Die and forming method for hot pressing forming of titanium alloy deep drawing part

Abstract

The invention provides a die for hot pressing forming of a titanium alloy deep drawing part and a forming method, and belongs to the technical field of metal pressure machining. The problem that the surface of the titanium alloy deep drawing part is prone to being scratched in the hot forming process is solved. Comprising an upper die and a lower die, the upper die is provided with an edge rounded corner area making contact with a plate, the edge rounded corner area is provided with a plurality of point contact molded surfaces distributed at intervals, and the point contact molded surfaces are of smooth protruding structures protruding out of the surface of a base body of the edge rounded corner area. The method is mainly used for controlling the surface scratch defect in the hot pressing forming process of the titanium alloy deep drawing part.

Description

Technical Field

[0001] This invention belongs to the field of metal pressure processing technology, and in particular relates to a mold and forming method for hot pressing of deep-drawn titanium alloy parts. Background Technology

[0002] Titanium and titanium alloys, due to their high specific strength, good heat resistance, and excellent corrosion resistance, have been widely used in aerospace, chemical equipment, shipbuilding, and other industrial fields. In particular, thin-walled deep-drawn titanium alloy structural parts are important components of high-end equipment such as aircraft and engines. These deep-drawn titanium alloy structural parts are mainly manufactured using hot pressing. In this process, heated titanium alloy sheets undergo plastic deformation under the action of a die to form the desired part shape. However, titanium alloys have high chemical reactivity at high temperatures and relatively high hardness, making them prone to adhesion and friction with the die surface during hot forming, resulting in severe scratches, abrasions, and other defects on the part surface. These surface defects not only affect the final appearance quality of the part but can also become stress concentration points, posing a potential threat to the fatigue strength and service life of the part, and may even lead to part scrapping, increasing production costs. In existing hot pressing technology, to facilitate the flow of sheet metal into the die cavity, the area on the die that first contacts the edge of the sheet metal and creates relative sliding is usually designed as a continuous, large-radius circular arc transition surface. While this design facilitates material flow, it essentially creates a large surface area of ​​contact between the entire side of the sheet metal and the rounded corners of the mold. Under high temperature and high pressure forming conditions, this large-area contact leads to intense sliding friction, which is one of the main causes of surface scratches on titanium alloy parts. The industry typically attempts to alleviate this problem by optimizing lubricants (such as spraying boron nitride), but the effects are limited, and the scratch problem remains fundamentally unresolved. Summary of the Invention

[0003] In view of this, the present invention aims to provide a mold and forming method for hot pressing of titanium alloy deep-drawn parts, so as to solve the technical problem that scratches are easy to occur on the surface of titanium alloy deep-drawn parts during hot forming.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a mold for hot pressing of titanium alloy deep-drawn parts, comprising an upper mold and a lower mold, wherein the upper mold is provided with an edge rounded corner area that contacts the sheet metal, and the edge rounded corner area is provided with a plurality of spaced point contact surfaces, wherein the point contact surfaces are smooth protrusions protruding from the substrate surface of the edge rounded corner area.

[0005] Furthermore, the point contact surfaces are evenly spaced along the material feeding direction on the rounded corner area of ​​the upper mold edge.

[0006] Furthermore, the upper mold has an edge rounded corner area with a radius of 10mm, and the point contact surfaces are set on the 10mm edge rounded corner area, and there are four point contact surfaces.

[0007] Furthermore, the cross-sectional shape of the point contact surface is an isosceles triangle with a smooth vertex, the base width of the isosceles triangle is 40mm, and the overall arc surface of the isosceles triangle matches the arc of the edge rounded corner area.

[0008] Furthermore, the isosceles triangle has a 5mm radius rounded corner at its vertices and a 2mm radius rounded corner on its two sides, excluding the base.

[0009] A forming method for hot pressing of deep-drawn titanium alloy parts, using a mold for hot pressing of deep-drawn titanium alloy parts, includes the following steps: S1: Cut the sheet material, remove burrs, oil stains and impurities, and spray boron nitride onto the surface of the sheet material; S2: Clean the surface of the point contact surface, remove impurities, and spray boron nitride. Then install the upper and lower molds in the center of the hot press worktable. S3: Use a soft aluminum shim placed on the lower mold to adjust the gap between the upper and lower molds; S4: Place the pre-treated sheet material on the lower mold, heat it to the forming temperature, and then control the upper mold to press down so that the sheet material forms point contact sliding friction with the point contact surface of the rounded corner area of ​​the upper mold during the forming process. At the same time, apply forming pressure and keep it warm and pressurized. S5: After the forming process is completed, control the upper mold to rise. After it is no longer in contact with the part, lift it up and remove the formed part.

[0010] Furthermore, in S1, the blanking is done by laser cutting, and the thickness of the sheet material is 1.5mm.

[0011] Furthermore, in S2, the surface of the point contact surface is sanded with sandpaper to make the surface of the point contact surface smooth.

[0012] Furthermore, in S3, when the thickness of the soft aluminum pad is insufficient, the gap is adjusted by supplementing with auxiliary paper.

[0013] Furthermore, in S4, the molding temperature is 750~780℃.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention transforms the large-area surface contact sliding friction between the traditional mold and the blank into discrete point contact sliding friction by setting multiple spaced point contact surfaces in the rounded corner area of ​​the upper mold. This greatly reduces the total contact area and relative sliding friction resistance between the blank and the mold surface during the flow process, thereby significantly reducing the probability and severity of scratches, scoring and other defects on the surface of titanium alloy parts from the source, and greatly improving the first-pass yield and surface quality of the products. 2. The present invention effectively controls scratch defects due to the point contact structure, reduces the scrap rate of parts caused by surface quality problems, directly saves raw material costs and energy and labor time consumed by repeated processing, and also reduces the dependence on subsequent polishing, grinding and other finishing processes and labor costs, avoiding mold rework or scrap due to severe scratches, and overall reducing the total production cost of titanium alloy deep drawing structural parts. 3. The present invention sets the point contact surfaces at equal intervals along the material feeding direction of the blank, which can ensure that the edge of the blank is subjected to uniform force during the forming process, avoid the phenomenon of poor material flow or stress concentration caused by sudden changes in local friction force, and help to obtain formed parts with higher dimensional accuracy and more uniform wall thickness distribution, thereby improving the consistency and reliability of the product. 4. The point contact surface of the present invention adopts an isosceles triangular cross section with a smooth vertex, and the vertex and sides are rounded so that these protruding structures not only reduce the contact area, but their smooth transition geometry can also better guide the blank to flow smoothly into the mold cavity, avoiding stress concentration and secondary scratches on the blank that may be caused by sharp corners, and further optimizing the friction reduction effect. 5. This invention can be directly integrated during the design and manufacturing of new molds, and it is also easy to implement through rework on existing molds, resulting in low modification costs and convenient implementation. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the axial structure of a mold for hot pressing of titanium alloy deep-drawn parts according to the present invention. Figure 2 This is a first-view axial side structural diagram of the upper die of a mold for hot pressing of titanium alloy deep-drawn parts according to the present invention. Figure 3 This is a second-view axial side structural diagram of the upper die of a mold for hot pressing of titanium alloy deep-drawn parts according to the present invention.

[0016] In the picture: 1. Upper mold; 2. Lower mold; 3. Point contact surface; 4. Edge rounded corner area. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0018] Detailed implementation method: See Figure 1-3 This embodiment describes a mold for hot pressing titanium alloy deep-drawn parts, comprising an upper mold 1 and a lower mold 2. The upper mold 1 has a rounded corner region 4 that contacts the sheet metal. The rounded corner region 4 has multiple spaced-apart point contact surfaces 3, which are smooth protrusions extending beyond the surface of the base material of the rounded corner region 4. The core improvement of this mold for hot pressing titanium alloy deep-drawn parts lies in the structure of the rounded corner region 4 in contact with the sheet metal. When the material flows into the die cavity during the deep drawing process, it first comes into contact with and experiences intense sliding friction at this part. Traditional dies have a continuous, smooth arc surface at this point, which is in surface contact with the sheet material and is prone to scratches. In this application, multiple raised point contact surfaces 3 are made on the substrate surface in the rounded corner area 4. These point contact surfaces 3 are smooth raised structures with a height slightly higher than the substrate surface, so that the sheet material only contacts these raised points when flowing, thereby transforming the large-area surface contact sliding friction into discrete point contact sliding friction, effectively reducing frictional resistance and the risk of scratches.

[0019] The point contact surfaces 3 are evenly spaced on the rounded corner area 4 of the upper mold 1 along the material feeding direction. In order to ensure that the material is subjected to uniform force during the feeding process and to avoid local stress concentration or poor feeding caused by uneven point contact distribution, the point contact surfaces 3 are arranged at equal intervals along the material feeding direction. The specific spacing can be adjusted according to the size and material characteristics of the material.

[0020] The upper mold 1 has an edge rounded corner area 4 with a radius of 10mm. The point contact surface 3 is set on the 10mm edge rounded corner area 4. There are four point contact surfaces 3. The edge rounded corner area 4 of the upper mold 1 has a specific rounded corner radius, namely 10mm. This ensures that the sheet material can flow in smoothly while providing sufficient space and a suitable base surface for the processing of the point contact surface 3. The four point contact surfaces 3 can achieve a good balance between effectively reducing the contact area and ensuring the forming stability.

[0021] The cross-sectional shape of the point contact surface 3 is an isosceles triangle with a smooth vertex. The base width of the isosceles triangle is 40mm. The overall arc surface of the isosceles triangle matches the arc of the edge rounded corner area 4, ensuring that the point contact surface 3 can be naturally integrated into the original structure of the mold without causing abrupt obstruction to the flow of materials.

[0022] The isosceles triangle has a 5mm radius rounded corner at its vertex and a 2mm radius rounded corner on its two sides (excluding the base). The 5mm radius rounded corner at the vertex of the triangle facing the material feeding direction helps guide the material to smoothly transition onto the point contact surface 3. The 2mm radius rounded corner on the two sides of the isosceles triangle (excluding the base) is designed to eliminate sharp corners and make the contact and separation between the point contact surface 3 and the material smoother.

[0023] A forming method for hot pressing of deep-drawn titanium alloy parts, using a mold for hot pressing of deep-drawn titanium alloy parts, includes the following steps: S1: Cut the sheet material, remove burrs, oil stains and impurities, and spray boron nitride on the surface of the sheet material. The sheet material is TA15 titanium alloy. Use a laser cutting machine to cut the material. Laser cutting can ensure the quality of the cut and reduce burrs. After cutting, use fine sandpaper or special grinding tools to carefully remove the burrs and spatter generated by the cutting edge. Then, use solvents such as acetone or alcohol to clean the surface of the sheet material to thoroughly remove oil stains, fingerprints and other contaminants. The coating should be uniform, without missed spraying or accumulation, and form a complete lubricating film. S2: Clean the surface of the point contact surface 3, remove impurities, and spray boron nitride. Spray a layer of boron nitride lubricant evenly on the cleaned mold surface area, especially the point contact surface 3. Install the upper mold 1 and the lower mold 2 in the center of the hot press worktable. Hoist the pre-treated upper mold 1 and lower mold 2 to the center area of ​​the hot press worktable. Use the positioning structure on the mold or use measuring tools to align them to ensure that the upper mold 1 and lower mold 2 are accurately aligned when the mold is closed, and avoid uneven load. S3: Place a soft aluminum pad on the lower mold 2, adjust the gap between the upper mold 1 and the lower mold 2, place a soft aluminum pad with a thickness of 1.5mm at the predetermined position on the surface of the lower mold 2, and slowly drive the hot press to press the upper mold down until it contacts the soft aluminum pad. Ensure that the gap is uniform by observation or measurement. S4: Place the pre-treated sheet material on the lower mold 2, heat the mold and sheet material together, and after heating to the forming temperature, control the upper mold 1 to press down, so that the sheet material forms point contact sliding friction with the point contact surface 3 of the rounded corner area 4 of the upper mold 1 during the forming process. After the temperature reaches the set value and is kept evenly, start the press and control the upper mold 1 to press down slowly at a speed of 0.5 mm / s, smoothly contact the sheet material, apply forming pressure and keep it warm and pressurized. During the pressing process of the upper mold 1, the edge of the sheet material begins to flow into the mold cavity. The contact between the sheet material and the mold is not the traditional contact of the entire arc surface, but only contact with multiple point contact surfaces 3 set on the rounded corner area 4 of the upper mold 1. The surface contact sliding friction is transformed into point contact sliding friction, which significantly reduces the total contact area and friction force, thereby fundamentally reducing the probability and degree of scratches. After the mold is closed, apply a forming pressure of 300 kN and keep it warm and pressurized for 8~10 minutes under this pressure to allow the material to fully plastically deform and solidify. S5: After the forming is completed, control the upper mold 1 to rise slowly at an initial speed of 0.5 mm / s. After it is no longer in contact with the part, lift it up and take out the formed part.

[0024] In S1, the blanking is done by laser cutting, and the thickness of the sheet is 1.5mm. The thickness of the sheet corresponds directly to the 1.5mm thick soft aluminum shim used when adjusting the mold gap, which ensures the accuracy of the gap adjustment.

[0025] In S2, sanding the surface of the point contact surface 3 with sandpaper makes the surface of the point contact surface 3 smooth, which can further reduce the probability of scratches during the point contact sliding friction process.

[0026] In S3, when the thickness of the soft aluminum shim is insufficient, the gap is adjusted by supplementing with auxiliary paper. When the thickness of the soft aluminum shim is slightly insufficient and the mold cannot achieve the best closing state, clean and flat paper can be used as a supplementary shim, placed under the soft aluminum shim for fine adjustment to ensure that the gap is accurate.

[0027] In S4, the forming temperature is 750~780℃. Within this temperature range, TA15 titanium alloy has good plasticity and low deformation resistance, which is conducive to deep drawing. At the same time, in combination with the structure of point contact surface 3, it can most effectively control the generation of scratch defects.

[0028] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A die for hot pressing of deep-drawn titanium alloy parts, comprising an upper die (1) and a lower die (2), characterized in that: The upper mold (1) is provided with an edge rounded corner area (4) that contacts the sheet metal. The edge rounded corner area (4) is provided with a plurality of spaced point contact surfaces (3). The point contact surfaces (3) are smooth protrusions that protrude from the base surface of the edge rounded corner area (4).

2. The mold for hot pressing of deep-drawn titanium alloy parts according to claim 1, characterized in that: The point contact surface (3) is set at equal intervals along the material feeding direction on the edge rounded corner area (4) of the upper mold (1).

3. The mold for hot pressing of deep-drawn titanium alloy parts according to claim 1, characterized in that: The upper mold (1) has an edge rounded corner area (4) with a radius of 10 mm. The point contact surface (3) is set on the 10 mm edge rounded corner area (4). There are four point contact surfaces (3).

4. A die for hot pressing of deep-drawn titanium alloy parts according to claim 1, characterized in that: The cross-sectional shape of the point contact surface (3) is an isosceles triangle with a smooth vertex. The width of the base of the isosceles triangle is 40mm. The overall arc surface of the isosceles triangle matches the arc of the edge rounded corner area (4).

5. A die for hot pressing of deep-drawn titanium alloy parts according to claim 1, characterized in that: The isosceles triangle has a 5mm radius rounded corner at its vertex and a 2mm radius rounded corner on its two sides, excluding the base.

6. A forming method for hot pressing of titanium alloy deep-drawn parts, using the mold for hot pressing of titanium alloy deep-drawn parts according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Cut the sheet material, remove burrs, oil stains and impurities, and spray boron nitride onto the surface of the sheet material; S2: Clean the surface of the point contact surface (3), remove impurities, and spray boron nitride. Install the upper mold (1) and the lower mold (2) at the center of the hot press workbench. S3: Place a soft aluminum shim on the lower mold (2) and adjust the gap between the upper mold (1) and the lower mold (2); S4: Place the pre-treated sheet on the lower mold (2), heat it to the forming temperature, and then control the upper mold (1) to press down so that the sheet forms point contact sliding friction with the point contact surface (3) of the rounded corner area (4) of the upper mold (1) during the forming process. At the same time, apply forming pressure and keep warm and pressurized. S5: After the forming is completed, control the upper mold (1) to rise, and lift it after it is no longer in contact with the part, and take out the formed part.

7. A forming method for hot pressing of deep-drawn titanium alloy parts according to claim 6, characterized in that: In S1, the blanking is done by laser cutting, and the thickness of the sheet material is 1.5mm.

8. A forming method for hot pressing of deep-drawn titanium alloy parts according to claim 6, characterized in that: In S2, the surface of the point contact surface (3) is sanded with sandpaper to make the surface of the point contact surface (3) smooth.

9. A forming method for hot pressing of deep-drawn titanium alloy parts according to claim 6, characterized in that: In S3, when the thickness of the soft aluminum pad is insufficient, the gap is adjusted by supplementing with auxiliary paper.

10. A forming method for hot pressing of deep-drawn titanium alloy parts according to claim 6, characterized in that: In S4, the molding temperature is 750~780℃.

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