TWI453073B - Designing method of materials for cylindrically forming and cylindrically formed products - Google Patents

Description

Design method of material for cylindrical forming and cylindrical processed product

The present invention relates to a method of designing a metal material capable of setting a springback angle at the time of forming a cylinder into a predetermined value, and a cylindrical processed product.

In a food container, a medical device, a metal container, a device part, and the like, a cylindrical processed product is used, and the cylindrical processed product is subjected to a cylindrical forming process using a bending process for a metal material (hereinafter referred to as a circle) Processed product manufactured by tube forming. For example, in a three-piece can including a lid portion, a main body portion, and a bottom portion, a cylindrical processed product obtained by subjecting a main body portion to a cylindrical shape is used.

In general, when a metal material (metal plate) is subjected to a cylindrical forming process and then unloaded, the metal material rebounds due to the elastic recovery, and as a result, the cylindrical shape changes. Therefore, when the cylindrical forming process is performed, it is necessary to determine the processing conditions in advance in consideration of the above-described rebound.

A recent tendency is to make the thickness of the metal material thin (hereinafter also referred to as thinning) to reduce the material cost. However, when the thickness is reduced, the rebound angle is increased, and a predetermined cylindrical shape cannot be secured, that is, a predetermined winding width cannot be secured. Here, the rebound angle is defined by the amount of change in the bending process from the bending angle at the time of load to the bending angle after unloading. In addition, as shown in FIG. 1, the winding width is defined as the interval between the one end of the metal plate which is formed into a cylindrical shape by the cylindrical forming process and the end on the opposite side, and the both ends are opposite. The state of the connection is set to 0, the positive value indicates the state in which both ends are open, and the negative value indicates the state in which both ends overlap.

When the winding width is changed by thinning, the subsequent steps (for example, the step of welding the end portion to form the main body portion of the three-piece can) are hindered. Therefore, it is necessary to make the winding width even if the thickness is reduced. There will be no change. Therefore, in the cylindrical forming step, when the metal material having a thick plate thickness is changed to a metal material having a thin plate thickness, the forming processing conditions must be newly set or the forming device is modified, thereby hindering the productivity improvement or Impede cost reduction.

Therefore, as long as a metal material having a predetermined cylindrical shape (winding width) can be obtained even when the thickness of the sheet is reduced, it is not necessary to reset the forming processing conditions or to modify the forming apparatus. That is, the following metal material must be designed, and even if the thickness of the plate is changed, the metal material can obtain a rebound angle equivalent to that before the plate thickness is changed.

However, if the metal material used for processing is a completely elastoplastic body which is not work hardened, theoretically, the rebound angle can be calculated according to the following formula (2) (see Non-Patent Document 1).

Δθ/θ=3(YP.r)/(E.t)-4[(YP.r)/(E.t)] ³ (2)

Here, Δθ: rebound angle (degree), θ: bending angle (degree), r: bending radius of curvature (mm), t: plate thickness (mm), YP: yield strength (MPa), E: Young's modulus (MPa).

Therefore, using equation (2) and depending on the target plate thickness or rebound angle, The mechanical properties (Young's modulus, fall strength) required for the metal material are calculated to design a metal material having the above mechanical properties.

However, according to Non-Patent Document 2, it is known that the theoretical formula represented by the above formula (2) does not necessarily correctly reproduce the experimental fact. Further, Non-Patent Document 2 has proposed an experimental formula for a stainless steel plate. However, the metal material is limited to a stainless steel plate. This experimental formula is not suitable for a wide variety of metal materials, and has problems in versatility.

[Previous Technical Literature]

[Non-Patent Document 1] Racecourse, Hashida: Iron and Steel, Japan Iron and Steel Association, Chi, 49 (3) (1963) P507

[Non-Patent Document 2] Sugimoto, Fukui, Mitsui, Watanabe, Nakamura: Iron and Steel, 66 (1980) S976

The present invention has been made in view of the above circumstances, and an object of the present invention is to newly find a method for calculating a rebound angle when performing cylindrical forming processing on a metal material having various mechanical properties or plate thicknesses, and A method of designing a metal material having the following material (mechanical characteristics) and a processed product produced by subjecting a metal material designed by the method to a cylindrical forming process, and the above-mentioned calculation method can be used for the above-mentioned material (mechanical property) Set the rebound angle to the specified value.

The gist of the present invention is as follows.

[1] A method of designing a material for cylindrical forming, characterized in that each time a metal material subjected to a cylindrical forming process by bending is designed, a rebound angle Δθ is brought to a predetermined value. ,based on Calculating the fall strength YP, the Young's modulus E, and the plate thickness t of the above metal material by the following formula (1), and having the above-described calculated fall strength YP and Young's modulus E, the above metal material In the design, the rebound angle Δθ is a rebound angle when the metal material is subjected to cylindrical forming under the condition that the bending radius r is 5 mm or more and the bending angle θ is 90 degrees or more and 180 degrees or less.

Δθ/θ=-5.52[(YP.r)/(E.t)] ² +4.13(YP.r)/(E.t)(1)

Here, Δθ: rebound angle (degree), θ: bending angle (degree), YP: fall strength (MPa), E: Young's modulus (MPa), t: plate thickness (mm), r: bending Radius of curvature (mm).

[2] A cylindrical molded article obtained by subjecting a metal material designed by the method according to [1] to a cylindrical forming process by bending.

According to the present invention, it is possible to easily design a metal material which can set the rebound angle to a predetermined value, thereby greatly contributing to an improvement in productivity in a cylindrical forming step or a reduction in cost.

If the metal material having the same mechanical properties and different plate thicknesses is subjected to cylindrical forming under the same conditions, the rebound angle may vary depending on the thickness of the plate, so that it is difficult to obtain a fixed winding width (cylindrical shape) ). Therefore, in the case where the cylindrical forming process is performed at the production site, the forming apparatus is modified every time the thickness of the sheet is changed, or the processing conditions are adjusted according to the thickness of the sheet, thereby hindering productivity and the like. In order to solve the above problem, it is conceivable to change the above-mentioned metal material to another metal material, and the mechanical properties of the other metal materials vary depending on the thickness of the sheet. In other words, when the thickness of the sheet is changed from t ₁ to t ₂ , if a metal material having the following mechanical properties is used, a processed product in which the winding width does not change after the cylindrical forming process can be obtained, the above mechanical properties. The rebound angle is made equal to the rebound angle of the metal material having a thickness t ₁ .

Therefore, it is necessary to clarify the influence of each factor of the plate thickness, mechanical characteristics, and molding processing conditions of the metal material on the rebound angle. Therefore, the inventors first studied which factor in each factor affects the rebound angle. As a result, it has been confirmed that the above factors are a bending angle, a bending curvature radius, a plate thickness, a lodging strength, and a Young's modulus.

Next, under the condition that various factors are changed, the bending process is performed, the rebound angle is measured, and the degree of influence of each factor is quantitatively evaluated, and the following experimental formula is derived, which indicates the rebound angle. Relationship with the above factors. Hereinafter, it demonstrates in detail.

As described above, generally, when the metal material is subjected to bending processing and then unloaded, the metal material slightly changes from the shape of the load state due to the elastic recovery. This change is called a rebound. If the bending angle θ (degrees) changes to θ' (degrees) due to the rebound, the rebound angle Δθ (degrees) is expressed by the formula (3). Further, in the bending process, if the radius of curvature of the surface having no distortion in the circumferential direction changes from r (mm) to r' (mm) due to springback, it is obtained. A relationship expressed by the following formula (4) is obtained.

△θ=θ-θ' (3)

Δθ/θ=(1/r-1/r')/(1/r') (4)

When the surface having no distortion change is at the center position of the plate thickness before and after the unloading, the following formula (5) is established by using the above formula (4) with respect to the change in curvature caused by the unloading.

△θ/θ=(M.r)/(E.I) (5)

Here, M is a bending moment (MPa.mm ³ ), and I is a secondary moment of the section (mm ⁴ ).

According to the simple bending theory, the bending moment M is represented by the following formula (6). Therefore, by substituting the formula (6) into the above formula (5), the following formula (7) is obtained. Further, if the metal material is a completely elastoplastic body which is not work hardened, n (work hardening index) = 0, and therefore, the above formula (2) can be obtained according to the formula (7). However, for an actual metal material, if n=0, it is not appropriate, and the value of n differs depending on the metal material.

In the above non-patent document 2, it was found that there is a correlation between Δθ/θ and (YP.r)/(E.t) based on an experiment for a stainless steel plate, and the equation (8) is derived. However, since the object is limited to the stainless steel plate, the range of the factor of Δθ/θ can be determined to be narrow (0 < (YP.r) / (E.t) ≦ 0.11), and lacks versatility.

Δθ/θ=1.9[(YP.r)/(E.t)] ^0.62 (8)

Therefore, the inventors of the present invention actually performed bending processing using various metal materials (aluminum plate, copper plate, stainless steel plate, and steel plate) and plate thickness conditions, and measured the rebound angle. At this time, the bending curvature radius is set to a range of 5 mm or more, and the bending angle is set to a range of 90 degrees to 180 degrees. Further, the thickness of the plate is set to be in the range of 0.1 mm to 2.0 mm. The reason is that, in the above range, it is sufficiently durable and versatile in the fields of food containers, medical equipment, metal containers, and device parts.

Fig. 2 shows the result of sorting based on the relationship between Δθ/θ and (YP.r)/(E.t). In the figure, ○ is the measurement result. Based on the above measurement results, a regression equation that can be reproduced with high precision is obtained, and the above formula (1) (see the solid line in the drawing) is obtained. The formula (1) can be used in a region where (YP.r) / (E.t) is 0.33 or less, and the range of use of the formula (1) is different. The scope of use of Patent Document 2 is broader. That is, the formula (1) can be applied to a wide variety of metal materials, and the following mechanical properties (YP, E) can be calculated according to the formula, and the mechanical properties (YP, E) refer to the desired plate. At the thickness, the specified rebound angle is reached. Next, it is only necessary to design a metal material having the above-described calculated mechanical properties. Further, it is also possible to obtain a plate thickness that reaches a predetermined rebound angle for a metal material having predetermined mechanical properties. In addition, the rebound angle can also be calculated based on the desired plate thickness and mechanical properties. In FIG. 2, the measurement data (data) in Non-Patent Document 2 is indicated by Δ, and the equation (8) is represented by a broken line, and the equation (2) is also expressed by a broken line.

Hereinafter, a sequence of designing a metal material such that when the thickness of the metal material subjected to the cylindrical forming process is reduced, even if the thickness of the plate is changed, the rebound angle is not changed (not Will change the winding width).

First, the rebound angle Δθ before the thickness of the plate was changed was measured. For example, a test piece having an arbitrary size is subjected to bending processing under the conditions of a curvature radius of curvature of 12.7 mm and a bending angle of 180 degrees. Next, the bending angle θ' of the test piece after the unloading is measured, and the rebound angle Δθ is calculated based on the above formula (3). When the rebound angle Δθ is saved as an existing material, the above sequence can also be omitted.

The rebound angle Δθ obtained in the above manner and the bending angle θ (=180°) are substituted into the formula (1), whereby the curvature radius r and the plate thickness t are known from the right side, and therefore, the lodging strength is The value of the ratio of Young's modulus (YP/E) is determined. Next, consider the gold that is subjected to the cylinder forming process. According to the specifications of the material, the fall strength YP and the Young's modulus E are determined based on the obtained YP/E, and the metal material having the above mechanical properties is designed. Furthermore, regarding the design of the material, a metal material satisfying the above mechanical properties can be selected from a metal material database. When there is no metal material satisfying the above mechanical properties in the database, the above YP and E are used as indicators, New materials can be designed.

As another embodiment, a case where the mechanical properties of the metal material subjected to the cylindrical forming process are changed will be described. First, in the same manner as described above, the metal material before the mechanical property change is subjected to bending processing, and the rebound angle is obtained in advance. Next, based on the above-described rebound angle, predetermined fall strength YP and Young's modulus E, and bending processing conditions (bending radius of curvature, bending angle), the plate thickness t is calculated according to the formula (1). When the metal material having the above-described plate thickness and mechanical properties is subjected to cylindrical forming, a winding width equivalent to that before the change in mechanical properties can be obtained.

As described above, in the present invention, when the required characteristics (plate thickness or mechanical properties) of the metal material are changed, first, the rebound angle of the metal material before the change is made clear, and then, the satisfaction formula (1) Under the conditions of the metal material, the characteristics of the metal material are sequentially determined, whereby the predetermined winding width can be ensured after the cylinder is formed.

[Example]

When the thickness of the metal material subjected to the cylindrical forming process is reduced, the material is designed for a metal material requiring a winding width equivalent to that before the plate thickness is reduced. First, an example of research on optimization of the fall strength YP, that is, a rule of a metal material before the thickness of the plate is reduced The grid is t=0.153 mm, YP=400 MPa, E=206000 MPa, Δθ=96 degrees, θ=180 degrees, r=12.7 mm, winding width=-10.5~-9.0 mm (average value: -9.6 mm) When the steel sheet is reduced to t=0.117 mm, in order to obtain a winding width equivalent to that before the sheet thickness is reduced, the fall strength YP is optimized so that the rebound angle is fixed. When Δθ=96 degrees, E=206000 MPa, and t=0.117 mm are substituted into the formula (1), if YP is about 310 MPa, the objective of achieving the object can be obtained.

Based on the above results, two steel sheets having a plate thickness of 0.117 mm and different lodging strength YP were produced, and 10 test pieces each having a size of 165.4 mm × 136.5 mm were cut out, and the cylinder was subjected to the same conditions as before the plate thickness was reduced. Forming processing. Table 1 shows the results of measuring the winding width after the cylinder was formed. Whether or not the determination of the winding width equivalent to the metal material before the thickness reduction of the plate is obtained is determined, and the unevenness of the winding width is considered, and within ±10% of the average winding width of the conventional material, It is judged as qualified. The winding width after the cylindrical forming using the steel plate (No. 2) of YP=300 MPa was -10.5 mm on the average value, and the degree of the metal material before the thickness reduction was obtained including the unevenness. Winding width. On the other hand, the winding width after the cylindrical forming using the steel sheet (No. 3) of YP = 362 MPa was +5.0 mm on the average value, and the same degree as the metal material before the sheet thickness reduction was obtained was not obtained. Winding width.

Next, an example in which the optimization of the Young's modulus E is studied is shown, that is, the specification of the metal material before the thickness of the plate is reduced is t=0.242 mm, YP=310 MPa, E=206000 MPa, Δθ=54.3. Degree, θ = 180 degrees, r = 12.7 mm, winding width = -12.0 to -8.0 mm (average value: -10.0 mm), when the steel sheet is reduced to t = 0.226 mm, in order to obtain a reduction from the thickness of the sheet The same winding width is used to optimize the Young's modulus E in such a way that the rebound angle is fixed. When Δθ=54.3, YP=310 MPa~320 MPa, and t=0.226 mm are substituted into the formula (1), if E is about 230,000 MPa, the objective of achieving the object can be obtained.

Based on the above results, two steel sheets having a plate thickness of 0.226 mm and different Young's modulus E were produced, and 10 test pieces each having a size of 165.4 mm × 136.5 mm were cut out, and rounded under the conditions before the plate thickness was reduced. Tube forming processing. Table 2 shows the results of measuring the winding width after molding each cylinder. Whether or not the determination of the winding width equivalent to the metal material before the thickness reduction of the plate is obtained is determined, and the unevenness of the winding width is considered, and within ±10% of the average winding width of the conventional material, It is judged as qualified. The winding width after the cylindrical forming using the steel plate (No. 2) of E = 231,000 MPa was -10.5 mm on the average value, and the degree of the metal material before the thickness reduction was obtained including the unevenness. Winding width. On the other hand, the winding width after the cylindrical forming using the steel plate (No. 3) of E=214000 MPa was -2.4 mm on the average value, and the same degree as the metal material before the plate thickness reduction was obtained was not obtained. Winding width.

In the above example, an example has been described in which, in the case where the thickness of the plate is reduced, either one of the fall strength and the Young's modulus is fixed, and the other is optimized, but it is also possible Both the drop strength and the Young's modulus change. Further, in the above example, an example has been described in which the lodging strength or Young's modulus is optimized in the case where the thickness of the plate is reduced, and the lodging strength or Young's modulus does not return The bullet angle (winding width) changes before or after the thickness of the panel is reduced, but the rebound angle can also be changed to a certain value. Further, the rebound angle at which the thickness of the sheet is changed can be obtained without changing the fall strength and the Young's modulus. Alternatively, the thickness of the sheet reaching the desired rebound angle may be determined without changing the strength of the fall and the Young's modulus.

E‧‧‧Young's modulus

R‧‧‧bending radius of curvature

T‧‧‧thickness

YP‧‧‧diffing strength

Θ‧‧‧bend angle

△θ‧‧‧ rebound angle

Figure 1 is a schematic view for explaining the winding width

Figure 2 is a graph showing the relationship between Δθ/θ and (YP.r)/(E.t)

E‧‧‧Young's modulus

R‧‧‧bending radius of curvature

T‧‧‧thickness

YP‧‧‧diffing strength

Θ‧‧‧bend angle

△θ‧‧‧ rebound angle

Claims (2)

A method for designing a material for forming a cylinder, characterized in that each time a metal material subjected to a cylindrical forming process by bending is designed, the rebound angle Δθ is set to a predetermined value, based on The formula (1) is used to calculate the fall strength YP, the Young's modulus E, and the sheet thickness t of the above metal material, and to perform the above-described metal material in such a manner that the calculated fall strength YP and Young's modulus E are obtained. In the design, the rebound angle Δθ is a rebound angle at the time of performing the cylindrical forming process on the metal material under the condition that the bending radius r is 5 mm or more and the bending angle θ is 90 degrees or more and 180 degrees or less. θ/θ=-5.52[(YP.r)/(E.t)] ² +4.13(YP.r)/(E.t)(1) where Δθ: rebound angle (degrees), θ : bending angle (degrees), YP: falling strength (MPa), E: Young's modulus (MPa), t: plate thickness (mm), r: bending radius of curvature (mm). A cylindrical processed product obtained by subjecting a metal material designed by a design method of a material for cylindrical forming according to the first aspect of the invention to a cylindrical forming process by bending .