Clean smelting method for magnesium-aluminum alloy treatment in RH refining process of automobile steel

Abstract

The invention is suitable for the technical field of steel production, and provides a cleaning smelting method for magnesium-aluminum alloy treatment in the RH refining process of automobile steel. Performing RH decarburization and alloying; performing RH alloying pure circulation; the RH vacuum breaking treatment is finished; a tundish; casting a blank; hot rolling; obtaining finished products. According to the magnesium-aluminum alloy treatment clean smelting method in the RH refining process of the automobile steel provided by the scheme, during smelting operation, by adjusting the adding amount, the adding proportion and the adding time of the magnesium-aluminum alloy, the effect that the size, the number and the density of inclusions in the steel are reduced through the magnesium-aluminum alloy is achieved, so that the cleanliness of the automobile steel is improved, and the service life of the automobile steel is prolonged. Meanwhile, the structure of the steel is further refined, and the strength and toughness of a steel product are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of steel production, and in particular relates to a magnesium-aluminum alloy clean smelting method in the RH refining process of automobile steel. Background Art

[0002] With the development of the steel industry, achieving green, high-end and intelligent steel grades is the core goal of improving corporate competitiveness. To achieve high-end, high-end steel grades such as automotive steel must be produced. However, automotive steel has relatively good requirements for cleanliness, especially the requirements for inclusions are very harsh. At present, in order to remove inclusions, various steel companies and research institutions use magnesium treatment, calcium treatment and aluminum treatment technologies to remove inclusions. The process of calcium and aluminum treatment of inclusions can easily cause inclusions to form large-sized Al2O3 inclusions, which have a harmful effect on the plasticity, toughness and fatigue properties of steel.

[0003] Through magnesium treatment, Al2O3 inclusions can be transformed into fine and dispersed inclusions, eliminating the hazards of large-sized Al2O3 inclusions. At the same time, fine and dispersed inclusions can serve as heterogeneous nucleation points for TiN and the steel matrix during solidification, promoting the refinement of TiN and grains. In addition, fine inclusions can pin austenite grain boundaries, inhibit grain growth, and induce the formation of intracrystalline acicular ferrite, thereby further refining the structure and improving strength and toughness. However, during the Mg treatment process, there will be problems such as violent reactions, low element yields, and unstable product quality. In addition, if the amount of Mg added during the Mg treatment process is unreasonable or the process is improperly controlled, there is also a risk of nozzle nodules, which limits the application of magnesium treatment technology.

[0004] Therefore, magnesium processing technology plays a significant role in improving the cleanliness of molten steel, modifying Al2O3 and MnS inclusions in steel, and refining grains. However, the existing technology only focuses on the beneficial effects of Mg and ignores the unfavorable factors, resulting in unstable product quality. Industrial production is still subject to great restrictions, especially for the application effect of low-carbon automotive steel in the RH refining process. These aspects are not clearly involved in the above-mentioned existing technologies, which has become a technical problem that steel companies urgently need to solve. Summary of the invention

[0005] The present invention provides a method for clean smelting of magnesium-aluminum alloy in the RH refining process of automobile steel. The invention aims at precise control technology and parameter control of the RH refining process, studies the effect of magnesium on the refinement and dispersion of alumina inclusions and the improvement of nozzle blockage in order to suppress the generation of clustered Al2O3 inclusions, and aims to achieve the effect of magnesium-aluminum alloy on reducing the size, quantity and density of inclusions in steel by adjusting the amount, proportion and timing of addition of magnesium-aluminum alloy, thereby not only improving the cleanliness of automobile steel, but also further refining the structure of steel and improving the strength and toughness of steel products.

[0006] To solve the above problems, the present invention is implemented as follows: a magnesium-aluminum alloy treatment and clean smelting method in the RH refining process of automobile steel, comprising the following process:

[0007] Steel tapping from converter; RH decarburization and alloying; RH alloying pure cycle; RH air breaking treatment completed; tundish; ingot casting; hot rolled coil; finished product.

[0008] Preferably, the converter tapping mode is a non-killed tapping mode, and when tapping the converter, the terminal temperature is controlled to be above 1580°C.

[0009] Preferably, the oxygen is controlled at 200-400 ppm before RH deoxidation of converter steel, aluminum blocks are used for deoxidation after RH decarburization, and magnesium-aluminum alloy is added 4-8 minutes after alloying; the composition of the magnesium-aluminum alloy is as follows: Mg: 10-15%, Al: 60-80%, C: 0.02-0.05%, S: <0.001, the amount of magnesium-aluminum alloy added is 0.1-5 kg / t, and the magnesium-aluminum alloy is added and circulated purely for 5-10 minutes before breaking the air.

[0010] Preferably, during the clean smelting of RH refined steel, attention is paid to the nodule condition of the stopper rod, upper nozzle and immersed nozzle after casting, and the SEN that is stopped and replaced during continuous casting is retained.

[0011] Preferably, during the clean smelting process of RH refined steel, it is necessary to track the rolling of slabs, take samples of hot-rolled and cold-rolled plates, and determine the properties of the samples.

[0012] Preferably, during the clean smelting of RH refined steel, it is necessary to clearly reduce the amount of aluminum blocks added during the RH deoxidation process, and the remaining operations are performed in accordance with the operating procedures.

[0013] Preferably, during the purification smelting process, the cleanliness and performance impact of the steel in the subsequent processes of continuous casting and hot rolling need to be determined based on the metallurgical effect after the addition of magnesium-aluminum alloy.

[0014] Compared with the related art, the magnesium-aluminum alloy clean smelting method for automobile steel RH refining process provided by the present invention has the following beneficial effects:

[0015] Compared with the prior art, the present invention provides a clean smelting method for magnesium-aluminum alloy treatment in the RH refining process of automobile steel. During the smelting operation, by adjusting the amount, proportion and timing of magnesium-aluminum alloy addition, the effect of reducing the size, quantity and density of inclusions in steel by magnesium-aluminum alloy is achieved, thereby not only improving the cleanliness of automobile steel, but also further refining the steel structure and improving the strength and toughness of the steel product. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a density bar graph of inclusions with different particle sizes in RH refining of a magnesium-aluminum alloy clean smelting method in a RH refining process of automobile steel provided by the present invention;

[0017] Figure 2 It is a density bar graph of inclusions of different particle sizes in the tundish of the present invention;

[0018] Figure 3 It is the smelting flow chart of the present invention. DETAILED DESCRIPTION

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field of the present application; the terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" in the specification and claims of the present application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of the present application or the above-mentioned figures are used to distinguish different objects, rather than to describe a specific order; the terms "inside", "outside", "left", and "right" indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0020] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0021] The embodiment of the present invention provides a magnesium-aluminum alloy cleaning smelting method in the RH refining process of automobile steel, such as Figures 1 to 3 As shown in the figure, the clean smelting process of magnesium-aluminum alloy processing for automobile steel in the RH refining process is:

[0022] Steelmaking from converter - RH decarburization and alloying - RH alloying pure cycle - RH air breaking treatment completed - tundish - ingot casting - hot rolled coil - finished product.

[0023] In this embodiment, a clean smelting method for magnesium-aluminum alloy treatment in the RH refining process of automobile steel is formed through the processes of converter steel tapping - RH decarburization and alloying - RH alloying pure cycle - completion of RH air breaking treatment - tundish - ingot - hot rolled coil - finished product. In the overall smelting process, by adjusting the amount, proportion and timing of magnesium-aluminum alloy addition, the effect of magnesium-aluminum alloy on reducing the size, quantity and density of inclusions in steel is achieved, thereby not only improving the cleanliness of automobile steel, but also further refining the structure of the steel, and improving the strength and toughness of the steel product.

[0024] In a further preferred embodiment of the present invention, the converter tapping mode is a non-quiet tapping mode, and when tapping the converter, the terminal temperature is controlled to be above 1580°C.

[0025] In this embodiment, during the RH refining process of magnesium-aluminum alloy processing and clean smelting of automobile steel, it is necessary to control the terminal temperature to be above 1580°C when tapping the converter.

[0026] In a further preferred embodiment of the present invention, the oxygen is controlled at 200-400 ppm before RH deoxidation of converter steel, aluminum blocks are used for deoxidation after RH decarburization, and magnesium-aluminum alloy is added 4-8 minutes after alloying; the composition of the magnesium-aluminum alloy is as follows: Mg: 10-15%, Al: 60-80%, C: 0.02-0.05%, S: <0.001, the amount of magnesium-aluminum alloy added is 0.1-5 kg / t, and the magnesium-aluminum alloy is added and circulated purely for 5-10 minutes before breaking the air.

[0027] In this embodiment, in the actual smelting process, the magnesium-aluminum alloy with corresponding component requirements is added 4 to 8 minutes after alloying.

[0028] In a further preferred embodiment of the present invention, during the clean smelting of RH refined steel, attention is paid to the nodule condition of the stopper rod, upper nozzle and submerged nozzle after casting, and the SEN that is stopped and replaced during continuous casting is retained.

[0029] In this embodiment, during the smelting process, it is necessary to pay real-time attention to the nodule conditions of the stopper rod, upper nozzle and immersed nozzle after casting, and retain the SEN when continuous casting is stopped and replaced, so as to facilitate understanding of the overall smelting situation.

[0030] In a further preferred embodiment of the present invention, during the clean smelting process of RH refined steel, it is necessary to track the slab rolling conditions, take samples of hot-rolled and cold-rolled plates, and determine the sample properties.

[0031] In this embodiment, during the smelting operation, the staff not only needs to track the rolling of the slab, but also needs to take samples of the hot-rolled and cold-rolled plates, test the samples, and determine the performance of the samples.

[0032] In a further preferred embodiment of the present invention, during the clean smelting of RH refined steel, it is necessary to clearly reduce the amount of aluminum blocks added during the RH deoxidation process, and the remaining operations are performed in accordance with the operating procedures.

[0033] In this embodiment, at the same time, during the smelting process, it is necessary to clarify the amount of aluminum blocks added during the RH deoxidation process.

[0034] In a further preferred embodiment of the present invention, during the purification smelting process, it is necessary to determine the cleanliness and performance impact of the steel in the subsequent processes of continuous casting and hot rolling based on the metallurgical effect after the addition of magnesium-aluminum alloy.

[0035] In this embodiment, at the same time, during the actual smelting operation, it is also necessary to determine the impact on the cleanliness and performance of the subsequent steel according to the metallurgical effect after the addition of magnesium-aluminum alloy.

[0036] In summary, compared with the relevant technologies, the clean smelting method of magnesium-aluminum alloy treatment in the RH refining process of automobile steel, during the smelting operation, by adjusting the amount, proportion and timing of magnesium-aluminum alloy addition, can achieve the effect of reducing the size, quantity and density of inclusions in steel by magnesium-aluminum alloy, thereby not only improving the cleanliness of automobile steel, but also further refining the steel structure and improving the strength and toughness of steel products.

[0037] According to the clean smelting method of magnesium-aluminum alloy in the RH refining process of automobile steel in this paper, the corresponding case implementation operation is carried out:

[0038] Implementation Case 1

[0039] SPHC and other low silicon non-calcium treated lightly treated steel (Si≤0.05%)

[0040] (1) In the converter non-killed steelmaking mode, the final temperature is controlled at 1640℃~1660℃, and oxygen blowing is not used to increase the temperature in the RH refining station as much as possible.

[0041] (2) The oxygen content before RH deoxidation is controlled to be ≤350ppm. After RH decarburization, aluminum blocks are used for deoxidation. Magnesium-aluminum alloy is added 3 to 6 minutes after alloying. The composition of magnesium-aluminum alloy is as follows: Mg: 10 to 15%, Al: 60 to 880%, C: 0.02 to 0.05%, S: <0.001, the amount of magnesium-aluminum alloy added is 30 to 150kg, and the magnesium-aluminum alloy is broken 4 to 6 minutes after addition.

[0042] (3) Pay attention to the nodule condition of the stopper rod, upper nozzle and immersed nozzle after casting, and retain the SEN that is stopped and replaced during continuous casting.

[0043] (4) Track the rolling of slabs and take samples of hot-rolled and cold-rolled plates for analysis.

[0044] (5) RH Pay attention to reducing the amount of aluminum blocks added during the deoxidation process, and perform other operations in accordance with the operating procedures.

[0045] Implementation Case 2

[0046] Ultra-low carbon steel grades (Si≤0.05%) treated with low silicon and non-calcium such as SDC06

[0047] (1) In the converter non-killed steelmaking mode, the final temperature is controlled at 1650℃~1670℃, and the RH refining station is not heated by blowing oxygen as much as possible.

[0048] (2) The oxygen content of RH before entering the station is 200-500ppm, the oxygen before RH deoxidation is controlled at 280-400ppm, the station temperature is 1600℃-1610℃, the decarburization oxygen blowing amount is <150Nm3, the T.Fe of the exiting slag is 3-6%, and the CaO / Al2O3 is 1.5-2.5.

[0049] After RH decarburization, aluminum blocks are used for deoxidation, and magnesium-aluminum alloy is added 3 to 5 minutes after alloying; the composition of the magnesium-aluminum alloy is as follows: Mg: 10 to 15%, Al: 60 to 880%, C: 0.02 to 0.05%, S: <0.001, the amount of magnesium-aluminum alloy added is 50 to 250 kg, and the magnesium-aluminum alloy is broken 3 to 5 minutes after addition.

[0050] (3) Pay attention to the nodule condition of the stopper rod, upper nozzle and immersed nozzle after casting, and retain the SEN that is stopped and replaced during continuous casting.

[0051] (4) Track the rolling of slabs and take samples of hot-rolled and cold-rolled plates.

[0052] (5) RH Pay attention to reducing the amount of aluminum blocks added during the deoxidation process, and perform other operations in accordance with the operating procedures.

[0053] (6) The equivalent diameter and density of inclusions in magnesium-modified automobile steel are reduced, and the number density of the equivalent diameter of inclusions in the size range of 5-10μm is reduced from 3.5 / mm2 to 1.5 / mm2. By counting the proportion of inclusions in different area ranges, it can be seen that after magnesium treatment, the proportion of small-sized inclusions in steel increases, and the proportion of large-sized inclusions decreases. The proportion of small-sized inclusions of 0-4μm increases from 46% to 77%, while the proportion of large-sized inclusions >10μm decreases from 10% to 4%, and the size of the overall inclusions is concentrated in small sizes. The cleanliness of the ingot and the surface quality of the cold-rolled product are significantly improved, and the defect rate caused by inclusions is reduced from 2.5% to less than 1.0%.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on these embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field can still combine, add, delete or make other adjustments to the features in the various embodiments of the present invention according to the circumstances without conflict, without making creative work, so as to obtain different other technical solutions that do not deviate from the concept of the present invention in essence, and these technical solutions also belong to the scope of protection of the present invention.

Claims

1. A method for cleaning and smelting magnesium-aluminum alloy in the RH refining process of automobile steel, characterized in that: The process includes: S1: tapping from converter; S2: RH decarburization and alloying; S3: RH alloying pure cycle; S4: RH air-breaking processing is completed; S5: Tundish; S6: Casting billet; S7: hot rolled coil; S8: Finished product.

2. The method for cleaning and smelting magnesium-aluminum alloy in the RH refining process of automobile steel according to claim 1, characterized in that: The converter tapping mode is a non-killed tapping mode. When tapping the converter, the terminal temperature is controlled to be above 1580-1690° C. (preferably 1645° C.).

3. The method for cleaning and smelting magnesium-aluminum alloy in the RH refining process of automobile steel according to claim 1, characterized in that: Before RH deoxidation of converter steel, the oxygen is controlled at 200-400ppm, and aluminum blocks are used for deoxidation after RH decarburization. Magnesium-aluminum alloy is added 4-8 minutes after alloying; the composition (mass fraction) of magnesium-aluminum alloy is as follows: Mg: 10-15%, Al: 60-80%, C: 0.02-0.05%, S: <0.001%, and the amount of magnesium-aluminum alloy added is 0.1-5kg / t. After adding magnesium-aluminum alloy, the pure circulation is 5-10 minutes and then the air is broken.

4. The method for cleaning and smelting magnesium-aluminum alloy in the RH refining process of automobile steel according to claim 1, characterized in that: During the clean smelting process of RH refined steel, attention is paid to the nodule condition of the stopper rod, upper water inlet and submerged water inlet after casting, and the submerged water inlet SEN of the crystallizer that is stopped and replaced during continuous casting is retained.

5. The method for cleaning and smelting magnesium-aluminum alloy in the RH refining process of automobile steel according to claim 1, characterized in that: During the clean smelting process of RH refined steel, it is necessary to track the rolling of slabs, take samples of hot-rolled and cold-rolled plates, and determine their sample properties.

6. The method for cleaning and smelting magnesium-aluminum alloy in the RH refining process of automobile steel according to claim 1, characterized in that: During the clean smelting of RH refined steel, it is necessary to reduce the amount of aluminum blocks added during the RH deoxidation process, and the rest of the operations are carried out in accordance with the operating procedures.

7. The method for cleaning and smelting magnesium-aluminum alloy in the RH refining process of automobile steel according to claim 1, characterized in that: During the purification smelting process, it is necessary to determine the cleanliness and performance of the steel in the subsequent processes of continuous casting and hot rolling based on the metallurgical effect after the addition of magnesium-aluminum alloy.

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