A method for preparing surface-strengthened plate and strip

Abstract

This invention belongs to the field of surface strengthening technology and provides a method for preparing surface-strengthened strips and sheets. The method includes: rolling a metal strip and sheet using a roll set, wherein the roll set includes an upper roll and a lower roll, and at least one of the upper and lower rolls has a corrugated working surface; in the traveling direction of the metal strip and sheet, the peak misalignment value between the corresponding positions of the nth roll and the (n+1)th roll in the roll set is 40~800 μm. In this application, during the surface strengthening process of the metal strip and sheet, a corrugated roll is introduced for rolling, causing the surface layer of the metal strip and sheet to undergo localized intense plastic deformation, resulting in grain refinement and the formation of a gradient structure, thereby achieving localized surface strengthening of the strip. This method is simple to operate and suitable for continuously producing a high-smoothness, damage-free gradient nanostructure layer on metal strips, which is beneficial for significantly improving the performance of the strip and has high production efficiency.

Description

Technical Field

[0001] This invention relates to the field of surface strengthening technology, and in particular to a method for preparing surface-strengthened plates and strips. Background Technology

[0002] Metallic materials occupy a vital position in the development and research of many materials. Many metallic materials experience workpiece failure during use, and these failures often originate from the material surface, such as fatigue crack initiation, friction and wear, and corrosion. To address these issues and improve the application of metallic materials, surface strengthening techniques are needed to extend their service life. Since Academician Lu Ke and others discovered surface gradient strengthening technology, gradient strengthening structures have been formed on the surface of metallic materials. This allows for the simultaneous improvement of strength, corrosion resistance, and fatigue resistance while minimizing or eliminating the loss of plasticity.

[0003] Currently, there are many methods for introducing gradient strengthening onto the surface of metallic materials, such as shot peening, deep rolling, laser surface treatment, surface mechanical rolling, and surface mechanical compaction. However, these techniques all have certain limitations. For example, while shot peening is not limited by the size and shape of the sample, it results in a high surface roughness and low surface finish. Deep rolling, surface mechanical rolling, and surface mechanical compaction are more suitable for rotating parts. For large sheet or strip metal workpieces, the processing speed and local micro-area plastic deformation have limitations. Therefore, there is currently no method for the continuous production of gradient nanostructured sheets and strips, and there is an urgent need to design an efficient method for surface mechanical strengthening of strips. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a method for preparing surface-strengthened sheet and strip. The method provided in this application enables the metal sheet and strip to achieve both surface strengthening and surface smoothness without damage.

[0005] In view of this, this application provides a method for preparing surface-strengthened plate strips, comprising the following steps:

[0006] Metal strips are rolled using a roll set, which includes an upper roll and a lower roll, and at least one of the upper roll and the lower roll has a corrugated working surface.

[0007] During the rolling process, multiple roll groups are arranged in the traveling direction of the metal material strip, and the working surface shape of each upper roll in the multiple roll groups is the same and / or the working surface shape of each lower roll is the same.

[0008] In the traveling direction of the metal strip, the peak misalignment value M between the nth roll and the (n+1th roll in the plurality of roll groups is 40~800μm.

[0009] In some specific embodiments, during the roll forming process, the diameter corresponding to the contact area between the upper and / or lower roll crests and the metal strip is denoted as d1, and the diameter corresponding to the contact area between the upper and / or lower roll troughs and the metal strip is denoted as d2, where d1 = 1~8mm and d1 = 2d2.

[0010] In some specific embodiments, the height difference between adjacent peaks and troughs of the upper roll and / or the lower roll is denoted as h, where h ≥ 0.4 mm.

[0011] In some specific embodiments, the number of passes in the rolling process is ≥1.

[0012] In some specific embodiments, in the roll group, the working surfaces of the upper roll and the lower roll are both corrugated, the crests of the upper roll and the crests of the lower roll correspond to each other, and the troughs of the upper roll and the troughs of the lower roll correspond to each other.

[0013] In some specific embodiments, the misalignment value M is 40~400μm.

[0014] In some specific embodiments, the peak diameter of the upper roll and / or lower roll is denoted as D1, the trough diameter is denoted as D2, and 20mm≤D1=D2+2h≤200mm.

[0015] In some specific embodiments, the metal material is stainless steel, and in the upper and / or lower rolls, d1 is 2~8mm, the misalignment value M is 100~600μm; the thickness of the stainless steel is 0.4mm~4.5mm.

[0016] In some specific embodiments, the metal material is a titanium alloy, and in the upper and / or lower rolls, d1 is 1~4mm and the misalignment value M is 100~400μm; and / or, the metal material is an aluminum alloy, and in the upper and / or lower rolls, d1 is 2~6mm and the misalignment value M is 100~400μm.

[0017] In some specific embodiments, the rolling speed of the upper roll is 2000~20000 mm / min, and / or the rolling speed of the lower roll is 2000~20000 mm / min; and / or the single-pass indentation depth of the roll forming is 30~400 μm; and / or the working surfaces of the upper and lower rolls of the last roll group in the plurality of roll groups are both planes.

[0018] This application provides a method for preparing surface-strengthened sheet and strip, which involves rolling a metal sheet and strip using a roll set, the roll set including an upper roll and a lower roll, wherein at least one of the upper roll and the lower roll has a corrugated working surface. Through the rolling process, localized stress concentration and strain gradients are formed on the surface of the metal sheet and strip, ultimately achieving surface strengthening of the metal sheet and strip. In the process of preparing the surface-strengthened sheet and strip, by introducing upper and / or lower rolls with corrugated working surfaces, the corrugated working surfaces act on the strip surface, introducing a corrugated track. The strain gradient of the trace causes the surface layer of the metal strip to undergo grain refinement through localized intense plastic deformation, forming a gradient structure, thereby achieving surface strengthening of the metal strip. Furthermore, the limitation of the misalignment value of the peaks of adjacent rolls in multiple roll groups ensures that each roll group is repeatedly processed by other roll groups in the rolling ripple trajectory formed on the surface of the metal strip, with multiple overlaps of local plastic deformation zones. This results in a continuous and misaligned near-smooth gradient structure on the surface of the metal strip, achieving both surface strengthening and surface smoothness without damage. Attached Figure Description

[0019] Figure 1 Figure A is a schematic diagram of the interaction between a single roll and the strip material of the present invention. Figure B is a side view of the roll and Figure C is a schematic diagram of the interaction between the roll group and the strip material.

[0020] Figure 2 Figure a is a planar assembly diagram of the multiple sets of rolls used in the rolling process of the present invention. Figure b is a three-dimensional assembly diagram of the multiple sets of rolls.

[0021] Figure 3 This is a cross-sectional hardness curve of 304 steel strip after surface strengthening of three types of rolls in Embodiment 1 of the present invention;

[0022] Figure 4 This is a cross-sectional hardness curve of the 304 sheet and strip after double-sided surface strengthening in Embodiment 2 of the present invention;

[0023] Figure 5 The images show the microstructure of the strip at different depths in Embodiment 2 of the present invention. Figure 5 a represents the morphology of the outermost grain. Figure 5 b represents the tissue morphology at a distance of 600 μm from the surface. Figure 5 c represents the tissue morphology at a distance of 2 mm from the surface;

[0024] Figure 6 This refers to the cross-sectional hardness distribution of the 310s stainless steel sheet and strip in Example 3 after processing.

[0025] Figure 7 This is the distribution of the microstructure of the TA2 section with depth in Example 4;

[0026] Figure 8 This is the distribution of hardness of the TA2 section with depth in Example 4;

[0027] Figure 9 The images shown are laser confocal images and 3-D contour maps of 2091 aluminum alloy in Example 5. Figure a is a laser confocal image of 2091 aluminum alloy, and Figure b is a 3-D contour map of 2091 aluminum alloy.

[0028] Figure 10 The distribution of cross-sectional hardness with depth in the 2091 aluminum alloy of Example 5;

[0029] Figure 11 These are hardness distribution diagrams of the cross-sections of the surface-strengthened metal sheets and strips in Examples 6-9;

[0030] Figure 12 These are hardness distribution diagrams of the cross-sections of the surface-strengthened metal sheets and strips in Examples 10-13;

[0031] Figure 13 This is a hardness distribution diagram of the cross-section of the surface-strengthened metal sheet / strip in Comparative Example 1.

[0032] Figure 14 The images shown are laser confocal images and 3-D contour maps of stainless steel after surface strengthening, as shown in Comparative Example 1. Figure a is the laser confocal image of stainless steel, and Figure b is the 3-D contour map of stainless steel.

[0033] Figure 15 The images shown are laser confocal images and 3-D contour maps of the surface-strengthened stainless steel in Comparative Example 2. Figure a is the laser confocal image of the stainless steel, and Figure b is the 3-D contour map of the stainless steel.

[0034] Figure 16 The images shown are laser confocal images and 3-D contour maps of the aluminum alloy after surface strengthening, as shown in Figure 3. Figure a is the laser confocal image of the aluminum alloy, and Figure b is the 3-D contour map of the aluminum alloy.

[0035] Figure 17 This is a hardness distribution diagram of the cross-section of the metal material with surface mechanical rolling treatment, as shown in Comparative Example 4.

[0036] Figure 18 This is a hardness distribution diagram of the cross-section of the metal material with surface mechanical rolling treatment, as shown in Comparative Example 5. Detailed Implementation

[0037] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0038] In view of the requirements for surface strengthening and surface finish of metallic materials in the prior art, this application provides a method for preparing surface-strengthened sheet and strip. This method employs upper and / or lower rolls with corrugated working surfaces, and limits the crest misalignment value at corresponding positions of adjacent rolls. This allows the metallic sheet and strip to undergo repeated deformation in localized plastic deformation zones while simultaneously forming a strain gradient strengthening layer on the surface. This ensures surface finish and surface strengthening, and avoids problems such as cracking and surface peeling of the strip. Specifically, this invention discloses a method for preparing surface-strengthened sheet and strip, including the following steps:

[0039] Metal strips are rolled using a roll set, which includes an upper roll and a lower roll, and at least one of the upper roll and the lower roll has a corrugated working surface.

[0040] During the rolling process, multiple roll groups are arranged in the traveling direction of the metal material strip, and the working surface shape of each upper roll in the multiple roll groups is the same and / or the working surface shape of each lower roll is the same.

[0041] In the traveling direction of the metal strip, the peak misalignment value M between the nth roll and the (n+1th roll in the roll group is 40~800μm.

[0042] In the method for preparing surface-strengthened strip and sheet provided in this application, the working surface shape of the roll is designed to be corrugated. By controlling the shape of the surface corrugations, a strain gradient and local stress concentration are introduced at the interaction surface between the roll and the strip and sheet, thereby achieving localized severe plastic deformation of the strip and sheet surface. A schematic diagram of the roll shape and the interaction between the roll and the strip and sheet is shown below. Figure 1 As shown in the diagram, Figure A is a schematic diagram of the interaction between the upper roll and the strip, Figure B is a side view of the roll, and Figure C is a schematic diagram of the interaction between the roll group and the strip; in the figures, 1 is the upper roll, 2 is the metal strip, and 3 is the lower roll. To achieve continuous deformation and repeated rolling deformation in local deformation zones to improve production efficiency and control the surface quality of the strip, multiple roll groups are arranged for rolling, as shown in the schematic diagram. Figure 2As shown, the metal strip is used as a raw material, and its preparation method follows methods well known to those skilled in the art. This application does not impose any special restrictions on this method. The material of the metal strip is not particularly limited; it can be an aluminum alloy, a titanium alloy, a nickel-based alloy, or stainless steel. While the material of the metal strip is not particularly limited in this application, the relevant parameters of the roll set differ depending on the type of metal strip. This application does not impose any special restrictions on the thickness of the metal strip. For example, the thickness of the metal strip is 0.2 mm to 10 mm; more specifically, the thickness is 0.4 mm to 7 mm; and even more specifically, the thickness is 1 mm to 5 mm.

[0043] This application employs multiple roll groups to roll metal strips, each roll group including an upper roll and a lower roll, with at least one of the upper and lower rolls having a corrugated working surface. The metal strip is fed along a direction perpendicular to the roll group's travel direction, and the upper and lower rolls can roll freely. After processing by the roll group, the surface of the metal strip is strengthened. In this application, a schematic diagram of the structure of the upper roll and / or lower roll of the roll group is shown below. Figure 1 As shown; specifically, the working surface of the upper roll of the roll assembly is corrugated, and the working surface of the lower roll is flat, or the working surface of the upper roll of the roll assembly is wavy, and the working surface of the lower roll is wavy (e.g. Figure 1 (See Figure C in the text). Similarly, the working surface of the lower roll of the roll group is corrugated, and the working surface of the upper roll is flat. That is, the working surfaces of the upper and lower rolls of the roll group are selected according to the processing requirements of the metal material strip, and this application does not impose any special restrictions on this.

[0044] Specifically, taking a roll group where both the upper and lower rolls have corrugated working surfaces as an example, when the roll group is working, the corrugated peaks of the upper and lower rolls act on the surface of the metal strip, introducing a strain gradient. The surface of the metal strip undergoes localized intense plastic deformation, resulting in grain refinement and a gradient structure, thus achieving localized strengthening of the upper and lower surfaces. However, this rolling process creates a single deformation zone on the surface of the metal strip, and the rolling trajectory is clearly visible to the naked eye, affecting the smoothness, uniformity, and surface strengthening effect of the metal strip. Therefore, research has introduced a combination of the strain gradient after the metal strip undergoes roll forming and the repeated application of the localized plastic deformation zone, achieving a smoother surface for the metal strip. A smooth gradient structure; from a technical perspective, during the roll rolling process, in the direction of travel of the metal strip, in multiple roll groups, the peak misalignment value M between the nth roll and the (n+1th)th roll is 40~800μm. That is, the peak misalignment value M at the same position of adjacent rolls is 40~800μm. For example, the misalignment value M between the first peak of the first upper roll and the first peak of the second upper roll in multiple roll groups is M, the misalignment value M between the second peak of the first upper roll and the second peak of the second upper roll is M, and so on, until the nth peak of the first upper roll and the nth peak of the second upper roll are also M. Similarly, the peaks of the second and third upper rolls also exhibit the aforementioned misalignment value M. This misalignment value M is determined by the diameter d1 corresponding to the contact area between the trough of the upper roll and / or lower roll and the metal strip, and the roll rolling reduction a. p The decision, the specific relation is as follows:

[0045] ;

[0046] The left side of the above equation represents the lateral width (i.e., the local deformation zone) of the trajectory formed by a single upper or lower roll on the surface of the metal strip. This lateral width needs to be filled by n peak misalignment values ​​M to achieve surface strengthening, uniformity, and a near-smooth metal strip. Thus, in the rolling process of multiple roll groups, the rolling trajectory of one roll group on the metal strip is repeatedly rolled by subsequent roll groups. Ideally, the larger n is, the smaller M is, the better the surface strengthening effect, but it also increases the difficulty of roll processing and damages the surface of the metal strip. Therefore, in order to balance the surface morphology, strengthening effect, and roll processing of the metal strip, the preferred value of n is 2 to 10, and the misalignment value M is... The value is 40~800μm; specifically, the misalignment value M is 80~400μm; for example, the misalignment value in this application is 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 200μm, 300μm, 500μm, 600μm or 700μm; more specifically, the metal material is stainless steel with a crest misalignment value of 100~600μm, the metal material is titanium alloy with a crest misalignment value of 100~400μm, the metal material is aluminum alloy with a crest misalignment value of 100~400μm; that is, according to the strengthening requirements of the metal material strip, rolls with crest misalignment are selected for processing to obtain full surface coverage strengthening and ensure the surface finish of the metal material strip.

[0047] During the roll forming process, the diameter corresponding to the contact area between the crest of the upper and / or lower rolls and the metal strip is denoted as d1, and the diameter corresponding to the contact area between the trough of the upper and / or lower rolls and the metal strip is denoted as d2, where d1 = 1~8mm, d1 = 2d2. The aforementioned contact area is actually the contact point between the crest of the upper and / or lower rolls and the metal strip, and the diameter corresponding to the circle containing this contact point is d1. Specifically, if the metal material is stainless steel, d1 is 2~8mm, more specifically, d1 is 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, or 8mm; if the metal material is titanium alloy, d1 is 1~4mm, more specifically, d1 is 1mm, 1.5mm, 2mm, 3mm, or 4mm; if the metal material is aluminum alloy, d1 is 2~6mm, more specifically, d1 is 2mm, 3mm, 4mm, 5mm, or 6mm. d1 and d2, to a certain extent, affect the surface roughness and cracking of the metal strip. The height difference between adjacent peaks and troughs of the upper and / or lower rolls is h, and the distance between adjacent peaks and troughs is L. Specific markings are as follows: Figure 1Figure A shows the values ​​of h ≥ 0.4 mm and L ≥ 3 mm. In this application, the number of roll groups = L / M. Theoretically, a smaller L is more conducive to obtaining strips with good surface quality, but a smaller L will increase the processing difficulty of the rolls. To balance the two, L should be at least ≥ 3 mm. The roll diameter of the crest of the upper roll and / or the lower roll is D1, and the roll diameter of the trough of the upper roll and / or the lower roll is D2. That is, overall, the maximum radial diameter (where the crest is located) of the upper roll and / or the lower roll is D1, and the minimum radial diameter (where the trough is located) is D2. 20 mm ≤ D1 = D2 + 2h ≤ 200 mm. Specifically, 30 mm ≤ D1 ≤ 80 mm, and h is 0.6 mm to 3 mm; more specifically, 40 mm ≤ D1 ≤ 50 mm, and h is 0.8 mm to 1.2 mm.

[0048] More specifically, the upper roll and / or lower roll may include the following specifications and dimensions:

[0049] 1) The metal material sheet and strip are made of stainless steel, with D1 being 50mm, d1 being 8mm, D2 being 44mm, d2 being 4mm, h being 3mm, d2 being 4mm, L being 5.2mm, and M being 100μm;

[0050] 2) The metal material strip is stainless steel, with D1 being 30mm, d1 being 4mm, D2 being 29.2mm, d2 being 2mm, h being 0.4mm, d2 being 2mm, L being 3mm, and M being 100μm;

[0051] 3) The metal material sheet and strip are made of stainless steel, with D1 being 30mm, d1 being 4mm, D2 being 29.2mm, d2 being 2mm, h being 0.4mm, d2 being 2mm, L being 3mm, and M being 200μm;

[0052] 4) The metal material sheet and strip are made of stainless steel, with D1 being 30mm, d1 being 4mm, D2 being 29.2mm, d2 being 2mm, h being 0.4mm, d2 being 2mm, L being 3mm, and M being 400μm;

[0053] 5) The metal material sheet and strip are made of stainless steel, with D1 being 30mm, d1 being 4mm, D2 being 29.2mm, d2 being 2mm, h being 0.4mm, d2 being 2mm, L being 3mm, and M being 600μm;

[0054] 6) The metal material strip is made of titanium alloy, with D1 = 20mm, d1 = 4mm, D2 = 19.2mm, d2 = 2mm, h = 0.4mm, L = 2mm, and M = 200μm;

[0055] 7) The metal material strip is made of aluminum alloy, with D1 being 30mm, d1 being 2mm, D2 being 28.4mm, d2 being 1mm, h being 0.8mm, L being 6mm, and M being 100μm.

[0056] During the rolling process, the rolling speed of the upper roll and / or the lower roll is 2000~20000 mm / min, specifically, the rolling speed of the upper roll and / or the lower roll is 4000~10000 mm / min; in a specific embodiment, the rolling speed of the upper roll and the lower roll is the same. The single indentation depth is 30~400 μm, specifically, the single indentation depth is 40~200 μm, more specifically, the single indentation depth is 100~150 μm.

[0057] Furthermore, the working surfaces of the upper and lower rolls of the last roll group in the plurality of roll groups are both planar.

[0058] In the process of preparing surface-strengthened strips, this invention introduces a corrugated working surface on the surface of the upper and / or lower rolls, and uses local plastic deformation during the rolling process to achieve grain refinement, thereby introducing a strain gradient. Furthermore, by combining the control of the peak misalignment value and the indentation depth, surface strengthening is achieved while ensuring the surface smoothness and non-destructive preparation of the metal strip.

[0059] To further understand the present invention, the method for preparing surface-strengthened plate and strip provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0060] Example 1

[0061] Three 3mm thick 304 stainless steel strips were placed in a set of rolls of different specifications for roll forming. The upper roll of the roll set was corrugated, and the lower roll was a plain roll. The rolling speed of the upper and lower rolls was 4000mm / min, and the misalignment value M was 100μm.

[0062] The specific parameters of the upper roller used in Sample 1 are as follows: D1 is 50mm, d1 is 8mm, D2 is 44mm, d2 is 4mm, h is 3mm, L is 5.2mm; the pressing depth is 100μm.

[0063] In this embodiment, the specific parameters of the upper roller selected for sample 2 are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, L is 3mm; the pressing depth is 100μm;

[0064] In this embodiment, the specific parameters of the upper roller selected for sample 3 are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, L is 3mm; the pressing depth is 200μm;

[0065] The surface of the stainless steel sheet and strip is significantly strengthened after roll forming, resulting in a mirror-like surface and a cross-sectional hardness distribution as shown in the figure. Figure 3 As shown in the figure. This embodiment demonstrates the feasibility of the method provided by the present invention, which can realize the preparation of single-sided gradient strip by setting the upper roll to be corrugated and the lower roll to be a normal flat roll. It also shows that reducing the roll diameter D1 and lowering the effective end d1 are beneficial to surface strengthening.

[0066] Example 2

[0067] A 4.5mm thick 304 stainless steel strip is placed in four sets of rolls for roll forming. The working surfaces of the upper and lower rolls are corrugated. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 100μm, and the misalignment value is 100μm.

[0068] In this embodiment, the specific parameters of the upper and lower rolls are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, and L is 3mm.

[0069] The stainless steel sheet and strip are significantly strengthened after roll forming, and the surface of the material is mirror-like. Figure 4 The results show that a gradient layer was constructed on both sides of the sample, with a thickness of ~2mm. The surface hardness increased from the original ~200HV to over 500HV. Figure 5 The microstructure of stainless steel sheet / strip at different depths is shown. Figure 5 a shows the surface microstructure, where the grains are significantly refined to ~50 nm. 5b shows the microstructure at a distance of 600 μm from the surface, which consists of deformed laths. 5c shows the microstructure at a distance of 2 mm from the surface, which is a typical coarse-grained microstructure.

[0070] Example 3

[0071] A 0.4mm thick 310s stainless steel strip is placed in an eight-roll mill for roll forming. The working surfaces of the upper and lower rolls are corrugated. The rolling speed of the upper and lower rolls is 10000mm / min, the indentation depth is 100μm, and the misalignment value is 100μm.

[0072] In this embodiment, the specific parameters of the upper and lower rolls are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, and L is 3mm.

[0073] The stainless steel sheet and strip are significantly strengthened after roll forming, and the surface of the material is mirror-like. Figure 6 The results show that the hardness distribution of the cross-section of 310s stainless steel strip after treatment indicates that a gradient layer is constructed on both sides of the sample, increasing the surface hardness to over 400 HV. This example demonstrates that the same technical effect of constructing a double-sided gradient layer can be achieved for thin stainless steel strips.

[0074] Example 4

[0075] A 2mm thick TA2 titanium alloy sheet and strip is placed in a set of rolls for roll forming. The working surfaces of the upper and lower rolls of the roll set are corrugated. The rolling speed of the upper and lower rolls is 6000mm / min, the indentation depth is 0.20mm, and the misalignment value is 200μm.

[0076] In this embodiment, the specific parameters of the upper and lower rolls are: D1 is 20mm, d1 is 4mm, D2 is 19.2mm, d2 is 2mm, h is 0.4mm, and L is 2mm.

[0077] The TA2 strip and sheet, after roll forming, exhibits a good surface finish and forms a significant gradient nanotwin structure, such as... Figure 7 As shown, the twin density gradually increases and the grains gradually refine as the distance from the surface of the strip increases; among them, the near-surface area is significantly strengthened, and the cross-sectional hardness is as follows: Figure 8 As shown, the surface hardness of the surface-strengthened titanium alloy sheet and strip is uniform, increasing to approximately 250 HV.

[0078] Example 5

[0079] A 0.5mm thick 2091 aluminum alloy strip is placed in two sets of rolls for roll forming. The working surfaces of the upper and lower rolls of the roll sets are corrugated. The rolling speed of the upper and lower rolls is 3000mm / min, the indentation depth is 150μm, and the misalignment value is 100μm.

[0080] In this embodiment, the specific parameters of the upper and lower rolls are: D1 is 30mm, d1 is 2mm, D2 is 28.4mm, d2 is 1mm, h is 0.8mm, and L is 6mm.

[0081] The surface of the aluminum alloy strip after roll forming is significantly strengthened, and the material surface is mirror-like. Laser confocal images and 3D contour maps are shown below. Figure 9 Cross-sectional hardness distribution as follows Figure 10 As shown.

[0082] Example 6

[0083] A 3mm thick 304 stainless steel strip is placed in two sets of rolls for roll forming. The upper roll of the roll set has a corrugated working surface, while the lower roll has a flat working surface. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 200μm, and the misalignment value is 600μm.

[0084] In this embodiment, the specific parameters of the upper roller are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, and L is 3mm.

[0085] The surface of the stainless steel sheet and strip is significantly strengthened after roll forming, and the cross-sectional hardness distribution is as follows: Figure 11 As shown in Sample 1.

[0086] Example 7

[0087] A 3mm thick 304 stainless steel strip is placed in two sets of rolls for roll forming. The upper roll of the roll set has a corrugated working surface, while the lower roll has a flat working surface. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 200μm, and the misalignment value is 400μm.

[0088] In this embodiment, the specific parameters of the upper roller are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, and L is 3mm.

[0089] The surface of the stainless steel sheet and strip is significantly strengthened after roll forming, and the cross-sectional hardness distribution is as follows: Figure 11 As shown in Sample 2.

[0090] Example 8

[0091] A 3mm thick 304 stainless steel strip is placed in two sets of rolls for roll forming. The upper roll of the roll set has a corrugated working surface, while the lower roll has a flat working surface. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 200μm, and the misalignment value is 200μm.

[0092] In this embodiment, the specific parameters of the upper roller are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, and L is 3mm.

[0093] The surface of the stainless steel sheet and strip is significantly strengthened after roll forming, and the cross-sectional hardness distribution is as follows: Figure 11 As shown in sample 3.

[0094] Example 9

[0095] A 3mm thick 304 stainless steel strip is placed in two sets of rolls for roll forming. The upper roll of the roll set has a corrugated working surface, while the lower roll has a flat working surface. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 200μm, and the misalignment value is 100μm.

[0096] In this embodiment, the specific parameters of the upper roller are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, and L is 3mm.

[0097] The surface of the stainless steel sheet and strip is significantly strengthened after roll forming, and the cross-sectional hardness distribution is as follows: Figure 11 As shown in Sample 4.

[0098] The difference between the four processes in Examples 6-9 is that the misalignment values ​​of adjacent peaks are different, the surface roughness of the four samples decreases significantly as the misalignment value decreases, and the gradient layer thickness is similar; among them, the surface hardness of sample 1 is ~420Hv, the surface hardness of samples 2 and 3 is ~430Hv, and the surface hardness of sample 4 is ~530Hv. This shows that within a certain range, with fixed roll parameters, reducing the misalignment value can improve the surface hardness and reduce the surface roughness.

[0099] Example 10

[0100] A 3mm thick 304 stainless steel strip is placed in two sets of rolls for roll forming. The upper roll of the roll set has a corrugated working surface, while the lower roll has a flat working surface. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 200μm, and the misalignment value is 50μm.

[0101] In this embodiment, the specific parameters of the upper roller are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, and L is 3mm.

[0102] The surface of the stainless steel sheet and strip is significantly strengthened after roll forming, and the cross-sectional hardness distribution is as follows: Figure 12 As shown in Sample 1.

[0103] Example 11

[0104] A 3mm thick 304 stainless steel strip is placed in two sets of rolls for roll forming. The upper roll of the roll set has a corrugated working surface, while the lower roll has a flat working surface. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 200μm, and the misalignment value is 30μm.

[0105] In this embodiment, the specific parameters of the upper roller are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, and L is 3mm.

[0106] The surface of the stainless steel sheet and strip is significantly strengthened after roll forming, and the cross-sectional hardness distribution is as follows: Figure 12 As shown in Sample 2.

[0107] Example 12

[0108] A 3mm thick 304 stainless steel strip is placed in two sets of rolls for roll forming. The upper roll of the roll set has a corrugated working surface, while the lower roll has a flat working surface. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 200μm, and the misalignment value is 15μm.

[0109] In this embodiment, the specific parameters of the upper roller are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, and L is 3mm.

[0110] The surface of the stainless steel sheet and strip is significantly strengthened after roll forming, and the cross-sectional hardness distribution is as follows: Figure 12 As shown in sample 3.

[0111] Example 13

[0112] A 3mm thick 304 stainless steel strip is placed in two sets of rolls for roll forming. The upper roll of the roll set has a corrugated working surface, while the lower roll has a flat working surface. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 200μm, and the misalignment value is 10μm.

[0113] In this embodiment, the specific parameters of the upper roller are: D1 is 30mm, d1 is 4mm, D2 is 29.2mm, d2 is 2mm, h is 0.4mm, and L is 3mm.

[0114] The surface of the stainless steel sheet and strip is significantly strengthened after roll forming, and the cross-sectional hardness distribution is as follows: Figure 12 As shown in Sample 4.

[0115] The difference between the four processes in Examples 10-13 lies in the different misalignment values ​​of adjacent peaks. Sample 1 uses a misalignment value of 50 μm, Sample 2 uses a misalignment value of 30 μm, Sample 3 uses a misalignment value of 15 μm, and Sample 4 uses a misalignment value of 10 μm. The surface roughness of all four samples can reach Ra < 0.2 μm, and the cross-sectional hardness distribution is almost the same. This means that a misalignment value that is too small is meaningless for improving hardness and surface roughness, but will reduce efficiency.

[0116] Comparative Example 1

[0117] A 3mm thick 304 stainless steel strip is placed in two sets of rolls for roll forming. The upper roll of the roll set has a corrugated working surface, while the lower roll has a flat working surface. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 200μm, and the misalignment value is 800μm.

[0118] In this embodiment, the specific parameters of the upper roller are: D1 is 50mm, d1 is 8mm, D2 is 48.4mm, d2 is 4mm, h is 0.8mm, and L is 6mm.

[0119] The surface of the stainless steel sheet and strip undergoes slight strengthening after roll forming, with the hardness increasing to approximately 225HV~270HV. However, the surface hardness distribution is uneven, and the cross-sectional hardness distribution is also uneven. Figure 13 As shown; in addition, larger misalignment values ​​result in more pronounced surface undulations, such as Figure 14 As shown.

[0120] Comparative Example 2

[0121] A 3mm thick 304 stainless steel strip is placed in two sets of rolls for roll forming. The upper roll of the roll set has a corrugated working surface, while the lower roll has a flat working surface. The rolling speed of the upper and lower rolls is 4000mm / min, the indentation depth is 200μm, and the misalignment value is 800μm.

[0122] In this embodiment, the specific parameters of the upper roller are: D1 is 30mm, d1 is 1mm, D2 is 29.2mm, d2 is 0.5mm, h is 0.4mm, and L is 3mm.

[0123] Cracks appear on the surface of stainless steel sheet and strip after roll forming, resulting in a decrease in surface quality, such as... Figure 15 As shown, a smaller d1 value may increase the surface contact stress, which is beneficial to surface grain refinement, but too small a d1 value will lead to the initiation of surface cracks.

[0124] Comparative Example 3

[0125] A 0.5mm thick 2091 aluminum alloy strip is placed in two sets of rolls for roll forming. The working surfaces of the upper and lower rolls of both sets of rolls are corrugated. The rolling speed of the upper and lower rolls is 3000mm / min, the indentation depth is 150μm, and the misalignment value is 100μm.

[0126] In this embodiment, the specific parameters of the upper and lower rolls are: D1 is 30mm, d1 is 1mm, D2 is 28.4mm, d2 is 0.5mm, h is 0.8mm, and L is 6mm.

[0127] The surface of the aluminum alloy strip after roll forming shows peeling, such as Figure 16 As shown.

[0128] Comparative Example 4

[0129] Gradient nanostructured 304 sheet and strip were prepared using surface mechanical rolling technique (P-SMRT) on flat plates. The rolling speed was 2000 mm / min, the final pass indentation was 50 μm, and one pass was performed on each side. The line spacing during the rolling process was 50 μm. The processing time for a 40 mm × 200 mm sheet and strip was 80 min. The cross-sectional hardness distribution was as follows. Figure 17 As shown, the technical effect achieved by the present invention is similar, but the time required to prepare the same size strip using the method of this application is only 3 minutes.

[0130] Comparative Example 5

[0131] Gradient nanostructured 304 strips were prepared using surface mechanical rolling technique (P-SMRT) on flat plates. The rolling speed was 2000 mm / min, the final pass indentation was 50 μm, and three passes were performed on one side. The line spacing during the rolling process was 100 μm. The processing time for a 40 mm × 200 mm strip was 120 min. The cross-sectional hardness distribution was as follows: Figure 18 As shown, the technical effect achieved by the present invention is similar, but the time required to prepare the same size strip by using the method of the present invention is only 5 minutes.

[0132] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0133] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a surface-strengthened plate or strip, comprising the following steps: Metal strips are rolled using a roll set, which includes an upper roll and a lower roll, and at least one of the upper roll and the lower roll has a corrugated working surface. During the rolling process, multiple roll groups are arranged in the traveling direction of the metal material strip, and the working surface shape of each upper roll in the multiple roll groups is the same and / or the working surface shape of each lower roll is the same. In the traveling direction of the metal strip, the peak misalignment value M between the nth roll and the (n+1th roll) in the plurality of roll groups is 40~800μm, that is, the peak misalignment value M at the same position of adjacent rolls is 40~800μm.

2. The method according to claim 1, characterized in that, During the roll forming process, the diameter of the contact area between the upper and / or lower roll crests and the metal strip is denoted as d1, and the diameter of the contact area between the upper and / or lower roll troughs and the metal strip is denoted as d2, where d1 = 1~8mm and d2 = 2d2.

3. The method according to claim 1, characterized in that, The height difference between adjacent peaks and troughs of the upper roll and / or the lower roll is denoted as h, where h ≥ 0.4 mm.

4. The method according to claim 1 or 2, characterized in that, The number of passes in the rolling process is ≥1.

5. The method according to claim 1 or 2, characterized in that, In the roll group, the working surfaces of the upper roll and the lower roll are corrugated, the crest of the upper roll corresponds to the crest of the lower roll, and the trough of the upper roll corresponds to the trough of the lower roll.

6. The method according to claim 1 or 2, characterized in that, The misalignment value M is 40~400μm.

7. The method according to claim 3, characterized in that, The peak diameter of the upper and / or lower rolls is denoted as D1, and the trough diameter is denoted as D2, and 20mm≤D1=D2+2h≤200mm.

8. The method according to claim 1, characterized in that, The metal material is stainless steel, and in the upper and / or lower rolls, d1 is 2~8mm, and the misalignment value M is 100~600μm; the thickness of the stainless steel is 0.4mm~4.5mm.

9. The method according to claim 1, characterized in that, The metal material is a titanium alloy, and in the upper and / or lower rolls, d1 is 1~4mm and the misalignment value M is 100~400μm; and / or, the metal material is an aluminum alloy, and in the upper and / or lower rolls, d1 is 2~6mm and the misalignment value M is 100~400μm.

10. The method according to claim 1 or 2, characterized in that, The rolling speed of the upper roll is 2000~20000 mm / min, and / or the rolling speed of the lower roll is 2000~20000 mm / min; And / or, the single-pass indentation depth of the rolling process is 30~400μm, and / or, the working surfaces of the upper and lower rolls of the last roll group in the plurality of roll groups are both planes.

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