Forging method for improving fatigue performance of side support die forging of aircraft landing gear

Abstract

The invention discloses a forging method for improving the fatigue performance of a side support die forging of an aircraft landing gear, belongs to the field of metal die forging, and aims to improve the fatigue performance. Comprising the following steps that S1, a round bar is heated through first fire to form a blank, and the cross section of the blank is matched with the cross section of a final forging in the length direction; s2, the blank is returned to a furnace and heated, positioning forging is conducted in the tire mold, a pre-forged piece is formed, and a positioning groove corresponding to the groove of the undercarriage side supporting die forging, a notch corresponding to the notch and a protruding rib corresponding to the transition rib are forged in the bottom of the pre-forged piece; and S3, the pre-forged piece is remelted and heated, the heated pre-forged piece is installed in a final forging die to be subjected to final forging, a final forged piece is obtained, and the final forging temperature is larger than or equal to 720 DEG C. And the round bar material is lower than the traditional finish forging temperature, so that inclusions are partially diffused in the forging process, the material is more uniform, and the fatigue performance is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal die forging, and in particular relates to a forging method for improving the fatigue performance of a side support die forging of an aircraft landing gear. Background Art

[0002] The landing gear is the main load-bearing structure of the aircraft, which is used to realize the take-off, taxiing, landing and parking of the aircraft and absorb the impact kinetic energy of the aircraft during landing. The side support is mainly used to keep the landing gear in the extended position, and at the same time bear the unbalanced force generated by the landing gear in the lateral direction, so that the landing gear moves in the predetermined direction. Its working conditions determine that it must have high fatigue performance. Figure 1 Disclosed is a side support of an aircraft landing gear, which is made of 300M steel and is in an I-shape. The web gradually widens from the left end to the right end along its length direction. The left end of the web is provided with an inward-concave groove 11, and the two sides of the right end of the web are provided with oppositely arranged protrusions 12. The bottom ends of the two protrusions 12 are connected through transition ribs 13. The right end of the web is provided with an inward-concave notch 14, and the notch 14 passes through the right end of the web of the landing gear side support die forging 1 along the length direction. At present, the forging process of the aircraft landing gear side support die forging is as follows: first, the square bar material is drawn to form a blank, and then die forging is performed, and the die forging temperature is 1050-1080°C. During use, it is found that the fatigue performance of the aircraft landing gear side support die forging needs to be improved. Summary of the invention

[0003] The object of the present invention is to provide a forging method for improving the fatigue performance of a side support die forging of an aircraft landing gear, so that the die forging has excellent fatigue performance.

[0004] The technical scheme adopted by the present invention is: a forging method for improving the fatigue performance of an aircraft landing gear side support die forging, wherein the material of the landing gear side support die forging is 300M, the landing gear side support die forging is in an I-shape, and the web gradually widens from the left end to the right end along its length direction, the left end of the web is provided with an inwardly concave groove, and the two sides of the right end of the web are provided with protrusions arranged oppositely, the bottom ends of the two protrusions are connected through transition ribs, and the right end of the web is provided with an inwardly concave notch, and the notch penetrates the right end of the web of the landing gear side support die forging along the length direction; comprising the following steps:

[0005] S1. The round bar is first heated to form a blank, and the cross section of the blank along the length direction matches the cross section of the final forging;

[0006] S2, the blank is returned to the furnace for heating, and local deformation positioning forging is performed in the tire membrane to form a pre-forged part, wherein the bottom of the pre-forged part is forged with a positioning groove corresponding to the groove of the landing gear side support die forging, a notch corresponding to the notch, and a protruding rib corresponding to the transition rib;

[0007] S3. The pre-forged parts are returned to the furnace for heating. After heating, the pre-forged parts are installed in the final forging die for final forging to obtain the final forging parts. The final forging temperature is ≥720℃.

[0008] Furthermore, the blank is square along its length and includes a rod portion and an expanded head portion at one end of the rod portion, and the cross sections of the rod portion and the expanded head portion are both circular.

[0009] Furthermore, the pre-forging is circular in shape.

[0010] Furthermore, a positioning plane extending along the length direction of the pre-forging is formed between the positioning groove and the notch of the pre-forging.

[0011] Furthermore, the pre-forging is 15-20 mm longer than the final forging.

[0012] Furthermore, the forging heating temperature is 1150-1200°C.

[0013] Furthermore, after each firing, the heated parts are returned to the furnace, and the heat preservation time of the hot parts is 30-60 minutes.

[0014] The beneficial effects of the present invention are as follows: the forging method for improving the fatigue performance of the aircraft landing gear side support die forging disclosed in the present invention changes the traditional form of using square bars to form blanks through free forging, and uses round bars to form blanks through upsetting or drawing. Compared with square bars, the metal flow intensity of round bars is relatively weaker, which greatly reduces the risk of reduced fatigue performance.

[0015] The final forging temperature adopted by the present invention is lower than the traditional forging temperature, so that the inclusions are partially diffused during the forging process, the material is more uniform, and the fatigue performance is improved.

[0016] The present invention adopts a forging process of drawing-pre-forging-final forging, and the pre-forging process of this embodiment is different from conventional pre-forging. The pre-forging disclosed in this embodiment is positioning forging in the fetal membrane. The so-called positioning forging refers to designing a suitable fetal membrane according to the characteristics of the final forging, and the blank undergoes local small deformation in the fetal membrane, so that the pre-forging formed by the pre-forging forms an adaptive positioning with the final forging die. The local small deformation during the pre-forging process reduces the intensity of metal flow and does not lead to a decrease in fatigue performance. The pre-forging formed by the pre-forging forms an adaptive positioning with the final forging die, which reduces the swinging time and ensures that the metal flow fully fills the cavity at the end. The final forging has good appearance and uniform structure, and the final forging process is stably controlled with uniform quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the side support die forging;

[0018] Figure 2 This is a schematic diagram of the blank after the first firing in the embodiment;

[0019] Figure 3 Schematic diagram of a pre-forged piece after the second firing in the embodiment;

[0020] Figure 4 Front view of the position of the fatigue test specimen in the embodiment;

[0021] Figure 5 for Figure 4 Top view of the .

[0022] In the figure, the landing gear side support die forging 1, the groove 11, the protrusion 12, the transition rib 13, the notch 14, the blank 2, the rod 21, the expanded head 22, the pre-forging 3, the positioning groove 31, the notch 32, the protruding rib 33, and the positioning plane 34. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0024] A forging method for improving the fatigue performance of an aircraft landing gear side support die forging, wherein the material of the landing gear side support die forging 1 is 300M, the landing gear side support die forging 1 is in an I-shape, and its top and bottom surfaces are isosceles trapezoids that gradually expand from the left end to the right end along its length direction, and a concave groove 11 is provided at the left end of its web, and protrusions 12 are provided on both sides of the right end of the web, and the bottom ends of the two protrusions 12 are connected through transition ribs 13, and a concave notch 14 is provided at the right end of the web, and the notch 14 passes through the right end of the web of the landing gear side support die forging 1 along the length direction; the method comprises the following steps:

[0025] S1, a round bar is first heated to form a blank 2, and the cross section of the blank 2 along the length direction matches the cross section of the final forging;

[0026] S2, the blank 2 is heated in the furnace and forged in position in the fetal membrane to form a pre-forged part 3, such as Figure 3 As shown, the bottom of the pre-forged part 3 is forged with a positioning groove 31 corresponding to the groove 11 of the landing gear side support die forging 1, a notch 32 corresponding to the notch 14, and a protruding rib 33 corresponding to the transition rib 13;

[0027] S3, the pre-forged piece 3 is returned to the furnace for heating, and after heating, the pre-forged piece 3 is installed in the final forging die for final forging to obtain the final forging, and the final forging temperature is ≥720°C.

[0028] The forging method for improving the fatigue performance of the aircraft landing gear side support die forging disclosed in the present invention changes the traditional form of using square bars to form blanks through free forging, and uses round bars to form blanks through upsetting or drawing. Compared with square bars, the metal flow intensity of round bars is relatively weaker, which greatly reduces the risk of reduced fatigue performance.

[0029] The final forging temperature adopted by the present invention is lower than the traditional forging temperature, so that the inclusions are partially diffused during the forging process, the material is more uniform, and the fatigue performance is improved.

[0030] The present invention adopts a forging process of drawing-pre-forging-final forging, and the pre-forging process of this embodiment is different from conventional pre-forging. The pre-forging disclosed in this embodiment is positioning forging in the fetal membrane. The so-called positioning forging refers to designing a suitable fetal membrane according to the characteristics of the final forging, and the blank undergoes local small deformation in the fetal membrane, so that the pre-forging 3 formed by the pre-forging forms an adaptive positioning with the final forging die. That is, in this embodiment, the blank undergoes local small deformation in the fetal membrane to form positioning grooves 31, notches 32 and ribs 33, which serve to position during the subsequent final forging. The local small deformation during the pre-forging process reduces the intensity of metal flow and does not lead to a decrease in fatigue performance. The pre-forging 3 formed by the pre-forging forms an adaptive positioning with the final forging die, which reduces the swinging time, and the final forging has good appearance and uniformity of structure, and the final forging process is stably controlled with uniform quality.

[0031] like Figure 2 As shown, the blank 2 is square along its length and includes a rod 21 and an expanded head 22 at one end of the rod 21. The cross-sections of the rod 21 and the expanded head 22 are both circular. The blank 2 is obtained by drawing the bar after the first heating. The first heating temperature of the bar is 1150-1200℃, the heating time of the cold piece is 0.6min / mm, and the holding time of the hot piece is 30-60min. The cross-sectional size of the blank 2 is 1.2 times the maximum cross-sectional size of the corresponding part of the final forging.

[0032] The pre-forged part 3 is quasi-circular. Quasi-circular includes circular, approximately circular or elliptical. The pre-forged part 3 is forged by the second-fire fetal membrane. After the first fire is completed, the hot blank 2 is returned to the furnace, and the blank 2 after being heated in the furnace undergoes a small local deformation in the fetal membrane to form an adaptive positioning with the final forging. The second-fire heating temperature of the blank 2 is 1150-1200°C, the heating time of the cold part is 0.6min / mm, and the insulation time of the hot part is 30-60min. The pre-forged part 3 is quasi-circular, that is, the process from the blank 2 to the pre-forged part 3 has small deformation, low material flow intensity, and little effect on fatigue performance.

[0033] If the surface between the positioning groove 31 and the notch 32 of the pre-forging 3 is arc-shaped, when it is placed on the final forging die, the contact area with the final forging die is small. In order to further improve the stability and reliability of positioning, a positioning plane 34 extending along the length direction of the pre-forging 3 is formed between the positioning groove 31 and the notch 32 of the pre-forging 3. The positioning plane 34 increases the contact area between the pre-forging 3 and the final forging die, which is more conducive to positioning.

[0034] In order to suppress the metal flow in the length direction and prevent the metal flow in the length direction from being too intense, in this embodiment, the pre-forging 3 is 15-20 mm longer than the final forging.

[0035] The forging heating temperature is 1150-1200℃. Heating at a higher temperature can make the workpiece heat through quickly. After each firing, the heated parts are returned to the furnace, and the hot parts are kept warm for 30-60 minutes. The hot parts are returned to the furnace to reduce the impact of temperature difference changes on fatigue performance.

[0036] Embodiment: The method disclosed in the present invention is used to forge Figure 1 The landing gear side support die forging 1 shown has an outer contour size of 265×330×1170 mm. The forging process is as follows:

[0037] S1. After the φ260 bar is heated for the first time, it is stretched to obtain a suitable billet cross section. The billet cross section is circular, and the billet cross section is 1.2 times the maximum cross section of the corresponding final forging. Figure 2 shown.

[0038] S2. After the first fire is finished, the blank is immediately returned to the furnace for heating, and the positioning forging is carried out in the fetal membrane to prepare the adaptive positioning for the final forging process. Figure 3 shown.

[0039] S3, after the second fire, the hot blank is returned to the furnace for die forging to obtain the final forging. Figure 1 shown.

[0040] The process implementation equipment is: the billet process and the tire membrane are implemented on a 16MN fast forging machine, and the die forging process is implemented on a 200MN hydraulic press. The forging process parameters are: all heating temperatures are 1150-1200℃, the cold piece heating time is 0.6min / mm, the hot piece insulation time is 30-60min, and the forging temperature is 720℃-900℃.

[0041] Comparative example: using traditional method to forge Figure 1 The landing gear side support die forging 1 shown has an outer contour size of 265×330×1170 mm.

[0042] It is known from metal material science that the performance is the worst at the position perpendicular to the parting surface and close to the flash, so a high-direction specimen is taken here for fatigue performance testing, such as Figure 4 and Figure 5 As shown, five points F1, F2, F3, F4 and F5 were taken for measurement, and the fatigue properties of the final forgings forged by the embodiment and the comparative example are shown in the following table:

[0043] F1(week) F2(week) F3(week) F4(week) F5(week) Average Week Comparative Example 409686 89071 98340 127864 190738 183140 Example 3000000 1614037 1440571 3000000 1629267 2136775

[0044] It can be seen from the above table that the fatigue performance of the embodiment is greatly improved, and the average fatigue performance is improved from 183140 weeks of the comparative example to 2136775 weeks.

[0045] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A forging method for improving fatigue performance of a side support die forging of an aircraft landing gear, wherein the material of the side support die forging (1) of the landing gear is 300M, the side support die forging (1) of the landing gear is in an I-shape, and the web gradually widens from the left end to the right end along its length direction, the left end of the web is provided with an inwardly concave groove (11), and the two sides of the right end of the web are provided with protrusions (12) arranged oppositely, the bottom ends of the two protrusions (12) are connected through transition ribs (13), and the right end of the web is provided with an inwardly concave notch (14), and the notch (14) passes through the right end of the web of the side support die forging (1) of the landing gear along the length direction; characterized in that: The following steps are involved: S1, a round bar is first heated to form a blank, and the cross section of the blank (2) along the length direction matches the cross section of the final forging; S2, the blank (2) is returned to the furnace for heating, and local deformation positioning forging is performed in the tire membrane to form a pre-forged part (3); the bottom of the pre-forged part (3) has a positioning groove (31) corresponding to the groove (11) of the landing gear side support die forging (1), a notch (32) corresponding to the notch (14), and a protruding rib (33) corresponding to the transition rib (13); S3, the pre-forged piece (3) is returned to the furnace for heating, and after heating, the pre-forged piece (3) is installed in a final forging die for final forging to obtain a final forging, and the final forging temperature is ≥720°C.

2. The forging method for improving the fatigue performance of the aircraft landing gear side support die forging according to claim 1, characterized in that: The blank (2) is square along its length and includes a rod portion (21) and an expanded head portion (22) at one end of the rod portion (21); the cross sections of the rod portion (21) and the expanded head portion (22) are both circular.

3. The forging method for improving the fatigue performance of the aircraft landing gear side support die forging according to claim 2, characterized in that: The pre-forged piece (3) is quasi-circular.

4. The forging method for improving the fatigue performance of the aircraft landing gear side support die forging according to claim 3, characterized in that: A positioning plane (34) extending along the length direction of the pre-forged piece (3) is formed between the positioning groove (31) and the notch (32) of the pre-forged piece (3).

5. The forging method for improving the fatigue performance of the aircraft landing gear side support die forging according to claim 1, characterized in that: The pre-forged part (3) is 15-20 mm longer than the final forged part.

6. The forging method for improving the fatigue performance of an aircraft landing gear side support die forging according to any one of claims 1 to 5, characterized in that: The forging heating temperature is 1150-1200℃.

7. The forging method for improving the fatigue performance of an aircraft landing gear side support die forging according to any one of claims 1 to 5, characterized in that: After each firing, the heated parts are returned to the furnace for 30-60 minutes of insulation time.

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