Forging method of large-taper conical shell forge piece

Abstract

The invention provides a forging method for a large-taper conical shell forge piece, and relates to the technical field of forging. In the forging method, in the process that a hollow cylindrical blank is drawn out and blanked to form a large head end and a small head end of a step cylinder prefabricated blank, as the outer diameter of the hollow cylindrical blank is equal to the outer diameter of the large head end of the step cylinder prefabricated blank, the large-taper conical shell forge piece is formed; therefore, the end part, used for forming the large-head end of the step cylinder prefabricated blank, of the hollow cylinder-shaped blank does not need to be forged, and the large-head end of the step cylinder prefabricated blank does not have a concave center condition; due to the fact that the check ring is arranged on the core rod used for drawing-out and blanking, and the end portion, used for forming the small head end of the step barrel prefabricated blank, of the hollow barrel-shaped blank abuts against the check ring in the drawing-out and blanking process, the situation that the small head end of the step barrel prefabricated blank is concaved can be prevented.

Description

Technical Field

[0001] The invention relates to the technical field of forging, in particular to a forging method for a large-taper cone shell forging. Background Art

[0002] At present, the taper of cone shell forgings on the market is relatively small, and the taper is generally less than 25 degrees. The commonly used production methods are as follows: (1) According to the taper of the cone shell forging, a hollow cylindrical blank is forged first, and then a special punch is used to punch the blank to make the blank fit the lower die; due to the large number of product size specifications, this method requires the use of special punches and lower dies of different specifications for products of different specifications, and the auxiliary tool investment is large, and it cannot be applied to all specifications of cone shell forgings. (2) The blank is forged into a cylindrical shape, and the edge is forged by widening the hammer head and the electric turntable, and it is gradually pressed down until the height of the forging is reached. This method is only suitable for cone shell forgings with small specifications; for cone shell forgings with large height and taper, a larger amount of edge opening is required, which is easy to cause the outer circle to be broken and the waist to collapse. (3) The steel ingot is subjected to drawing, upsetting, punching, and drawing to obtain a step cylinder preform, and then the step cylinder preform is expanded to obtain a conical shell forging. However, this method is currently mainly used for the manufacture of conical forgings with a small taper (about 15 degrees). For the preparation of conical shell forgings with a large taper, such as a taper greater than 25 degrees, a length greater than 1500mm, and an inner diameter of the small end less than 2000mm, the step cylinder preform obtained by this method is prone to a concave center at the small end, resulting in the inability to obtain a step cylinder preform of suitable size for subsequent expansion. Summary of the invention

[0003] The problem solved by the present invention is at least one of the following problems: when preparing a conical shell forging with a taper greater than 25 degrees, a length greater than 1500mm, and an inner diameter of the small head end less than 2000mm by expanding the hole of the step cylinder preform, how to avoid the concave center of the small head end of the step cylinder preform obtained by the drawing method.

[0004] In order to solve the above problems, the present invention provides a forging method for a large-taper cone shell forging, comprising:

[0005] Step S1, sequentially performing jaw pressing, primary upsetting, KD drawing, secondary upsetting and punching on the steel ingot to obtain a first intermediate billet;

[0006] Step S2, subjecting the first intermediate blank to core rod drawing to obtain a step tube preform; the step tube preform has a large head end and a small head end, and the outer diameter of the large head end is D; the core rod used in the core rod drawing process comprises a core rod body, a retaining ring and a flange; the flange is provided at one end of the core rod body, the retaining ring is sleeved on the core rod body, the retaining ring is closely arranged against the flange and is located between the other end of the core rod body and the flange; wherein, subjecting the first intermediate blank to core rod drawing to lengthen, comprises: drawing the first intermediate blank to a hollow cylindrical blank with an outer diameter of D; drawing and blanking the hollow cylindrical blank to sequentially form the large head end and the small head end; during the drawing and blanking process, the end of the hollow cylindrical blank used to form the small head end abuts against the retaining ring;

[0007] Step S3, performing primary reaming, small head end closing, leveling and secondary reaming on the step tube preform in sequence to obtain a conical shell forging.

[0008] Optionally, the design length L of the large-taper cone shell forging is greater than 1500 mm, the design taper θ is greater than 25 degrees, and the design inner diameter D1 of the small head end is less than 2000 mm.

[0009] Optionally, in step S2, the step tube preform includes a first hollow tube, a second hollow tube, a third hollow tube, a fourth hollow tube, and a fifth hollow tube which are connected in sequence and have the same inner diameter; the outer diameters of the first hollow tube, the second hollow tube, the third hollow tube, the fourth hollow tube, and the fifth hollow tube decrease in sequence.

[0010] Optionally, in step S2, the outer diameters of the first hollow cylinder, the second hollow cylinder, the third hollow cylinder, the fourth hollow cylinder, and the fifth hollow cylinder are 3610 mm, 3430 mm, 3240 mm, 3040 mm, and 2820 mm respectively, the inner diameters are all 1180 mm, and the lengths are all 460 mm.

[0011] Optionally, the design length L of the cone shell forging is 2000 mm, the design taper θ is 30 degrees, the design inner diameter D1 of the small head end is 1680 mm, the design outer diameter D2 of the small head end is 2895 mm, the design inner diameter D3 of the large head end is 3985 mm, and the design outer diameter D4 of the large head end is 5135 mm;

[0012] In the step S3, the step tube preform is subjected to primary reaming, small head end closing, flattening and secondary reaming in sequence to obtain a cone shell forging, including:

[0013] Step S31, the step tube preform is expanded once using a saddle with a diameter of 1120 mm to obtain a second intermediate blank in a conical shell shape; the inner diameter of the small end of the second intermediate blank is 1850 mm;

[0014] Step S32, closing the second intermediate blank until the inner diameter of the small end thereof is 1450 mm, and then flattening the second intermediate blank to obtain a third intermediate blank; the length of the third intermediate blank is 2000 mm;

[0015] Step S33, performing secondary expansion on the third intermediate blank to obtain a conical shell forging.

[0016] Optionally, in step S32, the closing is performed using an upper flat anvil and a lower V anvil with a width of 1200 mm.

[0017] Optionally, in step S32, the closing is performed in a stepped closing manner.

[0018] Optionally, in step S32, the closing amount of a single pass in the closing process is not higher than 100 mm.

[0019] Optionally, in step S33, the third intermediate billet is subjected to secondary hole expansion to obtain a conical shell forging, including: heating the third intermediate billet to 1240°C to 1260°C, keeping it warm for 6h to 8h, and then cooling it; when the temperature of the inner wall and end face of the small head end of the third intermediate billet drops to 1000°C, hole expansion forging is performed.

[0020] Optionally, the cooling treatment is performed by spraying or mist cooling.

[0021] Compared with the prior art, in the present invention, in the process of drawing and cutting the hollow cylindrical billet to form the big head end and the small head end of the step cylinder preform, since the outer diameter of the hollow cylindrical billet is equal to the outer diameter of the big head end of the step cylinder preform, the end of the hollow cylindrical billet used to form the big head end of the step cylinder preform does not need to be forged, so the big head end of the step cylinder preform will not be concave; since a retaining ring is provided on the core rod used for drawing and cutting, and the end of the hollow cylindrical billet used to form the small head end of the step cylinder preform abuts against the retaining ring during the drawing and cutting process, it is possible to prevent the small head end of the step cylinder preform from being concave. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a step cylinder preform in an embodiment of the present invention;

[0023] Figure 2 It is a structural schematic diagram of an embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of using a mandrel to draw and cut materials in an embodiment of the present invention;

[0025] Figure 4It is a schematic diagram of the hollow cylindrical blank in the process of drawing and cutting when the end portion used to form the small head end is away from the retaining ring;

[0026] Figure 5 A schematic diagram of a cone shell forging in an embodiment of the present invention;

[0027] Figure 6 It is a schematic diagram of evenly dividing the conical shell forging along its length direction in an embodiment of the present invention;

[0028] Figure 7 It is a schematic diagram of placing the step cylinder preform on the horse frame through the horse lever in an embodiment of the present invention;

[0029] Figure 8 It is a schematic diagram of the step tube preform after one hole expansion is performed by a horse bar in an embodiment of the present invention;

[0030] Fig. 9 It is a schematic diagram of closing the small end of the second intermediate blank in an embodiment of the present invention;

[0031] Fig.10 It is a schematic diagram of flattening the second intermediate blank after the small end is closed in an embodiment of the present invention;

[0032] Fig.11 Schematic diagram of the third intermediate blank before it is placed on the horse stand.

[0033] Description of reference numerals:

[0034] 1. Step tube preform; 11. First hollow tube; 12. Second hollow tube; 13. Third hollow tube; 14. Fourth hollow tube; 15. Fifth hollow tube; 2. Mandrel; 21. Mandrel body; 22. Circlip; 23. Flange; 3. Second intermediate blank; 4. Third intermediate blank; 5. Horse bar; 6. Closing sleeve. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be interpreted as being limited to the embodiments described herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0036] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by those skilled in the art to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific implementation methods and are not intended to limit this application;

[0037] The term "including" and its variations used in this article are open inclusions, that is, "including but not limited to"; the term "based on" is "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first" and "second" mentioned in the present invention are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, the meaning of "multiple" is two or more.

[0038] It should be noted that in the present invention, the big end of the step tube preform refers to the end of the step tube preform with a larger outer diameter, and the small end of the step tube preform refers to the end of the step tube preform with a smaller outer diameter. The big end of the cone shell forging refers to the end of the cone shell forging with a larger outer diameter, and the small end of the cone shell forging refers to the end of the cone shell forging with a smaller outer diameter. The taper of the cone shell forging is the angle between the generatrix of the inner wall contour of the cone shell forging and the central axis of the cone shell forging. It should be noted that Figure 3 , Figure 4 and Fig. 9 A is the upper flat anvil, B is the lower V anvil, Figure 7 C in the middle is a cutting board. Fig.10 D in the middle is the cover plate. Fig.11 In the middle, E is the horse frame and F is the mobile walkway.

[0039] In the related art, the conical shell forgings can be prepared by the following method: the steel ingot is subjected to drawing, upsetting, punching, and drawing and blanking to obtain a step tube preform, and then the step tube preform is expanded to obtain a conical shell forging. However, at present, this method is mainly used for the manufacture of conical forgings with a small taper (a taper of about 15 degrees). For the preparation of conical shell forgings with a taper greater than 25 degrees, a length greater than 1500mm, and an inner diameter of the small head end less than 2000mm, the blank obtained by punching needs to have a larger outer diameter and a smaller inner diameter to meet the dimensional requirements of the overall inner diameter and the outer diameter of the large head end of the step tube preform. Therefore, the outer diameter of the blank obtained by punching is much larger than the inner diameter, and the side wall of the blank is thicker. During the process of drawing and blanking the core rod, the material feeding speed of the part close to the outer wall surface of the blank will be faster than that of the part close to the inner hole of the blank. In the process of forming the large head end and the small head end of the step tube preform in sequence by drawing and blanking, the small head end is prone to produce a very large bell mouth (such as Figure 4 As shown), the small head end is concave, which makes it impossible to obtain a step tube preform of suitable size for subsequent hole expansion.

[0040] In view of the above problems, this embodiment provides a forging method for a large-taper cone shell forging, comprising:

[0041] Step S1, sequentially performing jaw pressing, primary upsetting, KD drawing, secondary upsetting and punching on the steel ingot to obtain a first intermediate billet;

[0042] Step S2, the first intermediate blank is stretched by a mandrel to obtain a step tube preform 1; Figure 1 As shown, the step tube preform 1 has a large head end and a small head end, and the outer diameter of the large head end is D; Figure 2 As shown, the mandrel 2 used in the mandrel drawing process includes a mandrel body 21, a retaining ring 22 and a flange 23; the flange 23 is arranged at one end of the mandrel body 21, the retaining ring 22 is sleeved on the mandrel body 21, the retaining ring 22 is arranged close to the flange 23 and is located between the other end of the mandrel body 21 and the flange 23; wherein, the mandrel drawing of the first intermediate blank comprises: drawing the first intermediate blank into a hollow cylindrical blank with an outer diameter of D; drawing and blanking the hollow cylindrical blank to sequentially form the large head end and the small head end; as shown Figure 3 As shown, during the drawing and blanking process, the end of the hollow cylindrical blank used to form the small head end abuts against the retaining ring 22; Figure 4 As shown in FIG. 1 , if during the drawing and blanking process, the end of the hollow cylindrical blank used to form the small head end is away from the retaining ring 22, the following situation will occur: Figure 4 The concave center of the small head end is shown.

[0043] Step S3, the step tube preform 1 is subjected to primary reaming, small head end closing, leveling and secondary reaming in sequence to obtain a conical shell forging.

[0044] In the embodiment of the present invention, in the process of drawing and cutting the hollow cylindrical billet to form the big head end and the small head end of the step cylinder preform 1, since the outer diameter of the hollow cylindrical billet is equal to the outer diameter of the big head end of the step cylinder preform, the end of the hollow cylindrical billet used to form the big head end of the step cylinder preform does not need to be forged, and thus the big head end of the step cylinder preform will not be concave; since a retaining ring 22 is provided on the core rod used for drawing and cutting, and the end of the hollow cylindrical billet used to form the small head end of the step cylinder preform abuts against the retaining ring 22 during the drawing and cutting process, it is possible to prevent the small head end of the step cylinder preform 1 from being concave.

[0045] In some embodiments of the present invention, Figure 5 As shown, the design length L of the large-taper cone shell forging is greater than 1500 mm, the design taper θ is greater than 25 degrees, and the design inner diameter D1 of the small head end is less than 2000 mm.

[0046] The cone shell forgings prepared in the embodiment of the present invention are as follows Figure 5 As shown, the shape of the cone shell forging can be regarded as a parallelogram rotated along the center line, or it can be understood as the upper and lower bases of the rectangular cross section per unit area are offset along the radial direction by the same drop value and then rotated along the center line. Therefore, the cone shell forging can be formed by expanding the step cylinder preform 1. Figure 1 As shown, exemplarily, the step cylinder preform 1 is composed of a first hollow cylinder 11, a second hollow cylinder 12, a third hollow cylinder 13, a fourth hollow cylinder 14, and a fifth hollow cylinder 15 which are connected in sequence and have the same inner diameter; the outer diameters of the first hollow cylinder 11, the second hollow cylinder 12, the third hollow cylinder 13, the fourth hollow cylinder 14, and the fifth hollow cylinder 15 are reduced in sequence to form 5 groups of outer steps; specifically, the process of expanding the prefabricated step cylinder preform 1 to form a conical shell forging includes: gradually reducing the difference between adjacent outer steps of the step cylinder preform 1 through local expansion until the outer contour of the step cylinder preform 1 is a smooth curved surface, and then performing synchronous expansion.

[0047] In the actual production process, the size of the step tube preform 1 needs to be determined according to the design size of the cone shell forging. Figure 6As shown, the cone shell forging can be divided equally along its length direction, and each part of the forging obtained can be regarded as a parallelogram rotated along the center line. Since the cone shell forging is made by expanding the step cylinder preform 1, the wall thickness of the billet gradually decreases in the radial direction during the expansion process, and its inner and outer diameters are increasing, but the material does not move in the axial direction; therefore, the length of each hollow cylinder constituting the step cylinder preform 1 is equal to the generatrix length of the outer contour of the forging obtained after the cone shell forging is divided equally.

[0048] For example, Figure 5 As shown, the design length L of the cone shell forging is 2000mm, the design taper θ is 30 degrees, the design inner diameter D1 of the small head end is 1680mm, the design outer diameter D2 of the small head end is 2895mm, the design inner diameter D3 of the large head end is 3985mm, and the design outer diameter D4 of the large head end is 5135mm; accordingly, Figure 1 As shown, the step tube preform 1 includes a first hollow tube 11, a second hollow tube 12, a third hollow tube 13, a fourth hollow tube 14, and a fifth hollow tube 15 which are connected in sequence and have the same inner diameter; the outer diameters of the first hollow tube 11, the second hollow tube 12, the third hollow tube 13, the fourth hollow tube 14, and the fifth hollow tube 15 are 3610mm, 3430mm, 3240mm, 3040mm, and 2820mm respectively, the inner diameters are all 1180mm, and the lengths are all 460mm.

[0049] For the preparation of the cone shell forging of the upper specification, in the step S3, the step tube preform 1 is subjected to primary reaming, small head end closing, flattening and secondary reaming in sequence to obtain the cone shell forging, including:

[0050] Step S31: Figure 7-8 As shown, the step tube preform 1 is expanded once using a 1120 mm diameter horse bar 5 to obtain a conical shell-shaped second intermediate blank 3; the inner diameter of the small end of the second intermediate blank 3 is 1850 mm;

[0051] Step S32: Figure 9-10 As shown, the second intermediate blank 3 is closed until the inner diameter of the small end is 1450 mm, and then flattened to obtain a third intermediate blank 4; the length of the third intermediate blank 4 is 2000 mm;

[0052] Step S33: Fig.11 As shown, the third intermediate blank 4 is subjected to secondary hole expansion to obtain a conical shell forging.

[0053] In the prior art, in the process of hole expansion using the horse lever 5, local hole expansion is performed first, so the part that contacts the anvil plate first (the large end of the billet) is expanded first, and during the hole expansion process, the height difference between adjacent outer steps gradually decreases, and the taper of the forging is gradually formed until there is no height difference between the various parts of the billet, and then synchronous hole expansion is performed; during this process, the step tube preform 1 is always in the process of rotating, and since the inner diameter of the small end of the step tube preform 1 is small, the gap between the inner wall of the small end of the step tube preform 1 and the horse lever 5 is small. During the entire hole expansion process, the small end of the step tube preform 1 is always expanded by the reaction force of the horse lever 5, and since the hole is expanded to the small end of the preform at the end, During the hole expansion process, the inner diameter of the small end of the preform is constantly increasing, resulting in an excessively large inner diameter of the small end of the forging. In order to solve the above problem, in this embodiment, the step tube preform 1 is first expanded using a lever 5 with a diameter of 1120 mm to obtain a second intermediate blank 3 in the shape of a conical shell with an inner diameter of 1850 mm at the small end. The inner diameter of the small end of the second intermediate blank 3 is larger than the designed inner diameter of the small end of the conical shell forging (1680 mm). Therefore, in this embodiment, the small end is further closed and smoothed to obtain a third intermediate blank 4 with a smaller inner diameter at the small end, and the inner diameter of the small end is 1450 mm. In order to make the size of the forging meet the requirements, a second hole expansion is performed to obtain the final forging.

[0054] In some embodiments of the present invention, in step S32, the closing is performed by using an upper flat anvil and a lower V anvil with a width of 1200 mm. By inserting the horse bar 5 into the closing sleeve 6, the operating machine clamps the horse bar 5 and inserts it from the large end of the second intermediate blank 3, and the closing sleeve 6 is pressed against the inner wall of the small end of the second intermediate blank 3, and then the upper flat anvil and the lower V anvil are used to close the mouth, thereby preventing the blank from moving during the closing process.

[0055] In some embodiments of the present invention, in step S32, the closing is performed in a stepped manner.

[0056] In some embodiments of the present invention, in step S32, the amount of closing in a single pass during the closing process is not higher than 100 mm, thereby preventing cracks on the end surface caused by too much closing in a single pass.

[0057] In some embodiments of the present invention, in step S33, the third intermediate billet 4 is subjected to secondary hole expansion to obtain a conical shell forging, including: heating the third intermediate billet 4 to 1240°C to 1260°C, keeping it warm for 6h to 8h, and then cooling it; when the temperature of the inner wall and end face of the small head end of the third intermediate billet 4 drops to 1000°C, hole expansion forging is performed.

[0058] In some embodiments of the present invention, the temperature reduction treatment is performed by spraying or mist cooling. In this embodiment, the temperature of the inner wall and end surface of the small end of the third intermediate blank 4 is quickly reduced by spraying, mist cooling and other measures to increase its deformation resistance.

[0059] The present invention is further described below in conjunction with specific embodiments.

[0060] Example 1

[0061] like Figure 5 As shown, the design length L of the cone shell forging is 2000mm, the design taper θ is 30 degrees, the design inner diameter D1 of the small head end is 1680mm, the design outer diameter D2 of the small head end is 2895mm, the design inner diameter D3 of the large head end is 3985mm, and the design outer diameter D4 of the large head end is 5135mm; the preparation process of the cone shell forging is as follows:

[0062] A1. Heat the steel ingot to 1250℃, keep it warm for 24h, press the jaws, chamfer, gas cut the ingot body at the nozzle end, heat it to 1270℃, keep it warm for 30h, upset it to an axial size of 1700mm and a radial size of 3730mm, then use the KD compaction method to draw it to an axial size of 4690mm and a radial size of 2250mm, heat it to 1270℃, keep it warm for 30h, upset it to an axial size of 1700mm and a radial size of 3700mm, then punch it to obtain the first intermediate blank; the inner diameter of the first intermediate blank is 1200mm.

[0063] A2, heating the first intermediate blank to 1250° C., keeping the temperature for 12 hours, and then drawing the first intermediate blank into a hollow cylindrical blank with an outer diameter of 3610 mm; Figure 3 As shown, the hollow cylindrical blank is stretched and blanked to form a large head end of a step cylinder preform 1 and a small head end of the step cylinder preform 1 in sequence, so as to obtain a step cylinder preform 1; wherein the step cylinder preform 1 is composed of a first hollow cylinder 11, a second hollow cylinder 12, a third hollow cylinder 13, a fourth hollow cylinder 14, and a fifth hollow cylinder 15 which are connected in sequence and have the same inner diameter; the outer diameters of the first hollow cylinder 11, the second hollow cylinder 12, the third hollow cylinder 13, the fourth hollow cylinder 14, and the fifth hollow cylinder 15 are 3610mm, 3430mm, 3240mm, 3040mm, and 2820mm respectively, their inner diameters are 1180mm, and their lengths are all 460mm; as shown Figure 2 As shown, the mandrel 2 used in the drawing and blanking process includes a mandrel body 21, a retaining ring 22 and a flange 23; the flange 23 is arranged at one end of the mandrel body 21, and the retaining ring 22 is sleeved on the mandrel body 21; Figure 3 As shown, during the drawing and blanking process, the end of the hollow cylindrical blank used to form the small head end of the step cylinder preform 1 abuts against the retaining ring 22.

[0064] A3, heating the step tube preform 1 to 1250°C and keeping it warm for 8 hours. Figure 7 and Figure 8 As shown, a hole is expanded once using a horse bar 5, a horse frame and an anvil with a diameter of 1120 mm to obtain a conical shell-shaped second intermediate blank 3; the inner diameter of the small head end of the second intermediate blank 3 is 1850 mm.

[0065] A4. Figure 9-10 As shown, the second intermediate blank 3 is heated to 1250°C and kept warm for 8 hours, and the second intermediate blank 3 is closed until the inner diameter of the small end is 1450mm, and then flattened to obtain the third intermediate blank 4; the length of the third intermediate blank 4 is 2000mm, and the closing is carried out in a stepped closing manner, and the closing is carried out using an upper flat anvil and a lower V-anvil with a width of 1200mm.

[0066] A5. Fig.11 As shown, the third intermediate billet 4 is heated to 1250°C, kept warm for 6 hours, and then placed on a rack for 20 to 30 minutes. During this period, a spraying method is used for cooling treatment. When the temperature of the inner wall and end surface of the small head end of the third intermediate billet 4 drops to 1000°C, hole expansion forging is performed to obtain a conical shell forging.

[0067] Comparative Example

[0068] The difference from Example 1 is that in step A2, during the drawing and blanking process, the end of the small head of the hollow cylindrical blank used to form the step tube preform 1 is away from the retaining ring 22; during the drawing and blanking process, the small head end of the blank is concave.

[0069] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A forging method for a large-taper cone shell forging, characterized in that: include: Step S1, sequentially performing jaw pressing, primary upsetting, KD drawing, secondary upsetting and punching on the steel ingot to obtain a first intermediate blank; Step S2, the first intermediate blank is subjected to mandrel drawing to obtain a step tube preform (1); the step tube preform (1) has a large head end and a small head end, and the outer diameter of the large head end is D; the mandrel (2) used in the mandrel drawing process comprises a mandrel body (21), a retaining ring (22) and a flange (23); the flange (23) is provided at one end of the mandrel body (21), the retaining ring (22) is sleeved on the mandrel body (21), and the retaining ring (22) is tightly The flange (23) is arranged close to the mandrel body (21) and is located between the other end of the mandrel body (21) and the flange (23); wherein the mandrel drawing of the first intermediate blank comprises: drawing the first intermediate blank into a hollow cylindrical blank with an outer diameter of D; drawing and blanking the hollow cylindrical blank to sequentially form the large end and the small end; during the drawing and blanking process, the end of the hollow cylindrical blank used to form the small end abuts against the retaining ring (22); Step S3, the step tube preform (1) is subjected to primary reaming, small head end closing, leveling and secondary reaming in sequence to obtain a conical shell forging.

2. The forging method of a large-taper cone shell forging according to claim 1, characterized in that: The design length L of the large-taper cone shell forging is greater than 1500 mm, the design taper θ is greater than 25 degrees, and the design inner diameter D1 of the small head end is less than 2000 mm.

3. The forging method of a large-taper cone shell forging according to claim 1, characterized in that: In step S2, the step tube preform (1) includes a first hollow tube (11), a second hollow tube (12), a third hollow tube (13), a fourth hollow tube (14), and a fifth hollow tube (15) which are connected in sequence and have the same inner diameter, and the outer diameters of the first hollow tube (11), the second hollow tube (12), the third hollow tube (13), the fourth hollow tube (14), and the fifth hollow tube (15) decrease in sequence.

4. The forging method of a large-taper cone shell forging according to claim 3, characterized in that: In step S2, the outer diameters of the first hollow cylinder (11), the second hollow cylinder (12), the third hollow cylinder (13), the fourth hollow cylinder (14), and the fifth hollow cylinder (15) are 3610 mm, 3430 mm, 3240 mm, 3040 mm, and 2820 mm, respectively, the inner diameters are all 1180 mm, and the lengths are all 460 mm.

5. The forging method of a large-taper cone shell forging according to claim 4, characterized in that: The design length L of the cone shell forging is 2000 mm, the design taper θ is 30 degrees, the design inner diameter D1 of the small head end is 1680 mm, the design outer diameter D2 of the small head end is 2895 mm, the design inner diameter D3 of the large head end is 3985 mm, and the design outer diameter D4 of the large head end is 5135 mm; In the step S3, the step tube preform (1) is subjected to primary reaming, small head end closing, flattening and secondary reaming in sequence to obtain a cone shell forging, including: Step S31, the step tube preform (1) is expanded once using a lever (5) with a diameter of 1120 mm to obtain a second intermediate blank (3) in a conical shell shape; the inner diameter of the small end of the second intermediate blank (3) is 1850 mm; Step S32, closing the second intermediate blank (3) until the inner diameter of the small end thereof is 1450 mm, and then flattening the second intermediate blank (3) to obtain a third intermediate blank (4); the length of the third intermediate blank (4) is 2000 mm; Step S33, performing secondary expansion on the third intermediate blank (4) to obtain a conical shell forging.

6. The forging method of a large-taper cone shell forging according to claim 5, characterized in that: In the step S32, the closing is performed using an upper flat anvil and a lower V anvil with a width of 1200 mm.

7. The forging method of a large-taper cone shell forging according to claim 5, characterized in that: In the step S32, the closing is performed in a stepped closing manner.

8. The forging method of a large-taper cone shell forging according to claim 5, characterized in that: In the step S32, the closing amount of a single pass in the closing process is not higher than 100 mm.

9. The forging method of a large-taper cone shell forging according to claim 5, characterized in that: In the step S33, the third intermediate billet (4) is subjected to secondary hole expansion to obtain a conical shell forging, including: heating the third intermediate billet (4) to 1240°C to 1260°C, keeping the temperature for 6h to 8h, and then cooling the billet; when the temperature of the inner wall and end face of the small head end of the third intermediate billet (4) drops to 1000°C, hole expansion forging is performed.

10. The forging method of a large-taper cone shell forging according to claim 9, characterized in that: The cooling treatment is carried out by spraying or mist cooling.

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