A method of forming a titanium alloy sheet overwrap roll form

Abstract

The present application relates to the field of titanium alloy cylinder structure forming, in particular to a method for forming a titanium alloy plate covering and rolling, comprising the following specific steps: S1: calculating size; S2: blanking and processing bevel; S3: fixing covering plate: placing the covering plate on the rolling plate, aligning around, and then spot welding and fixing; S4: pre-bending treatment; S5: rolling forming: achieving rolling effect through multiple plastic deformation; S6: natural jointing and adjusting; S7: removing covering layer and welding. The present application changes the stress and strain state during cylinder rolling by reasonably arranging the covering plate, so that the chord direction is not under compression stress during cylinder rolling, the chord direction does not occur compression deformation during rolling, and the chord direction tensile yield strength is avoided from being reduced.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy cylindrical structure forming, and in particular to a method for forming titanium alloy sheet by wrapping and rolling. Background Technology

[0002] Titanium alloys, as a lightweight structural material, possess excellent properties such as high specific strength and good corrosion resistance, and have broad application prospects. They are widely used in shipbuilding, marine engineering, aviation, aerospace, and chemical industries. Titanium alloy cylinders, as a typical structural form of pressure vessels, are usually formed using a rolling process. The following problems often arise during the rolling process of titanium alloy plates with a thickness of 20mm or more:

[0003] (1) During the rolling and forming process of the sheet metal, elastic-plastic deformation occurs, and the stress-strain distribution is relatively complex. The inner arc surface undergoes compressive deformation in the chord direction, and the outer arc surface undergoes tensile deformation in the chord direction. Generally, the stress-strain state in the thickness direction of the sheet metal is distributed symmetrically in opposite directions to the geometric neutral plane of the sheet metal, see Figure 1 .

[0004] (2) The inner arc surface area of ​​the plate undergoes significant compression deformation in the chord direction during the rolling process, resulting in the Baosinger effect, which leads to a significant reduction in tensile yield strength. The maximum reduction in local areas can reach more than 20%.

[0005] (3) Material strength is an important factor in ensuring the safe operation of the structure. The reduction in material strength caused by the plate forming process will bring hidden dangers to the safety and reliability of titanium alloy structures.

[0006] Publication No.: CN117816779A A method for room-temperature rolling of TC4 titanium alloy cylinders includes the following steps: S1, cutting and blanking; S2, chamfering the edges along the length direction; S3, pre-bending the head and tail; S4, multi-pass rolling; S5, straightening. However, the method described in this scheme is prone to significant compressive deformation of the inner arc surface area in the chord direction during the rolling process when rolling thick plates, resulting in the Bauschinger effect and a significant reduction in tensile yield strength.

[0007] Therefore, there is an urgent need to propose a new method for coating and rolling titanium alloy sheets to solve the problem of reduced tensile yield strength of titanium alloy sheets during the rolling and forming process in existing methods. Summary of the Invention

[0008] In view of this, the present invention aims to provide a method for forming titanium alloy sheet by wrapping and rolling, which solves the problem of reduced tensile yield strength of titanium alloy sheet in the existing method.

[0009] The technical solution of this invention is implemented as follows:

[0010] This invention discloses a method for coating and rolling titanium alloy sheets, comprising the following specific steps:

[0011] S1: Calculate the dimensions: Calculate the required cutting length and thickness of the rolled and coated plates based on the outer diameter and thickness of the cylinder;

[0012] S2: Material cutting and beveling: Complete the material cutting and process the welding bevel as required;

[0013] S3: Fixing the cladding material: Place the cladding material on top of the rolled material, align it around the edges, and then spot weld it in place;

[0014] S4: Pre-bending treatment: Press and pre-bend both ends of the composite board on a press;

[0015] S5: Rolling and shaping: Multiple plastic deformations are performed to achieve the rolling effect;

[0016] S6: Natural closing and adjustment: Under the pressure of the upper roller, the two ends of the board are crossed and overlapped, and the pressure of the upper roller is adjusted in time to achieve natural closing;

[0017] S7: Removal of cladding and welding: After removing the cladding material, grind the bevels at both ends of the cylinder and weld them together.

[0018] Furthermore, in step S1, the width of the covering material is the same as that of the rolled material, and the relationship between the cutting length L1 and thickness t1 of the material and the cutting length L2 and thickness t2 of the covering material is as follows:

[0019] L1=π×(Dt), t1=t;………………(1)

[0020] L2=π×(D-3t), t2=t;………………(2)

[0021] Where D is the outer diameter of the cylinder;

[0022] t is the thickness of the cylinder.

[0023] Furthermore, the thickness t of the sheet material is 20mm or more.

[0024] Furthermore, in step S1, the covering material is a pure titanium sheet.

[0025] Furthermore, in step S2, water jet cutting is used to complete the rolling and wrapping of the sheet material.

[0026] Furthermore, in step S4, the pre-bending radius R = D ÷ 2 — 2 × t2;

[0027] Where: D is the outer diameter of the cylinder;

[0028] t2 is the thickness of the cladding material.

[0029] Furthermore, in step S4, the pre-bending length is not less than the maximum straight edge length of the rolling mill.

[0030] Furthermore, in step S5, after the upper and lower rollers have made full contact with the sheet material, the pressure is set, and the plastic deformation effect is achieved through multiple rolling and pressing cycles, with the pressure amount decreasing gradually in each cycle.

[0031] Furthermore, in step S6, the two ends are made to overlap under the pressure of the upper roller. The amount of pressure of the upper roller is adjusted according to the rebound amount after the plate is unloaded. After unloading, the two ends of the cylinder naturally close together.

[0032] Furthermore, in step S7, the tensile yield strength of the inner arc surface after rolling and forming is increased by more than 30%.

[0033] Compared with the prior art, the method for forming titanium alloy sheet by coating and rolling according to the present invention has the following advantages:

[0034] 1. This invention uses a reasonable arrangement of the covering plate to roll the cylinder into shape, thereby changing the stress-strain state during the rolling process. This ensures that the chord direction of the cylinder is not subjected to compressive stress during rolling, and that no compressive deformation occurs in the chord direction, thus avoiding a decrease in the chord tensile yield strength.

[0035] 2. This invention allows the use of low-cost pure titanium plates for coating, and the plates can be reused multiple times. The operation is simple and the cost is low. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0037] Figure 1 This is a schematic diagram of the stress during the rolling process of titanium alloy sheet;

[0038] Figure 2 This is a schematic diagram showing the stress during the coating and rolling process of titanium alloy sheet. Detailed Implementation

[0039] To make the technical means and objectives and effects of the present invention easier to understand, the embodiments of the present invention will be described in detail below with reference to specific illustrations.

[0040] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "lateral," "longitudinal," and "center," are only used to explain the relative positional relationships and connections between components in a specific state. They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0041] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0043] like Figure 1-2 As shown, this invention discloses a method for forming a titanium alloy sheet by coating and rolling, including the following specific steps:

[0044] S1: Calculate the dimensions: Calculate the required cutting length and thickness of the rolled and coated plates based on the outer diameter and thickness of the cylinder;

[0045] Calculate the required cutting length L1 and thickness t1 of the rolled sheet based on the outer diameter D and thickness t of the cylinder, as well as the cutting length L2 and thickness t2 of the covering sheet, to ensure that the dimensions of the materials used are accurate and meet the requirements of subsequent processing, thus affecting the stress and strain distribution during the rolling process of the titanium alloy sheet.

[0046] S2: Material cutting and beveling: Complete the material cutting and process the welding bevel as required;

[0047] After the sheet metal is cut, the welding bevels at both ends of the rolled sheet metal are processed according to the welding process requirements to ensure that the cut edges are smooth and burr-free, thereby improving the quality of subsequent welding. The design of the bevels helps to ensure welding strength and sealing, improve production efficiency and product quality, and reduce the amount of subsequent processing work.

[0048] S3: Fixing the cladding material: Place the cladding material on top of the rolled material, align it around the edges, and then spot weld it in place;

[0049] This ensures that the two types of sheets are tightly bonded, preventing displacement during subsequent processing, avoiding deformation caused by insecure fixing and asymmetrical stress during rolling, and improving forming accuracy.

[0050] S4: Pre-bending treatment: Press and pre-bend both ends of the composite board on a press;

[0051] The mold is used on the press to press and pre-bend both ends of the composite sheet. The inner radius of the pre-bend is usually determined according to the set radius. This pre-forms a certain curved shape, which is convenient for subsequent rolling and forming, reduces the operation difficulty when rolling directly, and improves the forming quality.

[0052] S5: Rolling and shaping: Multiple plastic deformations are performed to achieve the rolling effect;

[0053] The pre-bent sheet is hoisted to the processing station, and a suitable downward pressure is set and repeated multiple times to achieve the plastic deformation effect. Through repeated plastic deformation, the sheet gradually approaches the required cylindrical shape, ensuring uniform deformation of the sheet and avoiding excessive stress concentration in certain areas.

[0054] S6: Natural closing and adjustment: Under the pressure of the upper roller, the two ends of the board are crossed and overlapped, and the pressure of the upper roller is adjusted in time to achieve natural closing.

[0055] Under the pressure of the upper roller, the two ends of the plate are crossed and overlapped. The pressure of the upper roller is adjusted in time according to the rebound after unloading to achieve natural closing. This ensures that the two ends of the cylinder can be perfectly connected, avoids structural damage caused by forced closing, improves the quality and safety of the finished product, and reduces the workload of later repairs.

[0056] S7: Removal of cladding and welding: After removing the cladding plate, grind the bevels at both ends of the cylinder and weld them together;

[0057] After removing the cladding plate, grind the bevels at both ends of the cylinder to remove the oxide layer, and then weld the connection. This removes surface impurities, ensures welding quality, enhances the mechanical properties and appearance of the final product, and extends its service life.

[0058] This setup involves rationally arranging the covering plates for cylinder rolling, altering the stress-strain state during cylinder rolling, ensuring that the chord direction is not subjected to compressive stress during rolling, and that no compressive deformation occurs in the chord direction, thus avoiding a decrease in chord tensile yield strength.

[0059] Specifically, in step S1, the width of the covering material is the same as that of the rolled material, and the relationship between the cutting length L1 and thickness t1 of the material and the cutting length L2 and thickness t2 of the covering material is as follows:

[0060] L1=π×(Dt), t1=t;………………(1)

[0061] L2=π×(D-3t), t2=t;………………(2)

[0062] Where D is the outer diameter of the cylinder;

[0063] t is the thickness of the cylinder.

[0064] By accurately calculating the blanking dimensions, it is ensured that the final formed cylinder meets the design requirements for outer diameter and thickness. Reasonable calculation of blanking dimensions helps to minimize material waste while ensuring sufficient material for manufacturing high-quality cylinders. Determining the blanking dimensions through specific calculation methods can effectively control the deformation and internal stress distribution of the sheet metal during the rolling process, avoiding additional stress concentration or uneven deformation caused by improper dimensions. This prevents the cylinder from being subjected to compressive stress in the chord direction during rolling, and prevents chordal compression deformation during rolling, thus avoiding a decrease in chordal tensile yield strength.

[0065] This setting reduces trial and error time. Directly cutting materials according to the calculation results can significantly improve work efficiency, reduce the extra adjustment work caused by unsuitable size, help ensure the accuracy of the cylinder shape, and ensure its mechanical properties, thereby improving the overall reliability and service life of the product.

[0066] Preferably, the thickness t of the sheet material is 20mm or more.

[0067] Specifically, in step S1, the covering material can be a lower-cost pure titanium material.

[0068] Using lower-cost pure titanium sheets instead of higher-cost titanium alloy sheets can significantly reduce raw material costs without affecting the performance of the final product. It can also improve the stress-strain distribution during the rolling process and prevent a decrease in tensile yield strength.

[0069] Specifically, in step S2, water jet cutting is used to complete the cutting of the rolled sheet and the cladding sheet.

[0070] Waterjet cutting technology can achieve very high cutting precision, ensuring the dimensional accuracy of titanium alloy sheets and clad sheets. As a cold cutting process, waterjet cutting produces almost no heat-affected zone (HAZ), thus avoiding problems such as material deformation, hardening, or other changes in physical properties due to heat. It can provide extremely smooth cutting edges, reducing the need for subsequent processing, such as grinding or finishing, and directly improving production efficiency.

[0071] This setup reduces the time and workload of subsequent processing, helping to speed up the entire manufacturing process. The cutting process mainly uses water and abrasives, making it more environmentally friendly and particularly suitable for making parts with complex shapes or special requirements.

[0072] Specifically, in step S4, the pre-bending radius R = D ÷ 2 - 2 × t2;

[0073] Where: D is the outer diameter of the cylinder;

[0074] t2 is the thickness of the cladding material.

[0075] By setting the pre-bending radius R, the sheet material can be given a preliminary bending shape before formal rolling, which helps to better achieve the required cylindrical shape during subsequent rolling. This effectively reduces the risk of uneven internal stress distribution and even cracks in the material during large-angle rolling, making the entire rolling process smoother.

[0076] This setting can reduce material damage caused by stress concentration during the rolling process, such as cracks or delamination, and help achieve a more uniform and accurate rolling effect, thereby improving the forming quality and dimensional accuracy of the final product. The pre-bending radius calculated by the formula ensures that the pre-bending parameters are consistent for each production run, which helps maintain the consistency and stability of product quality.

[0077] Specifically, in step S4, the pre-bending length should not be less than the maximum straight edge length of the plate rolling equipment.

[0078] By ensuring that the pre-bending length is not less than the maximum straight edge length of the plate rolling machine, sufficient initial curvature can be guaranteed when the plate enters the plate rolling machine. This allows for a more even distribution of stress within the plate, avoiding stress concentration caused by excessive local deformation. Consequently, the risk of material damage is reduced, which helps improve the forming accuracy of the final cylinder and makes the size and shape of the finished product more in line with design requirements.

[0079] This setup simplifies the operating process, improves work efficiency, effectively disperses various forces generated during the rolling process of the sheet material, reduces the possibility of cracks or other forms of damage caused by improper stress, helps maintain consistency and stability in the production process, and ensures that the quality of each batch of products meets the same high standards.

[0080] Specifically, in step S5, after the upper and lower rollers have made full contact with the sheet material, the pressure is set, and the plastic deformation effect is achieved through multiple rolling and pressing cycles, with the pressure amount decreasing gradually in each cycle.

[0081] By rolling the material multiple times and gradually adjusting the pressure, the material can be guided into the desired shape. The initial larger pressure helps to quickly initiate the plastic deformation process, while the subsequent gradually decreasing pressure ensures precise forming and more evenly distributes the stress inside the sheet. This avoids excessive deformation or cracking in local areas due to sudden excessive pressure. This progressive pressure strategy reduces the impact on the material and lowers the risk of surface cracks, delamination, or other forms of damage.

[0082] This setting allows operators to fine-tune the pressure applied each time based on different material thicknesses and diameters, adapting to the manufacturing needs of products of different specifications to achieve optimal results and ensure that the final product has good mechanical properties.

[0083] Specifically, in step S6, the two ends are overlapped under the pressure of the upper roller. The amount of pressure of the upper roller is adjusted in time according to the rebound amount after the plate is unloaded. After unloading, the two ends of the cylinder naturally close together.

[0084] By overlapping the two ends under the pressure of the upper roller, the two ends of the cylinder can be precisely aligned, avoiding joint problems caused by size mismatch. By observing and measuring the rebound amount after the plates are unloaded, the pressure of the upper roller can be adjusted according to the actual situation to compensate for this rebound effect, thereby ensuring the quality of the final joint. The joint will be naturally joined, rather than forcibly pressing the two ends together, avoiding structural damage or deformation caused by excessive force.

[0085] This design ensures a perfect fit between the two ends of the cylinder, forming a seamless connection. This improves the overall quality and appearance of the finished product, reduces the need for additional processes such as later repairs and polishing, saves time and costs, and significantly enhances its mechanical properties, such as compressive strength and corrosion resistance, thereby extending the product's service life.

[0086] Specifically, in step S7, the tensile yield strength of the inner arc surface after rolling and forming is increased by more than 30%.

[0087] By using a titanium alloy sheet cladding and rolling forming method, the tensile yield strength of the inner arc surface after rolling and forming is increased by more than 30%. This not only significantly enhances the mechanical properties and structural safety of the final product, but also brings greater design flexibility, while helping to reduce maintenance costs and improve market competitiveness.

[0088] Example 1

[0089] The cylinder material is TC4 titanium alloy, with an outer diameter of 1500 mm, a length of 2000 mm, and a thickness of 20 mm. The rolling process includes the following steps:

[0090] 1) Based on the above cylinder specifications, the calculated dimensions for the rolled sheet are 4649mm × 2000mm × 20mm, and the dimensions for the covered sheet are 4524mm × 2000mm × 20mm.

[0091] 2) Water jet cutting is used for material preparation, and welding bevels are machined according to the drawing requirements;

[0092] 3) The covering sheet is placed on top of the rolled sheet, and the four sides should be completely aligned and fixed by spot welding around the edges;

[0093] 4) The fixed covering sheet and the two ends of the rolled sheet are pre-bent by mold on a large press. The inner radius of the pre-bending is 710mm and the pre-bending length is ≥250mm.

[0094] 5) Hoist the pre-bent sheet to the plate rolling machine, align it, and start the upper roller to press down. After the upper and lower rollers are in full contact with the sheet, set the pressing amount and start the lower roller to rotate. Repeat the pressing to achieve the plastic deformation effect.

[0095] 6) Roll the sheet material processed in step 5) into a cylinder and close the ends. Under the pressure of the upper roller, make the two ends overlap. Adjust the pressure of the upper roller in time according to the rebound amount after the sheet material is unloaded. After unloading, the two ends of the cylinder will naturally close.

[0096] 7) Grind the bevels at both ends of the cylinder after the joint is closed to remove the oxide layer, and then weld the longitudinal seam of the cylinder.

[0097] The chordal tensile yield strength of the inner arc surface was measured on the cylinder and compared with the strength of the original plate. The results are shown in Table 1.

[0098] Example 2

[0099] The cylinder material is TC4 titanium alloy, with an outer diameter of 2000 mm, a length of 2000 mm, and a thickness of 25 mm. The rolling process includes the following steps:

[0100] 1) Based on the above cylinder specifications, the calculated dimensions for the rolled sheet are 6204mm × 2000mm × 25mm, and the dimensions for the covered sheet are 6.47mm × 2000mm × 25mm.

[0101] 2) Water jet cutting is used for material preparation, and welding bevels are machined according to the drawing requirements;

[0102] 3) The covering sheet is placed on the rolled sheet, and the four sides should be completely aligned and fixed by spot welding.

[0103] 4) The fixed covering sheet and the two ends of the rolled sheet are pre-bent by mold on a large press. The inner radius of the pre-bending is 850mm and the pre-bending length is ≥300mm.

[0104] 5) Hoist the pre-bent sheet to the plate rolling machine, align it, and start the upper roller to press down. After the upper and lower rollers are in full contact with the sheet, set the pressing amount and start the lower roller to rotate. Repeat the pressing to achieve the plastic deformation effect.

[0105] 6) Roll the sheet material processed in step 5) into a cylinder and close the ends. Under the pressure of the upper roller, make the two ends overlap. Adjust the pressure of the upper roller in time according to the rebound amount after the sheet material is unloaded. After unloading, the two ends of the cylinder will naturally close.

[0106] 7) Grind the bevels at both ends of the cylinder after the joint is closed to remove the oxide layer, and then weld the longitudinal seam of the cylinder.

[0107] The chordal tensile yield strength of the inner arc surface was measured on the cylinder and compared with the strength of the original plate. The results are shown in Table 1.

[0108] Table 1. Tensile yield strength test results after the cylinder is rolled and formed.

[0109]

[0110] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for forming a titanium alloy sheet by coating and rolling, characterized in that, The specific steps are as follows: S1: Calculate the dimensions: Calculate the required cutting length and thickness of the rolled and coated plates based on the outer diameter and thickness of the cylinder; S2: Cutting and beveling: Cutting the rolled and clad sheets and processing the welding bevels as required; S3: Fixing the cladding material: Place the cladding material on top of the rolled material, align it around the edges, and then spot weld it in place; S4: Pre-bending treatment: Press and pre-bend both ends of the composite board on a press; S5: Rolling and shaping: Multiple plastic deformations are performed to achieve the rolling effect; S6: Natural closing and adjustment: Under the pressure of the upper roller, make the two ends of the combined plate overlap. According to the rebound amount after the combined plate is unloaded, adjust the pressure of the upper roller. After unloading, the two ends of the cylinder will naturally close. S7: Removal of cladding and welding: After removing the cladding material, grind the bevels at both ends of the cylinder and weld them together.

2. The method for forming titanium alloy sheet by coating and rolling according to claim 1, characterized in that, In step S1, the width of the covering material is the same as that of the rolled material. The relationship between the cutting length L1 and thickness t1 of the rolled material and the cutting length L2 and thickness t2 of the covering material is as follows: L1=π×(D-t), t1=t;………………(1) L2=π×(D-3t), t2=t;………………(2) Where D is the outer diameter of the cylinder; t is the thickness of the cylinder.

3. The method for forming titanium alloy sheet by coating and rolling according to claim 2, characterized in that, The thickness t of the cylinder is 20mm or more.

4. The method for forming titanium alloy sheet by coating and rolling according to claim 1, characterized in that, In step S1, the covering material is a pure titanium sheet.

5. The method for forming titanium alloy sheet by coating and rolling according to claim 1, characterized in that, In step S2, water jet cutting is used to complete the cutting of the rolled sheet and the wrapped sheet.

6. The method for forming titanium alloy sheet by coating and rolling according to claim 2, characterized in that, In step S4, the pre-bending radius R = D ÷ 2 - 2 × t2; Where: D is the outer diameter of the cylinder; t2 is the thickness of the cladding material.

7. The method for forming titanium alloy sheet by coating and rolling according to claim 1, characterized in that, In step S4, the pre-bending length is not less than the maximum straight edge length of the rolling equipment.

8. The method for forming titanium alloy sheet by coating and rolling according to claim 1, characterized in that, In step S5, after the upper and lower rollers have made full contact with the combined sheet material, the pressure is set, and the plastic deformation effect is achieved through multiple rolling and pressing cycles, with the pressure amount decreasing gradually in each cycle.

9. The method for forming titanium alloy sheet by coating and rolling according to claim 1, characterized in that, In step S7, the tensile yield strength of the inner arc surface after rolling and forming is increased by more than 30%.

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