Metal plate, preparation method thereof and automobile part

Abstract

The invention relates to a metal plate, a preparation method thereof and an automobile part. The metal plate comprises at least one equal-thickness area and a thickness gradual change area, when the number of the equal-thickness areas is larger than or equal to 2, every two adjacent equal-thickness areas are connected through the thickness gradual change area, the thickness of the thickness gradual change area changes continuously, the metal plate is an integrally-formed plate, and the thickness of the whole metal plate does not change suddenly. The thickness of the metal plate is variable, and the purpose of weight reduction can be achieved, so that light weight of parts made of the metal plate is achieved, materials are saved, and material cost and resource consumption are reduced. Moreover, the metal plate is an integrally-formed plate, can be continuously produced, is high in efficiency and free of welding seams, avoids the problem of material breakage caused by welding problems, and improves the safety and reliability of automobile parts.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobile part manufacturing, in particular to a metal plate and a preparation method thereof, and an automobile part. BACKGROUND

[0002] In recent years, with the increasing demand for lightweight and safety in the field of automobile manufacturing, especially in new energy vehicles, the requirements for materials are becoming more and more important. At present, lightness and strength are the demand direction of materials for automobiles.

[0003] The parts made of metal materials for automobiles traditionally use materials with equal thickness. The materials with equal thickness cannot achieve the purpose of weight reduction according to the actual stress condition, and excessively thinning the material thickness cannot guarantee the safety of the parts. In order to solve the problems of lightweight and safety, some materials use the method of laser tailor welding, which is to weld materials with different thicknesses together to reduce weight under the premise of guaranteeing safety performance.

[0004] However, the metal plate and the preparation method thereof for automobile parts still need to be improved. SUMMARY

[0005] The present application is made based on the research and discovery of the inventors on the following problems: The inventors found that the laser tailor-welded plate has the following problems: the laser tailor-welding process is manually loaded and unloaded, which is low in efficiency and high in cost; the laser tailor-welded plate has a thickness mutation, which puts higher requirements on related molds and equipment during the production of parts; there is a weld on the laser tailor-welded plate, and the weld area has a lower ductility than the base material due to the formation of martensite and other organizations during rapid heating and cooling during welding, which is a brittle area; when there are defects such as weld perforation and distortion, the stress concentration effect will exacerbate the cracking risk.

[0006] Therefore, the present application provides a metal plate and a preparation method thereof, and an automobile part. The automobile part made of the metal plate takes into account the lightweight and safety, and can avoid the above-mentioned problems caused by laser tailor welding.

[0007] In a first aspect, the present application provides a metal plate. The metal plate comprises at least one equal-thickness region and a thickness-gradual-change region, when the number of equal-thickness regions is greater than or equal to 2, two adjacent equal-thickness regions are connected by the thickness-gradual-change region, the thickness of the thickness-gradual-change region changes continuously, and the metal plate is an integrally formed plate, and the thickness of the entire metal plate has no mutation. The thickness of the metal plate changes, which can achieve the purpose of weight reduction, thereby realizing the lightweight of the part made of the metal plate, saving the use of materials, and reducing the material cost and resource consumption. Moreover, the metal plate is an integrally formed plate, which can be produced continuously, is high in efficiency, has no weld, avoids the problem of material fracture caused by welding, and improves the safety and reliability of the automobile part.

[0008] Further, the thickness of the thickness gradient zone continuously increases or continuously decreases.

[0009] Further, the yield strength and tensile strength of the metal plate decrease with the increase of the thickness of the metal plate.

[0010] Further, the yield strength and tensile strength of the metal plate increase with the increase of the thickness of the metal plate.

[0011] Further, the yield strength and tensile strength of the metal plate change by a range of no more than 100 MPa with the thickness of the metal plate.

[0012] In a second aspect, the application provides a method for preparing a metal plate. The method comprises: rolling a metal plate blank to obtain a metal plate, the metal plate comprising at least one equal thickness zone and a thickness gradient zone, when the number of equal thickness zones is greater than or equal to 2, two adjacent equal thickness zones are connected by the thickness gradient zone, the thickness of the thickness gradient zone continuously changes, and the thickness of the entire metal plate has no sudden change. The metal plate prepared by the method is an integrally formed plate, which can be produced continuously, has high efficiency, and has no welds, thereby avoiding the problem of material rupture due to welding problems, improving the safety and reliability of automobile parts. Moreover, the thickness of the metal plate changes, which can achieve the purpose of weight reduction, thereby realizing the lightweight of the parts made of the metal plate, saving the use of materials, and reducing the material cost and resource consumption.

[0013] Further, the metal plate is formed by single-pass rolling or multi-pass rolling, the single-pass rolling is one-time variable-thickness rolling of the metal plate blank, the multi-pass rolling is rolling the metal plate blank to a predetermined thickness first, and then performing variable-thickness rolling, and in the process of forming the thickness gradient zone by the variable-thickness rolling, the pressure applied to the metal plate blank and the roll gap satisfy a negative correlation, that is, the greater the pressure, the smaller the roll gap, and the thinner the plate that can be rolled.

[0014] Further, the method further comprises: annealing heat treatment of the rolled metal plate blank, the annealing heat treatment comprising batch annealing or continuous annealing, the temperature of the batch annealing being 500-800℃, the holding time being 2-8h, and the cooling mode being furnace cooling, the temperature of the continuous annealing being 600-850℃, the holding time being 1-5min, and the cooling speed being 5-100℃ / s.

[0015] Further, the method further comprises: heating the rolled metal plate blank to 850-980℃, holding for 5-10min, and then transferring to a mold for quenching.

[0016] In a third aspect, the present application provides an automobile part. The automobile part is made of the metal sheet as described above or the metal sheet prepared by the method as described above. Therefore, the automobile part has all the features of the metal sheet as described above and the advantages thereof, which will not be repeated here. In general, the automobile part takes into account both light weight and safety. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by the drawings without creative labor for those skilled in the art.

[0018] Figure 1 The side view and top view schematic diagrams of the metal sheet provided for some embodiments of the present application; Figure 2 The trend schematic diagram of the mechanical properties and thickness change of the metal sheet provided for some embodiments of the present application; Figure 3 The side view and top view schematic diagrams of the metal sheet provided for example 1; Figure 4 The trend schematic diagram of the mechanical properties and thickness change of the metal sheet provided for example 1; Figure 5 The side view and top view schematic diagrams of the metal sheet provided for example 2; Figure 6 The trend schematic diagram of the mechanical properties and thickness change of the metal sheet provided for example 2; Figure 7 The trend schematic diagram of the mechanical properties and thickness change of the metal sheet provided for example 2 after rolling and mold quenching after heating; Figure 8 The side view and top view schematic diagrams of the metal sheet provided for example 3; Figure 9 The trend schematic diagram of the mechanical properties and thickness change of the metal sheet provided for example 3; Figure 10 The trend schematic diagram of the mechanical properties and thickness change of the metal sheet provided for example 3 after rolling and cover annealing; Figure 11 The trend schematic diagram of the mechanical properties and thickness change of the metal sheet provided for example 4 after rolling and mold quenching after heating; Figure 12 The trend schematic diagram of the mechanical properties and thickness change of the metal sheet provided for example 5 after rolling and mold quenching after heating; Figure 13 Tendency diagram of mechanical properties and thickness change of the metal sheet obtained by rolling and batch annealing for Example 6; Figure 14 Tendency diagram of mechanical properties and thickness change of the metal sheet obtained by rolling and batch annealing for Example 7; Figure 15 Schematic side and plan views of the metal sheet for Example 8; Figure 16 Tendency diagram of mechanical properties and thickness change of the metal sheet obtained by rolling for Example 8; Figure 17 Tendency diagram of mechanical properties and thickness change of the metal sheet obtained by rolling and continuous annealing for Example 8; Figure 18 Tendency diagram of mechanical properties and thickness change of the metal sheet obtained by rolling and continuous annealing for Example 9; Figure 19 Tendency diagram of mechanical properties and thickness change of the metal sheet obtained by rolling and continuous annealing for Example 10. DETAILED DESCRIPTION

[0019] Hereinafter, specific embodiments of the present application are concretely explained with reference to the accompanying drawings as appropriate. However, there are cases where unnecessary detailed explanations are omitted. For example, there are cases where detailed explanations of matters known well, repeated explanations of substantially identical structures are omitted. This is to avoid the following explanation from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following explanation are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0020] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the same, wherein any statement of a range can be modified by the use of "sub ranges" to achieve those sub-ranges. For example, a range of "1 to 10" can include any and all sub-ranges between (and including) the minimum value of 1 and the maximum value of 10, that is, any value from 1 to 10, including 1, 1.4, 4.6, 5.4, 6.8, 8, etc., in combination with any value from 10, including 10, 9, 5.6, 4.8, 4, 3, etc., and any and all sub-ranges thereof. For example, the range of "1 to 10" will include the range of "4 to 8" and the range of "4 to 6", inclusive of all values within the range of "4 to 8" and the range of "4 to 6". The same principles apply to ranges with endpoints involving all other values and sub-ranges.

[0021] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0022] Unless otherwise stated, all technical features of the present application and optional technical features can be combined with each other to form new technical solutions.

[0023] Unless otherwise stated, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, it is mentioned that the method can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0024] In the first aspect of the present application, the present application provides a metal plate. In some embodiments of the present application, the metal plate comprises at least one equal-thickness region and a thickness-gradual-change region, when the number of equal-thickness regions is greater than or equal to 2, two adjacent equal-thickness regions are connected by a thickness-gradual-change region, and the thickness of the thickness-gradual-change region continuously changes. The metal plate is an integrally formed plate, and the thickness of the entire metal plate does not have any abrupt change. The thickness of the metal plate changes, which can achieve the purpose of weight reduction, thereby realizing the lightweight of the parts made of the metal plate, saving the use of materials, reducing the cost of materials and resource consumption. Moreover, the metal plate is an integrally formed plate, which can be produced continuously, has high efficiency, and has no weld, thereby avoiding the problem of material fracture due to welding problems and improving the safety and reliability of automobile parts.

[0025] In some embodiments of the present application, the metal plate can be a stainless steel plate.

[0026] In some specific embodiments of the present application, referring to Figure 1 , the metal plate comprises three equal-thickness regions A, B and C, and two thickness-gradual-change regions a and b. The equal-thickness regions A and B are connected by the thickness-gradual-change region a, and the equal-thickness regions B and C are connected by the thickness-gradual-change region b. The thickness of the thickness-gradual-change regions a and b continuously changes, specifically, the thickness changes linearly. The metal plate is an integrally formed plate, and the thickness of the entire metal plate does not have any abrupt change, that is, the thickness of the thickness-gradual-change region continuously changes on the basis of the thickness of the equal-thickness region connected thereto.

[0027] In some specific embodiments of the present application, the metal plate comprises one equal-thickness region and one thickness-gradual-change region connected thereto. The thickness of the thickness-gradual-change region continuously changes, specifically, the thickness changes linearly or curvilinearly. Moreover, the metal plate is an integrally formed plate, and the thickness of the entire metal plate does not have any abrupt change (this case is not shown in the figure).

[0028] In some embodiments of the present application, the thicknesses of the multiple equal-thickness regions can be different, for example, referring to Figure 1 , the thickness of the equal-thickness region C is between the thicknesses of the equal-thickness regions A and B. Alternatively, the thicknesses of the multiple equal-thickness regions can be the same, for example, referring to Figure 8 , the thicknesses of the equal-thickness regions A and C are the same.

[0029] In some embodiments of the present application, the thickness of the thickness-gradual-change region can continuously increase or continuously decrease, for example, referring to Figure 1 , the thickness of the thickness-gradual-change region a continuously increases, and the thickness of the thickness-gradual-change region b continuously decreases, so as to adapt to various application environments.

[0030] In some embodiments of the present application, the yield strength and tensile strength of the metal sheet decrease with the increase of its thickness, i.e., the yield strength and tensile strength of the metal sheet are negatively correlated with its thickness. For example, referring to Figure 2 , the thicknesses of the equal-thickness zones A, C, and B increase successively, the yield strength and tensile strength of each equal-thickness zone decrease successively, the yield strength and tensile strength of the thickness gradual-change zone a decrease with the increase of the thickness, and the yield strength and tensile strength of the thickness gradual-change zone b increase with the decrease of the thickness. In addition, the plasticity (characterized by the elongation after fracture) of the metal sheet increases with the increase of the thickness, i.e., the plasticity of the metal sheet is positively correlated with its thickness. For example, referring to Figure 2 , the thicknesses of the equal-thickness zones A, C, and B increase successively, the elongation after fracture of each equal-thickness zone increases successively, the elongation after fracture of the thickness gradual-change zone a increases with the increase of the thickness, and the elongation after fracture of the thickness gradual-change zone b decreases with the decrease of the thickness. The above metal sheet can be used to manufacture automobile parts such as door impact beams, impact tubes, chassis parts, etc. On the premise of not affecting the welding with other parts, the thicknesses of the two ends are thinned, the yield strength and tensile strength of the product are improved, but the ability of the product to resist deformation is not affected, but rather is improved. In the current design, only the equal-thickness sheet with the thickest thickness zone can be selected to achieve design safety. Compared with the use of equal-thickness sheets, the weight of the metal sheet of the present application is significantly reduced, both lightweight and safety are taken into account, and various problems caused by laser tailor welding are avoided.

[0031] Alternatively, in some other embodiments of the present application, the yield strength and tensile strength of the metal sheet decrease with the increase of its thickness, while the plasticity does not change with the thickness, i.e., the plasticity is not correlated with the thickness (this case is not shown in the figure). The above metal sheet can be used to manufacture automobile parts such as energy absorption boxes and CCB tubes.

[0032] In some embodiments of the present application, the yield strength and tensile strength of the metal sheet increase with the increase of its thickness, i.e., the yield strength and tensile strength of the metal sheet are positively correlated with its thickness. For example, referring to Figure 8 and Figure 10 , the thicknesses of the equal-thickness zones A and C are the same (both are 1.75 mm), the thickness of the equal-thickness zone B (1.0 mm) is smaller than that of the equal-thickness zone A, the yield strength and tensile strength of the equal-thickness zone A are greater than those of the equal-thickness zone B, the yield strength and tensile strength of the thickness gradual-change zone d decrease with the decrease of the thickness (from 1.75 mm to 1.0 mm), and the yield strength and tensile strength of the thickness gradual-change zone e increase with the increase of the thickness (from 1.0 mm to 1.75 mm). In addition, the plasticity of the metal sheet decreases with the increase of the thickness, i.e., the plasticity of the metal sheet is negatively correlated with its thickness. For example, referring to Figure 8and Figure 10 , the thickness of the equal-thickness zone B (1.0 mm) is less than that of the equal-thickness zone A, the post-break elongation corresponding to the equal-thickness zone A is less than that corresponding to the equal-thickness zone B, the post-break elongation of the thickness-gradual-change zone d increases (from 1.75 mm to 1.0 mm) as the thickness decreases, and the post-break elongation of the thickness-gradual-change zone e decreases (from 1.0 mm to 1.75 mm) as the thickness increases. The above metal sheet can be used to manufacture automobile parts such as brake support reinforcement plates and front compartment supports.

[0033] Alternatively, in some other embodiments of the present application, the yield strength and tensile strength of the metal sheet increase as the thickness increases, and the plasticity does not change with the thickness, i.e., the plasticity is not correlated with the thickness (not shown in the figure). The above metal sheet can be used to manufacture automobile parts such as front longitudinal beams and roof cross beams.

[0034] In some embodiments of the present application, the yield strength and tensile strength of the metal sheet do not change by more than 100 MPa as the thickness changes. That is, the yield strength and tensile strength of the metal sheet do not change greatly as the thickness changes, but fluctuate within the same performance range. For example, referring to Figure 5 and Figure 7 , the thicknesses of the equal-thickness zones A, B, E, C, and D increase in turn (1.6 mm, 1.8 mm, 2 mm, 2.2 mm, and 2.85 mm, respectively), the yield strength corresponding to each equal-thickness zone differs by no more than 21 MPa, the tensile strength corresponding to each equal-thickness zone also differs by no more than 30 MPa, the yield strength of each thickness-gradual-change zone f, g, h, and i differs by no more than 21 MPa, and the tensile strength of each thickness-gradual-change zone f, g, h, and i differs by no more than 30 MPa, i.e., the yield strength and tensile strength of each region of the entire metal sheet are uniform. In addition, the plasticity of the metal sheet also changes by a small amount as the thickness changes. For example, referring to Figure 5 and Figure 7 , the thicknesses of the equal-thickness zones A, B, E, C, and D increase in turn, the post-break elongation corresponding to each equal-thickness zone differs by no more than 0.7%, and the post-break elongation of each thickness-gradual-change zone f, g, h, and i differs by no more than 0.7%, i.e., the plasticity of each region of the entire metal sheet is also uniform. The above metal sheet can be used to manufacture automobile parts such as A-pillar upper, A-pillar lower, B-pillar, mid-channel, longitudinal beam, seat cross beam, anti-collision beam, bumper, roof cross beam, and the like.

[0035] The thickness and mechanical properties (yield strength, tensile strength, plasticity) of the metal plate of the present application are variable, and the mechanical properties vary with the thickness, and the difference in mechanical properties coexists with the difference in thickness. Compared with traditional equal-thickness plates and laser-welded plates, the thickness of the metal plate with variable thickness and mechanical properties can be changed at will according to the actual design state of the part, and the light weight, material saving and cost saving are improved, the mechanical properties can change with the change of thickness, and a plurality of metal plates with different mechanical properties can be obtained, the thickness and mechanical properties of the metal plate can be designed and developed according to the actual stress state of the part, and the thickness and mechanical property distribution of the metal plate can be customized designed, so as to customize the production of automobile parts, and fully realize the needs of light weight, cost reduction and safety.

[0036] In another aspect of the present application, a method for preparing a metal plate is provided. In some embodiments of the present application, the metal plate prepared by the method can be the metal plate described above, so that the metal plate prepared by the method can have the same features and advantages as the metal plate described above, which will not be repeated here.

[0037] In some embodiments of the present application, the method comprises rolling a metal plate blank to obtain the metal plate, the metal plate comprising at least one equal-thickness region and a thickness-gradual-change region, when the number of equal-thickness regions is ≥2, two adjacent equal-thickness regions are connected by a thickness-gradual-change region, the thickness of the thickness-gradual-change region changes continuously, and the thickness of the entire metal plate has no abrupt change. The metal plate prepared by the method is an integrally formed plate, which can be produced continuously, has high efficiency, and has no welds, avoiding the problem of material fracture due to welding problems, improving the safety and reliability of automobile parts. Moreover, the thickness of the metal plate is variable, which can achieve the purpose of weight reduction, thereby realizing the light weight of the parts made of the metal plate, saving the use of materials, and reducing material cost and resource consumption.

[0038] The rolling of the present application is a cold rolling process, and the metal plate blank can be a steel coil with a thickness of 0.5-5mm.

[0039] In some embodiments of the present application, the metal plate can be formed by single pass rolling or by multi-pass rolling. Single pass rolling is a process in which a metal plate blank is rolled to a predetermined length and thickness, and then is rolled again only to change the thickness to obtain a periodic target size of the metal plate. Multi-pass rolling is a process in which a metal plate blank is first rolled to a predetermined thickness, and then is rolled again to change the thickness to obtain a periodic target size of the metal plate. In the process of changing the thickness, the product thickness and length required for rolling are first input on a control interface, and then the control program detects the real-time position of the roll gap through a displacement sensor according to the set product thickness distribution, and then provides pressure through a hydraulic cylinder to make the roll change according to the set roll gap thickness, so as to roll the metal plate with periodic distribution of different thicknesses and lengths.

[0040] In some embodiments of the present application, in the process of forming the thickness gradient zone by changing the thickness, the pressure applied to the metal plate blank and the roll gap between the rolls satisfy a negative correlation, that is, the greater the pressure, the smaller the roll gap, and the thinner the plate that can be rolled.

[0041] In some embodiments of the present application, the yield strength and tensile strength of the metal plate obtained by rolling decrease with the increase of the thickness, that is, the yield strength and tensile strength are negatively correlated with the thickness, and the plasticity of the metal plate obtained by rolling increases with the increase of the thickness, that is, the plasticity is positively correlated with the thickness.

[0042] In some embodiments of the present application, the method further comprises annealing heat treatment of the rolled metal plate blank, and the annealing heat treatment includes batch annealing or continuous annealing. The annealing heat treatment is mainly applied to cold forming materials, the batch annealing is a process in which the cold-rolled plate coil is annealed in a batch furnace in a stacked form, and the continuous annealing is a production method in which the cold-rolled plate coil is unwound and continuously passes through an annealing furnace, the annealing furnace is not sealed, and the strip steel is directly coiled without stopping.

[0043] The temperature of the batch annealing is 500-800℃, for example, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, the holding time is 2-8h, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, and the cooling method is furnace cooling. The yield strength and tensile strength of the metal plate obtained by rolling and batch annealing increase with the increase of the thickness, that is, the yield strength and tensile strength of the metal plate are positively correlated with the thickness, and the plasticity of the metal plate obtained by rolling and batch annealing decreases with the increase of the thickness, or the plasticity of the metal plate does not change with the change of the thickness.

[0044] The temperature of the continuous annealing is 700-850°C, for example, 700°C, 750°C, 800°C, 850°C, the holding time is 1-5 min, for example, 1 min, 2 min, 3 min, 4 min, 5 min, and the cooling speed is 5-100°C / s, for example, 5°C / s, 20°C / s, 40°C / s, 60°C / s, 80°C / s, 100°C / s. The yield strength and tensile strength of the metal plate obtained by rolling and continuous annealing decrease with the increase of the thickness of the metal plate, that is, the yield strength and tensile strength of the metal plate are negatively correlated with the thickness, and the plasticity of the metal plate obtained by rolling and continuous annealing does not change with the thickness.

[0045] Alternatively, in another embodiment of the present application, the method further comprises: heating the rolled metal plate blank to 850-980°C, for example, 850°C, 900°C, 950°C, 980°C, holding for 5-10 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, and then transferring to a mold for quenching. That is, the mold quenching method is used, which is mainly used for hot forming materials. The yield strength and tensile strength of the metal plate obtained by rolling and mold quenching do not change by more than 100 MPa with the change of the thickness of the metal plate, and the plasticity of the metal plate also changes by a small amplitude with the change of the thickness, that is, the mechanical properties of the metal plate are uniform.

[0046] The present application realizes the change of the thickness of the metal plate by rolling, and the metal plate can have one or more than one equal-thickness region and thickness-gradual-change region, realizes the lightweight of the material, saves the material cost, and through the matching of the thickness and the mechanical properties, the stress conditions of different parts of the automobile part can be met, the safety can be met, the traditional laser tailor-welded plate can be replaced, the cost is saved, and the risks such as brittleness and cracking of the material caused by the welding process are avoided.

[0047] In another aspect of the present application, the present application provides an automobile part. In some embodiments of the present application, the automobile part is made of the metal plate described above or the metal plate prepared by the method described above. Therefore, the automobile part has all the features and beneficial effects of the metal plate described above, which will not be repeated here. In general, the automobile part takes into account the lightweight and safety.

[0048] The specific examples of the automobile part have been described in detail above, which will not be repeated here.

[0049] Embodiments The present application will be described in more detail by the following examples, which are only for illustrative purposes and various modifications and changes can be apparent to those skilled in the art within the scope of the present application. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used as received without further purification, and all instruments used in the examples are commercially available.

[0050] Example 1 A raw steel coil with a thickness of 3.1 mm is rolled in a single pass to obtain a metal plate as shown in Figure 3 , and the dimensions of the metal plate are shown in Table 1. After the metal plate is rolled to the desired size and thickness, no subsequent treatment is performed, and the mechanical properties of each region after rolling are shown in Figure 4 . The thinner the thickness, the higher the yield strength and tensile strength, and the smaller the elongation after fracture.

[0051] The weight of the metal plate is 5.76 kg, and it is directly used to manufacture a door bumper beam. The middle 3 mm region (i.e., the equal thickness region B) has low strength and is mainly used to resist collision deformation and absorb energy. The two end 1.6 mm equal thickness regions A and 2.3 mm equal thickness regions C have high strength and are used to ensure the combination with other parts of the vehicle body, preventing deformation at the connection with other parts. If a 3 mm raw steel coil is directly used to manufacture the part, the weight is 6.96 kg, and the weight reduction using the metal plate of the present example is up to 17.2%.

[0052] Table 1

[0053] Example 2 A raw steel coil with a thickness of 2.9 mm for hot forming is rolled in a single pass to obtain a metal plate as shown in Figure 5 , and the dimensions of the metal plate are shown in Table 2. The mechanical properties of each region after rolling are shown in Figure 6 . The thinner the thickness, the higher the yield strength and tensile strength, and the smaller the elongation after fracture.

[0054] Table 2

[0055] The rough blank of the rolled metal plate is heated to 930℃ and held for 5 min, and then transferred to a mold for quenching, i.e., mold quenching. After mold quenching, the mechanical properties are as shown in Figure 7The mechanical properties (yield strength, tensile strength, plasticity) of each equal-thickness zone are basically consistent, showing the uniformity of performance, meeting the requirements of the hot forming steel for performance uniformity, and ensuring that each region of the product meets the basic collision strength requirements. The metal plate is applied to the manufacture of A column and B column.

[0056] 1.6 mm equal-thickness zone A is the deformation energy absorption zone of the part, which needs to deform and absorb energy first during the automobile collision to reduce the harm to the occupants, so the thickness design here is 1.6 mm. The weight of the part made of the metal plate is 17.95 kg. If an equal-thickness plate is used to make the part, the entire part needs a 2.9 mm equal-thickness plate, and the weight of the part is 22.81 kg, which increases by 21.31% compared to the weight of the metal plate of the embodiment, and there is no 1.6 mm zone position priority deformation condition, which is not conducive to energy absorption protection. If only a 1.6 mm equal-thickness plate is used, the thickness at other positions is insufficient to resist deformation during the collision process.

[0057] Example 3 The raw steel coil with a thickness of 1.8 mm is subjected to single-pass rolling to obtain a metal plate as shown in Figure 8 The size of the metal plate is shown in Table 3. The mechanical properties of each region after rolling are shown in Figure 9 The thinner the thickness, the higher the yield strength and tensile strength, and the smaller the elongation after fracture.

[0058] Table 3

[0059] After rolling, the metal plate needs to be annealed for heat treatment because its mechanical properties are too high and do not meet the requirements for mechanical properties. The rough metal plate after rolling is subjected to bell-type annealing, the bell-type annealing temperature is 650°C, the heating speed is 2°C / min, the holding time is 6h, and the cooling method is furnace cooling. The annealing furnace is water-cooled and air-cooled during the cooling process, and the furnace is discharged when the temperature cools to 80°C.

[0060] The mechanical properties after bell-type annealing are shown in Figure 10 After bell-type annealing, the yield strength and tensile strength increase with the increase of the thickness, and the elongation after fracture decreases with the increase of the thickness, but meets the requirement of elongation after fracture ≥ 15%.

[0061] The metal sheet is thinner in the middle and thicker at the edges, primarily used for parts in the middle that need to easily deform upon impact, requiring high elongation after fracture and a large amount of deformation participation for better energy absorption and safety. The ends require a certain thickness for drilling and fixing with other related parts, with a thickness of no less than 1.7mm. This metal sheet is used in the fabrication of parts such as the front cabin support and crossbeams. Parts made using this metal sheet weigh 4.11kg, compared to 5.40kg using a 1.75mm thick plate. This embodiment reduces weight by 23.9% while effectively absorbing energy and deforming, resulting in greater safety and reliability. Using a 1.75-1.0-1.75mm laser-welded plate increases welding costs, and the weld strength is 50% higher than the base material, leading to stress concentration and failing to meet performance requirements.

[0062] Example 4 The preparation process of the metal sheet in this embodiment is basically the same as that in Example 2. The difference is that the rolled metal sheet billet is heated to 850°C, held for 5 minutes, and then transferred to a mold for quenching. After mold quenching, its mechanical properties are as follows: Figure 11 As shown. The product in this embodiment is thin, with a thickness variation of 0.8-1.0-1.2mm. Compared with embodiment 2, the product in embodiment 4 is thinner and does not require a higher heating temperature, thus saving energy costs.

[0063] Example 5 The preparation process of the metal sheet in this embodiment is basically the same as that in Example 2. The difference is that the rolled metal sheet billet is heated to 980°C, held at that temperature for 10 minutes, and then transferred to a mold for quenching. After quenching in the mold, its mechanical properties are as follows: Figure 12 As shown. This embodiment uses 1800MPa grade hot-formed steel material, which is thick and has high strength.

[0064] Example 6 The preparation process of the metal sheet in this embodiment is basically the same as that in Example 3, except that the temperature of the bell-type annealing is 500℃ and the holding time is 8h. After bell-type annealing, its mechanical properties are as follows: Figure 13 As shown, under this annealing process, the yield strength, tensile strength, and elongation after fracture decrease with increasing thickness, and the properties show a negative correlation with thickness.

[0065] Example 7 The preparation process of the metal sheet in this embodiment is basically the same as that in Example 3, except that the temperature of the bell-type annealing is 800℃ and the holding time is 2h. After bell-type annealing, its mechanical properties are as follows: Figure 14 As shown. This embodiment uses a high-temperature, short-time annealing method; the performance varies depending on the material and under different conditions.

[0066] Example 8 A 1.6mm thick raw steel coil, after being rolled to varying thickness, yields a metal sheet as shown below. Figure 15 As shown in Table 4, the dimensions of the metal sheet are as follows. The mechanical properties of each region of the metal sheet after rolling are as follows: Figure 16 As shown, the thinner the thickness, the higher the yield strength and tensile strength, and the smaller the elongation after fracture.

[0067] Table 4

[0068] After continuous annealing at 780℃ for 5 minutes, the following was obtained: Figure 17 As shown, after annealing, the material yields. This part is manufactured using a 9-segment differential thickness plate, with the thinnest section in the middle, serving to connect the 1.1mm and 1.4mm sections at both ends. The 1.1mm and 1.4mm sections primarily bear the load, while the 1.4mm sections at both ends are the thickest and are used for connections with other parts. Compared to directly using a 1.4mm uniform thickness plate, the weight reduction reaches 19.4%.

[0069] Example 9 The preparation process of the metal sheet in this embodiment is basically the same as that in Example 8, except that the continuous annealing temperature is 700℃ and the holding time is 1 minute. After continuous annealing, its mechanical properties are as follows: Figure 18 As shown. In this embodiment, the material is different and the annealing conditions are different compared to Example 8, resulting in different mechanical properties.

[0070] Example 10 The preparation process of the metal sheet in this embodiment is basically the same as that in Example 8, except that the continuous annealing temperature is 850℃ and the holding time is 5 minutes. After continuous annealing, its mechanical properties are as follows: Figure 19 As shown.

[0071] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A metal sheet, characterized by Comprising: at least one equal-thickness zone and a thickness-gradual-change zone, when the number of equal-thickness zones is ≥2, two adjacent equal-thickness zones are connected by the thickness-gradual-change zone, the thickness of the thickness-gradual-change zone changes continuously, the metal plate is an integrally formed plate, and the thickness of the entire metal plate does not change abruptly.

2. The metal sheet according to claim 1, characterized in that, The thickness of the thickness-gradual-change zone changes continuously.

3. The metal sheet according to claim 1, characterized in that, The yield strength and tensile strength of the metal plate decrease with the increase of the thickness of the metal plate.

4. The metal sheet according to claim 1, characterized in that, The yield strength and tensile strength of the metal plate increase with the increase of the thickness of the metal plate.

5. The metal sheet according to claim 1, characterized in that The yield strength and tensile strength of the metal plate change by no more than 100 MPa with the change of the thickness of the metal plate.

6. A method of producing a metal sheet material, characterized by, Comprising: rolling a metal plate blank to obtain a metal plate, the metal plate comprises at least one equal-thickness zone and a thickness-gradual-change zone, when the number of equal-thickness zones is ≥2, two adjacent equal-thickness zones are connected by the thickness-gradual-change zone, the thickness of the thickness-gradual-change zone changes continuously, and the thickness of the entire metal plate does not change abruptly.

7. The method of claim 6, wherein, The metal plate is formed by single-pass rolling or multi-pass rolling, the single-pass rolling is one-time variable-thickness rolling of the metal plate blank, the multi-pass rolling is rolling the metal plate blank to a predetermined thickness first, and then performing variable-thickness rolling.

8. The method of claim 6, wherein, Further comprising: annealing heat treatment of the rolled metal plate blank, the annealing heat treatment comprises batch annealing or continuous annealing, the temperature of the batch annealing is 500-800℃, the holding time is 2-8h, and the cooling method is furnace cooling, the temperature of the continuous annealing is 700-850℃, the holding time is 1-5min, and the cooling speed is 5-100℃ / s.

9. The method of claim 6, wherein, Further comprising: heating the rolled metal plate blank to 850-980℃, holding for 5-10min, and then transferring to a mold for quenching.

10. An automotive part, characterized by The automobile part is made of the metal plate according to any one of claims 1-5 or the metal plate prepared by the method according to any one of claims 6-9.

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