A low-rebound, corrosion-resistant 550MPa grade cold-rolled high-strength steel and its manufacturing method

Abstract

This invention relates to a low-resilience, corrosion-resistant 550MPa grade cold-rolled high-strength steel and its manufacturing method. The chemical composition of the steel plate, by weight percentage, is: C: 0.05%–0.075%, Si: 0.25%–0.3%, Mn: 1.41%–1.65%, Cr: 0.053%–0.077%, P≤0.010%, S≤0.010%, Al: 0.6%–2.8%, Ce: 0.02%–0.05%, with the balance being Fe and unavoidable impurities. The chemical composition is designed based on C, Si, and Mn elements. The addition of certain amounts of Al and Cr improves the steel's strength and corrosion resistance. The addition of a certain amount of Ce purifies grain boundaries and desulfurizes the steel. During the annealing process, the microstructure is controlled to obtain a material with a low yield strength ratio.

Description

Technical Field

[0001] This invention relates to the field of high-strength steel technology, and in particular to a low-resilience, corrosion-resistant 550MPa grade cold-rolled high-strength steel suitable for manufacturing the main structures of bicycles and electric bicycles, such as wheels and frames, and its manufacturing method. Background Technology

[0002] Since the beginning of the 21st century, environmental issues have received increasing attention. Bicycles are the most environmentally friendly mode of transportation, and electric bicycles are becoming increasingly popular. Electric bicycles possess many advantages that other modes of transportation do not have, such as convenience, economy, and environmental friendliness. In some smaller third- and fourth-tier cities and vast rural areas, electric bicycles have become an important means of road transportation.

[0003] Currently, the number of electric bicycles in the Chinese market has reached a relatively high level, and existing bicycle and electric bicycle manufacturers have begun research on lightweighting. The weight of bicycles and electric bicycles mainly comes from the frame and wheels. Using high-strength steel can reduce the weight of the frame; however, due to factors such as industrial processing equipment, the strength of materials that can be processed by the deformation equipment used to manufacture bicycle and electric bicycle frames is limited. Moreover, the frame is mainly composed of tubular components of different shapes connected by welding, so there are high requirements for the resilience of the material after forming. If the tubular components have a large rebound after deformation, it will cause different parts of the frame to be unable to be connected.

[0004] Furthermore, while using high-strength steel allows for weight reduction by reducing thickness while maintaining strength, rusting is inevitable over time due to factors such as the peeling of anti-corrosion coatings. Thinner steel plates are also more prone to stress concentration than thicker ones, leading to decreased strength and increased susceptibility to cracks that compromise vehicle safety. Therefore, it is necessary to improve the corrosion resistance of steel to prevent cracking caused by rusting after material thinning. Summary of the Invention

[0005] This invention provides a low-resilience, corrosion-resistant 550MPa grade cold-rolled high-strength steel and its manufacturing method. The chemical composition is designed based on C, Si, and Mn elements. The strength of the steel is improved by adding a certain amount of Al and Cr, which also improves the corrosion resistance of the steel. A certain amount of Ce is added to purify the grain boundaries and desulfurize the steel. The material with a low yield strength ratio is obtained by controlling the microstructure during the annealing process.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A low-resilience, corrosion-resistant 550MPa grade cold-rolled high-strength steel, the chemical composition of the steel plate by weight percentage is: C: 0.05%–0.075%, Si: 0.25%–0.3%, Mn: 1.41%–1.65%, Cr: 0.053%–0.077%, P≤0.010%, S≤0.010%, Al: 0.6%–2.8%, Ce: 0.02%–0.05%, with the balance being Fe and unavoidable impurities.

[0008] Furthermore, the metallographic structure of the finished steel plate is ferrite + martensite + austenite, wherein the volume fraction of martensite is 6.8% to 8.3%, the volume fraction of austenite is 1.9% to 2.8%, and the remainder is ferrite; the ferrite structure includes α-ferrite and a small amount of δ-ferrite, and the grain size of the δ-ferrite structure is grade 8 or above.

[0009] Furthermore, the finished steel plate has a tensile strength ≥550MPa, an elongation greater than 23%, a yield strength ratio ≤0.46, a carbon equivalent ceq. <0.38%, a welding crack sensitivity index Pcm <0.199, and a springback angle θ after deformation of the pipe fittings less than 8°.

[0010] A method for manufacturing low-springback, corrosion-resistant 550MPa grade cold-rolled high-strength steel, the production process includes converter smelting, continuous casting, hot continuous rolling, pickling and cold rolling, and continuous annealing, with the following specific process controls:

[0011] 1) Converter smelting; smelting according to the set chemical composition to obtain molten steel that meets the composition requirements, with a tapping temperature of 1530℃~1580℃;

[0012] 2) Continuous casting; the steel pouring temperature is 1450~1502℃, and a light reduction is applied during continuous casting production, with a reduction of 3.4~5.5mm;

[0013] 3) Hot continuous rolling; the billet temperature is 500-800℃, the heating temperature is 1200-1260℃; at least 6 rolling passes are performed to obtain steel plates of the specified thickness; the initial rolling temperature is 1050-1150℃, the final rolling temperature is above 900℃; the coiling temperature is 510-550℃.

[0014] 4) Pickling and cold rolling: The steel coil is pickled and then cold rolled; during cold rolling, a single-stand rolling mill is used for 3 to 6 passes, and the total rolling reduction is more than 60% to obtain cold-rolled coil.

[0015] 5) Continuous annealing; The process route for continuous annealing is as follows: heating rate is 10℃ / s, annealing temperature is 775℃~810℃, annealing time is 80~114s; after annealing, it is first slowly cooled to 650℃~695℃, then rapidly cooled to 240℃~290℃, with a cooling rate greater than 45℃ / s during rapid cooling; aging temperature is 240℃~290℃, aging time is 220~390s, and finally cooled to room temperature.

[0016] Furthermore, in step 3), the thickness of the hot-rolled coil is 3.0 to 3.5 mm.

[0017] Furthermore, in step 4), the thickness of the cold-rolled coil is 1.0 to 1.4 mm.

[0018] Furthermore, in step 5), the atmosphere inside the furnace during the entire annealing process is a nitrogen-hydrogen mixture.

[0019] Furthermore, in step 5), the belt speed v of the steel plate during continuous annealing is: 120m / min ≥ v ≥ 90m / min.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1) The steel of this invention contains a certain amount of the rare earth element Ce. Ce not only purifies grain boundaries but also promotes the uniformity of martensite transformation, reduces concentrated stress, decreases the hardness difference between phases in the steel, and improves the material's plasticity. Ce also refines the δ-ferrite grains. Since the addition of Al results in coarse δ-ferrite grains, Ce refines the banded δ-ferrite structure. The addition of Ce reduces the interfacial tension of the molten steel, decreases the contact angle, and reduces the nucleation work, promoting the formation of numerous nuclei and inhibiting columnar crystal growth to a certain extent. It also refines the banded structure of high-temperature ferrite-δ-ferrite, resulting in over 75% equiaxed grains in the billet structure. By refining the δ-ferrite structure in the billet, the δ-ferrite grains in the subsequently produced steel are rated ≥8.

[0022] 2) This invention improves the corrosion resistance of steel by reducing the C and Mn content and increasing the Al content, while ensuring the strength of the steel. The corrosion resistance of the steel is evaluated by corrosion potential and corrosion current.

[0023] 3) The weldability of the steel is guaranteed through reasonable composition design. The carbon equivalent Ceq. of the steel is <0.38%, and the carbon equivalent is calculated as Ceq. = C + Mn / 6 + Si / 24 + Cr / 5 (%). The weld crack sensitivity index Pcm is <0.199, and the Pcm is calculated as Pcm = C + Si / 30 + (Mn + Cr) / 20 (%), which meets the performance requirements for welding bicycle steel bend tubes.

[0024] 4) This invention adopts a production process of converter smelting-continuous casting-hot continuous rolling-pickling rolling-continuous annealing. By adjusting the microstructure of the steel through the process, the microstructure of the finished steel is ferrite + martensite + austenite, wherein the grain size of ferrite is grade 8 or above, the volume percentage of martensite is 6.8% to 8.3%, and the volume percentage of austenite is 1.9% to 2.8%. The steel has a low yield strength ratio, which meets the requirement of low springback after the material is welded into tubes when manufacturing the main structure of bicycles. The springback angle is less than 8° as measured by the springback measurement method when bending the tube.

[0025] 5) The steel produced by this invention can be industrialized on existing production lines and has the advantage of stable production process. Attached Figure Description

[0026] Figure 1 This is a typical engineering stress-strain curve of the steel plate obtained in Embodiment 1 of the present invention.

[0027] Figure 2 This is a diagram of the billet structure in Embodiment 10 of the present invention. Detailed Implementation

[0028] The present invention discloses a low-resilience, corrosion-resistant 550MPa grade cold-rolled high-strength steel. The chemical composition of the steel plate, by weight percentage, is: C: 0.05%–0.075%, Si: 0.25%–0.3%, Mn: 1.41%–1.65%, Cr: 0.053%–0.077%, P≤0.010%, S≤0.010%, Al: 0.6%–2.8%, Ce: 0.02%–0.05%, with the balance being Fe and unavoidable impurities.

[0029] Furthermore, the metallographic structure of the finished steel plate is ferrite + martensite + austenite, wherein the volume fraction of martensite is 6.8% to 8.3%, the volume fraction of austenite is 1.9% to 2.8%, and the remainder is ferrite; the ferrite structure includes α-ferrite and a small amount of δ-ferrite, and the grain size of the δ-ferrite structure is grade 8 or above.

[0030] Furthermore, the finished steel plate has a tensile strength ≥550MPa, an elongation greater than 23%, a yield strength ratio ≤0.46, a carbon equivalent ceq. <0.38%, a welding crack sensitivity index Pcm <0.199, and a springback angle θ after deformation of the pipe fittings less than 8°.

[0031] The present invention discloses a method for manufacturing a low-springback, corrosion-resistant 550MPa grade cold-rolled high-strength steel. The production process includes converter smelting, continuous casting, hot continuous rolling, pickling and cold rolling, and continuous annealing. The specific process control is as follows:

[0032] 1) Converter smelting; smelting according to the set chemical composition to obtain molten steel that meets the composition requirements, with a tapping temperature of 1530℃~1580℃;

[0033] 2) Continuous casting; the steel pouring temperature is 1450~1502℃, and a light reduction is applied during continuous casting production, with a reduction of 3.4~5.5mm;

[0034] 3) Hot continuous rolling; the billet temperature is 500-800℃, the heating temperature is 1200-1260℃; at least 6 rolling passes are performed to obtain steel plates of the specified thickness; the initial rolling temperature is 1050-1150℃, the final rolling temperature is above 900℃; the coiling temperature is 510-550℃.

[0035] 4) Pickling and cold rolling: The steel coil is pickled and then cold rolled; during cold rolling, a single-stand rolling mill is used for 3 to 6 passes, and the total rolling reduction is more than 60% to obtain cold-rolled coil.

[0036] 5) Continuous annealing; The process route for continuous annealing is as follows: heating rate is 10℃ / s, annealing temperature is 775℃~810℃, annealing time is 80~114s; after annealing, it is first slowly cooled to 650℃~695℃, then rapidly cooled to 240℃~290℃, with a cooling rate greater than 45℃ / s during rapid cooling; aging temperature is 240℃~290℃, aging time is 220~390s, and finally cooled to room temperature.

[0037] Furthermore, in step 3), the thickness of the hot-rolled coil is 3.0 to 3.5 mm.

[0038] Furthermore, in step 4), the thickness of the cold-rolled coil is 1.0 to 1.4 mm.

[0039] Furthermore, in step 5), the atmosphere inside the furnace during the entire annealing process is a nitrogen-hydrogen mixture.

[0040] Furthermore, in step 5), the belt speed v of the steel plate during continuous annealing is: 120m / min ≥ v ≥ 90m / min.

[0041] The alloy design rationale for the low-springback, corrosion-resistant 550MPa grade cold-rolled high-strength steel described in this invention is as follows:

[0042] C: Carbon (C) has excellent solid solution strengthening effects. Too low a C content will reduce the strength of the steel and the stability of austenite; too high a C content will easily lead to the precipitation of coarse carbides at grain boundaries, reducing the steel's properties. Therefore, this invention controls the C content to be between 0.05% and 0.075%.

[0043] Mn: Mn is an element that strengthens steel through solid solution and expands the austenite region. Too low a Mn content leads to insufficient residual austenite after martensitic transformation, reducing the steel's plasticity. Too high a Mn content increases alloy costs and causes poor performance due to segregation. Therefore, this invention controls the Mn content to be between 1.41% and 1.65%.

[0044] Cr: Cr element can improve the hardenability of steel. After rapid cooling, martensite structure appears uniformly in the steel, increasing the uniformity of the structure. Therefore, the Cr element content is controlled at 0.053% to 0.077% in this invention.

[0045] Si: Si mainly functions as a deoxidizer in steel, reducing inclusions. Too low a Si content will not achieve this deoxidizing effect; too high a Si content will reduce the surface quality of the steel plate. Therefore, this invention controls the Si content to 0.25%–0.3%.

[0046] P: P is a harmful element in steel, and the lower its content, the better. Taking into account the production cost, this invention controls the P content to within 0.010%.

[0047] S: S is a harmful element in steel, and the lower its content, the better. Taking into account the production cost, this invention controls the S content to within 0.010%.

[0048] Al: Al helps deoxidize molten steel and inhibits the decomposition of residual austenite and the precipitation of carbides. Adding Al forms an oxide film on the surface of the steel plate, which helps improve the steel's corrosion resistance. However, excessive Al content not only increases production costs but also leads to difficulties in continuous casting. Therefore, this invention controls the Al content to be between 0.6% and 2.8%.

[0049] Ce (Ce): Possesses strong deoxidation and desulfurization capabilities, reacting with oxygen and sulfur to form spherical rare earth oxides, improving the toughness and plasticity of steel, reducing the segregation of impurity elements at grain boundaries, and improving the anisotropy of steel. Ce also promotes the uniformity of martensitic transformation, reduces concentrated stress, decreases the hardness difference between phases in steel, and enhances the material's plasticity. Ce also refines grains; since the addition of Al results in coarse δ-ferrite grains, Ce can refine the banded δ-ferrite structure, thereby improving the material's weldability. In this invention, the Ce content is controlled at 0.02%–0.05%.

[0050] The principle of the manufacturing method of low-springback corrosion-resistant 550MPa grade cold-rolled high-strength steel described in this invention is as follows:

[0051] The process flow includes the following steps: converter smelting → continuous casting → hot continuous rolling → pickling and cold rolling → continuous annealing. Specific control measures are as follows:

[0052] 1) Converter smelting: The chemical composition of the steel is as follows: C: 0.05%~0.075%, Si: 0.25%~0.3%, Mn: 1.4%~1.65%, Cr: 0.053%~0.077%, P: ≤0.010%, S: ≤0.010%, Al: 0.6~2.8%, Ce: 0.02~0.04%, with the balance being Fe. The steel is smelted in a converter to obtain molten steel that meets the composition requirements. The tapping temperature is between 1530℃ and 1580℃.

[0053] 2) Continuous casting: The casting temperature is between 1450 and 1502℃. During continuous casting production, a light reduction is required, with a reduction amount of 3.4 to 5.5 mm. Excessive reduction can easily cause a sharp increase in central cracks, while insufficient reduction has no effect on element segregation. Therefore, this invention controls the light reduction amount to 3.4 to 5.5 mm.

[0054] 3) Hot continuous rolling: The billet enters the furnace at a temperature between 500 and 800℃, and is heated at a temperature between 1200 and 1260℃. It is rolled in at least six passes through a rolling mill to obtain a steel plate of the specified thickness. The initial rolling temperature is between 1050 and 1150℃, and the final rolling temperature is above 900℃. Too low a final rolling temperature will cause hard phase structures to appear in the steel, leading to rolling difficulties. The coiling temperature is between 510 and 550℃; low-temperature coiling improves deformation energy storage. The thickness of the hot-rolled coil is between 3.0 and 3.5 mm.

[0055] 4) Pickling and cold rolling: The steel coil is first pickled and then cold rolled. It is rolled in 3 to 6 passes on a single stand mill with a total reduction rate of more than 60% to ensure sufficient cold deformation energy storage. The thickness of the cold rolled coil is between 1.0 and 1.4 mm.

[0056] 5) Continuous Annealing: The continuous annealing process route is as follows: heating rate is 10℃ / s, annealing temperature is 775℃~810℃, and annealing time is 80s~114s; after annealing, it is first slowly cooled to 650℃~695℃, then rapidly cooled to 240℃~290℃, with a cooling rate greater than 45℃ / s during rapid cooling. The aging temperature is 240℃~290℃, and the aging time is 220s~390s. Finally, it is cooled to room temperature.

[0057] (1) The atmosphere inside the furnace during the continuous annealing process is a mixture of nitrogen and hydrogen gas to ensure the surface quality of the steel plate.

[0058] (2) The speed v of the steel plate belt during continuous annealing must satisfy: 120m / min≥v≥90m / min.

[0059] The manufacturing method described in this invention can produce low-yield, corrosion-resistant 550MPa grade cold-rolled high-strength steel with tensile strength ≥550MPa, elongation greater than 23%, yield strength ratio ≤0.46, carbon equivalent ceq <0.38%, welding crack sensitivity index Pcm <0.199, and springback angle θ of the deformed pipe fitting less than 8°.

[0060] The present invention will be described in more detail below with reference to the embodiments. These embodiments are merely descriptions of the best mode of the present invention and do not limit the scope of the present invention in any way.

[0061]

Example

[0062] Table 1 lists the chemical composition of the steel plates in each embodiment; Table 2 lists the hot rolling process parameters of the steel plates in each embodiment; Table 3 lists the mechanical property parameters of the hot-rolled steel plates in each embodiment; Table 4 lists the cold rolling annealing process parameters of the steel plates in each embodiment; and Table 5 lists the mechanical property parameters of the steel plates in each embodiment after continuous annealing.

[0063] Table 6 shows the fitting results of the potential polarization curves measured when the experiments were conducted using the test solution (a mixed solution of 0.1 mol / L NaCl and 0.01 mol / L NaHSO3) in Examples 1-10. Figure 1 The figure shows a typical engineering stress-strain curve of the steel plate prepared in Example 1. Figure 2 This is a diagram of the billet structure in Example 10.

[0064] Table 1. Chemical composition of the steel plates in each embodiment, wt%.

[0065] Steel grade C Si Mn P S Al Ce Cr A1 0.068 0.3 1.63 0.0087 0.0041 0.62 0.025 0.077 A2 0.052 0.29 1.49 0.006 0.0038 1.73 0.0488 0.062 A3 0.074 0.26 1.5 0.005 0.0026 2.68 0.034 0.056 A4 0.0611 0.29 1.41 0.006 0.01 1.83 0.044 0.062 A5 0.05 0.28 1.53 0.003 0.008 1.62 0.049 0.071 A6 0.056 0.26 1.62 0.004 0.005 1.42 0.036 0.066 A7 0.073 0.25 1.65 0.008 0.009 1.55 0.038 0.053 A8 0.075 0.27 1.42 0.007 0.006 2.16 0.026 0.076 A9 0.058 0.29 1.55 0.004 0.004 2.62 0.033 0.062 A10 0.055 0.25 1.57 0.006 0.005 2.78 0.03 0.068

[0066] Table 2 Hot rolling process parameters of steel plates in each embodiment

[0067] Heating temperature, °C Rolling temperature, °C Final rolling temperature, °C Curling temperature, °C B1 1250 1105 915 543 B2 1210 1033 903 528 B3 1260 1136 929 549

[0068] Table 3 Mechanical property parameters of hot-rolled steel plates in various embodiments

[0069] Steel grade process number <![CDATA[Rp 0.2 / MPa]]> Rm / MPa A80 / ％ A1 B1 362 506 19.3 A2 B2 353 498 21.2 A3 B3 342 487 20.8

[0070] Table 4. Continuous annealing process parameters for steel plates in each embodiment.

[0071] Isotropic temperature (°C) Slow-cooling outlet temperature (°C) Rapid cooling outlet temperature (°C) Aging temperature (°C) C1 810 650 290 290 C2 800 695 240 240 C3 775 680 240 240 C4 809 670 260 260 C5 800 660 280 280 C6 780 655 270 270

[0072] Table 5 Mechanical property parameters of steel plates after continuous annealing in the examples.

[0073]

[0074] Table 6 shows the fitting results of the potential polarization curves of the steel plates obtained in Examples 1-10.

[0075] Example Steel grade process number process number <![CDATA[E corr / V]]> <![CDATA[I corr / (A / cm 2 )]]> 1 A1 B1 C1 -0.711 <![CDATA[2.28×10 -4 ]]> 2 A2 B2 C3 -0.709 <![CDATA[8.11×10 -5 ]]> 3 A3 B3 C2 -0.692 <![CDATA[4.48×10 -5 ]]> 4 A4 B1 C1 -0.700 <![CDATA[7.24×10 -5 ]]> 5 A5 B1 C1 -0.703 <![CDATA[8.94×10 -5 ]]> 6 A6 B1 C1 -0.708 <![CDATA[9.38×10 -5 ]]> 7 A7 B2 C1 -0.705 <![CDATA[8.36×10 -5 ]]> 8 A8 B3 C1 -0.696 <![CDATA[5.63×10 -5 ]]> 9 A9 B3 C1 -0.693 <![CDATA[5.22×10 -5 ]]> 10 A10 B3 C1 -0.682 <![CDATA[4.32×10 -5 ]]>

[0076] In the microstructure of cold-rolled high-strength steel billets, columnar crystals are predominantly present on both sides, while equiaxed crystals are present in the middle; however, as... Figure 2 As shown, the microstructure of the billet obtained in this embodiment 10 is almost entirely equiaxed crystals, and its grain structure has been refined compared with that of conventional billets.

[0077] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-resilience, corrosion-resistant 550MPa grade cold-rolled high-strength steel, characterized in that, The chemical composition of the steel plate, by weight percentage, is: C: 0.05%–0.075%, Si: 0.25%–0.3%, Mn: 1.41%–1.65%, Cr: 0.053%–0.077%, P≤0.010%, S≤0.010%, Al: 0.6%–2.8%, Ce: 0.02%–0.05%, with the balance being Fe and unavoidable impurities; The metallographic structure of the finished steel plate is ferrite + martensite + austenite, wherein the volume fraction of martensite is 6.8% to 8.3%, the volume fraction of austenite is 1.9% to 2.8%, and the remainder is ferrite. The ferrite structure includes α-ferrite and a small amount of δ-ferrite, and the grain size of the δ-ferrite structure is grade 8 or above.

2. The low-resilience, corrosion-resistant 550MPa grade cold-rolled high-strength steel according to claim 1, characterized in that, The finished steel plate has a tensile strength ≥ 550 MPa, an elongation greater than 23%, a yield strength ratio ≤ 0.46, a carbon equivalent ceq. < 0.38%, a weld crack sensitivity index Pcm < 0.199, and a springback angle θ after deformation of the pipe fittings less than 8°.

3. A method for manufacturing low-resilience, corrosion-resistant 550MPa grade cold-rolled high-strength steel as described in claim 1 or 2, characterized in that, The production process includes converter smelting, continuous casting, hot rolling, pickling and cold rolling, and continuous annealing. The specific control of each process is as follows: 1) Converter smelting; smelting according to the set chemical composition to obtain molten steel that meets the composition requirements, with a tapping temperature of 1530℃~1580℃; 2) Continuous casting; the steel pouring temperature is 1450~1502℃, and a light reduction is applied during continuous casting production, with a reduction of 3.4~5.5mm; 3) Hot continuous rolling; the billet temperature is 500-800℃, the heating temperature is 1200-1260℃; at least 6 rolling passes are performed to obtain steel plates of the specified thickness; the initial rolling temperature is 1050-1150℃, the final rolling temperature is above 900℃; the coiling temperature is 510-550℃. 4) Pickling and cold rolling: The steel coil is pickled and then cold rolled; during cold rolling, a single-stand rolling mill is used for 3 to 6 passes, and the total rolling reduction is more than 60% to obtain cold-rolled coil. 5) Continuous annealing; The process route for continuous annealing is as follows: heating rate is 10℃ / s, annealing temperature is 775℃~810℃, annealing time is 80~114s; after annealing, it is first slowly cooled to 650℃~695℃, then rapidly cooled to 240℃~290℃, with a cooling rate greater than 45℃ / s during rapid cooling; aging temperature is 240℃~290℃, aging time is 220~390s, and finally cooled to room temperature.

4. The method for manufacturing a low-springback, corrosion-resistant 550MPa grade cold-rolled high-strength steel according to claim 3, characterized in that, In step 3), the thickness of the hot-rolled coil is 3.0 to 3.5 mm.

5. The method for manufacturing a low-springback, corrosion-resistant 550MPa grade cold-rolled high-strength steel according to claim 3, characterized in that, In step 4), the thickness of the cold-rolled coil is 1.0 to 1.4 mm.

6. The method for manufacturing a low-springback, corrosion-resistant 550MPa grade cold-rolled high-strength steel according to claim 3, characterized in that, In step 5), the atmosphere inside the furnace during the entire annealing process is a nitrogen-hydrogen mixture.

7. The method for manufacturing a low-springback, corrosion-resistant 550MPa grade cold-rolled high-strength steel according to claim 3, characterized in that, In step 5), the belt speed v of the steel plate during continuous annealing is: 120m / min ≥ v ≥ 90m / min.

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