 + 30 - 14 - 1624 = -23℃

[0058] 3. Since [O] surplus = 93 ≥ 0 and T surplus = -23 ≤ 0 are met at the same time, high-carbon ferromanganese is added.

[0059] Step 5: If the type of ferromanganese is high-carbon ferromanganese according to step 3, add high-carbon ferromanganese 411 kg at the early stage of decarburization (RH is opened for 4 minutes);

[0060] Step 6: After decarburization, aluminum particles are added to perform deep deoxidation of the molten steel;

[0061] Step 7: After adding aluminum pellets for a while, add 287kg of ferrotitanium;

[0062] Step 8: After titanium iron is added, the molten steel circulates for a period of time to break the air.

[0063] Comparative Example 1:

[0064] The IF steel grade smelted by RH is: DC06, and the amount of molten steel is: 301 tons;

[0065] After the converter tapping is completed, steel samples are taken from the ladle. The carbon content [C] of the molten steel entering the station is 295ppm, and the manganese content [Mn] entering the station is 0.05%;

[0066] Before the RH process begins, the steel inlet temperature Tinlet is 1624°C and the oxygen content [O]inlet is 715 ppm as measured by an oxygen meter.

[0067] After decarburization, aluminum particles are added to perform deep deoxidation of the molten steel;

[0068] After a period of time, 272 kg of manganese metal and 287 kg of ferrotitanium were added.

[0069] After metallic manganese and ferrotitanium are added, the molten steel circulates for a period of time.

[0070] Example 2:

[0071] The IF steel grade of RH smelting is: TP121, and the composition requirements of RH air-breaking molten steel are:

[0072]

[0073] Molten steel volume: 304 tons;

[0074] This embodiment is implemented through the following steps:

[0075] Step 1: After the converter is finished tapping, take a steel sample from the ladle and analyze the carbon content of the molten steel [C] 进站 276ppm, manganese content [Mn] 进站 0.04%;

[0076] Step 2: Before the RH process begins, the molten steel is measured by an oxygen meter to measure the molten steel inlet temperature T 进站 1615℃, oxygen content [O] 进站 532ppm;

[0077] Step 3: Calculate the weight of high carbon ferromanganese M required to achieve the target manganese content of 0.22% in molten steel 高碳锰铁According to the metallurgical knowledge, 811 kg of high-carbon ferromanganese needs to be added. The weight of carbon in 811 kg of high-carbon ferromanganese is converted into the carbon content [C] of the molten steel 高碳锰铁 187 ppm;

[0078] Fourth step: Determine the type of ferromanganese alloy:

[0079] 1. Consider the oxygen content [O] of the incoming station 进站 whether it is sufficient to decarburize:

[0080] 1.1. Calculate the oxygen consumption Q for decarburization 脱碳耗氧 : Q 脱碳耗氧 = (276 + 187) x 0.9 = 417 ppm, where 0.9 is the oxygen consumption coefficient for decarburization;

[0081] 1.2. According to the requirements of the steel grade, determine the target oxygen content Q for decarburization end 脱碳结束目标氧 280 ppm;

[0082] 1.3. [O] 富余 = [O] 进站 - Q 脱碳耗氧 - Q 脱碳结束目标氧 = 532 - 417 - 280 = -165 ppm;

[0083] 2. Since the [O] surplus = -165 < 0, it does not meet the condition of adding high-carbon manganese, so add metallic manganese;

[0084] Sixth step: After decarburization, add aluminum particles to deeply deoxidize the molten steel;

[0085] Seventh step: After a period of time after adding aluminum particles, add 582 kg of metallic manganese, 152 kg of niobium iron, and 212 kg of titanium iron;

[0086] Eighth step: After adding metallic manganese, niobium iron, and titanium iron, the molten steel is recirculated for a period of time to break the vacuum.

[0087] Comparative Example 2:

[0088] The RH smelted IF steel grade is TP121, and the molten steel quantity is 311 tons;

[0089] After the converter tapping ends, take a steel sample in the ladle, and analyze the molten steel carbon content [C] of 317 ppm and the manganese content [Mn] of 0.07% at the incoming station;

[0090] Before the molten steel starts processing in the RH process, the incoming station temperature T 进站 is measured by an oxygen meter to be 1617°C, and the oxygen content [O] 进站 is 498 ppm;

[0091] After decarburization, aluminum particles are added for deep deoxidization of the molten steel;

[0092] Al particle is added for a period of time, and then metal manganese 221 kg, ferro-niobium 158 kg, and ferro-titanium 204 kg are added;

[0093] After the metal manganese, ferro-niobium, and ferro-titanium are added, the molten steel is circulated for a period of time to break the vacuum.

[0094] The main indicators of the RH in the examples are as follows:

[0095] Table 1 Main indicators of the RH in examples 1 and 2

[0096]

[0097] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical scope disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be defined by the protection scope of the claims.

[0098] The details not described in the present application are the known technology of the person skilled in the art.

Claims

1. A method for determining the type of ultra-low carbon ferromanganese steel, characterized in that: The specific steps include: According to the addition of high carbon ferromanganese during alloying, the high carbon ferromanganese M required to achieve the target manganese content in molten steel 高碳锰铁 The carbon content in the steel is converted into the carbon content in the molten steel [C] 高碳锰铁 , in order to determine the oxygen consumption Q for decarburization 脱碳耗氧 ; According to the oxygen content of molten steel entering the station [O] 进站 , judge whether it can meet the target oxygen content Q at the end of decarburization after removing the oxygen consumption of decarburization 脱碳结束目标氧 requirements; According to the molten steel inlet temperature T 进站 , judge that after deoxidation and heating T 脱氧升温值 , natural cooling T 自然温降 and the temperature change T caused by adding metal 合金 After that, can the target temperature T of RH treatment be met? 目标 requirements; If both requirements are met, high carbon ferromanganese is added in the early stage of decarburization, and aluminum particles are added after decarburization to perform deep deoxidation of the molten steel. If at least one of the two requirements is not met, high carbon ferromanganese cannot be used and low carbon alloying should be used after deep deoxidation for a period of time; Whether the target oxygen content at the end of decarburization meets the requirement is determined by the following calculation: [O] 富余 =[O] 进站 -Q 脱碳耗氧 -Q 脱碳结束目标氧 , calculated [O] 富余 ≥0 is satisfied; The oxygen consumption Q of the decarburization 脱碳耗氧 =([C] 进站 +[C] 高碳锰铁 )×η1, η1 is the decarburization oxygen consumption coefficient, which is related to the vacuum pump and vacuum tank parameters and is between 0.7-1.2 according to the parameters; the target oxygen content Q at the end of decarburization 脱碳结束目标氧 The specific value is determined according to the steel grade requirements; The determination of whether the target temperature after the RH treatment meets the requirements is determined by the following calculation: T 富余 =T 目标 +T 合金 +T 自然温降 -T 脱氧升温值 -T 进站 , calculated T 富余 ≤0 is satisfied; The deoxidation temperature T 脱氧升温值 =[O] 脱碳结束 ÷η2, where η2 is the deoxidation temperature rise coefficient, [O] 脱碳结束 To end the decarburization process, oxygen content in molten steel is [O] 脱碳结束 =[O] 进站 -Q 脱碳耗氧 ; RH treatment end target temperature T 目标 The specific value is determined according to the ultra-low carbon steel process, and the natural cooling T 自然温降 and the temperature change T caused by adding metal 合金 The values ​​are obtained by calculation or experiment.

2. The method for determining the type of ultra-low carbon ferromanganese steel according to claim 1, wherein: After the converter is finished tapping, take a steel sample from the ladle and analyze the carbon content of the molten steel [C] 进站 , Manganese content [Mn] 进站 Before the RH process begins, the steel entering the station is measured by an oxygen meter. 进站 , oxygen content [O] 进站 .

3. The method for determining the type of ultra-low carbon ferromanganese steel according to claim 1, wherein: The early stage of decarburization refers to 3-6 minutes after RH pumping is started.

4. A method for determining the type of ultra-low carbon ferromanganese steel according to any one of claims 1 to 3, characterized in that: The chemical composition of the RH molten steel out of the ultra-low carbon steel is, by mass fraction, C≤0.0030%, Si≤0.03%, 0.10%≤Mn≤0.40%, P≤0.050%, S≤0.015%, 0.020%≤Als≤0.070%.

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