Forging method for a titanium alloy forging with a rectangular cross-section

Abstract

The present invention relates to a forging method for a titanium alloy forging with a rectangular cross-section, comprising the following steps: S1. Blooming forging: performing blooming forging on the titanium alloy, and upsetting and drawing the billet multiple times to a set size; S2. Intermediate forging: performing multi-heat forging on the billet after blooming to obtain an intermediate forging billet; S3. Finished product forging: performing multi-heat forming on the intermediate forging billet at a temperature below the phase transformation point, and finally obtaining a titanium alloy forging with a rectangular cross-section that meets the specifications. This method ensures consistent deformation of the billet at each angle, reduces the difference in microstructure between the corners and the middle part when finally formed into a square billet, and maximally ensures the uniformity of the microstructure of the forging.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium alloy forging, and relates to a forging method for a titanium alloy forging with a rectangular cross-section. Background Art

[0002] Titanium alloys have the advantages of high specific strength, strong corrosion resistance, good biocompatibility, and can work at high temperatures for a long time. They are widely used in national defense, aerospace, shipbuilding, chemical industry, medical, biological and other fields, and are known as future metals. The weight ratio of titanium alloys used in some advanced aircraft has exceeded 30%, and with the progress of processing and manufacturing technology, this ratio is increasing year by year. Titanium alloys also have some disadvantages: such as large deformation resistance, high notch sensitivity, poor thermal conductivity, and large influence of tissue changes on mechanical properties. As a result, there are many uncertain factors in the hot working process.

[0003] Rectangular cross-section forgings are a special form of forgings, and their forging process is very different from that of circular cross-section forgings. During the forming process, the corner parts are easier to cool than other parts. After cooling, the fluidity of the metal becomes poor, and the grains are not easy to break, resulting in poor microstructure in the corner edge parts and uneven overall microstructure of the forging, posing a threat to the harsh working conditions. In addition to the mechanical properties of titanium alloy forgings, non-destructive testing methods such as ultrasonic testing are also an important evaluation method for titanium alloy forgings. Especially in evaluating the uniformity of forgings, ultrasonic testing has irreplaceable convenience and operability. In GJB2744A, it is stipulated that the bottom wave loss does not exceed 50% is the requirement for the microstructure uniformity of forgings.

[0004] When forming rectangular cross-section forgings, for the convenience of the production process, many forming methods can be designed for different blank specifications. However, from the past data, not all forming methods can produce forgings that meet the standards, especially forgings with special requirements for uniformity. Therefore, for such forgings, a special forming method is needed to achieve this. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art, and propose a forging method for a titanium alloy forging with a rectangular cross-section, which ensures that the deformation of the blank is consistent at each angle, and when finally formed into a square blank, reduces the difference in microstructure between the corners and the middle part, and maximally ensures the uniformity of the microstructure of the forging.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A forging method for a titanium alloy forging with a rectangular cross-section, characterized by comprising the following steps:

[0008] S1. Blooming Forging: Subject the titanium alloy to blooming forging, and upset and draw out the billet multiple times to the set size.

[0009] S2. Intermediate Forging: Forge the billet after blooming in multiple heats to obtain an intermediate forged billet.

[0010] S3. Finish Forging: Form the intermediate forged billet in multiple heats at a temperature below the phase transformation point to finally obtain a titanium alloy forging with a rectangular cross-section meeting the specifications.

[0011] Furthermore, the blooming forging in S1 is carried out in 1 to 3 heats. The heating temperature for blooming forging is 1000 - 1200 °C, the heat preservation coefficient is 0.5 - 1.2, the forging ratio is 1.5 - 2.5, and an anvil with a width of 400 - 1000 mm is used when upsetting the billet.

[0012] Furthermore, the blooming forging is divided into two upsetting and drawing operations, and chamfering is performed on the billet after each drawing.

[0013] Furthermore, S2 specifically includes:

[0014] S21. Forge the billet after blooming forging in step S1 above the phase transformation point in 2 to 4 heats. The heating temperature is 10 - 20 °C above the phase transformation point, and the forging method is upsetting and drawing. Each heat consists of 2 upsetting and 2 drawing operations. Chamfering is performed on the billet after each drawing. The upsetting and drawing ratio for each heat is 1.5 - 2.0. After forging, water cooling is used for cooling to obtain a primary intermediate forged billet.

[0015] S22. Forge the primary intermediate forged billet below the phase transformation point in 2 to 4 heats. The heating temperature is carried out at 30 - 60 °C below the phase transformation point. The forging method is also upsetting and drawing. Each heat consists of 2 upsetting and 2 drawing operations. Chamfering is performed on the billet after each drawing. After 1 upsetting and drawing operation, the billet is reversed axially and radially. The upsetting and drawing ratio for each heat is 1.7 - 2.2. After forging, water cooling is used for cooling, and air cooling is used for the cooling method in the last heat to obtain a secondary intermediate forged billet.

[0016] S23. Divide the secondary intermediate forged billet. The weight after division is 200 - 400 Kg. The divided billet is forged below the phase transformation point in 2 to 4 heats. The heating temperature for each heat is carried out at 40 - 70 °C below the phase transformation point. The forging method is upsetting and drawing. Each heat consists of 2 upsetting and 2 drawing operations. Chamfering is performed on the billet after each drawing, and reversing is also carried out simultaneously. The upsetting and drawing ratio for each heat is 1.7 - 2.5. After cooling, a tertiary intermediate forged billet is obtained, and the cooling method is water cooling.

[0017] Further, S3 specifically includes: subjecting the three intermediate forging blanks obtained in S2 to 2 to 4 heat treatments for forming and forging below the phase transformation point, with the heating temperature being 50 to 70°C below the phase transformation point. The forging method is drawing, with a drawing ratio of 2 to 5. After the end of drawing the square bar in each heat treatment, the blank is rolled into a round shape, and drawing continues in the next heat treatment until a titanium alloy forging with a rectangular cross-section meeting the specifications is obtained.

[0018] Further, the square billet is single-sized in both the height and width directions and multi-sized in the length direction.

[0019] Further, in the multi-heat treatment forming stage in S3, the cooling method is air cooling.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] In this forging method, the ingot is subjected to multiple heat treatments for forging. After dividing the secondary intermediate forging blank, forging of the small-sized blank continues, and a reverse forging treatment is added. After a series of forging processes, the structure of each part of the blank becomes uniform. In the forming stage, after drawing is completed, the blank is rolled into a round shape to ensure uniform deformation at each angle of the blank. When finally forming into a square billet, the difference in structure between the corners and the middle part is reduced, ensuring the uniformity of the forging structure to the greatest extent.

[0022] In the present invention, through the following detailed description of the exemplary embodiments of the present invention with reference to the accompanying drawings, other features and advantages of the present invention will become clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings herein are incorporated into the specification and form a part of the specification, and are used together with the specification to explain the principles of the present invention.

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a microstructural diagram of the forging in Embodiment 1 of the present invention;

[0026] Figure 2 It is a microstructural diagram of the forging in Embodiment 2 of the present invention;

[0027] Figure 3 It is a schematic diagram of the ingot forging process in one heat treatment of the present invention;

[0028] Figure 4 It is a schematic diagram of the intermediate forging process in one heat treatment of the present invention;

[0029] Figure 5 This is a schematic diagram of the forging process of the finished product of the present invention. Detailed implementation manners

[0030] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present invention. On the contrary, they are merely examples of devices consistent with some aspects of the present invention detailed in the appended claims.

[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0032] A forging method for a titanium alloy forging with a rectangular cross-section includes the following steps:

[0033] S1. Blooming forging: Perform blooming forging on the titanium alloy, and upset and draw the billet multiple times to the set size; The blooming forging is carried out for 1 to 3 heats, the heating temperature for blooming forging is 1000 - 1200 °C, the soaking coefficient is 0.5 - 1.2, the forging ratio is 1.5 - 2.5, an anvil with a width of 400 - 1000 mm is used when upsetting the billet, the blooming forging is divided into two upsetting and drawing operations, and chamfering is performed on the billet after each drawing.

[0034] S2. Intermediate forging:

[0035] S21. Redraw the billet after blooming forging in step S1 above the phase transformation point for 2 to 4 heats, the heating temperature is 10 - 20 °C above the phase transformation point, the redrawing method is upsetting and drawing, each heat is 2 upsetting and 2 drawing operations, chamfering is performed on the billet after each drawing, the upsetting and drawing ratio for each heat is 1.5 - 2.0, and water cooling is used for cooling after forging to obtain a first intermediate forging billet; <(

[0036] S22. Redraw the first intermediate forging billet below the phase transformation point for 2 to 4 heats, the heating temperature is carried out at 30 - 60 °C below the phase transformation point, the redrawing method is also upsetting and drawing, each heat is 2 upsetting and 2 drawing operations, chamfering is performed on the billet after each drawing, the axial and radial directions of the billet are reversed after 1 upsetting and drawing operation, the upsetting and drawing ratio for each heat is 1.7 - 2.2, water cooling is used for cooling after forging, and air cooling is used for cooling in the last heat to obtain a second intermediate forging billet;

[0037] S23. Divide the secondary intermediate forging blank. After division, the weight is 200 - 400 Kg. The divided blank is forged in 2 - 4 heating cycles below the phase transformation point. Each heating cycle is carried out at a temperature 40 - 70 °C below the phase transformation point. The forging method is upsetting and drawing. Each heating cycle includes 2 upsetting operations and 2 drawing operations. Chamfer the blank after each drawing operation and reverse the direction at the same time. The upsetting-drawing ratio for each heating cycle is 1.7 - 2.5. After cooling, a tertiary intermediate forging blank is obtained. The cooling method is water cooling.

[0038] S3. Finish forging: The intermediate forging blank is formed in multiple heating cycles at a temperature below the phase transformation point to finally obtain a titanium alloy forging with a rectangular cross-section that meets the specifications. The tertiary intermediate forging blank obtained in S2 is formed and forged in 2 - 4 heating cycles below the phase transformation point. The heating temperature is 50 - 70 °C below the phase transformation point. The forging method is drawing, and the drawing ratio is 2 - 5. After each square bar drawing in each heating cycle, roll the blank to a round shape and continue drawing in the next heating cycle until a titanium alloy forging with a rectangular cross-section that meets the specifications is obtained. The square blank is single-sized in both height and width directions and multi-sized in the length direction. The cooling method during the multiple heating cycle forming stage is air cooling.

[0039] The following is an illustration in combination with a specific process treatment:

[0040] Example 1

[0041] Standard: GJB2744A - 2019, flaw detection level: A. Preparation method for a TC4 forging with specifications of 60×80×190:

[0042] S1. Ingot forging:

[0043] Blank size: φ600×850 mm. The ingot forging heating temperature is 1000 - 1200 °C, the heat preservation coefficient is 0.5 - 1.2, the forging ratio is 1.5 - 2.5. When upsetting the blank, an anvil with a width of 400 - 1000 mm is used. The blank is upset twice and drawn twice to obtain an octagonal shape of 495×990 mm. The cooling method is water cooling.

[0044] S2. Intermediate forging:

[0045] Blank size: The heating temperature is 10 - 20 °C above the phase transformation point. The forging heating cycle is 2 - 4 times. The forging method is upsetting twice and drawing twice. Similarly, chamfer the blank after each drawing operation to ensure that the blank maintains a uniform overall color during forging. The upsetting-drawing ratio for each heating cycle is 1.5 - 2.0. After forging, cool the blank. The cooling method is water cooling to obtain a primary intermediate forging blank with specifications of octagonal 495×990 mm;

[0046] The primary intermediate forging blank is forged and modified in 2 to 4 heats below the phase transformation point, with the heating temperature carried out at 30 to 60 °C below the phase transformation point. The forging and modification method is also two-upsetting and two-drawing. Chamfering is also carried out on the blank after each drawing to ensure that the blank maintains a uniform overall color state during the forging process. And after 1 upsetting and drawing, axial and radial reorientation of the blank is required. The upsetting and drawing ratio for each heat is 1.7 to 2.2. After forging, it is cooled, and the cooling method is water cooling. The cooling method for the last heat is air cooling to obtain a secondary intermediate forging blank with a specification of octagonal 495×990 mm;

[0047] The secondary intermediate forging blank is divided in half, and the specification after dividing is octagonal 495×440 mm. The blank is forged and modified in 2 to 4 heats below the phase transformation point, with the heating temperature carried out at 30 to 60 °C below the phase transformation point. The forging and modification method is also two-upsetting and two-drawing. Chamfering is also carried out on the blank after each drawing to ensure that the blank maintains a uniform overall color state during the forging process. And after 1 upsetting and drawing, axial and radial reorientation of the blank is required. The upsetting and drawing ratio for each heat is 1.7 to 2.2. After forging, it is cooled, and the cooling method is water cooling to obtain a tertiary intermediate forging blank with a specification of octagonal 495×990;

[0048] S3. Finish forging:

[0049] The tertiary intermediate forging blank obtained in S2 is subjected to 2 to 4 heats of forming forging below the phase transformation point, with the heating temperature carried out at 50 to 70 °C below the phase transformation point. The forging and modification method is drawing forging, and the drawing ratio is 2 to 5. After each square bar drawing in each heat, the blank needs to be rolled to a round shape and continue drawing in the next heat until a square blank that meets the requirements is obtained. The blank is single-sized in the height and width directions and multi-sized in the length direction. In the S3 forming stage, the cooling method is air cooling. After the finish forging of the blank, machining is carried out to complete the preparation of the forging.

[0050] Physical and chemical test results of the forging:

[0051] (1) Room temperature mechanical properties of the forging:

[0052] The mechanical properties of the forging after heat treatment are shown in the following table. The room temperature mechanical properties of the forging in the L / LT / ST directions all meet and are higher than the requirements in GB / T2744A-2019, and the differences in the three directions are small. It can be seen from the mechanical properties that the organization of the forging is uniform in all directions. The impact in the L direction and KIC in the T-L direction also meet the standard requirements, and the hardness in all directions meets the standard.

[0053]

[0054] (2) Macrostructure of the forging:

[0055] There are no cracks, folds, pores, segregation, metallic or non-metallic inclusions, and other metallurgical defects visible to the naked eye at low magnification.

[0056] (3) Microstructure of the forging:

[0057] Such as Figure 1 As shown, the uniform microstructure processed in the two-phase region, with the β grain boundary α being fully broken and no continuous straight α-phase grain boundary being seen.

[0058] (4) Ultrasonic flaw detection of the forging:

[0059]

[0060] Example 2

[0061] The standard is GJB2744A-2019, the flaw detection level is Class A, and the preparation method of the TB6 forging with the specification of 200×100×100:

[0062] S1. Blooming forging:

[0063] Blank size: φ500×750mm, the heating temperature for blooming forging is 1000 - 1200°C, the heat preservation coefficient is 0.5 - 1.2, the forging ratio is 1.5 - 2.5, and an anvil with a width of 400 - 1000mm is used when upsetting the blank. The blank is upset and drawn twice to obtain an octagonal shape of 420×835mm. The cooling method is water cooling.

[0064] S2. Intermediate forging:

[0065] Blank size: octagonal 420×835mm, the heating is carried out at 10 - 20°C above the phase transformation point, the number of forging passes for re-forging is 2 - 4 passes, the re-forging method is upset and draw twice, and the blank is chamfered after each drawing to ensure that the blank maintains a uniform overall color during the forging process. The upsetting and drawing ratio for each pass is 1.5 - 2.0. After forging, it is cooled, and the cooling method is water cooling to obtain a first intermediate forging blank with the specification of octagonal 420×835mm;

[0066] The first intermediate forging blank is re-forged 2 - 4 times below the phase transformation point, the heating temperature is carried out at 30 - 60°C below the phase transformation point, the re-forging method is also upset and draw twice, and the blank is chamfered after each drawing to ensure that the blank maintains a uniform overall color during the forging process; and after 1 upsetting and drawing, the blank needs to be reversed axially and radially. The upsetting and drawing ratio for each pass is 1.7 - 2.2. After forging, it is cooled, the cooling method is water cooling, and the cooling method for the last pass is air cooling to obtain a second intermediate forging blank with the specification of octagonal 420×835mm;

[0067] Divide the secondary intermediate forging blank in half. After dividing, the specifications are octagonal, 420×415 mm. Forge the blank 2 to 4 times below the phase transformation point. The heating temperature is carried out 30 to 60 °C below the phase transformation point. The forging method is also two upsetting and two drawing operations. After each drawing operation, chamfer the blank to ensure that the blank maintains a uniform color state during the forging process. And after 1 upsetting and drawing operation, the axial and radial directions of the blank need to be reversed. The upsetting and drawing ratio for each heat treatment is 1.7 to 2.2. After forging, cool it. The cooling method is water cooling to obtain a tertiary intermediate forging blank with specifications of octagonal, 420×415 mm.

[0068] S3. Finish forging:

[0069] Carry out 2 to 4 times of forming forging on the tertiary intermediate forging blank obtained in S2 below the phase transformation point. The heating temperature is carried out 50 to 70 °C below the phase transformation point. The forging method is drawing forging, and the drawing ratio is 2 to 5. After each square bar drawing operation, the blank needs to be rolled into a round shape and continue drawing in the next heat treatment until a square blank that meets the requirements is obtained. The blank is single-sized in the height and width directions and multi-sized in the length direction. In the S3 forming stage, the cooling method is air cooling. After the finish forging of the blank, machining is carried out to complete the preparation of the forging.

[0070] Physical and chemical test results of the forging:

[0071] (1) Room temperature mechanical properties of the forging:

[0072] The mechanical properties of the forging after heat treatment are shown in the following table. The room temperature mechanical properties of the forging in the L / LT / ST directions all meet and are higher than the requirements in GB / T2744A-2019, and the differences in the three directions are small. It can be seen from the mechanical properties that the microstructure of the forging is uniform in all directions. The KIC in the T-L direction also meets the standard requirements.

[0073]

[0074] (2) Macrostructure of the forging:

[0075] There are no cracks, inclusions, segregation, shrinkage cavities, pores, delamination, and other metallurgical defects in the macrostructure. There are no clearly visible grains to the naked eye in the macrostructure.

[0076] (3) Microstructure of the forging:

[0077] As Figure 2 shown, it is composed of aged β matrix, spherical and strip-shaped α phases. The content of primary α phase is greater than 10%. There is no continuous and straight α phase network at the boundary of the original β grains, no coarse grain boundary α phase structure, and no β patches.

[0078] (4) Ultrasonic flaw detection of the forging:

[0079]

[0080] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0081] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A forging method for a titanium alloy forging with a rectangular cross-section, characterized in that, It includes the following steps: S1. Blooming forging: Forging the titanium alloy by blooming, upsetting and drawing out the billet multiple times to the set size; S2. Intermediate forging: Forging the billet after blooming in multiple heats to obtain an intermediate forged billet; S3. Finished forging: Forming the intermediate forged billet in multiple heats at a temperature below the phase transformation point to finally obtain a titanium alloy forging with a rectangular cross-section that meets the specifications; The blooming forging in S1 is carried out in 1 to 3 heats, the heating temperature for blooming forging is 1000 to 1200 °C, the heat preservation coefficient is 0.5 to 1.2, the forging ratio is 1.5 to 2.5, and an anvil with a width of 400 to 1000 mm is used when upsetting the billet; The blooming forging is divided into two upsetting and drawing operations, and chamfering is carried out on the billet after each drawing; S2 specifically includes: S21. Forging the billet after blooming forging in step S1 in 2 to 4 heats above the phase transformation point, the heating temperature is 10 to 20 °C above the phase transformation point, the forging method is upsetting and drawing, each heat is 2 times of upsetting and 2 times of drawing, chamfering is carried out on the billet after each drawing, the upsetting and drawing ratio for each heat is 1.5 to 2.0, and water cooling is used for cooling after forging to obtain a primary intermediate forged billet; S22. Forging the primary intermediate forged billet in 2 to 4 heats below the phase transformation point, the heating temperature is carried out at 30 to 60 °C below the phase transformation point, the forging method is also upsetting and drawing, each heat is 2 times of upsetting and 2 times of drawing, chamfering is carried out on the billet after each drawing, the axial and radial directions of the billet are reversed after 1 upsetting and drawing operation, the upsetting and drawing ratio for each heat is 1.7 to 2.2, water cooling is used for cooling after forging, and air cooling is used for cooling in the last heat to obtain a secondary intermediate forged billet; S23. Dividing the secondary intermediate forged billet, the weight after dividing is 200 to 400 Kg, the billet after dividing is forged in 2 to 4 heats below the phase transformation point, the heating temperature for each heat is carried out at 40 to 70 °C below the phase transformation point, the forging method is upsetting and drawing, each heat is 2 times of upsetting and 2 times of drawing, chamfering is carried out on the billet after each drawing, and reversing is carried out at the same time, the upsetting and drawing ratio for each heat is 1.7 to 2.5, and a tertiary intermediate forged billet is obtained after cooling, and the cooling method is water cooling.

2. The forging method of a titanium alloy forging with a rectangular cross-section according to claim 1, characterized in that, S3 specifically is: Forming and forging the tertiary intermediate forged billet obtained in S2 in 2 to 4 heats below the phase transformation point, the heating temperature is carried out at 50 to 70 °C below the phase transformation point, the forging method is drawing, the drawing ratio is 2 to 5, rolling the billet into a round shape is carried out after the end of drawing the square bar in each heat, and drawing continues in the next heat until a titanium alloy forging with a rectangular cross-section that meets the specifications is obtained.

3. The forging method of a titanium alloy forging with a rectangular cross-section according to claim 2, characterized in that, The square billet is single-sized in both the height and width directions and multi-sized in the length direction.

4. The forging method of a titanium alloy forging with a rectangular cross-section according to claim 2, characterized in that, In the multi-heat forming stage in S3, the cooling method is air cooling.

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