Forging method for Ti55531 titanium alloy outer cylinder with large cross section difference

Abstract

The invention belongs to the field of forging hot working, and relates to a forging method for a Ti55531 titanium alloy outer cylinder with large cross section difference. The method comprises the following steps: squaring a bar; the small-section part and the large-section part of the forge piece on the square billet are divided into a material D1 used for forming the small-section part of the forge piece and a material D2 used for forming the large-section part of the forge piece; drawing out for D1 along the streamline direction of the square billet; the drawn D1 enters a moulding bed, and the moulding bed is used for pressing the D2 part, so that the two sides of the D2 form transition slopes with the D1; drawing out and pressing a D2 end part processing boss part by combining a moulding bed and a plate opening tool; the blank mold is taken out, and the pressed D2 is drawn out in the streamline direction; repeatedly pressing and drawing until the fall of the boss part meets the design requirement; and the D1 of the part entering the forming die is drawn out in the streamline direction, and a rough blank of the outer cylinder forge piece is obtained through shaping.

Description

Technical Field

[0001] The invention belongs to the field of forging hot processing and relates to a forging method for a Ti55531 titanium alloy outer cylinder with large cross-section difference. Background Art

[0002] Ti55531 titanium alloy is a high-strength metastable β-type titanium alloy developed by Russia's VSMPO and Europe's Airbus based on BT22 (domestic grade TC18). The alloy has the advantages of low processing cost, good fracture toughness and high strength matching characteristics, good hardenability, insensitivity to segregation, and a wide range of processing technology. It is gradually being promoted and applied in aircraft landing gear structures.

[0003] However, since the alloy contains high content of β-phase stabilizing elements such as Mo, V, and Cr in its chemical composition, it can still maintain a complete β phase after quenching, so it has a low α / β transformation temperature. This characteristic makes large forgings, especially die forgings with large cross-section differences, prone to the following problems during the forging process: 1. The phase transition point is low, the billet temperature is low during forging, and the deformation resistance is large; 2. Excessive deformation in a single fire can easily cause overheating of the core, resulting in uneven organizational properties; 3. Due to the low temperature of the forging billet and inappropriate selection of forging steps, the temperature loss at the small cross-section may be too fast, resulting in repeated re-melting, which increases the cost of forgings, reduces production efficiency, and even damages the billet. Summary of the invention

[0004] The present invention is intended to provide a forging method for Ti55531 titanium alloy outer cylinder die forgings with large cross-section differences, and to provide a blanking method for outer cylinder forgings with large cross-section differences and fast cross-section changes on the basis of meeting the performance and use requirements of key parts for a new generation of aircraft landing gear. By selecting appropriate blanking steps, the number of forging fires can be reduced as much as possible on the basis of ensuring the deformation of the forgings, thereby achieving the purpose of reducing the production cost and scrap rate of forgings, improving production efficiency, and the final uniformity of the forgings.

[0005] Technical solution:

[0006] Provided is a forging method for a Ti55531 titanium alloy outer cylinder having a large cross-sectional difference, comprising:

[0007] Square the rod;

[0008] Divide the small cross-section part and the large cross-section part of the forging on the billet into material D1 for forming the small cross-section part of the forging and material D2 for forming the large cross-section part of the forging; draw D1 along the streamline direction of the billet;

[0009] Put the stretched D1 into the tire mold, and use the tire mold to press the D2 part, so that the two sides of D2 form a transition slope with D1; use the tire mold and the plate-opening tooling to stretch and press the end of D2 to process the boss part; exit the tire membrane, stretch the pressed D2 along the streamline direction; repeat the pressing and stretching until the height difference of the boss part meets the design requirements;

[0010] The D1 of the membrane inlet is stretched along the streamline direction and shaped to obtain the rough blank of the outer cylinder forging.

[0011] Furthermore, the cross-sectional area S of the billet 方 Slightly larger than the cross-sectional area S of the rod 棒材 .

[0012] Furthermore, the material is divided by calculating the weight or volume of the large cross-sectional portion D1 using three-dimensional software.

[0013] Furthermore, during the drawing process, the hammer anvil is preheated to 200°C to 300°C, and thermal insulation cotton is placed between the hammer anvil and the blank, and between the blank and the workbench.

[0014] Furthermore, the method further comprises:

[0015] Determine the placement position of the blank, place it in the die cavity, and perform die forging;

[0016] Perform rough machining of forgings before heat treatment according to the part structure to reduce the effective thickness of forgings;

[0017] Heat treatment is performed on forgings after rough machining before heat treatment.

[0018] Furthermore, the heating temperature of the membrane drawing and die forging is 40-60℃ below the phase change point; the heating coefficient of the cold material is 0.6-0.8min / mm, the heating coefficient of the hot material reheating is 0.4-0.6min / mm, the deformation of a single fire is as far as possible between 25% and 35%, the final forging temperature is greater than 750℃, and air cooling is used;

[0019] The mold and fetal membrane should be preheated for ≥24 hours in advance, and the preheating temperature should reach 250-300℃.

[0020] Furthermore, the heat treatment includes two types of heat treatment: "solid solution + aging" and "β annealing + aging".

[0021] Furthermore, the electric furnace should be Grade III or above in GJB904, and an electric furnace with self-cooling and controllable cooling rate should be selected for "β annealing + aging" heat treatment.

[0022] The beneficial effects are:

[0023] The present invention provides a forging method for a Ti55531 titanium alloy outer cylinder die forging with a variable cross-section, so that in the process of blank making and die forging, a suitable deformation amount and forging steps are selected, thereby achieving the purpose of reducing the number of forging fires as much as possible, reducing the production cost of forgings, improving production efficiency, and improving the final uniformity of the forging structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the digital model of the outer cylinder forging.

[0025] Figure 2 Schematic diagram of the forging structure.

[0026] Figure 3 The figure is a flow chart of the forging method for a Ti55531 titanium alloy outer cylinder with large cross-sectional differences. DETAILED DESCRIPTION

[0027] The present invention is intended to provide a forging method for a Ti55531 titanium alloy outer cylinder with large cross-sectional differences, such as Figure 3 As shown, the specific steps are as follows:

[0028] Step 1: Design the die forging according to the part structure, shape and the difficulty of filling the complex parts. Plane parting is usually used. For complex forgings, curved surface parting can be selected.

[0029] Preferably, according to the structural characteristics, size and difficulty of forming special structures or parts in the forgings, appropriate machining allowances, draft degrees and transition radius should be selected during forging design. For complex parts in the part structure (such as high bosses or multiple bosses), the machining allowance can be appropriately increased, and for parts that are easy to form, the machining allowance can be appropriately reduced.

[0030] Step 2: According to the maximum cross-sectional area S of the designed forging 锻件 , and consider the allowable underpressure and rough edge bin design specified in the drawing, select the appropriate bar specification, usually the bar cross-sectional area S 棒材 Should be slightly larger than S 锻件 ;

[0031] Further, according to the forging structure, the large cross-section part and the small cross-section part of the forging are divided into two parts, D1 and D2 (such as Figure 2 ), use 3D software to calculate the weight or volume of the large cross-section part D1 for division.

[0032] Step 3: Square the bar to ensure the cross-sectional area S of the square billet 方 Slightly larger than the cross-sectional area S of the rod 棒材 , the length L1 is calculated based on the weight / volume of D1, and this part of the material is used for forming D1;

[0033] Furthermore, at a phase transition point of 40 to 60°C, any side of the billet is selected as the starting point, and the end point position of L1 is measured in the length direction. While keeping the thickness direction unchanged, the plate is opened for dividing the material and lengthening L1.

[0034] Preferably, the hammer anvil is preheated to 200°C to 300°C, and heat-insulating cotton is placed between the hammer anvil and the blank, and between the blank and the workbench during pressing.

[0035] Step 4: Place the forging D1 into the die, and use the die to press the D2 part to form the angle and width of the D2 part (see Figure 3 );

[0036] Further, at 40-60°C below the phase transition point, the boss part of the tail of the forging is stretched and pressed by combining the mold, plate opening and other tooling (see Figure 3 ).

[0037] Preferably, the hammer anvil is preheated to 200°C to 300°C, the fetal membrane is preheated to 250°C to 300°C before entering the fetal membrane, and thermal insulation cotton is placed between the hammer anvil and the blank, and between the blank and the workbench.

[0038] Step 5: After the fetal membrane is removed, the fetal membrane portion (i.e., portion D1) in step 4 is stretched and shaped at a temperature of 40 to 60° C. below the phase transition point to obtain a rough blank of the outer cylinder forging;

[0039] Furthermore, depending on the shape of the outer cylinder, some outer cylinder forgings require the blank to be bent (see Figure 3 ).

[0040] Preferably, the anvil is preheated to 200°C to 300°C.

[0041] Step 6: Determine the placement position of the blank, place it in the mold cavity, and perform die forging at 40-60°C below the phase change point;

[0042] Furthermore, the heating coefficient of the cold material between step 4 and step 6 is 0.6-0.8 min / mm, the heating coefficient of the hot material returning to the furnace is 0.4-0.6 min / mm, the deformation amount of a single fire is as far as possible between 25% and 35%, the final forging temperature is greater than 750°C, and air cooling is performed;

[0043] Furthermore, the mold is preheated for ≥24 hours in advance, and the preheating temperature reaches 250-300°C.

[0044] Preferably, the blank is sprayed with a special heat-insulating and lubricating layer before entering the furnace, and a lubricant is sprayed in advance in the cavity in preparation for die forging, and a heat-insulating layer is covered on the surface of the blank.

[0045] Step 7: Perform pre-heat roughing on the forgings forged in step 6 according to the part structure to reduce the effective thickness of the forgings;

[0046] Preferably, the maximum effective thickness of the forging is reduced as much as possible before heat treatment to meet the requirements of the forging structure and performance.

[0047] Step 8: Heat treatment of the forging after rough machining before heat treatment;

[0048] Furthermore, step 8 includes two heat treatment states: "solid solution + aging" and "β annealing + aging", and the corresponding heat treatment system is selected according to the application requirements;

[0049] Preferably: the electric furnace is selected from the GJB904 grade III or above electric furnace, and the electric furnace with self-cooling and controllable cooling rate should be selected for the "β annealing + aging" heat treatment.

[0050] A certain project outer cylinder die forging (see Figure 1 ), material Ti55531, forging outline size: 1575×583×342, forging single-side machining allowance 8~10mm, projected area 0.45m 2 .

[0051] The forging method of the present invention comprises the following steps:

[0052] Step 1: According to the specific structure of the part and considering the difficulty of filling the complex parts, the plane parting is selected when designing the forging.

[0053] Step 2: Maximum cross-sectional area S of forging 锻件 =0.087m 2 Considering the allowable underpressure and burr bin design of forgings, Φ350 bar is selected for forging rough blanks. 锻件 =0.087m 2 <S=0.096m 2 .

[0054] Further, according to the forging structure, the forging is divided into two parts, D1 and D2 (such as Figure 2 ), use 3D software to calculate the weight m1 of D1.

[0055] Step 3: Square the rod so that S 方 =0.108m 2 ≥S 棒材 =0.096m 2 , calculate the material length L1 according to the weight of D1.

[0056] Furthermore, at a phase transition point of 40 to 60° C., any side of the billet is selected as the starting point, and the end point position L1 is measured in the length direction. While keeping the thickness direction unchanged, the open plate is used to divide the material and lengthen the billet.

[0057] Preferably, the hammer anvil is preheated to 200°C to 300°C, and heat-insulating cotton is placed between the hammer anvil and the blank, and between the blank and the workbench during pressing.

[0058] Step 4: Put the rough blank D1 part after the material is divided and stretched into the tire mold, and shape the angle and width of the D2 part at 40-60°C below the phase change point;

[0059] Further, at 40-60°C below the phase transition point, the sizes of L2 and L3 are determined in combination with the tire mold and the opening plate, as well as the position of the tail processing table, and the processing boss part of the blank D3 part is stretched and pressed (see Figure 3 ).

[0060] Preferably, the hammer anvil is preheated to 200°C to 300°C, the membrane is preheated to 250°C to 300°C before entering the membrane, and insulation cotton is placed between the hammer anvil and the blank, and between the blank and the workbench;

[0061] Step 5: After the fetal membrane is removed, the fetal membrane portion (i.e., portion D1) in step 4 is stretched and shaped at a temperature of 40 to 60° C. below the phase transition point to obtain a rough blank of the outer cylinder forging;

[0062] Furthermore, the blank is bent according to the shape of the forging, and the bending angle is determined by combining the material swing of the mold cavity or making a special template.

[0063] Step 6: Determine the placement position of the blank, place it in the mold cavity, and perform die forging at 40-60°C below the phase change point;

[0064] Furthermore, the heating coefficient of the cold material between step 4 and step 6 is 0.6-0.8 min / mm, the heating coefficient of the hot material returning to the furnace is 0.4-0.6 min / mm, the deformation amount of a single fire is as far as possible between 25% and 35%, the final forging temperature is ≥750°C, and air cooling is performed;

[0065] Furthermore, the mold is preheated for ≥24 hours in advance, and the preheating temperature reaches 250-300°C.

[0066] Preferably, the blank is sprayed with a special heat-insulating and lubricating layer before entering the furnace, and a lubricant is sprayed in advance in the cavity in preparation for die forging, and a heat-insulating layer is covered on the surface of the blank.

[0067] Step 7: Perform pre-heat roughing on the forgings forged in step 6 according to the part structure to reduce the effective thickness of the forgings;

[0068] Preferably, the maximum effective thickness of the forging is reduced as much as possible before heat treatment to meet the requirements of the forging structure and performance.

[0069] Step 8: Heat treat the forging after rough machining before heat treatment. According to the use requirements, the "β annealing + aging" heat treatment method is selected;

[0070] Further, step 8 comprises: placing the material in a warm furnace at 30-60°C below the phase change point, keeping the temperature for 100-150 minutes, then heating the material to 10-20°C above the phase change point and keeping the temperature for 100-150 minutes, then cooling the material to 540-580°C at a rate of 1.5-3.0°C / min, keeping the temperature for 8-10 hours, and then cooling the material out of the furnace in air;

[0071] Preferably: an electric furnace with self-cooling and controllable cooling rate is selected.

[0072] After the implementation of the present invention, by providing a variable-section Ti55531 titanium alloy outer cylinder die forging forging method, on the basis of meeting the use requirements of key components for a new generation of aircraft landing gear, by selecting appropriate deformation amount and forging steps, as well as the deformation amount in the process of billet making and die forging, the purpose of reducing the number of forging fires and reducing the production cost of forgings is achieved. At the same time, the forgings are machined before heat treatment, and the maximum effective thickness of the forgings is reduced, the hardenability of the forgings is increased, the uniformity of the final organizational performance of the forgings is achieved, and the first-time qualified rate is improved.

Claims

1. A forging method for a Ti55531 titanium alloy outer cylinder with large cross-section differences, characterized in that: include: Square the rod; Divide the small cross-section part and the large cross-section part of the forging on the billet into material D1 for forming the small cross-section part of the forging and material D2 for forming the large cross-section part of the forging; draw D1 along the streamline direction of the billet; Put the stretched D1 into the tire mold, and use the tire mold to press the D2 part, so that the two sides of D2 form a transition slope with D1; use the tire mold and the plate-opening tooling to stretch and press the end of D2 to process the boss part; exit the tire membrane, stretch the pressed D2 along the streamline direction; repeat the pressing and stretching until the height difference of the boss part meets the design requirements; The D1 of the membrane inlet is stretched along the streamline direction and shaped to obtain the rough blank of the outer cylinder forging.

2. The method according to claim 1, characterized in that Billet cross-sectional area S 方 Slightly larger than the cross-sectional area S of the rod 棒材 .

3. The method according to claim 1, characterized in that The material is divided by calculating the weight or volume of the large cross-section part D1 using three-dimensional software.

4. The method according to claim 1, characterized in that: During the drawing process, the hammer anvil is preheated to 200℃~300℃, and insulation cotton is placed between the hammer anvil and the blank, and between the blank and the workbench.

5. The method according to claim 1, characterized in that The method further comprises: Determine the placement position of the blank, place it in the die cavity, and perform die forging; Perform rough machining of forgings before heat treatment according to the part structure to reduce the effective thickness of forgings; Heat treatment is performed on forgings after rough machining before heat treatment.

6. The method according to claim 5, characterized in that The heating temperature of the membrane drawing and die forging is 40-60℃ below the phase change point; the heating coefficient of cold material is 0.6-0.8min / mm, the heating coefficient of hot material reheating is 0.4-0.6min / mm, the deformation of single fire is as far as possible within 25%-35%, the final forging temperature is greater than 750℃, and air cooling is used; The mold and fetal membrane should be preheated for ≥24 hours in advance, and the preheating temperature should reach 250-300℃.

7. The method according to claim 5, characterized in that Heat treatment includes: There are two heat treatments: "solid solution + aging" and "β annealing + aging".

8. The method according to claim 7, characterized in that The electric furnace should be Grade III or above in GJB904. For "β annealing + aging" heat treatment, an electric furnace with self-cooling and controllable cooling rate should be selected.

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