A steel for heavy-duty axle brake drums and a method of manufacturing the same

Abstract

The application discloses a kind of heavy axle brake drum steel and manufacturing method thereof, belong to metallurgical rolling technical field, comprising: converter smelting, LF refining, slab continuous casting, rolling and sampling inspection;The chemical composition of prepared steel material includes by mass percent, C: 0.04~0.06%, Si≤0.05%, Mn: 0.30~0.70%, P≤0.015%, S≤0.005%, Al: 0.02~0.05%, Ti: 0.010~0.050%, O≤0.002%, the balance is Fe and unavoidable impurities;Wherein, in the rolling step, finish rolling temperature is controlled at 820~840 DEG C, and then high-temperature austenite is rapidly cooled to 570~600 DEG C with the cooling rate of 25~35 DEG C / s The temperature interval of coiling temperature zone.The application is used to solve the problem of spinning cracking in the processing of heavy axle brake drum steel.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical rolling technology, specifically relating to a steel for brake drums of heavy-duty vehicle axles and its manufacturing method. Background Technology

[0002] The core function of heavy-duty vehicle axle brake drums is to provide reliable braking protection for high-load, high-intensity transportation scenarios. Bimetallic brake drums utilize the excellent frictional properties, wear resistance, and thermal conductivity of the inner gray cast iron layer, while the outer layer bears the tensile stress during braking. The superior tensile strength, high elasticity, and toughness of steel effectively prevent the brake drum from cracking under heavy loads and high temperatures. Due to their excellent resistance to heat fade and structural strength, bimetallic brake drums are widely used in heavy-duty tractors, semi-trailers, and other highway transport vehicles. The combination of high-strength steel on the outer layer and wear-resistant gray cast iron on the inner layer effectively solves the problem of high-temperature cracking caused by frequent braking, making them particularly suitable for long-distance mountainous roads and high-load freight scenarios.

[0003] Technical bottlenecks in the spinning cracking of brake drum steel for heavy-duty vehicle axles: (1) The spinning process of brake drum intensifies internal stress concentration and accelerates crack initiation. In addition, weak links such as banded structures or local non-metallic inclusions become crack sources; (2) Insufficient strength of the base material leads to stress concentration cracking during spinning; (3) High strength will increase spinning load and stress concentration cracking; (4) Low elongation will significantly reduce the resistance to deformation and increase the risk of crack initiation.

[0004] In summary, the technical bottlenecks in the spinning cracking process of brake drum steel for heavy-duty vehicle axles are how to eliminate banded structures, local non-metallic inclusions, and control large fluctuations in mechanical properties.

[0005] The patent application filed by Zhang Zhigang et al., titled "A 400MPa Grade Fine-Grained Ferritic Steel Strip for Automobile Brake Drums and Its Preparation Method," mentions KR desulfurization, requiring ≥95% slag removal from the surface of the molten iron ladle, increasing steelmaking costs by 48 yuan / ton. The patent specification states that an elongation rate of 45%–53% meets user needs. However, to increase the elongation rate to 55%–60%, the key factor is the final rolling temperature control mentioned in the patent specification, which is 850–870℃. Slightly higher temperatures cause coarsening of the ferrite grains, reducing the material's elongation. In conclusion, this patent does not meet the requirements for heavy-duty vehicle axle brake drums, whose core function is high-load, high-intensity transportation scenarios, making it unsuitable for large-scale production by most enterprises in a market economy.

[0006] The patent application filed by Peng Chong et al., entitled "A Steel for Brake Drums and Its Manufacturing Method," mentions in its first claim that C: 0.08%–0.10%, Mn: 0.50%–0.80%, and La+Ce: 0.002%–0.004%. Due to the excessively high C content, carbon atoms hinder dislocation movement, reducing the material's deformability, resulting in an elongation of only 41%–44% as stated in Clause 71 of the specification. The excessively high Mn content, the intentional addition of precious rare earth metals La+Ce, and the increased desulfurization of molten iron significantly increase the unnecessary costs of the steelmaking process. In summary, this patent does not meet the requirements for heavy-duty vehicle axle brake drums, whose core function is high-load, high-intensity transportation scenarios, and is not conducive to large-scale production by most enterprises in a market economy.

[0007] The patent application filed by Guo Bin et al., entitled "A Steel for Bimetallic Brake Drums and a Method for Preparing Hot-Rolled Steel Strips Therein," mentions in its first claim that the steel composition is C: 0.06%–0.09%, Mn: 0.90%–1.10%, and Mg: 0.0005%–0.0020%. Due to the excessively high C content, carbon atoms hinder dislocation movement, reducing the material's deformability, resulting in an elongation of ≤38% as stated in claims 27–69 of the specification, which is too low. The high Mn content, intentionally adding the precious metal Mg, increases the cost of desulfurization of molten iron, significantly increasing unnecessary expenses in the steelmaking process. In summary, this patent does not meet the requirements for heavy-duty vehicle axle brake drums, whose core function is high-load, high-intensity transportation scenarios, and is not conducive to large-scale production by most enterprises in a market economy.

[0008] The patent application filed by Wan Guoxi et al., entitled "A Steel Belt for Composite Brake Drum and Its Production Method," mentions in clauses 13-24 that C is 0.05%-0.08% and Mn is 1.00%-1.15%. Due to the excessively high C content, carbon atoms hinder dislocation movement, reducing the material's deformability, resulting in an elongation of 34%-35% as stated in clauses 13-24, which is too low. The high Mn content also significantly increases unnecessary costs in the steelmaking process. In conclusion, this patent does not meet the requirements for heavy-duty vehicle axle brake drums, whose core function is high-load, high-intensity transportation scenarios, and is not conducive to large-scale production by most enterprises in a market economy. Summary of the Invention

[0009] To address the technical problems existing in the prior art, this invention provides a steel for brake drums of heavy-duty vehicle axles and its manufacturing method, which solves the problem of spinning cracking during the processing of steel for brake drums of heavy-duty vehicle axles.

[0010] The first objective of this invention is to provide a method for manufacturing steel for brake drums of heavy-duty vehicle axles, comprising, in sequence: converter smelting, LF refining, slab continuous casting, rolling, and sampling inspection; the chemical composition of the steel prepared by the method, in mass percentage, comprises: C: 0.04%–0.06%, Si≤0.05%, Mn: 0.30%–0.70%, P≤0.015%, S≤0.005%, Al: 0.02%–0.05%, Ti: 0.010%–0.050%, O≤0.002%, with the balance being Fe and unavoidable impurities; In the rolling step, the finishing rolling temperature is controlled at 820℃~840℃, and then the high-temperature austenite is rapidly cooled to the coiling temperature range of 570℃~600℃ at a cooling rate of 25℃ / s~35℃ / s.

[0011] Preferably, the converter smelting includes converter decompression C: 0.03%~0.04%, strengthening the stirring of the molten pool through top and bottom re-blowing, and the carbon-oxygen product ≤0.0025%; slag washing, sequentially adding: lime 2.5kg / t~2.8kg / t, aluminum blocks 1.4kg / t~1.6kg / t, calcium carbide 0.25kg / t~0.35kg / t, silicon carbide 0.15kg / t~0.25kg / t, deep deoxidation to ensure argon station [O]: 0.0005%~0.0020%, early slag formation, and converter slag melting point ≤1540℃.

[0012] Preferably, the LF refining includes: using calcium carbide and silicon carbide for composite diffusion deoxidation and extreme desulfurization, the refining slag melting point is ≤1500℃, and the remaining non-metallic inclusions are modified by calcium treatment to generate nano-scale non-metallic inclusions that are diffusely distributed.

[0013] Preferably, the LF refining process includes: from molten steel to LF, 6.5 kg / t to 7.5 kg / t of lime and 0.5 kg / t to 1.5 kg / t of fluorite in converter + LF, 0.55 kg / t to 0.65 kg / t of calcium carbide in converter + LF, and 0.25 kg / t to 0.35 kg / t of silicon carbide in converter + LF. Calcium carbide and silicon carbide are used for composite diffusion deoxidation and extreme desulfurization, with S ≤ 0.003% and [O] ≤ 0.0010%. The refining slag has a melting point ≤ 1500℃. The low-melting-point slag adsorbs large-sized non-metallic inclusions. Pure calcium wire is used to modify residual MnS and Al2O3 at a speed of 3.0 m / s to 4.0 m / s to generate nano-sized non-metallic inclusions that are diffusely distributed.

[0014] Preferably, the slab continuous casting is carried out under low superheat conditions. By optimizing the electromagnetic stirring of the crystallizer, dynamic light pressure and the cooling capacity of the secondary cooling zone, the center segregation of the slab reaches the C0.5 level.

[0015] Preferably, the slab continuous casting includes: full-process protective casting of slabs, optimized crystallizer electromagnetic stirring 350A / 7Hz, dynamic light pressure reduction of 4.0mm to 4.5mm, and secondary cooling zone water volume of 0.8L / kg to 1.0L / kg under the premise of superheat of 10℃ to 25℃, and comprehensive process optimization.

[0016] Preferably, the rolling process includes: heating, having an intermediate billet thickness of 53 mm, and increasing the roughing reduction.

[0017] Preferably, the sampling inspection includes: obtaining a grain size ≥ 9.0, a ferrite + pearlite structure, a yield strength of 300MPa~320MPa, a tensile strength of 400MPa~420MPa, and an elongation of 55%~60% through sampling inspection.

[0018] A second objective of the present invention is to provide a steel for brake drums of heavy-duty vehicle axles, which is obtained by the above-described method for manufacturing steel for brake drums of heavy-duty vehicle axles.

[0019] A third objective of the present invention is to provide a brake drum for heavy-duty vehicle axles, which is made of the steel used for brake drums of heavy-duty vehicle axles as described above.

[0020] The advantages and positive effects of this invention are: This invention is suitable for overcoming technical bottlenecks in the entire process of steelmaking, continuous casting, and rolling. Optimization of the slag system from converter to LF: Optimizing the slag washing structure and addition sequence, advancing slag formation, deep deoxidation, rapid low-melting-point refining slag in LF refining, extreme desulfurization, removal of large-sized non-metallic inclusions, and calcium treatment to fully denature residual non-metallic inclusions; Elimination of center segregation in slab continuous casting: Optimizing the crystallizer electromagnetic stirring, dynamic light reduction, and secondary cooling capacity under low superheat conditions, achieving a C0.5 level for slab center segregation, providing a prerequisite for obtaining 0A-grade banded slabs; After heating, the intermediate slab thickness is 53 μm. The roughing reduction is increased; the finishing rolling temperature is 820℃~840℃, rolling in the austenitic region, which can fully utilize the high plastic deformation capacity of austenite. At the same time, dynamic recrystallization refines the austenite grains, and rapid cooling in the front section of dense laminar flow cooling inhibits austenite grain growth. The high-temperature austenite is rapidly cooled to the coiling temperature range of 570℃~600℃ at a cooling rate of 25℃ / s~35℃ / s, which inhibits pearlite transformation and promotes the precipitation of small-sized non-metallic inclusions in nanoscale form, greatly improving elongation. This yields heavy-duty vehicle axle brake drum steel with a grain size ≥9.0, ferrite + a small amount of pearlite structure, yield strength of 300MPa~320MPa, tensile strength of 400MPa~420MPa, and elongation of 55%~60%. Attached Figure Description

[0021] Figure 1This is a 500X high-magnification image of the core tissue of a control example in a preferred embodiment of the present invention, grade 8.0. Figure 2 These are 500X high-magnification images of the core tissue of Examples 1-4 in the preferred embodiments of the present invention, with a grade of 9.5. Detailed Implementation

[0022] To make the above-mentioned objectives, control system design, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] like Figures 1 to 2 As shown, the technical solution of the present invention is as follows: A method for preparing steel for brake drums of heavy-duty vehicle axles includes, in sequence: converter smelting, LF refining, slab continuous casting, rolling, and sampling inspection; the chemical composition of the steel prepared by the method, by mass percentage, includes: C: 0.04%~0.06%, Si≤0.05%, Mn: 0.30%~0.70%, P≤0.015%, S≤0.005%, Al: 0.02%~0.05%, Ti: 0.010%~0.050%, O≤0.002%, with the balance being Fe and unavoidable impurities; In the rolling step, the finishing rolling temperature is controlled at 820℃~840℃, and then the high-temperature austenite is rapidly cooled to the coiling temperature range of 570℃~600℃ at a cooling rate of 25℃ / s~35℃ / s.

[0024] To better understand the technical solution of this invention, each step will be explained in detail below: Step 1: After converter smelting, the steel slag is washed to form low-melting-point slag in advance. Specifically: Converter slag washing: C: 0.03%~0.04%, enhanced molten pool stirring through top and bottom reblowing, carbon-oxygen product ≤0.0025%; slag washing, adding in sequence: lime 2.5kg / t~2.8kg / t, aluminum blocks 1.4kg / t~1.6kg / t, calcium carbide 0.25kg / t~0.35kg / t, silicon carbide 0.15kg / t~0.25kg / t, deep deoxidation to ensure argon station [O]: 0.0005%~0.0020%, early slag formation, converter slag melting point ≤1540℃, providing a good kinetic and thermodynamic basis for LF.

[0025] Step 2: The molten steel is refined at LF (Lead-Layer Refining), rapidly producing low-melting-point refining slag and undergoing extreme desulfurization to remove large inclusions. Calcium treatment modifies residual MnS and Al2O3 non-metallic inclusions, generating nano-sized non-metallic inclusions that are diffusely distributed. Specifically: From molten steel to LF, the lime in the converter + LF is 6.5 kg / t to 7.5 kg / t, the fluorite is 0.5 kg / t to 1.5 kg / t, the calcium carbide in the converter + LF is 0.55 kg / t to 0.65 kg / t, and the silicon carbide in the converter + LF is 0.25 kg / t to 0.35 kg / t. Calcium carbide and silicon carbide are used for composite diffusion deoxidation and extreme desulfurization, with S≤0.003% and [O]≤0.0010%. The melting point of the refining slag is ≤1500℃. The low melting point slag adsorbs large-sized non-metallic inclusions. The pure calcium line modifies the residual MnS and Al2O3 at a speed of 3.0 m / s to 4.0 m / s, generating nano-sized non-metallic inclusions that are diffusely distributed.

[0026] Step 3: Continuous casting from molten steel to slab, optimizing the entire process under low superheat conditions, including electromagnetic stirring in the crystallizer, dynamic light reduction, and cooling capacity in the secondary cooling zone. Specifically: The continuous casting of slabs is protected throughout the casting process. Under the premise of superheating of 10-25℃, the process is optimized in all aspects, including electromagnetic stirring of 350A / 7Hz in the crystallizer, dynamic light pressure reduction of 4.0mm-4.5mm, and water content in the secondary cooling zone of 0.8L / kg-1.0L / kg. The segregation at the center of the slab reaches C0.5 grade, which provides the prerequisite for obtaining 0A grade banded slabs.

[0027] Step 4 involves heating, increasing the rough rolling reduction, and then finishing the rolling process in the austenitic region. Low coiling inhibits pearlite transformation, promoting the precipitation of small-sized non-metallic inclusions in a nanoscale morphology. Specifically: After heating, the intermediate billet thickness is 53mm to increase the rough rolling reduction; the finishing rolling temperature is 820℃~840℃, which is rolled in the austenite region. This can make full use of the high plastic deformation capacity of austenite. At the same time, the austenite grains are refined through dynamic recrystallization. The rapid cooling in the front section of the dense laminar flow cooling can suppress the growth of austenite grains. The high-temperature austenite is rapidly cooled to the coiling temperature range of 570℃~600℃ at a cooling rate of 25℃ / s~35℃ / s, which suppresses the pearlite transformation and promotes the precipitation of small-sized non-metallic inclusions in the form of nanoscale, which greatly improves the elongation.

[0028] Step 5: Sampling and testing revealed extremely fine grain size and excellent mechanical properties. Specifically: After sampling and testing, a steel for brake drums of heavy-duty vehicle axles was obtained with a grain size ≥9.0, a ferrite + a small amount of pearlite structure, a yield strength of 300MPa~320MPa, a tensile strength of 400MPa~420MPa, and an elongation of 55%~60%.

[0029] Comparative Examples and Examples 1-4: Table 1 shows the chemical composition of the comparative examples and Examples 1 to 4 of the present invention.

[0030] Table 1 Chemical Composition

[0031] See Table 1. The comparative example is the brake drum process for heavy-duty vehicle axles in traditional steel enterprises. Due to the high carbon content, carbon atoms hinder dislocation movement, reducing the material's deformation capacity and elongation. The high Mn content and the presence of the precious metal Nb significantly increase the cost of unnecessary expenditures in the steelmaking process.

[0032] Examples 1-4 describe the steel process for brake drums of high-performance heavy-duty vehicle axles. The low-carbon and low-manganese composition design has significant cost advantages, and the enhanced controlled rolling and cooling improve mechanical properties. The steel has S≤0.003%, [O]≤0.0010%, and the melting point of the refining slag is ≤1500℃. The low-melting-point slag adsorbs large-sized non-metallic inclusions, resulting in high-purity molten steel.

[0033] Table 2 shows the key steelmaking process parameters of the comparative examples and Examples 1-4 of this invention.

[0034] Table 2 Key process parameters for steelmaking

[0035] See Table 2. The control example is the brake drum process for heavy-duty vehicle axles in traditional steel enterprises. The lime + fluorite ratio is 10.0 kg / t, resulting in a large slag volume and high cost. Ineffective slag material did not achieve the ultimate desulfurization effect, resulting in an LF endpoint S of 0.005%, which is relatively well controlled. The slag melting point is 1528℃, which can effectively adsorb non-metallic inclusions. The superheat of 28℃ is relatively high. Under the process control of secondary cooling water ratio of 0.6 L / kg, crystallizer electromagnetic stirring of 300A / 6Hz, and dynamic light pressure reduction of 3.5 mm, the TiN non-metallic inclusions are severely agglomerated, and the central segregation C2.5 is relatively good, which basically meets the requirements.

[0036] Examples 1-4 illustrate the high-performance steel process for brake drums in heavy-duty vehicle axles. The process involves using 6.5 kg / t to 7.5 kg / t of lime and 0.5 kg / t to 1.5 kg / t of fluorite in a converter + LF process, reducing slag volume and lowering costs. Combined with 0.55 kg / t to 0.65 kg / t of calcium carbide and 0.25 kg / t to 0.35 kg / t of silicon carbide in a converter + LF process for composite deoxidation, the final sulfur content (S) in the LF process is ≤0.003%, achieving optimal desulfurization. The slag melting point is 1455℃ to 1465℃, and the liquid slag allows for better adsorption of non-metallic inclusions. The superheat is 12℃ to 23℃. With a secondary cooling water ratio of 0.9 L / kg, a crystallizer electromagnetic stirring of 350 A / 7 Hz, and a dynamic light pressure reduction of 4.3 mm, the process significantly reduces the agglomeration of non-metallic inclusions, achieving a C0.5 grade central segregation, providing a prerequisite for obtaining 0A grade banded inclusions.

[0037] Table 3 shows the key rolling process parameters of the comparative examples and Examples 1-4 of this invention. Table 3 Key process parameters for steel rolling

[0038] See Table 3. The comparative example is the brake drum process for heavy-duty vehicle axles in traditional steel enterprises. After heating, the intermediate billet thickness is 48mm, which increases the rough rolling reduction to a certain extent. The final rolling temperature of roughing is 1080℃, and the final rolling temperature of finishing is 865℃. Front-end cooling is adopted, and the cooling rate is 16.4℃ / s. The relatively low cooling rate can also effectively suppress the growth of austenite grains, but small-sized non-metallic inclusions are difficult to precipitate in nanoscale form, which makes it difficult to improve the elongation.

[0039] Examples 1-4 describe the process for high-performance brake drum steel for heavy-duty vehicle axles. The process involves heating, a 53mm thick intermediate billet, and increased roughing reduction. The final roughing temperature is 1010℃-1030℃, and the final finishing temperature is 820℃-840℃, rolling within the austenite region. This fully utilizes the high plasticity of austenite, while dynamic recrystallization refines the austenite grains. Rapid cooling in the front section of the dense laminar flow cooling process inhibits austenite grain growth. A cooling rate of 25℃ / s-35℃ / s rapidly cools the high-temperature austenite to the coiling temperature range of 570℃-600℃, suppressing pearlite transformation and promoting the precipitation of small-sized non-metallic inclusions in a nanoscale morphology, significantly improving elongation.

[0040] Table 4 shows the test results of the comparative example and Examples 1-4 of the present invention.

[0041] Step 5: After sampling and testing, heavy-duty vehicle axle brake drum steel with a grain size ≥ 9.0, ferrite + a small amount of pearlite structure, yield strength 300MPa~320MPa, tensile strength 400MPa~420MPa, and elongation 55%~60% is obtained.

[0042] See Table 4. The comparison example is the brake drum process for heavy-duty axles in traditional steel enterprises. The cleanliness is relatively high, and the non-metallic inclusions are due to the high melting point of the slag (1528℃) and the lack of extreme desulfurization. The cooling rate is 16.4℃ / s, which is relatively low, and the grain size is only grade 8.0. The yield strength is 352MPa and the tensile strength is 448MPa, which are both relatively high, resulting in an elongation of 42%, which can meet the requirements of the brake drum process for heavy-duty axles in traditional steel enterprises.

[0043] Examples 1-4 describe the process for high-performance brake drum steel for heavy-duty vehicle axles. The final LF value S ≤ 0.003%, achieving an ultimate desulfurization effect. In addition, the slag melting point is 1455℃~1465℃, and the liquid slag can better adsorb non-metallic inclusions, resulting in ultra-high purity molten steel. The high-temperature austenite is rapidly cooled to the coiling temperature range of 570℃~600℃ at a cooling rate of 25℃ / s~35℃ / s, which inhibits the pearlite transformation and promotes the precipitation of small-sized non-metallic inclusions in nanoscale form, greatly improving the elongation and fully meeting the process requirements for brake drum steel for heavy-duty vehicle axles.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A method for manufacturing steel for brake drums of heavy-duty vehicle axles, characterized in that, In order, they include: Converter smelting, LF refining, slab continuous casting, rolling and sampling inspection; The chemical composition of the steel prepared by the method, by mass percentage, includes: C: 0.04%–0.06%, Si ≤ 0.05%, Mn: 0.30%–0.70%, P ≤ 0.015%, S ≤ 0.005%, Al: 0.02%–0.05%, Ti: 0.010%–0.050%, O ≤ 0.002%, with the balance being Fe and unavoidable impurities; In the rolling step, the finishing rolling temperature is controlled at 820℃~840℃, and then the high-temperature austenite is rapidly cooled to the coiling temperature range of 570℃~600℃ at a cooling rate of 25℃ / s~35℃ / s.

2. The method for manufacturing steel for brake drums of heavy-duty vehicle axles according to claim 1, characterized in that, The converter smelting includes converter turning C: 0.03%~0.04%, strengthening the stirring of the molten pool through top and bottom re-blowing, carbon-oxygen product ≤0.0025%; slag washing, adding in sequence: lime 2.5kg / t~2.8kg / t, aluminum blocks 1.4kg / t~1.6kg / t, calcium carbide 0.25kg / t~0.35kg / t, silicon carbide 0.15kg / t~0.25kg / t, deep deoxidation to ensure argon station [O]: 0.0005%~0.0020%, early slag formation, converter slag melting point ≤1540℃.

3. The method for manufacturing steel for brake drums of heavy-duty vehicle axles according to claim 1, characterized in that, The LF refining process includes: using calcium carbide and silicon carbide for composite diffusion deoxidation and extreme desulfurization, with the refining slag having a melting point ≤1500℃, and subjecting residual non-metallic inclusions to calcium treatment to denature them, generating nanoscale non-metallic inclusions that are diffusely distributed.

4. The method for manufacturing steel for brake drums of heavy-duty vehicle axles according to claim 3, characterized in that, The LF refining process includes: from molten steel to LF, 6.5 kg / t to 7.5 kg / t of lime and 0.5 kg / t to 1.5 kg / t of fluorite in converter + LF, 0.55 kg / t to 0.65 kg / t of calcium carbide in converter + LF, and 0.25 kg / t to 0.35 kg / t of silicon carbide in converter + LF. Calcium carbide and silicon carbide are used for composite diffusion deoxidation and extreme desulfurization, with S ≤ 0.003% and [O] ≤ 0.0010%. The melting point of the refining slag is ≤ 1500℃. The low-melting-point slag adsorbs large-sized non-metallic inclusions. Pure calcium wire at a speed of 3.0 m / s to 4.0 m / s modifies the residual MnS and Al2O3, generating nanoscale non-metallic inclusions that are diffusely distributed.

5. The method for manufacturing steel for brake drums of heavy-duty vehicle axles according to claim 1, characterized in that, The slab continuous casting is carried out under low superheat conditions. By optimizing the electromagnetic stirring of the crystallizer, dynamic light pressure and the cooling capacity of the secondary cooling zone, the center segregation of the slab reaches the C0.5 level.

6. The method for manufacturing steel for brake drums of heavy-duty vehicle axles according to claim 5, characterized in that, The slab continuous casting includes: full-process protective casting of slabs, optimized crystallizer electromagnetic stirring 350A / 7Hz under the premise of superheat of 10℃~25℃, dynamic light pressure reduction of 4.0mm~4.5mm, and comprehensive process optimization of secondary cooling zone water volume of 0.8L / kg~1.0L / kg.

7. The method for manufacturing steel for brake drums of heavy-duty vehicle axles according to claim 1, characterized in that, The rolling process includes: heating, intermediate billet thickness of 53 mm, and increasing the roughing reduction.

8. The method for manufacturing steel for brake drums of heavy-duty vehicle axles according to claim 1, characterized in that, The sampling inspection includes: obtaining a grain size ≥ 9.0, a ferrite + pearlite structure, a yield strength of 300MPa~320MPa, a tensile strength of 400MPa~420MPa, and an elongation of 55%~60% after sampling inspection.

9. A type of steel for brake drums in heavy-duty vehicle axles, characterized in that, It is obtained by the manufacturing method of brake drum steel for heavy-duty vehicle axles according to any one of claims 1-8.

10. A brake drum for heavy-duty vehicle axles, characterized in that, It is made of the steel used for brake drums of heavy-duty vehicle axles as described in claim 9.

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