Smelting control method for ultralow manganese steel

Abstract

The invention discloses a smelting control method for ultralow manganese steel, and belongs to the technical field of steelmaking and smelting. The method comprises the following steps: (1) taking molten iron and scrap steel as raw materials, and smelting by a converter single-slag method; (2) a bottom gun controls the supply intensity of bottom blowing argon, lime is added in the bottom blowing process, and the alkalinity of the converter is controlled to be 2.5-3.5; (3) adding a demanganizing agent; (4) carrying out zero-position stirring after lifting the gun; (5) the final temperature of the converter is controlled to be 1620-1650 DEG C, the final oxygen value is larger than or equal to 0.06%, and the final manganese value is controlled to be 0.03% or below; (6) a demanganizing agent and lime are added in the tapping process for further demanganizing, and manganese is controlled to be 0.025% or below; and (7) oxidizing slag is produced in an LF furnace, a demanganizing agent is added, heating, argon blowing and stirring are carried out, further demanganizing is carried out, and the manganese content can be controlled to be 0.02% or below. According to the method, molten steel manganese can be stably controlled to be 0.02% or below, and the manufacturing rate of the ultra-low manganese steel is increased.

Description

Technical Field

[0001] This invention relates to the field of steelmaking and smelting technology, and in particular to a method for controlling the smelting of ultra-low manganese steel. Background Art

[0002] Manganese is generally a beneficial element in steel. However, for industrial pure iron steels, in addition to controlling the content of sulfur (S), phosphorus (P), and other impurities as much as possible, the manganese content also needs to be kept at a very low level. Typically, the manganese content at the converter endpoint is required to be ≤0.03%, and the finished product manganese content is controlled below 0.02%. Because the demanganese removal capacity of LF furnaces and RH refining processes is limited, demanganese removal becomes one of the important tasks in the steelmaking process when producing industrial pure iron steels.

[0003] When the manganese content in molten iron is between 0.05% and 0.15%, the converter can achieve one-shot over-oxidation tapping, but the final manganese content in the converter is controlled at around 0.05%. However, demanganese removal in the LF furnace remains difficult, and the yield rate for steel with manganese content below 0.02% remains low. Therefore, there is an urgent need to develop a smelting method to improve the yield of ultra-low manganese steel. Summary of the Invention

[0004] To address the problems of existing technologies, this invention provides a smelting control method for ultra-low manganese steel, which improves the demanganese removal efficiency in converter smelting, achieves stable control of manganese content at the converter endpoint below 0.03%, and controls the finished product manganese content below 0.02%, thereby increasing the yield of ultra-low manganese steel.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A method for controlling the smelting of ultra-low manganese steel, including converter smelting and LF refining;

[0007] The converter smelting process includes the following steps:

[0008] (1) Smelting using molten iron and scrap steel as raw materials in a converter single slag process; wherein, by mass percentage, the mass of scrap steel accounts for 15% to 25% of the total mass of molten iron and scrap steel.

[0009] (2) The bottom-blowing argon gas supply intensity is controlled by the bottom gun to be 0.04~0.06 Nm. 3 / min, time is 12-15min;

[0010] Lime is added during the bottom blowing process, with an addition amount of 30-40 kg / t steel. The basicity R of the converter is controlled at 2.5-3.5 to ensure that the slag is thoroughly melted and contains an appropriate amount of FeO. If the FeO is too low, the slag cannot be melted well and obviously cannot be demanganese. However, if the FeO is too high, it will dilute the demanganese removal effect of CaO.

[0011] (3) Add a manganese removal agent. The amount of manganese removal agent added during the smelting process is 10-12 kg / t steel, preferably 11.5 kg / t steel;

[0012] (4) After lifting the lance, stir at zero position for 2–4 minutes, and control the bottom-blown argon gas supply intensity at 0.08–0.12 Nm. 3 / min, increase stirring;

[0013] (5) The final temperature of the converter is controlled at 1620-1650℃, the final oxygen value is ≥0.06%, preferably 0.06%-0.08%, and the final manganese value is controlled below 0.03%;

[0014] (6) During the tapping process, demanganese remover and lime are added. The amount of demanganese remover added is 2-4 kg / t steel, and the amount of lime added is 2-3 kg / t steel. Argon is blown and stirred for 2-4 minutes during tapping, and the argon flow rate is 0.6-1.2 Nm³. 3 / min, slag washing process, further demanganese removal.

[0015] In the LF refining process, oxidized slag is generated in the LF furnace, and 2-4 kg / t of steel is added as a demanganese agent. The mixture is then boiled and heated, and argon is blown and stirred to remove manganese at a flow rate of 1.0-1.6 Nm³. 3 The process involves removing manganese at a rate of 10-20 min and a discharge temperature of 1615-1625℃.

[0016] Furthermore, in step (1), the scrap steel is low-sulfur scrap steel with a sulfur content ≤0.010% by mass.

[0017] Furthermore, in step (2), the lime can be added in 2 to 3 batches. For example, when the lime is added in 3 batches, the mass ratio of the first batch of lime, the second batch of lime and the third batch of lime is 4:(3-4):1.

[0018] Furthermore, in step (2), magnesite can also be added at a rate of 6-10 kg / t steel to protect the furnace lining. The magnesite can be added all at once.

[0019] Furthermore, in step (2), the converter process temperature is controlled at 1570℃~1620℃, and the carbon content is controlled at 0.20%~0.70%.

[0020] Furthermore, the converter has ≥2 bottom guns, and the converter is selected to have ≥2 visible bottom guns for production.

[0021] Furthermore, the manganese-removing agent is sintered ore, and the mass content of iron oxide in the manganese-removing agent is ≥60%.

[0022] Furthermore, based on mass content, the slag system inside the converter is controlled as follows:

[0023] slag components FeO CaO MgO <![CDATA[SiO2]]> other content,% 15～25 40～50 5～10 10～20 5～10

[0024] Furthermore, based on mass content, the LF slag system is controlled as follows:

[0025] slag components FeO CaO MgO <![CDATA[SiO2]]> other content,% 25～35 35～45 5～10 5～10 5～10

[0026] Furthermore, the method also includes RH refining.

[0027] Furthermore, the manganese content in each process is controlled as follows:

[0028] Process molten iron Converter end point Entering the LF furnace LF furnace RH Refining Finished product Manganese content, % 0.05～0.15 ≤0.03 ≤0.025 ≤0.02 ≤0.02 ≤0.02

[0029] Furthermore, during the RH refining process, the RH deep vacuum time is 10-15 min, the residual oxygen is 0.025%-0.035%, and the aluminum is cast after being killed; wherein, the amount of aluminum added during aluminum killing is 4-6 kg / t steel.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention solves the problem of low manganese yield in the production of ultra-low manganese steel. The invention employs low temperature, high oxidizing properties, and high basicity as principles in the smelting of ultra-low manganese steel. It improves the manganese removal efficiency of converter smelting in terms of molten iron, scrap steel, converter, basicity, materials, endpoint control, and slag system control, achieving stable control of the converter's final manganese content below 0.03%. Furthermore, the LF furnace further reduces the manganese content in the molten steel through high-oxidizing slag and argon blowing stirring processes, controlling the finished product manganese content below 0.02%, thus improving the yield of ultra-low manganese steel. DETAILED DESCRIPTION

[0032] The following embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0033] [Example 1]

[0034] This embodiment uses a 260t converter for smelting, and the steel grade is AGM6-2H industrial pure iron steel. The specific operation process is as follows:

[0035] The selected molten iron has a manganese content of 0.075% and a silicon content of 0.40%. 51.3 tons of low-sulfur scrap steel (S≤0.010%) was used. Production was carried out in a B converter with 6 bottom lances, and the bottom-blown argon gas supply intensity was 0.05 Nm. 3The slag material is quicklime, and the quicklime addition is calculated based on an alkalinity of 3.0, with a total quicklime addition of 8t. The first batch of quicklime (4t) and magnesite (2t) are added after 1.5 minutes of oxygen blowing. The second batch of quicklime (3t) is added after 3 minutes of oxygen blowing. At 12 minutes of oxygen blowing, the process temperature is 1592℃, and the process carbon content is 0.61%. At 13 minutes of oxygen blowing, the remaining quicklime (1t) and manganese removal agent (sinter) (3t) are added. After lifting the lance, zero-position stirring is performed for 3 minutes, with a bottom-blown argon gas supply intensity of 0.1 Nm. 3 The endpoint test was conducted at a rate of 1.0 Nm³ / min. The converter endpoint temperature was 1644℃, the endpoint oxygen value was 0.0692%, and the endpoint manganese content was 0.0283%. During tapping, 0.8 t of demanganese-removing agent (sintered ore) and 0.5 t of fine-grained quicklime were added, and the mixture was stirred with argon for 3 min at an argon flow rate of 1.0 Nm³ / min. 3 The manganese content is 0.022%. The LF furnace is heated for 10 minutes, then 0.8t of demanganese agent (sinter) is added, followed by argon blowing and stirring for 15 minutes at an argon flow rate of 1.5 Nm³ / min. 3 / min, LF furnace outlet temperature 1620℃, LF furnace outlet manganese 0.015%.

[0036] Among them, the control of the slag system in the converter at the end point:

[0037] slag components FeO CaO <![CDATA[SiO2]]> MgO other content,% 21.65 48.56 15.26 8.75 5.78

[0038] LF furnace refining top slag system control:

[0039] slag components FeO CaO <![CDATA[SiO2]]> MgO other content,% 32.51 42.81 8.89 5.91 9.88

[0040] In this embodiment, the initial manganese content is 0.075%, the manganese content in the molten steel produced by the converter is 0.0283%, and the manganese content in the steel removed from the LF furnace is 0.015%, which meets the requirement of manganese content control of ≤0.02% for steel grades.

[0041] [Example 2]

[0042] This embodiment uses a 260t converter for smelting, and the steel grade is AGM6-2H industrial pure iron steel. The specific operation process is as follows:

[0043] The selected molten iron has a manganese content of 0.070% and a silicon content of 0.47%. 50.99 tons of low-sulfur scrap steel (S≤0.010%) was used. Production was carried out in a B converter with 6 bottom lances and a bottom-blowing gas supply intensity of 0.05 Nm³. 3 / min. The slag material is quicklime. The quicklime addition is calculated based on an alkalinity of 3.0, with a total quicklime addition of 9t. The first batch of quicklime (4t) and magnesite (2t) are added after 1.5 minutes of oxygen blowing. The second batch of quicklime (4t) is added after 3 minutes of oxygen blowing. At 12.5 minutes of oxygen blowing, the process temperature is 1600℃, and the process carbon content is 0.33%. At 13.5 minutes of oxygen blowing, the remaining quicklime (1t) and demanganese-removing agent (sinter) (3t) are added. After lifting the lance, zero-position stirring is performed for 3 minutes, with a bottom-blowing air supply intensity of 0.1 Nm. 3 The endpoint test was conducted at a rate of 1.0 Nm³ / min. The converter endpoint temperature was 1633℃, the endpoint oxygen value was 0.0676%, and the endpoint manganese content was 0.0203%. During tapping, 0.8 t of demanganese agent (sintered ore) and 0.5 t of quicklime were added, and argon was blown and stirred for 3 min at a flow rate of 1.0 Nm³ / min. 3 The manganese content is 0.024%. The LF furnace is heated for 12 minutes, then 0.8t of demanganese agent (sinter) is added, followed by argon blowing and stirring for 10 minutes at an argon flow rate of 1.5 Nm³ / min. 3 / min, LF furnace outlet temperature 1620℃, LF furnace outlet manganese 0.012%.

[0044] Among them, the control of the slag system in the converter at the end point:

[0045] slag components FeO CaO <![CDATA[SiO2]]> MgO other content,% 23.45 45.85 14.6 9.12 6.98

[0046] LF furnace refining top slag system control:

[0047] slag components FeO CaO <![CDATA[SiO2]]> MgO other content,% 33.15 41.55 8.78 7.73 8.79

[0048] In this embodiment, the initial manganese content is 0.070%, the manganese content in the molten steel produced by the converter is 0.0203%, and the manganese content in the steel removed from the LF furnace is 0.012%, which meets the requirement of manganese content control of ≤0.02% for steel grades.

Claims

1. A method for controlling the smelting of ultra-low manganese steel, characterized in that, Including converter smelting and LF refining; The converter smelting process includes the following steps: (1) Smelting is carried out using molten iron and scrap steel as raw materials in a converter single slag process; wherein, by mass percentage, the mass of scrap steel accounts for 15%-25% of the total mass of molten iron and scrap steel. (2) The bottom-blowing argon gas supply intensity is controlled by the bottom gun to be 0.04~0.06 Nm. 3 / min, time is 12-15min; Lime is added during the bottom blowing process, with an addition amount of 30-40 kg / t steel, to control the converter basicity at 2.5-3.

5. (3) Add manganese removal agent. The amount of manganese removal agent added during the smelting process is 10-12 kg / t steel; (4) After lifting the lance, stir at zero position for 2–4 minutes, and control the bottom-blown argon gas supply intensity at 0.08–0.12 Nm. 3 / min; (5) The final temperature of the converter is controlled at 1620-1650℃, the final oxygen value is ≥0.06%, and the final manganese value is controlled below 0.03%; (6) During the tapping process, a demanganese remover and quicklime are added. The amount of demanganese remover added is 2-4 kg / t of steel, and the amount of quicklime added is 2-3 kg / t of steel. Argon is blown and stirred for 2-4 minutes during tapping, and the argon flow rate is 0.6-1.2 Nm³. 3 / min; In the LF refining process, oxidized slag is generated in the LF furnace, and 2-4 kg / t of steel is added as a demanganese agent. The mixture is then boiled and heated, and argon is blown and stirred to remove manganese at a flow rate of 1.0-1.6 Nm³. 3 / min, time is 10 to 20 min, and the outlet temperature is 1615 to 1625℃.

2. The method according to claim 1, characterized in that, In step (1), the manganese content in the molten iron is 0.05% to 0.15% by mass; the scrap steel is low-sulfur scrap steel with a sulfur content ≤0.010% by mass.

3. The method according to claim 1, characterized in that, In step (2), the slag is added in 2 to 3 batches.

4. The method according to claim 1, characterized in that, In step (2), magnesite is also added, with an addition amount of 6-10 kg / t steel.

5. The method according to claim 1, characterized in that, In step (2), the converter process temperature is controlled at 1570-1620℃ and the carbon content is controlled at 0.20%-0.70%.

6. The method according to claim 1, characterized in that, The converter has ≥2 bottom lances.

7. The method according to claim 1, characterized in that, The manganese removal agent is sintered ore, and the mass content of iron oxide in the manganese removal agent is ≥60%.

8. The method according to claim 1, characterized in that, The slag system inside the converter is controlled as follows, based on mass content: FeO 15%–25%, CaO 40%–50%, SiO2 10%–20%, MgO 5%–10%, others 5%–10%; The LF slag system is controlled as follows, based on mass content: FeO 25%–35%, CaO 35%–45%, SiO2 5%–10%, MgO 5%–10%, others 5%–10%; During the LF refining process, the mass content of manganese entering the LF furnace is ≤0.03%, and the mass content of manganese exiting the LF furnace is ≤0.02%.

9. The method according to claim 1, characterized in that, The method also includes RH refining, in which the mass content of manganese is ≤0.02%.

10. The method according to claim 9, characterized in that, During the RH refining process, the RH vacuum time is 10-15 min, the residual oxygen is 0.025%-0.035%, and the aluminum is cast after being killed; wherein, the amount of aluminum added during aluminum killing is 4-6 kg / t steel.