Production method of fiber steel
By optimizing converter smelting, post-furnace decarburization, LF refining, and continuous casting processes, and controlling alloying elements and process parameters, the problems of large fluctuations in fiber steel composition and unstable performance were solved, producing ultra-low strength and ultra-high ductility steel suitable for drawing, thereby improving production efficiency and reducing costs.
Patent Information
- Application Number
- CN202511149524.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-18
- Publication Date
- 2025-11-21
AI Technical Summary
Existing technologies struggle to produce fiber steel that combines ultra-low strength and ultra-high plasticity while being suitable for industrial production. They suffer from problems such as large fluctuations in composition and unstable performance, particularly in controlling the carbon, nitrogen, oxygen, sulfur content, and inclusions in the steel.
The process involves top and bottom blowing converter smelting, post-furnace decarburization, LF refining, continuous casting, and hot rolling. By controlling the addition of alloying elements and process parameters, including the use of iron oxide scale for decarburization, argon stirring, calcification treatment, and high-basicity covering agents, the vacuum decarburization process is avoided, ensuring the purity of molten steel and the purity of its microstructure.
It produces fiber steel with a tensile strength of less than 280MPa, an elongation at break of more than 50%, and a reduction of area of more than 80%, which is suitable for drawing fine filaments of less than 0.2mm, improving production stability and efficiency, and reducing the cost of vacuum processes.
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Figure CN120989490A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of metallurgical technology and relates to a method for producing fiber steel. Background Technology
[0002] Fiberglass steel is a special type of steel with ultra-high plasticity and ultra-low strength. Its core characteristics lie in its ferritic structure, which is close to that of pure iron, its extremely low tensile strength, and its excellent ductility in the hot-rolled state. This type of material has irreplaceable advantages in the field of drawing ultra-fine filaments (such as electronic wires with a diameter ≤0.2mm, medical microfilaments, etc.): the low strength can significantly reduce the wire breakage rate and equipment load during the drawing process, while the high plasticity ensures the forming stability and surface quality of the filament.
[0003] However, while existing industrially produced ultra-low carbon steels (such as IF steel and electrical steel) possess good plasticity, their tensile strength is generally higher than 300 MPa, and they cannot simultaneously meet the following key requirements:
[0004] The ultimate balance between strength and plasticity: Under conventional composition design, elements such as Si and Mn need to be added to control inclusions and precipitates in steel, which leads to increased strength; however, excessively reducing the C and N content faces technical challenges such as high smelting costs and easy carbon and nitrogen increase during continuous casting.
[0005] Tissue purity and sulfide control: In traditional processes, insufficient deoxidation or improper calcification can lead to the aggregation of Al2O3 inclusions, which become stress concentration points, induce microcracks, and impair drawing performance. When drawing fine wires (e.g., ≤0.2mm), the wire breakage rate soars. When the timing of sulfur content addition is not good, a lot of CaS inclusions will be generated, which seriously affects the smooth operation of continuous casting production. At the same time, when the sulfur content is insufficient (<0.030%), enough MnS plastic inclusions cannot be formed, making it difficult to guide the formation of fibrous structure during rolling.
[0006] Precise control of nitrogen content: When the nitrogen content in steel is >0.0050%, brittle phases such as AlN are easily formed, significantly reducing the reduction of area. However, in the existing converter-LF-continuous casting process, nitrogen control is difficult due to factors such as high-pressure nitrogen splashing for furnace protection, bottom-blown nitrogen stirring, and air intrusion. The converter-LF-RH / VD vacuum denitrification process, which involves raising the LF temperature to increase the steel temperature, causes the steel to absorb nitrogen, resulting in limited overall denitrification effect and a significant increase in production costs.
[0007] Process carbon increase risk: In conventional processes, problems such as electrode carbon increase during LF refining, use of carbonized rice husks as tundish covering agent, and carbon content in ladle / tundish refractory materials can easily lead to carbon increase in molten steel, resulting in excessive carbon content and increased strength in the finished product.
[0008] Therefore, there is an urgent need to develop a fiber steel that combines ultra-low strength and ultra-high plasticity and is suitable for industrial production. Furthermore, through a synergistic process design that controls carbon, nitrogen, and oxygen throughout the entire process, the problems of large composition fluctuations and unstable performance in existing technologies can be solved. Summary of the Invention
[0009] To achieve the above objectives, the present invention provides a method for producing fiber steel. Based on the influence of alloying elements on material properties and microstructure, and combined with existing equipment and process conditions, a fiber steel has been designed and developed, which solves the problems existing in the prior art.
[0010] The technical solution adopted in this invention is a method for producing fiber steel, including converter smelting, post-furnace decarburization, LF refining, continuous casting, hot rolling, and cooling processes.
[0011] The decarburization process after the furnace is as follows: during and after tapping, no alloys or deoxidizers are added. Instead, 1.5 kg / t of iron oxide scale is added and stirred with argon gas for 5 minutes. Decarburization is carried out using residual oxygen in the steel and oxygen introduced by the iron oxide scale. After decarburization to below 0.01%, the argon gas is turned off and alloys and slag washing materials are added.
[0012] The cooling process is as follows: after rolling, the material enters a slow cooling channel at a temperature above 750°C, the slow cooling time is above 30 minutes, the cooling rate is ≤0.3°C / s, and the temperature exiting the slow cooling channel is ≤300°C.
[0013] The fiber steel is composed of the following components by mass percentage: C≤0.03%; Si≤0.02%; Mn=0.10-0.20%; P≤0.015%; S≥0.030%; Al≥0.035%; N≤0.0030%; the remainder being Fe and unavoidable impurity elements.
[0014] Furthermore, the alloy and slag washing materials added in the post-furnace decarburization process are: 3 kg of aluminum-iron per t of steel, 1-1.5 kg of manganese-iron per t of steel, 300 kg of lime + 200 kg of synthetic slag.
[0015] Furthermore, the converter smelting process is as follows: a top-and-bottom blowing converter is used for smelting. No slag splashing operation is performed before smelting. The raw materials for converter smelting are: molten iron to scrap steel mass ratio = 5:1, total slag amount 15kg / t steel, lime to dolomite mass ratio = 5:4. In the later stage of converter smelting, no nitrogen-argon switching of bottom blowing gas is performed. Argon gas is used for bottom blowing throughout the process. Steel is tapped out in one pour without supplementary blowing. The tapping temperature is 1600-1660℃, and the final carbon content is ≤0.05%.
[0016] Furthermore, the LF refining process is as follows: the LF furnace uses a special carbon-free steel ladle, the smelting time is 60-80 minutes, the entire process is argon soft blowing without large argon stirring, producing alkaline slag with an alkalinity of 3-5 and a total slag amount of 12-15 kg / t; after deoxidation with 1 kg / t of aluminum granules, aluminum is adjusted to above 0.050% with aluminum wire, and then calcification treatment is carried out, with calcium wire feeding amount of 1-1.5 kg / t steel. After the calcification treatment is completed, soft blowing is carried out for 8 minutes, and then sulfur wire is fed in at 1.5-1.8 kg / t steel to adjust sulfur. After the sulfur wire is fed in, soft blowing is carried out for 15 minutes before leaving the station.
[0017] Furthermore, the continuous casting process is as follows: a special integral nozzle carbon-free tundish is used for continuous casting, argon blowing protection is carried out throughout the process, only a high-alkalinity covering agent is added to the slag surface of the tundish, no carbonized rice husk is added, and the liquid level fluctuation in the crystallizer is ≤5mm.
[0018] Furthermore, the hot rolling process is as follows: the heating furnace is rapidly heated, the total time in the furnace is ≤180min, the billet exit temperature is 1130-1180℃, after high pressure water descaling, the billet is rolled to the intermediate shape by a reciprocating rolling mill with large reduction, then rolled to near the final size by a flat and vertical alternating short stress rolling mill, and finally rolled into the finished product by a KOCKS rolling mill.
[0019] Furthermore, the fiber steel has a tensile strength below 280 MPa, an elongation after fracture above 50%, a reduction of area above 80%, and a metallographic structure showing ferrite, making it suitable for drawing fine wires below 0.2 mm.
[0020] The beneficial effects of this invention are as follows: Based on the requirements for the use of fiber steel and combined with the capabilities of existing equipment, this invention designs the composition and, based on the designed composition, designs the production process. Without using the vacuum decarburization process, the produced material has the characteristics of low tensile strength and good drawing performance, which is suitable for drawing fine wires below 0.2mm. This can significantly improve the stability and efficiency of drawing production, and also save about 50 yuan / ton in vacuum process costs.
[0021] Specifically, the rolled material produced by this invention has a tensile strength of less than 280 MPa, an elongation after fracture of ≥50%, a reduction of area of ≥80%, and a ferrite microstructure in the hot-rolled state, and has the characteristics of low tensile strength and good tensile properties. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 This is a metallographic image of the rolled material after slow cooling in Example 1 of the present invention. Observed at 100X, the metallographic structure is ferrite.
[0024] Figure 2 The image shows the metallographic structure of the rolled material after slow cooling in Example 2 of this invention. Observed at 100X, the metallographic structure is ferrite. Detailed Implementation
[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0026] A method for producing fiber steel includes the following steps:
[0027] (1) A top-and-bottom blown converter is used for smelting, and no slag splashing is performed before smelting. The raw materials for converter smelting are molten iron: scrap steel = 5:1, with a total slag amount of 15 kg / t steel, of which lime: dolomite = 5:4. No nitrogen-argon switching is performed during the later stages of converter smelting; argon is used for bottom blowing throughout the process. No additional blowing is performed after the steel is tapped; the tapping temperature is 1600-1660℃, and the final carbon content is ≤0.05%.
[0028] (2) During and after tapping, no alloys or deoxidizers are added initially. 1.5 kg / t of iron oxide scale is added, followed by 5 minutes of agitation with argon gas. Decarburization is achieved using residual oxygen in the steel and oxygen introduced by the iron oxide scale. After decarburization to below 0.01%, the argon gas is turned off, and alloys and slag washing materials are added: 3 kg / t of aluminum-iron, 1-1.5 kg / t of manganese-iron, 300 kg of lime, and 200 kg of synthetic slag.
[0029] (3) The LF furnace uses a special carbon-free steel ladle, with a smelting time of 60-80 minutes. Argon gas is used for soft blowing throughout the process without large-scale argon gas stirring to produce alkaline slag: the total slag amount is 12-15 kg / t (including slag washing material), and the basicity is 3-5. After deoxidation with 1 kg / t of aluminum granules, aluminum is adjusted to above 0.050% using aluminum wire, and then calcification treatment is carried out. After calcification treatment, soft blowing is performed for 8 minutes, and then sulfur wire is fed in to adjust the sulfur content. After the sulfur wire is fed in, soft blowing is performed for 15 minutes before the furnace exits the station.
[0030] (4) A special integral nozzle carbon-free tundish is used for continuous casting, with argon blowing protection throughout the process. Only a high-alkalinity covering agent is added to the slag surface of the tundish, and no carbonized rice husk is added. The liquid level fluctuation in the crystallizer is ≤5mm.
[0031] (5) The heating furnace is heated rapidly, with a total furnace time of ≤180min. The billet exit temperature is 1130-1180℃. After descaling with high-pressure water, it is rolled into an intermediate billet shape using a reciprocating rolling mill with large reduction. It is then rolled to near the final size using a flat-vertical alternating short-stress rolling mill, and finally rolled into the finished product by a KOCKS rolling mill.
[0032] (6) After rolling, the temperature is above 750℃ and then enters the slow cooling channel. The slow cooling time is above 30 minutes, the cooling rate is ≤0.3℃ / s, and the temperature of the product exiting the slow cooling channel is ≤300℃.
[0033] The fiber steel produced according to the above process steps has the following composition by mass percentage: C≤0.03%; Si≤0.02%; Mn≤0.20%; P≤0.015%; S=0.030-0.050%; Al≥0.035%; N≤0.0030%; the remainder is Fe and unavoidable impurity elements.
[0034] The following examples provide further details.
[0035] Example 1:
[0036] A method for producing fiber-reinforced steel follows a process flow of converter-post-furnace decarburization-LF-continuous casting-heating furnace-rolling. The chemical composition of the final product is shown in Table 1. The process steps include:
[0037] (1) A top-and-bottom blown converter is used for smelting, and no slag splashing is performed before smelting. The raw materials for converter smelting are molten iron:scrap steel = 5:1, with a total slag amount of 15 kg / t steel, of which lime:dolomite = 5:4. No nitrogen-argon switching is performed during the later stages of converter smelting; argon is used for bottom blowing throughout the process. No additional blowing is performed after the steel is tapped; the tapping temperature is 1653℃, and the final carbon content is 0.05%.
[0038] (2) During and after tapping, no alloys or deoxidizers are added initially. 1.5 kg / t of iron oxide scale is added, followed by 5 minutes of agitation with argon gas. Decarburization is achieved using residual oxygen in the steel and oxygen introduced by the iron oxide scale. After decarburization reaches 0.008%, the argon gas is turned off, and alloys and slag washing materials are added: 3 kg / t of aluminum-iron, 1.5 kg / t of manganese-iron, 300 kg of lime, and 200 kg of synthetic slag.
[0039] (3) The LF furnace uses a special carbon-free steel ladle, with a smelting time of 63 minutes. Argon gas is used for soft blowing throughout the process without large-scale argon gas stirring to produce alkaline slag: the total slag amount is 14.5 kg / t (including slag washing material), and the basicity is 4.4. After deoxidation with 1 kg / t of aluminum granules, aluminum is adjusted to 0.061% using aluminum wire, and then calcification treatment is carried out. After calcification treatment, soft blowing is performed for 8 minutes, and then sulfur wire is fed in to adjust the sulfur content. After the sulfur wire is fed in, soft blowing is performed for 15 minutes before the furnace exits the station.
[0040] (4) A special integral nozzle carbon-free tundish is used for continuous casting, with argon blowing protection throughout the process. Only a high-alkalinity covering agent is added to the slag surface of the tundish, and no carbonized rice husk is added. The liquid level fluctuation in the crystallizer is ≤5mm.
[0041] (5) The heating furnace is rapidly heated, with a total furnace time of 172 minutes and a billet exit temperature of 1142℃. After descaling with high-pressure water, the billet is rolled to an intermediate shape using a reciprocating rolling mill with high reduction. It is then rolled to near the final size using a flat-vertical alternating short-stress rolling mill, and finally rolled into a finished product using a KOCKS rolling mill.
[0042] (6) After rolling, the temperature is 758℃ and then enters the slow cooling channel. The slow cooling time is 33 min and the cooling rate is 0.24℃ / s. The temperature when exiting the slow cooling channel is 284℃.
[0043] The mechanical properties of the products produced using the above method are shown in Table 2, and the metallographic structure is as follows: Figure 1 As shown: at 100X, the microstructure is ferrite.
[0044] Example 2:
[0045] A method for producing fiber-reinforced steel follows a process flow of converter-post-furnace decarburization-LF-continuous casting-heating furnace-rolling. The chemical composition of the final product is shown in Table 1. The process steps include:
[0046] (1) A top-and-bottom blown converter is used for smelting, and no slag splashing is performed before smelting. The raw materials for converter smelting are molten iron:scrap steel = 5:1, with a total slag amount of 15 kg / t steel, of which lime:dolomite = 5:4. No nitrogen-argon switching is performed during the later stages of converter smelting; argon is used for bottom blowing throughout the process. No additional blowing is performed after the steel is tapped; the tapping temperature is 1653℃, and the final carbon content is 0.04%.
[0047] (2) During and after tapping, no alloys or deoxidizers are added initially. 1.5 kg / t of iron oxide scale is added, followed by 5 minutes of agitation with argon gas. Decarburization is achieved using residual oxygen in the steel and oxygen introduced by the iron oxide scale. After decarburization reaches 0.006%, the argon gas is turned off, and alloys and slag washing materials are added: 3 kg / t of aluminum-iron, 1.2 kg / t of manganese-iron, 300 kg of lime, and 200 kg of synthetic slag.
[0048] (3) The LF furnace uses a special carbon-free steel ladle, with a smelting time of 78 minutes. Argon gas is used for soft blowing throughout the process without large-scale argon gas stirring to produce alkaline slag: the total slag amount is 13.1 kg / t (including slag washing material), and the basicity is 3.2. After deoxidation with 1 kg / t of aluminum granules, aluminum is adjusted to 0.056% using aluminum wire, and then calcification treatment is carried out. After the calcification treatment, soft blowing is performed for 8 minutes, and then sulfur wire is fed in to adjust the sulfur content. After the sulfur wire is fed in, soft blowing is performed for 15 minutes before the slag is discharged from the station.
[0049] (4) A special integral nozzle carbon-free tundish is used for continuous casting, with argon blowing protection throughout the process. Only a high-alkalinity covering agent is added to the slag surface of the tundish, and no carbonized rice husk is added. The liquid level fluctuation in the crystallizer is ≤5mm.
[0050] (5) The heating furnace is rapidly heated, with a total furnace time of 133 minutes and a billet exit temperature of 1176℃. After descaling with high-pressure water, the billet is rolled into an intermediate billet shape using a reciprocating rolling mill with high reduction. It is then rolled to near the final size using a flat-vertical alternating short-stress rolling mill, and finally rolled into the finished product using a KOCKS rolling mill.
[0051] (6) After rolling, the temperature is 752℃ and then enters the slow cooling channel. The slow cooling time is 32 min and the cooling rate is 0.24℃ / s. The temperature when exiting the slow cooling channel is 292℃.
[0052] The mechanical properties of the products produced using the above method are shown in Table 2, and the metallographic structure is as follows: Figure 2 As shown: at 100X, the microstructure is ferrite.
[0053] Table 1. Chemical composition of the final product (by weight percentage)
[0054] Serial Number C％ Si% Mn% P％ S％ Al％ N％ Example 1 0.03 0.02 0.20 0.015 0.049 0.048 0.0026 Example 2 0.02 0.01 0.10 0.010 0.031 0.037 0.0028
[0055] In Table 1 above, the balance represents Fe and unavoidable impurity elements; each component in Table 1 refers to the elemental content of the final product. The detection method for the chemical components in Table 1 is to sample according to the requirements of GB / T 20066 standard and test according to the requirements of GB / T 4336 standard.
[0056] Comparative Example 1:
[0057] Except for the change of decarburization method to vacuum decarburization, the rest is the same as in Example 1.
[0058] Comparative Example 2:
[0059] Except for the post-rolling cooling rate of 1℃ / s, the rest is the same as in Example 2.
[0060] Example of effect:
[0061] The rolled materials (without additional heat treatment) after slow cooling in step (6) in the examples and comparative examples, i.e., the hot-rolled (+AR) state, were sampled directly according to the requirements of GB / T 2975 standard, and their mechanical properties were tested according to the requirements of GB / T 228.1 standard. The results are shown in Table 2.
[0062] Table 2 Mechanical properties of the effective examples and comparative examples
[0063]
[0064]
[0065] In summary, the technical solution of this invention, especially the decarburization method of this invention, can meet the requirements that the tensile strength of the produced rolled steel is below 280MPa, the elongation after fracture is ≥50%, and the reduction of area is ≥80%, and it is more cost-effective compared with vacuum decarburization.
[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.
Claims
1. A method for producing fiber steel, characterized in that, It includes converter smelting, post-furnace decarburization, LF refining, continuous casting, hot rolling, and cooling processes; The decarburization process after the furnace is as follows: during and after tapping, no alloys or deoxidizers are added. Instead, 1.5 kg / t of iron oxide scale is added and stirred with argon gas for 5 minutes. Decarburization is carried out using residual oxygen in the steel and oxygen introduced by the iron oxide scale. After decarburization to below 0.01%, the argon gas is turned off and alloys and slag washing materials are added. The cooling process is as follows: after rolling, the material enters a slow cooling channel at a temperature above 750°C, the slow cooling time is above 30 minutes, the cooling rate is ≤0.3°C / s, and the temperature exiting the slow cooling channel is ≤300°C. The fiber steel is composed of the following components by mass percentage: C≤0.03%; Si≤0.02%; Mn=0.10-0.20%; P≤0.015%; S≥0.030%; Al≥0.035%; N≤0.0030%; the remainder being Fe and unavoidable impurity elements.
2. The method for producing fiber steel as described in claim 1, characterized in that, The alloy and slag washing materials added in the decarburization process after the furnace are: 3 kg of aluminum-iron per t of steel, 1-1.5 kg of manganese-iron per t of steel, 300 kg of lime + 200 kg of synthetic slag.
3. The method for producing fiber steel as described in claim 2, characterized in that, The converter smelting process is as follows: a top-and-bottom blowing converter is used for smelting. No slag splashing operation is performed before smelting. The raw materials for converter smelting are molten iron: scrap steel mass ratio = 5:1, total slag amount 15kg / t steel, lime: dolomite mass ratio = 5:
4. In the later stage of converter smelting, there is no nitrogen-argon switching of bottom blowing gas. Argon gas is used for bottom blowing throughout the process. Steel is tapped out in one pour without supplementary blowing. The tapping temperature is 1600-1660℃, and the final carbon content is ≤0.05%.
4. The method for producing fiber steel as described in claim 3, characterized in that, The LF refining process is as follows: The LF furnace uses a special carbon-free steel ladle, the smelting time is 60-80 minutes, the whole process is argon soft blowing without large argon stirring, to produce alkaline slag with an alkalinity of 3-5 and a total slag amount of 12-15 kg / t; after deoxidation with 1 kg / t of aluminum granules, aluminum wire is used to adjust the aluminum to above 0.050%, and then calcification treatment is carried out. The calcium wire feed amount is 1-1.5 kg / t of steel. After the calcification treatment is completed, soft blowing is carried out for 8 minutes, and then sulfur wire is fed in at 1.5-1.8 kg / t of steel to adjust the sulfur. After the sulfur wire is fed in, soft blowing is carried out for 15 minutes before leaving the station.
5. The method for producing fiber steel as described in claim 4, characterized in that, The continuous casting process is as follows: a special integral nozzle carbon-free tundish is used for continuous casting, and argon blowing protection is carried out throughout the process. Only a high-alkalinity covering agent is added to the slag surface of the tundish, and no carbonized rice husk is added. The liquid level fluctuation in the crystallizer is ≤5mm.
6. The method for producing fiber steel as described in claim 5, characterized in that, The hot rolling process is as follows: the heating furnace is heated rapidly, the total time in the furnace is ≤180min, the billet exit temperature is 1130-1180℃, after high pressure water descaling, the billet is rolled to the intermediate shape by a reciprocating rolling mill with large reduction, then rolled to near the final size by a flat and vertical alternating short stress rolling mill, and finally rolled into the finished product by a KOCKS rolling mill.
7. The method for producing fiber steel as described in claim 6, characterized in that, The fiber steel has a tensile strength below 280MPa, an elongation after fracture above 50%, a reduction of area above 80%, and a metallographic structure of ferrite, making it suitable for drawing fine wires below 0.2mm.