510MPa automobile beam steel mainly reinforced by Ti microalloy and production method of 510MPa automobile beam steel

Abstract

The invention discloses 510MPa automobile beam steel mainly reinforced by Ti microalloy and a production method of the 510MPa automobile beam steel, and belongs to the technical field of metallurgical plate production. The 510 MPa automobile beam steel mainly reinforced by the Ti microalloy, provided by the invention, comprises the following chemical components in percentage by mass: 0.06 to 0.08 percent of C, 0.05 to 0.10 percent of Si, 0.85 to 1.00 percent of Mn, less than or equal to 0.018 percent of P, less than or equal to 0.005 percent of S, 0.025 to 0.045 percent of Alt, 0.030 to 0.042 percent of Ti, 0.0008 to 0.0020 percent of Ca and the balance of Fe. The mechanical properties can meet the requirements that the yield strength is larger than or equal to 355 MPa, the tensile strength is 510-630 MPa, and the ductility is larger than or equal to 24%.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical plate production technology, specifically relating to a 510MPa automotive beam steel mainly reinforced with Ti microalloying and its production method. Background Technology

[0002] With the rapid development of the automotive industry and the continuous increase in production, the requirements for lightweight and safety performance in automobiles are becoming increasingly stringent. As the main load-bearing component of the vehicle body, the automotive frame is primarily used to manufacture longitudinal and transverse beams in commercial vehicles, requiring high strength, high toughness, and good formability. Traditional automotive frame steels are mostly strengthened using elements such as Mn and Nb, but this approach suffers from high cost and complex processes. Ti microalloying technology offers advantages such as low cost and significant strengthening effects; however, the strength and toughness of existing Ti microalloyed steels are difficult to achieve at the 510MPa level, and the production process is not yet mature. Therefore, developing a 510MPa automotive frame steel primarily strengthened with Ti microalloying and its production method is of great significance. Titanium microalloyed 510MPa frame steel, with its high strength, high toughness, good fatigue resistance, and cold formability, has broad application prospects in the automotive industry. Especially in the manufacture of load-bearing components for heavy vehicles such as trucks, this steel can significantly improve vehicle safety and service life.

[0003] In summary, titanium microalloyed 510MPa beam steel is a high-performance steel with broad application prospects in the automotive industry. By optimizing the composition design and manufacturing process, its performance can be further improved while reducing costs, thus meeting the automotive industry's demand for high-performance materials.

[0004] Patent publication number CN 119144894 A discloses a 510MPa grade green and clean surface steel plate for automobile beams and its manufacturing method. The chemical composition ratio is C: 0.06-0.08%, Si: 0.05-0.15%, Mn: 1.40-1.55%, Nb: 0.015-0.030%, Ti: 0.015-0.030%, Als: 0.015-0.045%, P≤0.020%, S≤0.010%. The composition design of the literature differs from that of this invention. First, the Mn content of this invention is 0.85-1.00%. A higher Mn content easily leads to segregation and the formation of banded structures, causing anisotropy in the mechanical properties of the material and a significant reduction in the reduction of area, which adversely affects the subsequent processing and use of the steel. In addition, a high Mn content will worsen the weldability of the steel. Second, this invention increases the strength by adding Nb, resulting in higher production costs.

[0005] Patent publication number CN 103451535 A discloses a 510MPa grade hot-rolled strip steel for automobile beams and its production process. The chemical composition ratio is C: 0.13-0.18%, Si: 0.30-0.50%, Mn: 0.75-1.15%, Ti: 0.008-0.025%, Alt: 0.02-0.06%, P≤0.025%, S≤0.008%, N≤0.006%. The composition design in that literature differs from that of this invention. That literature improves strength by increasing the C and Si content. Firstly, when the C content is within a certain range, a peritectic reaction occurs, causing uneven solidification of the initial billet shell, leading to cracks in the continuously cast billet. Secondly, excessively high carbon content forms coarse and brittle carbide particles, which is detrimental to plasticity and toughness. Excessive carbon content also creates a segregation zone in the center of the steel plate, negatively impacting bending performance and formability. Furthermore, excessively high carbon content increases the welding carbon equivalent and the welding crack sensitivity index, hindering welding processing. Excessively high Si content not only reduces weldability but also produces a large amount of red rust, resulting in poor surface quality. In contrast, the composition design of this invention uses low C and low Si, avoiding these issues.

[0006] Patent publication number CN 102002631 A discloses a micro-niobium 510MPa grade automotive frame plate and its manufacturing method. The main chemical composition ratio is C: 0.095-0.125%, Si: 0.15-0.30%, Mn: 0.09-1.20%, Nb: 0.007-0.012%, Als: 0.010-0.024%, P≤0.025%, S≤0.012%. The composition design of this document differs from that of this invention. The composition of this document increases the strength by adding the more expensive Nb element, which increases the manufacturing cost of the product. Summary of the Invention

[0007] To meet the market demand for lightweight steel for automotive beams, further expand market share, and enrich product variety, this invention, based on advanced equipment and process characteristics, employs a rational composition design and process technology to develop a 510MPa automotive beam steel primarily reinforced with Ti microalloying. This achieves high strength, high toughness, and good formability, meeting the requirements for automotive lightweighting. Production results and user feedback demonstrate that all properties of this product meet relevant technical requirements and user needs.

[0008] This invention is mainly achieved through the following technical solutions.

[0009] One aspect of this invention provides a 510MPa automotive beam steel primarily reinforced with Ti microalloying, the chemical composition of which, by mass percentage, is: C: 0.06–0.08%, Si: 0.05–0.10%, Mn: 0.85–1.00%, P≤0.018%, S≤0.005%, Alt: 0.025–0.045%, Ti: 0.030–0.042%, Ca: 0.0008–0.0020%, with the balance being Fe and unavoidable impurities;

[0010] The mechanical properties of the 510MPa automotive beam steel mainly reinforced with Ti microalloying meet the following requirements: yield strength ≥355MPa, tensile strength 510~630MPa, and elongation ≥24%.

[0011] In some embodiments, the mechanical properties of the 510MPa automotive beam steel mainly reinforced with Ti microalloying meet the following requirements: yield strength 467-502MPa, tensile strength 526-568MPa, and elongation 26-31%.

[0012] In some embodiments, the chemical composition of the 510MPa automotive beam steel, which is mainly reinforced with Ti microalloying, is as follows by mass percentage: C: 0.062-0.08%, Si: 0.05-0.10%, Mn: 0.88-1.00%, P≤0.018%, S≤0.004%, Alt: 0.025-0.045%, Ti: 0.030-0.042%, Ca: 0.0015-0.0020%, with the balance being Fe and unavoidable impurities.

[0013] Another aspect of the present invention provides a method for producing 510MPa automotive beam steel with Ti microalloying as the main reinforcement, which includes the following processes: smelting-continuous casting; slab heating; rolling; cooling; and coiling.

[0014] In some embodiments, the smelting-continuous casting process includes the following steps: KR desulfurization—converter—LF refining—slab continuous casting—slow cooling; wherein the composition of the molten steel supplied to the casting machine is controlled as follows: C: 0.06~0.08%, Si: 0.05~0.10%, Mn: 0.85~1.00%, P≤0.018%, S≤0.005%, Alt: 0.025~0.045%, Ti: 0.030~0.042%, Ca: 0.0008~0.0020%, with the balance being Fe and unavoidable impurities. Specifically, in the smelting-continuous casting process, the molten iron is desulfurized and pretreated, and then decarburized and dephosphorized in a top-and-bottom blown converter to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is ≥1640℃. Then, the molten steel after converter smelting is refined in an LF ladle, and the refining temperature is ≥1564℃.

[0015] In some embodiments, in the slab heating process, the slab, after surface cleaning, is fed into a heating furnace. The slab heating temperature, furnace time, homogenization temperature, homogenization time, and exit temperature are strictly controlled. The heating temperature is controlled at 1230±20℃, the furnace time at 160–270 min, the homogenization temperature at 1240±20℃, the homogenization time at 25–50 min, and the exit temperature at 1220±20℃. Specifically, in the slab heating process, the slab superheat during continuous casting is controlled to ≥25℃, followed by slab cleaning, slow cooling, and continuous casting slab quality inspection. The slab heating temperature is 1230±20℃, the homogenization temperature is controlled at 1240±20℃, and the exit temperature is controlled at 1220±20℃. The heated slab is then subjected to high-pressure water descaling.

[0016] In some embodiments, the rolling process includes a roughing stage and a finishing stage. The roughing stage is performed using a 3+3 mode two-stand mill, and the finishing stage is performed using a 7-stand continuously variable crown (CVC) mill. The finishing stage employs speed-increasing rolling. The entry thickness of the finishing mill is 40 mm, the initial rolling temperature of the finishing mill is not less than 1030°C, and the final rolling temperature of the finishing mill is 900±15°C.

[0017] In some embodiments, the cooling process employs laminar flow cooling equipment, with a pre-dispersion cooling mode, and utilizes a computer-based secondary system for self-learning calculations. Specifically, the laminar flow cooling employs pre-dispersion cooling, with the cooling rate controlled at 25-28°C / s.

[0018] In some embodiments, the winding temperature is 600±15°C.

[0019] The beneficial effects of this invention are as follows: By combining a reasonable chemical composition design with an optimal hot rolling process, a 510MPa automotive beam steel primarily reinforced with Ti microalloying is provided. Ti, as a strong carbide-forming element, has a strong affinity for O, N, and C, forming titanium carbide (TiC) or titanium carbonitride (TiCN). These compounds significantly improve the strength of the steel. Simultaneously, Ti can also form insoluble carbide particles with iron and carbon, which accumulate at the grain boundaries of the steel, preventing grain coarsening and further improving the toughness. This steel grade, through titanium microalloying treatment, not only significantly improves the comprehensive properties of the steel, such as strength and toughness, but also reduces production costs and increases production efficiency. The microstructure consists of ferrite and pearlite. Mechanical properties: yield strength 467–502 MPa, tensile strength 526–568 MPa, elongation 26–31%. The titanium microalloyed 510MPa beam steel exhibits high strength, high toughness, good fatigue resistance, and cold formability. These performance characteristics have led to their widespread application in the automotive industry, particularly in the manufacture of load-bearing components such as truck crossbeams and longitudinal beams, meeting the industry's requirements for material strength. Furthermore, the increased strength of the steel strip in the automotive beams of this invention allows for a further reduction in thickness, making it a lightweight material that can replace lower-strength steel. In addition, the product's manufacturing method is simple and easy to implement, suitable for industrial mass production, and all performance characteristics meet relevant standards and user needs. Attached Figure Description

[0020] Figure 1 This is a micrograph of the 510MPa automotive beam steel mainly reinforced with Ti microalloying obtained in Example 1 of the present invention. Detailed Implementation

[0021] The present invention will be described in detail below through specific embodiments. These embodiments are intended to help understand the present invention and are not intended to limit the scope of the present invention.

[0022] Example 1

[0023] Molten iron undergoes desulfurization pretreatment, followed by decarburization and dephosphorization in a top-and-bottom blown converter to obtain steel. Argon blowing is performed throughout the converter smelting process, with scrap steel added. The converter tapping temperature is 1645℃. The molten steel is then subjected to LF ladle refining at a refining temperature ≥1564℃. Temperature measurement and composition fine-tuning are performed during LF ladle refining. The chemical composition supplied to the casting machine after LF ladle refining is shown in Table 1. The slab superheat is 28℃ during continuous casting, followed by slab cleaning, slow cooling, and continuous casting slab quality inspection. The slab heating temperature is 1223℃ for 265 minutes, and the heated slab is then descaled using high-pressure water. Width is determined using a width-fixing press, followed by a 2-stand roughing mill and a 7-stand CVC finishing mill. The finishing mill starting temperature is 1036℃, the finishing mill ending temperature is 893℃, and the finished product thickness is 2.0mm. Laminar flow cooling employs pre-dispersion cooling at a rate of 28℃ / s, reducing the steel strip temperature to 600℃ before coiling. Finally, product performance is tested, as shown in Table 2 below. Figure 1 The image shows a microstructure of a 510MPa automotive beam steel mainly reinforced with Ti microalloying obtained in this embodiment. The microstructure consists of ferrite and pearlite.

[0024] Example 2

[0025] Molten iron undergoes desulfurization pretreatment, followed by decarburization and dephosphorization in a top-and-bottom blown converter to obtain steel. Argon blowing is performed throughout the converter smelting process, with scrap steel added. The converter tapping temperature is 1652℃. The molten steel is then subjected to LF ladle refining at a refining temperature ≥1566℃. Temperature measurement and composition fine-tuning are performed during LF ladle refining. The chemical composition supplied to the casting machine after LF ladle refining is shown in Table 1. The slab superheat is 26℃, followed by slab cleaning, slow cooling, and continuous casting slab quality inspection. The slab heating temperature is 1228℃ for 258 minutes, and the heated slab is then descaled using high-pressure water. Width is determined using a width-fixing press, followed by a 2-stand roughing mill and a 7-stand CVC finishing mill. The finishing mill starting temperature is 1033℃, the finishing mill ending temperature is 905℃, and the finished product thickness is 3.0mm. Laminar flow cooling adopts pre-dispersion cooling with a cooling rate of 26℃ / s. The steel strip temperature is reduced to 605℃ before winding. Finally, product performance is tested, as shown in Table 2 below.

[0026] Example 3

[0027] Molten iron undergoes desulfurization pretreatment, followed by decarburization and dephosphorization in a top-and-bottom blown converter to obtain steel. Argon blowing is performed throughout the converter smelting process, with scrap steel added. The converter tapping temperature is 1647℃. The molten steel is then subjected to LF ladle refining at a refining temperature ≥1562℃. Temperature measurement and composition fine-tuning are performed during LF ladle refining. The chemical composition supplied to the casting machine after LF ladle refining is shown in Table 1. The slab superheat is 32℃ during continuous casting, followed by slab cleaning, slow cooling, and continuous casting slab quality inspection. The slab heating temperature is 1220℃ for 264 minutes, and the heated slab is then descaled using high-pressure water. Width is determined using a width-fixing press, followed by a 2-stand roughing mill and a 7-stand CVC finishing mill. The finishing mill starting temperature is 1030℃, the finishing mill finishing temperature is 896℃, and the finished product thickness is 4.0mm. Laminar flow cooling adopts pre-dispersion cooling at a cooling rate of 25℃ / s. The steel strip temperature is reduced to 588℃ before winding. Finally, product performance is tested, as shown in Table 2 below.

[0028] Example 4

[0029] Molten iron undergoes desulfurization pretreatment, followed by decarburization and dephosphorization in a top-and-bottom blown converter to obtain steel. Argon blowing is performed throughout the converter smelting process, with scrap steel added. The converter tapping temperature is 1643℃. The molten steel is then subjected to LF ladle refining at a refining temperature ≥1566℃. Temperature measurement and composition fine-tuning are performed during LF ladle refining. The chemical composition supplied to the casting machine after LF ladle refining is shown in Table 1. The slab superheat is 27℃ during continuous casting, followed by slab cleaning, slow cooling, and continuous casting slab quality inspection. The slab heating temperature is 1225℃ for 256 minutes, and the heated slab is then descaled using high-pressure water. Width is determined using a width-fixing press, followed by a 2-stand roughing mill and a 7-stand CVC finishing mill. The finishing mill starting temperature is 1031℃, the finishing mill ending temperature is 900℃, and the finished product thickness is 6.0mm. Laminar flow cooling adopts pre-dispersion cooling with a cooling rate of 27℃ / s. The steel strip temperature is reduced to 590℃ before winding. Finally, product performance is tested, as shown in Table 2 below.

[0030] Example 5

[0031] Molten iron undergoes desulfurization pretreatment, followed by decarburization and dephosphorization in a top-and-bottom blown converter to obtain steel. Argon blowing is performed throughout the converter smelting process, with scrap steel added. The converter tapping temperature is 1653℃. The molten steel is then subjected to LF ladle refining at a refining temperature ≥1568℃. Temperature measurement and composition fine-tuning are performed during LF ladle refining. The chemical composition supplied to the casting machine after LF ladle refining is shown in Table 1. The slab superheat is 31℃, followed by slab cleaning, slow cooling, and continuous casting slab quality inspection. The slab heating temperature is 1228℃ for 257 minutes, and the heated slab is then descaled using high-pressure water. Width is determined using a width-fixing press, followed by a 2-stand roughing mill and a 7-stand CVC finishing mill. The finishing mill starting temperature is 1032℃, the finishing mill ending temperature is 902℃, and the finished product thickness is 5.0mm. Laminar flow cooling adopts pre-dispersion cooling at a cooling rate of 25℃ / s. The steel strip temperature is reduced to 597℃ before winding. Finally, product performance is tested, as shown in Table 2 below.

[0032] Comparative Example 1: The production method followed that shown in Example 1, except that the chemical composition of the LF ladle refining casting machine was different from that used in Example 1, as shown in Table 1 below. Finally, product performance was tested, as shown in Table 2 below.

[0033] Comparative Example 2: The production method followed that shown in Example 5, except that the chemical composition of the LF ladle refining feeder was different from that used in Example 5, as shown in Table 1 below. Finally, product performance was tested, as shown in Table 2 below.

[0034] Comparative Examples 3-4: The production method of Comparative Examples 3-4 is the same as that shown in Example 1, except that the winding temperature is different from that in Example 1. Specifically, the winding temperature of Comparative Example 3 is 540°C, and the winding temperature of Comparative Example 4 is 660°C. Finally, the product performance was tested, as shown in Table 2 below.

[0035] Table 1: Chemical composition (wt%) of Examples 1-5 and Comparative Examples 1-4 of the present invention

[0036] Example C Si Mn P S Alt Ti Ca 1 0.070 0.05 0.88 0.018 0.004 0.045 0.036 0.0015 2 0.075 0.08 0.92 0.016 0.003 0.040 0.040 0.0020 3 0.066 0.10 0.90 0.015 0.003 0.030 0.030 0.0018 4 0.062 0.06 0.93 0.017 0.002 0.035 0.033 0.0018 5 0.080 0.07 1.00 0.018 0.002 0.025 0.042 0.0016 Comparative Example 1 0.070 0.05 0.50 0.018 0.004 0.045 0.020 0.0015 Comparative Example 2 0.080 0.07 1.28 0.018 0.002 0.025 0.055 0.0016 Comparative Example 3 0.070 0.05 0.88 0.018 0.004 0.045 0.036 0.0015 Comparative Example 4 0.070 0.05 0.88 0.018 0.004 0.045 0.036 0.0015

[0037] The mechanical properties of the steel coils in Examples 1 to 5 of the present invention were tested, and the test results are shown in Table 2.

[0038] Table 2: Mechanical properties of steel coils from Examples 1-5 and Comparative Examples 1-4 of the present invention

[0039]

[0040] As shown in Tables 1 and 2 above, the mechanical properties of the Ti microalloyed reinforced 510MPa automotive beam steel provided by this invention meet the following requirements: yield strength ≥355MPa, tensile strength 510~630MPa, elongation ≥24%, preferably: yield strength 467~502MPa, tensile strength 526~568MPa, elongation 26~31%. The titanium microalloyed 510MPa beam steel possesses high strength, high toughness, good fatigue resistance, and cold formability. These properties have led to its widespread application in the automotive industry, particularly in the manufacture of load-bearing components such as truck crossbeams and longitudinal beams, meeting the industry's requirements for material strength. Furthermore, the production method of this invention is simple and easy to implement, suitable for industrial mass production, and perfectly meets the needs of automotive beam steel, with all properties meeting relevant standard requirements and user needs. According to the test results of Comparative Examples 1-2, when the chemical composition of the product does not meet the requirements of this invention, the mechanical properties of the product will be substandard. For example, in Comparative Example 1, when the Mn and Ti contents are lower than the standard requirements, the strength of the product is lower than the standard requirements and cannot meet the user's needs. In Comparative Example 2, when the Mn and Ti contents are higher than the standard requirements, the product has high strength but low elongation, and cracking occurs in the bending test, resulting in poor cold workability during later use. According to the results of Comparative Examples 3-4, when the chemical composition of the product meets the requirements of this invention, but the production process does not meet the requirements of this invention, such as when the winding temperature is higher or lower than the set value, the performance of the obtained product will also fail to meet the requirements. The low winding temperature in Comparative Example 3 and the high winding temperature in Comparative Example 4 both lead to a decrease in product strength, failing to meet the standard requirements and user needs.

[0041] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A 510MPa automotive beam steel primarily reinforced with Ti microalloying, wherein the chemical composition of the 510MPa automotive beam steel primarily reinforced with Ti microalloying, by mass percentage, is: C: 0.06-0.08%, Si: 0.05-0.10%, Mn: 0.85-1.00%, P≤0.018%, S≤0.005%, Alt: 0.025-0.045%, Ti: 0.030-0.042%, Ca: 0.0008-0.0020%, with the balance being Fe and unavoidable impurities; The mechanical properties of the 510MPa automotive beam steel mainly reinforced with Ti microalloying meet the following requirements: yield strength ≥355MPa, tensile strength 510~630MPa, and elongation ≥24%.

2. The 510MPa automotive beam steel with Ti microalloying as the main reinforcement as described in claim 1 has the following mechanical properties: yield strength 467-502MPa, tensile strength 526-568MPa, and elongation 26-31%.

3. The 510MPa automotive beam steel with Ti microalloying reinforcement as described in claim 1 or 2 has the following chemical composition by mass percentage: C: 0.062-0.08%, Si: 0.05-0.10%, Mn: 0.88-1.00%, P≤0.018%, S≤0.004%, Alt: 0.025-0.045%, Ti: 0.030-0.042%, Ca: 0.0015-0.0020%, with the balance being Fe and unavoidable impurities.

4. The production method of 510MPa automotive beam steel with Ti microalloying reinforcement as described in any one of claims 1-4, comprising the following processes: Smelting—continuous casting; slab heating; rolling; cooling; and take-up.

5. The production method according to claim 4, wherein the smelting-continuous casting process includes the following flow: KR desulfurization—converter—LF refining—slab continuous casting—slow cooling; wherein the composition of the molten steel supplied to the casting machine is controlled as follows: C: 0.06~0.08%, Si: 0.05~0.10%, Mn: 0.85~1.00%, P≤0.018%, S≤0.005%, Alt: 0.025~0.045%, Ti: 0.030~0.042%, Ca: 0.0008~0.0020%, with the balance being Fe and unavoidable impurities.

6. The production method according to claim 4, wherein in the slab heating process, the slab after surface cleaning is fed into the heating furnace, and the slab heating temperature, furnace time, homogenization temperature, homogenization time and furnace exit temperature are strictly controlled. The heating temperature is controlled at 1230±20℃, the furnace time is controlled at 160~270min, the homogenization temperature is controlled at 1240±20℃, the homogenization time is controlled at 25~50min, and the furnace exit temperature is controlled at 1220±20℃.

7. The production method according to claim 4, wherein the rolling process includes a roughing stage and a finishing stage, wherein the roughing stage is performed using a 3+3 mode two-stand rolling mill, and the finishing stage is performed using a 7-stand continuously variable crown (CVC) rolling mill, wherein the finishing stage employs speed-increasing rolling; the finishing mill entry thickness is 40 mm, the starting rolling temperature is not less than 1030 °C, and the finishing rolling temperature is 900 ± 15 °C.

8. The production method according to claim 4, wherein the cooling process employs laminar flow cooling equipment, the cooling mode is pre-dispersion, and the results are calculated using a computer-based two-level system through self-learning.

9. The production method according to claim 4, wherein the winding temperature is 600±15℃.

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