A forging die and a flashless forging method for a valve cover

Abstract

The present application provides a kind of forging die and valve cover flashless forging method, the forging die includes mutually slidingly connected die inner ring and die outer ring, die inner ring has first accommodating cavity suitable for accommodating blank, die outer ring has inner wall surface suitable for accommodating blank and die inner ring, and the inner wall surface is jointly enclosed with the top surface of die inner ring to form second accommodating cavity suitable for accommodating blank, first accommodating cavity is communicated with second accommodating cavity, die outer ring has start forging state that is lifted to first height, and finish forging state that die outer ring bottom surface is flush with die inner ring bottom surface, slidingly connected die inner and outer ring can accommodate blank of different sizes and shapes, die inner ring and die outer ring are switched between start forging state and finish forging state by sliding to complete the forging of blank, and due to the downward movement of die outer ring following blank during forging, the radial deformation generated by blank forging pressure is converted into axial allowance, the generation of flash is reduced, and processing efficiency and processing quality are improved.

Description

Technical Field

[0001] This invention relates to the field of forging technology, specifically to a forging die and a flash-free forging method for valve covers. Background Technology

[0002] Valve covers play a crucial role in hydraulic equipment and mechanical systems, controlling oil flow and enhancing system sealing performance. Due to the complex working environment they operate in, various factors such as pressure resistance, stability, and wear resistance must be considered during production.

[0003] Currently, commonly used manufacturing technologies mainly include die casting, forging, and machining. Among these, forging technology plays an important role in valve cover manufacturing because it can provide higher strength and density, while also ensuring high precision and surface quality.

[0004] In traditional valve cover forging, there is a blanking deviation in the billet, and the actual blank weight is mainly positive to ensure the machining dimensions. During the forging process, the billet gradually fills the inner cavity of the die under the forging hammer. Due to the positive deviation in the billet weight, the excess billet in the inner cavity will form flash under forging. Flash is prone to folding in the subsequent shaping process, thus hindering the shaping of the flange outer circle. At the same time, flash is prone to tool collision during machining, reducing subsequent machining efficiency and greatly increasing machining costs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that existing valve cover forging methods are prone to producing flash during the forging process.

[0006] The present invention provides a forging die, comprising an inner die ring and an outer die ring slidably connected to each other, the inner die ring having a first receiving cavity suitable for receiving a blank, the outer die ring having an inner wall surface suitable for receiving the blank and the inner die ring, and the outer die ring further having a clamping part;

[0007] The inner wall surface and the top surface of the inner ring of the mold together form a second receiving cavity suitable for accommodating the blank. The first receiving cavity is connected to the second receiving cavity. The outer ring of the mold moves along the central axis of the inner ring of the mold under the drive of external force. The outer ring of the mold has an initial forging state in which it is raised to a first height, and a final forging state in which the bottom surface of the outer ring of the mold is flush with the bottom surface of the inner ring of the mold. The outer ring of the mold is switched between the initial forging state and the final forging state.

[0008] Optionally, in the forging die described above, the inner ring of the die includes a first sliding portion and a limiting portion connected to each other. The first sliding portion is parallel to the central axis of the inner ring of the die, and the limiting portion is disposed at one end of the first sliding portion near the bottom surface of the inner ring of the die. The first sliding portion and the limiting portion together constitute the outer wall surface of the inner ring of the die. The inner wall surface of the outer ring of the die includes a second sliding portion and an abutting portion connected to each other. The second sliding portion is parallel to the central axis of the inner ring of the die, and the abutting portion is disposed at one end of the second sliding portion near the bottom surface of the outer ring of the die.

[0009] Optionally, in the forging die described above, the first sliding part and the second sliding part are cylindrical surfaces arranged parallel to each other, and the limiting part and the abutting part are conical surfaces arranged parallel to each other.

[0010] Optionally, in the forging die described above, the outer ring of the die and the inner ring of the die are in a clearance fit.

[0011] Optionally, in the forging die described above, the diameters of the contact portions between the inner and outer rings of the die are nominal diameter - 0.5 mm and nominal diameter + 0.5 mm, respectively.

[0012] The present invention also provides a method for forging a valve cover without flash, which uses the forging die described above and further includes the following steps:

[0013] Billet forming: A metal material is provided, and the metal material is forged into a billet;

[0014] One-time upsetting: The billet is placed into the mold, the clamping mechanism clamps the outer ring of the mold and drives the outer ring of the mold away from the inner ring of the mold to expand the volume of the second receiving cavity, and the billet is upset and flattened into the first forging body;

[0015] Secondary upsetting: The first forging body is placed in the inner ring of the mold, the clamping mechanism clamps the outer ring of the mold, and the outer ring of the mold is driven to approach the inner ring of the mold to fit the top forging surface of the first forging body. The first forging body is upset and flattened until the bottom surface of the outer ring of the mold is flush with the bottom surface of the inner ring of the mold, forming the second forging body.

[0016] Blank forming: The second forging body is removed from the mold and the second forging body is modified to form a valve cover blank.

[0017] Optionally, in the above-mentioned flashless forging method for valve cover, during the first upsetting step, the contact and engagement portion of the first sliding part and the second sliding part is maintained between 15-25mm during the lifting of the outer ring of the die;

[0018] In the secondary upsetting step, the distance between the forging surface of the first forging body and the top of the outer ring of the mold is maintained between 5-10 mm.

[0019] Optionally, the above-described flashless forging method for valve covers further includes, in the billet forming step:

[0020] Heating: The billet is placed in a forging furnace and heated to a first temperature;

[0021] Shaping: The heated billet is taken out of the forging furnace and then rolled into a round bar.

[0022] Optionally, the above-described flashless forging method for valve covers further includes, before the first upsetting step:

[0023] Mold preheating: Preheat the entire mold to a temperature of 250-350℃ for 1.5-2.5 hours.

[0024] Optionally, in the above-described valve cover forging method without flash, the temperature of the second forging body after the secondary upsetting step is the second temperature.

[0025] Optionally, in the above-mentioned flashless forging method for the valve cover, the first temperature range is 1180-1250℃, and the second temperature range is greater than or equal to 850℃.

[0026] Optionally, in the above-mentioned flashless forging method for valve covers, the forging equipment is a 3T forging hammer.

[0027] The technical solution provided by this invention has the following advantages:

[0028] 1. The forging die provided by the present invention includes an inner die ring and an outer die ring that are slidably connected to each other. The inner die ring has a first receiving cavity suitable for receiving a blank, and the outer die ring has an inner wall surface suitable for receiving the blank and the inner die ring. The outer die ring is also provided with a clamping part. The inner wall surface and the top surface of the inner die ring together form a second receiving cavity suitable for receiving a blank. The first receiving cavity and the second receiving cavity are connected. The outer die ring moves along the central axis of the inner die ring under the drive of an external force. The outer die ring has an initial forging state in which it is raised to a first height, and a final forging state in which the bottom surface of the outer die ring is flush with the bottom surface of the inner die ring. The outer die ring is switched between the initial forging state and the final forging state.

[0029] This forging die structure features slidingly connected inner and outer rings that can accommodate blanks of different sizes and shapes. The clamping part of the outer ring is used to hold the blank when it is lifted. The interconnected first and second receiving cavities together hold and shape the blank. The inner and outer rings of the die slide between the initial forging state and the final forging state to complete the forging of the blank. Furthermore, since the outer ring of the die moves downward with the blank during the forging process, the radial deformation of the blank caused by forging pressure is converted into axial allowance, which is beneficial for subsequent processing and shaping, thus improving processing efficiency and quality.

[0030] 2. The valve cover forging method without flash provided by the present invention, using the forging die described above, further includes the following steps:

[0031] Billet forming: A metal material is provided, and the metal material is forged into a billet;

[0032] First upsetting: The billet is placed into the mold, the clamping mechanism clamps the outer ring of the mold and drives the outer ring of the mold away from the inner ring of the mold to expand the volume of the second receiving cavity, and the billet is upset and flattened into the first forging body;

[0033] Secondary upsetting: The first forging body is placed in the inner ring of the mold, the clamping mechanism clamps the outer ring of the mold, and drives the outer ring of the mold to approach the inner ring of the mold to fit the top forging surface of the first forging body. The first forging body is upset and flattened until the bottom surface of the outer ring of the mold is flush with the bottom surface of the inner ring of the mold, forming the second forging body.

[0034] Blank forming: The second forging body is removed from the mold and modified to form the valve cover blank.

[0035] This method for forging valve covers without flash involves a billet forming step. The purpose of this step is to heat the metal material to a suitable temperature using metal forging technology, increasing its plasticity and reducing its deformation resistance. The metal material is then forged into a mold billet. A first upsetting step maintains the billet's flat and regular shape, facilitating subsequent forming processes and expanding the volume of the second receiving cavity to provide space for subsequent billet deformation. A second upsetting step further forges and shapes the first forged body, allowing it to gradually fill the mold's receiving cavity. In the second upsetting step… In the upsetting step, the first forging body gradually moves downward under forging pressure, and the outer ring of the die follows the first forging body downward. When the billet is about to fill the second receiving cavity, the radial deformation of the billet caused by forging pressure is converted into axial allowance, which is beneficial to subsequent machining and shaping, and improves machining efficiency and machining quality. After the second upsetting step, the valve cover blank is formed by shaping and cooling through the blank forming step. Through the shaping in the blank forming stage, the accuracy and surface finish of the valve cover blank can be further improved, making the manufactured valve cover blank more in line with the design requirements. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the overall structure of the forging die provided in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of the inner ring of the mold provided in an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the structure of the outer ring of the mold provided in an embodiment of the present invention;

[0040] Explanation of reference numerals in the attached figures:

[0041] 1-Mold inner ring; 11-First sliding part; 12-Limiting part;

[0042] 2-Outer ring of mold; 21-Clamping part; 22-Second sliding part; 23-Abutting part. Detailed Implementation

[0043] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "linking," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0046] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] Example 1

[0048] like Figures 1 to 3As shown, this embodiment provides a forging die, including an inner die ring 1 and an outer die ring 2 that are slidably connected to each other. The inner die ring 1 has a first receiving cavity suitable for receiving a blank, and the outer die ring 2 has an inner wall surface suitable for receiving the blank and the inner die ring 1. The outer wall surface of the outer die ring 2 is also provided with a clamping part 21.

[0049] The inner wall surface and the top surface of the inner ring 1 of the mold together form a second receiving cavity suitable for accommodating the blank. The first receiving cavity is connected to the second receiving cavity. The outer ring 2 of the mold moves along the central axis of the inner ring 1 of the mold under the drive of external force. The outer ring 2 of the mold has an initial forging state in which it is raised to a first height, and a final forging state in which the bottom surface of the outer ring 2 of the mold is flush with the bottom surface of the inner ring 1 of the mold. The outer ring 2 of the mold is switched between the initial forging state and the final forging state. Specifically, in this embodiment, the slidingly connected inner and outer rings of the mold can adapt to blanks of different sizes and shapes. The clamping part 21 of the outer ring 2 of the mold is used to clamp when the outer ring 2 of the mold is lifted. The first and second accommodating cavities, which are interconnected, jointly accommodate the blank and shape it. The inner ring 1 and the outer ring 2 of the mold slide between the initial forging state and the final forging state to complete the forging of the blank. As the outer ring 2 of the mold moves downward with the blank during the forging process, when the blank is about to fill the second accommodating cavity, the radial deformation of the blank caused by forging is converted into axial allowance, which is beneficial for subsequent processing and shaping, and improves processing efficiency and processing quality.

[0050] The forging die provided in this embodiment includes an inner ring 1 comprising a first sliding portion 11 and a limiting portion 12 connected to each other. The first sliding portion 11 is parallel to the central axis of the inner ring 1, and the limiting portion 12 is located at one end of the first sliding portion 11 near the bottom surface of the inner ring 1. The first sliding portion 11 and the limiting portion 12 together constitute the outer wall surface of the inner ring 1. The inner wall surface of the outer ring 2 includes a second sliding portion 22 and an abutting portion 23 connected to each other. The second sliding portion 22 is parallel to the central axis of the inner ring 1, and the abutting portion 23 is located at one end of the second sliding portion 22 near the bottom surface of the outer ring 2. Specifically, in this embodiment, both the first sliding portion 11 and the second sliding portion 22 are parallel to the central axis of the inner ring 1, and the outer wall surface of the inner ring 1 and the inner wall surface of the outer ring 2 are tightly fitted, which can ensure the coaxiality of the billet during processing and avoid eccentricity of the billet during forging due to errors between the inner and outer rings of the die, thereby affecting the processing quality. The limiting portion 12 is located at one end of the first sliding portion 11 near the bottom surface of the inner ring 1. The abutting part 23 is located at one end of the second sliding part 22 near the bottom surface of the outer ring 2 of the mold. During the forging process, when the outer ring 2 of the mold moves to the final forging state, the two are always in contact and cooperate. The abutting part 23 abuts against the limiting part 12 to maintain the stability of the forging shape and reduce the error of the movement of the outer ring 2 of the mold.

[0051] like Figures 1 to 3As shown, in the forging die provided in this embodiment, the first sliding part 11 and the second sliding part 22 are cylindrical surfaces arranged parallel to each other, and the limiting part 12 and the abutting part 23 are conical surfaces arranged parallel to each other. Specifically, in this embodiment, the first sliding part 11 and the second sliding part 22 are both cylindrical surfaces, and the limiting part 12 and the abutting part 23 are both conical surfaces. The cylindrical and conical surfaces can further improve the coaxiality between the outer ring 2 and the inner ring 1 of the die. At the same time, the limiting part 12 and the abutting part 23 with conical surfaces can improve the stability of the connection between the inner ring 1 and the outer ring 2 of the die in the final forging state, which is beneficial to improving the quality of the forging.

[0052] like Figures 1 to 3 As shown, the forging die provided in this embodiment has an outer ring 2 and an inner ring 1 that are clearance-fitted. Specifically, in this embodiment, the clearance-fitted inner ring 1 and outer ring 2 of the die can act as vents during the forging process, expelling the hot air generated during the forging of the high-temperature billet. This reduces the difficulty of billet forming caused by gas expansion in the first or second cavity of the die, thereby improving processing quality. Timely expulsion of hot air also helps reduce machine energy consumption, thus lowering production costs.

[0053] The forging die provided in this embodiment has a nominal diameter of -0.5 mm and a nominal diameter of +0.5 mm at the contact point between the inner ring 1 and the outer ring 2, respectively.

[0054] Example 2

[0055] This embodiment provides a method for forging a valve cover without flash, which uses the forging die described above and further includes the following steps:

[0056] Billet forming: A metal material is provided, and the metal material is forged into a mold billet;

[0057] First upsetting: The billet is placed into the mold, the clamping mechanism clamps the outer ring 2 of the mold and drives the outer ring 2 of the mold away from the inner ring 1 of the mold to expand the volume of the second receiving cavity, and the billet that is about to be upset and flattened is used as the first forging body;

[0058] Secondary upsetting: The first forging body is placed in the inner ring 1 of the mold, the clamping mechanism clamps the outer ring 2 of the mold, and drives the outer ring 2 of the mold to approach the inner ring 1 of the mold to fit the top forging surface of the first forging body. The first forging body is upset and flattened until the bottom surface of the outer ring 2 of the mold is flush with the bottom surface of the inner ring 1 of the mold, forming the second forging body.

[0059] Blank forming: The second forging body is removed from the mold and modified to form the valve cover blank.

[0060] Specifically, in this embodiment, the billet forming step involves heating the metal material to a suitable temperature through metal forging, thereby increasing its plasticity and reducing its deformation resistance. The metal billet is then forged into a mold blank. The first upsetting step maintains the billet's flatness and regular shape, facilitating subsequent forming processes and expanding the volume of the second receiving cavity to provide space for subsequent billet deformation. The second upsetting step further forges and shapes the first forging body, gradually filling the mold's receiving cavity. During the second upsetting step, the first forging body moves downwards under forging pressure, and the outer ring 2 of the mold follows. When the billet is about to fill the second receiving cavity, the radial deformation caused by forging is converted into axial allowance, which is beneficial for subsequent shaping and improves processing efficiency and quality. After the second upsetting step, the blank forming step shapes and cools to form the valve cover blank. The shaping during the blank forming stage further improves the accuracy and surface finish of the valve cover blank, making the finished blank more in line with design requirements.

[0061] The burr-free forging method for valve covers provided in this embodiment maintains a distance of 15-25mm between the contacting and engaging portions of the first sliding part 11 and the second sliding part 22 during the initial upsetting step of the die outer ring 2; and maintains a distance of 5-10mm between the forging surface of the first forging body and the top of the die outer ring 2 during the secondary upsetting step. Specifically, in this embodiment, maintaining the distance between the contacting and engaging portions of the first sliding part 11 and the second sliding part 22 can prevent the die outer ring 2 from being struck by the forging hammer during the upsetting process, while also ensuring close contact with the upper surface of the first forging body, thus preventing burrs from forming when the billet is about to fill the second receiving cavity.

[0062] The valve cover forging method without flash provided in this embodiment further includes the following in the billet forming step:

[0063] Heating: The billet is placed in the forging furnace and heated to the first temperature;

[0064] Shaping: The heated billet is taken out of the forging furnace and then rolled into a round bar.

[0065] Specifically, in this embodiment, the metal billet is heated to a first temperature, making it soft and easy to process. Forging improves its internal structure and mechanical properties, enhancing its toughness. Simultaneously, heating the billet allows gases to escape, further improving forging quality. Rounding and shaping the billet into a regular cylindrical shape facilitates subsequent forging. Shaping also further improves the surface finish and shape accuracy of the metal billet, preventing forging defects caused by uneven shape.

[0066] The valve cover forging method without flash provided in this embodiment further includes, before the first upsetting step:

[0067] Mold preheating: The entire mold is preheated at a temperature of 250-350℃ for 1.5-2.5 hours. The purpose of preheating the mold is to reduce the deformation resistance caused by the cooling rate of the forging, improve the forming quality and precision of the valve body, and also prevent mold deformation or thermal cracking.

[0068] In the valve cover forging method without flash provided in this embodiment, the temperature of the second forging body after the second upsetting step is the second temperature.

[0069] The flashless forging method for valve covers provided in this embodiment has a first temperature range of 1180-1250℃ and a second temperature range of ≥850℃. Specifically, in this embodiment, the initial forging temperature is set to 1220℃, i.e., the first temperature range is 1180-1250℃. At this temperature, the metal billet becomes flexible and easy to process, and forging can improve its internal structure and improve its mechanical properties and toughness. At the same time, heating the billet can expel the gases, further improving the forging quality. Setting the initial forging temperature avoids deformation or chemical damage caused by overheating. Secondly, the final forging temperature is set, i.e., the second temperature range is ≥850℃. When forming the billet, by controlling the temperature within a suitable range, the metal billet can still maintain stable mechanical properties and toughness under the influence of temperature. The setting of the final forging temperature can ensure the stable quality of the flashless forging of the valve cover.

[0070] The valve cover forging method without flash provided in this embodiment uses a 3T forging hammer. Specifically, in this embodiment, the 3T forging hammer provides sufficient forging force and energy to deeply process and shape the metal billet, forming a high-precision forging. At the same time, the cost of using a 3T forging hammer is relatively low, making it particularly suitable for small and medium-sized factories and forging enterprises.

[0071] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A forging die, characterized in that, Including mutually sliding connections: The inner ring of the mold (1) has a first receiving cavity suitable for receiving the blank; The outer ring (2) of the mold has an inner wall surface suitable for accommodating the blank and the inner ring (1) of the mold, and a clamping part (21) is also provided on the outer wall surface of the outer ring (2); The inner wall surface and the top surface of the inner ring (1) of the mold together form a second receiving cavity suitable for accommodating the blank. The first receiving cavity is connected to the second receiving cavity. The outer ring (2) of the mold moves along the central axis of the inner ring (1) of the mold under the drive of external force. The outer ring (2) of the mold has a forging state raised to a first height and a forging state where the bottom surface of the outer ring (2) is flush with the bottom surface of the inner ring (1) of the mold. The outer ring (2) of the mold is switched between the forging state and the forging state.

2. The forging die according to claim 1, characterized in that, The inner ring of the mold (1) includes a first sliding part (11) and a limiting part (12) connected to each other. The first sliding part (11) is parallel to the central axis of the inner ring of the mold (1). The limiting part (12) is disposed at one end of the first sliding part (11) near the bottom surface of the inner ring of the mold (1). The first sliding part (11) and the limiting part (12) together constitute the outer wall surface of the inner ring of the mold (1). The inner wall surface of the outer ring (2) of the mold includes a second sliding part (22) and an abutting part (23) connected to each other. The second sliding part (22) is parallel to the central axis of the inner ring (1) of the mold, and the abutting part (23) is disposed at one end of the second sliding part (22) near the bottom surface of the outer ring (2) of the mold.

3. The forging die according to claim 2, characterized in that, The first sliding part (11) and the second sliding part (22) are cylindrical surfaces arranged parallel to each other, and the limiting part (12) and the abutting part (23) are conical surfaces arranged parallel to each other.

4. The forging die according to claim 2, characterized in that, The outer ring (2) of the mold and the inner ring (1) of the mold are in clearance fit.

5. The forging die according to claim 2, characterized in that, The diameters of the contact parts between the inner ring (1) and the outer ring (2) of the mold are nominal diameter -0.5mm and nominal diameter +0.5mm, respectively.

6. A method for forging a valve cover without flash, characterized in that, The forging die used according to any one of claims 1-5 further includes the following steps: Billet forming: A metal material is provided, and the metal material is forged into a billet; One-time upsetting: The billet is placed into the mold, the clamping mechanism clamps the outer ring (2) of the mold, and drives the outer ring (2) of the mold away from the inner ring (1) of the mold to expand the volume of the second receiving cavity, and the billet is upset and flattened into the first forging body; Secondary upsetting: The first forging body is placed into the first receiving cavity of the inner ring (1) of the mold, the clamping mechanism clamps the outer ring (2) of the mold, and drives the outer ring (2) of the mold to approach the inner ring (1) of the mold to match the top forging surface of the first forging body. The first forging body is upset and flattened until the outer ring (2) of the mold is flush with the bottom surface of the inner ring (1) of the mold, forming the second forging body; Blank forming: The second forging body is removed from the mold and the second forging body is modified to form a valve cover blank.

7. The method for forging a valve cover without flash according to claim 6, characterized in that, The inner ring (1) of the mold includes a first sliding part (11) and a limiting part (12) that are connected to each other. During the upsetting process, the contact area between the first sliding part (11) and the second sliding part (22) is maintained between 15-25 mm during the lifting of the outer ring of the mold (2). In the secondary upsetting step, the distance between the forging surface of the first forging body and the top of the outer ring (2) of the mold is maintained between 5-10 mm.

8. The method for forging a valve cover without flash according to claim 6, characterized in that, The blank forming step further includes: Heating: The billet is placed in a forging furnace and heated to a first temperature; Shaping: The heated billet is taken out of the forging furnace and then rolled into a round bar.

9. The method for forging a valve cover without flash according to claim 6, characterized in that, Before the first upsetting step, the following is also included: Mold preheating: Preheat the entire mold to a temperature of 250-350℃ for 1.5-2.5 hours.

10. The method for forging a valve cover without flash according to claim 8, characterized in that, After the second upsetting step, the temperature of the second forging body is the second temperature.

11. The method for forging a valve cover without flash according to claim 10, characterized in that, The first temperature range is 1180-1250℃, and the second temperature range is greater than or equal to 850℃.

12. The method for forging a valve cover without flash according to any one of claims 6-11, characterized in that, The forging equipment is a 3T forging hammer.

Images