JP3483406B2 - Counter-hydraulic forming method of Al-Mg based aluminum alloy sheet - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention
Regarding the facing hydraulic forming method of the Al-Mg-based aluminum alloy sheet containing the above, particularly when it is necessary to have a good appearance such as a car outer plate, when forming a member having a concave shape on the punch side The present invention relates to a facing hydraulic forming method of an Al-Mg-based aluminum alloy plate having high formability and capable of suppressing SS marks. [0002] CAFE (Corporate Average FueI Eco
In order to comply with regulations and the like, in the automobile industry, the use of aluminum as a material has been promoted in order to realize lighter weight and lower fuel consumption of automobiles. However, the formability of the aluminum alloy plate is poorer than that of the steel plate.
g in an aluminum alloy plate containing 2% or more,
Although the strength is high, a surface defect called an SS mark occurs on the surface of the sample after molding, which causes a problem of deteriorating the appearance of the product. In view of the above, with respect to molding of complicated shapes such as an outer plate and an inner plate for automobiles, attention has been paid to the application of an opposing hydraulic forming method having excellent formability (for example, Japanese Patent Publication No. 57-7809).
No., Tokuhei 3-32406). This opposing hydraulic forming method is a method of forming with a wrinkle retainer, a punch and a hydraulic dome, and is formed by hydraulic pressure without using a die. In this hydraulic forming method, by applying a hydraulic pressure, a friction holding effect in which the frictional resistance between the material and the punch is increased, and a friction reducing effect in which the frictional resistance between the material and the blank holder is reduced. The uniform deformation of the material is promoted by the former friction holding effect, and the flow of the material is promoted by the latter friction reducing effect, so that the formability can be improved. However, in the current opposing hydraulic molding of actual parts, the optimal pattern of hydraulic pressure has not yet been established.
For this reason, a pattern in which the hydraulic pressure is applied only at the bottom dead center is common. In order to suppress the SS mark, measures have also been taken from the material side of the aluminum alloy plate.
For example, JP-A-2-290953, JP-A-4-147
As disclosed in U.S. Pat. No. 952, etc., a technique for suppressing the SS mark by adjusting the composition and performing intermediate annealing is known. Further, a method of suppressing the SS mark by giving a processing strain by preliminary stretching using a leveler or the like is also known. [0006] However, in the case of forming an aluminum alloy plate by the facing hydraulic forming method, there is a report example in which the forming conditions in a small press using a symmetrical punch have been studied, but there is a report example. The optimal molding conditions for counter-hydraulic molding technology at the level are still unknown. As described above, when a hydraulic pattern for applying a hydraulic pressure at the bottom dead center after the completion of molding in the facing hydraulic molding of the automobile outer plate is used, a concave shape is formed on the surface of the molded product, particularly on the punch side. However, there is a problem that the SS mark is remarkably generated in a portion having the following. On the other hand, as measures for preventing SS marks from the surface of the material, intermediate annealing and pre-stretching have been carried out. However, by performing intermediate annealing, solid-solution Mg decreases and strength decreases. By performing the pre-stretching, problems such as an excessive increase in strength and a decrease in formability occur, and at present, the SS mark cannot be sufficiently suppressed only by improving the material surface. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and uses a facing hydraulic forming method, which is effective for improving the formability of an aluminum alloy plate, to produce a product having a complicated shape with high formability. In particular, when molding a member having a concave shape on the punch side, it has high formability and S-
It is an object of the present invention to provide a facing hydraulic forming method of an Al-Mg based alloy plate capable of sufficiently suppressing the S mark. [0010] According to the present invention, there is provided an Al-Mg according to the present invention.
The opposing hydraulic forming method for a system-based alloy plate is a method for opposing hydraulic forming an Al-Mg-based aluminum alloy plate containing 2.0% by weight or more of Mg, wherein the final hydraulic pressure is Pe and the final forming depth is De. Then, the final hydraulic pressure Pe is set to 30 kg / cm ² or more, and the hydraulic pressure P is set to (20 Pe) D with respect to the forming depth D.
/ De-19Pe≤P≤ (5Pe) D / (4De) and 0≤P≤Pe and the pressure is changed so as not to reduce the pressure, and the hydraulic pressure P is such that the molding depth D is 0.9 De or more.
It is molded with a liquid pressure of 0.1 Pe or less until it becomes less than De.
After that, the hydraulic pressure P is increased to the final hydraulic pressure Pe, and the final forming depth is increased.
It is characterized by being molded up to De . By forming an aluminum alloy plate by the opposing hydraulic forming method under the above conditions, the occurrence of SS marks is prevented even in a complicated shape, and the formability is improved. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have found that when forming an aluminum alloy member having a concave shape on the punch side by a facing hydraulic forming method, the SS mark is formed while maintaining high formability. As a result of studying the molding conditions for suppressing, it was found that when the pattern of the hydraulic pressure P with respect to the molding depth D falls within the following range, the moldability is improved and the SS mark can be prevented. . That is, the molding depth D is plotted on the horizontal axis.
And taking the hydraulic pressure P on the vertical axis and considering a coordinate axis with the origin at the molding start point, the hydraulic pressure P becomes the final hydraulic pressure Pe (kg /
cm ² ), and the hydraulic pressure P needs to be within the range represented by the following formula before the forming depth D reaches the final forming depth De. ## EQU1 ## P≤ (5Pe) D / (4De) ## EQU2 ## P≥ (20Pe) D / De-19Pe ## EQU3 ## where 0≤P≤Pe. The final hydraulic pressure Pe is a maximum hydraulic pressure value at the time of performing the opposing hydraulic forming. When the final hydraulic pressure is reached on the way to the bottom dead center of the press (final forming depth De), the pressure is equal to the final hydraulic pressure Pe. Is held until the press bottom dead center De. FIG. 1 is a graph showing the conditions of equations (1) to (3). In the area surrounded by hatching in FIG. 1,
By changing the hydraulic pressure P with respect to the forming depth D, S
-The generation of the -S mark can be prevented. Further, the final hydraulic pressure Pe needs to be 30 kg / cm ² or more. Within the above range, 30 kg / cm ²
By changing the hydraulic pressure in a continuous pattern until the final hydraulic pressure Pe is reached, the formability is improved and the occurrence of the SS mark is prevented. If the hydraulic pressure P changes in a pattern exceeding the range of the formula 1, the excessive hydraulic pressure is applied, so that the friction reducing effect becomes too large, whereby the material flows more and wrinkles occur. I do. When the wrinkles suppress the material from flowing, cracks occur and molding becomes impossible. Also, depending on the timing of the mold and the application of the hydraulic pressure, a reverse overhang phenomenon occurs, thereby causing cracking. On the other hand, when the hydraulic pressure P falls below the range of Expression 2,
When the friction reducing effect is reduced, cracks are easily generated. In addition, since the timing of applying the hydraulic pressure is delayed, the material is distorted by the punch, particularly in a portion having a concave shape on the punch side, similarly to the normal molding method which is not the opposing hydraulic molding method. . Then, after the pressing force by the punch, the formation of the concave portion is further performed by the application of the liquid pressure, and the strain rate near the concave portion is substantially reduced, which is a condition in which the SS mark is easily generated. .
Actually, the SS mark was partially generated on the surface of the molded product. The hydraulic pressure P needs to be a positive pressure (0 kg / cm ² or more). Further, in the opposed hydraulic forming method, since the final hydraulic pressure Pe is the maximum hydraulic pressure, P needs to satisfy the above equation (3). On the other hand, the reason why the final hydraulic pressure Pe is set to 30 kg / cm ² or more is that if the final hydraulic pressure Pe is less than 30 kg / cm ² , it becomes difficult to process a complicated shape, and the material and the die In this case, the friction holding effect and the friction reducing effect are insufficient, and cracks are likely to occur. Therefore, the final hydraulic pressure Pe is 3
0 kg / cm ² or more. The hydraulic pressure pattern within the above range changes continuously or keeps constant so that there is no singular point of the hydraulic pressure, and the change of the hydraulic pressure does not decrease. . That is, the hydraulic pressure must be increased or kept constant within the above range, and must not be reduced. When a pattern in which the hydraulic pressure is reduced is added to the hydraulic pressure pattern, the friction holding effect and the friction reducing effect between the material and the mold are reduced, cracks are easily generated, and it becomes difficult to form an aluminum alloy plate. . For example, as the hydraulic pressure pattern, the hydraulic pressure P is continuously increased to the final hydraulic pressure Pe until the molding depth D becomes 0.8 De or more and less than De.
There is a type in which e is maintained to form a final forming depth De. When this hydraulic pattern is used, high formability can be obtained due to a sufficient friction holding effect and a friction reducing effect. Also,
In particular, in the case of a mold having a concave shape, the deformation speed increases due to the early contact between the concave portion and the material, and the SS mark is significantly reduced. The pattern of the hydraulic pressure P is 0.1 Pe until the molding depth D becomes 0.9 De or more and less than De.
The molding may be performed with the following hydraulic pressure, and thereafter, the hydraulic pressure P may be increased to the final hydraulic pressure Pe to perform molding to the final molding depth De. In particular, when the clearance between the punch and the die is large, in the case of a mold having extreme irregularities on the side wall of the punch, and when the material strength is high and wrinkles are likely to occur, increasing the liquid pressure from the beginning will cause wrinkles to grow. Or the flow of the material stops at the uneven part, and cracks occur.However, when this hydraulic pressure pattern is used, there is no suppression of wrinkles and the flow of the material, and high moldability is obtained, S-
The S mark can be reduced. The composition of the aluminum alloy sheet to be formed contains Mg in an amount of 2.0% by weight or more. M
When the g content is less than 2.0% by weight, the SS mark does not occur even if the hydraulic pressure pattern is not within the above range, and the strength as a member is low. And it cannot be used for applications such as inner plates. EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Three types of Al-Mg alloys having Mg content and mechanical properties shown in Table 1 below are used as test materials, and have a width of 500 mm, a length of 800 mm, a depth of 50 mm, and a concave shape in the center. Using a hood outer model mold, the counter-hydraulic molding method is used under the condition that the SS mark with the viscosity of the rust preventive oil is 4 cSt / 40 ° C. and the strain rate is 1 × 10 ⁻³ / sec. The test material was formed. The press used in this test was a double-acting hydraulic press, which was designed to have a maximum punch load of 1000 tons, a maximum wrinkle holding load of 400 tons, and a maximum pressure increase capacity of 240 kg / cm.
² [Table 1] Table 2 below shows the results of molding tests performed under the above conditions with each of the hydraulic patterns 1 to 5 shown in FIG.
However, each hydraulic pressure pattern is as follows. Pattern 1 (Example): Equation 1 up to a molding depth of 0.8 De
While gradually increasing the hydraulic pressure so as to satisfy the conditions (1) and (2), and then forming the final hydraulic pressure P to the bottom dead center.
This is a pattern formed while holding e. Pattern 2 (Example): Within the range shown in Expressions 1 and 2, slightly increase the hydraulic pressure to a molding depth of 0.9 De, stop increasing the hydraulic pressure to 0.1 Pe, and increase the liquid pressure from 0.9 De to the bottom dead center. The pressure is sharply increased to the final hydraulic pressure Pe for molding. Pattern 3 (Comparative Example): A pattern formed by slightly increasing the liquid pressure almost to the bottom dead center and rapidly increasing the liquid pressure as it is. Pattern 4 (Comparative Example): From the initial stage of molding to the vicinity of the bottom dead center, slightly increase the hydraulic pressure within the range of Expressions 1 and 2 and set the final hydraulic pressure to 3
The pattern is less than 0 kg / cm ² . Pattern 5 (Comparative Example): The hydraulic pressure is increased within the range shown by Formulas 1 and 2 to a molding depth of 0.4 De, and thereafter, the hydraulic pressure is rapidly continued from the molding depth of 0.4 De to 0.8 De. This is a pattern formed by increasing the final hydraulic pressure to the final hydraulic pressure Pe and maintaining the final hydraulic pressure until the bottom dead center. [Table 2] In Table 2, as for the cracks described in the evaluation column, ○ indicates that no crack occurred, and × indicates that crack occurred.
The SS mark was visually evaluated on a five-point scale for samples in which cracks did not occur, and a sample with remarkable SS mark generation was rated at 5 levels, and a sample without SS mark generation was rated as 1 level. Level, 1 and 2 levels are ○, 3 and 4 levels are Δ,
Five levels were evaluated as x. The strength was evaluated based on the material strength, and those having a strength of 190 N / mm ² or more were rated as ○, and those less than 190 N / mm ² were rated as x. As is apparent from Table 2 and FIG. 1, in Examples 1 to 3 of the present invention, the molded product had no cracks,
This is a good one in which the occurrence of S marks is suppressed. On the other hand, in Comparative Examples 4 to 9, since the hydraulic pattern was out of the scope of the claims of the present invention, cracks were generated in the molded product, or SS marks were generated. . In Comparative Example 6, the final hydraulic pressure of the hydraulic pressure pattern was 3
When it was less than 0 kg / cm ² , cracks occurred. According to the method for counter pressure hydraulic forming of an aluminum alloy sheet according to the present invention, it is possible to prevent the occurrence of cracks in the molded product and to suppress the occurrence of SS marks.
The present invention has an excellent effect that a complicated shape can be formed for an aluminum alloy plate containing 2.0% by weight or more of Mg.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph illustrating a facing hydraulic forming method of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akihito Sato 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Kenji Tamada 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 56) References JP-A-5-7943 (JP, A) JP-A-8-90091 (JP, A) JP-A-57-44423 (JP, A) JP-A-9-24424 (JP, A) 57-70724 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21D 22/20 B21D 22/26 B21D 26/02

Claims (1)

(57) [Claims 1] Al-containing at least 2.0% by weight of Mg.
In the method of opposing hydraulic forming of a Mg-based aluminum alloy plate, when the final hydraulic pressure is Pe and the final forming depth is De, the final hydraulic pressure Pe is 30 kg / cm ² or more, and Pressure P is set to (20Pe) D / De-19P
satisfy the relation of e ≦ P ≦ (5Pe) D / (4De) and 0 ≦ P ≦ Pe with changing so as not to vacuum, before
The hydraulic pressure P is such that the molding depth D becomes 0.9 De or more and less than De.
Up to a hydraulic pressure of 0.1 Pe or less, and then increase the hydraulic pressure P
Increase to final hydraulic pressure Pe and mold to final molding depth De
Opposed hydraulic forming method of Al-Mg series aluminum alloy sheet, characterized by.