Nb-containing steel and method for improving niobium recovery rate in niobium-containing steel with low molten iron consumption

Abstract

The application discloses a niobium-containing steel and a method for improving niobium yield in niobium-containing steel under low molten iron consumption. The method for improving niobium yield in niobium-containing steel under low molten iron consumption comprises the following steps: placing a mixture containing molten iron and first scrap steel in a converter for smelting, performing deoxidation and alloying under a non-active atmosphere during tapping of the converter, adding 60%-80% of niobium iron, and obtaining molten steel after the tapping is completed; placing a mixture containing the molten steel and second scrap steel in an LF furnace for refining, performing deoxidation and slagging desulfurization treatment during the refining, adding the remaining niobium iron, and obtaining the niobium-containing steel; wherein the weight ratio of the first scrap steel to the molten iron is 1:3-5, and the weight ratio of the second scrap steel to the molten steel is 1:6-8. According to the embodiment of the application, the niobium yield in the niobium-containing steel under low molten iron consumption can be improved.

Description

Technical Field

[0001] This application belongs to the field of iron and steel smelting technology, and in particular relates to a method for improving the niobium yield in niobium-containing steel under low molten iron consumption. Background Technology

[0002] Niobium is a transition metal element with good ductility and superconductivity. Its most important application is in the steel industry, where 85%-90% of the world's niobium is used as an alloying element in steelmaking in the form of ferroniobium. Adding niobium to molten steel can refine the grain size, increase the strength of the steel, and simultaneously improve its toughness, resistance to high-temperature oxidation, and corrosion resistance, giving the steel good weldability and formability.

[0003] In the smelting of niobium-containing steel, about 5%-15% of the niobium is lost due to dust, steel slag encapsulation, or oxidation by molten steel and steel slag. Especially under low iron consumption conditions, i.e., when the consumption per ton of molten steel is low, a large amount of scrap steel is added to the converter and LF furnace, which allows a large amount of free oxygen to enter the molten steel, causing niobium to be oxidized. At the same time, the addition of a large amount of scrap steel will increase the amount of refining slag in order to deoxidize and control nitrogen, increasing the probability that ferroniobium will be adsorbed or encapsulated by steel slag, further reducing the niobium yield and increasing the smelting cost. Summary of the Invention

[0004] This application provides a method for improving the niobium yield in niobium-containing steel under low molten iron consumption, which can improve the niobium yield in niobium-containing steel under low molten iron consumption.

[0005] In the first aspect, embodiments of this application provide a method for improving the niobium yield in niobium-containing steel with low molten iron consumption.

[0006] A method for improving niobium yield in niobium-containing steel with low iron consumption includes the following steps:

[0007] The mixture containing molten iron and first scrap steel is placed in a converter for smelting. During the tapping process in the converter, deoxidation and alloying are carried out first in an inactive atmosphere, and then 60%-80% ferroniobium is added. After tapping, molten steel is obtained.

[0008] The mixture containing molten steel and second scrap steel is placed in an LF furnace for refining. During the refining process, deoxidation, slag formation and desulfurization are carried out first, and then the remaining ferroniobium is added to obtain niobium-containing steel.

[0009] The weight ratio of the first scrap steel to molten iron is 1:3-5, the weight ratio of the second scrap steel to molten steel is 1:6-8, and the amount of niobium iron added is calculated based on the niobium content of the niobium-containing steel and the weight of the molten steel in the LF furnace.

[0010] In any embodiment of this application, in the step of smelting a mixture containing molten iron and a first scrap steel in a converter, the inactive atmosphere includes at least one of argon, neon, and helium.

[0011] In any embodiment of this application, during the deoxidation and alloying process of the step of smelting a mixture containing molten iron and first scrap steel in a converter, the flow rate of the inactive atmosphere is 500-800 NL / min.

[0012] In any embodiment of this application, when adding ferroniobium after deoxidation and alloying in a converter during the step of smelting a mixture containing molten iron and first scrap steel, the flow rate of the inactive atmosphere is 200-400 NL / min.

[0013] In any embodiment of this application, in the step of smelting a mixture containing molten iron and a first scrap steel in a converter, deoxidation alloying includes adding at least one of silicon-based, manganese-based, and aluminum-based alloys to the mixture.

[0014] In any embodiment of this application, in the step of refining the mixture containing molten steel and second scrap steel in an LF furnace, the remaining ferroniobium is added when the temperature of the molten steel is above 1560°C.

[0015] In any embodiment of this application, in the step of refining the mixture containing molten steel and second scrap steel in an LF furnace, after adding the remaining ferroniobium, the process further includes wire feeding and soft blowing treatment.

[0016] In any embodiment of this application, the niobium yield is 97%-99%.

[0017] Secondly, embodiments of this application provide a niobium-containing steel.

[0018] A niobium-containing steel is obtained using the method described above.

[0019] In any embodiment of this application, the niobium content in the niobium-containing steel is 0.02%-0.04%.

[0020] The method for improving niobium yield in niobium-containing steel under low molten iron consumption in this application embodiment involves adding ferroniobium to the converter and LF furnace in batches. 60%-80% of the ferroniobium is added during converter tapping, taking advantage of the high tapping temperature and low slag volume to improve the yield. Simultaneously, the remaining small portion is added to the LF furnace, allowing for fine-tuning of the niobium content and preventing substandard composition. Furthermore, ferroniobium is added after deoxidation alloying and deoxidation, slag formation, and desulfurization treatments to prevent oxidation by free oxygen, further improving the yield. Detailed Implementation

[0021] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0022] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0023] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0024] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0025] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0026] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0027] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0028] Unless otherwise specified, this application uses conventional testing methods or testing methods recommended by the instrument.

[0029]

[0030] Since converter steelmaking uses blast furnace hot metal as its main raw material, steel feedstock consumption has become an important economic and technical indicator for steel plants, generally accounting for 80%-85% of converter costs. Therefore, reducing steel feedstock consumption—low hot metal consumption per unit—has become a major means for steel plants to reduce costs.

[0031] Scrap steel is an important component of metal materials in the converter smelting process, and increasing the scrap steel ratio in the converter can reduce the consumption per ton of molten steel. However, in the existing technology, when the scrap steel ratio is increased from 10.27% to 14.65%, it will cause all the indicators of converter smelting to decline, while increasing the difficulty of achieving a high alloy yield.

[0032] This application proposes to improve the niobium yield by controlling the order and amount of ferroniobium addition under special low iron consumption conditions, without reducing various indicators in converter smelting.

[0033] Methods to improve niobium yield in niobium-containing steel

[0034] A method for improving niobium yield in niobium-containing steel with low iron consumption includes the following steps:

[0035] The mixture containing molten iron and first scrap steel is placed in a converter for smelting. During the tapping process in the converter, deoxidation and alloying are carried out first in an inactive atmosphere, and then 60%-80% ferroniobium is added. After tapping, molten steel is obtained.

[0036] The mixture containing molten steel and second scrap steel is placed in an LF furnace for refining. During the refining process, deoxidation, slag formation and desulfurization are carried out first, and then the remaining ferroniobium is added to obtain niobium-containing steel.

[0037] The weight ratio of the first scrap steel to molten iron is 1:3-5, the weight ratio of the second scrap steel to molten steel is 1:6-8, and the amount of niobium iron added is calculated based on the niobium content of the niobium-containing steel and the weight of the molten steel in the LF furnace.

[0038] Iron consumption per unit refers to the amount of molten iron consumed per ton of qualified steel billet. Low iron consumption per unit means that a certain amount of scrap steel needs to be introduced.

[0039] During the converter tapping process, inactive gas can be blown into the bottom of the ladle throughout the process to agitate the steel. After the converter tapping is completed, the molten steel can be hoisted to the LF furnace for refining, and the molten steel is heated before the second scrap steel is added.

[0040] The ratio of scrap steel to molten iron in the converter is 1:3-1:5. If the ratio is too low, less scrap steel will be added, and the heat of the molten iron cannot be fully utilized. If the ratio is too high, more scrap steel will be added, which will result in insufficient heat of the molten iron, requiring excessive oxygen blowing or the addition of heating agents, thus increasing costs.

[0041] The ratio of scrap steel added to LF furnace to molten steel output from converter is 1:6-1:8. If the amount of scrap steel added is too small, it will not be conducive to increasing output and efficiency; if the amount of scrap steel added is too large, it will prolong the smelting time of molten steel.

[0042] The amount of ferroniobium added during converter tapping is 60%-80% of the estimated LF steel weight and the target niobium content of the steel grade. For example, when the weight of the molten steel after slag formation and desulfurization in the LF furnace is 200 tons, and the target niobium content in the niobium-containing steel is 0.0200%, the amount of ferroniobium added in the converter can increase the niobium content of the molten steel by 0.0120%-0.0160%, with an estimated niobium recovery rate of 96%. The amount of ferroniobium added in the converter is 38-51 kg. The high temperature and low slag volume during converter tapping ensure sufficient dissolution of ferroniobium and reduce adsorption by the steel slag. On the one hand, adding most of the ferroniobium during converter tapping helps improve the recovery rate. On the other hand, adding a small portion of ferroniobium in the LF furnace allows for fine-tuning of the niobium content, avoiding inaccurate steel weight estimations due to newly added scrap steel in the LF furnace. It also prevents the introduction of free oxygen that could cause secondary oxidation of niobium, resulting in substandard niobium content in the finished steel.

[0043] In the refining process of a mixture containing molten steel and second scrap steel in an LF furnace, ferroniobium is added after the deoxidation, slag formation and desulfurization treatments are performed during the refining process. At this time, the free oxygen content in the molten steel is at its lowest, which can reduce the oxidation of niobium and increase the niobium yield.

[0044] In some embodiments, in the step of smelting a mixture containing molten iron and a first scrap steel in a converter, the inactive atmosphere includes at least one of argon, neon, and helium.

[0045] In some embodiments, during the deoxidation and alloying process of smelting a mixture containing molten iron and first scrap steel in a converter, the flow rate of the inactive atmosphere is 500-800 NL / min. Within this range, rapid deoxidation of the alloy and timely flotation of oxide inclusions can be ensured, thereby improving the ferroniobium yield.

[0046] In some embodiments, during the step of smelting a mixture containing molten iron and a first scrap steel in a converter, when adding ferroniobium after deoxidation and alloying, the flow rate of the inactive atmosphere is 200-400 NL / min. After deoxidation and alloying, the flow rate of the inactive atmosphere needs to be reduced. Within this range, sufficient dissolution of ferroniobium in the molten steel can be ensured, while avoiding losses caused by air oxidation of niobium in the molten steel due to excessive tumbling of the steel.

[0047] In some embodiments, during the step of smelting a mixture containing molten iron and a first scrap steel in a converter, deoxidation alloying includes adding at least one of silicon-based, manganese-based, and aluminum-based alloys to the mixture. This can reduce the free oxygen content in the molten steel, reduce niobium oxidation, and improve yield.

[0048] In some embodiments, during the refining step of placing the mixture containing molten steel and second scrap steel in an LF furnace, the remaining ferroniobium is added when the molten steel temperature is above 1560°C. This allows the ferroniobium to diffuse and dissolve rapidly upon entering the molten steel, improving the yield.

[0049] In some embodiments, during the step of refining a mixture containing molten steel and a second scrap steel in an LF furnace, a weighing device is installed on the LF furnace ladle car, which can accurately display the weight of the molten steel after the addition of scrap steel, thereby improving the accuracy of the amount of ferroniobium added.

[0050] In some embodiments, the step of refining a mixture containing molten steel and second scrap steel in an LF furnace, after adding the remaining ferroniobium, further includes wire feeding and soft blowing treatment.

[0051] In some embodiments, the niobium recovery rate is 97%-99%.

[0052] Niobium-containing steel

[0053] A niobium-containing steel is obtained using the method described above.

[0054] In some embodiments, the niobium content in the niobium-containing steel is 0.02%-0.04%.

[0055] Niobium-containing steel is widely used in automobiles, bridges, oil pipelines, natural gas pipelines, oil drilling, offshore oil drilling platforms, railway tracks, and as reinforcing steel in civil engineering.

[0056] Example 1

[0057] In this embodiment, the smelting equipment is a nominal 210-ton converter, the niobium content in the ferroniobium is 65%, the niobium content in the niobium-containing steel is 0.03%-0.04%, and the target value is 0.035%.

[0058] (1) 160 tons of molten iron and 50 tons of scrap steel are poured into the converter for smelting. During the tapping process, the argon flow rate is first turned up to 600 NL / min, and 500 kg of silicon manganese and 100 kg of aluminum blocks are added for deoxidation and alloying. After adding, wait for 1 minute, then adjust the argon flow rate to 300 NL / min, and then add 90 kg of niobium iron. After tapping, the molten steel is hoisted to the LF furnace for refining.

[0059] (2) After the molten steel enters the LF furnace, it is first heated by submerged arc. After the molten steel is heated to 1600℃, the ladle car is driven to the scrap steel position and 30 tons of scrap steel are added. After the scrap steel is added, it is returned to the smelting position to heat up. Aluminum blocks and lime are added to form slag and desulfurize. Other alloys are added to meet the steel composition requirements. It is estimated that the molten steel will be heated to above 1560℃. Temperature is measured and samples are taken for analysis. At this time, the temperature of the molten steel is 1585℃, the niobium content is 0.0262%, and the weight of the molten steel is 219 tons. After calculation, 30 kg of ferroniobium is added. After 5 minutes, samples are taken for analysis. The niobium content is 0.0346%, and the composition is qualified. After wire feeding and soft blowing, the molten steel leaves the station.

[0060] Calculations show that the overall niobium recovery rate for this furnace is 97.1%.

[0061] Example 2

[0062] In this embodiment, the smelting equipment is a nominal 210-ton converter, the niobium content in the ferroniobium is 65%, the niobium content in the niobium-containing steel is 0.02%-0.03%, and the target value is 0.025%.

[0063] (1) 165 tons of molten iron and 45 tons of scrap steel were poured into the converter for smelting. During the tapping process, the argon flow rate was first turned up to 700 NL / min, and 300 kg of silicon manganese and 100 kg of aluminum blocks were added for deoxidation and alloying. After adding them, wait for 1 minute, then adjust the argon flow rate to 400 NL / min, and then add 70 kg of niobium iron. After tapping, the molten steel was hoisted to the LF furnace for refining.

[0064] (2) After the molten steel enters the LF furnace, it is first heated by submerged arc heating. After the molten steel reaches 1600℃, the ladle car is driven to the scrap steel position, and 25 tons of scrap steel are added. After the scrap steel is added, it returns to the smelting position to heat up, and aluminum blocks and lime are added to form slag and desulfurize. During the process, other alloys are added to meet the steel composition requirements. It is estimated that the molten steel will reach a temperature of over 1560℃. Temperature is measured and samples are taken for analysis. At this time, the molten steel temperature is 1580℃, the niobium content is 0.0210%, and the molten steel weight is 212 tons. After calculation, 10 kg of ferroniobium is added. After 5 minutes, samples are taken for analysis. The niobium content is 0.0239%, and the composition is qualified. After wire feeding and soft blowing, the molten steel leaves the station.

[0065] Calculations show that the overall niobium recovery rate for this furnace is 97.6%.

[0066] Example 3

[0067] In this embodiment, the smelting equipment is a nominal 210-ton converter, the niobium content in the ferroniobium is 65%, the niobium content in the niobium-containing steel is 0.03%-0.04%, and the target value is 0.035%.

[0068] (1) 170 tons of molten iron and 40 tons of scrap steel were poured into the converter for smelting. During the tapping process, the argon flow rate was first turned up to 700 NL / min, and 500 kg of silicon manganese and 100 kg of aluminum blocks were added for deoxidation and alloying. After adding them, wait for 1 minute, then adjust the argon flow rate to 300 NL / min, and then add 80 kg of niobium iron. After tapping, the molten steel was hoisted to the LF furnace for refining.

[0069] (2) After the molten steel enters the LF furnace, it is first heated by submerged arc. After the molten steel is heated to 1600℃, the ladle car is driven to the scrap steel position and 20 tons of scrap steel are added. After the scrap steel is added, it returns to the smelting position to heat up. Aluminum blocks and lime are added to form slag and desulfurize. Other alloys are added during the process to meet the steel composition requirements. It is estimated that the molten steel will be heated to above 1560℃. Temperature is measured and samples are taken for analysis. At this time, the temperature of the molten steel is 1590℃, the niobium content is 0.0246%, and the weight of the molten steel is 209 tons. After calculation, 30 kg of ferroniobium is added. Samples are taken for analysis 5 minutes later. The niobium content is 0.0337%, and the composition is qualified. After wire feeding and soft blowing, the molten steel leaves the station.

[0070] Calculations show that the overall niobium recovery rate for this furnace is 98.5%.

[0071] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A method for improving niobium recovery in niobium-bearing steel at a low iron unit consumption, characterized by, Includes the following steps: The mixture containing molten iron and first scrap steel is placed in a converter for smelting. During the tapping process in the converter, deoxidation and alloying are carried out first in an inactive atmosphere with a flow rate of 500-800 NL / min. Then, 60%-80% of ferroniobium is added with a flow rate of 200-400 NL / min. After tapping, molten steel is obtained. The mixture containing the molten steel and the second scrap steel is placed in an LF furnace for refining. During the refining process, deoxidation, slag formation and desulfurization are carried out first, and then the remaining ferroniobium is added to obtain the niobium-containing steel. The weight ratio of the first scrap steel to the molten iron is 1:3-5, the weight ratio of the second scrap steel to the molten steel is 1:6-8, and the amount of ferroniobium added is calculated based on the niobium content of the niobium-containing steel and the weight of the molten steel in the LF furnace.

2. The method of claim 1, wherein, In the step of smelting a mixture containing molten iron and first scrap steel in a converter, the inactive atmosphere includes at least one of argon, neon, and helium.

3. The method of claim 1, wherein, In the step of smelting a mixture containing molten iron and first scrap steel in a converter, deoxidation alloying includes adding at least one of silicon-based, manganese-based, and aluminum-based alloys to the mixture.

4. The method of claim 1, wherein, In the step of refining the mixture containing the molten steel and the second scrap steel in an LF furnace, the remaining ferroniobium is added when the temperature of the molten steel is above 1560 °C.

5. The method of claim 1, wherein, In the step of refining the mixture containing the molten steel and the second scrap steel in an LF furnace, after adding the remaining ferroniobium, the process also includes wire feeding and soft blowing treatment.

6. The method of claim 1, wherein, The niobium recovery rate is 97%-99%.

7. A niobium-containing steel, characterized in that, Obtained by the method described in any one of claims 1-6.

8. The niobium-containing steel according to claim 7, characterized in that, The niobium content in the niobium-containing steel is 0.02%-0.04%.

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