Large ring forging punching method

Abstract

The invention discloses a punching method for large ring forgings, belongs to the technical field of manufacturing of large ring forgings, and solves the problems that in the prior art, large ring forgings made of special materials are prone to forming microcracks during punching, and the consistency of the centers of punches cannot be guaranteed. The punching method comprises the following steps: upsetting a blank for multiple times; heating the blank; a punching positioning ring is placed on the platform and comprises an outer ring and a convex base plate located in the center of the outer ring; the blank is placed on the punching positioning ring, and the upper surface of the blank is pressed down through a solid punch; a pit is formed at the contact part of the lower surface of the blank and the inverted-T-shaped base plate; the solid punch is taken out, the blank is turned over by 180 degrees, the punching positioning ring is removed, the blank is placed on a platform, and the hollow punch is placed in a pit in the lower surface of the blank; and pressing the hollow punch until the hollow punch thoroughly punches the core part of the blank. The punching method can guarantee that the outer surface, the upper end surface and the lower end surface of the blank are good in state.

Description

Technical Field

[0001] The invention relates to the technical field of manufacturing large ring forgings, and in particular to a punching method for large ring forgings. Background Art

[0002] At present, the manufacturing method of large ring forgings usually uses solid billets for blanking, and then punches holes with punches. After punching, the holes are formed by drawing the mandrel or expanding the holes with a horse bar or rolling the ring. Punching can be done by single-sided punching or double-sided punching. Single-sided punching is relatively simple to operate. When the billet is high, the first punch is pressed into the billet, and then the second punch is placed on the first punch, and so on until the hole is penetrated. In the double-sided punching method, after punching on one side, the punch is usually taken out, and then the billet is turned 180°, and then the punch is used to align the position from the back side to punch out the hole. Punches for punching are usually divided into solid punches and hollow punches. Single-sided punching can use hollow punches or solid punches; double-sided punching usually uses solid punches. The advantage of solid punching is that the punching mass is small and material is saved, but the disadvantage is that the equipment pressure requirement is high; hollow punching can reduce the material resistance during punching, but the punching mass is large, which is relatively wasteful of material. When punching large ring forgings on a hydraulic press, solid punches are usually used for punching below Φ400mm, and hollow punches are used for punching of Φ400mm and above. On the other hand, large ring forgings are usually punched on one side, especially when the punching diameter exceeds Φ400mm. However, for large stainless steel or titanium alloy ring forgings with poor high-temperature plasticity and narrow forging range, if single-sided punching is used, the punching time is long. After the billet cools down, the metal on the punched side of the hole is seriously stretched, which is easy to form serious cracks at the punched part. In addition, if there are many inclusions at both ends of the billet, it is also easy to form microcracks during punching. All of the above will cause defects on the end face of the punched hole, which will have an adverse effect on subsequent thermal deformation. Double-sided punching requires a 180° flip, and the large forging billet itself is irregular. Using a free forging press, it is impossible to ensure that the punch center is consistent, which can easily cause the hole to be punched off-center and the holes at both ends are seriously non-concentric. For large ring forgings made of special materials or blanks with many inclusions at both ends, micro cracks are easily formed during punching. Under the free forging press, the existing punching method is used to punch holes, which has an adverse effect on the subsequent thermal deformation such as core rod drawing or horse bar expansion and the inspection of finished products. Summary of the invention

[0003] In view of the above situation, the present invention aims to provide a method for punching large ring forgings, which is used to solve the problems that large ring forgings made of special materials or inclusions at both ends of the blanks are prone to form micro cracks during punching, and the large forging blanks themselves are irregular, and the use of free forging machines cannot ensure the consistency of the punch center.

[0004] The purpose of the present invention is mainly achieved through the following technical solutions:

[0005] The present invention provides a large ring forging punching method, the large ring forging punching method comprising the following steps:

[0006] S1, upsetting the blank multiple times;

[0007] S2, the blank is heated;

[0008] S3. A punching positioning ring is placed on the platform, wherein the punching positioning ring includes an outer ring and a convex-shaped pad located at the center of the outer ring;

[0009] S4. The blank is placed on the punching positioning ring, and a solid punch is used to press down on the upper surface of the blank, and the pressing height does not exceed 1 / 4 of the blank height; a pit is formed at the contact point between the lower surface of the blank and the convex pad;

[0010] S5, take out the solid punch, turn the blank 180 degrees, remove the punching positioning ring, put the blank on the platform, and put the hollow punch on the pit on the lower surface of the blank;

[0011] S6. Press the hollow punch until the hollow punch punches through the center of the blank.

[0012] Furthermore, the components of the large ring forgings include, by mass percentage: C: 0.08% to 0.11%, Si: 0.40% to 0.8%, Mn: 17.0% to 20.0%, Cr: 17% to 20%, N: 0.50% to 0.65%, P: ≤0.030%, S: ≤0.010%, and the remainder is Fe and inevitable trace impurities.

[0013] Furthermore, the inner wall of the outer ring adopts a conical surface with a cone angle of 3° to 5°, and the inner ring bottom diameter d1 of the outer ring = the blank diameter d2 + 10 mm.

[0014] Furthermore, the height of the outer ring is ≥200 mm.

[0015] Further, in S4, the solid punch includes a large head end and a small head end, the diameter of the large head end is larger than the diameter of the small head end, and the cone angle of the solid punch is 4° to 8°.

[0016] Furthermore, in S4, the ratio of the height of the solid punch to the height of the blank is greater than 1 / 3.

[0017] Furthermore, in S4, the lower end of the solid punch is a small head end when punching, and the pressing height does not exceed 1 / 4 of the blank height.

[0018] Furthermore, the hollow punch is a cylinder with a hollow hole inside, the cross section of the hollow hole is trapezoidal, and the aperture of the upper surface of the hollow hole is larger than the aperture of the lower surface.

[0019] Furthermore, the hollow punches include a plurality of hollow punches, wherein the first hollow punch has the largest outer diameter, and the ratio of the outer diameter of the first hollow punch to the diameter of the blank is 1 / 2.5 to 1 / 3.

[0020] Furthermore, the outer diameter of the first hollow punch is 100 to 200 mm smaller than the diameter of the small head end of the solid punch.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] a) In the punching method for large ring forgings of the present invention, the blank is first placed on a punching positioning ring with a convex-shaped pad, and a solid punch is used to punch the blank. A pit of a certain depth can be formed after the punching. After turning the blank over, a hollow punch is used to punch the pit, which can avoid the misalignment of the upper and lower punches. In addition, the double-sided punching of the solid punch and the hollow punch is combined to avoid severe metal drawing and micro cracks, and can ensure that the outer surface of the blank and the upper and lower surfaces are in good condition.

[0023] b) In the large ring forging punching method of the present invention, by accurately controlling the size of the hollow punch and the solid punch, the steps in the punching process, the pressing depth and other parameters, it is possible to ensure that the outer surface and the upper and lower ends of the blank are in good condition.

[0024] c) In the punching method of large ring forgings of the present invention, after pre-punching with a solid punch, the solid forging is flipped 180 degrees, and the punch is separated from the blank by a hollow punch, and the forging can be punched out directly on the platform without replacing the punching plate, thereby improving the punching efficiency.

[0025] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the contents particularly pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are only for the purpose of illustrating specific embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0027] Figure 1 It is a structural schematic diagram of the punching positioning ring of the present invention;

[0028] Figure 2 It is a structural schematic diagram of a solid punch of the present invention;

[0029] Figure 3 It is a structural schematic diagram of the hollow punch of the present invention;

[0030] Figure 4It is a process schematic diagram of the punching method of the present invention;

[0031] Figure 5 This is a schematic diagram of the blank after punching of Comparative Example 1;

[0032] Figure 6 Schematic diagram of the blank after punching in Comparative Example 2.

[0033] Reference numerals

[0034] 1-solid punch, 2-blank, 3-punching positioning ring, 31-outer ring, 32-convex pad, 4-hollow punch, 41-hollow punch, 5-platform, 6-punch, 7-second hollow punch. DETAILED DESCRIPTION

[0035] Preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used to explain the principles of the present invention together with the embodiments of the present invention.

[0036] The inventor found in in-depth research that when punching large stainless steel or titanium alloy ring forgings with poor high-temperature plasticity and narrow forging range, if single-sided punching is used, the punching time is long. After the blank cools down, the metal on the punched side of the hole is seriously stretched, which is easy to form serious cracks at the punched hole. In addition, if there are many inclusions at both ends of the blank, it is also easy to form micro cracks during punching. All of the above will cause defects on the punched end face, which will have an adverse effect on subsequent thermal deformation. When double-sided punching is used, it needs to be flipped 180°, and the large forging blank itself is irregular. When a free forging press is used, it is impossible to ensure that the punch center is consistent, which can easily cause the hole to be punched off-center and the holes at both ends are seriously non-concentric. For large ring forgings of special materials or blanks with many inclusions at both ends, micro cracks are easily formed during punching. Under a free forging press, the use of existing punching methods after punching has an adverse effect on subsequent thermal deformation such as core rod lengthening or horse bar hole expansion and the inspection of finished products.

[0037] The present invention provides a large ring forging punching method, comprising the following steps:

[0038] S1, upsetting the blank multiple times;

[0039] S2, the blank is heated;

[0040] S3, a punching positioning ring 3 is placed on the platform 5, and the punching positioning ring 3 includes an outer ring 31 and a convex-shaped pad 32 located at the center of the outer ring;

[0041] S4, such as Figure 4As shown in (a), the blank 2 is placed on the punching positioning ring 3, and a solid punch 1 is used to press down on the upper surface of the blank 2. The pressing height generally does not exceed 1 / 4 of the blank height, but should reach more than 150mm; a pit is formed at the contact between the lower surface of the blank 2 and the convex pad 32, as shown in FIG. Figure 4 As shown in (b);

[0042] S5, take out the solid punch 1, turn the blank 2 180 degrees, remove the punching positioning ring 3, put the blank on the platform 5, and put the hollow punch 4 on the pit on the lower surface of the blank. Figure 4 As shown in (c);

[0043] S6, press the hollow punch 4 until the hollow punch punches through the core of the blank, and the blank is punched out 6 (punching out means the blank is punched out from the core) and falls on the platform.

[0044] Specifically, the components of the large ring forgings of the present invention include, by mass percentage, C: 0.08% to 0.11%, Si: 0.40% to 0.8%, Mn: 17.0% to 20.0%, Cr: 17% to 20%, N: 0.50% to 0.65%, P: ≤0.030%, S: ≤0.010%, and the balance is Fe and unavoidable trace impurities. The high temperature plasticity of the large ring forgings of the present invention is poor.

[0045] Specifically, in the above S1, the billet has a too large height-to-diameter ratio, which is easy to bend or form a double-drum shape, and needs to be reshaped later, which affects the upsetting effect. At the same time, the high-temperature plasticity is poor and it is easy to crack at the upsetting fracture. Therefore, the height-to-diameter ratio of the billet is controlled to be less than 2.5, for example, 1.6 to 2.3.

[0046] Specifically, in the above S1, the high temperature plasticity of the large ring forgings of the present invention is poor, therefore, the single upsetting ratio cannot be too large, and multiple upsettings are required. Specifically, the single upsetting ratio is controlled to be 1.3-1.5.

[0047] Specifically, in the above S2, the heating time is sufficient to heat the core of the blank through; and long-time heating is avoided as much as possible.

[0048] Specifically, in the above S3, if Figure 1The structure diagram of the punching positioning ring is shown. The punching positioning ring 3 includes an outer ring 31 and a convex-shaped pad 32 located at the center of the outer ring. Optionally, the outer ring 31 and the convex-shaped pad 32 are an integral structure, or a split structure. The inner wall of the outer ring 31 adopts a conical surface with a cone angle of 3° to 5°, such as 3°, 4°, and 5°. The inner ring bottom diameter d1 of the outer ring 31 is equal to the blank diameter d2+10mm. The height of the outer ring 31 is ≥200mm, which is conducive to the upsetting blank being placed in the punching positioning ring 3 and placed on the convex-shaped pad 32. The diameter d3 of the upper surface of the convex head of the convex-shaped pad 32 is equal to the diameter d4+10mm of the hollow punch. The height of the convex head of the convex-shaped pad 32 is ≥100mm, which ensures that it is pressed into the blank to form a pit, and the hollow punch 4 can be smoothly placed after turning over.

[0049] Specifically, the diameter of the upper surface of the convex head of the convex pad 32 is smaller than the diameter of the lower surface of the convex head, that is, the convex head of the convex pad 32 has a cone angle, and the cone angle is 3° to 8°, for example 4°, 5°, 6°, 7°.

[0050] Specifically, in the above S4, if Figure 2 As shown, the solid punch 1 includes a large head end and a small head end, and the diameter of the large head end is larger than that of the small head end. If the taper angle of the solid punch 1 is too large, the diameter difference between the large head end and the small head end is large, the resistance during the punching process increases, and it is not conducive to the subsequent core rod drawing or hole expansion. If the taper angle of the solid punch 1 is too small, it is not conducive to the solid punch 1 being taken out of the blank. Therefore, the taper angle of the solid punch 1 is controlled to be 4° to 8°, for example, 5°, 6°, 7°.

[0051] Specifically, in the above S4, in order to facilitate lifting and removing the solid punch 1 from the blank 2, the ratio of the height of the solid punch to the height of the blank should be greater than 1 / 3 based on the cone angle design.

[0052] Specifically, the small head end of the above-mentioned solid punch is provided with a chamfer, and the chamfer is R10-15mm (for example, R11mm, R12mm, R13mm, R14mm), which is conducive to pressing during punching. The lower end of the solid punch is the small head end when punching, and the pressing height does not exceed 1 / 4 of the blank height, but should reach more than 150mm to ensure that the subsequent punching can break away from the blank and fall onto the platform. Taking a blank height of 1000mm as an example, the pressing height after punching is 150-250mm.

[0053] Specifically, in the above S4, as the solid punch presses down on the center of the upper surface of the blank, the convex pad 32 begins to push into the lower surface of the blank to form a pit; after the solid punch completes the predetermined pressing stroke, the depth of the pit reaches a preset depth of about 100 mm, for example, 95 to 110 mm, which can ensure that the hollow punch in S5 can be placed stably.

[0054] Specifically, in the above S5, since the blank 2 is cooled, punching with a hollow punch can reduce pressure.

[0055] Specifically, in the above S5, after the solid punch is taken out from the blank 2, the blank 2 is turned 180 degrees, the punching positioning ring 3 is removed, and the blank is placed on the platform. At this time, the lower surface of the blank in S4 is turned to the upper end, and the pit on the lower surface of the blank in S4 is also turned to the upper end.

[0056] Specifically, Figure 3 As shown, the hollow punch 4 is a cylinder with a hollow hole 41 inside. The cross-section of the hollow hole 41 is trapezoidal. The aperture of the upper surface of the hollow hole 41 is larger than that of the lower surface. The difference between the aperture of the upper surface and the aperture of the lower surface of the hollow hole 41 is 10 to 40 mm, for example, 15 mm, 20 mm, 25 mm, 30 mm, and 35 mm.

[0057] Specifically, in order to ensure the strength of the hollow punch 4, no deformation occurs during punching, and the core blank can be smoothly extruded from the hollow punch 41. The wall thickness of the upper surface of the hollow punch 4 is 100-150 mm.

[0058] Specifically, in the above S5, the hollow punch 4 is placed in the above pit, which is the center of the blank 2. At this time, pressing down the hollow punch 4 can ensure that it is in the center of the blank, and can be concentric with the concave center formed by the solid punch of the blank in S4, avoiding misalignment of the upper and lower punches.

[0059] Specifically, in the above S6, considering that the hollow head punch is in direct shear contact with the inside of the blank, the outer diameter of the hollow punch is consistent, and the height should not be too long, therefore, multiple hollow punches can be used for punching. The outer diameters of multiple hollow punches decrease successively; during the punching process, after most of the first hollow punch enters the interior of the blank, the second hollow punch 7 is placed. Since the outer diameter of the second hollow punch 7 is smaller than that of the first hollow punch, the second hollow punch 7 does not directly contact the blank, which can significantly reduce contact friction. Specifically, S6 includes: pressing the first hollow punch, and after it is pressed to a certain size, placing the second hollow punch 7 on the first hollow punch, and continuing to press the second hollow punch 7, such as Figure 4 Using multiple hollow punches in sequence, repeat the above steps until the hollow punch punches through the core of the blank, and the punch 6 is separated from the blank and falls onto the platform.

[0060] Specifically, considering that the ratio of the outer diameter d4 of the first hollow punch to the blank diameter d2 is too small, it is necessary to increase the number of hole expansion fires or core rod drawing fires; if the ratio of d4 to the blank diameter d2 is too large, the punching resistance is large, the blank is easy to form an irregular shape with a small top and a large bottom, and the outer surface of the blank is easy to form cracks under the action of tangential tensile stress. Therefore, the ratio of the outer diameter d4 of the first hollow punch to the blank diameter d2 is controlled to be between 1 / 2.5 and 1 / 3.

[0061] Specifically, the outer diameter of the first hollow punch is 100-200 mm smaller than the diameter of the small head end of the solid punch 1, for example, 120 mm, 150 mm, 170 mm, 180 mm, 200 mm.

[0062] Specifically, in the above S6, the outer diameter of the second hollow punch is 10 to 20 mm smaller than the outer diameter of the first hollow punch, and the inner diameter of the lower surface of the second hollow punch is the same as the inner diameter of the upper surface of the first hollow punch; the outer diameter of the third hollow punch is 10 to 20 mm smaller than the outer diameter of the second hollow punch, and the inner diameter of the lower surface of the third hollow punch is the same as the inner diameter of the upper surface of the second hollow punch; the design concept of the remaining hollow punches is the same and will not be repeated.

[0063] Specifically, the outer diameter of the large ring forging of the present invention is 外 2500mm or more, for example 3000-4500mm, inner diameter φ 内 The width is greater than 2200 mm, for example, 2500 to 4000 mm, and the height is greater than 900 mm, for example, 1000 to 1600 mm.

[0064] Compared with the prior art, in the punching method for large ring forgings of the present invention, the blank is first placed on a punching positioning ring with a convex-shaped pad, and a solid punch is used to punch the blank. A pit of a certain depth can be formed after punching. After turning the blank over, a hollow punch is used to punch the pit, which can avoid misalignment of the upper and lower punches. In addition, the double-sided punching of the solid punch and the hollow punch is combined, which can avoid severe metal drawing and microcracks, and can ensure that the outer surface of the blank and the upper and lower surfaces are in good condition.

[0065] In the large ring forging punching method of the present invention, by accurately controlling the size of the hollow punch and the solid punch, the steps in the punching process, the pressing depth and other parameters, it can ensure that the outer surface and the upper and lower ends of the blank are in good condition.

[0066] In the punching method for large ring forgings of the present invention, after pre-punching with a solid punch, the solid forging is flipped 180 degrees, and the punch is separated from the blank by a hollow punch, and the forging can be punched out directly on the platform without replacing the punching plate, thereby improving the punching efficiency.

[0067] The technical solution of the present invention is further explained below in conjunction with specific embodiments.

[0068] Example 1

[0069] The present embodiment provides a method for punching large ring forgings, wherein the components of the ring forgings include, by mass percentage, C: 0.09%, Si: 0.65%, P: 0.01%, S: 0.002%, Mn: 18.5%, Cr: 18.5%, N: 0.61%, and the remainder is Fe and inevitable trace impurities.

[0070] The size of the ring forging in this embodiment is φ 外 =3000mm,φ 内 =2500mm, H=1000mm.

[0071] The steps include:

[0072] S1, the size of the billet before upsetting is φ = 1200mm, the height H1 = 2170mm, the height-to-diameter ratio of the billet before upsetting is 1.8, and upsetting is performed after high-temperature heating; the target height after upsetting is H2 = 1200mm, and upsetting is performed twice by heating, the first upsetting to a height of 1600mm, and the second upsetting to a height of 1200mm, and the outer circle is rolled flat, and the diameter of the lower end of the billet is 1610mm;

[0073] S2, the blank is heated at a temperature of 1200°C for 27 hours, and the core of the blank is heated through;

[0074] S3, a punching positioning ring 3 is placed on the platform, the punching positioning ring 3 comprises an outer ring 31 and a convex-shaped pad 32 located at the center of the outer ring; the inner ring bottom diameter of the outer ring 31 is 1620 mm, the height of the outer ring 31 is 200 mm, the height of the convex head of the convex-shaped pad is 100 mm, the upper surface diameter of the convex head of the convex-shaped pad 32 is 610 mm, and the cone angle is 4°;

[0075] S4, the blank 2 is placed on the punching positioning ring 3, and a solid punch 1 is used to press down on the upper surface of the blank 2. The dimensions of the solid punch 1 are: height 500mm, outer diameter of the small head end is 720mm, cone angle 6°, and the small head end is provided with a chamfer, and the chamfer is R10mm; the solid punch is placed in the center of the blank and punched down, and the pressing height is 200mm;

[0076] S5, take out the solid punch 1, lift the blank, turn it 180 degrees, remove the punching positioning ring 3, put the blank on the platform, put the first hollow punch on the pit on the lower surface of the blank, the outer diameter of the first hollow punch is φ = 600mm, the height is 600mm, the aperture of the upper surface of the hollow punch is 360mm, and the aperture of the lower surface of the hollow punch is 330mm;

[0077] S6. Press the first hollow punch to a depth of 400 mm, then place the second hollow punch on the first hollow punch. The height of the second hollow punch is 800 mm, and the outer diameter of the second hollow punch is φ=590 mm, ensuring that the second hollow punch does not exceed the outer diameter of the first hollow punch. Press the second hollow punch until punching is completed, and the two hollow punches together with the center part punch out of the blank, and then fall onto the platform to complete the punching.

[0078] The outer surface and the upper and lower end surfaces of the blank obtained in this embodiment are in good condition, and the manufacture of large ring forgings can be successfully completed after subsequent hole expansion.

[0079] Example 2

[0080] The present embodiment provides a method for punching large ring forgings, wherein the components of the ring forgings include, by mass percentage, C: 0.11%, Si: 0.5%, P: 0.011%, S: 0.002%, Mn: 19.5%, Cr: 19%, N: 0.65%, and the remainder is Fe and inevitable trace impurities.

[0081] The size of the ring forging is φ 外 =4500mm,φ 内 =4000, H=1600mm.

[0082] The steps include:

[0083] S1, the size of the billet before upsetting is φ = 1500mm, the height H1 = 3250mm, the height-to-diameter ratio of the billet before upsetting is 2.17, and upsetting is performed after high-temperature heating; the target height after upsetting is H2 = 1800mm, and upsetting is performed in two heating steps, the first upsetting to a height of 2400mm, and the second upsetting to a height of 1800mm, and the outer circle is rolled flat, and the diameter size of the lower end of the billet is 2010mm;

[0084] S2, the blank is heated at a temperature of 1220°C for 32 hours, and the core of the blank is heated through;

[0085] S3, a punching positioning ring 3 is placed on the platform, the punching positioning ring 3 comprises an outer ring 31 and a convex-shaped pad 32 located at the center of the outer ring; the inner ring bottom diameter of the outer ring 31 is 2020 mm, the height of the outer ring 31 is 250 mm, the height of the convex head of the convex-shaped pad is 100 mm, the upper surface diameter of the convex head of the convex-shaped pad 32 is 710 mm, and the cone angle is 5°;

[0086] S4, the blank 2 is placed on the punching positioning ring 3, and a solid punch 1 is used to press down on the upper surface of the blank 2. The dimensions of the solid punch 1 are: height 700mm, outer diameter of the small head end 900mm, solid punch taper angle 6°; the small head end is provided with a chamfer, and the chamfer is R11mm; the solid punch is placed in the center of the blank and punched down, and the pressing height is 300mm;

[0087] S5, take out the solid punch 1, lift the blank, turn it 180 degrees, remove the punching positioning ring 3, put the blank on the platform, put the first hollow punch on the pit on the lower surface of the blank, the outer diameter of the first hollow punch is φ = 700mm, the height is 600mm, the aperture of the upper surface of the hollow punch is 460mm, and the aperture of the lower surface of the hollow punch is 425mm;

[0088] S6. Press the first hollow punch to a depth of 400mm, then place the second hollow punch on the first hollow punch. The height of the second hollow punch is 800mm, and the outer diameter of the second hollow punch is φ=690mm, to ensure that the second hollow punch does not exceed the outer diameter of the first hollow punch. When the remaining height of the second hollow punch is 400mm, place the third hollow punch on the second hollow punch until the punching is completed. The three hollow punches together with the core punch out of the blank, and then fall onto the platform to complete the punching.

[0089] The outer surface and the upper and lower end surfaces of the blank obtained in this embodiment are in good condition, and the manufacture of large ring forgings can be successfully completed after subsequent hole expansion.

[0090] The inventor has conducted a large number of experimental studies during the research process, and now uses some solutions with poor surfaces after punching as comparative examples.

[0091] Comparative Example 1

[0092] This comparative example provides a method for punching large ring forgings. The components of the ring forgings are the same as those in Example 1 and will not be described in detail here.

[0093] The punching method of this comparative example comprises the following steps:

[0094] S1. The size of the billet before upsetting is φ=1200mm, the height H1=2170mm, the height-to-diameter ratio of the billet before upsetting is 1.8, and upsetting is performed after high-temperature heating; the target height after upsetting is H2=1200mm, and upsetting is performed in two heating steps, the first upsetting to a height of 1600mm, and the second upsetting to a height of 1200mm, the outer circle is rolled flat, and the diameter of the lower end of the billet is 1610mm.

[0095] S2, the blank is heated at a temperature of 1200°C for 27 hours, and the core of the blank is heated through;

[0096] S3. Place a first hollow punch at the center of the blank. The outer diameter of the first hollow punch is φ=600 mm, the height is 600 mm, the aperture of the upper surface of the hollow punch is 360 mm, and the aperture of the lower surface of the hollow punch is 330 mm;

[0097] S4, press the first hollow punch to a depth of 400 mm, then put in the second hollow punch, the height of the second hollow punch is 800 mm, the outer diameter of the second hollow punch is φ=590 mm, and ensure that the second hollow punch does not exceed the outer diameter of the first hollow punch; press the second hollow punch until the punch bulges out at the bottom of the blank;

[0098] S5. The blank and the punch are hoisted to a special leaking plate (for leaking punches), the third hollow punch is placed above the second hollow punch, and the third hollow punch is pressed until the second hollow punch and the second hollow punch are separated from the core of the blank, thereby completing the punching.

[0099] After punching, the bottom punched end blank has serious tensile cracks. Figure 5 As shown, it is necessary to suspend hot forging and hole expansion and cold working to remove cracks, which affects the production progress and wastes the blank.

[0100] Comparative Example 2

[0101] This comparative example provides a method for punching large ring forgings. The components of the ring forgings are the same as those in Example 2 and will not be described in detail here.

[0102] The punching method is the same as that of Example 2, except that:

[0103] The outer diameter of the small head end of the solid punch 1 in S4 is 750mm, and the cone angle of the solid punch is 3°;

[0104] In S4 of the comparative example, the outer diameter of the small head end of the solid punch is only 50 mm larger than the outer diameter of the first hollow punch. After the hollow punch completes the punching, the inner hole at the lower part of the blank is obviously stretched, and the inner hole forms a step, such as Figure 6 As shown, it is not conducive to subsequent hole expansion or core rod lengthening.

[0105] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for punching large ring forgings, characterized in that: The large ring forging punching method comprises the following steps: S1, upsetting the blank multiple times; S2, the blank is heated; S3, placing a punching positioning ring (3) on the platform, wherein the punching positioning ring (3) comprises an outer ring (31) and a convex-shaped pad (32) located at the center of the outer ring; S4, the blank (2) is placed on the punching positioning ring (3), and a solid punch (1) is used to press down on the upper surface of the blank (2), and the pressing height does not exceed 1 / 4 of the height of the blank; a pit is formed at the contact point between the lower surface of the blank (2) and the convex-shaped pad (32); S5, take out the solid punch (1), turn the blank (2) 180 degrees, remove the punching positioning ring (3), put the blank on the platform, and place the hollow punch (4) on the pit on the lower surface of the blank; S6. Press the hollow punch (4) until the hollow punch punches through the center of the blank.

2. The large ring forging punching method according to claim 1, characterized in that: The components of the large ring forgings include, by mass percentage, C: 0.08% to 0.11%, Si: 0.40% to 0.8%, Mn: 17.0% to 20.0%, Cr: 17% to 20%, N: 0.50% to 0.65%, P: ≤0.030%, S: ≤0.010%, and the remainder is Fe and inevitable trace impurities.

3. The large ring forging punching method according to claim 1, characterized in that: The inner wall of the outer ring (31) is a conical surface with a cone angle of 3° to 5°. The inner ring bottom diameter d1 of the outer ring (31) is equal to the blank diameter d2+10 mm.

4. The large ring forging punching method according to claim 3, characterized in that: The height of the outer ring (31) is ≥200 mm.

5. The large ring forging punching method according to claim 1, characterized in that: In S4, the solid punch (1) comprises a large head end and a small head end, the diameter of the large head end is larger than the diameter of the small head end, and the cone angle of the solid punch (1) is 4° to 8°.

6. The large ring forging punching method according to claim 5, characterized in that: In the above S4, the ratio of the height of the solid punch to the height of the blank is greater than 1 / 3.

7. The large ring forging punching method according to claim 1, characterized in that: In the above S4, the lower end of the solid punch is a small head end when punching, and the pressing height does not exceed 1 / 4 of the blank height.

8. The large ring forging punching method according to claim 1, characterized in that: The hollow punch (4) is a cylinder with a hollow punch hole (41) inside. The cross section of the hollow punch hole (41) is trapezoidal, and the hole diameter of the upper surface of the hollow punch hole (41) is larger than the hole diameter of the lower surface.

9. The large ring forging punching method according to any one of claims 1 to 8, characterized in that: The hollow punches include a plurality of punches, among which the first hollow punch has the largest outer diameter, and the ratio of the outer diameter of the first hollow punch to the diameter of the blank is 1 / 2.5 to 1 / 3.

10. The large ring forging punching method according to claim 9, characterized in that: The outer diameter of the first hollow punch is 100-200 mm smaller than the diameter of the small head end of the solid punch.

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