Method for reducing vacuum treatment period by adding metal material into RH vacuum furnace

Abstract

The invention discloses a method for reducing a vacuum treatment period by adding a metal material into an RH vacuum furnace, and belongs to the technical field of metal smelting. In the RH vacuum refining process, a metal material containing FeO is added into a vacuum chamber of an RH vacuum furnace for direct oxygenation, then oxygen determination is conducted on molten steel, oxygen is blown into the molten steel through a top lance according to the oxygen determination condition, and oxygen determination is conducted on the molten steel after oxygen blowing through the top lance is completed till the oxygen content in the molten steel reaches 60-120 ppm. In the RH vacuum treatment period, the metal material is added to directly increase oxygen to the molten steel, meanwhile, the circulating vacuum degree of the vacuum chamber and the circulating gas lifting process are optimized, Fe in the metal material is reduced through carbon and oxygen reduction, steel and iron material consumption is reduced, the oxygen enrichment time in the vacuum oxygen blowing process is shortened, the vacuum treatment period is shortened, and steel and iron material consumption and power consumption are reduced; meanwhile, the high-oxidability erosion time of the vacuum chamber is shortened, and the refractory erosion condition of the vacuum chamber is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal smelting, and in particular relates to a method for adding metal materials to an RH vacuum furnace to reduce a vacuum treatment cycle. Background Art

[0002] RH vacuum furnace is the key equipment for producing ultra-low carbon steel, and plays an important role in improving product structure and upgrading product quality. The main task of RH vacuum refining process is to degas, float non-metallic inclusions through molten steel circulation, and even out molten steel composition and temperature. At the same time, it has multiple metallurgical functions such as deoxidation, decarburization, dephosphorization, desulfurization, and composition fine-tuning through the material addition system.

[0003] RH vacuum refining uses an ultra-low carbon mode to remove carbon from steel to an extremely low level, and then alloys are added to meet the low-carbon requirements of steel. Currently, in the RH vacuum refining production process, the converter reduces the final oxygen by high carbon drawing, and the carbon content of the RH vacuum furnace molten steel entering the station is 600ppm higher than the oxygen content. The RH vacuum furnace needs to add oxygen to the molten steel through a top-blown oxygen lance. The oxygen addition process takes a long time, resulting in a long production cycle. In addition, during the vacuum oxygen blowing process, the oxygen enrichment of the molten steel in the vacuum chamber has a greater erosion on the refractory, affecting the life of the refractory in the vacuum chamber.

[0004] When RH is used to smelt low-carbon and ultra-low-carbon steel, if the carbon content is too high and the free oxygen is insufficient when the RH arrives at the station, oxygen is usually added to the molten steel by blowing oxygen from a top gun to ensure a good decarburization effect. The method of blowing oxygen from a top gun has a certain impact on the refractory materials in the vacuum chamber; and during the process of blowing oxygen from a top gun, oxygen and molten steel are in surface contact, which is easily affected by the vacuum of the system and leads to unstable absorption rate. Patent CN106498127A discloses an oxygen addition method for the RH refining process. In view of the technical problems that the oxygen absorption rate is unstable when the temperature is not sufficient in the prior art, and that scrap steel is added to cool down the furnace with a very high temperature at the RH arrival station, when the oxygen activity a[O] does not meet the carbon-oxygen relationship, oxygen addition is achieved by adding a solid oxygenator, which not only eliminates the impact of oxygen on the refractory materials in the vacuum chamber, but also improves the oxygen absorption rate during oxygen addition. However, this method not only requires temperature surplus calculation when RH arrives at the station, but also requires judgment of the oxygen activity a[O] of the oxygen determination result when the temperature is surplus, that is, if the oxygen activity a[O] meets the decarburization conditions of the carbon-oxygen relationship, natural decarburization is performed; if the oxygen activity a[O] does not meet the carbon-oxygen relationship, solid oxygenator is added for oxygenation and forced decarburization is performed. The patented method has a complex processing process and a long oxygenation process, resulting in a long production cycle. Summary of the invention

[0005] Aiming at the problems of top gun oxygen blowing in the vacuum refining process of RH vacuum furnace in the prior art, which causes erosion of vacuum chamber refractory, long oxygen addition time and complicated oxygen addition process, the present invention provides a method for reducing vacuum treatment cycle by adding metal material in RH vacuum furnace, which improves erosion of vacuum refractory while ensuring stable casting of casting machine and reducing steel material and electricity consumption in steelmaking cost, and reduces vacuum treatment cycle.

[0006] The present invention is achieved through the following technical solutions: A method for reducing the vacuum treatment cycle by adding metal materials in an RH vacuum furnace. During the RH vacuum refining process, a metal material containing FeO is added into a vacuum chamber of the RH vacuum furnace to directly increase oxygen, and then the molten steel is oxygenated. Oxygen is blown into the molten steel through a top gun according to the oxygen determination condition. After the top gun oxygen blowing is completed, the molten steel is oxygenated until the oxygen content in the molten steel reaches 60-120 ppm.

[0007] Furthermore, the mass percentage of FeO in the FeO-containing metal material is 50-70%, and H2O≤1%.

[0008] Furthermore, the specific operation of RH vacuum refining is: (1) Start of vacuum treatment: Increase the gas setting to 60-80m³ / h and start the vacuum cooling mode; (2) During the 2.5-3.5 minutes of vacuum treatment, the gas is set to 80-100 m³ / t, the hot mode is started, and metal materials containing FeO are added to the molten steel. The vacuum degree is controlled at 10-30 mbar. (3) During the 4.5-5.5 minutes of vacuum treatment, set the boost gas to 140-160 m³ / h, start the cold mode, and control the vacuum degree to ≤4 mbar.

[0009] (4) At the 6.5-7.5 minute mark of vacuum treatment, the gas is set at 80-100 m³ / h, the hot mode is started, and oxygen is determined in the molten steel. According to the oxygen determination conditions, oxygen is blown into the molten steel with a top gun until the carbon-oxygen balance is reached, and the vacuum degree is controlled at 10-30 mbar; (5) After the oxygen blowing is completed, the gas setting is increased to 160-180m³ / h, and the cold mode is started. When the vacuum degree is ≤3mbar and lasts for 2-3min, the molten steel is oxygenated. When the oxygen content in the molten steel is between 60-120ppm, the molten steel has been treated.

[0010] Furthermore, the specific operation of RH vacuum refining is: (1) Start of vacuum treatment: Increase the gas setting to 60-80m³ / h and start the vacuum cooling mode; (2) Vacuum treatment at the 3rd minute: Set the gas pressure to 80-100 m³ / t, start the hot mode, add FeO-containing metal material to the molten steel, and control the vacuum degree to 10-30 mbar; (3) 5 minutes of vacuum treatment: Set the gas flow rate to 140-160 m³ / h, start the cold mode, and control the vacuum degree to ≤4 mbar.

[0011] (4) At the 7th minute of vacuum treatment, the gas is set to 80-100 m³ / h, the hot mode is started, and the molten steel is oxygenated. According to the oxygenation situation, oxygen is blown into the molten steel with a top gun until the carbon-oxygen balance is reached, and the vacuum degree is controlled at 10-30 mbar; (5) After the oxygen blowing is completed, the gas setting is increased to 160-180m³ / h, and the cold mode is started. When the vacuum degree is ≤3mbar and lasts for 2-3min, the molten steel is oxygenated. When the oxygen content in the molten steel is between 60-120ppm, the molten steel has been treated.

[0012] Furthermore, the mass of sintered ore added to each ton of molten steel is 1.45~2.5kg.

[0013] Furthermore, the FeO-containing metal material in step (2) is sintered ore.

[0014] Furthermore, the gas used for the lifting gas is argon.

[0015] Beneficial Effects The present invention adds metal materials to directly increase oxygen to molten steel during RH vacuum treatment, optimizes the vacuum degree of vacuum chamber circulation and the circulation gas process, reduces Fe reduction in metal materials through carbon oxygen reduction, reduces oxygen enrichment time during vacuum oxygen blowing, reduces vacuum treatment cycle, reduces steel material consumption and power consumption, and reduces high oxidation corrosion time in vacuum chamber, improves resistant material corrosion in vacuum chamber; through comparative analysis, the vacuum treatment cycle of the present invention is reduced from 18min to 11min, steel material consumption is reduced by 0.3kg / t, and process power consumption is reduced by 1kwh / t. The profit per ton of steel is about 2 yuan / t. DETAILED DESCRIPTION

[0016] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0017] The molten steel in the present invention refers to molten steel tapped from a converter. The amounts of molten steel in Example 1 to Comparative Example 2 are 305t, 302t, 303t, 301t, and 305t, respectively. The gas used for degassing in the following Examples and Comparative Examples is argon.

[0018] The FeO-containing metal material is a sintered ore, and its mass percentage composition is: FeO 69%, H2O≤1%, the remaining components are SiO28%, CaO 15%, MgO 3%, and other impurities <5%.

[0019] Example 1 (1) When vacuum treatment begins, the gas is set to 80 m³ / h and the vacuum cooling mode is started; (2) At the 3rd minute of vacuum treatment, the boost gas was set to 80 m³ / t, the hot mode was started, 600 kg of sintered ore was added to the molten steel, the oxygen addition amount reached 200 ppm, and the vacuum degree was controlled at 10-30 mbar; (3) At the 5th minute of vacuum treatment, the gas flow rate was set to 140 m³ / h, the cold mode was started, and the vacuum degree was controlled to ≤4 mbar.

[0020] (4) At the 7th minute of vacuum treatment, the gas is set to 80 m³ / h, the hot mode is started, and the molten steel is oxygenated. According to the oxygenation situation, 30 m³ of oxygen is blown into the molten steel, and the oxygen is increased by 100 ppm until the carbon-oxygen balance is reached. The vacuum degree is controlled at 10-30 mbar; (5) After the oxygen blowing is completed, the gas setting is increased to 180m³ / h, and the cold mode is started. When the vacuum degree is ≤3mbar and lasts for 2min, the molten steel is oxygenated. When the oxygen content in the molten steel is 100ppm, the molten steel has been treated.

[0021] Example 2 (1) Start of vacuum treatment: Set the gas to 80m³ / h and start the vacuum cooling mode; (2) At the 3rd minute of vacuum treatment, the boost gas was set to 80 m³ / t, the hot mode was started, 750 kg of sintered ore was added to the molten steel, the oxygen addition amount reached 250 ppm, and the vacuum degree was controlled at 10-30 mbar; (3) At the 5th minute of vacuum treatment, the gas flow rate was set to 140 m³ / h, the cold mode was started, and the vacuum degree was controlled to ≤4 mbar.

[0022] (4) At the 7th minute of vacuum treatment, the gas is set to 80 m³ / h, the hot mode is started, and the molten steel is oxygenated. According to the oxygenation situation, 15 m³ of oxygen is blown into the molten steel, and the oxygen is increased by 50 ppm until the carbon-oxygen balance is reached. The vacuum degree is controlled at 10-30 mbar; (5) After the oxygen blowing is completed, the gas setting is increased to 180m³ / h, and the cold mode is started. When the vacuum degree is ≤3mbar and lasts for 2min, the molten steel is oxygenated. When the oxygen content in the molten steel is 90ppm, the molten steel has been treated.

[0023] Example 3 (1) Start of vacuum treatment: Set the gas to 80m³ / h and start the vacuum cooling mode; (2) At the 3rd minute of vacuum treatment, the boost gas was set to 80 m³ / t, the hot mode was started, 450 kg of sintered ore was added to the molten steel, the oxygen addition amount reached 150 ppm, and the vacuum degree was controlled at 10-30 mbar; (3) Vacuum treatment for 5 minutes, set the boost gas to 140m³ / h, start the cold mode, and control the vacuum degree to ≤4mbar.

[0024] (4) At the 7th minute of vacuum treatment, the gas is set to 80 m³ / h, the hot mode is started, and the molten steel is oxygenated. According to the oxygenation situation, 45 m³ of oxygen is blown into the molten steel, and the oxygen is increased by 150 ppm until the carbon-oxygen balance is reached. The vacuum degree is controlled at 10-30 mbar; (5) After the oxygen blowing is completed, the gas setting is increased to 180m³ / h, and the cold mode is started. When the vacuum degree is ≤3mbar and lasts for 2min, the molten steel is oxygenated. When the oxygen content in the molten steel is between 90ppm, the molten steel has been treated.

[0025] Comparative Example 1 Different from Example 1, in Comparative Example 1, no sintered ore is added, and oxygen is only added by blowing oxygen through the top gun. The specific steps are as follows: (1) Vacuum treatment begins, the gas is set to 100m³ / h, and the vacuum cooling mode is started; (2) Vacuum treatment at the 3rd minute: set the boost gas to 120 m³ / t, start the thermal mode, and control the vacuum degree to 10-30 mbar; (3) 5th minute of vacuum treatment: Set the gas flow rate to 150 m³ / h, start the cold mode, and control the vacuum degree to ≤4 mbar.

[0026] (4) 7th minute of vacuum treatment: the gas is set to 80 m³ / h, the hot mode is started, and the molten steel is oxygenated. According to the oxygenation situation, 90 m³ of oxygen is blown into the molten steel, the oxygen is increased by 300 ppm, and the vacuum degree is controlled at 10-30 mbar; (5) After the oxygen blowing is completed, the gas setting is increased to 150m³ / h, and the cold mode is started. When the vacuum degree is ≤3mbar and lasts for 6min, the molten steel is oxygenated. When the oxygen content in the molten steel is 150ppm, the molten steel is treated.

[0027] Comparative Example 2 Different from Example 1, Comparative Example 2 changes the timing of adding sintered ore, and the specific operation is as follows: (1) Start of vacuum treatment: Set the gas to 80m³ / h and start the vacuum cooling mode; (2) At the 3rd minute of vacuum treatment: set the gas flow rate to 80 m³ / h, start the hot mode, and perform oxygen determination on the molten steel. According to the oxygen determination conditions, blow 30 m³ of oxygen into the molten steel, increase the oxygen by 100 ppm, and control the vacuum degree at 10-30 mbar. At the end of oxygen blowing: set the gas flow rate to 180 m³ / h, start the cold mode, and wait until the vacuum degree is ≤3 mbar for 2 minutes.

[0028] (3) Vacuum treatment at minute 7: Set the boost gas to 80 m³ / t, start the hot mode, add 750 kg of sintered ore to the molten steel, increase the oxygen content to 250 ppm, and control the vacuum degree to 10-30 mbar; (4) At the 12th minute of vacuum treatment: the gas is set to 140 m³ / h, the cold mode is started, the vacuum degree is controlled to ≤ 4 mbar, and it is maintained for 6 minutes. The oxygen content in the molten steel is 120 ppm, and the molten steel treatment is completed.

[0029] The vacuum treatment time, steel material consumption, and electricity consumption during the RH vacuum refining process of Examples 1 to 3 and Comparative Examples 1 to 2 were analyzed, and the results are shown in Table 1 below: Table 1 .

Claims

1. A method for reducing the vacuum treatment cycle by adding metal material to an RH vacuum furnace, characterized in that: During the RH vacuum refining process, FeO-containing metal materials are added into the vacuum chamber of the RH vacuum furnace for direct oxygenation, and then the molten steel is oxygenated. Oxygen is blown into the molten steel through a top gun according to the oxygen determination conditions. After the top gun oxygen blowing is completed, the molten steel is oxygenated until the oxygen content in the molten steel reaches 60-120ppm.

2. The method for reducing the vacuum treatment cycle by adding metal material to an RH vacuum furnace according to claim 1, characterized in that: The mass percentage of FeO in the FeO-containing metal material is 50-70%, and H2O≤1%.

3. The method for reducing the vacuum treatment cycle by adding metal material to the RH vacuum furnace according to claim 1, characterized in that: The specific operation of RH vacuum refining is: (1) Start of vacuum treatment: Increase the gas setting to 60-80m³ / h and start the vacuum cooling mode; (2) During the 2.5-3.5 minutes of vacuum treatment, the gas is set to 80-100 m³ / t, the hot mode is started, and metal materials containing FeO are added to the molten steel. The vacuum degree is controlled at 10-30 mbar. (3) During the 4.5-5.5 minutes of vacuum treatment, set the boost gas to 140-160 m³ / h, start the cold mode, and control the vacuum degree to ≤4 mbar. (4) At the 6.5-7.5 minute mark of vacuum treatment, the gas is set at 80-100 m³ / h, the hot mode is started, and oxygen is determined in the molten steel. According to the oxygen determination conditions, oxygen is blown into the molten steel with a top gun until the carbon-oxygen balance is reached, and the vacuum degree is controlled at 10-30 mbar; (5) After the oxygen blowing is completed, the gas setting is increased to 160-180m³ / h, and the cold mode is started. When the vacuum degree is ≤3mbar and lasts for 2-3min, the molten steel is oxygenated. When the oxygen content in the molten steel is between 60-120ppm, the molten steel has been treated.

4. The method for reducing the vacuum treatment cycle by adding metal material to an RH vacuum furnace according to claim 3, characterized in that: The specific operation of RH vacuum refining is: (1) Start of vacuum treatment: Increase the gas setting to 60-80m³ / h and start the vacuum cooling mode; (2) Vacuum treatment at the 3rd minute: Set the gas pressure to 80-100 m³ / t, start the hot mode, add FeO-containing metal material to the molten steel, and control the vacuum degree to 10-30 mbar; (3) 5 minutes of vacuum treatment: Set the gas flow rate to 140-160 m³ / h, start the cold mode, and control the vacuum degree to ≤4 mbar. (4) At the 7th minute of vacuum treatment, the gas is set to 80-100 m³ / h, the hot mode is started, and the molten steel is oxygenated. According to the oxygenation situation, oxygen is blown into the molten steel with a top gun until the carbon-oxygen balance is reached, and the vacuum degree is controlled at 10-30 mbar; (5) After the oxygen blowing is completed, the gas setting is increased to 160-180m³ / h, and the cold mode is started. When the vacuum degree is ≤3mbar and lasts for 2-3min, the molten steel is oxygenated. When the oxygen content in the molten steel is between 60-120ppm, the molten steel has been treated.

5. The method for reducing the vacuum treatment cycle by adding metal material to an RH vacuum furnace according to claim 3, characterized in that: The mass of sintered ore added to each ton of molten steel is 1.45~2.5kg.

6. The method for reducing the vacuum treatment cycle by adding metal material to an RH vacuum furnace according to claim 1, characterized in that: The FeO-containing metal material in step (2) is sintered ore.

7. The method for reducing the vacuum treatment cycle by adding metal material to an RH vacuum furnace according to claim 1, characterized in that: The gas used for the lifting gas is argon.