A method for accelerating the heating speed of a ladle refining furnace

Abstract

This invention discloses a method for accelerating the heating rate of a ladle refining furnace, comprising the following steps: a) adding hot slag into the ladle; b) after the molten steel enters the ladle heating position, within the first 5 minutes of smelting, CO2 is blown into the ladle through the bottom blowing system, and a foaming agent is added to the ladle furnace to rapidly form foamed slag in the ladle. The electrode arc current is adjusted to 25000A and the electrode arc voltage to 120V, so that the slag temperature rises rapidly to above 1500℃; c) within 5-10 minutes of smelting, argon gas is blown into the ladle, with the electrode arc current at 15000A and the voltage at 120V to maintain the stability of the arc, and a refining slag conditioner is added; active lime is added to maintain the thickness of the refining slag layer during this process, with a target refining slag temperature of 1550-1650℃ in the middle stage; d) after 10 minutes of smelting, active lime is added, and the ladle bottom blowing flow rate is adjusted to 1-5 m³ / h. 3 The electrode arc current is 25000A and the voltage is 120V to heat the molten steel. After the molten steel reaches the commanded temperature, the electrode is raised to end the molten steel heating operation, so as to effectively improve the overall heating rate of the ladle furnace.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for accelerating the heating rate of a ladle refining furnace. Background Technology

[0002] A ladle refining furnace is an important metallurgical equipment used to refine molten steel from primary furnaces (electric arc furnaces, open-hearth furnaces, converters), and to regulate the temperature, composition, and inclusions of the molten steel, thus providing a buffer for continuous casting and rolling processes.

[0003] The steel temperature heating system in the ladle refining furnace mainly consists of a transformer, a high-voltage control system, water-cooled cables, conductive cross arms, electrode holders, and graphite electrodes. During the heating process, the electrical system controls the electrode current, voltage, and the distance between the graphite electrodes and the molten steel surface, which can generate a high-temperature electric arc between the graphite electrodes and the molten steel. The heat transfer between the electric arc, steel slag, and molten steel is used to heat the molten steel in the ladle furnace.

[0004] The main factors affecting the heating rate of a ladle refining furnace include the current intensity of the electric arc and the slag's ability to envelop the arc. The current intensity of the electric arc is the primary energy source for the ladle furnace; the larger the arc current, the faster the furnace heats up. However, the arc current is limited by the transformer's power and cannot be increased indefinitely. During ladle furnace smelting, the thickness of the slag layer is directly related to the arc's enveloping properties. Maintaining a slag thickness greater than the arc length during smelting ensures the arc is completely enveloped. In the early stages of ladle furnace refining, due to the low slag temperature and the addition of various solid slagging agents, the slag cannot liquefy rapidly, thus failing to effectively envelop the arc and affecting the heating efficiency of the molten steel. The heating rate during ladle furnace smelting is often maintained at 2-3℃ / min. In the middle and later stages of ladle furnace smelting, if the slag layer thickness and molten slag composition are not properly controlled, allowing the molten slag to enter the high melting point region, the slagging process will be prolonged, damaging the slag's ability to envelop the arc and affecting the furnace's heating efficiency. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for accelerating the heating rate of a ladle refining furnace, thereby solving the problem that insufficient slag layer thickness affects the encapsulation of the electric arc during ladle furnace smelting, resulting in slow heat transfer from the electric arc to the molten steel.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for accelerating the heating rate of a ladle refining furnace includes the following steps:

[0008] a. Add hot slag into the ladle at the steel ladle receiving point, with a hot slag dosage of 4-5 kg / ton of steel;

[0009] b. After the molten steel enters the ladle heating position, CO2 is blown into the ladle through the bottom blowing system within the first 5 minutes of smelting, with a bottom blowing flow rate of 5-10 m³ / h. 3 / h, and add 1-2kg / ton of foaming agent to the ladle furnace to quickly form 100-250mm foam slag in the ladle. Adjust the electrode arc current to 25000A and the electrode arc voltage to 120V to make the slag temperature rise rapidly to above 1500℃.

[0010] c. Within 5-10 minutes of smelting, argon gas is blown into the ladle at a flow rate of 10-15 m³ / min. 3 The electrode arc current is 15000A and the voltage is 120V per hour to maintain arc stability. A refining slag conditioner is added at a rate of 1-3 kg / ton of steel. Activated lime is added at a rate of 2-4 kg / ton of steel to maintain a refining slag layer thickness of 150-200 mm. The target temperature for the intermediate refining slag is 1550-1650℃. The target composition of the intermediate refining slag is: CaO 40-45%; SiO2 45-55%; Al2O3 5-15%.

[0011] d. After smelting for 10 minutes, add quicklime at a rate of 1-3 kg / ton of steel, and adjust the bottom blowing flow rate of the ladle to 1-5 m³ / min. 3 The electrode arc current is 25000A and the voltage is 120V to heat the molten steel. After the molten steel reaches the specified temperature, the electrode is lifted to end the molten steel heating operation.

[0012] In step a, the composition of the hot slag is as follows: CaO 55-65%; SiO2 25-35%; Al2O3 5-10%; FeO 0-1%; and the hot slag temperature is 1400-1500℃.

[0013] In step b, the foaming agent is a compressed briquette with a particle size of 3-10 mm, and the foaming agent contains 65-84% C, 5-12% CaF2, 2-5% NaF, and 3-8% Al2O3.

[0014] In step c, the refining slag conditioner has a particle size of 10-30mm and is in the form of 45-55% SiO2, 40-45% Al2O3, and 5-10% other components.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: In the early stage of slag formation during steel refining, circulating hot slag is added. The latent heat of the hot slag and the high-current heating allow for rapid liquefaction of the steel slag, creating conditions for the rapid formation of foamed slag. In the early stage, CO2 gas is blown in to maintain an oxidizing atmosphere in the furnace, providing a stable oxidizing atmosphere for the foaming agent. This allows for the rapid formation of foamed slag in the early smelting stage, ensuring the slag layer thickness reaches the level required to envelop the electric arc, thus increasing the heating rate of the ladle furnace in the early stage. In the middle stage of smelting, lime and slag adjusters are added to adjust the slag composition into a low-melting-point region, enabling rapid slag liquefaction and increasing the amount of slag during the smelting process. This ensures that the thickness of the molten slag in the middle stage of smelting reaches the level required to envelop the electric arc. To improve heating efficiency, it is necessary to increase the arc flow intensity and reduce the bottom blowing flow rate in the later stages of smelting. This reduces the heat carried out by the bottom blowing and allows the molten steel temperature to be raised rapidly to the target temperature. Through the aforementioned series of measures, liquid slag that completely encapsulates the electric arc can be formed during the ladle furnace smelting process, thereby increasing the molten steel temperature during the ladle furnace refining process. This increases the overall heating rate of the ladle furnace from 2-4℃ / min to 4-6℃ / min, thus shortening the smelting cycle of the ladle furnace, improving its production efficiency, reducing electricity costs and the amount of graphite electrodes used in the smelting process, and ultimately saving costs and stabilizing the production rhythm of the ladle furnace. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.

[0017] Example 1:

[0018] Taking a 60t ladle furnace producing HRB400 as an example, this paper illustrates a method to accelerate the heating rate of a ladle refining furnace, with a refining cycle of 30 minutes.

[0019] (1) Add the residual circulating hot slag into the ladle at the refining molten steel receiving position, with a circulating hot slag usage of 4 kg / ton of steel;

[0020] (2) After the molten steel enters the ladle heating position, CO2 gas is blown into the ladle through the bottom blowing system within the first 5 minutes of smelting. The bottom blowing flow rate is 5 m³ / s. 3 / h, and add 1kg / ton of foaming agent to the ladle furnace to quickly form 110mm foam slag in the ladle. Adjust the electrode arc current to 25000A and the electrode arc voltage to 120V to make the slag temperature rise rapidly to 1520℃.

[0021] (3) Within 5-10 minutes of smelting, argon gas is blown into the ladle at a flow rate of 10 m³ / min. 3The electrode arc current is 15000A and the voltage is 120V per hour to maintain arc stability. A refining slag conditioner is added at a rate of 1 kg / ton of steel. Activated lime is added at a rate of 2 kg / ton of steel to maintain a layer thickness of 150 mm. The target temperature for the refining slag is 1550℃. The target mid-term composition of the refining slag is: CaO 42%; SiO2 45%; Al2O3 5%.

[0022] (4) After smelting for 10 minutes, add quicklime at a rate of 1 kg / ton of steel. Adjust the bottom blowing flow rate of the ladle to 1 m³ / min. 3 The electrode arc current is 25000A and the voltage is 120V to heat the molten steel. After the molten steel temperature reaches 1600℃, the electrode is lifted to end the molten steel heating operation.

[0023] Using this method, the heating rate of the ladle furnace can be effectively increased from 3℃ / min to 4℃ / min, shortening the smelting cycle of the ladle furnace by 5 minutes.

[0024] Example 2:

[0025] Taking a 60t ladle furnace producing 87B steel as an example, this paper illustrates a method to accelerate the heating rate of a ladle refining furnace, with a refining cycle of 60 minutes.

[0026] (1) Add the residual circulating hot slag into the ladle at the refining molten steel receiving position, with a circulating hot slag usage of 5 kg / ton of steel;

[0027] (2) After the molten steel enters the ladle heating position, CO2 gas is blown into the ladle through the bottom blowing system within the first 5 minutes of smelting. The bottom blowing flow rate is 10 m³ / min. 3 / h, and add 2kg / ton of foaming agent to the ladle furnace to quickly form 250mm of foamed slag inside the ladle. Adjust the electrode arc current to 25000A and the electrode arc voltage to 120V to rapidly raise the slag temperature to 1510℃;

[0028] (3) Within 5-10 minutes of smelting, argon gas is blown into the ladle at a flow rate of 15 m³ / min. 3 The electrode arc current is 15000A and the voltage is 120V per hour to maintain arc stability. A refining slag conditioner is added at a rate of 3 kg / ton of steel; quicklime is added at a rate of 4 kg / ton of steel to maintain a process layer thickness of 200 mm. The target temperature for the refining slag is 1550℃, and the target mid-term composition for the refining slag is: CaO: 45%; SiO2: 55%; Al2O3: 14%.

[0029] (4) After smelting for 10 minutes, add quicklime at a rate of 3 kg / ton of steel. Adjust the bottom blowing flow rate of the ladle to 5 m³ / min. 3The electrode arc current is 25000A and the voltage is 120V to heat the molten steel. After the molten steel temperature reaches 1560℃, the electrode is lifted to end the molten steel heating operation.

[0030] Using this method, the heating rate of the ladle furnace can be effectively increased from 3℃ / min to 6℃ / min, shortening the smelting cycle of the ladle furnace by 10 minutes.

[0031] Example 3:

[0032] Taking a 60t ladle furnace producing R30 as an example, this paper illustrates a method to accelerate the heating rate of a ladle refining furnace, with a refining cycle of 40 minutes.

[0033] (1) At the refining steel receiving position, the residual circulating hot slag in the ladle is added into the ladle, and the amount of circulating hot slag is 4.5 kg / ton of steel;

[0034] (2) After the molten steel enters the ladle heating position, CO2 gas is blown into the ladle through the bottom blowing system within the first 5 minutes of smelting. The bottom blowing flow rate is 8 m³ / s. 3 / h, and add 1.5kg / ton of foaming agent to the ladle furnace to quickly form 180mm of foamed slag inside the ladle. Adjust the electrode arc current to 25000A and the electrode arc voltage to 120V to rapidly raise the slag temperature to 1550℃;

[0035] (3) Within 5-10 minutes of smelting, argon gas is blown into the ladle at a flow rate of 13 m³ / min. 3 The electrode arc current is 15000A and the voltage is 120V per hour to maintain arc stability. A refining slag conditioner is added at a rate of 2 kg / ton of steel; quicklime is added at a rate of 3 kg / ton of steel to maintain a process layer thickness of 180 mm. The target temperature for the refining slag is 1550℃, and the target composition is: CaO: 42%; SiO2: 51%; Al2O3: 7%.

[0036] (4) After smelting for 10 minutes, add quicklime at a rate of 2 kg / ton of steel. Adjust the bottom blowing flow rate of the ladle to 3 m³ / min. 3 The electrode arc current is 25000A and the voltage is 120V to heat the molten steel. After the molten steel temperature reaches 1600℃, the electrode is lifted to end the molten steel heating operation.

[0037] Using this method, the heating rate of the ladle furnace can be effectively increased from 3℃ / min to 4℃ / min, shortening the smelting cycle of the ladle furnace by 7 minutes.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for accelerating the heating rate of a ladle refining furnace, characterized in that: Includes the following steps: a. Add hot slag into the ladle at the steel ladle receiving point, with a hot slag dosage of 4-5 kg / ton of steel; b. After the molten steel enters the ladle heating position, CO2 is blown into the ladle through the bottom blowing system within the first 5 minutes of smelting, with a bottom blowing flow rate of 5-10 m³ / h. 3 / h, and add 1-2kg / ton of foaming agent to the ladle furnace to quickly form 100-250mm foam slag in the ladle. Adjust the electrode arc current to 25000A and the electrode arc voltage to 120V to make the slag temperature rise rapidly to above 1500℃. c. Within 5-10 minutes of smelting, argon gas is blown into the ladle at a flow rate of 10-15 m³ / min. 3 The electrode arc current is 15000A and the voltage is 120V per hour to maintain arc stability. A refining slag conditioner is added at a rate of 1-3 kg / ton of steel. Activated lime is added at a rate of 2-4 kg / ton of steel to maintain a refining slag layer thickness of 150-200 mm. The target temperature for the intermediate refining slag is 1550-1650℃. The target composition of the intermediate refining slag is: CaO 40-45%; SiO2 45-55%; Al2O3 5-15%. d. After smelting for 10 minutes, add quicklime at a rate of 1-3 kg / ton of steel, and adjust the bottom blowing flow rate of the ladle to 1-5 m³ / min. 3 The electrode arc current is 25000A and the voltage is 120V to heat the molten steel. After the molten steel reaches the specified temperature, the electrode is lifted to end the molten steel heating operation.

2. The method for accelerating the heating rate of a ladle refining furnace according to claim 1, characterized in that, In step a, the composition of the hot slag is as follows: CaO 55-65%; SiO2 25-35%; Al2O3 5-10%; FeO 0-1%; and the hot slag temperature is 1400-1500℃.

3. The method for accelerating the heating rate of a ladle refining furnace according to claim 1, characterized in that, In step b, the foaming agent is a compressed briquette with a particle size of 3-10 mm. The foaming agent contains 65-84% C, 5-12% CaF2, 2-5% NaF, and 3-8% Al2O3.

4. The method for accelerating the heating rate of a ladle refining furnace according to claim 1, characterized in that, In step c, the refining slag conditioner has a particle size of 10-30mm and is made of 45-55% SiO2, 40-45% Al2O3, and 5-10% other components.