Power supply control method based on graded heating of LF (Ladle Furnace)

Abstract

The invention discloses a power supply control method based on graded heating of an LF refining furnace. The power supply control method is characterized by comprising the following steps of stage division, wherein the LF refining process is divided into the following steps: 1) a heating stage-an early refining stage; (2) a heat preservation stage-a refining later stage; power supply control in a temperature rise stage: selecting a higher voltage grade, and matching economic current corresponding to the voltage; the thickness of the slag is controlled to be larger than the length of an electric arc, long-arc submerged arc operation is adopted, and it is ensured that the wear index of a refractory is smaller than or equal to 850000 kW.V / m < 2 >; power supply control in a heat preservation stage: selecting a lower voltage grade, and matching economic current corresponding to the voltage; and the arc length is controlled to be smaller than or equal to 60 mm, it is ensured that the wear index of the refractory material is smaller than or equal to 350,000 kW.V / m < 2 >, and According to the method, the voltage and current parameters are optimized in stages, so that the refractory material loss and the power consumption are reduced while the heating efficiency is ensured, and the economical efficiency and the stability of the refining process are improved.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and particularly relates to a power supply control method based on staged heating in an LF refining furnace. Background Technology

[0002] As a key piece of equipment in steel production, the LF refining furnace mainly functions to heat molten steel, adjust its composition, and maintain its temperature. Current technologies often suffer from the following problems with the power supply system of LF refining furnaces: 1) The use of a single or a few sets of voltage and current parameters throughout the refining process leads to low heating efficiency or severe refractory material wear; 2) The power supply parameters are not optimized for the different needs of the heating and holding stages, resulting in wasted energy and high electrode consumption; 3) Improper control of the refractory material wear index leads to a shortened ladle life, increased inclusions in the molten steel, and affects product quality.

[0003] Existing research shows that parameters such as arc power, refractory wear index, and steel heating rate in LF refining furnaces are significantly correlated with voltage and current, and the economic current (the current value corresponding to the maximum arc power) increases with increasing voltage level. Therefore, there is an urgent need for a staged heating technology that dynamically adjusts power supply parameters according to the refining stage to achieve energy conservation, emission reduction, cost reduction, and efficiency improvement. Summary of the Invention

[0004] The purpose of this invention is to provide a power supply control method for staged heating in an LF refining furnace. By optimizing voltage and current parameters in stages, the method can reduce refractory material loss and power consumption while ensuring heating efficiency, thereby improving the economy and stability of the refining process.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention discloses a power supply control method for staged heating in an LF refining furnace, comprising the following steps:

[0007] Phase Division: The LF refining process is divided into: 1) Heating stage - early refining stage; 2) Holding stage - late refining stage;

[0008] Power supply control during the heating phase: Select a higher voltage level and match the corresponding economic current; control the slag thickness to be greater than the arc length, adopt long-arc submerged arc operation, and ensure that the refractory wear index is ≤

[0009] 850000kW·V / m 2 ;

[0010] Power supply control during the insulation stage: Select a lower voltage level and match the corresponding economic current; control the arc length to ≤60mm to ensure the refractory wear index is ≤350000kW·V / m 2 This reduces energy consumption.

[0011] Furthermore, the higher voltage level is level 9-11.

[0012] Furthermore, the lower voltage level is level 1-3.

[0013] Furthermore, during the heating phase (0-30 min): voltage level: 11, 344V; economic current: 37kA; control parameters: arc power 14857kW, arc length 92mm, slag thickness 100-120mm.

[0014] Results: The molten steel temperature rises at a rate of 4.4℃ / min, increasing from 1550℃ to 1680℃ within 30 minutes.

[0015] Furthermore, during the heat preservation stage (30-60 min): Voltage level: Class 2, 246V; Economic current: 26kA; Control parameters: Arc power 7598kW, Arc length 54mm, Slag thickness 80-100mm; Results: Molten steel temperature stabilized at 1670-1680℃, Refractory abrasion index 293233kW·V / m 2 .

[0016] Furthermore, during the heating phase (0-25 min): Voltage level: Class 10, 331V; Economic current: 35kA; Control parameters: Arc power 13755kW, Arc length 87mm, Slag thickness 110-130mm; Effect: Steel heating rate 4.2℃ / min, raising the steel temperature from 1540℃ to 1640℃ within 25 minutes.

[0017] Furthermore, during the heat preservation stage (25-50 min): Voltage level: Class 3, 255V; Economic current: 27kA; Control parameters: Arc power 8164kW, Arc length 57mm, Slag thickness 90-110mm; Results: Molten steel temperature stabilized at 1630-1640℃, Refractory abrasion index 326609kW·V / m 2 .

[0018] Furthermore, during the heating phase (0-20 min): Voltage level: 9, 320V; Economic current: 34kA; Control parameters: Arc power 12856kW, Arc length 83mm, Slag thickness 100-120mm; Effect: Steel heating rate 3.9℃ / min, raising the steel temperature from 1530℃ to 1610℃ within 20 minutes.

[0019] Furthermore, during the heat preservation stage (20-40 min): Voltage level: Class 1, 238V; Economic current: 26kA; Control parameters: Arc power 7112kW, Arc length 51mm, Slag thickness 80-100mm; Results: Molten steel temperature stabilized at 1600-1610℃, Refractory abrasion index 265545kW·V / m 2 .

[0020] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0021] During the heating stage, a combination of high voltage and economical current is used to increase the heating rate of molten steel (up to 4.4℃ / min) and shorten the smelting cycle; during the holding stage, a combination of low voltage and economical current is used to reduce refractory wear (wear index ≤350000kW·V / m). 2 This extends the life of the ladle; it matches the economic current throughout the process, reducing reactive power consumption and lowering power consumption by 10%-15%; and it reduces steel inclusions and improves product quality by matching and controlling the slag thickness with the arc length. Detailed Implementation

[0022] The present invention will be further described below through examples.

[0023] Example 1: Heating control for staged refining of high-carbon steel (Solution of this application)

[0024] 1. Heating phase (0-30 min):

[0025] Voltage rating: 11 (344V);

[0026] Economic current: 37kA;

[0027] Control parameters: Arc power 14857kW, arc length 92mm, slag thickness 100-120mm;

[0028] Results: The molten steel temperature rises at a rate of 4.4℃ / min, increasing from 1550℃ to 1680℃ within 30 minutes.

[0029] 2. Heat preservation stage (30-60 min):

[0030] Voltage rating: Level 2 (246V);

[0031] Economic current: 26kA;

[0032] Control parameters: Arc power 7598kW, arc length 54mm, slag thickness 80-100mm;

[0033] Results: The molten steel temperature remained stable at 1670-1680℃, and the refractory wear index was 293233 kW·V / m. 2 .

[0034] Comparative Example 1: (Original Process)

[0035] 1. Single parameter throughout (0-60min)

[0036] Voltage rating: Level 6 (290V);

[0037] Current: 30kA;

[0038] Control parameters: Arc power 9860kW, arc length 70mm, slag thickness 80-100mm;

[0039] Results: The steel heating rate is 2.8℃ / min, and the steel temperature rises from 1550℃ to 1720℃ within 60 minutes (overheating by 40℃). The power consumption is 410 kWh / t (29% higher than that of this application), the electrode consumption is 1.2 kg / t (50% higher than that of this application), and the refractory wear index is 680,000 kW·V / m. 2 (132% higher than this application).

[0040] Example 2: Heating control for staged refining of low-alloy steel (Solution of this application)

[0041] 1. Heating phase (0-25 min):

[0042] Voltage rating: 10 (331V);

[0043] Economic current: 35kA;

[0044] Control parameters: Arc power 13755kW, arc length 87mm, slag thickness 110-130mm;

[0045] Results: The molten steel temperature rises at a rate of 4.2℃ / min, increasing from 1540℃ to 1640℃ within 25 minutes.

[0046] 2. Incubation stage (25-50 min):

[0047] Voltage rating: Level 3 (255V);

[0048] Economic current: 27kA;

[0049] Control parameters: Arc power 8164kW, arc length 57mm, slag thickness 90-110mm;

[0050] Results: The molten steel temperature remained stable at 1630-1640℃, and the refractory wear index was 326609kW·V / m. 2 .

[0051] Comparative Example 2: (Original Process)

[0052] 1. Phased but not matched economic current (0-50min);

[0053] Heating stage (0-25min): Voltage level 8 (305V), current 32kA, arc power 10680kW;

[0054] Heat preservation stage (25-50min): Voltage level 5 (278V), current 28kA, arc power 8864kW;

[0055] Results: The steel heating rate was 3.1℃ / min (26% lower than that of this application); the steel temperature rose from 1540℃ to 1618℃ within 25 minutes (22℃ less than the target temperature); the temperature fluctuation during the holding period was ±12℃; the power consumption was 368kWh / t (25% higher than that of this application); and the refractory wear index was 510000kW·V / m. 2 (56% higher than this application).

[0056] Example 3: Heating control for staged refining of plain carbon steel (Scheme of this application)

[0057] 1. Heating phase (0-20 min):

[0058] Voltage rating: Level 9 (320V);

[0059] Economic current: 34kA;

[0060] Control parameters: Arc power 12856kW, arc length 83mm, slag thickness 100-120mm;

[0061] Results: The molten steel temperature rises at a rate of 3.9℃ / min, increasing from 1530℃ to 1610℃ within 20 minutes.

[0062] 2. Insulation stage (20-40 min):

[0063] Voltage rating: Level 1 (238V);

[0064] Economic current: 26kA;

[0065] Control parameters: Arc power 7112kW, arc length 51mm, slag thickness 80-100mm;

[0066] Results: The molten steel temperature remained stable at 1600-1610℃, and the refractory wear index was 265545 kW·V / m. 2 .

[0067] Comparative Example 3: (Original Process)

[0068] 1. Low voltage and high current throughout (0-40min);

[0069] Voltage rating: Level 3 (255V);

[0070] Current: 38kA;

[0071] Parameters: Arc power 10890kW, arc length 65mm, slag thickness 70-90mm;

[0072] Results: The steel heating rate is 2.5℃ / min (36% lower than that of this application); the steel temperature rises from 1530℃ to 1630℃ within 40 minutes (twice the time); the power consumption is 355kWh / t (32% higher than that of this application); the electrode consumption is 1.1kg / t (57% higher than that of this application); and the refractory wear index is 720000kW·V / m. 2 (171% higher than this application).

[0073] Compared with the original process, the beneficial technical effects of this invention are as follows: Improved efficiency: The high voltage-economic current combination is used in the heating stage, which increases the heating rate by 35%-45% compared with the traditional process, shortens the smelting cycle by 15%-25%, and avoids the problem of molten steel overheating or failing to reach the target temperature; Reduced losses: The low voltage-economic current combination is used in the heat preservation stage, which reduces the wear index of refractory materials by 45%-65% compared with the traditional process, extends the life of the ladle by more than 30%, and reduces electrode consumption by 30%-50%; Optimized energy consumption: The economic current is matched throughout the process, reducing reactive power consumption, and reducing power consumption by 25%-32% compared with the traditional process, saving 80-100 kWh of electricity per ton of steel.

[0074] In the above embodiments, the voltage and current parameters at each stage are based on the principle of economic current matching, and the submerged arc operation is achieved by controlling the slag thickness, so as to minimize refractory material loss and power consumption while ensuring heating efficiency.

[0075] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A power supply control method based on staged heating in an LF refining furnace, characterized in that: Includes the following steps: Phase Division: The LF refining process is divided into: 1) Heating stage - early refining stage; 2) Heat preservation stage - late refining stage; Power supply control during the heating phase: Select a higher voltage level and match the corresponding economic current; control the slag thickness to be greater than the arc length, adopt long-arc submerged arc operation, and ensure that the refractory wear index is ≤ 850000kW·V / m 2 ; Power supply control during the insulation stage: Select a lower voltage level and match the corresponding economic current; control the arc length to ≤60mm to ensure the refractory wear index is ≤350000kW·V / m 2 This reduces energy consumption.

2. The power supply control method for staged heating of an LF refining furnace according to claim 1, characterized in that: The higher voltage level is level 9-11.

3. The power supply control method for staged heating of an LF refining furnace according to claim 1, characterized in that: The lower voltage levels are 1-3.

4. The power supply control method for staged heating of an LF refining furnace according to claim 1, characterized in that: Heating stage 0-30min: Voltage level: Class 11, 344V; Economic current: 37kA; Control parameters: Arc power 14857kW, Arc length 92mm, Slag thickness 100-120mm. Results: The molten steel temperature rises at a rate of 4.4℃ / min, increasing from 1550℃ to 1680℃ within 30 minutes.

5. The power supply control method for staged heating of an LF refining furnace according to claim 4, characterized in that: Insulation stage 30-60min: Voltage level: Level 2, 246V; Economic current: 26kA; Control parameters: Arc power 7598kW, Arc length 54mm, Slag thickness 80-100mm; Results: The molten steel temperature remained stable at 1670-1680℃, and the refractory wear index was 293233 kW·V / m. 2 .

6. The power supply control method for staged heating of an LF refining furnace according to claim 1, characterized in that: Heating stage 0-25min: Voltage level: Class 10, 331V; Economic current: 35kA; Control parameters: Arc power 13755kW, Arc length 87mm, Slag thickness 110-130mm. Results: The molten steel temperature rises at a rate of 4.2℃ / min, increasing from 1540℃ to 1640℃ within 25 minutes.

7. The power supply control method for staged heating of an LF refining furnace according to claim 6, characterized in that: Holding stage (25-50 min): Voltage level: Class 3, 255V; Economic current: 27kA; Control parameters: Arc power 8164kW, Arc length 57mm, Slag thickness 90-110mm; Results: Molten steel temperature stabilized at 1630-1640℃, Refractory abrasion index 326609kW·V / m 2 .

8. The power supply control method for staged heating of an LF refining furnace according to claim 1, characterized in that: Heating stage 0-20min: Voltage level: Level 9, 320V; Economic current: 34kA; Control parameters: Arc power 12856kW, Arc length 83mm, Slag thickness 100-120mm. Results: The molten steel temperature rises at a rate of 3.9℃ / min, increasing from 1530℃ to 1610℃ within 20 minutes.

9. The power supply control method for staged heating of an LF refining furnace according to claim 8, characterized in that: Holding stage (20-40 min): Voltage level: Class 1, 238V; Economic current: 26kA; Control parameters: Arc power 7112kW, Arc length 51mm, Slag thickness 80-100mm; Results: Molten steel temperature stabilized at 1600-1610℃, Refractory abrasion index 265545kW·V / m 2 .