Manufacturing method of steel for base plate of new energy automobile battery bottom protection plate

Abstract

The invention relates to the technical field of cold-rolled automobile steel production, and particularly discloses a manufacturing method of steel for a base plate of a new energy automobile battery bottom guard plate, which comprises the procedures of steelmaking, hot rolling, pickling cold continuous rolling, continuous hot galvanizing and the like. By adopting LF and RH two-time refining and reasonable hot rolling temperature, annealing temperature and other key parameters, it is guaranteed that a product is uniform in structure, fine in grain, free of banded structures and large-size inclusion segregation, and good comprehensive forming performance is achieved; compared with the prior art, the method has the advantages that alloy is added less, the thin and wide ultra-high-strength steel strip added less alloy is prepared through process setting, meanwhile, good surface quality of the steel strip is guaranteed through reasonable galvanization and post-treatment processes, and the complex requirements of ultra-high strength, corrosion resistance and thin and wide specifications required by the base plate of the battery bottom guard plate of the new energy automobile are met.

Description

Technical Field

[0001] This invention relates to the field of cold-rolled automotive steel production technology, specifically to a method for manufacturing steel for the base plate of a new energy vehicle battery. Background Technology

[0002] With the increasing demand for lightweight vehicles from the government and the market, new energy vehicles are replacing gasoline vehicles as the mainstream. The core driving force behind this transformation is the "heart" that powers the vehicle – the battery pack. Battery pack safety is one of the core issues for electric vehicles, and a battery underbody protection plate can effectively resist intrusion into the bottom of the battery pack, providing crucial protection for its structural safety. More and more models are choosing a "sandwich structure" battery underbody protection plate. This type of plate consists of upper and lower skins and a middle steel base layer, connected by an adhesive film or (and) hot melt adhesive layer. Compared to traditional pure plastic or steel underbody protection plates, it combines lightweight design with excellent impact resistance and corrosion resistance.

[0003] In this application environment, the steel base material for the battery underbody plate of new energy vehicles needs to meet the performance requirements of high strength, thin dimensions, high surface quality, and low surface tension. At the same time, as the size of battery packs increases, new requirements are also placed on the width specifications of the steel base. Conventional hot rolling and cold rolling annealing processes are very difficult to use for producing thin-gauge, wide-width ultra-high-strength steel.

[0004] Invention CN113430466A discloses an ultra-high strength steel for the lower base plate of a battery pack in new energy vehicles and its production method. The chemical composition of the steel plate, by weight percentage, is: C: 0.20-0.25%; Si: 0.20-0.40%; Mn: 1.20-1.70%; Cr: 0.10-0.20%; P: ≤0.020%; Al: ≤0.003%; S: ≤0.004%; with the balance being Fe and unavoidable impurities. The steel base is connected to the battery pack or vehicle chassis via mechanical fastening methods such as bolts and self-piercing riveting. The invented steel is not connected to the upper and lower skins via adhesive films or hot-melt adhesive layers, meaning it is not a galvanized sheet requiring high surface quality. This invention is constrained by the manufacturing process, preventing the production of lightweight thin plates less than 0.8mm thick, and also imposes significant limitations on the size of the battery pack protective plate.

[0005] Invention CN120311095A discloses a method for producing 980MPa grade galvanized duplex steel strip for automotive structures. The chemical composition of the steel strip, by weight percentage, is: C: 0.08-0.25%, Si: 0.15-0.45%, Mn: 2.0-2.9%, Al: 0.02-0.06%, Cr: 0.25-0.5%, Mo: 0.1-0.3%, P≤0.015%, S≤0.005%, with the balance being Fe and unavoidable impurities. Mo alloys are expensive; based on 2025 ferromolybdenum alloy prices, with a Mo content of 0.1-0.3%, the cost of ferromolybdenum alloy per ton of steel would be as high as 350-1050 yuan, making industrial-scale production and promotion difficult. The impact of hot-rolled coil surface quality on the finished galvanized coil was not considered. The setting of key process parameters such as the coiling temperature of 580-620℃ in the hot rolling process resulted in the formation of a large amount of quadrature iron oxide scale, which is difficult to remove with acid pickling and has a significant negative impact on the galvanized surface. Therefore, exploring a manufacturing method for steel used in the base plate of new energy vehicle batteries that requires less alloy addition, has low cost, and is lightweight, has become a technical problem urgently needing to be solved by those skilled in the art. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a method for manufacturing steel for the base plate of the bottom guard plate of new energy vehicle batteries.

[0007] The technical solution adopted by this invention to solve its technical problem is: a method for manufacturing steel for the base plate of a new energy vehicle battery bottom guard plate, comprising the following steps:

[0008] S1. The chemical composition of the steel plate by weight percentage is as follows: C: 0.16%-0.24%, Si: 0.20%-0.40%, Mn: 2.20%-2.60%, Cr: 0.2%-0.5%, Ti: 0.02%~0.04%, P≤0.020%, S≤0.007%, Al: 0.03%-0.05%, N≤0.0030%, with the remaining elements being Fe and unavoidable impurities;

[0009] S2. Steelmaking process: LF refining + RH refining is adopted;

[0010] S3. Hot rolling process: control the heating time, temperature and coiling temperature of the billet, and keep it warm in the slow cooling pit of the hot rolling warehouse after coiling.

[0011] S4. Pickling and cold rolling process: During production on a multi-stand cold rolling mill, the total cold rolling reduction rate is 35-55%.

[0012] S5. Hot-dip galvanizing process: control the continuous annealing temperature and cooling parameters, perform pre-oxidation and reduction control before entering the zinc pot to ensure good galvanization properties, and finally perform post-treatment.

[0013] Specifically, in step S1, the steel plate has a yield strength of 570-650 MPa, a tensile strength of 980-1050 MPa, an elongation after fracture (A80) of 10-18%, and a microstructure by volume percentage of ferrite 22-35%, martensite 43-52%, and bainite 18-30%.

[0014] Specifically, in step S1, the steel plate is a hot-dip galvanized steel plate with a thickness of 0.65-1.5mm and a width of 1000mm-1650mm, with no uncoated areas, no pits, no zinc ripples, good surface quality, and a surface tension ≥40mN / m after post-treatment.

[0015] Specifically, in step S1, after the steel plate is made into the battery bottom protective plate substrate, it is connected to the upper and lower skins of the battery bottom protective plate substrate through an adhesive film and / or a hot melt adhesive layer. The upper and lower skins are fiber-reinforced composite materials.

[0016] Specifically, after LF refining and RH refining in step S2, the crystallizer taper is 0.95-1.25%; the continuous casting billet pulling speed is 0.85±0.1m / min.

[0017] Specifically, in step S3, the total heating time of the billet is 220-260 min, the soaking time is 30-45 min, and the furnace exit temperature is 1220-1260℃; the hot rolling finishing temperature is 920±20℃; the coiling temperature is 500-560℃; U-shaped coiling is adopted, with the hot head: the temperature of the first 80m of the steel coil is 60℃ higher than that of the middle of the steel coil, and the hot tail: the temperature of the last 40m of the steel coil is 30℃ higher than that of the middle of the steel coil; after hot rolling, it is kept warm in the slow cooling pit of the hot rolling warehouse for a period of not less than 48 hours.

[0018] Specifically, the continuous annealing temperature in step S5 is 830-850℃; cooling parameters: slow cooling end temperature is 700-720℃, rapid cooling end temperature is 440-460℃, furnace exit temperature is 445-465℃, post-plating cooling rate is ≥20℃ / s, and belt speed is 100-140m / min.

[0019] Specifically, in step S5, the pre-oxidation-reduction stage controls the temperature of the pre-oxidation chamber to 700-750℃, the oxygen content in the pre-oxidation chamber to be in the range of 2.0-2.5%, the finishing elongation rate is set to 0.5-1.2%, the post-treatment method is passivation without oiling, and the passivation drying oven temperature is 210-270℃.

[0020] The present invention has the following beneficial effects:

[0021] This invention discloses a manufacturing method for steel used in the base plate of new energy vehicle battery underbody panels. By employing key parameters such as LF+RH double refining, a continuous casting billet pulling speed of 0.85±0.1m / min, and appropriate hot rolling and annealing temperatures, the method ensures a uniform microstructure, fine grains, and the absence of banded structures and large inclusions / segregations, resulting in excellent overall forming performance. With minimal alloy additions, and to meet the ultra-high strength requirements of the new energy vehicle battery underbody panel base plate, the method sets high hot rolling furnace exit temperature, appropriate coiling temperature, low total reduction in pickling rolling, and high annealing homogenization temperature. Through this process setting, ultra-high strength steel strip with minimal alloy additions is produced. Simultaneously, appropriate galvanizing and post-treatment processes ensure good surface quality of the steel strip. This method also provides a solution for producing ultra-high strength steel strips with extremely thin and wide specifications even on a multi-stand cold continuous rolling mill for pickling, thus meeting the complex requirements of ultra-high strength, corrosion resistance, and thin and wide specifications for the new energy vehicle battery underbody panel base plate. Attached Figure Description

[0022] Figure 1 This is a metallographic diagram of the hot-dip galvanized steel sheet produced by this invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] A method for manufacturing a steel substrate for a new energy vehicle battery bottom protection plate, wherein the chemical composition of the steel plate by weight percentage is: C: 0.16%-0.24%, Si: 0.20%-0.40%, Mn: 2.20%-2.60%, Cr: 0.2%-0.5%, Ti: 0.02%~0.04%, P≤0.020%, S≤0.007%, Al: 0.03%-0.05%, N≤0.0030%, and the remaining elements are Fe and unavoidable impurities.

[0025] The basic principles of the alloy element content design in this invention are as follows:

[0026] C: C plays a phase transformation strengthening role in duplex steel. By improving the stability of austenite, more martensite is formed after cooling, which directly improves the tensile strength. Considering the weldability, the strip steel requires a low carbon content. Therefore, the present invention controls the C content in the range of 0.16%-0.24%.

[0027] Si: Si is a ferrite-forming element. During heat treatment and slow cooling in the two-phase region, it has a significant purifying effect on ferrite, ensuring good drawing properties of the strip steel. Si promotes the diffusion of carbon and manganese into austenite, thereby improving the stability of austenite, and also enhances strength through solid solution strengthening. However, considering that too high a Si content will affect the surface quality of galvanized steel sheets, this invention controls the Si content within the range of 0.20%-0.40%.

[0028] Mn: Mn is a commonly used solid solution strengthening element that helps expand the austenite region and delays the transformation of pearlite and bainite during the cooling process of austenite, thereby improving the hardenability of steel. To ensure high strength, the Mn content in this invention is controlled within the range of 2.20%-2.60%.

[0029] Cr: The main role of Cr in duplex steel is to improve hardenability. The addition of Cr allows austenite to exist more stably under the same cooling conditions, resulting in a higher proportion of martensite, which is particularly important for producing high-strength steel strips on production lines with limited cooling capacity. However, excessive Cr content will deteriorate weldability. Therefore, this invention controls the Cr content within the range of 0.2%-0.5%.

[0030] Ti: In steel, it mainly forms fine TiC or TiN particles, which can refine the grains and strengthen the steel through precipitation. Excessive Ti content can lead to the formation of coarse carbides, potentially impairing plasticity and deteriorating the surface of galvanized duplex steel. Therefore, this invention controls the Ti content within the range of 0.02%-0.04%.

[0031] P, S, and N are impurity elements in steel, which worsen its plasticity and toughness. Generally, they need to be controlled at low levels. Considering the actual performance requirements of the product, this invention controls P ≤ 0.020%, S ≤ 0.007%, and N ≤ 0.0030%.

[0032] Al: Aluminum is one of the most important and commonly used strong deoxidizers in steelmaking. It can reduce oxygen content and improve the purity of molten steel. The main role of aluminum in steel is to refine grains and fix nitrogen in the steel, thereby improving the impact toughness of steel and reducing the tendency for cold brittleness and aging. When Al is too high, it can easily cause nozzle blockage and slab cracking during steelmaking. Therefore, this invention controls Al at 0.03%-0.05%.

[0033] The specific process steps and their impact on the product are as follows:

[0034] In the steelmaking process, LF refining + RH refining is adopted to ensure that impurity elements such as P, S, and N are controlled at low levels, and to ensure uniform control of alloy composition and molten steel temperature. Given the high content of elements such as Mn, Cr, and Si, to ensure billet quality and reduce inclusions and billet segregation, the crystallizer taper is controlled at 0.95-1.25%, and the continuous casting billet pulling speed is 0.85±0.1 m / min.

[0035] In the hot rolling process, the total heating time for the cast billet is 220-260 minutes, the soaking time is 30-45 minutes, and the furnace exit temperature is 1220-1260℃. Considering the high alloy element content of the steel used in the base plate of the new energy vehicle battery in this invention, a longer heating time and soaking time are set to ensure uniform heating of the cast billet and avoid edge cracking of the billet due to rapid heating. At the same time, a higher furnace exit temperature is controlled to further eliminate component segregation in the ingot or continuously cast billet, ensure uniform diffusion of Mn element, and avoid the formation of coarse banded structures during rolling. The hot rolling finish temperature is 920±20℃, and the coiling temperature is 500-560℃. Using a relatively high temperature of 920℃ for the final rolling combined with medium and low temperature coiling at 500-560℃, the strength of the hot-rolled coil is reasonably controlled, while avoiding the difficulty in removing the quaternary iron oxide scale generated after coiling, which would affect the surface quality of the galvanized product. U-shaped coiling is employed, with the temperature of the first 80m of the hot-rolled coil 60°C higher than that of the middle section, and the temperature of the last 40m of the hot-rolled coil 30°C higher than that of the middle section. After hot rolling, the coil is held in a slow cooling pit in the hot rolling silo for at least 48 hours. The use of a U-shaped coiling method with different lengths and temperatures at the beginning and end ensures uniform self-tempering of the entire coil during slow cooling after coiling, thereby guaranteeing uniform microstructure and properties and avoiding thickness fluctuations and poor strip shape in the pickled coil. The slow cooling holding period of at least 48 hours ensures a low cooling rate during the cooling process, controlling the strength of the hot-rolled strip within a reasonable range.

[0036] In the pickling and cold rolling process, the total cold rolling reduction rate is 35-55% when produced on a multi-stand cold rolling mill. A reasonable total reduction rate can refine the grains and provide recrystallization deformation energy. However, considering the high alloy element content of the steel used in the base plate of the new energy vehicle battery described in this invention, the low-temperature coiling in the hot rolling process, and the high strength of the hot-rolled coil, and also considering that the required specifications for the battery base plate base are mostly thin and wide, the load of the pickling and rolling mill must be controlled within a reasonable range to avoid exceeding the upper limit of the multi-stand continuous rolling mill. Therefore, the total cold rolling reduction rate is set at 35-55%.

[0037] The continuous hot-dip galvanizing process has the following parameters: continuous annealing soaking temperature: 830-850℃; slow cooling ending temperature: 700-720℃; rapid cooling ending temperature: 440-460℃; furnace exit temperature: 445-465℃; post-galvanizing cooling rate ≥20℃ / s; strip speed: 100-140m / min. Considering the relatively low total reduction rate of pickling and rolling, a higher annealing soaking temperature is set to increase the austenitization degree in the strip microstructure. Combined with a higher slow cooling ending temperature, this further improves austenite stability, providing a crucial guarantee for the strength of the galvanized product. The rapid cooling ending temperature and furnace exit temperature affect the content of newly formed ferrite and pre-galvanized bainite. The post-galvanizing cooling rate, i.e., the cooling speed of the strip after exiting the zinc bath, is controlled above 20℃ / s, mainly to control the martensite content in the finished product microstructure and ensure sufficient strength.

[0038] In the pre-oxidation and reduction stage, the pre-oxidation chamber temperature is 700-750℃, and the oxygen content within the chamber ranges from 2.0-2.5%. Setting reasonable pre-oxidation and reduction parameters avoids the formation of excessive silicon and manganese oxides on the substrate surface, which could affect wettability. This ensures the formation of a good inhibition layer on the substrate surface, meeting high surface quality requirements such as no missed plating, no pitting, and no zinc ripples. The finishing elongation is set at 0.5-1.2% to control the surface roughness of the hot-dip galvanized product and meet customer requirements. A large finishing elongation is not set to avoid affecting the drawing performance of the finished product. The post-treatment method is passivation without oiling. The passivation drying oven temperature is 210-270℃ to ensure high surface tension of the galvanized coil. The drying oven temperature range is set to avoid the temperature range where internal stress release occurs in the strip, preventing large waviness in the strip.

[0039] Examples 1-5: The present invention will be further described in detail below through specific examples 1-5:

[0040] The chemical composition of the continuous casting billet used in the base plate steel of the new energy vehicle battery in specific embodiments 1-5 is shown in Table 1:

[0041] Table 1 Chemical composition (wt%)

[0042] Example C Si S P Mn Al Cr Ti N 1 0.22 0.25 0.001 0.007 2.42 0.035 0.20 0.031 0.0022 2 0.21 0.27 0.001 0.008 2.35 0.035 0.21 0.033 0.0011 3 0.19 0.26 0.001 0.011 2.51 0.052 0.31 0.031 0.0012 4 0.22 0.32 0.001 0.010 2.52 0.051 0.27 0.027 0.0020 5 0.17 0.29 0.001 0.010 2.39 0.046 0.20 0.030 0.0014

[0043] In the steelmaking process, LF refining + RH refining is adopted; the crystallizer taper is 0.95-1.25%; the continuous casting billet pulling speed is 0.85±0.1m / min. The process parameters of the steelmaking process are shown in Table 2.

[0044] Table 2 Key process parameters for steelmaking

[0045] Example Refining process route crystallizer taper Continuous casting billet pulling speed 1 LF Refining + RH Refining 1.15 0.85 2 LF Refining + RH Refining 1.05 0.85 3 LF Refining + RH Refining 1.05 0.85 4 LF Refining + RH Refining 1.15 0.95 5 LF Refining + RH Refining 1.15 0.95

[0046] The total heating time for the cast billet is 220-260 min, with a soaking time of 30-45 min, and the furnace exit temperature is 1220-1260℃. The hot rolling finishing temperature is 920±20℃; the coiling temperature is 500-560℃; U-shaped coiling is used, with a hot head of 80m*60℃ and a hot tail of 40m*30℃. After hot rolling, the billet is held in a slow cooling pit in the hot rolling silo for at least 48 hours. Specific parameters for the hot rolling process are shown in Table 3.

[0047] Table 3 Hot rolling process parameters

[0048] Example Heating time / min Soaking time / min Furnace temperature / ℃ Hot rolling finishing temperature Winding temperature / ℃ Hot-rolled coil stacking slow cooling time / h 1 240 35 1230 920 550 48 2 247 33 1233 920 540 48 3 240 37 1231 915 535 48 4 253 35 1255 925 520 48 5 260 40 1257 915 540 48

[0049] During production on a pickling multi-stand cold rolling mill, the total cold rolling reduction rate is 35-55%. Hot-rolled coils are transformed into cold-hardened coils through the pickling and cold rolling process. Specific parameters for the pickling and cold rolling process are shown in Table 4.

[0050] Table 4 Process parameters for pickling and cold rolling processes

[0051] Example strip thickness / mm strip width / mm Total cold rolling reduction rate / % 1 1.0 1550 46 2 0.8 1600 50 3 1.0 1570 46 4 1.2 1620 42 5 1.2 1635 42

[0052] Continuous annealing soaking temperature: 830-850℃, slow cooling ending temperature: 700-720℃, rapid cooling ending temperature: 440-460℃, furnace exit temperature: 445-465℃, post-galvanizing cooling rate ≥20℃ / s, belt speed 100-140m / min. In the pre-oxidation and reduction stage, the pre-oxidation chamber temperature is 700-750℃, and the oxygen content in the pre-oxidation chamber ranges from 2.0-2.5%. The finishing elongation is set at 0.5-1.2%. The post-treatment method is passivation without oiling, with a passivation drying oven temperature of 210-270℃. The cold-rolled coil undergoes a continuous hot-dip galvanizing process to become the final product. Specific parameters for the continuous hot-dip galvanizing process are shown in Tables 5 and 6.

[0053] Table 5 Process parameters for continuous hot-dip galvanizing process

[0054] Example strip thickness / mm Annealing temperature / ℃ Slow cooling end temperature / ℃ Rapid cooling end temperature / ℃ Zinc pot temperature / ℃ Post-plating cooling rate (°C / s) Belt speed (m / min) Finishing elongation / % Passivation drying oven temperature / ℃ 1 1.0 840 710 450 455 25 130 1.0 220 2 0.8 835 700 455 455 20 140 1.0 230 3 1.0 840 710 450 460 25 130 1.0 220 4 1.2 850 715 452 457 25 120 0.8 210 5 1.2 850 715 448 462 25 120 0.6 210

[0055] Table 6 Pre-oxidation-reduction process parameters

[0056] Example Pre-oxidation chamber temperature / °C Oxygen content in oxidation room / % 1 720 2.1 2 710 2.1 3 710 2.0 4 715 2.0 5 715 2.3

[0057] like Figure 1 As shown, the microstructure of hot-dip galvanized steel sheet by volume percentage is: ferrite 22-35%, martensite 43-52%, and bainite 18-30%.

[0058] The hot-dip galvanized steel sheet has a yield strength of 570-650 MPa, a tensile strength of 980-1050 MPa, and an elongation after fracture (A80) of 10-18%. The mechanical properties of the hot-dip galvanized steel sheet in the examples are shown in Table 7.

[0059] Table 7 Mechanical Properties of Hot-Dip Galvanized Steel Sheets

[0060] Example Yield strength / MPa Tensile strength / MPa Elongation after fracture A80 / % 1 577 1010 16 2 589 1022 13 3 573 993 15 4 638 1025 15 5 579 986 18

[0061] This invention is not limited to the above-described embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.

[0062] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method of manufacturing a steel for a substrate for a battery underpan of a new energy vehicle, characterized by, The method comprises the following steps: S1, the chemical composition of the steel plate is as follows in percentage by weight: C: 0.16%-0.24%, Si: 0.20%-0.40%, Mn: 2.20%-2.60%, Cr: 0.2%-0.5%, Ti: 0.02%-0.04%, P≤0.020%, S≤0.007%, Al: 0.03%-0.05%, N≤0.0030%, and the rest is Fe and inevitable impurities; S2, the steelmaking process: LF refining+RH refining is adopted; S3, the hot rolling process: the heating time, temperature and coiling temperature of the cast blank are controlled, and the coiled steel plate is kept in the heat soaking pit of the hot rolling warehouse for heat preservation; S4, the pickling cold continuous rolling process: when the pickling multi-stand cold continuous rolling unit is used for production, the total cold rolling reduction rate is 35-55%; S5, the hot galvanizing process: the continuous annealing soaking temperature and the cooling parameters are controlled, the pre-oxidation reduction control is performed before entering the zinc pot to ensure good galvanizability, and finally the post-treatment is performed.

2. The method of manufacturing a steel for a new energy automobile battery underguard substrate according to claim 1, characterized by, The yield strength of the steel plate in the step S1 is 570-650 MPa, the tensile strength is 980-1050 MPa, the elongation after fracture A80 is 10-18%, and the microstructure is as follows in percentage by volume: ferrite 22-35%, martensite 43-52% and bainite 18-30%.

3. The method of manufacturing a steel for a new energy automobile battery bottom protection plate substrate according to claim 1, characterized in that, The steel plate in the step S1 is a hot galvanizing steel plate with a thickness of 0.65-1.5 mm and a width of 1000-1650 mm, which is free of plating leakage, free of pockmarks and free of zinc ripples, and has good surface quality, and the surface tension after post-treatment is greater than or equal to 40 mN / m.

4. The method of producing a steel sheet for a new energy automobile battery underpan substrate according to claim 1, characterized by, After the steel plate in the step S1 is made into a battery bottom guard plate substrate, the upper and lower skins of the battery bottom guard plate substrate are connected through a glue film and / or a hot melt adhesive layer, and the upper and lower skins are fiber-reinforced composite materials.

5. The method of manufacturing a steel for a new energy automobile battery underguard substrate according to claim 1, characterized by, After the LF refining+RH refining in the step S2, the taper of the crystallizer is 0.95-1.25%, and the continuous casting blank pulling speed is 0.85±0.1 m / min.

6. The method of manufacturing a new energy automobile battery bottom protection plate substrate steel according to claim 1, characterized in that, In the step S3, the total heating time of the cast blank is 220-260 min, the soaking time is 30-45 min, the discharge temperature is 1220-1260℃, the hot rolling finishing rolling temperature is 920±20℃, the coiling temperature is 500-560℃, the U-shaped coiling is adopted, the temperature of the steel coil head 80 m is 60℃ higher than the temperature of the middle part of the steel coil, the temperature of the steel coil tail 40 m is 30℃ higher than the temperature of the middle part of the steel coil, and the coiled steel plate is kept in the heat soaking pit of the hot rolling warehouse for heat preservation for not less than 48 h.

7. The method of manufacturing a new energy automobile battery bottom protection plate substrate steel according to claim 1, characterized in that, In the step S5, the continuous annealing soaking temperature is 830-850℃, the cooling parameters are as follows: the slow cooling end temperature is 700-720℃, the fast cooling end temperature is 440-460℃, the discharge temperature is 445-465℃, the plating after cooling speed is greater than or equal to 20℃ / s, and the strip speed is 100-140 m / min.

8. The method of manufacturing a new energy automobile battery bottom protection plate substrate steel according to claim 1, characterized in that, In the step S5, the pre-oxidation reduction stage controls the pre-oxidation chamber temperature to be 700-750℃, the oxygen content in the pre-oxidation chamber is in the range of 2.0-2.5%, the finish rolling elongation is set to be 0.5-1.2%, the post-treatment mode is passivation and no oil coating, and the passivation drying furnace temperature is 210-270℃.

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