A forging method for a cross-shaped TC32 titanium alloy die forging.

Abstract

This invention belongs to the field of forging hot working and relates to a forging method for a cross-shaped TC32 titanium alloy die forging. The method includes: selecting a bar stock as a billet; upsetting the bar stock and shaping it into a cuboid; reversing the direction of the billet and elongating it along its short side, shaping it into an irregular octagonal cross-section cube as the billet; on the cube, the surface corresponding to the web of the cross-shaped TC32 titanium alloy die forging is larger than the surface corresponding to the high ribs of the cross-shaped TC32 titanium alloy die forging, and the web material is also more than the high rib material; vertically placing the billet into a pre-forging die along its height direction for upsetting to obtain a cross-shaped pre-forging; the cross-shaped pre-forging has lugs at both ends; the larger lug is used to form the high ribs with bosses, the smaller lug is used to form the high ribs, and the middle of the pre-forging is used to form the web; rotating the pre-forging 90° and placing it with the larger lug facing upwards into the final forging die for cross-shaped reversing forging.

Description

Technical Field

[0001] This invention belongs to the field of forging and hot working, and relates to a forging method for a cross-shaped TC32 titanium alloy die forging. Background Technology

[0002] To meet the demands of a certain Chinese aircraft for significant weight reduction, long service life, and cost control, the development of a new generation of high-performance and low-cost titanium alloys for the main structural components has become an important development direction for aerospace materials. TC32 titanium alloy is a low-cost, high-performance titanium alloy with a main chemical composition of Ti-5Al-3Mo-3Cr-1Zr. This alloy possesses advantages such as ultra-high toughness, medium strength, and high plasticity. Furthermore, it has a wide hot working window and excellent strength-toughness matching, making it suitable for use in forgings of key load-bearing structures for next-generation aircraft.

[0003] Forgings for aircraft joint structures are critical components for connection and load-bearing. Because they must withstand forces in multiple directions, they are typically cross-shaped. This shape presents significant challenges in blank preparation and die forging, primarily due to the following problems: 1. Complex blank structure, making free forging difficult; difficult die forging, requiring large tonnage equipment, multiple forging passes, and a long production cycle; 2. Complex forging structure, significant deformation differences in different parts, and poor microstructure uniformity; 3. Large blank weight, reduced material utilization, and increased forging costs; 4. Difficulty in aligning the original flow lines of the bar stock with the final forging, significantly impacting the forging's microstructure and properties. Summary of the Invention

[0004] Objective of the Invention: This invention provides a forging method for cross-shaped TC32 titanium alloy forgings to meet the requirements of key load-bearing joint components in my country's new generation of aircraft. It also provides a method for billet preparation and die forging of cross-shaped forgings. By combining two different types of forging equipment—hydraulic press pre-forging and spiral hammer reversing cross-shaped final forging—the die forging process ensures that the fiber flow lines of the billet are consistent with the flow lines of the forging, reducing the tonnage required for die forging equipment, decreasing the number of forging passes, improving production efficiency, increasing material utilization, reducing production costs, and ensuring a reasonable match between the final shape, microstructure, and properties of the forging, ultimately improving the product qualification rate.

[0005] Technical solution:

[0006] A forging method for a cross-shaped TC32 titanium alloy forging is provided, comprising:

[0007] Bar stock was selected as the billet.

[0008] Upsetting and shaping of bar stock into cuboids;

[0009] The billet is reversing and elongated along the short side, and shaped into an irregular octagonal cross-section cube as the billet, ensuring that the flow line direction of the billet is parallel to the cross-section and consistent with the original flow line direction of the bar stock; the web corresponding to the cross-shaped TC32 titanium alloy die forging is larger than the high rib corresponding to the cross-shaped TC32 titanium alloy die forging, and the web material is also more than the high rib material.

[0010] The billet is placed vertically into the pre-forging mold along its own height direction for upsetting to obtain a cross-shaped pre-forging part; the cross-shaped pre-forging part has ear pieces at both ends; the large ear piece is used to form the high rib with the boss, the small ear piece is used to form the high rib, and the middle part of the pre-forging part is used to form the web.

[0011] Rotate the pre-forged part 90° and place it into the final forging die with the large lugs facing upwards for cross-shaped forging.

[0012] Furthermore, the method also includes:

[0013] If the maximum equivalent cross section thickness of a certain part of a cross-shaped forging is greater than 120mm, the thickness of that part should be reduced by machining beforehand.

[0014] Heat treatment is performed on forgings that have been machined to reduce thickness.

[0015] Furthermore, the preheating temperature range for the forging hammer anvil and other auxiliary tooling is 200℃~300℃.

[0016] Furthermore, the billet pre-forging process is carried out on a hydraulic press, with the pressing speed controlled at 2-5 mm / s;

[0017] The final forging process of the billet is carried out on a spiral hammer, with the pressing rate controlled at 0.3 to 0.5 m / s, and the energy increment is set for each hammer.

[0018] Furthermore, the preheating temperature of the die forging mold is 250℃~350℃.

[0019] Furthermore, pre-forging is carried out on a hydraulic press.

[0020] Furthermore, the pre-forged part is rotated 90° and placed into the final forging die for cross-shaped forging on a spiral hammer.

[0021] Furthermore, the machined forgings with reduced thickness undergo heat treatment, including:

[0022] The forgings with reduced thickness by machining are subjected to the first annealing, wherein the temperature is heated to 850℃~900℃, the holding time is 3h, and the cooling method is air cooling; the uniformity of the electric furnace is ±10℃, and the transfer time of the forgings from the furnace to air cooling is less than or equal to 90s;

[0023] The forgings with reduced thickness by machining are subjected to a second annealing process, in which the temperature is heated to 500℃~580℃ and held for 6 hours, and the cooling method is air cooling; the uniformity of the electric furnace is ±5℃.

[0024] Furthermore, a gap of 100 μm or more is left between the forgings in the electric furnace; the forgings are placed on the charging plate, which has ventilation holes or the forgings are supported and placed stably to prevent deformation of the forgings during heating, which would result in uneven machining allowance of the forgings.

[0025] Furthermore, the forging parameters during free forging and die forging include:

[0026] The billet is heated to 30℃~40℃ below the phase transformation point; the heating coefficient for cold material is 0.6~0.8min / mm, and the heating coefficient for hot material returning to the furnace is 0.4~0.6min / mm.

[0027] During forging, the deformation per forging pass is 25% to 30%; the final forging temperature is greater than or equal to 750℃.

[0028] Beneficial effects

[0029] This paper presents a forging method for cross-shaped TC32 titanium alloy forgings to meet the requirements of key load-bearing joint components in my country's new generation of aircraft. It also provides a method for billet preparation and die forging of cross-shaped forgings. By combining two different types of forging equipment—hydraulic press pre-forging and spiral hammer reversing cross-shaped final forging—the die forging process ensures that the fiber flow lines of the billet are consistent with the flow lines of the forging, reducing the tonnage required for die forging equipment, decreasing the number of forging passes, improving production efficiency, increasing material utilization, reducing production costs, and ensuring a reasonable match between the final shape, microstructure, and properties of the forging, ultimately improving the product qualification rate. Attached Figure Description

[0030] Figure 1a Schematic diagram 1 of a certain type of machine joint forging.

[0031] Figure 1b Schematic diagram of the structure of a certain type of machine joint forging. Figure 2 .

[0032] Figure 2 This is a schematic diagram of a cube with an irregular octagonal cross-section.

[0033] Figure 3a This is a schematic diagram of the billet's placement position in the pre-forging cavity.

[0034] Figure 3b This is a schematic diagram of the pre-forged part.

[0035] Figure 4a Schematic diagram 1 shows the phase relationship between the pre-forging and the final forging.

[0036] Figure 4b Schematic diagram of the phase relationship between the pre-forging and the final forging Figure 2 .

[0037] Figure 5 This is a forging process diagram for a cross-shaped TC32 titanium alloy die forging. Detailed Implementation

[0038] This invention provides a forging method for a cross-shaped TC32 titanium alloy forging, comprising:

[0039] Bar stock was selected as the billet.

[0040] Upsetting and shaping of bar stock into cuboids

[0041] The billet is reversibly elongated on its short side and shaped into an irregular octagonal cube, ensuring that the billet's streamline direction is parallel to the cross-section and consistent with the original streamline direction of the bar stock.

[0042] The billet is placed vertically into the pre-forging die for upsetting to obtain a cross-shaped pre-forging part.

[0043] Rotate the pre-forged part 90° and place it into the final forging die for cross-shaped forging.

[0044] Furthermore, the method also includes:

[0045] For parts of the formed cross-shaped die forging where the maximum equivalent cross section thickness is greater than the preset thickness, machining is performed to reduce the thickness.

[0046] Heat treatment is performed on forgings that have been machined to reduce thickness.

[0047] Furthermore, the preset thickness is 120mm.

[0048] Furthermore, the preheating temperature range for the forging hammer anvil and other auxiliary tooling is 200℃~300℃.

[0049] Furthermore, the billet pre-forging is carried out on a hydraulic press with a reduction rate controlled at 2-5 mm / s; the billet final forging is carried out on a spiral hammer with a reduction rate controlled at 0.3-0.5 m / s, and energy increments are set for each hammer.

[0050] Furthermore, the preheating temperature of the die forging mold is 250℃~350℃.

[0051] Furthermore, during the billet preparation process, the bar stock is first upset and then drawn in a different direction to form an irregular octagonal cross-section cube, which matches the pre-forging cavity;

[0052] The billet is placed vertically into the pre-forging die for upsetting to obtain a cross-shaped pre-forging part.

[0053] Rotate the pre-forged part 90° and place it into the final forging die for cross-shaped forging.

[0054] Furthermore, the machined forgings with reduced thickness undergo heat treatment, including:

[0055] The forgings with reduced thickness by machining are subjected to the first annealing, wherein the temperature is heated to 850℃~900℃, the holding time is 3h, and the cooling method is air cooling; the uniformity of the electric furnace is ±10℃, and the transfer time of the forgings from the furnace to air cooling is less than or equal to 90s;

[0056] The forgings with reduced thickness by machining are subjected to a second annealing process, in which the temperature is heated to 500℃~580℃ and held for 6 hours, and the cooling method is air cooling; the uniformity of the electric furnace is ±5℃.

[0057] Furthermore, a gap of 100 mm or more is left between the internal parts of the electric furnace; the forgings are placed on the charging plate, which has ventilation holes or the forgings are supported and placed stably to prevent deformation of the forgings during heating, which would result in uneven machining allowance of the forgings.

[0058] Furthermore, the forging parameters during free forging and die forging include:

[0059] The billet is heated to 30℃~40℃ below the phase transformation point; the heating coefficient for cold material is 0.6~0.8min / mm, and the heating coefficient for hot material returning to the furnace is 0.4~0.6min / mm.

[0060] During forging, the deformation per forging pass is 25% to 30%; the final forging temperature is greater than or equal to 750℃.

[0061] This invention proposes a forging method for a cross-shaped TC32 titanium alloy die forging, such as... Figure 5 As shown, the specific steps are as follows:

[0062] Step 1: Design the forging according to the shape of the part. Usually, the parting surface is selected as the plane with the largest projection, which facilitates the forming and parting of the forging.

[0063] Preferably, based on the characteristics of the part, the forging allowance, draft angle, and fillet size are determined. For narrow, high-ribbed areas and areas difficult to fill in during die forging, a design approach of large arc transition, variable allowance, and draft angle is adopted.

[0064] Step 2: Select bar stock as billet: The length-to-diameter ratio of the billet should be controlled between 2 and 3 times to facilitate upsetting;

[0065] Step 3: First, upset the bar stock and shape it into a cuboid; then, reverse the direction of the billet to lengthen the short side and shape it into an irregular octagonal cross-section cube, ensuring that the flow lines of the billet are parallel to the cross-section and consistent with the original flow lines of the bar stock.

[0066] An octagonal cross-section cube can be placed vertically into the pre-forging cavity, with external dimensions similar to those of the pre-forging cavity (see...). Figure 2 );

[0067] During forging, hammering should be slow to prevent overheating of the core. During upsetting, each hammer blow should reduce the weight by 30-50mm, followed by a lift of the hammer before the second blow. The upsetting speed should be slow and uniform, controlled at 5-8mm / s. During drawing, each hammer blow should feed 80-100mm of the current pressing height, with a reduction of ≤35mm per hammer blow.

[0068] The angles of an octagonal cube should not be too small, generally controlled between R50 and 100.

[0069] The side length of the octagonal cube corresponding to the four intersecting directions of the pre-forging cavity should be strictly controlled to avoid damage to the mold bridge.

[0070] Re-sinking of hot materials for reshaping is permitted, and the rough shape can be checked using templates or molds.

[0071] Step 4: Vertically place the octagonal cube blank into the cavity of the pre-forging mold for upsetting to obtain a cross-shaped pre-forging part that is thick in the middle and thin on both sides.

[0072] Furthermore, pre-forging and upsetting are generally carried out using a hydraulic press. The billet is placed in an electric furnace at 100–150°C for preheating for 10–20 minutes, and a lubricant is sprayed on. The coating should be uniform and cover the entire surface of the billet.

[0073] Furthermore, the billet is heated to 30°C–40°C below the phase transformation point;

[0074] The heating coefficient for cold material is 0.6–0.8 min / mm, and the heating coefficient for hot material returning to the furnace is 0.4–0.6 min / mm; during forging, the deformation per forging pass is 25%–30%; the final forging temperature is greater than or equal to 750℃; and the cooling method is air cooling.

[0075] Furthermore: the mold preheating temperature is 250℃~350℃;

[0076] Step 5: Rotate the pre-forging part 90° and place it into the final forging die cavity for cross-shaped forging.

[0077] Furthermore, the two wings of the pre-forged part are vertically placed into the final forging cavity to form the narrow high ribs on the upper and lower sides of the final forging part, and the middle thick section position parallel to the mold cavity is used to form the large web plate part of the final forging part.

[0078] Furthermore, the final forging is carried out on a spiral hammer, with the pressing rate controlled at 0.3–0.5 m / s, and energy increments are set for each hammer strike.

[0079] Step 6: Perform localized section reduction machining on the cross-shaped forging formed in Step 5 to reduce the effective heat treatment thickness of the forging;

[0080] Preferably, in the solid part of the cross-shaped die forging head where the equivalent cross section thickness (inscribed circle diameter) is greater than 120mm, a Φ45 through hole coaxial with the part is added by machining. The purpose is to reduce the effective thickness of the forging, prepare for subsequent heat treatment annealing, and meet the requirements of forging structure and performance matching.

[0081] Step 7: Perform heat treatment on the forging from Step 6;

[0082] Further, step 7 includes: primary annealing: heating to a temperature of 850℃~900℃ and holding for 3 hours; cooling method: air cooling;

[0083] Preferably, the uniformity of the electric furnace is ±10℃;

[0084] Preferably, the transfer time for air cooling of forgings after exiting the furnace is less than or equal to 2 minutes;

[0085] Furthermore, step 7 also includes: secondary annealing: heating the forging to a temperature of 500℃~580℃, holding it at that temperature for 6 hours, and cooling it by air cooling;

[0086] Preferably, the uniformity of the electric furnace is ±5℃;

[0087] Preferably, step 7 further includes: placing the charging plate and forgings within the effective qualified area of ​​the electric furnace; the number of forgings charged into the furnace is selected based on the outer dimensions and weight of the forgings, the effective qualified area of ​​the electric furnace, and the heating power of the electric furnace; a gap of ≥50mm is left between the forgings; the forgings are placed on the charging plate in a single layer and supported and stabilized to prevent deformation of the forgings during heating.

[0088] Example 1

[0089] A certain type of machine joint forging (see) Figure 1a and Figure 1b The material is TC32, the forging dimensions are 630×530×405mm, the design allowance between the forging and one side of the part is 10mm, the draft angle is 7°, and the maximum projected area is 0.27m². 2 The overall cross-sectional thickness of the forging varies considerably, with the maximum vertical dimension being 405mm and the minimum vertical dimension being 57mm, a ratio of 7:1, making it difficult to control the consistency of forging deformation. There are 160-240mm high ribs on both sides of the web, with a rib width of 65mm and a rib height-to-width ratio of 3:1, making forging difficult.

[0090] This invention proposes a forging method for a cross-shaped TC32 titanium alloy die forging, comprising the following steps:

[0091] Step 1: Based on the shape of the part, design the die forging part with a single-sided allowance of 10mm and a draft angle of 7°, and select the maximum projected cross section of 630×530mm as the forging parting surface.

[0092] Step 2: Select Φ300 bar stock as billet. Calculate the blanking length of 700mm based on the forging weight and material utilization rate of numerical simulation. The upsetting height-to-diameter ratio of the bar stock is 7 / 3 < 3, which meets the upsetting ratio requirements for forging.

[0093] Step 3: First, upset the bar stock and shape it into a 375×350mm cuboid; then, reverse the direction of the billet, lengthen the short side, and shape it into an irregular octagonal cube (see...). Figure 2 This ensures that the flow lines of the billet are parallel to the cross-section and consistent with the original flow lines of the bar stock.

[0094] During forging, hammering should be slow to prevent overheating of the core. During upsetting, each hammer blow should reduce the weight by 30-50mm, followed by a lift of the hammer before the second blow. The upsetting speed should be slow and uniform, controlled at 5-8mm / s. During drawing, each hammer blow should feed 80-100mm of the current pressing height, with a reduction of ≤35mm per hammer blow.

[0095] The angles of an octagonal cube should not be too small, and are generally controlled between R50 and 100.

[0096] The side length of the octagonal cube corresponding to the four intersecting directions of the pre-forging cavity should be strictly controlled to avoid damage to the mold bridge.

[0097] Re-firing of hot material into the furnace for reshaping is permitted, and the rough shape can be checked using templates or molds.

[0098] Step 4: Vertically place the octagonal cubic billet into the cavity of the pre-forging die for upsetting, resulting in a cross-shaped pre-forging part that is thick in the middle and thin on both sides (see...). Figure 3a and Figure 3b ).

[0099] Furthermore, pre-forging and upsetting are generally carried out using hydraulic press equipment. The billet is placed in an electric furnace at 100-150°C for preheating for 10-20 minutes, and a lubricant is sprayed on. The coating should be uniform and cover the entire surface of the billet.

[0100] Furthermore, the billet temperature is heated to 30°C–40°C below the phase transformation point;

[0101] The heating coefficient for cold material is 0.6–0.8 min / mm, and the heating coefficient for hot material returning to the furnace is 0.4–0.6 min / mm; during forging, the deformation per forging pass is 25%–30%; the final forging temperature is greater than or equal to 750℃; and the cooling method is air cooling.

[0102] Furthermore: the mold preheating temperature is 250℃~350℃;

[0103] Step 5: Rotate the pre-forging part 90° and place it into the final forging die cavity for cross-shaped forging (see...). Figure 4a and Figure 4b );

[0104] Furthermore, the two wing tabs of the pre-forged part are vertically placed into the final forging cavity, with the smaller tabs facing downwards, to form the narrow, high ribs on the upper and lower sides of the final forging part, and the thick section in the middle, parallel to the mold cavity, to form the large web portion of the final forging part.

[0105] Furthermore, the final forging is carried out on a spiral hammer, with the pressing rate controlled at 0.3–0.5 m / s, and energy increments are set for each hammer strike.

[0106] Step 6: Perform localized section reduction machining on the cross-shaped forging formed in Step 5 to reduce the effective heat treatment thickness of the forging;

[0107] Preferably, in the solid part of the cross-shaped die forging head where the equivalent cross section thickness (inscribed circle diameter) is greater than 120mm, a Φ45 through hole coaxial with the part is added by machining. The purpose is to reduce the effective thickness of the forging, prepare for subsequent heat treatment annealing, and meet the requirements of forging structure and performance matching.

[0108] Step 7: Perform heat treatment on the forging from Step 6;

[0109] Further, step 7 includes: primary annealing: heating to a temperature of 880°C and holding for 3 hours;

[0110] Cooling method: Air cooling.

[0111] Preferably, the uniformity of the electric furnace is ±10℃.

[0112] Preferably, the transfer time for air cooling of forgings after exiting the furnace is less than or equal to 2 minutes;

[0113] Furthermore, step 7 also includes: secondary annealing: heating the forging to a temperature of 550°C and holding it at that temperature for 6 hours;

[0114] Cooling method: Air cooling.

[0115] Preferably, the uniformity of the electric furnace is ±5℃;

[0116] Preferably, step 7 further includes: placing the charging plate and forgings within the effective qualified area of ​​the electric furnace; the number of forgings charged into the furnace is selected based on the outer dimensions and weight of the forgings, the effective qualified area of ​​the electric furnace, and the heating power of the electric furnace; a gap of ≥50mm is left between the forgings; the forgings are placed on the charging plate in a single layer and supported and stabilized to prevent deformation of the forgings during heating.

[0117] After implementation, this invention provides a forging method for cross-shaped TC32 titanium alloy forgings to meet the requirements of key load-bearing joint components for my country's new generation of aircraft. It also provides a billet preparation method for cross-shaped forgings, employing a forging process combining hydraulic press pre-forging and spiral hammer reversing cross-shaped final forging. This ensures that the fiber flow lines of the billet are consistent with the flow lines of the forging, reduces the tonnage required for forging equipment, decreases the number of forging passes, improves production efficiency, increases material utilization, reduces production costs, and ensures a reasonable match between the final shape, microstructure, and properties of the forging, ultimately improving the product qualification rate.

Claims

1. A forging method for a cross-shaped TC32 titanium alloy die forging, characterized in that, include: Bar stock was selected as the billet. Upsetting and shaping of bar stock into cuboids; The billet is reversing and elongated along the short side, and shaped into an irregular octagonal cross-section cube as the billet, ensuring that the flow line direction of the billet is parallel to the cross-section and consistent with the original flow line direction of the bar stock; the web corresponding to the cross-shaped TC32 titanium alloy die forging is larger than the high rib corresponding to the cross-shaped TC32 titanium alloy die forging, and the web material is also more than the high rib material. The billet is placed vertically into the pre-forging mold along its own height direction for upsetting to obtain a cross-shaped pre-forging part; the cross-shaped pre-forging part has ear pieces at both ends; the large ear piece is used to form the high rib with the boss, the small ear piece is used to form the high rib, and the middle part of the pre-forging part is used to form the web. Rotate the pre-forging part by 90° and place it into the final forging mold with the large ear facing upward for cross-shaped forging. Specifically, rotate the pre-forging part by 90° and place it into the final forging mold for cross-shaped forging on the spiral hammer. If the maximum equivalent cross section thickness of a certain part of a cross-shaped forging is greater than 120mm, the thickness of that part should be reduced by machining beforehand. The forgings with reduced thickness after machining are subjected to heat treatment, specifically as follows: The forgings undergo a first annealing process, where they are heated to 850℃~900℃, held for 3 hours, and cooled by air; the furnace uniformity is ±10℃, and the transfer time between the forgings and the air-cooled furnace is less than or equal to 90 seconds; the forgings undergo a second annealing process, where they are heated to 500℃~580℃, held for 6 hours, and cooled by air; the furnace uniformity is ±5℃. Among them, the billet pre-forging process is carried out on a hydraulic press, and the pressing speed is controlled at 2-5 mm / s; The final forging process of the billet is carried out on a spiral hammer, with the pressing rate controlled at 0.3 to 0.5 m / s, and the energy increment is set for each hammer.

2. The method according to claim 1, characterized in that, The preheating temperature range for the forging hammer anvil and other auxiliary tooling is 200℃~300℃.

3. The method according to claim 1, characterized in that, The preheating temperature of the die forging mold is 250℃~350℃; the preheating temperature of the die film is 250℃~350℃.

4. The method according to claim 1, characterized in that, Pre-forging is performed on a hydraulic press.

5. The method according to claim 1, characterized in that, A gap of 100 μm or more is left between forgings in the electric furnace; the forgings are placed on the charging plate, which has ventilation holes or the forgings are supported and placed firmly to prevent deformation of the forgings during heating, which would result in uneven machining allowance of the forgings.

6. The method according to claim 1, characterized in that, The forging parameters in free forging and die forging processes include: The billet is heated to 30℃~40℃ below the phase transformation point; the heating coefficient for cold material is 0.6~0.8 min / mm, and the heating coefficient for hot material returning to the furnace is 0.4~0.6 min / mm. During forging, the deformation per forging pass is 25% to 30%; the final forging temperature is greater than or equal to 750℃.

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