A forging method of 35CrNi3MoV cylinder
Through multiple hot forging and deformation improvement processes, the problems of internal defects and coarse grains in the 35CrNi3MoV cylinder were solved, thereby improving the cylinder's pressure-bearing capacity and service life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGYIN ZENKUNG FORGING CO LTD
- Filing Date
- 2023-09-21
- Publication Date
- 2026-06-16
AI Technical Summary
The 35CrNi3MoV cylinder produced by traditional forging methods has more internal defects and coarser grains, resulting in poor pressure resistance and short service life.
The process involves multiple forging steps, including billet heating, rolling the outer circle, upsetting, drawing, squaring, punching, and low-temperature forging. Combined with the deformation improvement process, interleaved forging marks are formed. Internal defects are improved through multiple large deformations, and the grains are refined by forging at low temperatures.
It improved the flaw detection pass rate of the cylinder, refined the internal grains, enhanced the strength and hardness of the billet, improved the density of the structure, reduced material cracks, and improved the pressure bearing capacity and service life of the cylinder.
Smart Images
Figure CN117259636B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of forging technology, and more particularly to a forging method for a 35CrNi3MoV cylinder. Background Technology
[0002] 35CrNi3MoV is a medium-carbon medium-alloy steel, commonly used in the manufacture of load-bearing and transmission structural components in nuclear power, thermal power, mining, and metallurgy. However, with the development of the times, the performance requirements for 35CrNi3MoV steel are becoming increasingly higher.
[0003] The 35CrNi3MoV cylinder is used as a hydrogenation section, and its internal microstructure requires high quality. Traditional forging methods involving upsetting, drawing, and punching result in cylinders with numerous internal defects and coarse grains, leading to poor pressure resistance and a short service life. Therefore, addressing this problem is crucial. Summary of the Invention
[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a forging method for 35CrNi3MoV cylinders to solve the problem that the cylinders have many internal defects and coarse grains, resulting in poor pressure bearing capacity.
[0005] To achieve the above objectives, the technical solution of the present invention is as follows:
[0006] A forging method for a 35CrNi3MoV cylinder;
[0007] Includes the following steps:
[0008] Step S1, billet heating: The billet is heated to 1230℃ and then held at that temperature;
[0009] Step S2, First forging: Roll the outer circle of the billet and upset the billet to the specified size;
[0010] Step S3, Second Forging: The billet is drawn into an octagonal shape, then upset and squared;
[0011] Step S4, Third Forging: Flatten the billet into a square shape using the FM method;
[0012] Step S5, Fourth Forging: Upsetting the billet, followed by punching;
[0013] Step S6, Fifth Forging: Insert a mandrel into the billet, then draw it out while leaving some deformation, and then air cool it until the surface temperature of the billet is 350-400℃.
[0014] Step S7, Sixth Forging: The furnace temperature is raised to 350-400℃ and then held; the billet is placed in the furnace and heated to 650℃ and held; then the furnace temperature is raised to 940℃ and held; the billet is removed from the furnace and finished into a finished product.
[0015] The further technical solution is as follows: Step S1, billet heating: the billet is heated to 1230℃ and then kept at that temperature for 5-7 hours.
[0016] The further technical solution is as follows: Step S2, first forging: roll the outer circle of the billet, roll the amount of 30-50mm, and upset the billet height to 800mm; then heat to 1250℃ and hold for 4-6 hours.
[0017] The further technical solution is as follows: Step S3, second forging: the billet is drawn octagonally to 970*1960mm, then upset to 1510*850mm and squared to 1100*1100*1260mm; then heated to 1250℃ and held for 4-6 hours.
[0018] The further technical solution is as follows: Step S4, third fire forging: the billet FM is drawn flat to 900*700*2400mm; then heated to 1250℃ and held for 2-3 hours.
[0019] The further technical solution is as follows: Step S5, fourth fire forging: the height of the upsetting billet is increased to 800mm, and then a hole is punched; the hole diameter is Φ550mm; then it is heated to 1250℃ and held for 4-6 hours.
[0020] The further technical solution is as follows: Step S6, fifth forging: insert a mandrel with a size of Φ525-Φ445*3000mm into the billet, then draw it out with a flat anvil on the upper side and a V-shaped anvil on the lower side, leaving a deformation amount of 5-15%; heat it to 1200℃ and hold it for 4-6 hours; then air cool it to the surface temperature of the billet: 350-400℃.
[0021] The further technical solution is as follows: Step S7, sixth fire forging: after the furnace temperature is raised to 350-400℃, it is held for 4-5 hours; the billet is placed in the furnace and heated to 650℃ and held for 3-4 hours, then the furnace temperature is raised to 940℃ and held for 8-10 hours, the billet is taken out of the furnace and finished into a finished product.
[0022] The further technical solution is as follows:
[0023] In step S2, the first forging process includes a first deformation improvement process after upsetting the billet:
[0024] The end face of the billet is tilted at a certain angle and forged to form forging marks on the end face of the billet; by moving and rotating the billet, the forging marks are distributed in an alternating pattern along the end face of the billet.
[0025] In step S3, the second forging process, after the billet is drawn octagonally, a second deformation improvement process is also included.
[0026] The billet is tilted at a certain angle along the axis and its surface is forged to form forging marks. By moving and rotating the billet, the forging marks are arranged in a ring along the billet surface and distributed in parallel along the axis.
[0027] The further technical solution is as follows:
[0028] In step S2: the billet height is positively correlated with the forging pressure; the billet end face inclination angle is positively correlated with the forging pressure; and the billet end face inclination angle is positively correlated with the billet height.
[0029] In step S3: the forging mark distribution density along the billet axis is negatively correlated with the forging mark distribution density on the billet end face; the billet thickness along the billet axis is positively correlated with the forging pressure; the billet axis tilt angle is negatively correlated with the forging pressure; and the billet axis tilt angle is positively correlated with the billet thickness along the billet axis.
[0030] Compared with the prior art, the beneficial technical effects of the present invention are as follows: (1) In the second forging process, the billet undergoes multiple large deformations through multiple forging steps, including drawing, upsetting, and squaring, thereby improving the internal defects of the billet and increasing the pass rate of flaw detection; (2) By placing the billet in the lower V-anvil and drawing it through the forging pressure of the upper flat anvil, the drawing efficiency is high and the billet will not be eccentric; (3) In the sixth forging process, the low temperature forging process makes the internal grain size of the billet smaller and the grain boundaries clearer, thereby improving the strength and hardness of the billet. At the same time, the lower furnace temperature in the sixth forging process makes the deformation performance of the billet better, which can remove internal defects of the billet and reduce material cracks; (4) The forging marks formed in the first deformation improvement process are along the end face of the billet, and forging can also be carried out inside the billet, thereby improving the internal density of the billet structure. However, the forging marks on the end face of the billet cannot form more complex three-dimensional forging inside the billet. Therefore, in the second deformation improvement process, by forging the outer surface of the billet, the forging pressure inside the billet comes from different directions, which improves the density inside the billet and prevents the billet from becoming loose and having bubbles; (5) The relationship between the billet axis tilt angle and the forging pressure is different from the relationship between the billet end face tilt angle and the forging pressure. In the first deformation improvement process, the billet end face forging pressure is only applied to one end face of the billet, while in the second deformation improvement process, the billet axis direction is to forge the four faces of the outer surface of the billet separately. If the forging pressure density is too high, it is easy to cause the billet to break and the billet to have cracks inside. Therefore, when the forging pressure distribution density of the billet end face is relatively sparse, the forging pressure distribution density in the billet axis direction is increased. When the forging pressure distribution density of the billet end face is relatively dense, the forging pressure distribution density in the billet axis direction is reduced. This makes the overall forging pressure distribution of the billet uniform, avoids more forging pressure inside the billet, and thus avoids the billet from breaking and having cracks. Attached Figure Description
[0031] Figure 1 A schematic flowchart of the forging method of the 35CrNi3MoV cylinder of the present invention is shown.
[0032] Figure 2 The diagram shows the distribution of forging marks after upsetting of the billet during the first forging process of the forging method of the 35CrNi3MoV cylinder of the present invention.
[0033] Figure 3 This diagram illustrates the distribution of forging marks after the billet solidifies during the second forging process of the forging method for the 35CrNi3MoV cylinder of this invention. Detailed Implementation
[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the device proposed by this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, only for the purpose of conveniently and clearly illustrating the embodiments of this invention. Please refer to the accompanying drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.
[0035] Figure 1 A schematic flow chart of the forging method for the 35CrNi3MoV cylinder of this invention is shown. (In conjunction with...) Figure 1 As shown, this invention discloses a forging method for a 35CrNi3MoV cylinder.
[0036] The forging method of the 35CrNi3MoV cylinder includes the following steps:
[0037] Step S1: Heating the billet: Heat the billet to 1230℃ and then keep it at that temperature.
[0038] Step S2, First forging: Roll the outer circle of the billet and upset the billet to the specified size.
[0039] Step S3, Second Forging: The billet is drawn into an octagonal shape, then upset and squared.
[0040] Step S4, Third Forging: Flatten the billet into a square shape using the FM method.
[0041] Step S5, Fourth Forging: Upsetting the billet, followed by punching.
[0042] Step S6, Fifth Forging: Insert a mandrel into the billet, then draw it out while leaving some deformation, and then air cool it to the surface temperature of the billet: 350-400℃.
[0043] Step S7, Sixth Forging: The furnace temperature is raised to 350-400℃ and then held. The billet is placed in the furnace and heated to 650℃ and held, then the furnace temperature is raised to 940℃ and held. The billet is then removed from the furnace and finished into a finished product.
[0044] Step S1: Billet heating: Heat the billet to 1230℃ and hold for 5-7 hours.
[0045] In step S1, the billet is heated. After heating, the billet is kept at a relatively long temperature for a long time to make the temperature difference between the inside and outside of the billet uniform, so that the billet has a better dense structure after forging.
[0046] Step S2, First forging: Roll the outer diameter of the billet, rolling amount: 30-50mm, upsetting the billet height to 800mm. Then heat to 1250℃ and hold for 4-6 hours.
[0047] Step S3, Second Forging: The billet is drawn octagonally to 970*1960mm, then upset to 1510*850mm and squared to 1100*1100*1260mm. Then it is heated to 1250℃ and held for 4-6 hours.
[0048] The machining allowance for rolling the outer diameter in the first forging process is relatively small. Rolling the outer diameter and upsetting in the first forging process cause basic deformation of the billet, preparing it for the subsequent second forging process.
[0049] The second forging process involves drawing, upsetting, and squaring in sequence. Through multiple forging steps, the billet undergoes multiple large deformations, which improves the internal defects of the billet and increases the pass rate of flaw detection.
[0050] Step S4, Third Forging: Flatten the billet to 900*700*2400mm using the FM method. Then heat it to 1250℃ and hold it for 2-3 hours.
[0051] By flattening the billet during the third forging process (FM), the holding time of the billet in the subsequent sixth forging process can be reduced.
[0052] Step S5, Fourth Forging: Upset the billet to a height of 800mm, then punch a hole. The hole diameter is Φ550mm. Afterwards, heat to 1250℃ and hold for 4-6 hours.
[0053] The upsetting and punching in the fourth forging process prepares the mandrel for the subsequent fifth forging process.
[0054] Step S6, Fifth Forging: Insert a mandrel with dimensions of Φ525-Φ445*3000mm into the billet, then use a flat anvil on top and a V-anvil on the bottom to draw it out, leaving a deformation allowance of 5-15%. Heat to 1200℃ and hold for 4-6 hours. Then air cool until the billet surface temperature is 350-400℃.
[0055] The billet is drawn by inserting a mandrel through a hole in the billet and then drawing it out using an upper flat anvil and a lower V-anvil, leaving a 5-15% deformation allowance for the finished size. The billet is then air-cooled to 350-400℃.
[0056] During the drawing process, the mandrel is placed inside the hole of the billet. When the forging deviates, the hole in the billet is easily enlarged, causing the billet to become eccentric. By placing the billet in the lower V-anvil and drawing it through the forging pressure of the upper flat anvil, the drawing efficiency is higher, and the billet will not become eccentric.
[0057] Step S7, Sixth Forging: After heating the furnace to 350-400℃, hold the temperature for 4-5 hours. Place the billet in the furnace and heat it to 650℃, then hold it for 3-4 hours. After that, heat the furnace to 940℃ and hold it for 8-10 hours. Remove the billet from the furnace and finish it into a finished product.
[0058] The sixth forging process, involving low-temperature forging, results in finer grain sizes and clearer grain boundaries in the billet, improving its strength and hardness. Simultaneously, the lower furnace temperature in the sixth forging process enhances the billet's deformability, removes internal defects, and reduces material cracking.
[0059] In step S2, the first forging process includes a first deformation improvement process after upsetting the billet:
[0060] The end face of the billet is tilted at a certain angle and forged to form forging marks. By moving and rotating the billet, the forging marks are distributed alternately along the end face of the billet.
[0061] In step S3, the second forging process, after the billet is drawn octagonally, a second deformation improvement process is also included.
[0062] The billet is tilted at a certain angle along the axis, and its surface is forged to form forging marks. By moving and rotating the billet, the forging marks are arranged in a ring shape along the axis of the billet surface.
[0063] In step S2: the billet height is positively correlated with the forging pressure, and the billet end face inclination angle is positively correlated with the forging pressure. The billet end face inclination angle is positively correlated with the billet height.
[0064] In step S3: the length of the billet axis is positively correlated with the forging mark distribution density; the thickness of the billet along the axis is positively correlated with the forging pressure; and the inclination angle of the billet axis is negatively correlated with the forging pressure. The inclination angle of the billet axis is positively correlated with the thickness of the billet along the axis.
[0065] In the first forging process, the billet height after upsetting is 800mm. An inclined forging block is placed on the worktable of the forging equipment. The inclined surface of the forging block forms a first angle with the working surface of the worktable. The size of this first angle is directly proportional to the height of the upset billet. The higher the upset billet, the larger the first angle. The lower the upset billet, the smaller the first angle. A higher upset billet results in greater forging pressure. A lower upset billet results in lower forging pressure. A larger first angle results in greater forging pressure. A smaller first angle results in lower forging pressure.
[0066] When a billet is placed horizontally and forged, the deformation gradually decreases from the outside to the inside, resulting in uneven internal and external microstructure and inconsistent density. To induce deformation, the billet is placed at an angle, creating a forging mark where the angled surface near the forging block intersects with the working surface of the worktable. Deformation occurs both inside and outside the forging mark area. Forging continues, creating new forging marks, with the forging head pressing against the old forging mark area. At this point, the old forging mark area is horizontal, and the deformation from the subsequent forging decreases gradually from the outside to the inside. This pressing of the old forging mark area avoids frequent and repeated forging of the billet's interior, preventing internal cracks.
[0067] To ensure a uniform distribution of forging marks on the billet and improve the uniformity of the metal microstructure at any location on the billet, the billet is moved and rotated during the forging process. This causes the forging marks to be staggered along the end face of the billet, resulting in a uniform distribution of forging marks.
[0068] Figure 2 The diagram shows the distribution of forging marks after upsetting of the billet during the first forging process of the forging method of the 35CrNi3MoV cylinder of the present invention.
[0069] Figure 2 The diagram shows two scenarios: one where forging marks are distributed longitudinally and laterally along the end face of the billet, and another where forging marks are distributed radially along the end face of the billet.
[0070] By first moving the billet, then rotating it by a certain angle, and then moving it again, the forging marks are made to be distributed longitudinally and laterally along the end face of the billet. Alternatively, by rotating the billet along the center of its end face, the forging marks are distributed radially along the end face.
[0071] In the first deformation improvement process, the forging marks formed are along the end face of the billet, allowing for forging within the billet and improving its internal density. However, forging marks on the end face cannot create more complex three-dimensional forging within the billet. Therefore, in the second deformation improvement process, forging marks are applied to the outer surface of the billet, resulting in forging marks within the billet originating from different directions. This enhances the internal density of the billet, preventing porosity and air bubbles from forming inside.
[0072] In the second forging process, the billet, after square forming, has dimensions of 1100*1100*1260mm. At this point, the billet end faces are square. After square forming, the billet end faces are located on both sides of the horizontal direction. When the billet is placed at an angle, a forging mark is formed at the intersection of the inclined surface of the billet near the forging block and the working surface of the worktable. Deformation occurs both inside and outside the location where the forging mark forms. Forging continues, creating new forging marks, with the forging head of the forging equipment pressing against the old forging mark location. At this point, the old forging mark location is horizontal, and the deformation generated by the subsequent forging gradually decreases from the outside in. Pressing against the old forging mark location avoids frequent and repeated forging of the billet's interior, preventing internal cracks from forming.
[0073] A forging block with an inclined angle is placed on the worktable of the forging equipment. A second angle is formed between the inclined surface of the forging block and the working surface of the worktable. The magnitude of the first angle is positively correlated with the thickness of the billet along its axial direction. The greater the thickness of the billet along its axial direction, the larger the first angle. The smaller the thickness of the billet along its axial direction, the smaller the first angle. The magnitude of the first angle is negatively correlated with the forging pressure. The larger the first angle, the smaller the forging pressure. The smaller the first angle, the greater the forging pressure. The greater the thickness of the billet along its axial direction, the greater the forging pressure. The thinner the thickness of the billet along its axial direction, the smaller the forging pressure. The sparser the forging mark distribution density on the billet end face, the denser the forging mark distribution density along the billet axial direction. The denser the forging mark distribution density on the billet end face, the sparser the forging mark distribution density along the billet axial direction.
[0074] Figure 3 This diagram illustrates the distribution of forging marks after the billet solidifies during the second forging process of the forging method for the 35CrNi3MoV cylinder of this invention. Figure 3 The figure shows the distribution of forging marks along the axial direction of the billet.
[0075] The relationship between the billet axis inclination angle and forging pressure differs from that between the billet end face inclination angle and forging pressure. In the first deformation improvement process, the forging pressure on the billet end face only acts on one end face. However, in the second deformation improvement process, the billet axis direction involves forging all four faces of the billet's outer surface. If the forging density is too high, it can easily cause the billet to fracture and develop internal fracture marks. Therefore, when the forging mark distribution density on the billet end face is sparse, the forging mark distribution density along the billet axis should be increased. When the forging mark distribution density on the billet end face is dense, the forging mark distribution density along the billet axis should be decreased. This ensures a uniform forging mark distribution throughout the billet, avoiding excessive internal forging marks and thus preventing billet fracture and fracture marks.
[0076] By forging the four sides of the billet separately, the forging marks on each side are staggered to avoid the forging marks on different sides being on the same plane, thus preventing the billet from breaking during forging.
[0077] The present application is illustrated below through three embodiments:
[0078] Example 1:
[0079] A forging method for a 35CrNi3MoV cylinder includes the following steps:
[0080] Step S1: Billet heating: Heat the billet to 1230℃ and hold for 5 hours.
[0081] Step S2, First forging: Roll the outer circle of the billet, roll the amount of 30mm, and upset the billet height to 800mm; then heat to 1250℃ and hold for 4 hours.
[0082] Step S3, Second Forging: The billet is drawn octagonally to 970*1960mm, then upset to 1510*850mm and squared to 1100*1100*1260mm; then heated to 1250℃ and held for 4 hours.
[0083] Step S4, Third Forging: Flatten the billet to 900*700*2400mm; then heat it to 1250℃ and hold it for 2 hours.
[0084] Step S5, Fourth Forging: Upset the billet to a height of 800mm, then punch a hole with a diameter of Φ550mm; then heat it to 1250℃ and hold it for 4 hours.
[0085] Step S6, Fifth Forging: Insert a mandrel with a size of Φ525*3000mm into the billet, then draw it out with a flat anvil on the top and a V-shaped anvil on the bottom, leaving a 5% deformation allowance; heat to 1200℃ and hold for 4 hours; then air cool to the surface temperature of the billet: 350℃.
[0086] Step S7, Sixth Forging: The furnace temperature is raised to 350℃ and held for 4 hours; the billet is placed in the furnace and heated to 650℃ and held for 3 hours, then the furnace temperature is raised to 940℃ and held for 8 hours. The billet is then removed from the furnace and finished into a finished product.
[0087] Example 2:
[0088] A forging method for a 35CrNi3MoV cylinder includes the following steps:
[0089] Step S1: Billet heating: Heat the billet to 1230℃ and hold for 7 hours.
[0090] Step S2, First forging: Roll the outer circle of the billet, roll the amount of 50mm, and upset the billet height to 800mm; then heat to 1250℃ and hold for 6 hours.
[0091] Step S3, Second Forging: The billet is drawn octagonally to 970*1960mm, then upset to 1510*850mm and squared to 1100*1100*1260mm; then heated to 1250℃ and held for 6 hours.
[0092] Step S4, Third Forging: Flatten the billet to 900*700*2400mm; then heat it to 1250℃ and hold it for 3 hours.
[0093] Step S5, Fourth Forging: Upset the billet to a height of 800mm, then punch a hole with a diameter of Φ550mm; then heat it to 1250℃ and hold it for 6 hours.
[0094] Step S6, Fifth Forging: Insert a mandrel with a size of Φ445*3000mm into the billet, then draw it out with a flat anvil on the top and a V-shaped anvil on the bottom, leaving a 15% deformation allowance; heat to 1200℃ and hold for 6 hours; then air cool to the surface temperature of the billet: 400℃.
[0095] Step S7, Sixth Forging: The furnace temperature is raised to 400℃ and held for 5 hours; the billet is placed in the furnace and heated to 650℃ and held for 4 hours, then the furnace temperature is raised to 940℃ and held for 10 hours. The billet is then removed from the furnace and finished into a finished product.
[0096] Example 3:
[0097] A forging method for a 35CrNi3MoV cylinder includes the following steps:
[0098] Step S1: Billet heating: Heat the billet to 1230℃ and hold for 6 hours.
[0099] Step S2, First forging: Roll the outer circle of the billet, roll the amount of 40mm, and upset the billet to a height of 800mm; then heat to 1250℃ and hold for 5 hours.
[0100] Step S3, Second Forging: The billet is drawn octagonally to 970*1960mm, then upset to 1510*850mm and squared to 1100*1100*1260mm; then heated to 1250℃ and held for 5 hours.
[0101] Step S4, Third Forging: Flatten the billet to 900*700*2400mm; then heat it to 1250℃ and hold it for 2.5h.
[0102] Step S5, Fourth Forging: Upset the billet to a height of 800mm, then punch a hole with a diameter of Φ550mm; then heat it to 1250℃ and hold it for 5 hours.
[0103] Step S6, Fifth Forging: Insert a mandrel with a size of Φ525*3000mm into the billet, then draw it out with a flat anvil on the top and a V-shaped anvil on the bottom, leaving a 10% deformation allowance; heat to 1200℃ and hold for 5 hours; then air cool to the surface temperature of the billet: 370℃.
[0104] Step S7, Sixth Forging: The furnace temperature is raised to 370℃ and held for 4.5 hours; the billet is placed in the furnace and heated to 650℃ and held for 3.5 hours, then the furnace temperature is raised to 940℃ and held for 9 hours. The billet is then removed from the furnace and finished into a finished product.
[0105] Comprehensive mechanical property testing of the finished product:
[0106] The performance parameters of the finished products obtained in Examples 1-3 are shown in Table 1.
[0107]
[0108] Table 1
[0109] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0110] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A forging method for a 35CrNi3MoV cylindrical body, characterized in that: Includes the following steps: Step S1, billet heating: The billet is heated to 1230℃ and then held at that temperature; Step S2, First forging: Roll the outer circle of the billet and upset the billet to the specified size; Step S3, Second Forging: The billet is drawn into an octagonal shape, then upset and squared; Step S4, Third Forging: Flatten the billet into a square shape using the FM method; Step S5, Fourth Forging: Upsetting the billet, followed by punching; Step S6, Fifth Forging: Insert a mandrel into the billet, then draw it out while leaving some deformation, and then air cool it until the surface temperature of the billet is 350-400℃. Step S7, Sixth Forging: The furnace temperature is raised to 350-400℃ and then held; the billet is placed in the furnace and heated to 650℃ and held; then the furnace temperature is raised to 940℃ and held; the billet is taken out of the furnace and finished into a finished product. In step S2, the first forging process includes a first deformation improvement process after upsetting the billet: The end face of the billet is tilted at a certain angle and forged to form forging marks on the end face of the billet; by moving and rotating the billet, the forging marks are distributed in an alternating pattern along the end face of the billet. In step S3, the second forging process, after the billet is drawn octagonally, a second deformation improvement process is also included. The billet is tilted at a certain angle along the axis and its surface is forged to form forging marks. By moving and rotating the billet, the forging marks are arranged in a ring along the billet surface and distributed in parallel along the axis.
2. The forging method of the 35CrNi3MoV cylinder as described in claim 1, characterized in that: Step S1: Billet heating: Heat the billet to 1230℃ and hold for 5-7 hours.
3. The forging method of the 35CrNi3MoV cylinder as described in claim 1, characterized in that: Step S2, First forging: Roll the outer circle of the billet, roll the amount of 30-50mm, and upset the billet height to 800mm; then heat to 1250℃ and hold for 4-6 hours.
4. The forging method of the 35CrNi3MoV cylinder as described in claim 1, characterized in that: Step S3, Second Forging: The billet is drawn octagonally to 970*1960mm, then upset to 1510*850mm and squared to 1100*1100*1260mm; then heated to 1250℃ and held for 4-6 hours.
5. The forging method of the 35CrNi3MoV cylinder as described in claim 1, characterized in that: Step S4, Third Forging: Flatten the billet to 900*700*2400mm; then heat it to 1250℃ and hold it for 2-3 hours.
6. The forging method of the 35CrNi3MoV cylinder as described in claim 1, characterized in that: Step S5, Fourth Forging: Upset the billet to a height of 800mm, then punch a hole with a diameter of Φ550mm; then heat it to 1250℃ and hold it for 4-6 hours.
7. The forging method of the 35CrNi3MoV cylinder as described in claim 1, characterized in that: Step S6, Fifth Forging: Insert a mandrel with dimensions of Φ525-Φ445*3000mm into the billet, then use a flat anvil on the top and a V-anvil on the bottom to draw it out, leaving a deformation allowance of 5-15%; heat to 1200℃ and hold for 4-6 hours; then air cool to the surface temperature of the billet: 350-400℃.
8. The forging method of the 35CrNi3MoV cylinder as described in claim 1, characterized in that: Step S7, Sixth Forging: After heating the furnace to 350-400℃, hold the temperature for 4-5 hours; place the billet in the furnace and heat it to 650℃, then hold it for 3-4 hours, and then heat the furnace to 940℃ and hold it for 8-10 hours. The billet is then removed from the furnace and finished into a finished product.
9. The forging method of the 35CrNi3MoV cylinder as described in claim 1, characterized in that: In step S2: the billet height is positively correlated with the forging pressure; the billet end face inclination angle is positively correlated with the forging pressure; and the billet end face inclination angle is positively correlated with the billet height. In step S3: the forging mark distribution density along the billet axis is negatively correlated with the forging mark distribution density on the billet end face; the billet thickness along the billet axis is positively correlated with the forging pressure; the billet axis tilt angle is negatively correlated with the forging pressure; and the billet axis tilt angle is positively correlated with the billet thickness along the billet axis.