A method for forming thick steel plates by bending

Abstract

This invention relates to the field of steel plate bending technology, specifically to a method for bending and forming thick steel plates, comprising the following steps: obtaining design parameters for the forming state of the steel plate, determining the steel plate material selection and bending process parameters; determining whether the bending line is a positive pressure bending line or an interference bending line, and marking it on the steel plate; prioritizing bending along the positive pressure bending line according to the bending process parameters, and finally bending along the interference bending line; when bending along the interference bending line of the steel plate, a first bending is performed until the steel plate bends to the point where the interference end of the steel plate abuts against the lifting plate, then the upper die and the steel plate are lifted, the lower die support gap is adjusted, and then the steel plate is lowered to abut against the two lower dies for a second bending operation. This invention adopts a secondary bending method combining positive pressure and asymmetric bending for the interference bending line, solving the problem of bending and welding segmented steel plates separately, which is beneficial to improving the performance of the formed steel plate.

Description

Technical Field

[0001] This invention relates to the field of steel plate bending technology, and in particular to a method for bending and forming thick steel plates. Background Technology

[0002] Steel plates are conventional semi-finished metal products that require certain processing to meet actual usage requirements. Common processing methods include cutting, welding, punching, bending, press bending, leveling and shaping, ribbed forming, flanging, grinding, and cutting. Among these, the pressing bending process is mainly used for deformation processing of thick plates with a thickness greater than 20mm. The press is large in size, and the upper die is usually set vertically, with the lower die located directly below the upper die. The upper die moves up and down in the vertical plane, pressing the steel plate to bend it to an appropriate angle. For steel plates with complex shapes, multiple pressing operations are usually required.

[0003] In practical applications, when bending steel plates whose two ends are close together or even close to closed after forming, such as irregular beams, curved beams, box columns, irregular columns, and some irregular components in building steel structures, the position of the final bending line is usually directly opposite to the two ends of the formed steel plate. However, for some workpieces, the position of the final bending line is not directly opposite to the two ends of the formed steel plate. In this case, when the upper mold presses down to a certain extent, one end of the steel plate will interfere with the lifting plate connected to the upper mold and cannot be pressed down further.

[0004] In existing technologies, when the position of the final bending line is not directly opposite to the gap between the two ends of the formed steel plate, causing the upper die to be unable to press properly, the steel plate is usually divided into several parts, i.e., two steel plates are used, each plate is pressed into shape separately, and then the two formed steel plates are welded together. However, the composition of the welding material and the process used for welding are different from the steel plate preparation process. The main difference lies in the metallographic structure of the weld and the steel plate. The high temperature of welding will affect the metallographic structure of the area near the weld of the steel plate, which will have a certain adverse effect on the structural strength, corrosion resistance, weather resistance and other properties. Therefore, it is necessary to minimize the number of welds in the formed steel plate and optimize the steel plate bending process to improve the performance and quality of the formed steel plate. Summary of the Invention

[0005] To address the aforementioned shortcomings, the present invention aims to provide a method for forming thick steel plates by pressing and bending, thereby solving the technical problem in the prior art where the position of the final bending line is not directly opposite to the gap between the two ends of the formed steel plate, requiring the two steel plates to be pressed and formed separately before welding, which affects the performance and quality of the formed steel plate.

[0006] To achieve the above objectives, the present invention provides a method for forming thick steel plates by bending, comprising the following steps:

[0007] Obtain the design parameters for the steel plate forming state, determine the steel plate material selection and bending process parameters, including at least the number and position of bending lines, bending radius, lower die support gap, bending angle and bending depth corresponding to each bending line;

[0008] Determine whether the bending line is a positive pressure bending line or an interference bending line, and mark it on the steel plate. Prioritize bending along the positive pressure bending line according to the bending process parameters, and finally bend along the interference bending line.

[0009] When bending along the interference bending line of the steel plate, first bend it once until the steel plate bends to the point where the interference end of the steel plate abuts against the lifting plate. Then lift the upper die and the steel plate, adjust the support gap of the lower die, and then let the steel plate fall down to abut against the two lower dies for a second bending operation.

[0010] As a further improvement, the method for adjusting the lower die support gap after one bending along the steel plate interference bending line is as follows:

[0011] Establish a two-dimensional model of the steel plate under bending conditions, including at least a first bending state diagram and a second bending state diagram along the interference bending line, and calculate the deflection angle of the steel plate in the two model diagrams;

[0012] After bending the steel plate once along the interference bending line, rotate the steel plate with the interference bending line as the center and according to the deflection angle so that the interference end deviates from the lifting plate. Adjust the position of one side of the lower die, calculate the distance between the steel plate and the lower die when it falls vertically, and calculate the position of the support point of the other lower die.

[0013] Using the vertical plane containing the interference curve as a reference, calculate the distance between it and the support points of the two lower molds, and adjust the positions of the two lower molds accordingly.

[0014] As a further improvement, the primary bending depth and total bending depth along the interference bending line are measured from the primary bending state diagram and the secondary bending state diagram. The difference between the two is calculated as the secondary positive pressure depth. Then, the secondary positive pressure depth is corrected by the deflection angle to obtain the secondary bending depth. The formula for calculating the secondary bending depth is as follows:

[0015] ,

[0016] Where H is the total bending depth of the interference bending line of the formed steel plate, in mm; The bending depth along the interference bending line of the steel plate is measured in mm. The secondary bending depth along the interference bending line of the steel plate is expressed in mm. This represents the deflection angle of the steel plate.

[0017] As a further improvement, if the actual bending depth during the bending operation deviates from the theoretical bending depth calculated above, the actual bending depth value is substituted into the above formula for calculating the secondary bending depth to correct the calculation of the secondary bending depth.

[0018] As a further improvement, for cases where the angle deviation after bending does not reach the target angle and for cases where bending is performed twice along the interference bending line to the interference end and still does not reach the target angle, a pressure mechanism and bending die are used to press and compensate the steel plate. The shape, specifications and bending angle of the bending die are matched with the shape, size and bending angle of both sides of the steel plate correction part.

[0019] For the formed steel plate after compression compensation, a fixed support structure is used to fix the angle.

[0020] Due to the adoption of the above technical solution, the beneficial technical effects of the present invention are as follows:

[0021] The steel plate is bent first along the positive pressure bending line, and then along the interference bending line. The interference bending line adopts a two-stage bending method that combines positive pressure and asymmetric bending. This solves the problem that the existing method of bending the steel plate separately and then welding it is not possible to perform interference bending. This reduces welding costs and reduces the impact of welding process and weld on the performance of the steel plate. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the steel plate forming process;

[0024] Figure 3 This is a schematic diagram of the positive pressure state of the formed steel plate;

[0025] Figure 4 This is a schematic diagram of the deflection state of the formed steel plate;

[0026] Figure 5 This is a schematic diagram of the curved lines marking the steel plate;

[0027] Figure 6 This is a schematic diagram of the bending state of the steel plate near both ends;

[0028] Figure 7 This is a schematic diagram of the state before the interference bending operation;

[0029] Figure 8 This is a schematic diagram of the state of the interference curve after one bending.

[0030] Figure 9 yes Figure 8 A schematic diagram of the structure after the steel plate is deflected;

[0031] Figure 10 This is a schematic diagram showing the positions of the two lower molds;

[0032] Figure 11 This is a schematic diagram showing the connection between the falling steel plate and the lower mold;

[0033] Figure 12 This is a schematic diagram showing the state of the steel plate after a second bending.

[0034] Figure 13 This is a schematic diagram of the pressure mechanism.

[0035] Wherein: 1-positive pressure bending line, 2-interference bending line, 3-upper mold, 4-lifting plate, 5-interference end, 6-pressure mechanism, 7-bending mold. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] This embodiment provides a method for forming thick steel plates by bending, such as... Figure 1 As shown, it includes the following steps:

[0038] To obtain the design parameters for the steel plate forming state, determine the steel plate material selection and bending process parameters. This includes at least the number and location of bending lines, bending radius, lower die support clearance, bending angle and bending depth corresponding to each bending line. Specifically, a two-dimensional model of the steel plate forming state can be created, such as... Figure 2 The image shows a fully formed steel plate with a total of 8 bending lines. The number of bending lines, the bending angle and bending depth corresponding to each bending line are calculated. The bending lines are the contact lines between the upper die 3 and the surface of the steel plate during bending.

[0039] Determine whether the curved line is a positive pressure curved line 1 or an interference curved line 2. Figure 2 , Figure 3 and Figure 4 The bending lines at the opposite ends of the gap between the two ends of the steel plate are as follows: the bending line of the first bending operation is the positive pressure bending line 1, and the bending line of the subsequent bending operation is the interference bending line 2. Figure 6 and Figure 7 As shown, one curved line is designated as interference curved line 2, and the remaining curved lines are designated as positive pressure curved lines 1, and are marked on the steel plate, as detailed below. Figure 5As shown, bending is performed first along the positive pressure bending line 1 according to the bending process parameters, and finally along the interference bending line 2. Here, the positive pressure bending line 1 is the bending line in which the end of the steel plate will not interfere with the lifting plate during the bending process of the steel plate. The bending angle can be reached by applying positive vertical pressure. When bending, the end of the steel plate will approach the lifting plate 4 of the upper mold 3 and interfere with the lifting plate 4, and thus cannot reach the bending angle.

[0040] When bending along the interference bending line 2 of the steel plate, perform a single bending motion until the steel plate bends to the point where the interference end 5 of the steel plate abuts against the lifting plate 4, such as... Figure 7 and 8 As shown, the upper die 3 and the steel plate are then raised, the lower die support gap is adjusted, and then the steel plate is lowered until it abuts against the two lower dies for a secondary bending operation, as shown. Figure 11 and Figure 12 As shown, during both bending processes, the upper mold 3 moves vertically up and down.

[0041] The steel plate bending forming method provided in this embodiment prioritizes bending along the positive pressure bending line 1 and finally bending along the interference bending line 2. The interference bending line 2 adopts a secondary bending method that combines vertical positive pressure and asymmetric bending, which solves the problem that the existing method of bending steel plates separately and then welding is not possible, thus reducing welding costs and minimizing the impact of welding process and weld on the performance of steel plates.

[0042] Before actual bending, based on the selected steel plate material and thickness, obtain the corresponding parameters such as yield strength, elastic modulus, neutral layer position, and bending radius. Perform a test press using the equipment to verify and correct these parameters. Further test presses are conducted to confirm the actual bending depth of each bend. For example, for a 49mm thick Q235 steel plate, the straightness (the length of the steel plate along the bending line in mm) divided by 1000 should be less than or equal to 12mm, with a length tolerance of 0-25mm. The bending angle should reach 135 degrees, the bending radius should be less than or equal to 5 times the plate thickness, and the neutral layer coefficient should be 0.2. A total lower die support gap of 400mm can be selected.

[0043] The process of pressure testing to verify the actual pressure depth of each bend includes selecting test plates of the same material thickness, marking the bends, conducting multiple pressure tests on different bends, recording the actual pressure depth and bending angle, and analyzing the influence of springback on different bends to correct the actual pressure depth. Specifically, linear regression can be used for analysis.

[0044] In this embodiment, after bending along the interference bending line 2 of the steel plate once, the steel plate needs to be lifted, and the lower die support gap L needs to be adjusted. The specific adjustment method is as follows:

[0045] Establish a two-dimensional model of the steel plate under bending conditions, including at least a primary bending state diagram and a secondary bending state diagram along the interference bending line 2, and calculate the deflection angle of the steel plate in the two model diagrams. See details Figure 3 and Figure 4 During the bending process, the interference bending line 2 is always within the vertical plane pressed down by the upper die 3. The deflection angle is obtained by measuring the angle between the connecting line of the interference end 5 and the interference bending line 2 in the two figures. ;

[0046] After bending and lifting the steel plate along the interference bending line 2, with the interference bending line 2 as the center, according to the aforementioned deflection angle... Rotate the steel plate, as Figure 9 As shown, the interference end 5 is deviated from the lifting plate 4, and the position of one of the lower dies is adjusted. Specifically, the position of one lower die is determined by adjusting the steel plate material thickness, bending process parameters, and bending equipment parameters. The distance between the steel plate and the lower die when it falls vertically is calculated. Since the supporting surfaces of the two lower dies on the steel plate are horizontal, the support point position of the other lower die is determined and calculated accordingly. Figure 10 As shown;

[0047] Using the vertical plane containing the interference bending line 2 as a reference, calculate the distance between it and the support points of the two lower molds, and adjust the positions of the two lower molds accordingly.

[0048] Typically, the distance between the lower die support point on one side of the interference end 5 and the interference bending line 2 increases, while the distance between the lower die support point on the other side and the interference bending line 2 decreases, resulting in an overall increase in the gap between the two lower die supports. In practice, for a 49mm thick Q235 steel plate, the initial total lower die support gap is set at 400mm, with 200mm gaps on both sides. After one pressing cycle, the gap can be adjusted to 300mm on one side and 159mm on the other. This lower die support gap is determined based on the specific bending equipment and bending process parameters. In reality, due to limitations in equipment and other factors, the lower die position cannot be arbitrarily adjusted. Different bending equipment may correspond to different lower die support gaps. This is only used to illustrate a specific embodiment and is not intended as a specific limitation. Corrections can be made when there are errors in actual operation, with the aim of providing stable support for the steel plate.

[0049] In this embodiment, the primary bending depth and total bending depth of interference bending line 2 are measured from the primary bending state diagram and the secondary bending state diagram along the interference bending line 2. The difference between the two is calculated as the secondary positive bending depth. Then, the secondary positive bending depth is corrected by the deflection angle to obtain the secondary bending depth. The formula for calculating the secondary bending depth is as follows:

[0050] ,

[0051] Where H is the total bending depth of the interference bending line 2 of the formed steel plate, that is, the distance between the bending line and the line connecting the two adjacent bending lines after the second bending, in mm. The bending depth along the interference bending line 2 of the steel plate is the distance between the interference bending line 2 and the lower die support surface when the steel plate is bent to the interference point. The unit is mm. The second bending depth along the interference bending line 2 of the steel plate is the distance between the interference bending line 2 and the lower mold support plane after the second bending, in mm. This represents the deflection angle of the steel plate.

[0052] In this embodiment, if the actual bending depth deviates from the theoretical bending depth calculated above during the bending operation, the actual bending depth value is substituted into the calculation formula for the secondary bending depth to correct the calculation of the secondary bending depth.

[0053] In addition, for cases where the angle deviation after bending does not reach the target angle, and for cases where bending is performed twice along the interference bending line 2 to the interference end 5 and still does not reach the target angle due to interference with the lifting plate 4, the pressure mechanism 6 and bending die 7 are used to press and compensate the steel plate. The shape, specifications and bending angle of the bending die 7 are matched with the shape, size and bending angle of both sides of the steel plate correction part. The bending die 7 can protect the bending part that does not need to be corrected, and prevent it from being incorrectly corrected.

[0054] For the formed steel plate after compression compensation, a fixed support structure is used to fix the angle, stabilize the forming state of the steel plate, and prevent the steel plate from deforming due to gravity and its own elasticity.

[0055] Specifically, such as Figure 13 As shown, the pressure mechanism 6 can be a frame structure, with the forming steel plate passing through the frame and the bending mold 7 installed on the frame.

[0056] During actual bending, situations may arise where the distance between the bending line and the end of the steel plate is small when the plate is in its formed state. This distance may even be less than half the gap of the lower die support, making bending impossible. If the lower die support gap is reduced, a larger downward pressure may be required. Therefore, for cases where the distance between the bending line and the end of the steel plate is small, a pressure head allowance is reserved at both ends of the steel plate. The distance between the pressure head allowance and the bending line near the end should ensure that the end of the steel plate remains outside the lower die support point after the bending line reaches the bending angle. If welding is required at the end of the steel plate after bending, a bevel allowance must also be reserved according to the parameters of the welding bevel.

[0057] In this embodiment, for the secondary bending operation of the interference bending line 2, during the test calibration, multiple tests are also required to record the actual pressing depth and bending angle, and analyze the influence of springback factors at different pressing depths and bending angles in order to correct the actual pressing depth. Linear regression method can also be used for analysis.

[0058] In practical use, this embodiment is suitable for bending thick steel plates. The bending angle does not require extremely high precision. The deflection angle is usually around 10 degrees, and the maximum is no more than 15 degrees. The angle is relatively small. Of course, for high-precision bending requirements, the bending die 7 can be used to press and compensate the steel plate after bending to achieve extremely high bending accuracy.

[0059] The shaped steel plate prepared by the method of this embodiment, after being joined and welded by the bending mold 7 and the pressure mechanism 6, fully meets the usage requirements after testing. The bevel adopts a double V-shaped bevel, with the inner bevel angle being 70 degrees and the outer bevel angle being 50 degrees. The inner bevel depth is 8mm, the blunt edge is 0-2mm, and the root gap is 0-3mm. During welding, gas shielded welding is used for the root pass first, followed by submerged arc welding.

[0060] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art should be able to make corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method of press bending a steel plate girders, characterized by, Includes the following steps: Obtain the design parameters for the steel plate forming state, determine the steel plate material selection and bending process parameters, including at least the number and position of bending lines, bending radius, lower die support gap, bending angle and bending depth corresponding to each bending line; Determine whether the bending line is a positive pressure bending line or an interference bending line, and mark it on the steel plate. Prioritize bending along the positive pressure bending line according to the bending process parameters, and finally bend along the interference bending line. When bending along the interference bending line of the steel plate, first bend it once until the steel plate bends to the point where the interference end of the steel plate abuts against the lifting plate. Then lift the upper die and the steel plate, adjust the support gap of the lower die, and then let the steel plate fall down to abut against the two lower dies for a second bending operation. The method for adjusting the gap of the lower die support after bending along the interference bending line of the steel plate is as follows: Establish a two-dimensional model of the steel plate under bending conditions, including at least a first bending state diagram and a second bending state diagram along the interference bending line, and calculate the deflection angle of the steel plate in the two model diagrams; After bending the steel plate once along the interference bending line, rotate the steel plate with the interference bending line as the center and according to the deflection angle so that the interference end deviates from the lifting plate. Adjust the position of one side of the lower die, calculate the distance between the steel plate and the lower die when it falls vertically, and calculate the position of the support point of the other lower die. Using the vertical plane containing the interference curve as a reference, calculate the distance between it and the support points of the two lower molds, and adjust the positions of the two lower molds accordingly.

2. The steel plate thick plate press bending forming method according to claim 1, characterized by, From the primary and secondary bending state diagrams along the interference bending line, the primary bending depth and total bending depth are measured. The difference between the two is calculated as the secondary positive pressure depth. Then, the secondary positive pressure depth is corrected using the deflection angle to obtain the secondary bending depth. The formula for calculating the secondary bending depth is as follows: ， Where H is the total bending depth of the interference bending line of the formed steel plate, in mm; The bending depth along the interference bending line of the steel plate is measured in mm. The secondary bending depth along the interference bending line of the steel plate is expressed in mm. This represents the deflection angle of the steel plate.

3. The method according to claim 2, wherein If the actual bending depth deviates from the theoretical bending depth calculated above during the bending operation, the actual bending depth value should be substituted into the calculation formula for the secondary bending depth to correct the calculation of the secondary bending depth.

4. The method according to any one of claims 1 to 3, wherein For cases where the angle deviation after bending does not reach the target angle, and for cases where bending is performed twice along the interference bending line to the interference end and still does not reach the target angle due to interference with the lifting plate, a pressure mechanism and bending die are used to press and compensate the steel plate. The shape, specifications and bending angle of the bending die are matched with the shape, size and bending angle of both sides of the steel plate correction part. For the formed steel plate after compression compensation, a fixed support structure is used to fix the angle.

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