Preparation method of steel for hollow stabilizer bar of new energy vehicle with high cleanliness

Abstract

The present invention belongs to the technical field of steelmaking, and specifically relates to a preparation method of steel for the hollow stabilizer bar of new energy vehicles with high cleanliness. By adding aluminum blocks after the converter and feeding aluminum wire in the argon blowing station for deep deoxidation, the aluminum content in the LF refining process is controlled at a relatively low level. The RH adopts a vacuum light treatment mode, reducing the aluminum loss during the vacuum treatment process. The aluminum content is adjusted to the target value at the end of the vacuum. The steel produced by this process has high cleanliness, and the inclusions in the molten steel are a small amount of small-sized low-melting calcium aluminates. The oxide inclusions can meet the requirements of B fine, B coarse, D fine, D coarse ≤ 1.0 grade, and Ds ≤ 0.5 grade.

Description

Technical Field

[0001] The present invention belongs to the technical field of steelmaking, and particularly relates to a preparation method of steel for a hollow stabilizer bar of a new energy vehicle with high cleanliness. Background Art

[0002] The lateral stabilizer bar is used to increase the roll angle stiffness of the vehicle suspension, reduce the body tilt angle, and enable the vehicle to drive smoothly when the road condition is uneven or turning. At present, the chassis stabilizer bars used in domestic commercial vehicles and most passenger vehicles are all solid structures. The materials of the solid stabilizer bars are mainly spring round steels 60Si2Mn and 50CrVA. With the rapid development of new energy vehicles, and at the same time to achieve energy conservation, emission reduction and vehicle lightweighting, the application of steel for hollow stabilizer bars is also emerging. The outer diameter of the hollow stabilizer bar is larger than that of the solid bar, but the quality can be reduced by about 40%, which is of great significance for lightweighting. The steels for hollow stabilizer bars mainly include materials for welded pipe processes such as 20MnB5, 22MnB5, and 26MnB5 (mainly imported), and materials for seamless pipe processes such as 35CrMo and 42CrMo. As an important durable and safety part of the chassis, the service conditions of the stabilizer bar are often relatively harsh, and the cleanliness of the raw materials is extremely critical to the fatigue life of the stabilizer bar.

[0003] The seamless hollow stabilizer bar is a new technology and new product with great market potential. Developing a seamless hollow stabilizer bar material that can replace imported foreign materials has great market value. The main difficulty lies in how to improve the cleanliness of the raw materials. During the middle and late stages of LF refining and the vacuum treatment process of the conventional smelting process, the aluminum loss is large, indicating that the molten steel is severely oxidized, the steel slag reaction is too intense, the steel slag is severely emulsified, and at the same time, the Al 2 O 3 content in the slag increases sharply, affecting the adsorption effect of the slag on inclusions.

[0004] Publication No. CN 114908219 A discloses a smelting method for reducing silicon-manganese inclusions in aluminum-killed steel. Through deoxidation with aluminum ingots in the primary smelting process, alloying with ferrosilicon and low-carbon ferromanganese, adding calcium aluminate pre-melted slag and lime to make slag, controlling the slag basicity of LF refining to be 5-8, and the vacuum time control range to be 15-25 min, the aluminum content in the molten steel is ≥0.01% after the vacuum degassing and breaking of the vacuum, which can reduce the silicon-manganese inclusions in aluminum-killed steel. This invention focuses on how to control silicon-manganese inclusions, but for aluminum-killed steel, the main inclusion types are alumina, magnesium aluminate spinel, and calcium aluminate, and how to control them is not involved in this invention; in addition, the RH vacuum treatment time is long, which will cause a large aluminum loss during the vacuum process, thus affecting the adsorption effect of the slag on inclusions.

[0005] Publication No. CN 115491577 A discloses a smelting method for improving the cleanliness of steel used for automotive hollow stabilizer bars. By using low-carbon and low-calcium alloys throughout the process, high-grade powdered silicon carbide is used to make a reducing slag, and most of the inclusions in the steel after LF refining are solid oxides. Then, through RH high-vacuum strong stirring (RH lifting gas flow rate of 96 - 120 Nm 3 / h, high-vacuum treatment time of ≥ 20 min at ≤ 67 Pa), they are removed, and after a small amount of calcium treatment, the class B and class D inclusions are controlled to be ≤ grade 1.0. Using the RH high-vacuum strong stirring mode, due to the intense steel water circulation and long vacuum treatment time, the temperature drop of the steel water during the vacuum process is large and the aluminum loss is relatively large, which is not conducive to the control of the production rhythm and increases the production cost to a certain extent.

[0006] In summary, the prior art does not involve the influence of aluminum loss changes during the smelting process on the inclusions of aluminum-killed steel, nor the influence of the RH vacuum light treatment mode on the inclusions. Therefore, how to provide molten steel with sufficient deoxidation and a low aluminum content for the RH process, use a reasonable vacuum degree and vacuum degassing mode in the RH process to reduce the aluminum loss during the process, and adjust the aluminum content using a vacuum feeding device at the end of the vacuum treatment to reduce the size and quantity of class B, class D, and class Ds inclusions of oxides in the steel, so as to achieve the purpose of improving the cleanliness of steel used for new energy vehicle hollow stabilizer bars, is the problem to be solved by the present invention. Summary of the Invention

[0007] The purpose of the present invention is to optimize the production process of new energy vehicle hollow stabilizer bars mainly from the perspective of inclusion control to address the above technical problems. It is proposed to deeply deoxidize by adding aluminum blocks after the converter and feeding aluminum wire at the argon blowing station, control the aluminum content at a relatively low level during the LF refining process, use the RH vacuum light treatment mode, reduce the aluminum loss during the vacuum treatment process, and then adjust the aluminum content to the target value at the end of the vacuum, ensuring the removal effect of spinel inclusions by RH while reducing the content of alumina and calcium aluminate inclusions. The steel produced by this process has high cleanliness, and the inclusions in the molten steel are a small amount of small-sized low-melting-point calcium aluminate, and the oxide inclusions can meet the requirements that class B fine, class B coarse, class D fine, class D coarse ≤ grade 1.0, and class Ds ≤ grade 0.5.

[0008] The technical solution adopted to achieve the purpose of the present invention is: a preparation method for steel used for high-cleanliness new energy vehicle hollow stabilizer bars, including the following processes carried out in sequence: converter smelting, argon blowing station, LF refining, RH vacuum treatment, and continuous casting.

[0009] (1) When the converter taps, add 0.54 - 0.69 kg / t of aluminum blocks (the amount of aluminum blocks added per ton of steel) behind the furnace, only add 5.0 - 5.77 kg / t of lime as the slag-making material, and feed 20 - 50 m of aluminum wire at the argon blowing station for deep deoxidation;

[0010] Utilize the strong deoxidization ability of aluminum. Add aluminum blocks in stages during tapping and feed an appropriate amount of aluminum wire at the argon blowing station to ensure the precipitation deoxidization effect and make the deoxidization products float upward as early as possible (the lower the recovery rate of aluminum, the better, and as much aluminum as possible is converted into deoxidization products and enters the slag to ensure the slag melting effect). Only add lime as the slag-making material to prevent the excessive content of Al 2 O 3 in the slag. At the same time, the precipitation deoxidization products can enter the slag to ensure the slag melting effect and improve the adsorption effect of the slag on non-metallic inclusions.

[0011] (2) The LF refining process includes: During the LF refining process, use ferrosilicon powder and silicon carbide for deoxidization to make white slag, do not use aluminum wire and aluminum grains, and use low-aluminum alloys to adjust the composition throughout the process (specific low-aluminum alloys include any one or more of low-aluminum ferrosilicon, low-carbon ferrochrome, low-aluminum silicomanganese, ferromolybdenum, etc.), and control the aluminum content in the entire LF refining process ≤ 0.008%;

[0012] The aluminum content of the low-aluminum ferrosilicon and low-aluminum silicomanganese is ≤ 0.010%;

[0013] In the middle and early stages of LF refining, use ferrosilicon powder and silicon carbide to make white slag to strengthen diffusion deoxidization. At the same time, disable aluminum wire and aluminum grains, use low-aluminum alloys, reduce the aluminum content in the molten steel, and ensure that the spinel inclusions rich in Mg and poor in Al are present at the end of LF refining.

[0014] (3) The RH vacuum treatment process includes: Select argon as the lifting gas for RH vacuum treatment, with the lifting gas flow rate of 60 - 80 Nm 3 / h, and control the vacuum degree at 2 - 3.5 kPa (specifically, when performing RH vacuum treatment, first turn on the 4# and 5# vacuum pumps, and then turn on the 3# vacuum pump after about 2 minutes), and the treatment time is 10 - 12 min. At the end of the RH vacuum treatment, use vacuum feeding to add 0.2 - 0.4 kg / t of aluminum blocks to adjust the aluminum content to the target value.

[0015] The RH vacuum treatment has good removal effect and high efficiency on solid inclusions, especially spinel inclusions rich in Mg and poor in Al, and can be quickly removed even under relatively low vacuum degree conditions. Utilize this characteristic, adopt the RH light treatment mode, which can efficiently remove spinel while reducing the aluminum loss in the molten steel. At the end of the RH vacuum treatment, use vacuum feeding equipment to add aluminum blocks, which improves the recovery rate of aluminum, reduces alloy consumption, reduces the content of alumina and calcium aluminate inclusions, and improves the cleanliness of the molten steel.

[0016] The quality components of the steel grade involved in the present invention include: C 0.30 - 0.40%, Si 0.15 - 0.40%, Mn 1.00 - 1.40%, P ≤ 0.025%, S ≤ 0.005%, Cr 0.18 - 0.50%, Mo 0.05 - 0.30%, Al 0.015 - 0.030%, Ti 0.015 - 0.040%, B 0.0015 - 0.0050%, and the balance is Fe and inevitable impurities.

[0017] The beneficial effects of the present invention are as follows:

[0018] In the present invention, aluminum blocks are added after the converter and aluminum wires are fed in the argon blowing station for deep deoxidation, controlling the aluminum content in the LF refining process at a relatively low level. The RH adopts a vacuum light treatment mode, reducing the aluminum loss during the vacuum treatment process. The aluminum content is adjusted to the target value at the end of the vacuum period, improving the cleanliness of the molten steel.

[0019] Compared with the existing process technology, in the process of the present invention, aluminum blocks are added after the converter and aluminum wires are fed into the argon blowing station in stages, ensuring the precipitation deoxidation effect and making the deoxidation products float as early as possible. The aluminum content in the LF refining process is controlled ≤ 0.008% throughout the LF refining process, ensuring that the spinel inclusions at the end of the LF refining are rich in Mg and low in Al. The RH adopts a vacuum light treatment mode, efficiently removing spinel inclusions while reducing the aluminum loss of the molten steel; aluminum blocks are added using a vacuum feeding device at the end of the RH vacuum treatment, improving the recovery rate of aluminum, reducing the content of alumina and calcium aluminate inclusions, and improving the cleanliness of the molten steel. Finally, the inclusions in the molten steel are a small amount of small-sized low-melting-point calcium aluminate, and the oxide inclusions can meet the requirements of B fine, B coarse, D fine, D coarse ≤ 1.0 grade, and Ds ≤ 0.5 grade. Description of the Drawings

[0020] Figure 1 Changes in calcium aluminate inclusions during the smelting process of the example (electron microscopy statistical size 1μm - 3μm, ≥ 3μm).

[0021] Figure 2 Changes in calcium aluminate inclusions during the smelting process of the comparative example (electron microscopy statistical size 1μm - 3μm, ≥ 3μm). Detailed Description of the Invention

[0022] The present invention is not limited to the following specific embodiments. Those of ordinary skill in the art can implement the present invention in other various specific embodiments according to the content disclosed in the present invention, or any simple changes or modifications made using the design structure and concept of the present invention fall within the protection scope of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0023] The present invention is further described in detail below in conjunction with embodiments:

[0024] In this embodiment and the comparative example, the comprehensive control effect of the present invention is illustrated by the smelting process of the steel for the hollow stabilizer bar of new energy vehicles. The melting composition of the steel grade is C 0.34%, Si 0.30%, Mn 1.35%, P 0.015%, S 0.003%, Cr 0.28%, Mo 0.15%, Al 0.022%, Ti 0.0030%, B 0.0028%.

[0025] The present invention will be further described in detail below in conjunction with embodiments:

[0026] Example 1

[0027] The steel grade of the example is 34MnB5, and the smelting steps include converter smelting, argon blowing station, LF refining, RH vacuum treatment and continuous casting. The processes not specifically defined are conventional processes.

[0028] (1) When tapping from the 130t converter, 80 kg of aluminum blocks are added behind the furnace, only 700 kg of lime is added as slag-making material, and 30 m of aluminum wire is fed into the argon blowing station for deep deoxidation;

[0029] (2) The LF refining process includes: 50 kg of ferrosilicon powder and 150 kg of silicon carbide are used for deoxidation and white slag making (FeO≤0.50% and MnO≤0.25% in the slag) during LF refining. Aluminum wire and aluminum pellets are not used, and low-aluminum alloys are used throughout the process to adjust the composition. After adjustment, C is 0.34%, Si is 0.30%, Mn is 1.35%, Cr is 0.28%, Mo is 0.15%. The low-aluminum alloys include 116 kg of low-aluminum ferrosilicon (Si 74.9%, Al 0.008%), 611 kg of low-carbon ferrochrome (Cr 56.2%, Al 0.007%), 2588 kg of low-aluminum silicomanganese (Si 16.3%, Mn 64.2%, Al 0.008%), 325 kg of ferromolybdenum (Mo 59.8%, Al 0.006%). The maximum aluminum content during the entire LF refining process is 0.006%;

[0030] (3) The RH vacuum treatment process includes: Argon is selected as the lifting gas for RH vacuum treatment, and the lifting gas flow rate is 75 Nm 3 / h. When performing RH vacuum treatment, the 4# and 5# vacuum pumps are first turned on, and the 3# vacuum pump is turned on about 2 minutes later. The vacuum degree is controlled at 3.5 kPa, and the treatment time is 10 min. At the end of the RH vacuum treatment, 36 kg of aluminum blocks are added by vacuum feeding to adjust the aluminum content to the target value.

[0031] Example 2

[0032] In step (1), 50 m of aluminum wire is fed into the argon blowing station for deep deoxidation, and the rest of the operations are the same as those in Example 1.

[0033] Example 3

[0034] In step (3), the gas flow rate is increased by 60 Nm 3 / h, and the remaining operations are the same as those in Example 1.

[0035] Example 4

[0036] In step (3), the vacuum degree is controlled at 2 kPa, and the remaining operations are the same as those in Example 1.

[0037] Example 5

[0038] In step (3), the treatment time is 12 min, and the remaining operations are the same as those in Example 1.

[0039] Comparative Example 1

[0040] In Example 1, "feeding 30 m of aluminum wire at the argon blowing station for deep deoxidation" is modified to "feeding 80 m of aluminum wire at the argon blowing station for deep deoxidation", and other conditions are the same as those in Example 1.

[0041] Comparative Example 2

[0042] In Example 1, "using low aluminum alloy to adjust the composition throughout the process" is modified to "using 116 kg of ferrosilicon (Si 74.9%, Al 0.061%), 2588 kg of silicomanganese (Si 16.3%, Mn 64.2%, Al 0.054%), 611 kg of high-carbon ferrochrome (Cr 55.8%, Al 0.072%), 325 kg of ferromolybdenum (Mo 59.8%, Al 0.006%) to adjust the composition, and after adjustment, C is 0.34%, Si is 0.30%, Mn is 1.35%, Cr is 0.28%, and Mo is 0.15%", and other conditions are the same as those in Example 1.

[0043] Comparative Example 3

[0044] In Example 1, "the vacuum degree is controlled at 3.5 kPa" is modified to "the vacuum degree is controlled at 133 Pa", and other conditions are the same as those in Example 1. At this time, spinel inclusions can be completely removed, but due to the high vacuum degree, the aluminum loss after RH treatment is relatively large, and there are more alumina inclusions than in the process of this application. When the vacuum degree is lower than 3.5 kPa, due to the decrease in the vacuum degree, the removal efficiency of spinel inclusions decreases, and it is necessary to extend the treatment time or increase the total amount of molten steel circulation to ensure the removal effect of spinel, which will reduce the production efficiency and increase the cost.

[0045] Comparative Example 4

[0046] In step (3) of Example 1, "the treatment time is 10 min" is modified to "the treatment time is 15 min", and other conditions are the same as those in Example 1.

[0047] Comparative Example 5

[0048] In Example 1, the sentence “At the end of the RH vacuum treatment, 36 kg of aluminum blocks were added by vacuum feeding to adjust the aluminum content to the target value.” was modified to “After the RH breaking vacuum, 140 m (36 kg) of aluminum wire was fed to adjust the aluminum content to the target value.” Other conditions were the same as those in Example 1.

[0049] Non-metallic inclusion ratings and fatigue life of finished stabilizer bars of the steel bars prepared in Examples 1-5 and Comparative Examples 1-5.

[0050] Table 1 Non-metallic inclusion ratings and fatigue life of finished stabilizer bars of the steel bars prepared in Examples 1-5 and Comparative Examples 1-5

[0051]

[0052]

[0053] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A preparation method of steel for the hollow stabilizer bar of new energy vehicles with high cleanliness, characterized in that: it includes the following processes carried out in sequence: converter smelting, argon blowing station, LF refining, RH vacuum treatment and continuous casting; In the converter tapping process, when tapping the converter, 0.54 - 0.69 kg / t of aluminum blocks are added behind the furnace, and only 5.0 - 5.77 kg / t of lime is added as the slag-making material. 20 - 50 m of aluminum wire is fed into the argon blowing station for deep deoxidation; In the LF refining process, ferrosilicon powder and silicon carbide are used for deoxidation to make white slag. Aluminum wire and aluminum grains are not used, and low-aluminum alloys are used throughout the process to adjust the composition, controlling the aluminum content in the whole LF refining process ≤ 0.008%; In the RH vacuum treatment process, argon is selected as the lifting gas, and the lifting gas flow rate is 60 - 80 Nm 3 / h, the vacuum degree is controlled at 2 - 3.5 kPa, the treatment time is 10 - 12 min, and at the end of the RH vacuum treatment, 0.2 - 0.4 kg / t of aluminum blocks are added by vacuum feeding to adjust the aluminum content to the target value; In the LF refining process, low-aluminum alloys are used throughout the process to adjust the composition. The low-aluminum alloys include any one or two of low-aluminum ferrosilicon and low-aluminum silicomanganese; The aluminum content of low-aluminum ferrosilicon and low-aluminum silicomanganese is both ≤ 0.010%.

2. The preparation method of steel for the hollow stabilizer bar of new energy vehicles with high cleanliness as described in claim 1, characterized in that: The mass composition of the steel grade includes: C 0.30 - 0.40%, Si 0.15 - 0.40%, Mn 1.00 - 1.40%, P ≤ 0.025%, S ≤ 0.005%, Cr 0.18 - 0.50%, Mo 0.05 - 0.30%, Al 0.015 - 0.030%, Ti 0.015 - 0.040%, B 0.0015 - 0.0050%.

3. The preparation method of steel for the hollow stabilizer bar of new energy vehicles with high cleanliness as described in claim 1, characterized in that: The vacuum degree control method in the RH vacuum treatment process includes that when carrying out RH vacuum treatment, the 4# and 5# vacuum pumps are first started, and then the 3# vacuum pump is started after about 2 minutes.

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