A method for controlling the surface scale of hot-rolled wire rod and a hot-rolled wire rod

Abstract

This invention belongs to the field of steel rolling technology, specifically relating to a method for controlling iron oxide scale on the surface of hot-rolled wire rod and the hot-rolled wire rod itself. The method includes: molten steel is smelted in a converter, refined, and continuously cast to obtain a billet; the billet is heated and descaled; the descaled billet is subjected to controlled rolling and controlled cooling to obtain wire rod; the controlled rolling and controlled cooling process includes: roughing, intermediate rolling, finishing rolling, wire drawing, and roller cooling; a first pre-cooling treatment is performed before finishing rolling; a second pre-cooling treatment is performed before wire drawing, with a wire drawing temperature of 850℃-900℃; the roller cooling process includes a first cooling treatment and a second cooling treatment, wherein the roller speed of the first cooling treatment is 0.7m / s-1.1m / s, the cooling rate is 3℃ / s-5℃ / s, and the final cooling temperature is 740℃-780℃; and the roller speed of the second cooling treatment is 0.8m / s-1.3m / s, the cooling rate is 1℃ / s-3℃ / s, and the final cooling temperature is 560℃-600℃. The present invention forms a loose iron oxide scale structure on the surface of wire rod that is not easy to fall off automatically, but is easy to fall off during mechanical peeling.

Description

Technical Field

[0001] This invention relates to the field of steel rolling technology, specifically to a method for controlling iron oxide scale on the surface of hot-rolled wire rod and the hot-rolled wire rod itself. Background Technology

[0002] Hot-rolled wire rod is mainly used to manufacture products such as automotive seat steel wire, sofa springs, and computer brackets. The hot-rolled wire rod undergoes mechanical peeling, pickling, and drawing into steel wire, which is then polished and electroplated by downstream manufacturers to produce finished products. The iron oxide scale layer on the surface of the hot-rolled wire rod affects the quality of the steel wire and the finished product. Firstly, the iron oxide scale layer may automatically detach during storage and transportation, failing to protect the wire rod substrate. Instead, the exposed metal substrate reacts with oxygen and moisture in the air to form red ferric oxide, which is difficult to remove during pickling, affecting the quality of the steel wire and the finished product. Secondly, the iron oxide scale layer may not be easily removed during mechanical peeling, leaving residual scale on the wire rod surface. After pickling and drawing, this residual scale can form small black pinhole defects on the steel wire surface, affecting the quality of the steel wire and the finished product.

[0003] In response to this, there is an urgent need in the field for a method to control the iron oxide scale on the surface of hot-rolled wire rod, forming an iron oxide scale layer on the surface of the wire rod that is not easy to fall off automatically and is easy to remove during mechanical peeling. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies, such as the easy automatic shedding of iron oxide scale during storage and transportation, the difficulty in removing ferric oxide formed by pickling, and the difficulty in removing iron oxide scale by mechanical peeling. This invention provides a method for controlling iron oxide scale on the surface of hot-rolled wire rod and the hot-rolled wire rod itself. This method controls the thickness and composition of iron oxide scale on the surface of the hot-rolled wire rod, thereby forming a loose iron oxide scale structure on the surface of the wire rod that is not easy to fall off automatically, but is easy to fall off during mechanical peeling.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for controlling iron oxide scale on the surface of hot-rolled wire rod, the method comprising:

[0006] Molten steel is smelted, refined and continuously cast in a converter to obtain a billet;

[0007] The billet is heated and descaled;

[0008] The descaled billet is subjected to controlled rolling and controlled cooling to obtain wire rod; the controlled rolling and controlled cooling process includes: roughing, intermediate rolling, finishing, wire drawing and roller cooling;

[0009] The first pre-cooling treatment is performed before the finishing rolling;

[0010] The second pre-cooling treatment is performed before spinning, and the conditions for spinning include: the spinning temperature is 850℃-900℃;

[0011] The roller cooling system has a roller speed of 0.7 m / s to 1.3 m / s and includes a first cooling process and a second cooling process. The conditions for the first cooling process are: roller speed of 0.7 m / s to 1.1 m / s, cooling rate of 3℃ / s to 5℃ / s, and final cooling temperature of 740℃ to 780℃. The conditions for the second cooling process are: roller speed of 0.8 m / s to 1.3 m / s, cooling rate of 1℃ / s to 3℃ / s, and final cooling temperature of 560℃ to 600℃.

[0012] In some preferred embodiments, the conditions for the first precooling treatment include a cooling rate of 20°C / s to 30°C / s; and / or the conditions for the finishing rolling include a finishing rolling temperature of 820°C to 860°C.

[0013] In some preferred embodiments, the conditions for the second precooling treatment include: a cooling rate of 25°C / s to 35°C / s, and / or, the spinning temperature of 860°C to 890°C.

[0014] In some preferred embodiments, the heating conditions include: the temperature of the heating section is 1020℃~1100℃, the temperature of the soaking section is 1060℃~1100℃, and the total heating time of the billet in the heating section and the soaking section is controlled to be 70min~90min.

[0015] In some preferred embodiments, the chemical composition of the billet is controlled by weight percentage through the converter smelting, refining and continuous casting processes to include: C: 0.17% to 0.23%, Si: 0.17% to 0.30%, Mn: 0.40% to 0.60%, N≤0.007%, P≤0.020%, S≤0.020%, Cr≤0.10%, Ni≤0.15%, Cu≤0.15%, Alt≤0.006%, with the remainder being iron and unavoidable impurities.

[0016] Preferably, the converter smelting includes adding aluminum blocks to the molten steel between P / 4 tons and P / 3 tons of steel produced by the converter, adjusting the amount of aluminum blocks added according to the carbon content at the converter endpoint, wherein the carbon content at the endpoint is ≥0.08%, and the amount of aluminum blocks added is 0.60 kg / t-0.70 kg / t.

[0017] Preferably, the refining includes LF refining, which includes sequentially adding lime and fluorite, treating the slag with submerged arc heating, and then adding calcium silicate powder deoxidizer to create white slag.

[0018] In a second aspect, the present invention provides a hot-rolled wire rod having an iron oxide scale obtained by the control method described in the first aspect on its surface, wherein the thickness of the iron oxide scale is 12 μm to 21 μm.

[0019] The iron oxide scale includes an inner layer of iron oxide scale and an outer layer of iron oxide scale. Based on the thickness of the iron oxide scale, the thickness of the inner layer of iron oxide scale accounts for 70% to 80%, and the thickness of the outer layer of iron oxide scale accounts for 20% to 30%. The inner layer of iron oxide scale includes FeO, and the outer layer of iron oxide scale includes Fe3O4.

[0020] In some preferred embodiments, the microstructure of the wire rod includes ferrite and pearlite, wherein the area ratio of ferrite is 81%-87% and the area ratio of pearlite is 13%-19%, and the grain size of the wire rod is grade 9.5 or higher; the mechanical properties of the wire rod include: tensile strength of 480MPa-510MPa, elongation after fracture ≥38%, and reduction of area ≥69%.

[0021] In the control method provided by this invention, the wire drawing temperature is 850℃-900℃, and after wire drawing, roller cooling is performed. The roller speed is 0.7m / s-1.3m / s. The roller cooling includes a first cooling treatment and a second cooling treatment. The cooling rate of the first cooling treatment is 3℃ / s-5℃ / s, and the final cooling temperature is 740℃-780℃. The cooling rate of the second cooling treatment is 1℃ / s-3℃ / s, and the final cooling temperature is 560℃-600℃. The thickness of the iron oxide scale layer on the surface of the obtained hot-rolled wire rod is 12μm-21μm, and it includes an inner layer and an outer layer. The main component of the inner layer is FeO, and the main component of the outer layer is Fe3O4. The thickness of the inner layer accounts for 70%-80%, and the thickness of the outer layer accounts for 20%-30%, forming an iron oxide scale with a specific structure. This iron oxide scale with a specific structure is not easy to fall off automatically during the storage and transportation of the hot-rolled wire rod, which can prevent further oxidation of the wire rod substrate and is easy to remove by mechanical peeling.

[0022] The winding temperature is limited to 850℃-900℃. If the winding temperature is higher than 900℃, the iron oxide scale layer on the surface of the wire rod is larger than 21μm, which is easily detached during storage and transportation. If the winding temperature is lower than 850℃, the iron oxide scale layer on the surface of the wire rod is smaller than 12μm, which is not easily removed by mechanical stripping. The roller speed is limited to 0.7m / s-1.3m / s, which further makes the iron oxide scale layer on the surface of the wire rod less likely to detach automatically and easier to remove during mechanical stripping. The limited roller cooling process involves first rapidly cooling to 740℃-780℃ at a rate of 3℃ / s-5℃ / s, followed by slow cooling to 560℃-600℃ at a rate of 1℃ / s-3℃ / s. This process ensures that the iron oxide scale layer is of moderate thickness, loose, and easy to detach, guaranteeing that the iron oxide scale can be easily removed during mechanical stripping. If the rapid cooling rate exceeds 5℃ / s, the resulting iron oxide scale layer will be less than 12μm, making it difficult to remove and prone to forming coarse Widmanstätten structures in the wire rod, affecting the stripping, drawing, and cold heading performance of the wire rod.

[0023] The hot-rolled wire rod provided by this invention has an iron oxide scale layer on its surface, comprising an inner iron oxide scale and an outer iron oxide scale. The main component of the inner iron oxide scale is FeO, while the main component of the outer iron oxide scale is Fe3O4. The thickness of the inner iron oxide scale is much greater than that of the outer iron oxide scale. During the storage or transportation of the hot-rolled wire rod, the iron oxide scale is not easily detached automatically and is easily removed during mechanical peeling. The iron oxide scale layer with FeO as the main component is relatively loose, located in the inner layer, and accounts for 70% to 80% of the thickness. The iron oxide scale layer with Fe3O4 as the main component is relatively dense, located in the outer layer, and accounts for 20% to 30% of the thickness. During the storage or transportation of the hot-rolled wire rod, the iron oxide scale is not easily detached automatically and is easily removed during mechanical peeling. If the thickness of the inner iron oxide scale layer with FeO as the main component is greater than 80%, the iron oxide scale is easy to detach automatically; if the thickness of the outer iron oxide scale layer with Fe3O4 as the main component is greater than 30%, the iron oxide scale layer is too dense and not easy to peel off. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a diagram of the iron oxide scale structure of the hot-rolled wire rod produced in Example 1 of the present invention.

[0026] Figure 2 This is a diagram of the iron oxide scale structure of the hot-rolled wire rod produced in Example 2 of the present invention.

[0027] Figure 3 This is a diagram of the iron oxide scale structure of the hot-rolled wire rod produced in Example 3 of the present invention.

[0028] Figure 4 This is a diagram of the iron oxide scale structure of the hot-rolled wire rod produced in Example 4 of the present invention.

[0029] Figure 5 This is a diagram of the iron oxide scale structure of the hot-rolled wire rod produced in Example 5 of the present invention.

[0030] Figure 6 This is a diagram of the iron oxide scale structure of the hot-rolled wire rod produced in Example 6 of the present invention.

[0031] Figure 7 This is a diagram of the iron oxide scale structure of the hot-rolled wire rod produced in Comparative Example 1 of the present invention.

[0032] Figure 8 This is a diagram of the iron oxide scale structure of the hot-rolled wire produced in Comparative Example 2 of the present invention.

[0033] Figure 9 This is a diagram of the iron oxide scale structure of the hot-rolled wire produced in Comparative Example 3 of the present invention.

[0034] Figure 10 This is a diagram of the iron oxide scale structure of the hot-rolled wire produced in Comparative Example 4 of the present invention.

[0035] Figure 11 This is a diagram of the iron oxide scale structure of the hot-rolled wire produced in Comparative Example 5 of the present invention.

[0036] Figure 12 This is a diagram of the iron oxide scale structure of the hot-rolled wire produced in Comparative Example 6 of the present invention.

[0037] Figure 13 This is a diagram of the iron oxide scale structure of the hot-rolled wire produced in Comparative Example 7 of the present invention.

[0038] Figure 14 This is a diagram of the iron oxide scale structure of the hot-rolled wire produced in Comparative Example 8 of the present invention.

[0039] Figure 15 This is a diagram of the iron oxide scale structure of the hot-rolled wire produced in Comparative Example 9 of the present invention.

[0040] Figure 16 This is a diagram of the iron oxide scale structure of the hot-rolled wire rod produced in Comparative Example 10 of the present invention.

[0041] Figure 17 This is a diagram of the iron oxide scale structure of the hot-rolled wire produced in Comparative Example 11 of the present invention. Detailed Implementation

[0042] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0043] The inventors of this invention have discovered that, in the prior art, the iron oxide scale layer on the surface of hot-rolled wire rod directly affects the quality of the steel wire and finished products made from the wire rod. The iron oxide scale layer may fall off automatically, and the exposed metal substrate reacts with oxygen and water vapor in the air to generate red ferric oxide. Ferric oxide is not easily removed during the pickling process in the pickling tank. The iron oxide scale layer may not be easily removed during the mechanical peeling process, and the remaining iron oxide scale remains on the surface of the wire rod. After pickling in the pickling tank and drawing, it will form small black spots with pinhole defects on the surface of the steel wire.

[0044] In this regard, firstly, the present invention provides a method for controlling iron oxide scale on the surface of hot-rolled wire rod, the method comprising:

[0045] Molten steel is smelted, refined and continuously cast in a converter to obtain a billet;

[0046] The billet is heated and descaled;

[0047] The descaled billet is subjected to controlled rolling and controlled cooling to obtain wire rod; the controlled rolling and controlled cooling process includes: roughing, intermediate rolling, finishing, wire drawing and roller cooling;

[0048] The first pre-cooling treatment is performed before the finishing rolling;

[0049] The second pre-cooling treatment is performed before spinning, and the conditions for spinning include: the spinning temperature is 850℃-900℃;

[0050] The roller cooling system has a roller speed of 0.7 m / s to 1.3 m / s and includes a first cooling process and a second cooling process. The conditions for the first cooling process are: roller speed of 0.7 m / s to 1.1 m / s, cooling rate of 3℃ / s to 5℃ / s, and final cooling temperature of 740℃ to 780℃. The conditions for the second cooling process are: roller speed of 0.8 m / s to 1.3 m / s, cooling rate of 1℃ / s to 3℃ / s, and final cooling temperature of 560℃ to 600℃.

[0051] The spinning temperature of this invention can be, for example, 850℃, 855℃, 860℃, 865℃, 870℃, 875℃, 880℃, 885℃, 890℃, 895℃, or 900℃; the roller speed of the first cooling process can be, for example, 0.7m / s, 0.8m / s, 0.9m / s, 1m / s, or 1.1m / s; the cooling rate of the first cooling process can be, for example, 3℃ / s, 3.5℃ / s, 4℃ / s, 4.5℃ / s, or 5℃ / s; and the final cooling temperature of the first cooling process can be, for example, 740℃. The temperatures are 745℃, 750℃, 755℃, 760℃, 765℃, 770℃, 775℃, and 780℃; the roller speed of the second cooling process can be, for example, 0.8m / s, 0.9m / s, 1m / s, 1.1m / s, 1.2m / s, and 1.3m / s; the cooling rate of the second cooling process can be, for example, 1℃ / s, 1.5℃ / s, 2℃ / s, 2.5℃ / s, and 3℃ / s; and the final cooling temperature of the second cooling process can be, for example, 560℃, 570℃, 580℃, 590℃, and 600℃.

[0052] In this invention, molten steel undergoes converter smelting, refining, and continuous casting to obtain a billet. The billet is then heated and descaled before being rolled through roughing, intermediate rolling, finishing rolling, wire rod production, and roller cooling to obtain wire rod. The wire rod production temperature is controlled at 850℃-900℃, and the roller cooling speed is controlled at 0.7m / s-1.3m / s. Roller cooling is achieved by controlling the cooling rate: first, rapid cooling at 3℃ / s-5℃ / s, resulting in a final cooling temperature of 740℃-780℃; then, slow cooling at 1℃ / s-3℃ / s, resulting in a final cooling temperature of 560℃-600℃. After roller cooling, a specific structure is formed on the surface of the wire rod. The iron oxide scale layer, specifically, has a thickness of 12–21 μm and is divided into an inner iron oxide scale layer with FeO as the main component and a thickness of 70%–80%, and an outer iron oxide scale layer with Fe3O4 as the main component and a thickness of 20%–30%. The iron oxide scale layer with this specific structure is not easy to fall off automatically during the storage and transportation of hot-rolled wire rod in the early stage, which can prevent the wire rod matrix from reacting with oxygen and water vapor in the air to generate ferric oxide that is difficult to remove. On the other hand, the iron oxide scale layer is easy to remove during the mechanical peeling process in the later stage, so as to avoid affecting the quality of steel wire and finished products.

[0053] Under the same conditions, if the coiling temperature is above 900℃, the oxidation reaction is rapid, forming an iron oxide scale layer larger than 21μm, which easily detaches automatically during the storage and transportation of the wire rod. If the coiling temperature is below 850℃, the formed iron oxide scale layer is smaller than 12μm, which is not easily removed by mechanical peeling. If the roller conveyor speed is too low (below 0.7m / s for the first cooling process and below 0.8m / s for the second cooling process), the cooling time of the wire rod is too long, easily resulting in an iron oxide scale layer larger than 21μm, which easily detaches automatically. If the roller conveyor speed is too high (below 1.1m / s for the first cooling process and above 1.3m / s for the second cooling process), the cooling time of the wire rod is too short, easily resulting in an iron oxide scale layer smaller than 12μm, which is not easily removed during the mechanical peeling process. If the rapid cooling rate exceeds 5℃ / s, the formed iron oxide scale layer is smaller than 12μm, which is not easily removed and affects the wire rod's... Peeling performance: If the slow cooling rate is less than 1℃ / s, the formed iron oxide scale layer is larger than 21μm, and the iron oxide scale is easy to fall off automatically; if the cooling rate is maintained at 3℃ / s to 5℃ / s throughout the roller cooling process, the formed iron oxide scale layer will be smaller than 12μm, which is not easy to remove and affects the peeling performance of the wire rod; if the cooling rate is maintained at 1℃ / s to 3℃ / s throughout the process, the formed iron oxide scale layer will be larger than 21μm, and the iron oxide scale is easy to fall off automatically; if slow cooling is performed first at 1℃ / s to 3℃ / s, followed by rapid cooling at 3℃ / s to 5℃ / s, the formed iron oxide scale layer will be smaller than 12μm, which is not easy to remove and affects the peeling performance of the wire rod; if the final cooling temperature of the rapid cooling stage is lower than 740℃, the formed iron oxide scale layer will be smaller than 12μm, which is not easy to remove and affects the peeling performance of the wire rod; if the final cooling temperature of the rapid cooling stage is higher than 780℃, the formed iron oxide scale layer will be larger than 21μm, and the iron oxide scale is easy to fall off automatically.

[0054] The control of the coiling temperature in this invention not only affects the formation of iron oxide scale, but also the internal structure and properties of the wire rod. Specifically, if the coiling temperature is below 850°C, it will lead to an increase in the tensile strength of the wire rod, a decrease in elongation after fracture and reduction of area, and a high and coarse Widmanstätten structure. Simultaneously, the control of the roller speed and cooling rate during the roller cooling stage will also affect the internal structure and properties of the wire rod. If the roller speed is too low, if the roller speed of the first cooling treatment is below 0.7 m / s and the roller speed of the second cooling treatment is below 0.8 m / s, it will lead to an increase in the tensile strength of the wire rod, a decrease in elongation after fracture and reduction of area, and a high and coarse Widmanstätten structure. By making... The wire rod is first rapidly cooled at a rate of 3°C / s to 5°C / s to 740°C to 780°C, then slowly cooled at a rate of 1°C / s to 3°C / s to 560°C to 600°C. This process ensures that the microstructure of the wire rod is dominated by ferrite and pearlite, with a grain size of grade 9.5 or higher, a tensile strength of 480MPa-510MPa, an elongation after fracture of 38%, and a reduction of area of ​​69%. This results in the wire rod being qualified for 1 / 2 cold upsetting (the test method for qualified 1 / 2 cold upsetting is to take a wire rod with a height twice its diameter, press the wire rod until the height and diameter are equal, and the wire rod should not crack). This ensures that the strength and plasticity of the wire rod meet the requirements. Under the same conditions, if the cooling rate in the first cooling stage exceeds 5°C / s, coarse Widmanstätten structure is easily formed in the wire rod, affecting the drawing and cold heading performance of the wire rod. If the cooling rate is maintained at 3℃ / s to 5℃ / s during the roller cooling process, Widmanstätten structure will occur, which is not conducive to wire rod drawing.

[0055] In some preferred embodiments, the wire drawing temperature is 860℃~890℃. Under this preferred embodiment, it is more conducive to ensuring the thickness of the iron oxide scale, mechanical properties, metallographic structure and cold heading performance of the wire rod.

[0056] In some preferred embodiments, the chemical composition of the billet is controlled by weight percentage through the converter smelting, refining and continuous casting processes to include: C: 0.17% to 0.23%, Si: 0.17% to 0.30%, Mn: 0.40% to 0.60%, N≤0.007%, P≤0.020%, S≤0.020%, Cr≤0.10%, Ni≤0.15%, Cu≤0.15%, Alt≤0.006%, with the remainder being iron and unavoidable impurities. Carbon (C) is a crucial element in wire rod for wire drawing. Controlling the C content in the cast billet to 0.17%–0.23% is beneficial for ensuring the tensile strength of the wire rod. Furthermore, controlling the C content below 0.23% helps prevent excessively thick primary oxide scale, making it easier to remove during descaling. Controlling the Si content to the lower limit of the standard range, 0.17%–0.30%, helps reduce draw hardening and improves the toughness and plasticity of the wire rod. Controlling the Mn content to 0.40%–0.60% helps control the strength of the wire rod. Controlling the total aluminum (Al) to ≤0.006% helps ensure castability during continuous casting and improves the quality of the cast billet. A reasonable weight percentage range for these elements ensures the strength and toughness of the wire rod and facilitates the wire drawing process. Too low a total element content leads to insufficient tensile strength, while too high a total element content easily causes component segregation, increasing the wire rod's susceptibility to hard phase formation and deteriorating its drawability.

[0057] Preferably, the chemical composition of the billet, by weight percentage, comprises: C: 0.17%–0.22%, Si: 0.17%–0.30%, Mn: 0.40%–0.55%, N ≤ 0.005%, P ≤ 0.018%, S ≤ 0.015%, Cr ≤ 0.08%, Ni ≤ 0.15%, Cu ≤ 0.15%, Alt ≤ 0.006%, with the balance being Fe and unavoidable impurities.

[0058] More preferably, the converter smelting includes adding aluminum blocks to the molten steel between P / 4 tons and P / 3 tons of steel produced by the converter. The amount of aluminum blocks added is adjusted according to the carbon content at the converter endpoint, where the endpoint carbon content is ≥0.08%, and the amount of aluminum blocks added is 0.60 kg / t - 0.70 kg / t. By adding an appropriate amount of aluminum blocks, the oxygen content of the molten steel is kept ≤50 ppm and the molten steel does not contain acid-soluble aluminum components. This is more conducive to solving the problem of high oxygen content in aluminum-free steel, and is also more conducive to ensuring castability during continuous casting and improving the quality of the cast billet.

[0059] More preferably, during the converter smelting process, oxygen is blown from both the top and bottom. During the converter tapping process, under bottom-blown argon conditions, aluminum blocks, ferrosilicon, ferrosilicon, and a recarburizing agent are added sequentially. Between P / 4 tons and P / 3 tons of steel tapped from the converter, ferrosilicon is added to the molten steel. Between P / 4 tons and P / 3 tons of steel tapped from the converter, a recarburizing agent is added. In addition, the tapping time is controlled to be ≥3 minutes, the argon blowing time to be ≥2 minutes, and at the end of tapping, 3 kg / t-4 kg / t of lime and 0.5 kg / t-0.9 kg / t of fluorite are added with the steel stream. This preferred scheme is more conducive to improving the composition hit rate.

[0060] More preferably, the refining includes LF refining, which involves sequentially adding lime and fluorite, treating the slag with submerged arc heating, and then adding a calcium silicate powder deoxidizer to create white slag. In this preferred embodiment, using a calcium silicate powder deoxidizer for slag formation is more effective in solving the difficulty of creating white slag for aluminum-free steel and is more conducive to improving the quality of molten steel. The composition of the calcium silicate powder deoxidizer is: SiC: 9%; Si: 8.8%; Ca: 38%; TC: 5.9%; others: 38.3%.

[0061] More preferably, during the LF refining process, the amount of lime added is 2.9 kg / t to 4.5 kg / t, the amount of fluorite added is 0 kg / t to 1.7 kg / t, the amount of silicon-calcium powder deoxidizer added is 0.5 kg / t to 1.6 kg / t, the white slag holding time is ≥10 minutes, and alloys are added to fine-tune the composition based on the sampling and analysis results of the LF furnace. After the composition and temperature reach the target, seamless calcium wire is fed at 0.3 kg / t to 0.45 kg / t, and the soft blowing time is ≥15 minutes.

[0062] In some preferred embodiments, the heating conditions include: a heating zone temperature of 1020℃~1100℃, a soaking zone temperature of 1060℃~1100℃, and a total heating time of the billet in the heating and soaking zones controlled at 70min~90min. Under this preferred scheme, controlling the heating zone temperature at 1020℃~1100℃ and the soaking zone temperature at 1060℃~1100℃ is more conducive to preventing the formation of excessively thick primary iron oxide scale, which is difficult to remove during the descaling stage. In the later rolling stage, the primary iron oxide scale adhering to the billet is pressed into the billet, causing surface defects such as folds in the wire rod. It also helps prevent the formation of coarse Widmanstätten structures during the controlled cooling stage of the wire rod, further improving the drawing and cold heading performance of the wire rod and preventing drawing fracture or cold heading cracking.

[0063] In some preferred embodiments, high-pressure water is used for descaling, with a maximum pressure of 20 MPa, to ensure that the iron oxide scale generated during the heating process of the billet is completely removed.

[0064] In some preferred embodiments, the conditions for the first pre-cooling treatment include a cooling rate of 20°C / s to 30°C / s; and the conditions for the finishing rolling include a finishing rolling temperature of 820°C to 860°C. In this preferred embodiment, limiting the finishing rolling temperature to 820°C to 860°C allows the wire rod to be rolled in the two-phase region, which is more conducive to increasing the nucleation points of ferrite and promoting the γ / α transformation, as well as refining the ferrite grains, thereby further improving the strength and ductility of the steel. Controlling the cooling rate of the first pre-cooling treatment to above 20°C / s is more conducive to preventing grain growth due to excessively high wire rod temperature, while controlling the cooling rate of the first pre-cooling treatment to below 30°C / s is more conducive to preventing an increase in the ferrite volume fraction of the wire rod, which would lead to a decrease in strength.

[0065] In some preferred embodiments, the conditions for the second pre-cooling treatment include: a cooling rate of 25°C / s to 35°C / s. In this preferred embodiment, a cooling rate of 25°C / s or higher is more conducive to ensuring a spinning temperature of ≤900°C, and a cooling rate of 35°C / s or lower is more conducive to ensuring a spinning temperature of ≥850°C.

[0066] In a second aspect, the present invention provides a hot-rolled wire rod having an iron oxide scale obtained by the control method described in the first aspect on its surface, wherein the thickness of the iron oxide scale is 12 μm to 21 μm.

[0067] The iron oxide scale comprises an inner layer and an outer layer. Based on the thickness of the iron oxide scale, the inner layer accounts for 70%–80% of the total thickness, and the outer layer accounts for 20%–30%. The inner layer comprises FeO, and the outer layer comprises Fe3O4. In this invention, the hot-rolled wire rod has an iron oxide scale layer on its surface comprising an inner layer primarily composed of FeO and an outer layer primarily composed of Fe3O4. The thickness of the inner layer is significantly greater than that of the outer layer. Therefore, the iron oxide scale is less likely to detach automatically during storage or transportation of the hot-rolled wire rod and is easily removed during mechanical peeling.

[0068] In some preferred embodiments, the microstructure of the wire rod comprises ferrite and pearlite, wherein the area ratio of ferrite is 81%-87% and the area ratio of pearlite is 13%-19%, and the grain size of the wire rod is grade 9.5 or higher; the mechanical properties of the wire rod include a tensile strength of 480MPa-510MPa, an elongation after fracture of ≥38%, and a reduction of area of ​​≥69%.

[0069] The present invention will be further described in detail below with reference to specific embodiments.

[0070] Example 1

[0071] The chemical composition of wire rod steel is as follows: C: 0.20%, Si: 0.25%, Mn: 0.45%, N: 0.0047%, P: 0.018%, S: 0.010%, Cr: 0.04%, Ni: 0.02%, Cu: 0.03%, Alt: 0.005%, with the balance being Fe and unavoidable impurities. The smelting and rolling process of wire rod steel is as follows:

[0072] S1: In the converter, steel is smelted using a top and bottom oxygen blowing method. During tapping, the molten steel undergoes deoxidation and alloying. Under bottom-blown argon conditions, when the converter tapping reaches P / 4 tons (total tapping volume of the converter is P tons), 0.61 kg / t of aluminum blocks are added with the steel stream. Also when the converter tapping reaches P / 4 tons, 5.8 kg / t of ferrosilicon manganese (FeMn) is added with the steel stream. 65 Si 17 When the converter tapps to P / 4 tons, 3.7 kg / t of ferrosilicon is added with the steel stream. The grade or composition of the ferrosilicon is FeSi. 72 Al 1.5 When the steel reaches P / 4 tons in the converter, 1.1 kg / t of recarburizing agent is added along with the steel grade. The specific recarburizing agent grade or composition is C: 98%. The composition of the molten steel is adjusted to the lower limit of the range. Finally, 3.1 kg / t of lime and 0.7 kg / t of fluorite are added. The tapping time is 200 s, and the argon blowing time during the tapping process is 150 s.

[0073] S2: 3.2 kg / t of lime and 0.6 kg / t of fluorite are added to the LF refining furnace. After treating the slag with submerged arc heating, 1.6 kg / t of silicon-calcium powder deoxidizer is added to create white slag. The composition of the silicon-calcium powder deoxidizer is SiC: 9%, Si: 8.8%, Ca: 38%, TC: 5.9%, and other: 38.3%. The total FeO and MnO content of the white slag is controlled to be less than 1 wt%, and the white slag holding time is 11 min. Based on the sampling analysis results from the LF furnace, silicon manganese, ferrosilicon, carbon powder, etc., are added to fine-tune the alloy composition. When the composition meets the standard and the temperature reaches 1598℃, 0.42 kg / t of seamless calcium wire is fed in, and the soft blowing time is controlled at 17 min. After refining and continuous casting, a 160 mm × 160 mm square billet is obtained.

[0074] S3: The billet obtained in step S2 is heated. The temperature of the heating section is 1040℃~1090℃ and the heating time is 35min. The temperature of the soaking section is 1070℃~1100℃ and the heating time is 40min. Then, high-pressure water descaling is performed. The maximum pressure of the high-pressure water is 20MPa.

[0075] S4: The billet obtained in step S3 is subjected to controlled rolling and controlled cooling to obtain wire rod. The wire rod undergoes rough rolling, intermediate rolling, first pre-cooling treatment, finish rolling, second pre-cooling treatment, wire drawing, and roller cooling in sequence. The rough rolling temperature is 980℃, the first pre-cooling treatment has a cooling rate of 24℃ / s, the finish rolling temperature is 822℃~850℃, the second pre-cooling treatment has a cooling rate of 33℃ / s, and the wire drawing temperature is 862℃~886℃. Roller cooling includes a first cooling treatment and a second cooling treatment. The first cooling treatment has a cooling rate of 4.6℃ / s, a roller speed of 0.9m / s-1.0m / s, and a final cooling temperature of 746℃-772℃. The second cooling treatment has a cooling rate of 2.3℃ / s, a roller speed of 1.05m / s-1.25m / s, and a final cooling temperature of 565℃-597℃. Afterwards, air cooling is performed. The iron oxide scale structure of the wire rod steel in this embodiment is shown in [reference needed]. Figure 1 .

[0076] Example 2

[0077] The process was carried out in accordance with Example 1, except that the chemical composition of the wire rod steel was as follows: C: 0.19%, Si: 0.23%, Mn: 0.44%, N: 0.0040%, P: 0.016%, S: 0.008%, Cr: 0.05%, Ni: 0.01%, Cu: 0.03%, Alt: 0.004%, with the balance being Fe and unavoidable impurities. The tapping time was 190 s, the argon blowing time during tapping was 140 s, and during the tapping process, 0.64 kg / t of aluminum blocks, 5.6 kg / t of silicon manganese, 3.5 kg / t of ferrosilicon, 1.05 kg / t of carbon raiser, 3.3 kg / t of lime, and 0.89 kg / t of fluorite were added with the steel stream. During the refining process, 2.9 kg / t of lime, 0.5 kg / t of fluorite, and 1.6 kg / t of silica-calcium powder deoxidizer are added. The white slag is maintained for 10.5 min. When the composition meets the standard and the temperature reaches 1602℃, 0.45 kg / t of seamless calcium wire is fed in, and the soft blowing time is controlled at 16 min. The temperature of the heating section is 1030℃~1085℃, and the heating time is 32 min. The temperature of the soaking section is 1065℃~1095℃, and the heating time is 38 min. The roughing temperature is 975℃, the cooling rate of the first pre-cooling treatment is 26℃ / s, the finishing temperature is 825℃~856℃, the cooling rate of the second pre-cooling treatment is 31℃ / s, and the wire drawing temperature is 861℃~888℃. Roller cooling sequentially includes a first cooling treatment and a second cooling treatment. The cooling rate of the first cooling treatment is 4.3℃ / s, the roller speed is 0.95m / s-1.05m / s, and the final cooling temperature is 745℃-775℃. The cooling rate of the second cooling treatment is 2.1℃ / s, the roller speed is 1.1m / s-1.3m / s, and the final cooling temperature is 568℃-600℃, followed by air cooling. The iron oxide scale structure of the wire rod in this embodiment is shown in [reference needed]. Figure 2 .

[0078] Example 3

[0079] The process was carried out in accordance with Example 1, except that the chemical composition of the wire rod steel was as follows: C: 0.20%, Si: 0.25%, Mn: 0.48%, N: 0.0036%, P: 0.015%, S: 0.007%, Cr: 0.05%, Ni: 0.02%, Cu: 0.03%, Alt: 0.005%, with the balance being Fe and unavoidable impurities. The tapping time was 205s, the argon blowing time during tapping was 130s, and during the tapping process, 0.66kg / t of aluminum blocks, 6.28kg / t of silicon manganese, 3.03kg / t of ferrosilicon, 1.12kg / t of carbon raiser, 3.31kg / t of lime, and 0.69kg / t of fluorite were added with the steel stream. During the refining process, 3.11 kg / t of lime, 0.50 kg / t of fluorite, and 1.55 kg / t of calcium silicate deoxidizer are added. The white slag is held for 12 minutes. When the composition meets the standard and the temperature reaches 1600℃, 0.41 kg / t of seamless calcium wire is fed in, and the soft blowing time is controlled at 15 minutes. The temperature of the heating section is 1040℃~1085℃, and the heating time is 36 minutes. The temperature of the soaking section is 1070℃~1100℃, and the heating time is 42 minutes. The roughing temperature is 976℃, the cooling rate of the first pre-cooling treatment is 27℃ / s, the finishing temperature is 828℃~860℃, the cooling rate of the second pre-cooling treatment is 32℃ / s, and the wire drawing temperature is 863℃~885℃. Roller cooling sequentially includes a first cooling treatment and a second cooling treatment. The cooling rate of the first cooling treatment is 4.5℃ / s, the roller speed is 0.95m / s-1.1m / s, and the final cooling temperature is 750℃-778℃. The cooling rate of the second cooling treatment is 2.4℃ / s, the roller speed is 1.1m / s-1.25m / s, and the final cooling temperature is 565℃-596℃, followed by air cooling. The iron oxide scale structure of the wire rod in this embodiment is shown in [reference needed]. Figure 3 .

[0080] Example 4

[0081] The process was carried out in accordance with Example 1, except that the chemical composition of the wire rod steel was as follows: C: 0.12%, Si: 0.15%, Mn: 0.35%, N: 0.0049%, P: 0.017%, S: 0.011%, Cr: 0.06%, Ni: 0.02%, Cu: 0.02%, Alt: 0.004%, with the balance being Fe and unavoidable impurities. The tapping time was 190s, the argon blowing time during tapping was 135s, and during the tapping process, 0.64kg / t of aluminum blocks, 4.14kg / t of silicon manganese, 2.27kg / t of ferrosilicon, 0.34kg / t of carbon raiser, 3.5kg / t of lime, and 0.78kg / t of fluorite were added with the steel stream. During the refining process, 3.01 kg / t of lime, 0.34 kg / t of fluorite, and 1.71 kg / t of calcium silicate deoxidizer are added. The white slag is held for 10.5 min. When the composition meets the standard and the temperature reaches 1599℃, 0.4 kg / t of seamless calcium wire is fed in, and the soft blowing time is controlled at 15 min. The temperature of the heating section is 1055℃-1096℃, and the heating time is 34 min. The temperature of the soaking section is 1070℃-1098℃, and the heating time is 38 min. The roughing temperature is 985℃, the cooling rate of the first pre-cooling treatment is 26℃ / s, the finishing temperature is 825℃-855℃, the cooling rate of the second pre-cooling treatment is 31℃ / s, and the wire drawing temperature is 862℃-886℃. Roller cooling sequentially includes a first cooling treatment and a second cooling treatment. The first cooling treatment has a cooling rate of 4.5℃ / s, a roller speed of 0.9m / s-1.0m / s, and a final cooling temperature of 748℃-776℃. The second cooling treatment has a cooling rate of 2.4℃ / s, a roller speed of 1.05m / s-1.25m / s, and a final cooling temperature of 563℃-594℃, followed by air cooling. The iron oxide scale structure of the wire rod in this embodiment is shown in [reference needed]. Figure 4 .

[0082] Example 5

[0083] The process was carried out in accordance with Example 1, except that the roller speed for the first cooling treatment was 0.7 m / s-0.85 m / s, and the roller speed for the second cooling treatment was 0.8 m / s-0.95 m / s. The iron oxide scale structure of the wire rod steel in this example is shown below. Figure 5 .

[0084] Example 6

[0085] The procedure was carried out in accordance with Example 1, except that the wire drawing temperature was 880℃-900℃. The iron oxide scale structure of the wire rod in this example is shown below. Figure 6 .

[0086] Comparative Example 1

[0087] The procedure was carried out in accordance with Example 1, except that the wire drawing temperature was 810℃-840℃. The iron oxide scale structure of the wire rod in this example is shown below. Figure 7 .

[0088] Comparative Example 2

[0089] The procedure was carried out in accordance with Example 1, except that the wire drawing temperature was 905-930℃. The iron oxide scale microstructure of the wire rod in this example is shown below. Figure 8 .

[0090] Comparative Example 3

[0091] The process was carried out in accordance with Example 1, except that the roller speed for the first cooling treatment was 0.3 m / s to 0.6 m / s. The iron oxide scale microstructure of the wire rod steel in this example is shown below. Figure 9 .

[0092] Comparative Example 4

[0093] The process was carried out in accordance with Example 1, except that the roller speed for the first cooling treatment was 1.2 m / s to 1.4 m / s. The iron oxide scale structure of the wire rod steel in this example is shown below. Figure 10 .

[0094] Comparative Example 5

[0095] The procedure was carried out in accordance with Example 1, except that the roller speed for the second cooling process was 0.5 m / s to 0.75 m / s. The iron oxide scale microstructure of the wire rod steel in this example is shown below. Figure 11 .

[0096] Comparative Example 6

[0097] The process was carried out in accordance with Example 1, except that the roller speed for the second cooling treatment was 1.35 m / s to 1.6 m / s. The iron oxide scale microstructure of the wire rod steel in this example is shown below. Figure 12 .

[0098] Comparative Example 7

[0099] The process was carried out in accordance with Example 1, except that the cooling rate of the first cooling treatment was 6°C / s. The iron oxide scale structure of the wire rod steel in this example is shown below. Figure 13 .

[0100] Comparative Example 8

[0101] The process was carried out in accordance with Example 1, except that the cooling rate of the second cooling treatment was 0.5°C / s. The iron oxide scale microstructure of the wire rod steel in this example is shown below. Figure 14 .

[0102] Comparative Example 9

[0103] The process is carried out in accordance with Example 1, except that a second cooling treatment is not performed, and the final cooling temperature of the first cooling treatment is 471℃-518℃. The iron oxide scale microstructure of the wire rod steel in this example is shown below. Figure 15 .

[0104] Comparative Example 10

[0105] The process is carried out in accordance with Example 1, except that the first cooling treatment is omitted, and the final cooling temperature of the second cooling treatment is 612℃-641℃. The iron oxide scale structure of the wire rod steel in this example is shown below. Figure 16 .

[0106] Comparative Example 11

[0107] The process is carried out in accordance with Example 1, except that the cooling treatment is first performed at the cooling rate of the second cooling treatment, with a final cooling temperature of 780℃-810℃, and then the cooling treatment is performed at the cooling rate of the first cooling treatment, with a final cooling temperature of 600℃-635℃. The iron oxide scale structure of the wire rod steel in this example is shown in [reference needed]. Figure 17 .

[0108] Test case

[0109] The microstructure of the wire rod was tested according to GB / T 13298.

[0110] The grain size of the wire rods was tested in accordance with GB / T6394.

[0111] The tensile strength, elongation after fracture, and reduction of area of ​​wire rod shall be tested in accordance with GB / T 228.

[0112] Cold heading of wire rod shall be tested in accordance with YB / T5293.

[0113] The thickness, composition, and morphology (porosity) of the iron oxide scale in the wire rod were detected using scanning electron microscopy. Table 2 shows the thicknesses of the inner FeO layer and the outer Fe3O4 layer, as well as the thickness ratio of the inner FeO layer to the outer Fe3O4 layer, which are the average values ​​obtained after measuring the thicknesses of the inner FeO layer and the outer Fe3O4 layer at five locations in the sample.

[0114] The test results of the microstructure and properties of the wire rods of Examples 1-6 and Comparative Examples 1-11 are shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] The test results of the microstructure and properties of the iron oxide scale in Examples 1-6 and Comparative Examples 1-11 are shown in Table 2. (The column for automatic detachment of iron oxide scale in Table 2, which states "uneven thickness", refers to the uneven thickness of the iron oxide scale layer caused by the detachment of iron oxide scale during the storage and transportation of hot-rolled wire rod.)

[0119] Table 2

[0120]

[0121]

[0122] By comparing Examples 1-6 with Comparative Examples 1-11, it can be seen that controlling the wire drawing temperature to be no lower than 850℃ helps prevent the iron oxide scale layer from being too thin, forming a reasonably structured inner FeO layer and outer Fe3O4 layer. This makes the iron oxide scale easier to detach during the mechanical peeling stage, controls tensile strength, and increases elongation at break and cross-sectional area shrinkage. Controlling the wire drawing temperature to be no higher than 900℃ helps prevent the iron oxide scale layer from being too thick, forming a reasonably structured inner FeO layer and outer Fe3O4 layer. This results in a more uniform iron oxide scale layer thickness, making it less prone to automatic detachment and preventing wire rod rusting, thus affecting quality. Controlling the roller speed of the first cooling treatment to be no lower than 0.7 m / s helps to make the iron oxide scale layer thickness more uniform, making it less prone to automatic detachment and preventing wire rod rusting. This also controls tensile strength and increases elongation at break and cross-sectional area shrinkage. By controlling the roller speed of the first cooling process to be no higher than 1.1 m / s, it is easier to prevent the iron oxide scale layer from being too thin, forming a reasonably structured inner FeO layer and outer Fe3O4 layer, making the iron oxide scale easier to remove during the mechanical peeling stage. By controlling the roller speed of the second cooling process to be no lower than 0.8 m / s, it is easier to prevent the iron oxide scale layer from being too thick, forming a reasonably structured inner FeO layer and outer Fe3O4 layer, resulting in a more uniform iron oxide scale thickness, making it less prone to automatic detachment, preventing wire rod rusting, controlling tensile strength, and increasing elongation at break and cross-sectional area shrinkage. By controlling the roller speed of the second cooling process to be no higher than 1.3 m / s, it is easier to prevent the iron oxide scale layer from being too thin, forming a reasonably structured inner FeO layer and outer Fe3O4 layer, making the iron oxide scale easier to remove during the mechanical peeling stage. By controlling the cooling rate of the first cooling treatment to be no higher than 5℃ / s, it is easier to prevent the iron oxide scale layer from being too thin, forming a reasonably structured inner FeO layer and outer Fe3O4 layer, making the iron oxide scale easier to remove during the mechanical peeling stage. By controlling the cooling rate of the second cooling treatment to be no lower than 1℃ / s, it is easier to prevent the iron oxide scale layer from being too thick, forming a reasonably structured inner FeO layer and outer Fe3O4 layer, resulting in a more uniform iron oxide scale thickness, making it less likely to fall off automatically, and preventing the wire rod from rusting.By first subjecting the iron oxide scale to rapid cooling at 3-5℃ / s, followed by slow cooling at 1-3℃ / s, compared to direct rapid cooling to the final cooling temperature, it is more effective in preventing the iron oxide scale layer from becoming too thin. This results in the formation of a structurally sound inner FeO layer and outer Fe3O4 layer, making the iron oxide scale easier to detach during the mechanical peeling stage. It also helps control tensile strength and increases elongation at fracture and sectional expansion. Furthermore, compared to direct slow cooling to the final cooling temperature, it is more effective in preventing the iron oxide scale layer from becoming too thick, forming a structurally sound inner FeO layer and outer Fe3O4 layer. The iron oxide scale thickness is more uniform, less prone to automatic detachment, preventing rusting of the wire rod, controlling tensile strength, and increasing elongation at fracture and sectional expansion. Finally, compared to slow cooling followed by rapid cooling to the final cooling temperature, it is more effective in preventing the iron oxide scale layer from becoming too thin, forming a structurally sound inner FeO layer and outer Fe3O4 layer. This makes the iron oxide scale easier to detach during the mechanical peeling stage, controlling tensile strength, and increasing elongation at fracture and sectional expansion.

[0123] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for controlling iron oxide scale on the surface of hot-rolled wire rod, characterized in that, The method includes: Molten steel is smelted, refined and continuously cast in a converter to obtain a billet; The billet is heated and descaled; The descaled billet is subjected to controlled rolling and controlled cooling to obtain wire rod; the controlled rolling and controlled cooling process includes: roughing, intermediate rolling, finishing, wire drawing and roller cooling; The first pre-cooling treatment is performed before the finishing rolling; the conditions for the first pre-cooling treatment include a cooling rate of 20℃ / s to 30℃ / s; the conditions for the finishing rolling include a finishing rolling temperature of 820℃ to 860℃. The second pre-cooling treatment is performed before spinning, with a cooling rate of 25℃ / s to 35℃ / s. The conditions for spinning include a spinning temperature of 850℃ to 900℃. The roller cooling system has a roller speed of 0.7 m / s to 1.3 m / s and includes a first cooling process and a second cooling process. The conditions for the first cooling process are: roller speed of 0.7 m / s to 1.1 m / s, cooling rate of 3℃ / s to 5℃ / s, and final cooling temperature of 740℃ to 780℃. The conditions for the second cooling process are: roller speed of 0.8 m / s to 1.3 m / s, cooling rate of 1℃ / s to 3℃ / s, and final cooling temperature of 560℃ to 600℃. The microstructure of the hot-rolled wire rod includes ferrite and pearlite, wherein the area ratio of ferrite is 81%-87% and the area ratio of pearlite is 13%-19%.

2. The control method according to claim 1, characterized in that, The conditions for the second pre-cooling treatment include: the spinning temperature is 860℃~890℃.

3. The control method according to claim 1, characterized in that, The heating conditions include: the temperature of the heating section is 1020℃~1100℃, the temperature of the soaking section is 1060℃~1100℃, and the total heating time of the billet in the heating section and the soaking section is controlled within 70min~90min.

4. The control method according to claim 1, characterized in that, Through the converter smelting, refining and continuous casting processes, the chemical composition of the billet is controlled to include, by weight percentage: C: 0.17%–0.23%, Si: 0.17%–0.30%, Mn: 0.40%–0.60%, N≤0.007%, P≤0.020%, S≤0.020%, Cr≤0.10%, Ni≤0.15%, Cu≤0.15%, Alt≤0.006%, with the remainder being iron and unavoidable impurities.

5. The control method according to claim 4, characterized in that, The converter smelting process includes: the total steel output of the converter is P tons; between P / 4 tons and P / 3 tons of steel output, aluminum blocks are added to the molten steel; the amount of aluminum blocks added is adjusted according to the carbon content at the converter endpoint, where the carbon content at the endpoint is ≥0.08%, and the amount of aluminum blocks added is 0.60 kg / t - 0.70 kg / t.

6. The control method according to claim 4, characterized in that, The refining process includes LF refining, which involves sequentially adding lime and fluorite, treating the slag with submerged arc heating, and then adding calcium silicate powder as a deoxidizer to create white slag.

7. A hot-rolled wire rod, characterized in that, Its surface has an iron oxide scale obtained by the control method according to any one of claims 1-6, wherein the thickness of the iron oxide scale is 12 μm to 21 μm; The iron oxide scale includes an inner layer of iron oxide scale and an outer layer of iron oxide scale. Based on the thickness of the iron oxide scale, the thickness of the inner layer of iron oxide scale accounts for 70% to 80%, and the thickness of the outer layer of iron oxide scale accounts for 20% to 30%. The inner layer of iron oxide scale includes FeO, and the outer layer of iron oxide scale includes Fe3O4.

8. The hot-rolled wire rod according to claim 7, characterized in that, The grain size of the wire rod is grade 9.5 or higher; the mechanical properties of the wire rod include: tensile strength of 480MPa-510MPa, elongation after fracture ≥38%, and reduction of area ≥69%.

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