阅读说明：本技术 一种大曲率金属厚板精确预成型方法 (Accurate preforming method for large-curvature metal thick plate ) 是由 张小波 岳维 邹震宇 李涛 邓文秀 张毅 郑伟涛 于 2021-06-28 设计创作，主要内容包括：本发明公开了一种大曲率金属厚板精确预成型方法,包括以下步骤：1)设计模具；2)将热压零件展开,形成毛坯料,并将毛坯料放置于模具内；3)通过Abqus有限元仿真；4)铸造模具；5)安装模具；6)根据模具设计预留的零件外形余量的展开数模,并根据厚度方向余量选择毛坯料规格；7)热压毛坯,进行零件的预成型过程,得到成型零件。本发明提出了一整套一种大曲率金属厚板精确预成型方法,能够整体成型厚度尺寸大的invar钢模板毛坯,且制造精度达到±2mm,大幅度提高了复材模具模板的厚度均匀性及保证了后期模板的气密性,从而满足了复材零件的热均匀性及孔隙率,大幅度降低了制造成本及生产制造周期。(The invention discloses a precise preforming method for a large-curvature metal thick plate, which comprises the following steps of: 1) designing a mould; 2) unfolding the hot-pressed part to form a blank, and placing the blank in a die; 3) simulating by an Abqus finite element; 4) casting a mold; 5) installing a mould; 6) designing an expansion digital model of the reserved part appearance allowance according to a die, and selecting the specification of the blank according to the allowance in the thickness direction; 7) and hot-pressing the blank, and performing a preforming process of the part to obtain a formed part. The invention provides a whole set of precise preforming method for a large-curvature metal thick plate, which can integrally form an invar steel template blank with large thickness and size, the manufacturing precision reaches +/-2 mm, the thickness uniformity of the composite material die plate is greatly improved, the air tightness of the later-stage die plate is ensured, the thermal uniformity and the porosity of a composite material part are met, and the manufacturing cost and the production and manufacturing period are greatly reduced.)

1. The precise preforming method for the large-curvature metal thick plate is characterized by comprising the following steps of:

(1) designing a mold: by utilizing the appearance of the part to be formed, the allowance of 3-5mm is reserved on the molded surface of the part, the allowance of 2-4mm is reserved on the non-working surface of the part, and the allowance of 40-80mm is reserved on the periphery of the part;

(2) unfolding the hot-pressed part to form a blank, and placing the blank in a die;

(3) simulating the damage value, the die attaching degree and the pressure of the hot-pressed part through Abqus finite element simulation, and correcting the pressing die according to the simulation result;

(4) casting a mould, reserving 30mm allowance on the surface of a casting, measuring a molded surface after manufacturing, and using the mold with a tolerance of +/-0.1 mm;

(5) installing a mould;

(6) designing an expansion digital model of the reserved part appearance allowance according to a die, and selecting the specification of the blank according to the allowance in the thickness direction;

(7) and hot-pressing the blank, and performing a preforming process of the part to obtain a formed part.

2. The method for precisely performing the thick metal plate with large curvature according to claim 1, wherein the die designed in step (1) comprises an upper die and a lower die, the upper portion of the upper die is fixedly connected with a universal die holder, and guide posts, guide sliding blocks and stop blocks for fixing blank parts during part forming are arranged on two sides between the upper die and the lower die.

3. The method for precisely preforming a thick plate of high-curvature metal according to claim 2, wherein the upper and lower dies are made of cast iron or steel, and are provided with lightening grooves, the thickness of the reinforcing rib is 60-100mm, and the upper die is provided with a U-shaped groove for positioning with a machine tool.

4. The method of claim 2, wherein the general die holder is made of Q235A, the two length directions of the general die holder are dovetail structures, the size of the general die holder matches the size of the press, and the general die holder is connected with the upper die by screws.

5. The method for precisely preforming a thick plate of high-curvature metal according to claim 2, wherein the step (5) of installing the mold includes installing a universal die holder of the upper mold on the upper mold, installing the universal die holder on the press,

the lower die of the pressing die is placed at the corresponding position of the platform, and the lower die is not fixed on the platform and can be kept to move freely on the platform of the pressing machine.

6. The method for precisely preforming the thick plate of large curvature metal according to claim 2, wherein in the step (7), the blank is hot pressed, and the specific process of preforming the part is as follows:

(7.1) heating the blank to 650 ℃ at the speed of 10 ℃/min, preserving heat for 1h, heating to 900 +/-50 ℃ at the speed of 100 ℃/h, and preserving heat for 30-60 min;

(7.2) rapidly moving the blank to a lower die of a pressing die, roughly positioning by using a material blocking block, pressing down an upper die, ensuring that the temperature of the part is 800 +/-50 ℃ and the pressure is 3500 plus 6000 tons during pressing down, keeping the pressure for 5-10 minutes after the upper die is moved to a theoretical position, and releasing the pressure of a press when the part is cooled to be below 300 ℃;

(7.3) disassembling the universal die holder, wherein the upper die cannot be moved in the period, cooling is carried out for more than 1h, and when the temperature of the part is reduced to be lower than 100 ℃, the part can be taken out.

7. The precise preforming method for the thick metal plate with large curvature according to any one of claims 1 to 6, characterized in that in the step (3), the thickness of the local unformed part of the template is less than 15mm through Abqus finite element simulation, the local unformed part of the template can be smoothly transited, and the later stage is compensated by repair welding; when the simulation pressure is more than 5000 tons, whether corners exist on the molded surface of the pressing die or not needs to be considered, so that local premature contact is caused, the parts cannot be lined, and the parts are locally repaired.

8. The method for precisely performing large-curvature thick metal plate according to any one of claims 1 to 6, wherein in the step (7), after the hot-pressed part is cooled, the mold is lifted, the top of the part is supported by a steel bar to be attached to the pressing mold, the steel bar and the hot-pressed part are subjected to spot welding, and subsequent work is performed.

Technical Field

The invention relates to the technical field of manufacturing of aviation equipment, in particular to a precise preforming method for a large-curvature metal thick plate.

Background

The advanced composite material part is widely applied to the production and the manufacture of a new generation of fighter plane due to the advantages of light weight, corrosion resistance, strong designability and the like. In the manufacturing process of the composite material die, the die profile is determined by the shape of the part, and the shape of the part tends to have the characteristics of large curvature, deep cavity and the like along with the improvement of designability of the composite material part. In order to ensure the overall quality of the composite material part, the composite material mold template generally has the requirements of thermal uniformity and air tightness. In order to ensure the integral structural strength, the thickness of the template of the composite material mould forming part is generally 12-16mm, the tolerance of the thickness of the template of the composite material mould is required to be generally +/-2 mm in order to ensure the thermal uniformity of the composite material part in the forming process, and in order to ensure the air tightness of the composite material mould, the template of the mould is required to be integrally formed as much as possible, so that the welding process is avoided as much as possible, and the air tightness risk caused by welding defects is reduced.

To ensure the forming precision of the composite material part (the thermal expansion coefficient of the composite material part is lower by about 3 x 10)^-6v./deg.C), Invar steel has very small coefficient of thermal expansion of 1.6 x 10 at-80 deg.C to 230 deg.C^-6V. (1.2 x 10 for ordinary steel)^-5/° c), and is therefore widely used in the manufacture of large, important, complex composite molds. At present, domestic Invar steel is basically imported from foreign countries and is limited by the production size of foreign companies, the thickness of a common Invar steel raw material is 9-30mm, and the price is very expensive and 150 yuan/kg.

In the prior art, a template with small curvature change is formed in a mode of local bending and block welding in the manufacturing process of a composite material mold, and the difference between the preformed template and the theory is more than +/-5-6 mm, but no effective forming scheme exists for forming a thick high-curvature Invar steel template, and no effective high-precision forming precedent exists in China particularly for forming the composite material mold template with large curvature and deep cavity. Due to the technical bottleneck limitation, the installation application of a composite part on a certain part of a certain type of airplane in China has not been realized for many years.

Disclosure of Invention

The invention aims to provide the precise preforming method of the large-curvature metal thick plate, which improves the preforming precision of the profile plate, reduces numerical control machining amount, ensures the air tightness and the wall thickness uniformity in the forming process of a composite material die in the later period, and is particularly suitable for preforming the Invar composite material die profile plate with a complex curved surface.

The invention is realized by the following technical scheme: a precise preforming method for a large-curvature metal thick plate comprises the following steps:

(1) designing a mold: by utilizing the appearance of the part to be formed, the allowance of 3-5mm is reserved on the molded surface of the part, the allowance of 2-4mm is reserved on the non-working surface of the part, and the allowance of 40-80mm is reserved on the periphery of the part;

(2) unfolding the hot-pressed part to form a blank, and placing the blank in a die;

(3) simulating the damage value, the die attaching degree and the pressure of the hot-pressed part through Abqus finite element simulation, and correcting the pressing die according to the simulation result;

(4) casting a mould, reserving 30mm allowance on the surface of a casting, measuring a molded surface after manufacturing, and using the mold with a tolerance of +/-0.1 mm;

(5) installing a mould;

(6) designing an expansion digital model of the reserved part appearance allowance according to a die, and selecting the specification of the blank according to the allowance in the thickness direction;

(7) and hot-pressing the blank, and performing a preforming process of the part to obtain a formed part.

In order to better realize the method of the invention, the die designed in the step (1) further comprises an upper die and a lower die, the upper part of the upper die is fixedly connected with a universal die holder, and a guide pillar, a guide slide block and a material stop block for fixing a blank part during part forming are arranged on two sides between the upper die and the lower die.

In order to better realize the method of the invention, the upper die and the lower die are made of cast iron or cast steel, the upper die and the lower die are provided with lightening grooves, the thickness of the reinforcing rib is 60-100mm, and the upper die is provided with a U-shaped groove for positioning with a machine tool.

In order to better realize the method of the invention, the universal die holder is made of Q235A, the two length directions of the universal die holder are dovetail structures, the size of the universal die holder is matched with that of the press, and the universal die holder is connected with the upper die by screws.

In order to better implement the method of the present invention, the step (5) of installing the die includes installing the universal die holder of the upper die on the upper die, and installing the universal die holder on the press. The lower die of the pressing die is placed at the corresponding position of the platform, and the lower die is not fixed on the platform and can be kept to move freely on the platform of the pressing machine.

In order to better implement the method of the present invention, further, in the step (7), the blank is hot-pressed, and the specific process of performing the preforming of the part is as follows:

(7.1) heating the blank to 650 ℃ at the speed of 10 ℃/min, preserving heat for 1h, heating to 900 +/-50 ℃ at the speed of 100 ℃/h, and preserving heat for 30-60 min;

(7.2) rapidly moving the blank to a lower die of a pressing die, roughly positioning by using a material blocking block, pressing down an upper die, ensuring that the temperature of the part is 800 +/-50 ℃ and the pressure is 3500 plus 6000 tons during pressing down, keeping the pressure for 5-10 minutes after the upper die is moved to a theoretical position, and releasing the pressure of a press when the part is cooled to be below 300 ℃;

(7.3) disassembling the universal die holder, wherein the upper die cannot be moved in the period, cooling is carried out for more than 1h, and when the temperature of the part is reduced to be lower than 100 ℃, the part can be taken out.

In order to better realize the method of the invention, further, in the step (3), the thickness of the template which can not be formed locally is smaller than 15mm through Abqus finite element simulation, the template can be smoothly transited, and the later stage is compensated by adopting a repair welding mode; when the simulation pressure is more than 5000 tons, whether corners exist on the molded surface of the pressing die or not needs to be considered, so that local premature contact is caused, the parts cannot be lined, and the parts are locally repaired.

In order to better implement the method of the invention, further, in the step (7), after the hot-pressed part is cooled, the mould is lifted, the top of the part is supported by a steel bar to be attached to a pressing mould, the steel bar and the hot-pressed part are spot-welded, and the subsequent work is carried out.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the invention provides a whole set of precise preforming method for a large-curvature metal thick plate, which can integrally form an invar steel template blank with large thickness and size, the manufacturing precision reaches +/-2 mm, the thickness uniformity of a composite material die plate is greatly improved, and the air tightness of a later-stage die plate is ensured, so that the thermal uniformity and the porosity of a composite material part are met, and the manufacturing cost and the production and manufacturing period are greatly reduced;

(2) the invention solves the problem of the preforming of the panel in the manufacturing process of the composite material die due to the influence of the size and the air tightness of the material, greatly improves the preforming precision of the panel, reduces the numerical control processing amount and ensures the air tightness and the wall thickness uniformity in the later forming process of the composite material die;

(3) the invention is used for preforming the composite material mould type panel, is particularly suitable for preforming the Invar material composite material mould type panel with a complex curved surface, and is suitable for wide popularization and application.

Detailed Description

The present invention will be described in further detail with reference to the following examples for the purpose of making clear the objects, process conditions and advantages of the present invention, but the embodiments of the present invention are not limited thereto, and various substitutions and modifications can be made according to the common technical knowledge and the conventional means in the art without departing from the technical idea of the present invention described above, and the specific examples described herein are only for explaining the present invention and are not intended to limit the present invention.

Example 1:

the technical scheme of the die design of the embodiment is as follows: and extracting the inner and outer molded surfaces of the mold template, wherein the inner molded surface (the side contacted with the frame) is reserved with 3mm allowance, the outer molded surface is reserved with 5-6mm allowance, the height of the template part in the length direction is approximately leveled, the part is leveled, so that the Z direction of the part has no negative angle, the appearance of the part in the width direction is reserved with 40-60mm allowance, and the part in the length direction is placed with 150-200mm allowance. And (3) after the extracted outer profile is extended by 40-60mm in an outward inserting way, extending the outer profile in an outward inserting way or stretching the outer profile along a certain angle (the angle is not less than the minimum angle of the original curved surface), and forming a lower die body of the pressing die by utilizing the designed curved surface cutting boss. And offsetting the thickness of the hot-pressed blank according to the molded surface of the lower die body of the pressing die to form the molded surface of the upper die of the pressing die.

Example 2:

the design scheme of the stamper of this example is: after the die pressing design is completed, the hot-pressed part is unfolded to form a blank, the blank is placed on the lower die, and the material blocking blocks are respectively arranged in the length direction and the width direction of the part and used for fixing the blank part during part forming.

Example 3:

the design scheme of the stamper of this example is: after the design of the pressing die is finished, lugs with the thickness of 60-100 and the width of 100-150mm are widened at two ends of the upper die part, and U-shaped grooves which are uniformly spaced and fixed are arranged on the lugs. And designing a universal die holder according to the dovetail size of the hot press, wherein the dovetail part of the die holder is matched with the hot press, a step with the height of 70mm is arranged on the die holder, and U-shaped grooves with the same interval are arranged according to the positions of the U-shaped grooves on the upper die. The length of the universal U-shaped groove covers the width difference of an upper die of a common deep cavity die.

Example 4:

the design scheme of the stamper of this example is: the moulding-die adopts cast steel material, sets up between the upper and lower moulding-die and leads the slider and be used for the coarse positioning of upper and lower moulding-die in the four corners position, sets up two guide pillars at width both ends for the accurate positioning of upper and lower moulding-die.

Example 5:

the precise preforming method for the large-curvature metal thick plate comprises the following steps: simulating the damage value, the die attaching degree and the pressure of the hot-pressed part by Abqus finite element simulation, and correcting the pressing die according to the simulation result. The thickness of the local unformed template is less than 15mm, the template can be smoothly transited, and the later repair welding mode is adopted for compensation. At pressures above 5000 tons, consideration is given to the presence of corners in the die surface, resulting in localized premature contact, failure to align parts, and localized modification of parts.

Example 6:

the precise preforming method for the large-curvature metal thick plate in the embodiment comprises the following steps: and after the design of the upper and lower pressing dies is finished, the upper and lower pressing dies are respectively cast, the allowance of 30mm is reserved on the surface of a casting, molded surfaces are respectively measured after the casting is finished, and the tolerance of +/-0.1 mm can be used.

Example 7:

the precise preforming method for the large-curvature metal thick plate in the embodiment comprises the following steps: after the die is manufactured, the universal die holder of the upper die is firstly installed on the upper die, and the universal die holder is installed on the press. The lower die of the pressing die is placed at the corresponding position of the platform, and the lower die is not fixed on the platform and can be kept to move freely on the platform of the pressing machine.

Example 8:

the hot pressing scheme of the parts of the embodiment is as follows: the template blank is made of Invar, an expansion digital model of the shape allowance of the part reserved according to die pressing design is adopted, and the specification of the blank is selected according to the allowance in the thickness direction (3 mm +6mm =9 mm).

Example 9:

the hot pressing scheme of the part in the embodiment is that a template blank is heated to 650 ℃ at the speed of 10 ℃/min, the temperature is maintained for 1h, the template blank is heated to 900 +/-50 ℃ at the speed of 100 ℃/h, the temperature is maintained for 30-60 min, the template blank is quickly moved to a lower die of a pressing die, a material blocking block is used for coarse positioning, the upper die is pressed downwards (the temperature of the part is ensured to be 800 +/-50 ℃ during pressing), the pressure is 3500 plus 6000 tons, the pressure is maintained for 5-10 min after the upper die is moved to the theoretical position, and the pressure of the press is released when the part is cooled to below 300 ℃. And (3) disassembling the universal die holder (the upper die cannot be moved in the period), cooling for more than 1h, and taking out the part when the temperature of the part is reduced to be below 100 ℃. After the hot-pressed part required by the embodiment is cooled, the top of the upper die part of the pressing die is lifted to be supported by a steel bar until the top of the upper die part is attached to the pressing die, the steel bar and the hot-pressed part are spot-welded, and subsequent work is carried out.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.