Forging method of large complex TC18 titanium alloy

Abstract

The invention belongs to the field of forging hot working, and relates to a forging method of a large complex TC18 titanium alloy. The method comprises the following steps: selecting a surface parallel to a triangular area of a forge piece as a pre-forging parting surface and a finish-forging parting surface; preparing a spindle-shaped rough shape by adopting a bar material; two ends of the fusiform rough shape are flat plates which are perpendicular to each other; a groove is formed in the rear end of the fusiform horizontal plate, so that shoulder parts on two sides are reserved at the end of the fusiform horizontal plate; specifically, a groove is additionally formed in the upper end face of a horizontal plate, and the inner surface of the groove between shoulder parts on the two sides is changed into an inwards-concave curved surface; a high boss with a semi-elliptic section is formed on the part, above the parting surface, of the fusiform rough vertical plate, a front reinforcing rib of the high boss is formed on the part close to the connecting area of the two plates, and U-shaped grooves penetrating through the height direction are additionally formed in the left side and the right side of the high boss; the part, below the parting surface, of the vertical plate is formed along with the shape; the spindle-shaped rough shape is pre-forged, and a pre-forged piece is obtained; and performing die forging on the pre-forged piece to obtain a forged piece.

Description

Technical Field

[0001] The invention belongs to the field of forging hot processing and relates to a forging method of a large and complex TC18 titanium alloy. Background Art

[0002] TC18 titanium alloy has the characteristics of high strength, high toughness, good hardenability, etc., and is widely used in the aerospace field. At the same time, with the continuous improvement of domestic forging equipment capabilities, aerospace aircraft structural parts have gradually developed from the original welding and assembly of multiple parts to integration, and the structure of forgings has also shown diversity and complexity. With the increase in the difficulty of forging forming and the requirements for organization and performance, higher requirements are also placed on forging forming and process methods.

[0003] A new type of forgings combining a torque arm and a rocker joint for landing gear, the structure of which is (see Figure 1 ), the triangle area 1 is combined with the high boss area 2; its characteristics are: the triangle area 1 is thin and wide with ribs, the high boss area 2 is large and high, and the triangle width L1 is greater than the height L2 of the high boss, and the cross-section of this type of forging varies greatly. At the same time, the deformation and forging temperature of the TC18 titanium alloy forging process have a great influence on the product structure and performance. If such forgings are not designed with pre-forgings or the pre-forgings are designed unreasonably, the unidirectional zone forging is very likely to cause the deformation and temperature field of the forgings to be uneven, thereby causing the forgings to be unqualified in structure and performance, resulting in the problem of forgings being scrapped. Summary of the invention

[0004] Purpose of the invention: The present invention provides a forging method for large and complex TC18 titanium alloy die forgings to meet the requirements for forging forming, and at the same time provides a design method for pre-forgings to improve the uniformity of the structure of the high boss parts and the small surface deformation. At the same time, through the arc design concept, the utilization rate of the forging materials is improved, the production cost is reduced, and the use requirements of key components for the new generation of aircraft landing gear are met.

[0005] Technical solution:

[0006] A forging method for a large and complex TC18 titanium alloy is provided, comprising:

[0007] Select the surface parallel to the triangular area of ​​the forging as the parting surface for the pre-forging and the parting surface for the final forging;

[0008] A spindle-shaped rough shape is prepared by using a rod material; the two ends of the spindle-shaped rough shape are mutually perpendicular flat plates; the rear end of the horizontal plate of the spindle-shaped rough shape has a groove, so that the end leaves shoulders on both sides;

[0009] The spindle-shaped rough shape is pre-forged to obtain a pre-forged part: specifically, a groove is added to the upper end surface of the horizontal plate, and the inner surface of the groove between the shoulders on both sides becomes a concave curved surface; a high boss with a semi-elliptical cross-section is formed on the vertical plate of the spindle-shaped rough shape above the parting surface, and a front side reinforcing rib of the high boss is formed near the connection area of ​​the two plates, and U-shaped grooves penetrating in the height direction are added on the left and right sides of the high boss; the part of the vertical plate below the parting surface is formed in a free-form manner;

[0010] Pre-forging the spindle-shaped rough shape to obtain a pre-forged part;

[0011] The pre-forged piece is die forged to obtain a forging.

[0012] The spindle-shaped rough shape is prepared by using rod material, including:

[0013] Step 1: Select the bar as the blank;

[0014] Step 2: The blank is first upset, squared, and formed into a rectangular parallelepiped; the upsetting ratio is less than or equal to 3;

[0015] Step 3: Turn over the rectangular blank, divide the rectangular blank, use one end as the triangle forming area, and the other end as the high boss forming area; flatten and widen the triangle forming area to form a spindle-shaped horizontal plate; flatten the width of the rectangular blank vertically; widen until one end cannot enter the fetal membrane cavity;

[0016] Step 4: Rotate the blank 90°, place the high boss forming area vertically into the tire membrane, upset and widen the triangular forming area, form the triangular area, and then press a groove in the middle of the end of the triangular area to leave shoulders on both sides of the end of the triangular area;

[0017] Step 5: Take out the blank from the fetal membrane, flatten the high boss forming area to form a spindle-shaped vertical plate, and finally shape it into a spindle-shaped shape.

[0018] The longitudinal section of the reinforcing rib is a triangle. The height of the triangle does not exceed the designed boss height. The width of the triangular rib does not exceed 1 / 3 to 1 / 2 of the designed width of the part. The two sides of the rib width need to be demolded and transitioned with a large R fillet.

[0019] The U-shaped groove should have a draft angle of 1° to 10°; the depth h of the U-shaped groove should be less than 1 / 3 of the diameter of the U-shaped groove, and the convex radius R of the U-shaped groove should be greater than or equal to the concave radius R1.

[0020] Heat treatment parameters for die forging include:

[0021] Primary annealing: heating to 830°C, furnace cooling to 760°C, furnace uniformity is ±10°C;

[0022] Secondary annealing: Heat the forging to a temperature of 616°C with an electric furnace uniformity of ±5°C.

[0023] The volume of the billet is 1.1 to 1.25 times the volume of the forging.

[0024] During heat treatment, the effective thickness of the forging should be determined to be less than or equal to 250mm. For forgings with an effective thickness greater than 150mm, air cooling is adopted, and for forgings with an effective thickness less than or equal to 150mm, air cooling is adopted. For forgings with an effective thickness greater than 250mm, machining is used to reduce the thickness of the forgings before primary annealing.

[0025] During heat treatment, the transfer time of forgings out of the furnace is less than or equal to 2 minutes.

[0026] The beneficial effects are:

[0027] A forging method for large and complex TC18 titanium alloy die forgings is used to meet the use requirements of key components for the new generation of aircraft landing gear. At the same time, a pre-forging design method is provided to improve the uniformity of the structure and the small surface deformation of the high boss part. At the same time, the arc design concept is used to improve the utilization rate of forging materials and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structural features of the forging of the present invention.

[0029] Figure 2 It is a schematic diagram of the rough structure of the present invention.

[0030] Figure 3 This is a schematic diagram of the structural features of the pre-forging of the present invention.

[0031] Figure 4 For the present invention Figure 3 EE section view.

[0032] Figure 5 It is a schematic diagram of the longitudinal section of the U-shaped groove of the high boss side wall of the present invention.

[0033] Figure 6 The figure is a flow chart of the die forging forming of the present invention.

[0034] Figure 7-1 This is a simulation effect diagram of the cross-sectional deformation of the pre-forged part of the present invention.

[0035] Figure 7-2 This is a simulation effect diagram of the deformation of the longitudinal section of the pre-forged part of the present invention.

[0036] Figure 8-1 This is a simulation diagram of the cross-sectional deformation of a conventional pre-forging.

[0037] Figure 8-2 This is a simulation effect diagram of the longitudinal section deformation of a conventional pre-forging. DETAILED DESCRIPTION

[0038] A large and complex TC18 titanium alloy forging method of billet making + die forging (pre-forging + final forging) and a pre-forging design method for improving the uniformity of forging structure are proposed. The specific steps include steps 1 to 6, as follows.

[0039] Step 1: Design the die forging according to the shape of the part. Usually the parting surface is selected to be parallel to the triangle to facilitate the forming of the die forging.

[0040] Preferably, the forging allowance, draft angle, and fillet size are determined according to the part characteristics. For high bosses and parts that are difficult to fill in the die forging, a variable allowance design approach can be adopted to further carry out forging design.

[0041] Step 2: Forging blank making process. The blank making process includes steps 1 to 5, the specific contents are as follows:

[0042] Step 1: Select the bar as the blank. The volume of the blank is 1.1 to 1.25 times the volume of the forging;

[0043] Step 2: The blank is first upset, squared, and formed into a rectangular parallelepiped. The diameter-to-length ratio of the bar (i.e., the upsetting ratio) is less than or equal to 3; the shape and size of the rectangular parallelepiped blank after forming can enter the fetal membrane cavity;

[0044] Step 3: Divide the material, flatten and widen one end. Divide the material according to 1.1 to 1.25 times the volume of the triangular area of ​​the forging; flatten the rectangular parallelepiped vertically in the width direction; widen until one end cannot enter the fetal membrane cavity.

[0045] Step 4: Rotate the blank 90°, place it vertically into the tire membrane, upset and widen the triangular area, press out the middle groove of the triangular area, and leave the shoulder size on both sides.

[0046] The fetal membrane cavity can be designed as a cylinder, a cuboid or a cube. The four faces of the cylinder, the cuboid or the cube have a draft of 1° to 3°, which is easy to demold. At the same time, the volume of the fetal membrane cavity is 1.1 to 1.25 times the volume of the high boss 2 of the forging.

[0047] Step 5: Take out the blank from the fetal membrane, rotate it 90°, flatten the high boss area 2, and shape it into a spindle shape (see Figure 2 ) Wild shape size.

[0048] Step 3: Pre-forging design. Pre-forging design includes the following 4 characteristic elements (see Figure 3 ): The cross section of the high boss is designed to be semi-elliptical A (see EE section view Figure 4 ), the boss and the triangular transition area have reinforcing ribs (B), the high boss side wall is designed with a U-shaped groove running through the height direction (C), and one end of the triangular area is designed to be arc-shaped (D).

[0049] Pre-forgings are designed according to the shape and size of the final forgings. Usually, the maximum projection area of ​​this type of forging is parallel to the triangle, so the parting surface is selected to be parallel to the triangle; the horizontal length and width of the pre-forgings are narrower than the final forgings, and the metal stored in the characteristic parts must meet the forming requirements of the forgings, while the metal flow must meet the deformation requirements of the material.

[0050] Furthermore: a parallel triangular plane is selected as a parting surface, and the cross section of the high boss portion is designed to be a semi-ellipse.

[0051] Purpose: To increase the height of the boss and the deformation of the boss part of the forging; at the same time, the side wall of the pre-forged part can be naturally demolded without the need for demolding, thereby improving design efficiency.

[0052] Furthermore: reinforcing ribs are added at the transition between the high boss and the triangular area. The characteristics of the reinforcing ribs are: the longitudinal section is triangular, the triangle height does not exceed the designed boss height, the triangular rib width does not exceed 1 / 3 to 1 / 2 of the designed width of the part, and the two sides of the rib width need to be demolded and transitioned with large R fillets to avoid defects such as pinching and folding in the forgings.

[0053] Usually, the design method for this part is a large R fillet transition; the design of the reinforcing ribs significantly improves the problem of the difference in deformation between the core and the surface of the high boss;

[0054] Further: the high boss side wall is designed to have a U-shaped groove running through the height direction, and the side wall groove should have a draft of 1° to 10°; the side wall is dug with a U-shaped groove (see Figure 5 ), in order to ensure that the forging does not have defects such as pinching and folding, the U-shaped groove should not be too deep, where h < 1 / 3b, R ≥ R1;

[0055] Purpose: To improve the tissue differences caused by the dead area of ​​surface deformation or small deformation.

[0056] Furthermore: the middle part of one end of the triangular area is designed to be in an arc shape.

[0057] The purpose of arc design is to reduce the material consumption of forgings in the triangular area, improve the uniformity of the structure, and improve the structural differences caused by excessive deformation due to the large amount of metal flowing into the burrs.

[0058] Step 4: Place the formed blank in the pre-forging die cavity to perform pre-forging forming.

[0059] Preferably, step 2 and step 4 further include: heating the blank or rough blank to 30°C to 40°C below the phase change point; the heating coefficient of the cold material is 0.6 to 0.8 min / mm, and the heating coefficient of the hot material is 0.3 to 0.4 min / mm;

[0060] Preferably, step 2 and step 4 further include: heating in an electric furnace at ±10°C;

[0061] Step 5: Place the pre-forged part in the final forging die cavity for final forging.

[0062] Preferably, step 5 further comprises: heating the pre-forged piece to 30°C to 40°C below the phase transition point,

[0063] Temperature coefficient 0.6~0.8min / mm, then heat up to 15℃~25℃ above the phase change point, insulation coefficient 0.3~0.4min / mm, hot material is not allowed to return to the furnace; preferably ±5℃ electric furnace heating, use patrol meter to control material temperature; before loading, ensure that the heating furnace equipment is in good condition, when loading, the billet is supported, and a gap of 60~100mm is left between the billets for heating. Purpose: The billet is fully and evenly heated to avoid the heating effect affected by factors such as improper heating furnace and loading.

[0064] Preferably, step 2, step 4, and step 5 further include: during forging, the deformation amount per fire is

[0065] 20%~50%; final forging temperature is greater than or equal to 720℃; cooling method is air cooling.

[0066] Preferably, step 4 and step 5 further include: placing the blank or pre-forged part at 100°C to 150°C

[0067] Preheat in an electric furnace for 10 to 40 minutes. After preheating, spray the coating evenly on the entire surface of the blank or pre-forging. Titanium-5 is used as the spraying agent. The purpose is to reduce the metal flow resistance. During forging, the upper and lower mold cavities are covered with 5 to 10 mm thick insulation cotton or insulation cloth. The insulation cloth is made of high-silica fiber cloth. The purpose is to reduce the metal cooling rate and ensure the forming process of the pre-forging and the final forging; at the same time, reduce the organizational differences caused by the different temperature drop rates between the surface and the core of the metal billet. The mold preheating temperature is 250℃~450℃;

[0068] Step 6: heat treating the forging of step 5;

[0069] Further, step 6 includes: primary annealing: heating to a temperature of 820°C to 850°C, furnace cooling to 740°C to 760°C, cooling method: air cooling or wind cooling.

[0070] Preferably: the uniformity of the electric furnace is ±10°C,

[0071] Preferably: the time for transferring the forging out of the furnace is less than or equal to 2 minutes;

[0072] Preferably: the effective thickness of the forging should be less than or equal to 250mm. For forgings with an effective thickness greater than 150mm, air cooling is adopted, and for forgings with an effective thickness less than or equal to 150mm, air cooling is adopted. For forgings with an effective thickness greater than 250mm, machining is used to reduce the thickness of the forgings before primary annealing.

[0073] Furthermore, step 6 also includes: secondary annealing: heating the forging to a temperature of 500° C. to 650° C., and cooling method: air cooling.

[0074] Preferably, the furnace uniformity is ±5°C;

[0075] Preferably, step 6 specifically also includes: placing the charging plate and forgings in the effective qualified area of ​​the electric furnace; the number of forgings loaded into the furnace is selected according to the outer dimensions and weight of the forgings, the effective qualified area of ​​the electric furnace and the heating power of the electric furnace; leaving a gap of 50 to 100 mm or more between the forgings; the forgings are placed on the charging plate, and the charging plate has air holes or the forgings are supported and padded to prevent deformation of the forgings during the heating process, resulting in uneven machining allowance of the forgings.

[0076] Example

[0077] A certain type of machine rear rocker arm joint die forging (see Figure 1 ), material is TC18, forging outline size: 1287×887×538, single side volume 8~10mm, maximum projection area is 0.596m 2 , phase transition point: 872℃, the forging method of this patent, such as Figure 6 As shown, the following steps are included:

[0078] Step 1: Design the die forging according to the shape of the part and select the parting surface parallel to the triangle.

[0079] Step 2: Forging blank making process. The blank making process includes steps 1 to 5, the specific contents are as follows:

[0080] Step 1: Selection The bar is used as the blank. The volume of the blank is 1.1 to 1.25 times the volume of the forging;

[0081] Step 2: The blank is first upset, squared, and formed into a rectangular parallelepiped. The diameter-to-length ratio of the bar (i.e., the upsetting ratio) is less than or equal to 3; the shape and size of the rectangular parallelepiped blank after forming can enter the fetal membrane cavity;

[0082] Step 3: Divide the material, flatten and widen one end. Divide the material according to 1.1 to 1.25 times the volume of the triangular area of ​​the forging; flatten the rectangular parallelepiped vertically in the width direction; widen until one end cannot enter the fetal membrane cavity.

[0083] Step 4: Rotate the blank 90°, place it vertically into the tire membrane, upset and widen the triangular area, press out the middle groove of the triangular area, and leave the shoulder size on both sides.

[0084] The fetal membrane cavity can be designed as a cylinder, a cuboid or a cube. The four faces of the cylinder, the cuboid or the cube have a draft of 1° to 3°, which is easy to demold. At the same time, the volume of the fetal membrane cavity is 1.1 to 1.25 times the volume of the high boss 2 of the forging.

[0085] Step 5: Take out the blank from the fetal membrane, rotate it 90°, flatten the high boss area 2, and shape it into a spindle shape (see Figure 2 ) Wild shape size.

[0086] Step 3: Pre-forging design. Pre-forging design includes the following 4 characteristic elements (see Figure 3 ): The cross section of the high boss is designed to be semi-elliptical A (see EE section view Figure 4 ), the boss and the triangular transition area have reinforcing ribs (B), the high boss side wall is designed with a U-shaped groove running through the height direction (C), and one end of the triangular area is designed to be arc-shaped (D).

[0087] Pre-forgings are designed according to the shape and size of the final forgings. Usually, the maximum projection area of ​​this type of forging is parallel to the triangle, so the parting surface is selected to be parallel to the triangle; the horizontal length and width of the pre-forgings are narrower than the final forgings, and the metal stored in the characteristic parts must meet the forming requirements of the forgings, while the metal flow must meet the deformation requirements of the material.

[0088] Furthermore: a parallel triangular plane is selected as a parting surface, and the cross section of the high boss portion is designed to be a semi-ellipse.

[0089] Purpose: To increase the height of the boss and the deformation of the forging; at the same time, the side wall of the pre-forged part does not need to be drafted, and the forging can be naturally demolded, thereby improving design efficiency.

[0090] Furthermore: reinforcing ribs are added at the transition between the high boss and the triangular area. The characteristics of the reinforcing ribs are: the longitudinal section is triangular, the triangle height does not exceed the designed boss height, the triangular rib width does not exceed 1 / 3 to 1 / 2 of the designed width of the part, and the two sides of the rib width need to be demolded and transitioned with large R fillets to avoid defects such as pinching and folding in the forgings.

[0091] Usually, the design method for this part is a large R fillet transition; the design of the reinforcing ribs significantly improves the problem of the difference in deformation between the core and the surface of the high boss;

[0092] Further: the high boss side wall is designed to have a U-shaped groove running through the height direction, and the side wall groove should have a draft of 1° to 10°; the side wall is dug with a U-shaped groove (see Figure 5 ), in order to ensure that the forging does not have defects such as pinching and folding, the U-shaped groove should not be too deep, where h < 1 / 3b, R ≥ R1;

[0093] Purpose: To improve the tissue differences caused by the dead area of ​​surface deformation or small deformation.

[0094] Furthermore: the middle part of one end of the triangular area is designed to be in an arc shape.

[0095] The purpose of arc design is to reduce the material consumption of forgings in the triangular area, improve the uniformity of the structure, and improve the structural differences caused by excessive deformation due to the large amount of metal flowing into the burrs.

[0096] The design effect of the present invention is compared by simulation software:

[0097] Figure 7-1 and Figure 7-2 : Simulation effect diagram of deformation from pre-forging to final forging of the present invention

[0098] Figure 8-1 and Figure 8-2 :Conventional pre-forging design to final forging deformation simulation effect diagram

[0099] Step 4: Place the formed blank in the pre-forging die cavity to perform pre-forging forming.

[0100] Step 5: Place the pre-forged part in the final forging die cavity for final forging.

[0101] Step 6: heat treating the forging of step 5;

[0102] Furthermore, step 6 includes: primary annealing: heating to a temperature of 830° C., furnace cooling to 760° C., cooling method: air cooling.

[0103] Furthermore, step 6 also includes: secondary annealing: heating the forging to a temperature of 616° C., cooling method: air cooling.

[0104] The physical and chemical properties of the forgings produced by the above method meet the standard requirements. The physical and chemical property results are shown in Table 1. When designing the pre-forging, the reliability of the positioning of the pre-forging in the final forging die cavity is also considered to meet the use requirements of key components for the new generation of aircraft landing gear; improve the utilization rate of forging materials, reduce production costs, provide new design ideas and methods for the production of this type of forgings, and provide reliability for subsequent batch production.

[0105] Table 1 Mechanical test results of forgings

[0106]

[0107]

Claims

1. A forging method for a large and complex TC18 titanium alloy, characterized in that: include: Select the surface parallel to the triangular area of ​​the forging as the parting surface for the pre-forging and the parting surface for the final forging; A spindle-shaped rough shape is prepared by using a rod material; the two ends of the spindle-shaped rough shape are mutually perpendicular flat plates; the rear end of the horizontal plate of the spindle-shaped rough shape has a groove, so that the end leaves shoulders on both sides; The spindle-shaped rough shape is pre-forged to obtain a pre-forged part: specifically, a groove is added to the upper end surface of the horizontal plate, and the inner surface of the groove between the shoulders on both sides becomes a concave curved surface; a high boss with a semi-elliptical cross-section is formed on the vertical plate of the spindle-shaped rough shape above the parting surface, and a front side reinforcing rib of the high boss is formed near the connection area of ​​the two plates, and U-shaped grooves penetrating in the height direction are added on the left and right sides of the high boss; the part of the vertical plate below the parting surface is formed in a free-form manner; Pre-forging the spindle-shaped rough shape to obtain a pre-forged part; The pre-forged piece is die forged to obtain a forging.

2. The method according to claim 1, characterized in that The spindle-shaped rough shape is prepared by using rod material, including: Step 1: Select the bar as the blank; Step 2: The blank is first upset, squared, and formed into a rectangular parallelepiped; the upsetting ratio is less than or equal to 3; Step 3: Turn over the rectangular blank, divide the rectangular blank, use one end as the triangle forming area, and the other end as the high boss forming area; flatten and widen the triangle forming area to form a spindle-shaped horizontal plate; flatten the width of the rectangular blank vertically; widen until one end cannot enter the fetal membrane cavity; Step 4: Rotate the blank 90°, place the high boss forming area vertically into the tire membrane, upset and widen the triangular forming area, form the triangular area, and then press a groove in the middle of the end of the triangular area to leave shoulders on both sides of the end of the triangular area; Step 5: Take out the blank from the fetal membrane, flatten the high boss forming area to form a spindle-shaped vertical plate, and finally shape it into a spindle-shaped shape.

3. The method according to claim 2, characterized in that The longitudinal section of the reinforcing rib is a triangle. The height of the triangle does not exceed the designed boss height. The width of the triangular rib does not exceed 1 / 3 to 1 / 2 of the designed width of the part. The two sides of the rib width need to be demolded and transitioned with a large R fillet.

4. The method according to claim 3, characterized in that The U-shaped groove should have a draft angle of 1° to 10°; the depth h of the U-shaped groove should be less than 1 / 3 of the diameter of the U-shaped groove, and the convex radius R of the U-shaped groove should be greater than or equal to the concave radius R1.

5. The method according to claim 1, characterized in that: Heat treatment parameters for die forging include: Primary annealing: heating to 830°C, furnace cooling to 760°C, furnace uniformity is ±10°C; Secondary annealing: Heat the forging to a temperature of 616°C with an electric furnace uniformity of ±5°C.

6. The method according to claim 1, characterized in that The volume of the billet is 1.1 to 1.25 times the volume of the forging.

7. The method according to claim 5, characterized in that During heat treatment, the effective thickness of the forging should be determined to be less than or equal to 250mm. For forgings with an effective thickness greater than 150mm, air cooling is adopted, and for forgings with an effective thickness less than or equal to 150mm, air cooling is adopted. For forgings with an effective thickness greater than 250mm, machining is used to reduce the thickness of the forgings before primary annealing.

8. The method according to claim 5, characterized in that During heat treatment, the transfer time of forgings out of the furnace is less than or equal to 2 minutes.

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