Method for controlling molten steel temperature through LF electrode heating

Abstract

The invention relates to a method for controlling the temperature of molten steel through LF electrode heating. The method comprises the following steps that firstly, data are obtained, secondly, the initial temperature of the molten steel is measured through a temperature measuring probe, and thirdly, the temperature change of the molten steel caused by material input is calculated; (4) calculating the natural temperature drop temperature of the molten steel; (5) calculating the time required by feeding; (6) calculating the time required by wire feeding; (7) calculating the temperature drop change of the molten steel by bottom blowing; according to the method, by reasonably calculating the LF electrode heating time, the temperature reaching rate of primary heating of the LF electrode is effectively increased, and therefore the LF treatment period is shortened; meanwhile, power consumption in the production process is reduced, and the effect is remarkable.

Description

Technical Field

[0001] The invention relates to a method, in particular to a method for controlling the temperature of molten steel by heating with LF electrodes, and belongs to the technical field of production and control of metallurgical processes. Background Art

[0002] LF refining furnace is a refining equipment for heating and controlling the composition of molten steel. Its main functions are heating, desulfurization and adjustment of various elements in molten steel to make the molten steel meet the standard requirements of this steel grade. Therefore, in the production process, in order to make the molten steel reach the target temperature when it leaves the station, the temperature of the molten steel needs to be heated. The main means for LF to increase the temperature of molten steel is electrode heating. The electrode consists of three graphite electrodes. By energizing the three electrodes with large resistance, the electrodes generate a lot of heat. Since the electrodes are inserted into the molten steel during heating, the heat generated by the electrodes is transferred to the molten steel, so that the temperature of the molten steel is increased. In this process, the operator needs to consider the heating efficiency of each heating gear of the electrode, the target temperature to be achieved, the natural temperature drop coefficient of the molten steel, and the intensity of the bottom blowing, and comprehensively consider the setting value of the electrode heating gear and heating time. After the setting is completed, the electrode is energized for heating. When the heating time reaches the set value, the heating automatically stops and the electrode heating is completed. However, in the actual electrode heating process, if the setting gear and time are inaccurate, it may cause the molten steel temperature to be insufficient and multiple heating to occur, or the molten steel temperature to be too high and increase the power consumption, thereby increasing the cost.

[0003] At present, most of the industry uses the operator's experience to operate the electrode for heating. Some factories also use a fixed calculation formula to first calculate the target temperature of the molten steel, and then the operator sets the heating time and gear of the electrode according to the target temperature. However, there are generally few conditions considered, and various conditions are not fully considered for optimization calculation. There is room for improvement in this method.

[0004] In recent years, some domestic steel mills have carried out research on various methods of controlling molten steel temperature by electrode heating. The following 5 patents are involved in this research field:

[0005] 1. A method for reducing the power consumption of an LF furnace, patent number: CN201510791249.3. The present invention provides a method for reducing the power consumption of an LF furnace. After the molten steel tank enters the LF furnace, calcium carbide is added at 0.2-0.5 kg / ton of steel, and the fluxing slag is first added at a ratio of lime: fluxing slag = 4:1, and then lime is added. The amount of lime added is controlled at 7-10 kg / ton of steel; the temperature is raised after stirring for 55-65 seconds with a large amount of argon gas of 85-90 Nm3 / h; the temperature is raised in a low gear for slagging in the first 10 minutes of heating, and then the temperature is raised in a medium-high gear; and the heating time is accurately calculated according to the temperature drop of the large tank and the time information of the upper continuous casting machine to avoid secondary heating at low temperature or the probability of adding scrap steel to reduce the temperature at high temperature. The present invention can not only reduce the power consumption of the LF furnace, but also reduce the noise on site, increase the life of the graphite electrode, and reduce the amount used. After the implementation of the present invention, the power consumption of the LF furnace is 27.48 kWh / t steel, which is 7.06% lower than the same period last year, thereby greatly reducing the smelting cost. A method for reducing the power consumption of the LF furnace, characterized in that: (1) after the molten steel tank enters the LF furnace, calcium carbide is added at a rate of 0.2-0.5 kg / ton steel, and the fluxing slag is first added at a ratio of lime: fluxing slag = 4:1, and then lime is added, and the amount of lime added is controlled to be 7-10 kg / ton steel; (2) the LF furnace is heated after stirring for 55-65 seconds with a large amount of argon gas of 85-90 Nm3 / h; (3) within the first 10 minutes of heating, a low gear is used for heating and slagging, and then a medium-high gear is used for heating; (4) during the heating process, slag is added in batches at a rate of 0.46-0.5 kg / ton steel of lime and 1.8-2 kg / ton steel of fluxing slag, and the total amount of lime added is not less than 6.9 kg / ton steel; at the top When the slag is sticky or the initial sulfur is high, the amount of lime added should not be less than 9.6 kg / ton of steel; (5) According to the temperature drop of the large tank and the time information of the continuous casting machine, the heating time is accurately calculated to avoid secondary heating at low temperature or adding scrap steel to cool down at high temperature; the target heating time T is calculated as follows: T = (t1 + T1 × η1-t2 + t3 + ΔT) ÷ η2t1: target temperature of the continuous casting machine, calculated according to the liquidus temperature of the steel grade; T1: planned time interval for the continuous casting machine; η1: temperature drop loss, 0.9~1℃ / min; t2: current molten steel temperature; t3: temperature drop after adding material, 7℃ / t; ΔT: temperature drop of the large tank, A and B grade tanks add 10℃; η2: heating efficiency, 4.5℃ / min. In this patent, a fixed temperature drop value is used for the temperature drop loss, temperature drop after adding materials, etc. However, in the actual production process, as the number of times the ladle is used increases, the temperature drop loss will increase. In addition, various materials have different effects on the temperature of the molten steel. Therefore, it is not appropriate to use a fixed value to participate in the calculation of the molten steel temperature.

[0006] 2. A double-station LF furnace molten steel temperature prediction control system, patent number: CN200910087529.0. A double-station LF furnace molten steel temperature prediction control system, belonging to the field of LF furnace automatic control technology. The system includes hardware and software processing modules for online detection and prediction control; the characteristics are that the hardware includes a temperature measuring thermocouple, which is connected to the LF furnace production process database through Ethernet; the software processing module includes a data acquisition module, a double-station processing module, a temperature correction module, a molten steel temperature prediction module, a parameter self-learning module, a molten steel temperature control module, and a historical data query module. The advantages are that the prediction is accurate, reliable and practical, and the automation level is high. Although this patented method takes into account the influence of bottom blowing argon on molten steel, and sets the temperature drop coefficient according to the slag thickness and bottom blowing intensity; however, it does not take into account the intensity changes and duration of each bottom blowing intensity in different processing processes during the production process, and the strength of the bottom blowing has a greater impact on the molten steel.

[0007] 3. A system and method for online control of molten steel temperature in LF refining process, patent number: CN201310306019.4. A system and method for online control of molten steel temperature in LF refining process, belonging to the field of production and control technology of metallurgical process, the system: includes information acquisition module, heating judgment module, electrode heating and temperature rise module, ladle lining heat dissipation module, alloy addition judgment module, alloy thermal effect module, slag addition judgment module, slag thermal effect module, argon gas blowing slag layer judgment module, molten steel radiation heat dissipation module, argon gas heat absorption module, slag layer heat dissipation module, temperature calculation module, temperature correction judgment module, temperature correction module, temperature prediction module, temperature control module. Method: Online control of molten steel temperature in LF refining process is to obtain the real-time temperature of molten steel after calculating the temperature change of molten steel caused by heating and heat dissipation and cooling process of LF refining process, and control the heating process by adjusting the heating time, so that the real-time temperature of molten steel reaches the target temperature of molten steel, and is controlled within the control accuracy range allowed by LF refining site. This patent does not involve the calculation of the electrode heating time, which is different from the calculation results of this patent.

[0008] 4. Real-time measurement and reporting method of molten steel temperature in LF refining furnace, patent number: CN201010199979.1. The present invention relates to a real-time measurement and reporting method of molten steel temperature in LF refining furnace, belonging to the technical field of molten steel temperature measurement in LF refining furnace. The method uses the existing LF refining furnace calculation system to read the weight of molten steel and the existing parameters during the furnace processing, and regularly measures the measured temperature of the molten steel. At the beginning of the furnace processing, the natural temperature drop coefficient of the molten steel is first calculated in real time, and then the calculated temperature of the molten steel in the non-temperature measurement time period is calculated in real time according to the set interval time; or after the second temperature measurement, the natural temperature drop compensation coefficient of the molten steel is first calculated, and then the calculated temperature at each temperature measurement time is calculated in real time, and the calculated temperature and the measured temperature in the non-temperature measurement time period or the calculated temperature before each temperature measurement are respectively used as the real-time measurement and reporting molten steel temperature and output to the existing LF refining furnace calculation system. Because the method dynamically calculates the natural temperature drop coefficient, and further introduces the natural temperature drop compensation coefficient to compensate for the deviation of the natural temperature drop coefficient of the molten steel, a more accurate real-time molten steel temperature can be obtained compared with the prior art. This patent does not involve the calculation of the electrode heating time, which is different from the calculation results of this patent.

[0009] 5. LF-RH process molten steel temperature pre-control device and method, patent number: CN201710349737.8. The present invention relates to a LF-RH process molten steel temperature pre-control device, characterized in that the pre-control device includes a data collection module, a continuous casting temperature calculation module, a molten steel natural temperature drop calculation module, an RH decarburization temperature rise calculation module, an RH degassing temperature drop calculation module, an RH aluminum deoxidation temperature rise calculation module, an LF electrode temperature rise calculation module, and a scrap steel temperature drop calculation module; the scheme predicts the molten steel temperature in real time by tracking various events and related data in the RH smelting process, realizes online temperature calculation or temperature prediction, and accurately controls the RH molten steel temperature. The scope of this patent is different from that of this patent, and the patent does not involve the calculation of electrode heating time, and it has not been issued to L1 for execution.

[0010] The control methods described in the above five patents: The first two patents have the problem of using a fixed temperature drop value to participate in the calculation of the molten steel temperature and insufficient consideration of the factors affecting the molten steel temperature. The methods in the last three patents are different from the scope of this patent or do not involve the calculation of the electrode heating time. Summary of the invention

[0011] The present invention aims at the problems existing in the prior art and provides a method for controlling the temperature of molten steel by heating LF electrodes. In the whole electrode heating process, the technical solution is very important for controlling the gear and time of electrode heating. The present invention can accurately control the gear and time of electrode heating, thereby shortening the LF production time, reducing the power consumption of electrode heating, and improving the automation control level of LF electrode heating.

[0012] In order to achieve the above object, the technical solution of the present invention is as follows: a method for controlling the temperature of molten steel by heating with LF electrodes, characterized in that the method comprises the following steps:

[0013] Step 1: Obtain data. Obtain the type and weight of materials required for the molten steel in this furnace from the LF alloy model (including the type and length of wire feeding, as well as the batch information of material feeding and wire feeding). These data are calculated by the alloy model at the beginning of the furnace. Obtain data such as the weight of the molten steel in the current processing furnace, the target temperature of the molten steel, and the planned end time of LF processing through the secondary process control system.

[0014] Step 2: Use the temperature probe to measure the initial temperature of the molten steel. After the furnace enters the station, use the temperature probe to measure the temperature of the molten steel to obtain the initial temperature of the molten steel (denoted as: T 初始 )

[0015] Step 3: Calculate the temperature change of molten steel caused by the input materials. The calculation results of the alloy model were obtained in step 1, including the type and weight of the required input materials (the weight of the materials is recorded as: W i , the wire feeding length is recorded as: L i ), this step mainly calculates the change of molten steel temperature after these materials are put into molten steel (the temperature drop after each material is put into molten steel is recorded as: T i ), where the temperature variation coefficient of each material is: The density of each thread is: α i .

[0016] Calculation method for converting wire feeding length into weight:

[0017] W i =L i ×α i ………(1)

[0018] Calculation method for the change in molten steel temperature caused by adding each material:

[0019]

[0020] Calculation method for temperature change of molten steel caused by inputting all materials:

[0021] T 物料 =T1+T2+...+T i ………(3)

[0022] Where: T 物料 : The temperature change of molten steel after all materials are put in (unit: °C); if it is a negative value, the temperature of molten steel decreases, if it is a positive value, the temperature of molten steel increases;

[0023] Step 4: Calculate the natural temperature drop of the molten steel. That is, the initial temperature of the molten steel is measured by the temperature probe (denoted as: M 测温时刻 ), to the planned furnace exit time (denoted as: M 出站时刻 ), the heat of the molten steel diffuses outward through the ladle, causing the temperature of the molten steel to drop (denoted as: T 自然温降 ).

[0024] Calculation method for temperature drop of molten steel from the time when the initial temperature is measured to the time when the planned heat is finished:

[0025] T 自然温降 =W 钢水重量 ×(M 出站时刻 -M 测温时刻 )×λ 自然温降系数 ..(4)

[0026] in:

[0027] λ 自然温降系数 : Natural temperature drop coefficient of molten steel (unit: ℃ / t / min).

[0028] W 钢水重量 : The total weight of molten steel (unit: t).

[0029] Step 5: Calculate the time required for feeding. That is, the time interval from the start of feeding to the completion of feeding, and the length of time is determined by the total weight of all materials required to be fed (recorded as: W 总重量 ) and the feeding speed of the feeding hopper (denoted as: V 下料速度 )Decide.

[0030] Calculation method for feeding time of all materials:

[0031] S 投料时间 =W 总重量 ÷V 下料速度 ………(5)

[0032] in:

[0033] S 投料时间 : The time required to put in all materials (unit: min).

[0034] Step 6: Calculate the time required for wire feeding. That is, the time interval from the start of wire feeding to the end of wire feeding, and the length of time is determined by the length of all wires to be fed (recorded as: L 喂丝长度 ) and the speed of the wire feeder (denoted as: V 喂丝速度 )Decide.

[0035] Calculation method for feeding time of all materials:

[0036] S 喂丝时间 =L 喂丝长度 ÷V 喂丝速度………(6)

[0037] in:

[0038] S 喂丝时间 : Time required for wire feeding (unit: min).

[0039] Step 7: Calculate the change of temperature drop of molten steel due to bottom blowing. There are three bottom blowing methods in the whole LF treatment process, one is weak bottom blowing, one is strong bottom blowing, and the other is standard bottom blowing between weak blowing and strong blowing; the three bottom blowing methods are generally divided by the flow range of bottom blowing. Weak bottom blowing is used during the feeding, wire feeding and electrode heating process in the production process; strong bottom blowing is used for a certain time (recorded as: S) after the feeding, wire feeding and heating are completed. 设定 , generally set to 3 minutes) to achieve uniform molten steel composition and molten steel temperature. After each batch of materials is added, each batch of wire is fed, and each heating is completed, S 设定 The strong bottom blowing of the time; the standard bottom blowing is used during the other processing times. 批次次数 , unit: times), provided by the alloy model calculation results.

[0040] Calculation method of bottom blowing time for weak bottom blowing flow:

[0041] S 弱 =S 投料时间 +S 喂丝时间 +S 加热时间 ......(7)

[0042] Calculation method of bottom blowing time for strong bottom blowing flow:

[0043] S 强 =(N 批次次数 +N 加热次数 )×S 设定 ......(8)

[0044] Calculation method of bottom blowing time for standard bottom blowing flow rate:

[0045] S 标准 =S 剩余 -S 弱 -S 强 ......(9)

[0046] Calculation method for temperature drop of molten steel caused by bottom blowing during the whole treatment process:

[0047] T 底吹温降 =S 强 ×β 强温降 +S 弱 ×β 弱温降 +S 标准 ×β 标准温降..(10)

[0048] in:

[0049] S 投料时间 : The time required to put in all materials (unit: min);

[0050] S 喂丝时间 : The time required for wire feeding (unit: min);

[0051] S 加热时间 : Electrode heating time (unit: min);

[0052] S 弱 : Weak bottom blowing time (unit: min);

[0053] S 强 : Strong bottom blowing time (unit: min);

[0054] S 标准 : Standard bottom blowing time (unit: min);

[0055] S 剩余 : Remaining treatment time of molten steel (unit: min);

[0056] β 弱温降 : Temperature drop coefficient of molten steel under weak bottom blowing (unit: ℃ / min);

[0057] β 强温降 : Temperature drop coefficient of molten steel under strong bottom blowing (unit: ℃ / min).

[0058] β 标准温降 : Temperature drop coefficient of molten steel under standard bottom blowing (unit: ℃ / min);

[0059] T 底吹温降 :Temperature drop of molten steel caused by bottom blowing (unit: ℃)

[0060] Step 8: Calculate the time setting value for electrode heating.

[0061] In order to make the molten steel temperature reach the set target temperature when it leaves the station; first, predict the molten steel temperature when it leaves the station:

[0062] T 出站 =T 初始 -T 底吹温降 -T 物料 -T 自然温降 ..(10)

[0063] in:

[0064] T 物料 : The temperature change of molten steel after all materials are put into the furnace (unit: °C);

[0065] T 自然温降 : The temperature drop of the molten steel caused by the heat diffusion from the molten steel through the ladle (unit: °C);

[0066] T 底吹温降 : Temperature drop of molten steel caused by bottom blowing (unit: °C);

[0067] T 初始 : Initial temperature measured by the temperature probe (unit: °C);

[0068] T 出站 : The predicted temperature when the furnace is finished as planned (unit: °C).

[0069] Secondly, compare T 出站 and T 目标 , and perform corresponding processing according to the comparison situation:

[0070] 1) When T 出站 <T 目标 When: It means that at the end of the furnace, the predicted exit temperature is not enough and electrode heating is required.

[0071] To increase the temperature of the molten steel; in order to calculate the electrode heating time, it is necessary to introduce the electrothermal conversion coefficient (denoted as: λ 电热 , unit: kwh / t / ℃) and electrode heating efficiency coefficient (denoted as: μ 加热效率 , unit: kwh / min); these two coefficients are system parameters of the LF electrode heating system, provided by the electrode manufacturer. Regarding the electrode heating efficiency, each heating gear in the electrode heating system has a heating efficiency coefficient for that gear. In the process of calculating the heating time, the heating efficiency coefficient is selected according to the gear set by the current heating system; when the gear changes, the heating time will be recalculated.

[0072] Calculate the time for electrode heating:

[0073] S 加热时间 =W 钢水重量 ×(T 目标 -T 出站 )×λ 电热 ÷μ 加热效率 .(11)

[0074] in:

[0075] T 目标 : The target temperature of the molten steel obtained from the secondary process control system in step 1 (unit: °C);

[0076] T 出站 : The predicted temperature when the furnace leaves the station as planned (unit: ℃).

[0077] W钢水重量 : The total weight of molten steel (unit: t).

[0078] λ 电热 : Electric heat conversion coefficient (unit: kwh / t / ℃);

[0079] μ 加热效率 : Electrode heating efficiency coefficient (unit: kwh / min);

[0080] S 加热时间 : Electrode heating time (unit: min);

[0081] 2) When T 结束 =T 目标 When: It means that at the end of the furnace, the predicted outlet temperature is equal to the target temperature and electrode heating is not required.

[0082] 3) When T 结束 >T 目标 Time: It means that at the end of the furnace, the predicted outlet temperature is greater than the target temperature, and it is necessary to increase the time of strong bottom blowing to lower the molten steel temperature so that the outlet temperature is equal to the target temperature. In this case, electrode heating is not required.

[0083] Step 9: Send the electrode heating time and gear to L1 to control the electrode heating. In general, except for the low gear heating when melting slag, in order to reduce the LF processing cycle, the highest gear is used for rapid heating; after completing the calculation of the electrode heating time, the calculated S 加热时间 The heating gear is sent to the corresponding electrode heating setting value of the first-level system, and a heating start instruction is sent to the first-level system. The first-level system executes the heating task based on the set heating time, and ends the heating task when the heating time is reached.

[0084] The above 9 steps describe in detail the method of the present invention for controlling the temperature of molten steel by heating the LF electrode. The control method fully considers the influence of factors such as wire feeding, material feeding, bottom blowing, heating, and natural temperature drop on the molten steel temperature during the LF production process, and calculates the heating time of the LF electrode through a reasonable method. Finally, the heating time setting value is calculated to control the electrode heating, thereby ensuring that the molten steel temperature reaches the target temperature when it is planned to leave the station, and ultimately reducing the production cost of LF.

[0085] Compared with the prior art, the present invention has the following advantages: a method for controlling the temperature of molten steel by heating LF electrodes of the present invention comprehensively considers the temperature changes in the entire LF production process, and calculates the impact of each treatment process on the molten steel in advance, obtains the time setting value of electrode heating by calculation before heating the molten steel, and sends it to the first level for electrode heating control, so that the outlet temperature of the molten steel is basically consistent with the target temperature within a very small deviation range, and also avoids the problem of increased power consumption caused by repeated electrode heating; after using this method to participate in LF electrode heating control, the over-target temperature of LF is reduced from the original 1.8°C to 1°C, thereby effectively reducing power consumption and other production costs in the LF production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 LF pole heating control molten steel temperature flow chart. DETAILED DESCRIPTION

[0087] In order to deepen the understanding of the present invention, the present embodiment is described in detail below with reference to the accompanying drawings.

[0088] Example 1: See Figure 1 A method for controlling the temperature of molten steel by heating an LF electrode in this embodiment comprises the following steps:

[0089] Step 1: Get data. Get the type and weight of materials needed to be put into the molten steel in this furnace from the LF alloy model (including the type and length of wire feeding, as well as the batch information of feeding and wire feeding). These data are calculated by the alloy model at the beginning of the furnace; get the weight of the molten steel in the current furnace, the target temperature of the molten steel, the planned end time of LF processing, etc. through the secondary process control system. (Related data can be found in Implementation Sample Table 1 and Implementation Sample Table 2)

[0090] Implementation example Table 1: Obtaining basic information of LF refining furnace

[0091]

[0092] Implementation example Table 2: LF alloy model calculation results information table

[0093]

[0094] Step 2: Use the temperature probe to measure the initial temperature of the molten steel. After the furnace enters the station, use the temperature probe to measure the temperature of the molten steel to obtain the initial temperature of the molten steel (denoted as: T 初始 )

[0095] Step 3: Calculate the temperature change of molten steel caused by the input materials. The calculation results of the alloy model were obtained in step 1, including the type and weight of the required input materials (the weight of the materials is recorded as: Wi , the wire feeding length is recorded as: L i ), this step mainly calculates the change of molten steel temperature after these materials are put into molten steel (the temperature drop after each material is put into molten steel is recorded as: T i ),

[0096] Among them, the temperature variation coefficient of each material is: The density of each thread is: α i .

[0097] Calculation method for converting wire feeding length into weight:

[0098] W i =L i ×α i ………(1)

[0099] Calculation method for the change in molten steel temperature caused by adding each material:

[0100]

[0101] Calculation method for temperature change of molten steel caused by inputting all materials:

[0102] T 物料 =T1+T2+...+T i ………(3)

[0103] in:

[0104] T 物料 : The temperature change of the molten steel after all materials are put in (unit: ℃); if it is a negative value, the temperature of the molten steel decreases, if it is a positive value, the temperature of the molten steel increases.

[0105] Step 4: Calculate the natural temperature drop of the molten steel. That is, the initial temperature of the molten steel is measured by the temperature probe (recorded as:

[0106] M 测温时刻 ), to the planned furnace exit time (denoted as: M 出站时刻 ), the heat of the molten steel diffuses outward through the ladle, causing the temperature of the molten steel to drop (denoted as: T 自然温降 ).

[0107] Calculation method for temperature drop of molten steel from the time when the initial temperature is measured to the time when the planned heat is finished:

[0108] T 自然温降 =W 钢水重量 ×(M 出站时刻 -M 测温时刻 )×λ 自然温降系数 ..(4)

[0109] in:

[0110] λ自然温降系数 : Natural temperature drop coefficient of molten steel (unit: ℃ / t / min).

[0111] W 钢水重量 : The total weight of molten steel (unit: t).

[0112] Step 5: Calculate the time required for feeding. That is, the time interval from the start of feeding to the completion of feeding, and the length of time is determined by the total weight of all materials required to be fed (recorded as: W 总重量 ) and the feeding speed of the feeding hopper (denoted as: V 下料速度 )Decide.

[0113] Calculation method for feeding time of all materials:

[0114] S 投料时间 =W 总重量 ÷V 下料速度 ………(5)

[0115] in:

[0116] S 投料时间 : The time required to put in all materials (unit: min).

[0117] Step 6: Calculate the time required for wire feeding. That is, the time interval from the start of wire feeding to the end of wire feeding, and the length of time is determined by the length of all wires to be fed (recorded as: L 喂丝长度 ) and the speed of the wire feeder (denoted as: V 喂丝速度 )Decide.

[0118] Calculation method for feeding time of all materials:

[0119] S 喂丝时间 =L 喂丝长度 ÷V 喂丝速度 ………(6)

[0120] in:

[0121] S 喂丝时间 : Time required for wire feeding (unit: min).

[0122] Step 7: Calculate the change of temperature drop of molten steel due to bottom blowing. There are three bottom blowing methods in the whole LF treatment process, one is weak bottom blowing, one is strong bottom blowing, and the other is standard bottom blowing between weak blowing and strong blowing; the three bottom blowing methods are generally divided by the flow range of bottom blowing. Weak bottom blowing is used during the feeding, wire feeding and electrode heating process in the production process; strong bottom blowing is used for a certain time (recorded as: S) after the feeding, wire feeding and heating are completed. 设定 , generally set to 3 minutes) to achieve uniform molten steel composition and molten steel temperature. After each batch of materials is added, each batch of wire is fed, and each heating is completed, S设定 The strong bottom blowing of the time; the standard bottom blowing is used during the other processing times. 批次次数 , unit: times), provided by the alloy model calculation results.

[0123] Calculation method of bottom blowing time for weak bottom blowing flow:

[0124] S 弱 =S 投料时间 +S 喂丝时间 +S 加热时间 ......(7)

[0125] Calculation method of bottom blowing time for strong bottom blowing flow:

[0126] S 强 =(N 批次次数 +N 加热次数 )×S 设定 ......(8)

[0127] Calculation method of bottom blowing time for standard bottom blowing flow rate:

[0128] S 标准 =S 剩余 -S 弱 -S 强 ......(9)

[0129] Calculation method for temperature drop of molten steel caused by bottom blowing during the whole treatment process:

[0130] T 底吹温降 =S 强 ×β 强温降 +S 弱 ×β 弱温降 +S 标准 ×β 标准温降 ..(10)

[0131] in:

[0132] S 投料时间 : The time required to put in all materials (unit: min);

[0133] S 喂丝时间 : The time required for wire feeding (unit: min);

[0134] S 加热时间 : Electrode heating time (unit: min);

[0135] S 弱 : Weak bottom blowing time (unit: min);

[0136] S 强 : Strong bottom blowing time (unit: min);

[0137] S 标准 : Standard bottom blowing time (unit: min);

[0138] S 剩余 : Remaining treatment time of molten steel (unit: min);

[0139] β 弱温降 : Temperature drop coefficient of molten steel under weak bottom blowing (unit: ℃ / min);

[0140] β 强温降 : Temperature drop coefficient of molten steel under strong bottom blowing (unit: ℃ / min).

[0141] β 标准温降 : Temperature drop coefficient of molten steel under standard bottom blowing (unit: ℃ / min);

[0142] T 底吹温降 :Temperature drop of molten steel caused by bottom blowing (unit: ℃)

[0143] Step 8: Calculate the time setting value for electrode heating.

[0144] In order to make the molten steel temperature reach the set target temperature when it leaves the station; first, predict the molten steel temperature when it leaves the station:

[0145] T 出站 =T 初始 -T 底吹温降 -T 物料 -T 自然温降 ..(10)

[0146] in:

[0147] T 物料 : The temperature change of molten steel after all materials are put into the furnace (unit: °C);

[0148] T 自然温降 : The temperature drop of the molten steel caused by the heat diffusion from the molten steel through the ladle (unit: °C);

[0149] T 底吹温降 : Temperature drop of molten steel caused by bottom blowing (unit: °C);

[0150] T 初始 : Initial temperature measured by the temperature probe (unit: °C);

[0151] T 出站 : The predicted temperature when the furnace is finished as planned (unit: °C).

[0152] Secondly, compare T 出站 and T 目标 , and perform corresponding processing according to the comparison situation:

[0153] 1) When T 出站 <T 目标 Time: It means that at the end of the furnace, the predicted outlet temperature is not enough, and electrode heating is required to increase the temperature of the molten steel. In order to calculate the electrode heating time, the electrothermal conversion coefficient (denoted as: λ 电热 , unit: kwh / t / ℃) and electrode heating efficiency coefficient (denoted as: μ 加热效率 , unit: kwh / min); these two coefficients are system parameters of the LF electrode heating system, provided by the electrode manufacturer. Regarding the electrode heating efficiency, each heating gear in the electrode heating system has a heating efficiency coefficient for that gear. In the process of calculating the heating time, the heating efficiency coefficient is selected according to the gear set by the current heating system; when the gear changes, the heating time will be recalculated.

[0154] Calculate the time for electrode heating:

[0155] S 加热时间 =W 钢水重量 ×(T 目标 -T 出站 )×λ 电热 ÷μ 加热效率 .(11)

[0156] in:

[0157] T 目标 : The target temperature of the molten steel obtained from the secondary process control system in step 1 (unit: °C);

[0158] T 出站 : The predicted temperature when the furnace leaves the station as planned (unit: ℃).

[0159] W 钢水重量 : The total weight of molten steel (unit: t).

[0160] λ 电热 : Electric heat conversion coefficient (unit: kwh / t / ℃);

[0161] μ 加热效率 : Electrode heating efficiency coefficient (unit: kwh / min);

[0162] S 加热时间 : Electrode heating time (unit: min);

[0163] 2) When T 结束 =T 目标 When: It means that at the end of the furnace, the predicted outlet temperature is equal to the target temperature and electrode heating is not required.

[0164] 3) When T 结束 >T 目标Time: It means that at the end of the furnace, the predicted outlet temperature is greater than the target temperature, and it is necessary to increase the time of strong bottom blowing to lower the molten steel temperature so that the outlet temperature is equal to the target temperature. In this case, electrode heating is not required.

[0165] Step 9: Send the electrode heating time and gear to L1 to control the electrode heating. In general, except for the low gear heating when melting slag, in order to reduce the LF processing cycle, the highest gear is used for rapid heating; after completing the calculation of the electrode heating time, the calculated S 加热时间 The heating gear is sent to the corresponding electrode heating setting value of the first-level system, and a heating start instruction is sent to the first-level system. The first-level system executes the heating task based on the set heating time, and ends the heating task when the heating time is reached.

[0166] In the process of controlling the temperature of molten steel by LF electrode heating, there are many factors that affect the temperature of molten steel. It is difficult to accurately control the outlet temperature of molten steel by electrode heating. Too high temperature will increase the cost of electricity consumption, and too low temperature will lead to unqualified quality. After introducing the background blowing control method, the set value of LF electrode heating time during molten steel LF treatment can be accurately calculated, so as to accurately control the molten steel temperature to be equal to or close to the target temperature at the end of LF treatment, thereby reducing the consumption of argon and electricity during LF production.

[0167] Practice has proved that after using this LF electrode heating method to control the temperature of molten steel to control the electrode heating, the LF argon consumption and electricity consumption costs have been significantly reduced, and the LF over-target temperature has dropped from the original 1.8°C to 1°C, with significant results. It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention, and equivalent changes or substitutions made on the basis of the above technical solutions fall within the scope of protection of the claims of the present invention.

Claims

1. A method for controlling the temperature of molten steel by heating with LF electrodes, characterized in that: The method comprises the following steps: Step 1: Get the data, Step 2: Use the temperature probe to measure the initial temperature of the molten steel. After the furnace enters the station, use the temperature probe to measure the temperature of the molten steel to obtain the initial temperature of the molten steel (denoted as: T 初始 ) Step 3: Calculate the temperature change of molten steel caused by input materials; Step 4: Calculate the natural temperature drop of molten steel. Step 5: Calculate the time required for feeding. Step 6: Calculate the time required to feed the wire. Step 7: Calculate the change of temperature drop of molten steel due to bottom blowing. Step 8: Calculate the time setting value for electrode heating, Step 9: Send the electrode heating time and gear position to L1 to control the electrode heating.

2. The method for controlling the temperature of molten steel by heating LF electrodes according to claim 1, characterized in that: Step 1: Obtain data and obtain the type and weight of materials required to be added to the molten steel in this furnace from the LF alloy model.

3. The method for controlling the temperature of molten steel by heating LF electrodes according to claim 2, characterized in that: Step 3: Calculate the temperature change of molten steel caused by the input materials. The calculation results of the alloy model were obtained in step 1, including the type and weight of the required input materials (the weight of the materials is recorded as: W i , the wire feeding length is recorded as: L i ), this step mainly calculates the change of molten steel temperature after these materials are put into molten steel (the temperature drop after each material is put into molten steel is recorded as: T i ), where the temperature variation coefficient of each material is: The density of each thread is: α i , Calculation method for converting wire feeding length into weight: W i =L i ×α i ………(1) Calculation method for the change in molten steel temperature caused by adding each material: Calculation method for temperature change of molten steel caused by inputting all materials: T 物料 =T1+T2+...+T i ………(3) in: T 物料 : The temperature change of the molten steel after all materials are put in (unit: ℃); if it is a negative value, the temperature of the molten steel decreases, if it is a positive value, the temperature of the molten steel increases.

4. The method for controlling the temperature of molten steel by heating LF electrodes according to claim 3, characterized in that: Step 4: Calculate the natural temperature drop of the molten steel, that is, the time when the initial temperature of the molten steel is measured by the temperature measuring probe (denoted as: M 测温时刻 ), to the planned furnace exit time (denoted as: M 出站时刻 ), the heat of the molten steel diffuses outward through the ladle, causing the temperature of the molten steel to drop (denoted as: T 自然温降 ), the calculation method of the temperature drop of molten steel from the time when the initial temperature is measured to the time when the planned heat is finished is: T 自然温降 =W 钢水重量 ×(M 出站时刻 -M 测温时刻 )×λ 自然温降系数 ..(4) in: λ 自然温降系数 : Natural temperature drop coefficient of molten steel (unit: ℃ / t / min), W 钢水重量 : The total weight of molten steel (unit: t).

5. The method for controlling the temperature of molten steel by heating LF electrodes according to claim 4, characterized in that: Step 5: Calculate the time required for feeding, as follows: the time interval from the start of feeding to the completion of feeding, and the length of time is determined by the total weight of all materials required to be fed (recorded as: W 总重量 ) and the feeding speed of the feeding hopper (denoted as: V 下料速度 ) determines the calculation method of feeding time for all materials: S 投料时间 =W 总重量 ÷V 下料速度 ………(5) in: S 投料时间 : The time required to put in all materials (unit: min).

6. The method for controlling the temperature of molten steel by heating LF electrodes according to claim 5, characterized in that: Step 6: Calculate the time required for wire feeding, that is, the time interval from the start of wire feeding to the end of wire feeding, and the length of time is determined by the length of all wires to be fed (denoted as: L 喂丝长度 ) and the speed of the wire feeder (denoted as: V 喂丝速度 )Decide, Calculation method for feeding time of all materials: S 喂丝时间 =L 喂丝长度 ÷V 喂丝速度 ………(6) in: S 喂丝时间 : Time required for wire feeding (unit: min).

7. The method for controlling the temperature of molten steel by heating LF electrodes according to claim 6, characterized in that: Step 7: Calculate the change of temperature drop of molten steel due to bottom blowing. There are three bottom blowing modes in the whole LF treatment process, one is weak bottom blowing, one is strong bottom blowing, and the other is standard bottom blowing between weak blowing and strong blowing. The three bottom blowing modes are divided by the flow range of bottom blowing. Weak bottom blowing is used in the process of feeding, wire feeding and electrode heating in the production process; strong bottom blowing is used for a certain time (recorded as: S) after feeding, wire feeding and heating. 设定 , set for 3 minutes) to achieve uniform molten steel composition and temperature. After each batch of materials is added, each batch of wire is fed, and each heating is completed, S 设定 The strong bottom blowing of the time; the standard bottom blowing is used in the other processing time, the feeding and wire feeding batch number (denoted as: N 批次次数 , unit: times), provided by the alloy model calculation results, Calculation method of bottom blowing time for weak bottom blowing flow: S 弱 =S 投料时间 +S 喂丝时间 +S 加热时间 ......(7) Calculation method of bottom blowing time for strong bottom blowing flow: S 强 =(N 批次次数 +N 加热次数 )×S 设定 ......(8) Calculation method of bottom blowing time for standard bottom blowing flow rate: S 标准 =S 剩余 -S 弱 -S 强 ......(9) Calculation method for temperature drop of molten steel caused by bottom blowing during the whole treatment process: T 底吹温降 =S 强 ×β 强温降 +S 弱 ×β 弱温降 +S 标准 ×β 标准温降 ..(10) in: S 投料时间 : The time required to put in all materials (unit: min); S 喂丝时间 : The time required for wire feeding (unit: min); S 加热时间 : Electrode heating time (unit: min); S 弱 : Weak bottom blowing time (unit: min); S 强 : Strong bottom blowing time (unit: min); S 标准 : Standard bottom blowing time (unit: min); S 剩余 : Remaining treatment time of molten steel (unit: min); β 弱温降 : Temperature drop coefficient of molten steel under weak bottom blowing (unit: ℃ / min); β 强温降 : Temperature drop coefficient of molten steel under strong bottom blowing (unit: ℃ / min), β 标准温降 : Temperature drop coefficient of molten steel under standard bottom blowing (unit: ℃ / min); T 底吹温降 : Temperature drop of molten steel caused by bottom blowing (unit: ℃).

8. The method for controlling the temperature of molten steel by heating with LF electrodes according to claim 3 or 4, characterized in that: Step 8: Calculate the time setting value for electrode heating as follows: In order to make the molten steel temperature reach the set target temperature when it leaves the station; first, predict the molten steel temperature when it leaves the station: T 出站 =T 初始 -T 底吹温降 -T 物料 -T 自然温降 ..(10) in: T 物料 : The temperature change of molten steel after all materials are put into the furnace (unit: °C); T 自然温降 : The temperature drop of the molten steel caused by the heat diffusion from the molten steel through the ladle (unit: °C); T 底吹温降 : Temperature drop of molten steel caused by bottom blowing (unit: °C); T 初始 : Initial temperature measured by the temperature probe (unit: °C); T 出站 : The predicted temperature when the furnace is finished according to the planned time (unit: °C), Secondly, compare T 出站 and T 目标 , and perform corresponding processing according to the comparison situation: 1) When T 出站 <T 目标 Time: It means that at the end of the furnace, the predicted outlet temperature is not enough, and electrode heating is required to increase the temperature of the molten steel. In order to calculate the electrode heating time, the electrothermal conversion coefficient (denoted as: λ 电热 , unit: kwh / t / ℃) and electrode heating efficiency coefficient (denoted as: μ 加热效率 , unit: kwh / min); these two coefficients are system parameters of the LF electrode heating system, provided by the electrode manufacturer. Regarding the electrode heating efficiency, each heating gear in the electrode heating system has a heating efficiency coefficient for that gear. In the process of calculating the heating time, the heating efficiency coefficient is selected according to the gear set by the current heating system; when the gear changes, the heating time will be recalculated. Calculate the time for electrode heating: S 加热时间 =W 钢水重量 ×(T 目标 -T 出站 )×λ 电热 ÷μ 加热效率 .(11) in: T 目标 : The target temperature of the molten steel obtained from the secondary process control system in step 1 (unit: °C); T 出站 : The predicted temperature when the furnace leaves the station at the planned time (unit: °C), W 钢水重量 : Total weight of molten steel (unit: t), λ 电热 : Electric heat conversion coefficient (unit: kwh / t / ℃); μ 加热效率 : Electrode heating efficiency coefficient (unit: kwh / min); S 加热时间 : Electrode heating time (unit: min); 2) When T 结束 =T 目标 When: It means that at the end of the furnace, the predicted outlet temperature is equal to the target temperature, and electrode heating is not required. 3) When T 结束 >T 目标 Time: It means that at the end of the furnace, the predicted outlet temperature is greater than the target temperature, and it is necessary to increase the time of strong bottom blowing to lower the molten steel temperature so that the outlet temperature is equal to the target temperature. In this case, electrode heating is not required.

9. The method for controlling the temperature of molten steel by heating LF electrodes according to claim 8, characterized in that: Step 9: Send the electrode heating time and gear to L1 to control the electrode heating. In order to reduce the LF processing cycle, the highest gear is used for rapid heating. After completing the calculation of the electrode heating time, the calculated S 加热时间 The heating gear is sent to the corresponding electrode heating setting value of the first-level system, and a heating start instruction is sent to the first-level system. The first-level system executes the heating task based on the set heating time, and ends the heating task when the heating time is reached.

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