Large forged piece preformed blank with flange deep blind hole, forged piece and forming method of large forged piece preformed blank

Abstract

The invention relates to a large-scale flanged deep blind hole forge piece preformed blank, a forge piece and a forming method thereof, belongs to the technical field of forging, and is used for at least solving one of the problems that an existing press cannot meet the forging pressure of integral forming of the large-scale flanged deep blind hole forge piece, and coarse grains and mixed crystals are easily generated in the preparation process of the large-scale flanged deep blind hole forge piece. The prefabricated blank comprises a second expanding section, a third expanding section, a third constant-diameter section, a fourth expanding section and a fourth constant-diameter section which are sequentially connected from bottom to top; the included angle k1 between the outer circular surface of the second diameter expanding section and the center line of the preformed blank and the included angle k2 between the outer circular surface of the third diameter expanding section and the center line of the preformed blank meet the following relation: k1 is less than k2; a second center blind hole is formed in the upper surface of the fourth constant-diameter section and is in a circular truncated cone shape, and the aperture of the upper surface of the second center blind hole is larger than that of the lower surface of the second center blind hole. The large forged piece with the flange and the deep blind hole, prepared through the method, is uniform in crystal grain and small in forming pressure.

Description

Technical Field

[0001] The present invention belongs to the technical field of forging, and particularly relates to a preform for a large flange deep blind hole forging, a forging and a forming method thereof. Background Art

[0002] Since stainless steel or superalloy does not undergo a phase change during hot working and heat treatment, it is difficult to eliminate coarse grains and mixed grains caused by uneven forging during subsequent heat treatment. The deformation uniformity of the forged finished product will affect the uniformity of the grain size of the finished product. Therefore, how to ensure the deformation uniformity of the forging finished product is particularly important for ensuring product quality.

[0003] The manufacture of large flange deep blind hole forgings has a relatively high risk coefficient. The forging has a complex shape, is difficult to form, and the flange end face is prone to cracking. It is difficult to ensure the grain size and deformation uniformity of each part of the forging. At present, the forming methods for forgings with shallow blind holes mainly include punching, drawing, etc. For deep blind hole forgings, there is a method of multi-pass drawing after punching. However, when forging large stainless steel or superalloy deep blind hole flange blind hole forgings, the force required for punching exceeds the limit value of the press, and general presses cannot meet the requirements. Moreover, using the method of multi-pass drawing, not only is there a risk of thickening deformation at the bottom head position, but also multiple non-deformation heating processes will inevitably cause coarse grain size. Therefore, providing a large flange deep blind hole forging and its forming method has become an urgent problem to be solved. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a preform for a large flange deep blind hole forging, a forging and a forming method thereof, so as to solve at least one of the following technical problems: the existing press cannot meet the forging pressure for the overall forming of large flange deep blind hole forgings, and problems such as coarse grain and mixed grain are likely to occur during the preparation process of large flange deep blind hole forgings.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] The present invention provides a preform for a large flange deep blind hole forging, which includes, from bottom to top, a second diameter-expanding section, a third diameter-expanding section, a third constant-diameter section, a fourth diameter-expanding section and a fourth constant-diameter section connected in sequence;

[0007] The included angle k1 between the outer circumferential surface of the second diameter-expanding section and the central line of the preform, and the included angle k2 between the outer circumferential surface of the third diameter-expanding section and the central line of the preform satisfy the following relationship: k1 < k2;

[0008] The upper surface of the fourth constant-diameter section is provided with a second central blind hole, the second central blind hole is frustum-shaped, and the aperture of the upper surface of the second central blind hole is larger than that of the lower surface.

[0009] Further, the included angle α / 2 between the upper side wall of the second central blind hole and the center line of the preform is 2° to 7.5°.

[0010] Further, the included angle k3 between the outer cylindrical surface of the fourth diameter-expanding section and the center line of the preform is greater than 30°.

[0011] Further, a circular chamfer is provided at the connection between the side wall and the bottom wall of the second central blind hole.

[0012] Further, the upper surface of the fourth constant-diameter section slopes downward in a direction gradually away from the center line of the preform.

[0013] Further, the height L4 of the second central blind hole is less than the height L1 of the fourth constant-diameter section.

[0014] The present invention also provides a forming method for a large flange deep blind hole forging. The forming method includes die forging using the preform of the large flange deep blind hole forging described above.

[0015] Further, the large flange deep blind hole forging includes, from bottom to top, a first constant-diameter section, a first diameter-expanding section, and a second constant-diameter section connected in sequence. A first central blind hole is also provided on the flange deep blind hole forging. The first central blind hole penetrates through the second constant-diameter section and the first diameter-expanding section and extends to the bottom of the first constant-diameter section; the outer diameter of the second constant-diameter section is D1, the diameter of the first central blind hole is D2, and the outer diameter of the first constant-diameter section is D3, where D1 > D3 > D2; the height of the first constant-diameter section is H2, the height of the first diameter-expanding section is H3, and the height of the second constant-diameter section is H4.

[0016] Further, the height L2 of the third diameter-expanding section, the height L3 of the second diameter-expanding section, and the height H2 of the first constant-diameter section satisfy the following relationship: H2 < L2 + L3.

[0017] Further, the diameter D4 of the lower surface of the second diameter-expanding section and the outer diameter D3 of the first constant-diameter section satisfy the following relationship: D4 = (0.4 - 0.7)D3.

[0018] The present invention also provides a large flange deep blind hole forging, which is prepared by using the above forming method.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0020] The preform of the large flange deep blind hole forging of the present invention is in the shape of multiple stepped sections. When the preform is placed in the female die, a part of the third diameter-expanded section is placed on the conical inclined surface of the female die, and the fourth constant-diameter section is located above the female die and the outer diameter of the fourth constant-diameter section is greater than the maximum inner diameter of the female die. Instead of the blank being completely placed inside the female die in the traditional design, in this way, a part of the third diameter-expanded section is in close contact with the conical inclined surface of the female die, and the fourth diameter-expanded section is in contact with the upper end of the female die, which can effectively prevent the height of the preform from decreasing, and further prevent the blank from gradually filling the cavity due to the downward movement of the blank metal, thus avoiding the increase in forming force and the shortening of the limit stroke of the punch. The stepped preform design is adopted to compress the deformation amount in the subsequent drawing process, enabling single-fire drawing, and further ensuring the technical advantages of single-fire drawing forming.

[0021] In the forming method of the present invention, by precisely controlling the shape and size of the preform, the flow splitting during the forging process can be achieved. Combining with the control of the process steps of the present invention, the step-by-step gradient deformation of the first constant-diameter section and the second constant-diameter section can be realized, so that the strain of the second constant-diameter section is 0.4 - 0.6, and the strain of the first constant-diameter section and the bottom head position is 0.5 - 1; furthermore, the deformation amount at each position is ensured to be uniform, so that the grain size distribution is uniform and the grains are fine.

[0022] In the forming method of the present invention, the required forming force is relatively small, for example, below 14000T, which does not exceed the limit of the press and is safe to operate.

[0023] The grains of the large flange deep blind hole forging prepared by the method of the present invention are uniform, the grain size is 3 - 4 levels, and the maximum grain size difference between different parts is below 1 level. For example, the maximum grain size difference between different parts is 0.5 level. During the preparation process of the present invention, there are no defects such as cracks and concave cores.

[0024] Other features and advantages of the present invention will be described in the subsequent specification, and some of them will become obvious from the specification or be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in the written specification and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings are only used to illustrate the purpose of the specific invention and are not considered as a limitation to the present invention. Throughout the drawings, the same reference signs represent the same components.

[0026] Figure 1 It is a schematic structural diagram of the large flange deep blind hole forging of the present invention;

[0027] Figure 2 It is a schematic structural diagram of the preform of the large flange deep blind hole forging of the present invention;

[0028] Figure 3Assembly schematic diagram of the forming process of the large flange deep blind hole forging of the present invention;

[0029] Figure 4 Schematic diagram of the first lower die of the present invention;

[0030] Figure 5 Schematic diagram of the second lower die of the present invention;

[0031] Figure 6 Schematic diagram of the punch rod of the present invention;

[0032] Figure 7 Schematic diagram of the punch retaining ring of the present invention;

[0033] Figure 8 Schematic diagram of the bottom backing plate of the present invention;

[0034] Figure 9 Schematic diagram of the mandrel of the present invention;

[0035] Figure 10 Schematic diagram of the preform die forging process of the present invention;

[0036] Figure 11 Schematic diagram after the preform die forging of the present invention;

[0037] Figure 12 Schematic diagram of drawing out of the present invention;

[0038] Figure 13 Schematic diagram of the preparation process of Comparative Example 1;

[0039] Figure 14 Schematic diagram of the preparation process of Comparative Example 2.

[0040] Reference numerals:

[0041] 1 - First constant diameter section, 2 - First expanded diameter section, 3 - Second constant diameter section, 4 - First central blind hole, 5 - Second expanded diameter section, 6 - Third expanded diameter section, 7 - Third constant diameter section, 8 - Fourth expanded diameter section, 9 - Fourth constant diameter section, 10 - Second central blind hole, 11 - Platform, 12 - Die, 1201 - First lower die, 1202 - Second lower die, 1203 - Bottom backing plate, 13 - Punch, 1301 - Punch rod, 1302 - Punch retaining ring, 1303 - Soft pin, 14 - Mandrel, 1401 - Clamping section, 1402 - Working section, 1403 - Connecting section, 15 - Mandrel retaining ring. Detailed description of the invention

[0042] The following will specifically describe the preferred invention of the present invention in conjunction with the accompanying drawings, where the accompanying drawings form a part of the present invention and are used together with the invention of the present invention to explain the principle of the present invention.

[0043] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly specified and defined, the term "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be directly connected or indirectly connected through an intermediate medium.

[0044] The terms "top", "bottom", "above", "under", and "on" used in the description throughout the text are relative positions with respect to the components of the device, such as the relative positions of the top and bottom substrates inside the device. It can be understood that the device is multifunctional and is independent of its orientation in space.

[0045] The normal working surface of the present invention can be a plane or a curved surface, which can be inclined or horizontal. For the convenience of description, the embodiments of the present invention are placed on a horizontal plane and used on the horizontal plane, and "high and low" and "up and down" are defined accordingly.

[0046] The present invention provides a large flange deep blind hole forging, as Figure 1 shown. The large flange deep blind hole forging includes, from bottom to top, a first constant diameter section 1, a first diameter expansion section 2, and a second constant diameter section 3 that are connected in sequence. A first central blind hole 4 is also provided on the flange deep blind hole forging. The first central blind hole 4 penetrates through the second constant diameter section 3 and the first diameter expansion section 2 and extends towards the bottom of the first constant diameter section 1. The outer diameter of the second constant diameter section 3 is D1, the diameter of the first central blind hole 4 is D2, and the outer diameter of the first constant diameter section 1 is D3, where D1 > D3 > D2. The height of the first constant diameter section 1 is H2, the height of the first diameter expansion section 2 is H3, the height of the second constant diameter section 3 is H4, the overall height of the forging is H, and the distance from the lowest end of the bottom of the first central blind hole 4 to the bottom of the forging along the central axis is H1. The overall of the first diameter expansion section 2 and the second constant diameter section 3 can be referred to as the flange.

[0047] Specifically, the material of the large flange deep blind hole forging of the present invention is stainless steel or superalloy, with a large deformation resistance and difficult to control the grain size. For example, the material of the large flange deep blind hole forging of the present invention is 316 stainless steel.

[0048] Specifically, the above-mentioned H is more than 2000 mm. For example, H is 1700 - 4600 mm, H1 is 100 - 500 mm, H2 is 600 - 1800 mm, H3 is 100 - 400 mm, and H4 is 1000 - 2400 mm; D3 is more than 1000 mm. For example, D3 is 1000 - 1500 mm, D2 is 800 - 1200 mm, and D1 is more than 1400 mm. For example, D1 is 1400 - 2400 mm.

[0049] Specifically, the ratio h / D2 of the depth h of the above-mentioned first central blind hole 4 to the diameter D2 of the first central blind hole 4 is 1.5 or more, for example, 1.5 to 3, such as 2, 2.2, 2.4, 2.6, 2.8.

[0050] When the inventor prepares the above-mentioned large flange deep blind hole forging, it is difficult to ensure the grain size of the forging and the deformation uniformity of each part; and because the blind hole is relatively deep, the force required for punching is relatively large, and the punching force exceeds the limit value of the press, and general presses cannot meet the requirements; and because the blind hole is relatively deep, it is easy to hold the die after punching, resulting in difficulty in removing the punch.

[0051] The present invention provides a preform for a large flange deep blind hole forging (which can be simply referred to as a preform), as Figure 2 shown, the preform includes a second diameter-expanded section 5, a third diameter-expanded section 6, a third constant-diameter section 7, a fourth diameter-expanded section 8, and a fourth constant-diameter section 9 connected in sequence from bottom to top; the included angle k1 between the outer circumferential surface of the second diameter-expanded section 5 and the central axis of the preform, and the included angle k2 between the outer circumferential surface of the third diameter-expanded section 6 and the central axis of the preform satisfy the following relationship: k1 < k2; the upper surface of the fourth constant-diameter section 9 is provided with a second central blind hole 10, the second central blind hole 10 is frustum-shaped, and the aperture of the upper surface of the second central blind hole 10 is larger than the aperture of the lower surface. Specifically, considering that the included angle α / 2 between the upper end side wall of the second central blind hole 10 and the central axis of the preform is too large, a large slope will be formed on the preform after punching, and there will be a large gap between the inner hole of the forging and the mandrel during mandrel drawing, affecting the deformation amount of the flange part; if α / 2 is too small, the inner hole blank will wrap the punch rod during the punching process, resulting in difficulty in demolding. Therefore, α is controlled to be 4° to 15°, such as 6°, 8°, 10°, 12°, 14°; that is, α / 2 is 2° to 7.5°.

[0052] Specifically, in order to prevent the height of the blank from decreasing during die forging, the included angle k3 between the outer circumferential surface of the fourth diameter-expanded section 8 and the central axis of the preform is greater than 30°, for example, k3 is 33° to 80°; such as 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°.

[0053] Specifically, the total height H' of the preform is less than the height H of the finished product of the large flange deep blind hole forging.

[0054] Compared with the prior art, the preform of the large flange deep blind hole forging of the present invention is in the shape of multiple stepped sections. When the preform is placed in the female die, a part of the third diameter-expanding section is placed on the tapered inclined surface of the female die, and the fourth constant-diameter section is located above the female die and the outer diameter of the fourth constant-diameter section is greater than the maximum inner diameter of the female die, rather than the blank being completely placed inside the female die in the traditional design. In this way, during punching, a part of the third diameter-expanding section is in close contact with the tapered inclined surface of the female die, and the fourth diameter-expanding section gradually contacts the upper end surface of the female die, which can effectively prevent the height of the preform from decreasing, and further prevent the blank from gradually filling the cavity due to the downward movement of the blank metal, thereby avoiding the increase in forming force and the shortening of the limit stroke of the punch. The stepped preform design is adopted to compress the deformation amount in the subsequent drawing process, enabling single-fire drawing and thus ensuring the technical advantages of single-fire drawing forming.

[0055] Specifically, there is a circular chamfer at the connection between the side wall and the bottom wall of the above-mentioned second central blind hole 10, which can reduce the tensile stress at the connection part of the side wall and the bottom surface and prevent cracks from occurring.

[0056] Specifically, there is a circular chamfer at the connection between the side wall of the above-mentioned second central blind hole 10 and the upper surface of the fourth constant-diameter section 9, which can reduce stress concentration.

[0057] Specifically, the upper surface of the above-mentioned fourth constant-diameter section 9 slopes downward along the direction gradually away from the center line of the preform. Such a setting is because the height of the inner hole part will decrease after die forging and punching. This setting will make the end surface height tend to be consistent after punching, and there will be no phenomenon of concave center. Considering that if the inclination angle β is too large, the inner hole of the end surface will be high and the outer circle will be low; if β is too small, it will not achieve the due effect, the inner hole will be low and the outer circle will be high. Moreover, once the inner hole is low and the outer circle is high occurs, during the subsequent drawing process, the inner hole contacts the mandrel, and the inner hole grows slowly in the length direction while the outer circle grows fast, and the concave center situation will be aggravated. Therefore, β is controlled to be 2° to 8°, such as 3°, 4°, 5°, 6°, 7°.

[0058] Specifically, the height L2 of the above-mentioned third diameter-expanding section 6, the height L3 of the second diameter-expanding section 5, and the height H2 of the first constant-diameter section 1 of the forging satisfy the following relationship: H2 < L2 + L3.

[0059] Specifically, the diameter D4 of the lower surface of the above-mentioned second diameter-expanding section 5 and the outer diameter D3 of the first constant-diameter section 1 satisfy the following relationship: D4 = (0.4 - 0.7)D3.

[0060] Specifically, the diameter D2' of the lower surface of the above-mentioned second central blind hole 10 and the diameter D2 of the first central blind hole 4 satisfy the following relationship: D2' = D2.

[0061] Specifically, the diameter D0 of the upper surface of the above-mentioned second diameter-expanding section 5 and the diameter D2' of the lower surface of the second central blind hole 10 satisfy the following relationship: D0 > D2'.

[0062] Specifically, the diameter D1' of the above-mentioned third constant-diameter section 7 and the outer diameter D1 of the second constant-diameter section 3 satisfy the following relationship: D1' = D1.

[0063] Specifically, the diameter D1'' of the above-mentioned fourth constant-diameter section 9, the outer diameter D1 of the second constant-diameter section 3, and the diameter D2 of the first central blind hole 4 satisfy the following relationship:

[0064]

[0065] Specifically, considering that the angle γ / 2 between the lower side wall of the third diameter-expanding section 6 and the center line of the preform is too large, the blank will be stuck at this layer, and it is easy to cause the metal below this inclined plane to crack during stamping; if the angle is too small, the blank will flow downward. After filling the cavity, the stamping force increases and the stroke decreases. Therefore, γ is controlled to be 80° - 120°.

[0066] Specifically, the height L4 of the above-mentioned second central blind hole 10 and the height L1 of the fourth constant-diameter section 9 satisfy the following relationship: L4 < L1. Specifically, the height L1 of the above-mentioned fourth constant-diameter section 9 is controlled between 600 - 1000 mm, and L1 = L4 + (50 - 200) mm. L4 is smaller than L1 to ensure the uniformity of deformation. If L4 is deeper than L1, after stamping, the blank between L4 and L1 has no deformation amount and will not be covered during mandrel drawing. Therefore, L4 < L1 is controlled.

[0067] Specifically, the present invention also provides a forming tooling for a large flange deep blind hole forging, as Figure 3 shown. The forming tooling includes a platform 11 and a female die 12 above the platform 11; the female die 12 is hollow, and the female die 12 includes a first lower die 1201 and a second lower die 1202. The inner side of the upper end surface of the second lower die 1202 is provided with a tapered inclined plane, and the angle θ between the tapered inclined plane and the center line of the female die 12 is 5° - 45°, such as 10°, 15°, 20°, 25°, 30°, 35°, 40°; the bottom end surface of the first lower die 1201 is provided with a positioning groove, and the upper end surface of the second lower die 1202 is clamped into the positioning groove; during use, the first lower die 1201 cooperates with the third constant-diameter section 7, and the tapered inclined plane of the second lower die 1202 can cooperate with the third diameter-expanding section 6.

[0068] Specifically, the platform 11 and the female die 12 are of a split type, which can avoid stress concentration at the bottom, and the die life is longer; and the split type has a relatively simple shape, is convenient for manufacturing and processing, and saves costs.

[0069] Specifically, the female die 12 further includes a bottom backing plate 1203. The bottom backing plate 1203 is placed inside the second lower die 1202. The bottom backing plate 1203 is a hollow ring. During die forging, the bottom of the second diameter expansion section 5 is placed inside the inner hole of the bottom backing plate 1203, and the bottom backing plate 1203 serves to prevent the blank from cracking during die forging.

[0070] Considering that an excessive thickness H10 of the bottom backing plate 1203 wastes the weight of the forgings, while a too small thickness fails to prevent cracking; therefore, the thickness H10 of the bottom backing plate 1203 is controlled to be 80 - 200 mm, such as 100 mm, 120 mm, 140 mm, 160 mm, 180 mm.

[0071] Specifically, the above - mentioned forming tooling further includes a punch 13. The punch 13 includes a punch rod 1301 and a punch retaining ring 1302. A boss is provided at the lower end of the punch rod 1301, and the punch retaining ring 1302 is sleeved on the boss. The punch rod 1301 and the punch retaining ring 1302 are connected by a soft pin 1303; a chamfer is provided on the outer side of the lower end of the punch retaining ring 1302; the outer diameter D9 of the punch retaining ring 1302 is greater than the outer diameter D8 of the punch rod 1301; for example, the difference between the outer diameter of the punch retaining ring 1302 and the outer diameter of the punch rod 1301 is 40 - 100 mm. The height H9 of the punch retaining ring 1302 is 150 - 250 mm.

[0072] Specifically, the punch connecting frame is connected to the movable crossbeam of the press above the punch connecting frame. The punch rod 1301 is connected to the punch connecting frame by a long pin, thereby connecting the punch rod 1301 to the movable crossbeam of the press.

[0073] After die forging, when the movable crossbeam of the press drives the punch rod 1301 to move upward, the soft pin between the punch rod 1301 and the punch retaining ring 1302 will be sheared due to the gravity of the blank, and the punch retaining ring 1302 and the broken soft pin will remain in the inner hole of the forging. In this way, the demolding is simple and fast.

[0074] Specifically, in order to ensure that the soft pin can bear the weight of the punch but cannot bear the weight of the blank, the material of the soft pin is Q235 steel or 45 steel, and the diameter is 22 - 25 mm.

[0075] Specifically, the above - mentioned forming tooling further includes a mandrel 14 and a mandrel retaining ring 15, as Figure 12 shown. The mandrel 14 includes a clamping section 1401 and a working section 1402. The working section 1402 acts on the central blind hole of the blank. There is a taper on the side of the working section 1402, and the draft taper is 4°, which is convenient for demolding; the clamping section 1401 and the working section 1402 are connected by a connecting part 1403 in the middle. The diameter of the working section 1402 is smaller than the diameter of the connecting part 1403, and the diameter of the clamping section 1401 is smaller than the diameter of the working section 1402.

[0076] Specifically, the diameter of the mandrel retaining ring 15 is greater than the outer diameter of the second constant-diameter section 3 of the forging. During upsetting, the mandrel retaining ring 15 is used and sleeved at the connection between the working section 1402 and the connecting portion 1403. The mandrel retaining ring 15 can prevent end-face cracks and concave centers of the forging and is beneficial for mandrel demolding. Mechanism for preventing cracks: When there is no mandrel retaining ring 15 pressing against the forging, the end face of the forging contacts the air, cools rapidly, and the end-face bulging generates tensile stress, making it prone to generate blossoming cracks; when there is a mandrel retaining ring 15 pressing against the end face, the end-face bulging cannot form, the end face tends to be flat, and the generation of tensile stress is reduced. Mechanism for preventing concave centers: During the process of mandrel upsetting, the inner hole of the blank contacts the mandrel, the temperature drops rapidly, and the friction is large. Often, the material moves at the end face while not moving at the core, resulting in a concave center. Therefore, when there is a mandrel retaining ring 15, the end face is flatter, eliminating the concave center. Demolding: During the process of mandrel upsetting, due to the gradual decrease in the temperature of the blank, the effect of thermal expansion and contraction makes the blank easily wrap around the mandrel and difficult to demold. Therefore, when the end face of the blank presses against the mandrel retaining ring 15 for upsetting, the length at the mandrel retaining ring 15 increases, and there is relative movement between the blank part of the inner hole of the forging and the mandrel, and they will not be locked on the mandrel. Demolding is carried out based on this principle.

[0077] Specifically, Figure 4 is a schematic diagram of the first lower die, Figure 5 is a schematic diagram of the second lower die, Figure 6 is a schematic diagram of the punch rod, Figure 7 is a schematic diagram of the punch retaining ring, Figure 8 is a schematic diagram of the bottom backing plate, Figure 9 is a schematic diagram of the mandrel. The inner wall of the upper surface of the first lower die 1201 is provided with a chamfer; the inner diameter of the first lower die 1201 is D6, the inner diameter of the positioning groove at the bottom of the first lower die 1201 is D5, and the height of the first lower die 1201 is H7; the inner diameter of the upper surface of the second lower die 1202 is D7, the inner diameter of the lower surface of the second lower die 1202 is D3', the outer diameter of the second lower die 1202 is D5', and the height of the second lower die 1202 is H6; the outer diameter of the punch rod 1301 is D8, the height of the boss of the punch rod 1301 is H8, and the diameter of the boss is D12; the height of the punch retaining ring 1302 is H9, the inner diameter of the punch retaining ring 1302 is D13, and the outer diameter of the punch retaining ring 1302 is D9; the outer diameter of the bottom backing plate 1203 is D10; the maximum diameter of the working section 1402 of the mandrel is D11, and the length of the working section 1402 of the mandrel is H4'; the units of the above dimensions are all mm, and the above dimensions meet the following relationships:

[0078] D6 = D7 = D1;

[0079] D3' = D3;

[0080] D5 = D5' + (3 - 20) mm;

[0081] H6 = H2 + (100 - 400) mm;

[0082] D8 = D9 - (40 - 100) mm;

[0083] D9 = D2;

[0084] D10 = D3' - (20 - 50) mm;

[0085] D11 = D2;

[0086] D12 = D13 - (1 - 5) mm;

[0087] H8 = H9;

[0088] H10 = 80 - 200 mm;

[0089] H4' < H - H1 - H9.

[0090] The present invention provides a forming method for the above-mentioned large-sized flanged deep blind hole forging, and the forming method includes die forging using the preform of the above-mentioned large-sized flanged deep blind hole forging.

[0091] Specifically, the above-mentioned forming method includes the following specific steps:

[0092] S1. Make an ingot into a preform of a large-sized flanged deep blind hole forging;

[0093] S2. As shown in A of, place the preform in the female die 12, the third constant diameter section 7 of the preform is matched with the first lower die 1201 of the female die, and the conical inclined surface of the second lower die 1202 of the female die is matched with the third diameter-expanded section 6; Figure 10 Shown in A, place the preform in the female die 12, the third constant diameter section 7 of the preform is mated with the first lower die 1201 of the female die, and the conical inclined surface of the second lower die 1202 of the female die is mated with the third diameter-expanded section 6;

[0094] S3. The movable crossbeam of the press presses down to drive the punch to move downward, and start die forging; as shown in B of, when the stroke of the punch reaches the preset value, stop loading; Figure 10 Shown in B, when the stroke of the punch reaches the preset value, stop loading;

[0095] S4. As shown in, after die forging, the punch retaining ring 1302 is locked by the inner hole blank, lift the movable crossbeam of the press, and the movable crossbeam of the press drives the punch rod 1301 to lift. Since the soft pin cannot drive the weight of the blank, it is sheared and cut off, so that the punch retaining ring 1302 remains in the inner hole of the forging; Figure 11 As shown in, after die forging, the punch retaining ring 1302 is locked by the inner hole blank, lift the movable crossbeam of the press, and the movable crossbeam of the press drives the punch rod 1301 to lift. Since the soft pin cannot drive the weight of the blank, it is sheared and cut off, so that the punch retaining ring 1302 remains in the inner hole of the forging;

[0096] S5. Disconnect the forged blank after die forging from the female die 12, return the forged blank to the furnace for supplementary heating, and perform mandrel drawing after supplementary heating.

[0097] Specifically, in the above-mentioned S2, the length between the upper end surface of the third constant diameter section 7 of the preform and the lower end surface of the second diameter-expanded section 5 is greater than the total assembly height of the first lower die 1201 and the second lower die 1202;

[0098] Specifically, in the above S5, the mandrel 14 is inserted into the central blind hole of the forging blank, and the mandrel retaining ring 15 is abutted between the connecting portion 1403 and the forging blank, and then upsetting is performed once to obtain a large flange deep blind hole forging.

[0099] Specifically, in the above S5, when upsetting the mandrel, 100 - 200 mm of the remaining blank end is not pressed to prevent the generation of end cracks.

[0100] Compared with the prior art, the preform of the large flange deep blind hole forging of the present invention is in a multi - step shape. When the preform is placed in the female die, a part of the third diameter - expanding section is placed on the tapered inclined surface of the female die, and the fourth constant - diameter section is located above the female die and the outer diameter of the fourth constant - diameter section is greater than the maximum inner diameter of the female die, rather than the preform being completely inside the female die in the traditional design. In this way, when punching, a part of the third diameter - expanding section is in close contact with the tapered inclined surface of the female die, and the fourth diameter - expanding section gradually contacts the upper end surface of the female die, which can effectively prevent the reduction of the height of the preform blank, and further prevent the blank from gradually filling the cavity due to the downward movement of the blank metal, thus avoiding the increase of the forming force and the shortening of the limit stroke of the punch. The stepped pre - forming design compresses the deformation amount in the subsequent upsetting process, enabling upsetting in a single heat treatment, and further ensuring the technical advantages of single - heat - treatment upsetting forming.

[0101] The female die of the forming tooling of the present invention includes a first lower die and a second lower die. By controlling the shapes of the first lower die and the second lower die, flow - splitting during the forging process can be achieved; and the female die also includes a bottom backing plate, which can prevent the blank from cracking during die forging.

[0102] The punch of the forming tooling of the present invention includes a punch rod and a punch retaining ring. The punch rod and the punch retaining ring are connected by a soft pin. After die forging, when the movable crossbeam of the press drives the punch rod to move upward, the soft pin between the punch rod and the punch retaining ring will be sheared due to the gravity of the blank, and the punch retaining ring and the broken soft pin remain in the inner hole of the forging. In this way, the demoulding is simple and fast.

[0103] In the forming method of the present invention, by precisely controlling the shape and size of the preform and combining with the control of the forming tooling, for example, the female die of the forming tooling includes a first lower die and a second lower die, and by controlling the shapes of the first lower die and the second lower die, flow - splitting during the forging process can be achieved. Combining with the control of the process steps of the present invention, gradient deformation in multiple heat treatments of the first constant - diameter section and the second constant - diameter section can be realized, so that the strain of the second constant - diameter section is 0.4 - 0.6, and the strain of the first constant - diameter section and the bottom head is 0.5 - 1; thus ensuring uniform deformation amount at each position, making the grain size distribution uniform and the grains fine.

[0104] The grains of the large flange deep blind hole forging prepared by the method of the present invention are uniform, the grain size is 3-4 levels, the maximum grain size difference at different parts is less than 1 level, for example, the maximum grain size difference at different parts is 0.5 level. During the preparation process of the present invention, there are no defects such as cracks and concave centers.

[0105] Example 1

[0106] This example provides a large flange deep blind hole forging, as Figure 1 shown. The large flange deep blind hole forging includes a first constant diameter section 1, a first diameter expansion section 2, and a second constant diameter section 3 connected in sequence from bottom to top. A first central blind hole 4 is also provided on the flange deep blind hole forging. The first central blind hole 4 penetrates through the second constant diameter section 3 and the first diameter expansion section 2 and extends to the bottom of the first constant diameter section 1; the outer diameter of the second constant diameter section 3 is D1, the diameter of the first central blind hole 4 is D2, the outer diameter of the first constant diameter section 1 is D3, D1 = 1650 mm, D3 = 1310 mm, D2 = 900 mm; the height of the first constant diameter section 1 is H2, the height of the first diameter expansion section 2 is H3, the height of the second constant diameter section 3 is H4, the overall height of the forging is H, and the distance from the lowest end of the bottom of the first central blind hole 4 to the bottom of the forging along the central axis is H1. The overall of the first diameter expansion section 2 and the second constant diameter section 3 can be called a flange. H1 = 200 mm, H2 = 1135 mm, H3 = 180 mm, H4 = 1305 mm, H = 2620 mm. The depth h of the first central blind hole 4 is 2420 mm.

[0107] The material of the large flange deep blind hole forging is 316 stainless steel.

[0108] Example 2

[0109] This example provides a preform of a large flange deep blind hole forging (which can be simply referred to as a preform), as Figure 2 shown. The preform includes a second diameter expansion section 5, a third diameter expansion section 6, a third constant diameter section 7, a fourth diameter expansion section 8, and a fourth constant diameter section 9 connected in sequence from bottom to top. The angles k1, k2, k3 between the outer circular surfaces of the second diameter expansion section 5, the third diameter expansion section 6, and the fourth diameter expansion section 8 and the central axis of the preform are 13.5°, 45°, and 55° respectively; a second central blind hole 10 is provided on the upper surface of the fourth constant diameter section 9. The second central blind hole 10 is frustum-shaped, and the aperture of the upper surface of the second central blind hole 10 is larger than that of the lower surface, α is 6°; there is a circular chamfer at the connection between the side wall and the bottom wall of the second central blind hole 10, and there is a circular chamfer at the connection between the side wall of the second central blind hole 10 and the upper surface of the fourth constant diameter section 9. The upper surface of the fourth constant diameter section 9 slopes downward along the direction gradually away from the central axis of the preform, β is 2°.

[0110] Specifically, the height L2 of the third diameter-expanded section 6, the height L3 of the second diameter-expanded section 5, the height L1 of the fourth constant-diameter section 9, the diameter D0 of the upper surface of the second diameter-expanded section 5, the height L4 of the second central blind hole 10, the diameter D4 of the lower surface of the second diameter-expanded section 5, the diameter D2' of the lower surface of the second central blind hole 10, the diameter D1' of the third constant-diameter section 7, the diameter D1'' of the fourth constant-diameter section 9, γ, and the total height H' of the preform are respectively: L2 = 280 mm, L3 = 1100 mm, L1 = 800 mm, D0 = 1148 mm, L4 = 750 mm, D4 = 640 mm, D2' = 900 mm, D1' = 1650 mm, D1'' = 1920 mm, γ = 90°, and H' = 2520 mm.

[0111] Embodiment 3

[0112] This embodiment provides a forming tooling for a large-sized flange deep blind hole forging, as Figure 3 shown. The forming tooling includes a platform 11 and a female die 12 above the platform 11; the female die 12 is hollow and includes a first lower die 1201 and a second lower die 1202. A tapered inclined surface is provided on the inner side of the upper end surface of the second lower die 1202, and the included angle θ between the tapered inclined surface and the center line of the female die is 10°. A positioning groove is provided on the bottom end surface of the first lower die 1201, and the upper end surface of the second lower die 1202 is clamped into the positioning groove; during use, the first lower die 1201 cooperates with the third constant-diameter section 7, and the tapered inclined surface of the second lower die 1202 can cooperate with the third diameter-expanded section 6.

[0113] Specifically, the platform 11 and the female die 12 are of a split type.

[0114] Specifically, the female die 12 further includes a bottom backing plate 1203. The bottom backing plate 1203 is placed inside the second lower die 1202. The bottom backing plate 1203 is a hollow ring. During die forging, the bottom of the second diameter-expanded section 5 is placed inside the inner hole of the bottom backing plate 1203. The thickness H10 of the bottom backing plate 1203 is 100 mm.

[0115] Specifically, the above-mentioned forming tooling further includes a punch 13. The punch 13 includes a punch rod 1301 and a punch clamping ring 1302. A boss is provided at the lower end of the punch rod 1301, and the punch clamping ring 1302 is sleeved on the boss. The punch rod 1301 and the punch clamping ring 1302 are connected by a soft pin 1303; a chamfer is provided on the outer side of the lower end of the punch clamping ring 1302; the outer diameter of the punch clamping ring 1302 is larger than the outer diameter of the punch rod 1301.

[0116] Specifically, the punch connecting frame is connected to the movable crossbeam of the press above the punch connecting frame, and the punch rod 1301 is connected to the punch connecting frame by a long pin.

[0117] After die forging is completed, when the moving crossbeam of the press drives the punch rod 1301 to move upward, the soft pin between the punch rod 1301 and the punch retaining ring 1302 will be sheared due to the gravity of the blank, and the punch retaining ring 1302 and the broken soft pin will remain in the inner hole of the forging.

[0118] Specifically, the material of the soft pin is 45 steel, and the diameter is 25 mm.

[0119] Specifically, the above-mentioned forming tooling further includes a mandrel 14 and a mandrel retaining ring 15. The mandrel 14 includes a clamping section 1401 and a working section 1402. The working section 1402 acts on the central blind hole of the blank. The side surface of the working section 1402 has a taper, and the draft angle is 4°; the clamping section 1401 and the working section 1402 are connected by a connecting part 1403 in the middle. The diameter of the working section 1402 is smaller than that of the connecting part 1403, and the diameter of the clamping section 1401 is smaller than that of the working section 1402.

[0120] Specifically, the diameter of the mandrel retaining ring 15 is larger than the outer diameter of the second constant diameter section 3 of the forging. During stretching, the mandrel retaining ring 15 is used and sleeved on the connection part between the working section 1402 and the connecting part 1403 of the mandrel. The mandrel retaining ring 15 can prevent end face cracks and concavity of the forging and is beneficial to mandrel demolding.

[0121] Specifically, Figure 4 is a schematic diagram of the first lower die, Figure 5 is a schematic diagram of the second lower die, Figure 6 is a schematic diagram of the punch rod, Figure 7 is a schematic diagram of the punch retaining ring, Figure 8 is a schematic diagram of the bottom backing plate, Figure 9 is a schematic diagram of the mandrel. The inner wall of the upper surface of the first lower die 1201 is provided with a chamfer; the inner diameter D6 of the first lower die 1201 is 1650 mm, the inner diameter D5 of the positioning groove at the bottom of the first lower die 1201 is 1955 mm, and the height H7 of the first lower die 1201 is 740 mm; the inner diameter D7 of the upper surface of the second lower die 1202 is 1650 mm, the inner diameter D3' of the lower surface of the second lower die 1202 is 1310 mm, the outer diameter D5' of the outer ring of the second lower die 1202 is 1950 mm, and the height H6 of the second lower die 1202 is 1450 mm; the outer diameter D8 of the punch rod 1301 is 840 mm, the height H8 of the boss of the punch rod 1301 is 220 mm, and the diameter D12 of the boss is 640 mm; the height H9 of the punch retaining ring 1302 is 220 mm, the inner diameter D13 of the punch retaining ring 1302 is 645 mm, and the outer diameter D9 of the punch retaining ring 1302 is 900 mm; the outer diameter D10 of the bottom backing plate 1203 is 1290 mm; the maximum diameter D11 of the working section 1402 of the mandrel is 900 mm, and the length H4' of the working section 1402 of the mandrel is 1900 mm.

[0122] Example 4

[0123] This example provides a forming method for a large flange deep blind hole forging of Example 1, using the preform of Example 2 and the forming tooling of Example 3.

[0124] The specific steps of the forming method for the large flange deep blind hole forging in this example are as follows:

[0125] S1. Make an ingot into a preform of a large flange deep blind hole forging;

[0126] S2. As shown in A in Figure 10 , place the preform in the female die 12. The third constant diameter section 7 of the preform is matched with the first lower die 1201 of the female die, and the tapered inclined surface of the second lower die 1202 of the female die is matched with the third diameter-expanded section 6;

[0127] S3. The moving crossbeam of the press presses down to drive the punch to move downward, and start die forging; as shown in B in Figure 10 , when the stroke of the punch reaches the preset value, stop loading;

[0128] S4. As shown in Figure 11 , after die forging, the punch holding ring 1302 is locked by the inner hole blank. Lift the moving crossbeam of the press, and the moving crossbeam of the press drives the punch rod 1301 to lift. Since the soft pin cannot drive the weight of the blank, it is sheared and cut off, so that the punch holding ring 1302 remains in the inner hole of the forging;

[0129] S5. Disconnect the forged blank after die forging from the female die 12, return the forged blank to the furnace for supplementary heating, and perform mandrel drawing after supplementary heating.

[0130] The grains of the forging obtained in this example are uniform, the grain size is 3-3.5 levels, and the maximum grain size difference in different parts is 0.5 levels. During the preparation process of this example, no defects such as cracks and concave cores appear.

[0131] At the end of forming, the forming force is the largest, reaching 14000T, and the maximum load of the forming press is 15000T, which does not exceed the limit of the press, reducing the forming force by 8000T compared with the existing initial traditional forming method of 22000T.

[0132] During the research process, the inventor conducted a large number of experimental studies, and now some solutions with poor performance are used as comparative examples.

[0133] Comparative Example 1

[0134] This comparative example provides a forming method for a large flange deep blind hole forging, which is used to prepare a forging with the shape of Example 1.

[0135] The method of this comparative example uses the traditional method, such as Figure 13As shown, the blank is directly punched and formed. However, this forming method requires a relatively large forming force, about 22000T, exceeding the press limit. Within the press limit forming force range, the punch stroke is short, leaving a large machining allowance at the bottom of the inner hole.

[0136] Comparative Example 2

[0137] This comparative example provides a forming method for a large flange deep blind hole forging, used to prepare a forging with the shape of Example 1.

[0138] The method of this comparative example is roughly the same as that of Example 4, and the difference lies in:

[0139] Ordinary preforms are used (as Figure 14 shown, different from the preform shape of the present invention) for forming. While the forming force is large, the mandrel drawing requires a relatively long length and it is difficult to form in one heat. In this way, there is a situation of multi-heat non-forging ratio heating at the bottom, and there is a phenomenon of coarse crystal and mixed crystal at the bottom.

[0140] Comparative Example 3

[0141] This comparative example provides a forming method for a large flange deep blind hole forging, used to prepare a forging with the shape of Example 1.

[0142] The method of this comparative example is roughly the same as that of Example 4, and the difference lies in:

[0143] If γ = 140°, it will cause too large tensile stress in the first constant diameter section, resulting in the phenomenon of tensile cracking.

[0144] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A large-scale forging preform with flange and deep blind hole, characterized in that: The preform comprises, from bottom to top, a second diameter expansion section (5), a third diameter expansion section (6), a third constant diameter section (7), a fourth diameter expansion section (8) and a fourth constant diameter section (9) which are connected in sequence; The angle k1 between the outer cylindrical surface of the second diameter expansion section (5) and the center line of the preform and the angle k2 between the outer cylindrical surface of the third diameter expansion section (6) and the center line of the preform meet the following relationship: k1<k2; A second central blind hole (10) is provided on the upper surface of the fourth constant diameter section (9); the second central blind hole (10) is truncated cone-shaped; the aperture of the upper surface of the second central blind hole (10) is larger than the aperture of the lower surface.

2. The large-scale forging preform with flange and deep blind hole according to claim 1 is characterized in that: The included angle α / 2 between the upper end side wall of the second central blind hole (10) and the center line of the preform is 2° to 7.5°.

3. The large-scale forging preform with flange and deep blind hole according to claim 1 is characterized in that: The included angle k3 between the outer cylindrical surface of the fourth diameter expansion section (8) and the center line of the preform is greater than 30°.

4. The large-scale forging preform with flange and deep blind hole according to claim 1 is characterized in that: A circular chamfer is formed at the connection between the side wall of the second central blind hole (10) and the bottom wall of the second central blind hole (10).

5. The large forging preform with flange and deep blind hole according to any one of claims 1 to 4, characterized in that: The upper surface of the fourth constant diameter section (9) is inclined downward in a direction gradually moving away from the center line of the preform.

6. A forming method for large flanged deep blind hole forgings, characterized in that: The forming method comprises die forging the large flanged deep blind hole forging preform as claimed in any one of claims 1 to 5.

7. The forming method according to claim 6, characterized in that: The large flanged deep blind hole forging comprises, from bottom to top, a first constant diameter section (1), a first expanded diameter section (2) and a second constant diameter section (3) which are connected in sequence. The flanged deep blind hole forging is also provided with a first central blind hole (4), the first central blind hole (4) passing through the second constant diameter section (3) and the first expanded diameter section (2) and extending toward the bottom of the first constant diameter section (1); the outer ring diameter of the second constant diameter section (3) is D1, the diameter of the first central blind hole (4) is D2, the outer ring diameter of the first constant diameter section (1) is D3, and D1>D3>D2; the height of the first constant diameter section (1) is H2, the height of the first expanded diameter section (2) is H3, and the height of the second constant diameter section (3) is H4.

8. The forming method according to claim 7, characterized in that: The height L2 of the third diameter expansion section (6), the height L3 of the second diameter expansion section (5) and the height H2 of the first constant diameter section (1) satisfy the following relationship: H2<L2+L3.

9. The forming method according to claim 7, characterized in that: The diameter D4 of the lower surface of the second diameter expansion section (5) and the outer ring diameter D3 of the first constant diameter section (1) satisfy the following relationship: D4=(0.4-0.7)D3.

10. A large flanged deep blind hole forging, characterized in that: The large flanged deep blind hole forging is prepared by the forming method described in any one of claims 6 to 9.

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