A method of storing and thermoforming a titanium alloy cap

Abstract

The application discloses a kind of for titanium alloy cap storage thermoforming method, using disc-shaped with center hole blank and two different hot stretch forming die, first by first set of hot stretch forming die obtains the profile feature of cylindrical surface section and spherical surface section of cap, again by second set of hot stretch forming die obtains the rib feature on spherical surface section. Among them, the first set of hot stretch forming die forming process includes two stages sequentially, when first stage hot stretch, no pressure edge force is applied, blank is in the state of no tensile deformation enters the mold storage, and spherical storage bag is formed in the center area of blank, when second stage hot stretch, pressure edge force is applied, and the profile of cylindrical surface section and the profile of spherical surface section are stretched and formed in the mold.The present application effectively solves the tearing and thinning problem in the processing of titanium alloy cap, and greatly improves the processing qualification rate.

Description

Technical Field

[0001] This invention belongs to the field of special processing technology for titanium alloys, and specifically relates to a thermoforming processing method for titanium alloy caps. Background Technology

[0002] like Figure 1 The image shows a type of hood used on an aircraft engine. The main body of the hood component is a cylindrical-to-spherical segment structure. The diameter of the cylindrical segment is Φ150mm, and the height is approximately 100mm. The depth-to-diameter ratio is greater than 0.6, and a circular hole is opened at the center of the head of the component. Eight ribs of varying lengths are evenly distributed around the perimeter of the hole. The final thinning requirement for the component is greater than 0.6t (t refers to the original thickness of the component sheet). The thinning of the component is related to the forming accuracy of the surface, and the surface of the component is complex.

[0003] Due to the high aspect ratio of the part, its titanium alloy construction, and the dense ribs on its head, controlling the part's wall thickness is challenging. Traditional hot stretching processes result in excessive material deformation, making it impossible to guarantee the correct thickness. This leads to material thinning at the highest point of the spherical section, failing to meet the final application requirements. Therefore, it is necessary to research a new thermoforming method for the cap to mass-produce similar parts. Summary of the Invention

[0004] The present invention aims to provide a material storage thermoforming method for titanium alloy cap covers, which effectively solves the tearing and thinning problems in the processing of titanium alloy cap covers, and greatly improves the processing qualification rate, thereby enabling mass production of titanium alloy cap covers.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for thermoforming a titanium alloy cap, the cap mainly composed of a cylindrical section and a spherical section, wherein one axial end face of the cylindrical section is open, and the other axial end face is closed through the spherical section, and the surface of the spherical section is evenly distributed with multiple ribs of varying lengths. The thermoforming method includes the following steps:

[0007] Step 1: Prepare raw materials by processing a disc-shaped plate with a central hole as the raw material.

[0008] Step 2, the first forming: The raw material from Step 1 is hot-stretched to obtain cylindrical and spherical segments. The hot-stretching process is divided into two sequential stages. In the first stage, no blank holder force is applied during hot stretching (i.e., a clamping force is applied to the annular edge of the raw material). The raw material enters the hot stretching mold without stretching deformation and is stored, forming a spherical storage bag in the center area of ​​the raw material. In the second stage, blank holder force is applied during hot stretching, and the cylindrical and spherical segments are stretched and formed in the hot stretching mold.

[0009] Step 3, second forming: using a hot stretching forming method, all the ribs are machined on the surface of the spherical segment obtained in step 2.

[0010] As one approach, in step one, the size of the disc-shaped material with the central opening is calculated by converting the volume of the titanium alloy cap part into the volume of the material using the equal volume method.

[0011] As one approach, in step two, the amount of pressure applied during the first stage of hot stretching is less than the amount of pressure applied during the second stage of hot stretching.

[0012] As one approach, in step two, there is at least one part rotation operation during both the first and second stage hot stretching processes, causing the stretching part in the hot stretching die to rotate relative to the hot stretching die.

[0013] As one approach, in step two, before the first stage of hot stretching, a lubricant and a thermoforming protective coating are sprayed onto the surface of the raw material.

[0014] As one approach, in step two, after the second stage of hot stretching, a flange edge with a transition fillet is formed at the open end of the cylindrical section.

[0015] As one embodiment, in step two, the hot stretching die includes a lower template, a first concave die, a first convex die, and a support plate. The first convex die is mounted on the lower template and its surface includes an inner forming surface of a cylindrical segment and an inner forming surface of a spherical segment. The support plate is an annular piece placed on the lower template and has a positioning pin. The first convex die is placed in the inner annular hole of the support plate. The lower template also has a push rod hole that penetrates the lower template and points to the support plate. The surface of the first concave die includes an outer forming surface of a cylindrical segment, an outer forming surface of a spherical segment, and an annular pressing surface that cooperates with the support plate. The annular pressing surface has a positioning hole that matches the positioning pin.

[0016] As one embodiment, in step three, the hot stretching die includes a lower template, a second concave die, a second convex die, and a backing plate. The second convex die is mounted on the lower template and its surface includes an inner forming surface. The backing plate is an annular piece placed on the lower template. The second convex die is placed in the inner annular hole of the backing plate. The lower template also has a push rod hole that penetrates the lower template and points to the backing plate. The surface of the second concave die includes an outer forming surface.

[0017] As one approach, in step three, all the ribs on the spherical section surface are formed by hot stretching in one go.

[0018] Furthermore, step three is followed by step four, which involves cutting off the flange edge of the open end of the cylindrical section in step two.

[0019] This invention provides a processing method for high aspect ratio titanium alloy cap parts. The method utilizes a material storage scheme to avoid the risks of tearing and thinning during processing. Furthermore, this invention involves two forming stages. The first stage forms the cylindrical and spherical sections, while the second stage forms multiple ribs with inconsistent long sides on the spherical section. The first forming stage employs a method of first bending and storing the material without blank holder force, followed by stretching with blank holder force, while retaining a flange edge with a rounded transition corner. This ensures the surface processing accuracy of complex-shaped parts like high aspect ratio titanium alloy caps, solves the problem of excessive wall thickness reduction, and results in a relatively uniform wall thickness distribution for the formed cap part, with the minimum wall thickness at the thinned area being approximately 0.8 tons. Attached Figure Description

[0020] Figure 1 A 3D model of a titanium alloy cap part;

[0021] Figure 2 This is the drawing of the first molding die;

[0022] Figure 3 This is a drawing of the second molding die;

[0023] Figure 4 This is a rough drawing of the material used in the molding of the hat cover parts.

[0024] Figure 5 This is a schematic diagram of the first stage of material storage during the first hot stretching process;

[0025] Figure 6 This is a schematic diagram of the part after the first hot stretching.

[0026] In the figure, 1-lower template, 2-first punch, 3-material support plate, 4-first die, 5-second die, 6-second punch, 7-backing plate. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0028] like Figure 1 As shown, since the cap-type parts are made of titanium alloy and have complex shapes, their forming performance at room temperature is extremely poor. The parts also have a large depth-to-diameter ratio. When using traditional hot stretching processing, these parts are prone to thinning and tearing, resulting in an extremely low pass rate.

[0029] The present invention is implemented using the following technical solution:

[0030] (1) Mold: Based on the structural characteristics of the titanium alloy cap parts, a mold was designed and manufactured. Figure 2 and Figure 3 The two sets of hot stretch forming molds shown are used to process the cylindrical and spherical sections of the cap part, and the other set is used to process the ribs on the spherical section of the cap part.

[0031] (2) Preparation of the molding blank: Calculate the required size of the blank according to the final size required for the cap part using the equal volume method. Cut the sheet metal to obtain a disc-shaped blank with a central hole. The central hole in the disc prevents tearing during the hot stretching molding process. The blank drawing is shown below. Figure 4 ;

[0032] (3) First forming: Obtaining the cylindrical segment ( Figure 6 The cylindrical surface on the right side of SR and the spherical segment ( Figure 6 (SR). During the forming process, the part is thermoformed and stretched by pressing down a certain distance without blank holder force and then pressing down another distance with blank holder force. By not applying blank holder force, the material is ensured to bend and deform during the actual processing. The subsequent application of blank holder force is used to repair the wrinkles on the surface. That is, without blank holder force, a material storage bag is formed, and the subsequent application of blank holder force restores the surface of the part. This method can ensure a thickness reduction of about 0.8t in the first forming.

[0033] Specifically, in Figure 4 The raw material surface is sprayed with graphite lubricant and TI-05 thermoforming protective coating (a protective coating for the hot stretching of titanium alloys). During the forming process, thermoforming stretching is performed using a processing mode of first pressing down 3mm without blank holder force, then pressing down 6mm with blank holder force. When the hot stretching process with and without blank holder force is halfway completed, the part is rotated relative to the first and second sets of molds to avoid jamming during stretching. The absence of blank holder force ensures that the material does not undergo tensile deformation during actual processing, and the raw material is folded in... Figure 2 The first set of molds, the raw material storage state is as follows Figure 5 Subsequently, a blank holder force is applied to repair wrinkles on the part's surface. This involves creating a material reservoir without blank holder force, followed by applying blank holder force to restore the part's shape. The part's shape after hot stretching is as follows... Figure 6 As shown, the open end of the cylindrical section has a flange edge with a rounded transition fillet, which provides machining allowance for subsequent machining of the cylindrical section (mainly outer diameter and wall thickness) to meet the requirements, while ensuring that the open end of the cylindrical section will not crack or have excessive thinning.

[0034] like Figure 2As shown, the first set of hot stretch forming molds includes a lower template 1, a first die 4, a first punch 2, and a support plate 3. The first punch 2 is mounted on the lower template 1, and its surface includes an inner forming surface of a cylindrical section and an inner forming surface of a spherical section. The support plate 3 is an annular component placed on the lower template 1, and a locating pin is provided on the support plate 3. The first punch 2 is placed in the inner annular hole of the support plate 3. The lower template 1 also has a push rod hole that penetrates the lower template 1 and points towards the support plate 3. The surface of the first die 4 includes an outer forming surface of a cylindrical section, an outer forming surface of a spherical section, and an annular pressing surface that mates with the support plate 3. A locating hole matching the locating pin is provided on the annular pressing surface. A push rod passes through the push rod hole of the lower template 1 to support the lower end face of the support plate 3. As one embodiment, the blank holder force is adjusted by the push rod inside the push rod hole of the lower template 1; that is, the push rod pushes the support plate 3 closer to the first die 4, thereby generating a blank holder force between the support plate 3 and the first die 4. The combination of positioning holes and positioning pins prevents the material support plate 3 and the first die 4 from rotating relative to each other during hot stretching.

[0035] (4) Second forming: After the cylindrical section of the main body of the cap part is machined into a spherical section, a second set of hot stretch forming molds is used to press all the ribs on the spherical section, and finally the titanium alloy cap part that meets the design requirements is produced. The spherical section after the first forming is used as the positioning reference surface during the second forming.

[0036] like Figure 3 As shown, the second set of hot stretching dies includes a lower template 1, a second concave die 5, a second convex die 6, and a backing plate 7. The second convex die 6 is mounted on the lower template 1, and its surface includes an inner forming surface for the ribs. The backing plate 7 is an annular piece placed on the lower template 1, with the second convex die 6 positioned within the inner annular hole of the backing plate 7. The lower template 1 also has a push rod hole that penetrates the lower template 1 and points towards the backing plate 7. The surface of the second concave die 5 includes an outer forming surface for the ribs. After the ribs are pressed, the backing plate 7 is pushed upwards by the push rod, causing the formed cap part to move away from the second convex die 6. The downward displacement of the second concave die 5 is controlled by selecting an appropriate thickness for the backing plate 7.

[0037] (5) Trimming, such as Figure 6 After the second molding is completed, there is still a flange edge at the right end of the cylindrical section with a corresponding transition fillet R5. This flange edge is removed by cutting.

[0038] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A method for thermoforming a titanium alloy cap, wherein the titanium alloy cap is mainly composed of a cylindrical section and a spherical section, one axial end face of the cylindrical section is open, and the other axial end face is closed through the spherical section, and the surface of the spherical section is evenly distributed with multiple ribs of varying lengths, characterized in that... The material storage thermoforming method includes the following steps: Step 1: Prepare raw materials by processing a disc-shaped plate with a central hole as the raw material. Step 2, the first forming: the raw material from Step 1 is hot-stretched to obtain cylindrical and spherical segments. The hot-stretching process is divided into two sequential stages. In the first stage, no blank holder force is applied during hot stretching. The raw material enters the hot stretching mold for storage without stretching deformation, and a spherical storage bag is formed in the center area of ​​the raw material. In the second stage, blank holder force is applied during hot stretching, and the cylindrical and spherical segments are stretched and formed in the hot stretching mold. Step 3, second forming: using a hot stretching forming method, all the ribs are machined on the surface of the spherical segment obtained in step 2; In step two, there is at least one part rotation operation in both the first and second stage hot stretching processes, causing the stretching part in the hot stretching die to rotate relative to the hot stretching die. In step two, the hot stretching die used includes a lower template, a first concave die, a first convex die, and a support plate. The first convex die is mounted on the lower template and its surface includes an inner forming surface of a cylindrical section and an inner forming surface of a spherical section. The support plate is an annular piece placed on the lower template and is provided with a positioning pin. The first convex die is placed in the inner annular hole of the support plate. The lower template also has a push rod hole that penetrates the lower template and points to the support plate. The surface of the first concave die includes an outer forming surface of a cylindrical section, an outer forming surface of a spherical section, and an annular pressing surface that cooperates with the support plate. The annular pressing surface has a positioning hole that matches the positioning pin. In step three, the hot stretching die used includes a lower template, a second concave die, a second convex die, and a backing plate. The second convex die is mounted on the lower template and its surface includes an inner forming surface. The backing plate is an annular piece placed on the lower template. The second convex die is placed in the inner annular hole of the backing plate. The lower template also has a push rod hole that penetrates the lower template and points to the backing plate. The surface of the second concave die includes an outer forming surface.

2. The material storage thermoforming method for titanium alloy cap covers according to claim 1, characterized in that: In step one, the size of the disc-shaped material with the central opening is calculated by converting the volume of the titanium alloy cap part into the volume of the material using the equal volume method.

3. The material storage thermoforming method for titanium alloy cap covers according to claim 1, characterized in that: In step two, the amount of pressure applied during the first stage of hot stretching is less than the amount of pressure applied during the second stage of hot stretching.

4. The material storage thermoforming method for titanium alloy cap covers according to claim 1, characterized in that: In step two, before the first stage of hot stretching, a lubricant and a thermoforming protective coating are sprayed onto the surface of the raw material.

5. The material storage thermoforming method for a titanium alloy cap cover according to claim 1, characterized in that: In step two, after the second stage of hot stretching, a flange edge with a transition fillet is formed at the open end of the cylindrical section.

6. The material storage thermoforming method for a titanium alloy cap cover according to claim 1, characterized in that: In step three, all the ribs on the spherical section are formed by hot stretching in one go.

7. The material storage thermoforming method for titanium alloy cap covers according to claim 1, characterized in that: It also includes step four, cutting off the flange edge at the open end of the cylindrical section in step two.

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