阅读说明：本技术 三片式法兰球阀阀盖辗扩锻造成形工艺 (Three-piece flange ball valve cover rolling forging forming process ) 是由 周亚夫 吴克成 杨柳 于 2020-10-23 设计创作，主要内容包括：本发明公开了一种三片式法兰球阀阀盖辗扩锻造成形工艺,包括下料、加热及镦粗；制坯及冲连皮；辗扩成形；制坯及冲连皮使坯件中心的锥形深盲孔变成中心通孔；辗扩模中,芯辊穿过坯件的部分由从下到上依次相连的下圆柱段、上大下小的锥形过渡段和上圆柱段组成,主辊部分包括上盖圈,上盖圈下端面凸出隔圈的部分是由下锥面和上锥面组成的双锥面,下锥面与水平面的夹角为5°＜α≤8°,上锥面与水平面的夹角为35°＜β≤42°,坯件的下端面位于下盖圈的锥形面的高度范围内,坯件的上端面位于上盖圈的上锥面的高度范围内。使辗扩成形后的坯件上法兰带有台阶,内孔靠近上法兰的一端带有锥度,从而减少后续机加量,并降低材料成本,提高锻件质量。(The invention discloses a three-piece flange ball valve bonnet rolling forging forming process, which comprises blanking, heating and upsetting; blank making and continuous skin punching; performing ring rolling and shaping; making a blank and punching a connecting skin to change a conical deep blind hole in the center of the blank into a central through hole; in the rolling die, the part of the core roller penetrating through the blank consists of a lower cylindrical section, a conical transition section with a larger upper part and a smaller lower part and an upper cylindrical section which are sequentially connected from bottom to top, the main roller part comprises an upper cover ring, the part of the lower end surface of the upper cover ring protruding out of the spacer ring is a double conical surface consisting of a lower conical surface and an upper conical surface, the included angle between the lower conical surface and the horizontal plane is more than 5 degrees and less than or equal to 8 degrees, the included angle between the upper conical surface and the horizontal plane is more than 35 degrees and less than or equal to 42 degrees, the lower end surface of the blank is positioned in the height range of the conical surface of the lower cover ring, and the upper end surface of the blank. The upper flange of the blank after the rolling forming is provided with a step, and one end of the inner hole close to the upper flange is provided with a taper, so that the subsequent machine dosage is reduced, the material cost is reduced, and the forging quality is improved.)

1. A three-piece type flange ball valve cover rolling forging forming process comprises the following steps:

blanking, heating and upsetting; secondly, blank making and continuous skin punching; (III) rolling and shaping; the method is characterized in that:

in the step (II), the blank after upsetting is placed into a blank making lower die assembly (10), and a conical deep blind hole is punched in the center of the blank through a conical punching punch (11) with a large upper part and a small lower part; the blank is taken out and turned for 180 degrees, then placed into a blank making lower die assembly (10) again, and a skin connecting punch (12) is used for punching off a skin connecting layer, so that a conical deep blind hole in the center of the blank is changed into a central through hole;

in the third step, the blank is placed into a rolling die for rolling and forming;

the rolling and expanding die comprises a main roller part, a core roller (8), an upper cone roller (9) of a hole expanding machine and a lower cone roller (7) of the hole expanding machine, wherein the core roller (8) is used for sleeving a blank, the part of the core roller (8) penetrating through the blank consists of a lower cylindrical section (8a), a conical transition section (8b) with a large upper part and a small lower part and an upper cylindrical section (8c) which are sequentially connected from bottom to top, the upper cone roller (9) of the hole expanding machine and the lower cone roller (7) of the hole expanding machine are respectively arranged on one side of the axis of the core roller (8) and are used for pressing the upper end surface and the lower end surface of the blank, the main roller part is arranged on the other side of the axis of the core roller (8) and is used for expanding the blank by combining with the core roller (8), the main roller part comprises a main roller shaft (1), and a lower cover ring (2), a spacer ring (3), a middle ring (4), a spacer ring (3) and an upper, and is pressed and fixed by a pressing ring (6); the diameter of the lower cover ring (2), the diameter of the middle ring (4) and the diameter of the upper cover ring (5) are larger than the diameter of the spacer ring (3), the parts of the upper end surface of the lower cover ring (2) and the upper end surface of the middle ring (4) which protrude out of the spacer ring (3) are conical surfaces, the part of the lower end surface of the upper cover ring (5) which protrudes out of the spacer ring (3) is a double conical surface consisting of a lower conical surface (5b) and an upper conical surface (5a), the included angle between the lower conical surface (5b) and a horizontal plane is more than 5 degrees and less than or equal to 8 degrees, the included angle between the upper conical surface (5a) and the horizontal plane is more than 35 degrees and less than or equal to 42 degrees, the included angle gamma of the conical transition section (8b) is less than or equal to 64 degrees, the lower end surface of the blank is positioned in the height range of the conical surface of the lower cover ring (2), and;

the blank after the rolling and expanding of the rolling and expanding die is provided with an upper flange, a lower flange and a central through hole, one end of the central through hole close to the upper flange is provided with a taper, and the upper flange is provided with a step.

2. The three-piece flange ball valve cover rolling forging forming process according to claim 1, characterized in that: and (III) placing the blank on a workbench of a hole expanding machine by using a horizontal numerical control band axial rolling hole expanding machine, sleeving a core roller (8) into the inner hole of the blank, rotating the main roller part, moving the core roller (8), an upper cone roller (9) of the hole expanding machine and a lower cone roller (7) of the hole expanding machine to the main roller part simultaneously, moving the upper cone roller (9) of the hole expanding machine downwards to the proper position, gradually expanding the inner hole and the outer circle of the blank under the combined action of the core roller (8) and the main roller part, ensuring that the total height of the blank is ensured by moving the upper cone roller (9) of the hole expanding machine downwards, and returning the upper cone roller (9) of the hole expanding machine, the lower cone roller (7) of the hole expanding machine and the core roller (8) to the original positions after all sizes and shapes of the blank meet requirements, taking out the blank and.

3. The three-piece flange ball valve cover rolling forging forming process according to claim 1 or 2, characterized in that: in the step (I) and the step (II), a three-station double-workbench 2000-ton hydraulic forging press is shared, the blank is placed on a No. 1 workbench at a first station, and the No. 1 workbench moves into a second station for upsetting and descaling; after the blank is clamped, the No. 1 workbench moves to a third station, and the No. 2 workbench moves to a second station and enters a working position; a blank making lower die assembly is arranged on the No. 2 workbench, a blank is placed in the blank making lower die assembly, a punching punch moves to the center of a second station, a conical deep blind hole is punched downwards in the center of the blank, and the punching punch is reset; ejecting the blank, clamping the blank, turning the blank by 180 degrees, putting the blank into a blank-making lower die assembly, moving a continuous skin punch to the central position of a second station, punching off a continuous skin layer downwards, and resetting the continuous skin punch; the No. 2 workbench moves to a third station, a blank is ejected out, and the blank is taken away; and circularly entering upsetting, blank making and continuous punching of the next blank.

4. The three-piece flange ball valve cover rolling forging forming process according to claim 1, characterized in that: in the step (one), blanking is carried out by adopting a band sawing machine according to the specification, the size and the precision required by the blanking process; the heating adopts a regenerative natural gas heating furnace.

Technical Field

The invention relates to the technical field of forging forming processes, in particular to a three-piece type flange ball valve cover rolling forging forming process.

Background

The rolling is a rotary forging method for manufacturing the required ring-shaped piece by gradually enlarging the diameter of the ring-shaped blank in a hole pattern formed by a rolling roller and a core roller and forming the ring-shaped blank, which is also called reaming or rolling.

FIG. 1 is a part diagram of a valve cover of a medium-sized and large-sized three-piece flange ball valve, wherein a flange plate at the upper end of the valve cover is provided with a step, and the upper end of an inner hole is provided with a step hole. Fig. 2 is a blank drawing of a valve cover of a medium-sized and large-sized three-piece flange ball valve with a conventional design after being formed by rolling and forging. The flange plate at the upper end of the valve cover forging rolled by the rolling die has no step and is an integral plane; meanwhile, the inner hole is also a straight hole.

At present, the process of rolling, forging and forming a three-piece flange ball valve cover is shown in fig. 3. Mainly comprises (I) blanking, heating and upsetting; secondly, blank making and continuous skin punching; and (III) a rolling forming process, wherein the inner hole of the blank after blank making and continuous skin punching is a straight hole, the flange plate at the upper end of the rolled blank is a plane, and the inner hole is still the straight hole. The rolling die used in the rolling forming is shown in fig. 4.

The rolling die consists of a main roller part, a core roller 8, an upper cone roller 9 of the broaching machine and a lower cone roller 7 of the broaching machine. The core roller 8 is used for sleeving the blank, and the part of the core roller 8 penetrating through the blank is a cylindrical section. The upper cone roller 9 of the broaching machine and the lower cone roller 7 of the broaching machine are respectively arranged on one side of the axis of the core roller 8 and are used for pressing the upper end surface and the lower end surface of the blank. The main roller part is arranged on the other side of the axis of the core roller 8 and is combined with the core roller 8 for rolling the blank, the main roller part comprises a main roller shaft 1, and a lower cover ring 2, a spacing ring 3, a middle ring 4 and a spacing ring 3 which are sequentially coaxially sleeved on the main roller shaft 1 from bottom to top, and are pressed and fixed through a pressing ring 6; the diameters of the lower cover ring 2, the middle ring 4 and the upper cover ring 5 are larger than the diameter of the spacer ring 3, the parts of the upper end surface of the lower cover ring 2 and the upper end surface of the middle ring 4, which protrude out of the spacer ring 3, are conical surfaces, the lower end surface of the blank is positioned in the height range of the conical surface of the lower cover ring 2, and the upper end surface of the blank is positioned outside the pressing ring 6.

Although the structure of the die is relatively simple, the service life of the rolling die for the valve covers of medium-sized and large-sized three-piece flange ball valves is long, and except for the core rod, the service life of one die is more than 4 thousands of dies, and the height of the die can reach 10 thousands of dies. The service life of the core roller is about 4000, so that the cost difference of the die cost which is spread on each forging blank is very small and can be almost ignored. However, in the forged piece formed by rolling the valve cover of the medium-sized and large-sized three-piece flange ball valve with the conventional design, the flange plate at the upper end has no step, and the end, close to the upper flange plate, of the inner hole has no taper, so that the subsequent machining cost is high, and the material cost of blank blanking is greatly increased.

Disclosure of Invention

The invention aims to provide a forming process suitable for ring rolling forging of a three-piece flange ball valve cover, which can enable an upper flange of a ring-rolled blank to be provided with a step and one end of an inner hole close to the upper flange to be provided with a taper, thereby reducing the subsequent machining amount and lowering the material cost.

Therefore, the technical scheme adopted by the invention is as follows: a three-piece type flange ball valve cover rolling forging forming process comprises the following steps:

blanking, heating and upsetting; secondly, blank making and continuous skin punching; (III) rolling and shaping;

in the step (II), the blank after upsetting is placed into a blank making lower die assembly, and a conical deep blind hole is punched in the center of the blank through a conical punching punch with a large upper part and a small lower part; taking out the blank, turning the blank for 180 degrees, putting the blank into the blank-making lower die assembly again, and punching off the continuous skin layer through the continuous skin punch so as to change the conical deep blind hole in the center of the blank into a central through hole;

in the third step, the blank is placed into a rolling die for rolling and forming;

the rolling and expanding die comprises a main roller part, a core roller, an upper cone roller of a hole expanding machine and a lower cone roller of the hole expanding machine, wherein the core roller is used for sleeving a blank, the part of the core roller, which penetrates through the blank, consists of a lower cylindrical section, a conical transition section with a large upper part and a small lower part and an upper cylindrical section which are sequentially connected from bottom to top; the diameters of the lower cover ring, the middle ring and the upper cover ring are larger than the diameter of the spacer ring, the parts of the upper end surface of the lower cover ring and the upper end surface of the middle ring, which protrude out of the spacer ring, are conical surfaces, the part of the lower end surface of the upper cover ring, which protrudes out of the spacer ring, is a double conical surface consisting of a lower conical surface and an upper conical surface, the included angle between the lower conical surface and the horizontal plane is more than 5 degrees and less than or equal to 8 degrees, the included angle between the upper conical surface and the horizontal plane is more than 35 degrees and less than or equal to 42 degrees, the included angle gamma of the conical transition section is less than or equal to 64 degrees, the lower end surface of the blank is positioned in the height range of the conical;

the blank after the rolling and expanding of the rolling and expanding die is provided with an upper flange, a lower flange and a central through hole, one end of the central through hole close to the upper flange is provided with a taper, and the upper flange is provided with a step.

Preferably, in the step (iii), a horizontal numerical control broaching machine with axial rolling is used, the blank is placed on a workbench of the broaching machine, a core roller is sleeved in an inner hole of the blank, the main roller part rotates, the core roller, an upper conical roller of the broaching machine and a lower conical roller of the broaching machine simultaneously move towards the main roller part, the inner hole and the outer circle of the blank are gradually enlarged under the combined action of the core roller and the main roller part after the upper conical roller of the broaching machine moves downwards to the proper position, the total height of the blank is ensured by the downward movement of the upper conical roller of the broaching machine, and after all sizes and shapes of the blank meet requirements, the upper conical roller of the broaching machine, the lower conical roller of the broaching machine and the core roller return to original positions, and the blank is taken out to finish the rolling and expanding formation.

Preferably, in the step (I) and the step (II), a three-station double-workbench 2000-ton hydraulic forging press is shared, the blank is placed on a workbench No. 1 of a first station, and the workbench No. 1 moves into a second station for upsetting and descaling; after the blank is clamped, the No. 1 workbench moves to a third station, and the No. 2 workbench moves to a second station and enters a working position; a blank making lower die assembly is arranged on the No. 2 workbench, a blank is placed in the blank making lower die assembly, a punching punch moves to the center of a second station, a conical deep blind hole is punched downwards in the center of the blank, and the punching punch is reset; ejecting the blank, clamping the blank, turning the blank by 180 degrees, putting the blank into a blank-making lower die assembly, moving a continuous skin punch to the central position of a second station, punching off a continuous skin layer downwards, and resetting the continuous skin punch; the No. 2 workbench moves to a third station, a blank is ejected out, and the blank is taken away; and circularly entering upsetting, blank making and continuous punching of the next blank.

Preferably, in the step (one), the blanking is performed by a band sawing machine according to the specification, size and precision required by the blanking process; the heating adopts a regenerative natural gas heating furnace.

The invention has the beneficial effects that: the process is mainly characterized in that the upper end flange step of the valve cover and the upper end taper of the inner hole are rolled and formed at one time during hole expansion, and the tapered inner hole is formed in advance during blank making; by adding the upper cover ring with the double conical surfaces in the rolling die and controlling key parameters (including the angle of the double conical surfaces, the structure of the core rod, the height relation between the upper end surface and the lower end surface of the blank and the conical surfaces of the upper cover ring and the lower cover ring and the like) in the rolling process, the process feasibility is high, and the quality of the rolled forging piece is improved. The valve cover has large production quantity, and the optimized process design and the optimized die design greatly reduce the machining amount and the material cost and can bring great economic benefit.

Drawings

Fig. 1 is a part view of a three-piece flange ball valve cover.

Fig. 2 is a diagram of a blank of a conventional three-piece flange ball valve cover formed by rolling forging.

Fig. 3 is a process diagram for rolling, forging and forming a valve cover of a conventional three-piece flange ball valve.

Fig. 4 is a rolling die of a conventional three-piece flange ball valve cover.

Fig. 5 is a diagram of a blank of the three-piece flange ball valve cover formed by rolling and forging.

FIG. 6 is a process diagram for the rolling forging of the valve cover of the three-piece flange ball valve.

FIG. 7 is a blank making die for the rolling forging of the three-piece flange ball valve cover of the invention.

FIG. 8 is a ring rolling die for ring rolling and forging a three-piece flange ball valve cover according to the present invention.

Detailed Description

The invention will be further illustrated by the following examples in conjunction with the accompanying drawings:

the three-piece flange ball valve cover component shown in fig. 1 is typically characterized by an upper flange and a lower flange, wherein the upper flange is provided with a step, and the upper end of an inner hole is provided with a stepped hole. Firstly, a three-piece flange ball valve cover blank as shown in fig. 5 needs to be forged and machined.

The roll-expanding forging forming process adopted by the three-piece flange ball valve cover blank shown in fig. 5 comprises the following steps: blanking, heating and upsetting; secondly, blank making and continuous skin punching; and (III) rolling and shaping, as shown in figure 6. The blank of the valve cover of the three-piece flange ball valve shown in figure 5 is provided with an upper flange, a lower flange and a central through hole, wherein one end of the central through hole close to the upper flange is provided with a taper, and the upper flange is provided with a step.

In the step (I), blanking is carried out by adopting a band sawing machine according to the specification, the size and the precision required by the blanking process. The heating is carried out by adopting a heat accumulating type natural gas heating furnace according to the heating process file strictly, so that the height of the temperature rise, the temperature control, the sectional temperature rise during the stainless steel heating, the heat preservation requirement and the like is consistent with the height of the process file. After heating to the forging temperature, upsetting is performed. But not limited to, a band saw machine, and a circular saw machine may be used. The heating is not limited to the regenerative natural gas heating furnace, and may be an electric heating furnace or the like.

As shown in fig. 7, the blank making and the punching of the integral skin share a set of dies, including a blank making lower die assembly 10, a punching punch 11 and an integral skin punch 12.

In the step (II), the blank after upsetting is placed into a blank making lower die assembly 10, and a conical deep blind hole is punched in the center of the blank through a conical punching punch 11 with a large upper part and a small lower part; the blank is taken out and turned for 180 degrees, then is placed into the blank making lower die assembly 10 again, and the continuous skin layer is punched through the continuous skin punch 12, so that the conical deep blind hole in the center of the blank is changed into a central through hole, and preparation is made for subsequent roll forming.

As shown in fig. 8, the rolling die is mainly composed of a main roll part, a core roll 8, an upper reamer cone roll 9 and a lower reamer cone roll 7. The core roller 8 is used for sleeving the blank, and the part of the core roller 8 penetrating through the blank consists of a lower cylindrical section 8a, a conical transition section 8b with a large upper part and a small lower part and an upper cylindrical section 8c which are sequentially connected from bottom to top. The upper cone roller 9 of the broaching machine and the lower cone roller 7 of the broaching machine are respectively arranged on one side of the axis of the core roller 8 and are used for pressing the upper end surface and the lower end surface of the blank. The main roll part is arranged on the other side of the axis of the core roll 8 and is combined with the core roll 8 to roll the blank. The middle part of the core stick 8 is additionally provided with a step section with taper so as to be matched with the inner hole structure of the blank.

The main roller part mainly comprises a main roller shaft 1, a lower cover ring 2, a space ring 3, a middle ring 4, a space ring 3 and an upper cover ring 5 which are sequentially coaxially sleeved on the main roller shaft 1 from bottom to top, and is pressed and fixed through a pressing ring 6. The diameters of the lower cover ring 2, the middle ring 4 and the upper cover ring 5 are larger than the diameter of the spacer ring 3, and the parts of the upper end surface of the lower cover ring 2 and the upper end surface and the lower end surface of the middle ring 4 which protrude out of the spacer ring 3 are conical surfaces. The part of the lower end surface of the upper cover ring 5, which protrudes out of the space ring 3, is a double conical surface consisting of a lower conical surface 5b and an upper conical surface 5a, the included angle between the lower conical surface 5b and the horizontal plane is more than 5 degrees and less than or equal to 8 degrees, the included angle between the upper conical surface 5a and the horizontal plane is more than 35 degrees and less than or equal to 42 degrees, and the included angle gamma of the conical transition section 8b is less than or equal to 64 degrees. The lower end surface of the blank is located within the height range of the tapered surface of the lower cover ring 2, and the upper end surface of the blank is located within the height range of the upper tapered surface 5a of the upper cover ring 5.

Preferably, the angle α between the lower tapered surface 5b and the horizontal plane is 5 °, and the angle β between the upper tapered surface 5a and the horizontal plane is 42 °. The upper cylindrical section 8c of the core roller 8 extends into the blank by a height of 10mm, and the angle γ of the conical transition section 8b is 40 °. The included angle gamma is determined by the structure of the final product, and the maximum taper angle gamma is less than or equal to 64 degrees according to the result of digital simulation rolling. The upper end surface of the lower cover ring 2 forms an included angle of 3 degrees with the horizontal plane.

The blank after the rolling and expansion of the rolling and expansion die is provided with an upper flange, a lower flange and a central through hole, one end of the central through hole close to the upper flange is provided with a taper, and the upper flange is provided with a step, as shown in figure 5.

In the third step, the blank is placed into a rolling die shown in fig. 8 for rolling and forming.

Preferably, in step (iii), a horizontal numerically controlled broaching machine with axial rolling is used. The blank is placed on a workbench of a hole expanding machine, a core roller 8 is sleeved in an inner hole of the blank, a main roller part rotates, the core roller 8, an upper conical roller 9 of the hole expanding machine and a lower conical roller 7 of the hole expanding machine simultaneously move towards the main roller part, simultaneously, after the upper conical roller 9 of the hole expanding machine moves downwards to a proper position, the inner hole and the outer circle of the blank are gradually expanded under the combined action of the core roller 8 and the main roller part, the total height of the blank is ensured by the downward movement of the upper conical roller 9 of the hole expanding machine, after all sizes and shapes of the blank meet requirements, the upper conical roller 9 of the hole expanding machine, the lower conical roller 7 of the hole expanding machine and the core roller 8 return to original positions, the blank.

Preferably, the three-station double-workbench 2000-ton hydraulic forging press is shared in the step (I) and the step (II). The three stations comprise a first station, a second station and a third station, and the second station is a working station and is positioned in the center of the press. A platform is arranged on the workbench No. 1, and a blank making lower die assembly is arranged on the workbench No. 2.

Placing the blank on a No. 1 workbench at a first station, and moving the No. 1 workbench into a second station for upsetting and descaling; after the blank is clamped, the No. 1 workbench moves to a third station, and the No. 2 workbench moves to a second station and enters a working position; a blank making lower die assembly is arranged on the No. 2 workbench, a blank is placed in the blank making lower die assembly, a punching punch moves to the center of a second station, a conical deep blind hole is punched downwards in the center of the blank, and the punching punch is reset; ejecting the blank, clamping the blank, turning the blank by 180 degrees, putting the blank into a blank-making lower die assembly, moving a continuous skin punch to the central position of a second station, punching off a continuous skin layer downwards, and resetting the continuous skin punch; the No. 2 workbench moves to a third station, a blank is ejected out, and the blank is taken away; and circularly entering upsetting, blank making and continuous punching of the next blank.

After the rolling and expanding formation, before machining, blank inspection, heat treatment (tempering, and solution treatment for stainless steel materials), comprehensive inspection, and warehousing for transfer are required to be performed, which is not described herein again, and the method only explains the core important steps.

Compared with the traditional process method, the process method has the advantages that due to the change of the die, the blanking weight of the blank after the improved design is 406Kg, the blanking weight of the blank after the conventional design is 438.4Kg, the weight of the material after the optimized design is reduced by 32.4Kg, and the material is saved by 7.4 percent, so that the process method is very considerable.

The key points of the design of the rolling and expanding die are as follows:

(1) the design of the upper cover ring of the ring rolling die is very important, the design of the double conical surfaces at the lower end of the upper cover ring is critical, and the perfect forming of the steps on the upper flange plate of the valve cover forging is related, so that the defect of forging (ring rolling) is avoided. When the included angle beta between the upper conical surface 5a and the horizontal plane is larger than 42 degrees, the deformation acting force of the upper cover ring on the blank is too large, upward axial burrs are generated at the contact position of the upper end of the blank and the upper cover ring, and then the burrs are rolled on the upper end surface through the rolling action of the upper conical roller 9 of the hole expanding machine to form an interlayer. The angle is therefore designed to be 42 ° or slightly less than 42 °. This structure has an additional advantage: the height requirement on the blank is wide, and the blank can be placed in the vertical height range of the angle of the height dimension of the workbench of the hole expanding machine, so that the operation and control capability of the height control of the blank during blank manufacturing is reduced, and the precision control requirement of equipment and the requirement of the technical level of workers are reduced. When the included angle between the lower conical surface 5B of the upper cover ring 5 and the horizontal plane is alpha less than 5 degrees, the position of the beta angle is firstly contacted with the blank, the metal of the blank flows along the direction of the angle B, the metal cannot be contacted with the conical surface of the alpha angle in the upper cover ring in the early stage, and a circle of annular groove is generated at the position during final forming, so that the forging (rolling) defect is formed. Therefore, α in the upper cover ring needs to be designed to be 5 ° or more.

(2) The design of the core rod 8 is also important, the key point is that a position corresponding to the upper end of the upper taper hole of the inner hole of the blank, namely, a small section of the upper cylindrical section 8c is required to extend into the workpiece to form a straight hole, and the straight hole has a very short size, but plays a very large role in the rolling and expanding stability in the rolling and expanding forming process. Because of the taper of the inner hole, the blank generates an axial force in the rolling process, and in the actual production process, because the main roller part of the rolling die and the contact surface between the core rod and the blank are very small during rolling, the blank can generate axial runout under the action of the axial force, thereby causing the generation of forging (rolling) defects. When the core rod is designed, the adverse factors need to be fully considered, so that a section of straight hole is formed in an inner hole at the upper end of the blank in the forming process, and the straight hole part is only acted by radial force, thereby effectively restraining the blank from jumping in the rolling process and avoiding the forging (rolling) defect caused by the blank jumping.