JPS6317528B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting distortion in a metal sheet using a stretcher leveler, and particularly to a method for correcting distortion in a metal sheet by an effective tensile operation regardless of the state of distortion existing in the metal sheet. This provides a corrective method.

The metal sheet (original plate) obtained by cutting a metal strip or the like into a predetermined length has distortions that have been received during the manufacturing process, and as a result, the metal sheet has a large depression in the center. In other words, it has a bowl-shaped shape in which the edges of the four circumferences are warped (belly elongation), or one or both sides are uneven in the length direction (edge elongation). It may happen.

A stretcher leveler has been known as a device that corrects and flattens the unevenness caused by distortion of a metal sheet, and it usually straightens the metal sheet in the width direction at both ends of the sheet (longitudinal direction). The strain is corrected by clamping and restraining the plate with a clamper, applying a predetermined tension operation in the longitudinal direction of the plate, and then releasing the clamper.

By the way, it is known that the more a strained metal sheet is stretched, the more the degree of strain is improved. In the case of aluminum material, if it is stretched by more than 0.6% compared to the length of the original plate, strain marks will occur near the clamped part of the aluminum sheet and the product value will be lost. Therefore, the tensile elongation is set at an upper limit of about 0.6%. Under such circumstances, for thin plates with a thickness of about 3.0 mm or less, if the distortion of the original plate is due to edge elongation, it can be corrected to a relatively flat plate, but if the distortion of the original plate is almost flat, then It has been experimentally confirmed that the original board is corrected to a slightly elongated board, and that the original board with moderate elongation is corrected to a board with an even worse degree of elongation. Therefore, considering this phenomenon, it would be sufficient to make a plate with slightly elongated edges in the pre-process of the stretcher/leveler and bring it to the stretcher/leveler, but it is not possible to control the strain in the pre-process. If so, the stretcher leveler becomes an unnecessary device, and therefore, in order to make the original function of the stretcher leveler work, it is necessary to improve the leveler so that it can correct any distortion of the base plate. It is desired.

In view of the above-mentioned circumstances, the present inventor first attempted an analysis using the finite element method in order to elucidate the conventional stretcher leveler phenomenon in order to solve the problem. That is, plane stress F=15956Kg
(σ = 8.0Kg/mm ² ), and when a base plate with dimensions of 2.0 ^t × 1000 ^W × 2000 ^L is stretched uniformly to give an elongation of δ = 0.54%, the diagonal line shown in Figure 1 a. For 1/4 part of the original plate (other parts appear symmetrically, the results can be used), stress in the X direction (σx), stress in the y direction (σy), shear stress (τxy), and equivalent stress. (σeq) and equivalent plastic strain (εp
eq), and use the results as the first
As shown in Figures b to f. And from these results,
In a metal sheet, as shown in Figure 1 (g), plastic strain is mainly concentrated in areas A at the four corners of the sheet and two areas B located approximately 1/5 from each edge at the approximate center in the width direction of the sheet. It turns out that it does. Therefore, since part A is the edge of the plate, even if the amount of plastic strain is larger than that of the surrounding parts, it will hardly affect the flatness of the whole plate, but part B At the center of the board in the width direction,
Moreover, since it is located inside the sheet, there is excess thickness compared to the surrounding area, and the center of the sheet eventually swells, resulting in a board with medium elongation.This is the cause of the phenomenon of medium elongation in stretchers and levelers. .

The inventor of the present invention was able to elucidate the conventional phenomenon in stretcher levelers as described above, and in order to improve the leveler, he conducted further analysis using a similar finite element method to improve the shape of various clampers. Even if the clamper shape is changed, the local plastic strain concentration as described above cannot be prevented, and it is necessary to devise a tension method to eliminate the plastic strain concentration. It has been found that it is effective to vary the magnitude of the tensile force in the width direction of the plate as shown in FIG. 2a.

In other words, under the conditions of F = 15682 Kg and δ = 0.55%, 2.0 ^t × 1000 ^W is subjected to uneven tension (the ends receive twice the force compared to the center) as shown in Figure 2 a.
The stress distribution of each metal sheet of ×2000 ^L dimension is shown in Figure 2 b to f, and it is clear from these that the equivalent plastic strain (εp eq) is locally concentrated, especially in the center of the sheet. Concentration [B in Figure 1 g
), which reduces the stretcher
This suppresses the occurrence of medium elongation after leveling.

The present invention was completed based on this knowledge, and its gist is to change the tensile force applied to a metal sheet in the length direction of the sheet in the width direction, thereby reducing the strain that exists in the metal sheet. According to the medium elongation state or edge elongation state, a larger tensile force is applied to the part where there is no elongation than the part where there is elongation,
In particular, in order to practically implement such a method, the present invention has a plurality of clampers in the width direction of the metal sheet, and each of the clampers independently controls the ends of the metal sheet in the length direction. In addition to using a stretcher leveler that can be clamped and pulled, the tensioning operation can be performed in one step, or after pre-pulling only the area where a large tensile force needs to be applied, the final tension is applied evenly over the entire width. This is done by applying tension in multiple stages.

FIG. 3a shows schematically a stretcher leveler which is desirable for carrying out the method described above, in which a metal sheet S is divided into a plurality of parts at each longitudinal end of the metal sheet S, which are divided as far as possible. clamper
They are each clamped by a necessary clamper among _C1 to _C7 , and a predetermined pulling operation is applied in the direction of the arrow. In addition, by pulling the metal sheet S using as many clampers C ₁ , C ₂ , ... as possible, uneven elongation (displacement) in the width direction applied to the metal sheet S can be suppressed. This makes it possible to change the tension smoothly and to apply a predetermined tensile force to the necessary portions accurately. When the metal sheet S is clamped and pulled by the clampers C ₁ , C ₂ , . ), a larger tensile force is applied to the parts with less . , a larger tensile force is applied toward the sides, and in the case of elongation at both ends, a larger tensile force is applied toward the center as shown in FIG. 3c. For such a tensioning operation, the clampers C ₁ , C _{2 .} . . are operated independently, and the target metal sheet S
The parts are clamped and pulled, but here, as shown in the figure, each clamper C ₁ ,
C ₂ . . . is equipped with clamp cylinders CL ₁ , CL ₂ . A tension cylinder SC is provided for this purpose. Therefore, when performing tension as shown in FIG. 3b, for example, first the clamper is
After clamping and pulling the metal sheet S only with C ₂ and C ₅ and applying a tensile force only to both sides, the entire width of the sheet S is clamped with clampers C ₂ , C ₃ , C ₄ , and C ₅ . By applying equal tension to the
A predetermined tension will be applied.

Incidentally, metal sheets (aluminum A50
52 H34 or Aluminum A1100 H14 2.0×1000×
Figure 4 shows the results of actually stretching the 2000 material) in comparison with the conventional method. In addition, in FIG. 4, the numerical values attached to each part of the sheet indicate the height (mm) from the reference horizontal plane.

As is clear from the results shown in Figure 4, even if the metal sheet is clamped and stretched over its entire width as in the past, there is a certain leveling (flattening) effect on the sheet that is stretched at one end. However, in the case of a sheet with medium elongation, the extent of its medium elongation is emphasized, and in the case of a sheet with strong elongation at both ends, it cannot be flattened sufficiently so that it can be changed into a sheet with medium elongation. .

On the other hand, when a medium elongation sheet is subjected to multi-stage tensioning operations according to the present invention and the tensile force applied in the longitudinal direction is changed in the width direction, the medium elongation condition is effectively improved. It can be straightened into a highly flattened sheet. especially,
A sheet with a light medium elongation can be flattened considerably by simply tensioning only both sides of the sheet with clamps, and depending on the degree of strain (medium elongation), different tensile forces in the longitudinal direction can be applied to the two sides. If it is necessary to apply the force, it is sufficient to sequentially pull each side portion one by one, and finally apply uniform tension to the entire width.

Furthermore, it is clear from FIG. 4 that an excellent leveling effect can be achieved by applying the method of the present invention even to sheets with edge stretching. In addition, in the case of a sheet that is stretched at one end, only the non-stretched side is first pulled, and then tension is applied uniformly across the entire width, and in the case of a sheet that is stretched at both ends, a large tensile force is applied to the center. An excellent flattened sheet is obtained by first pulling only the central portion of the sheet, and then applying uniform tension across the entire width so that the sheet has a flattened surface.

As described above, according to the present invention, the present invention is not limited to straightening sheets in a specific state of distortion as in conventional stretcher levelers, but can also straighten sheets in any state of distortion, such as medium elongation and edge elongation. By applying a tensile force that changes in the sheet width direction in accordance with the strain in the sheet length direction, it has become possible to straighten the sheet into an extremely flat sheet.

Note that the present invention is not limited to the specific methods exemplified above in any way, and various changes and improvements can be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. for example,
In the above example, the tensioning of the metal sheet is performed in multiple stages, but it is also possible to perform this in one stage. In such a case, each clamper _C1 , _C2 , . In addition, the degree of tension applied to the metal sheet in the plate length direction and the degree of change in the plate width direction are determined empirically depending on the material of the sheet, the location and degree of strain, the intended degree of correction, etc. A decision will be made as appropriate.

[Brief explanation of the drawing]

Figures 1 a to f and 2 a to f show the analysis results of stress in the conventional method and the method of the present invention using the finite element method, respectively, and each a explains the analysis part of the metal sheet and the tensile method, respectively. In the figure, each b is the stress distribution diagram in the x direction, and each c is the y
Each d is a distribution diagram of shear stress, each e is a distribution diagram of equivalent stress, each f is a distribution diagram of equivalent plastic strain, and the first
Figure g is an explanatory diagram showing a portion where plastic strain is concentrated in a metal sheet. FIG. 3a is a plan view showing an apparatus suitable for carrying out the present invention, and FIGS. 3b and 3c are diagrams showing typical tension patterns for a medium-stretched device and an edge-stretched device, respectively. Furthermore, FIG. 4 is a diagram showing the results of stretching metal sheets containing various strains according to the conventional method and the method of the present invention, respectively. S...metal sheet, C _o ...clamper, CL _o ...clamp cylinder, SC...tension cylinder.

Claims (1)

[Scope of Claims] 1. A method for correcting distortion of a metal sheet by a tensile operation using a stretcher leveler, wherein the stretcher leveler includes a plurality of clampers in the width direction of the metal sheet, and Using a clamper that independently clamps and tensions the ends of the metal sheet in the plate length direction, and applying tension in the plate length direction to the metal sheet by each of the independent clampers. A stretcher leveler characterized in that the force is varied in the width direction of the metal sheet, and a larger tensile force is applied to the part where there is no elongation than the part where there is no elongation depending on the state of middle elongation or end elongation of the metal sheet. Straightening method for metal sheets. 2 The tensile force in the plate length direction that changes in the width direction is
2. The method of claim 1, wherein said method is caused by a single pulling operation by said plurality of clampers. 3. Clamp only the center portion or only one or both side portions of the ends of the metal sheet in the plate length direction with a clamper located at the part and pre-tension it in the plate length direction, and then The method according to claim 1, wherein the entire width of the longitudinal end portion is clamped and the plate is pulled uniformly in the longitudinal direction. 4. After clamping one side part of the end of the metal sheet in the plate length direction with a clamper located at that part and pulling it in the plate length direction, apply the same tension to the other side part. 2. The method according to claim 1, wherein the metal sheet is stretched uniformly in the longitudinal direction by clamping the entire width of the end of the metal sheet in the longitudinal direction.