CN112792200A - Hot-press forming method for variable-curvature skin sheet metal part - Google Patents
Hot-press forming method for variable-curvature skin sheet metal part Download PDFInfo
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- CN112792200A CN112792200A CN202011589262.8A CN202011589262A CN112792200A CN 112792200 A CN112792200 A CN 112792200A CN 202011589262 A CN202011589262 A CN 202011589262A CN 112792200 A CN112792200 A CN 112792200A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/20—Deep-drawing
- B21D22/22—Deep-drawing with devices for holding the edge of the blanks
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D37/00—Tools as parts of machines covered by this subclass
- B21D37/16—Heating or cooling
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- Shaping Metal By Deep-Drawing, Or The Like (AREA)
Abstract
The invention discloses a hot press forming method for a variable curvature skin type sheet metal part, and belongs to the technical field of sheet metal and hot forming. The invention solves the defects of easy occurrence of wrinkles, cracks and the like in the hot press forming of the prior variable-curvature skin sheet metal part and the problem of long forming period. The invention calculates the expansion size of the part by a finite element analysis method, and effectively solves the problem of local wrinkles after the part is formed by optimizing the structure of the die and changing the hot pressing mode of the part. The contour of the expanded material after being changed effectively gets rid of the complex stress influence of excessive process allowance on the position where folds are easy to appear in hot forming, the plate can be attached along with the profile in the hot forming process, and the plate positioning holes are designed at the two ends of the expanded material, so that the expanded material is a fixing hole for hot-press forming of the plate and a positioning hole for subsequent laser cutting of a part, and the working efficiency of the laser cutting of the part is greatly improved.
Description
Technical Field
The invention relates to a hot-press forming method of a variable-curvature skin type sheet metal part, and belongs to the technical field of sheet metal and hot forming.
Background
The skin is a variable-curvature large-size sheet metal part, the structure of the skin is a sheet metal part with a concave middle part and two upturned ends in a saddle shape, and due to the large size and large curvature change, the uneven wall thickness of the part is easily caused by improper air pressure control by adopting a superplastic forming method, so that the appearance requirement of the skin part is difficult to meet. In the prior art, a hot forming process is usually adopted for forming, and the method has the characteristics of simple and convenient manufacturing process, low cost and the like, but because the sheet metal material has certain plasticity in a high-temperature state, the sheet metal material cannot be discharged in a limited space in the hot pressing process directly by adopting a hot forming method due to larger shape curvature, the defects of large-area folds, cracks and the like are inevitably generated, and the qualified rate can only reach 15%. And the existing skin hot-press forming often needs hot-press forming treatment after hot-press forming, so that the process period is long. Therefore, it is necessary to provide an effective hot press forming method for variable curvature skin type sheet metal parts.
Disclosure of Invention
The invention provides a variable curvature skin type sheet metal part hot press forming method, aiming at solving the technical problems of the existing variable curvature skin type sheet metal part hot press forming.
The technical scheme of the invention is as follows:
a variable curvature skin sheet metal part hot press forming method comprises the following operation steps:
step 1, determining the outline of an unfolded material;
calculating the size of an expanded material of the part according to the overall dimension of the finally formed part, determining the outline of the expanded material of the part, reserving positioning surfaces at two expanded ends, and designing positioning holes on the positioning surfaces;
step 2, hot-press forming of the spread material;
installing a hot-press forming male die and a female die in a hot-press forming machine, ensuring that the female die is below an upper male die, and then preheating the die; after the preheating of the die is finished, the unfolded material is placed on the male die, the unfolded material is matched and positioned with positioning pins at two ends of the male die through positioning holes at two ends, the unfolded material is preheated, then the die is closed and pressure maintaining treatment is carried out, and after the forming is finished, the unfolded material is placed on a cutting die to be subjected to laser cutting to reach the required size of the part.
Furthermore, the part is a variable-curvature skin sheet metal part, the middle part of the part is concave, two ends of the part are upwarped, the total length of the part is 700-750 mm, and the maximum depth of the part along the hot-press forming direction is 200 mm.
Further, in the step one, the unfolding size of the part is calculated by adopting a finite element analysis method.
Furthermore, the specific operation process of calculating the expansion size of the part by the finite element analysis method comprises the following steps: and (3) introducing the part into finite element analysis software PAM-STAMP, dividing the unit size interval of the grid into 2-5 mm, calculating the outline of the expanded material by using a plate material back calculation module, putting the single side of the expanded material by 5mm on the basis, and adding plate material positioning holes.
Further, the mold was preheated to a temperature of 800 ℃ in step 2.
Further, in the step 2, the preheating temperature of the spread material is 800 ℃, and the preheating time is 15 minutes.
Further, the conditions of mold closing and pressure maintaining in the step 2 are as follows: the temperature is 800 ℃, the pressure is 1500N, and the dwell time is 15 minutes.
The invention has the following beneficial effects: the invention calculates the expansion size of the part by a finite element analysis method, and achieves the following optimization results by optimizing the die structure and changing the hot pressing mode of the part:
(1) the method effectively solves the problem of local wrinkles after the part is formed, and the maximum value of the deviation between the wrinkle part and the theoretical molded surface is only 0.1 mm;
(2) compared with the original two-step hot press forming process that hot press forming is often carried out after hot press forming, the one-step hot press forming method of the invention saves the cost of hot press forming time of the part by 50 percent while ensuring that the part achieves better forming effect, and reduces the time of 2 days needed by hot press forming of every 15 original parts to only 1 day; the equipment use and energy consumption cost is reduced by 50 percent, and the hot press forming cost is saved by 5000 yuan for every 15 pieces.
(3) The positioning holes are reserved on the spreading material, so that the large positioning in the hot-press forming process is facilitated, the subsequent laser cutting positioning is also facilitated, the subsequent laser cutting time of the part is reduced to 7 minutes per part from 15 minutes per part, the cutting time of each part is saved by 8 minutes, and the time and cost are saved by over 50 percent.
Drawings
FIG. 1 is a schematic structural view of a skin part;
FIG. 2 is a schematic view of the outline of the spread material of embodiment 1;
FIG. 3 is a schematic view showing the mounting of the spread material and the mold in the hot press molding in embodiment 1;
fig. 4 is a schematic view of the installation of the skin laser cutting and light-gathering cutting die obtained in embodiment 1;
FIG. 5 is a schematic diagram of meshing before part expansion;
FIG. 6 is a schematic view of the expanded shape of the part;
FIG. 7 is a schematic diagram illustrating the influence of the process margin of excessive blank materials on the complex stress of the molded surface area of a part in the conventional hot press forming of the part;
FIG. 8 is a schematic view of a stress analysis of a profile area of a finite element spread material of a part according to the size of a blank during hot press forming of the part.
Detailed Description
The experimental procedures used in the following examples are conventional unless otherwise specified. The materials, reagents, methods and apparatus used, unless otherwise specified, are conventional in the art and are commercially available to those skilled in the art.
Embodiment mode 1:
the skin I is a variable-curvature sheet metal part, the structure is shown in figure 1, the middle part is low-concave, two ends are upwarped, the total length of the part exceeds 700mm, and the maximum depth along the hot-press forming direction is nearly 200 mm.
Firstly, determining the outline of an unfolded material;
the method comprises the steps of calculating the size of an expanded material of a part according to the overall dimension of the finally formed part, determining the outline of the expanded material of the part, reserving positioning surfaces at two ends of the expanded material, designing positioning holes on the positioning surfaces, effectively getting rid of the complex stress influence of excessive process allowance on the position where folds are easy to appear in hot forming as shown in figure 2, facilitating the plate to be attached along with the profile in the hot forming process, designing plate positioning holes at two ends of the expanded material, namely, fixing holes of the hot-press formed plate and positioning holes for subsequent laser cutting of the part, and greatly improving the working efficiency of laser cutting of the part.
The specific operation process of calculating the expansion size of the part by the finite element analysis method comprises the following steps: and (3) introducing the part into finite element analysis software PAM-STAMP, dividing the unit size interval of the grid into 2-5 mm, calculating the outline of the unfolded material by using a plate material back calculation module as shown in figure 5, placing the single side of the unfolded material by 5mm on the basis as shown in figure 6, and adding plate material positioning holes. The expanded material and the blank material with larger process allowance are subjected to hot forming finite element analysis, as shown in fig. 8 and 7 respectively, and the results of comparing the stress distribution conditions of the blank material in the forming process show that the stress distribution of the blank material with larger process allowance in the hot forming process is much more complex, so that the material feeding of the part in the middle of the molded surface in the forming process is not smooth, and wrinkles are generated.
Secondly, installing a hot-press forming male die and a female die in a hot-press forming machine, ensuring that the female die is below an upper male die, and then preheating the die; after the preheating of the die is finished, the unfolded material is placed on the male die, the unfolded material is matched and positioned with the positioning pins at the two ends of the male die through the positioning holes at the two ends, the unfolded material is preheated, as shown in figure 3, the die is closed and pressure maintaining treatment is carried out, a hot pressing mode of one-step forming is adopted, and when parts are subjected to hot pressing, the female die is arranged above the male die, and a plate positioning structure is additionally arranged below the male die.
Wherein the preheating temperature of the die is 800 ℃, and the condition is met when the temperature is reached; preheating the spread materials at 800 ℃ for 15 minutes; the conditions of mold closing and pressure maintaining are as follows: the temperature is 800 ℃, the pressure is 1500N, and the dwell time is 15 minutes.
And thirdly, after the hot press forming is finished, placing the workpiece on a cutting die for laser cutting to reach the required size of the part, as shown in figure 4.
Claims (7)
1. A hot press forming method for a variable curvature skin sheet metal part is characterized by comprising the following steps:
step 1, determining the outline of an unfolded material;
calculating the size of an expanded material of the part according to the overall dimension of the finally formed part, determining the outline of the expanded material of the part, reserving positioning surfaces at two expanded ends, and designing positioning holes on the positioning surfaces;
step 2, hot-press forming of the spread material;
installing a hot-press forming male die and a female die in a hot-press forming machine, ensuring that the female die is below an upper male die, and then preheating the die; after the preheating of the die is finished, the unfolded material is placed on the male die, the unfolded material is matched and positioned with positioning pins at two ends of the male die through positioning holes at two ends, the unfolded material is preheated, then the die is closed and pressure maintaining treatment is carried out, and after the forming is finished, the unfolded material is placed on a cutting die to be subjected to laser cutting to reach the required size of the part.
2. The method for hot press forming of the variable-curvature skin sheet metal part according to claim 1, wherein the part is the variable-curvature skin sheet metal part, the middle part of the part is concave, two ends of the part are tilted upwards, the total length of the part is 700 mm-750, and the maximum depth of the part in the hot press forming direction is 200 mm.
3. The method for hot press forming of the variable curvature skin type sheet metal part according to claim 1, wherein in the first step, a finite element analysis method is adopted to calculate the unfolding size of the part.
4. The hot press forming method for the variable-curvature skin sheet metal part according to claim 3, wherein the specific operation process of calculating the unfolding size of the part by the finite element analysis method is as follows: and (3) introducing the part into finite element analysis software PAM-STAMP, dividing the unit size interval of the grid into 2-5 mm, calculating the outline of the expanded material by using a plate material back calculation module, putting the single side of the expanded material by 5mm on the basis, and adding plate material positioning holes.
5. The method for hot press forming of the variable curvature skin type sheet metal part according to claim 1, wherein the mold in the step 2 is preheated to a temperature of 800 ℃.
6. The hot press forming method of the variable curvature skin sheet metal part according to claim 1, wherein the preheating temperature of the spread material in the step 2 is 800 ℃, and the preheating time is 15 minutes.
7. The method for hot press forming of the variable-curvature skin sheet metal part according to claim 1, wherein the mold closing and pressure maintaining conditions in the step 2 are as follows: the temperature is 800 ℃, the pressure is 1500N, and the dwell time is 15 minutes.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011589262.8A CN112792200A (en) | 2020-12-28 | 2020-12-28 | Hot-press forming method for variable-curvature skin sheet metal part |
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| CN202011589262.8A CN112792200A (en) | 2020-12-28 | 2020-12-28 | Hot-press forming method for variable-curvature skin sheet metal part |
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| CN112792200A true CN112792200A (en) | 2021-05-14 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114434092A (en) * | 2021-12-15 | 2022-05-06 | 成都飞机工业（集团）有限责任公司 | Production method of aviation plate frame type complex parts |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109967619A (en) * | 2017-12-28 | 2019-07-05 | 航天海鹰(哈尔滨)钛业有限公司 | A kind of deep camber, variable cross-section titanium alloy covering hot forming mold |
| CN111687593A (en) * | 2020-05-25 | 2020-09-22 | 航天海鹰(哈尔滨)钛业有限公司 | Titanium alloy variable-curvature revolution solid structure sheet metal part forming process |
| CN111745027A (en) * | 2020-06-12 | 2020-10-09 | 陕西飞机工业（集团）有限公司 | Method for forming saddle-shaped skin part |
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- 2020-12-28 CN CN202011589262.8A patent/CN112792200A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109967619A (en) * | 2017-12-28 | 2019-07-05 | 航天海鹰(哈尔滨)钛业有限公司 | A kind of deep camber, variable cross-section titanium alloy covering hot forming mold |
| CN111687593A (en) * | 2020-05-25 | 2020-09-22 | 航天海鹰(哈尔滨)钛业有限公司 | Titanium alloy variable-curvature revolution solid structure sheet metal part forming process |
| CN111745027A (en) * | 2020-06-12 | 2020-10-09 | 陕西飞机工业（集团）有限公司 | Method for forming saddle-shaped skin part |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114434092A (en) * | 2021-12-15 | 2022-05-06 | 成都飞机工业（集团）有限责任公司 | Production method of aviation plate frame type complex parts |
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