Nail-shaped forge piece forming method

Abstract

The invention relates to the field of forging technologies of large forgings, and discloses a nail-shaped forge piece forming method which comprises the following steps that S1, a machined metal bar is selected, S2, a detachable shell cover is assembled on a basic mold, the shell cover and the basic mold are coaxially positioned through a concave-convex positioning ring, S3, a shell cover pipeline communicates with an upper cavity of the basic mold, and S4, the shell cover pipeline communicates with a lower cavity of the basic mold. S4, the bar is inserted into a shell cover pipeline, and the lower end of the bar extends into the upper cavity; S5, the bar is downwards extruded by the output end of a hydraulic cylinder of a press; and S6, the protruding part, formed due to material overflowing, of the surface of the forge piece is machined. Coaxial positioning is achieved through the concave-convex positioning ring, a stable guide structure is provided for a bar, and the bar is inserted into and extends to the upper cavity of the die along the shell cover pipeline, so that the bar can be evenly stressed when bearing the pressure of a hydraulic cylinder of a press, the bending phenomenon caused by uneven stress is avoided to a great extent, and the production efficiency is improved. And the precision and quality of forge piece forming are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of forging processes for large forgings, and particularly to a forming method for a nail-shaped forging. Background Art

[0002] The nail-shaped forging includes a horizontal section and a vertical section. The horizontal section is 600 mm long and 100 mm high, and the vertical section is 200 mm long and 200 mm high. The existing forming process for the nail-shaped forging is as follows: a bar stock with a diameter of 200 mm, a relatively long length, and a relatively small diameter is selected and placed into the forming groove of the forming die.

[0003] The width dimension of the forming groove is exactly adapted to the diameter of the bar stock, and the depth of the forming groove is only 200 mm. The press presses the bar stock from top to bottom. During the pressing process, the bar stock is used to fill the upper chamber on the forming die to form the horizontal section structure of the nail-shaped forging. However, during the pressing and forming process, since the bar stock is relatively slender, it is very easy for the bar stock to bend under pressure, which is not conducive to the stability of the forming process. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a forming method for a nail-shaped forging, which solves the problem that the bar stock bends under pressure and is not conducive to the stability of the forming process.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: a forming method for a nail-shaped forging, including the following steps: S1: Select a processed metal bar stock; S2: Assemble a detachable shell cover on the basic die, and the shell cover is coaxially positioned with the basic die through a concave-convex positioning ring; S3: Connect the shell cover pipeline with the upper chamber of the basic die; S4: Insert the bar stock into the shell cover pipeline and make its lower end extend into the upper chamber; S5: The output end of the press hydraulic cylinder presses the bar stock downward, so that the metal material fills the forming groove. Then, the press controls the hydraulic cylinder to pressurize, so that the output end of the hydraulic cylinder continues to press the bar stock to make the metal material fill the upper chamber, forming a nail-shaped forging with a horizontal section and a vertical section; S6: Perform machining treatment on the raised part formed on the surface of the forging due to material overflow.

[0006] Preferably, in step S2, the concave-convex positioning ring includes: A ring-shaped boss provided at the bottom of the detachable shell cover, and a ring-shaped groove correspondingly provided at the top of the basic die. The fitting clearance between the boss and the groove is 0.05 - 0.1 mm, and three groups of positioning pins are circumferentially and uniformly arranged to limit the radial displacement.

[0007] Preferably, the extrusion process in step S5 is divided into two stages: The first stage: The upper die and the detachable shell cover are advanced at a speed of 5 - 8 mm / s until the forming groove is completely filled; The second stage: The output end of the hydraulic cylinder is advanced at a speed of 2 - 4 mm / s until the upper chamber is filled, and the pressure is maintained for 10 - 15 seconds after filling.

[0008] Preferably, during the extrusion process in the second stage, when it is detected that the extrusion pressure reaches 800 - 1000 kN, the pressure - maintaining program is automatically triggered to increase the output pressure of the hydraulic cylinder to 120% - 150% of the rated value.

[0009] Preferably, before the operation of step S5, the bar stock is subjected to gradient heating treatment: The area corresponding to the forming groove is heated to 950 ± 20 °C, and the area corresponding to the upper chamber is heated to 850 ± 20 °C. The heating gradient is realized by zonal control of the induction coil, and the temperature error ≤ ±10 °C.

[0010] Preferably, the upper chamber is opened at the center position of the top of the basic die, and a forming groove is also opened on the basic die. The upper chamber and the forming groove communicate with each other; The detachable shell cover is coaxially connected to the basic die through a concave - convex positioning ring. Two slot holes are opened on both the upper die and the detachable shell cover. Both of the two slot holes are shell cover pipes and communicate with each other.

[0011] Preferably, the height of the annular boss of the concave - convex positioning ring is 20 - 25 mm, and its surface is provided with a tungsten carbide wear - resistant coating. The coating thickness is 10 - 15 μm, and the hardness ≥ HV1500.

[0012] Preferably, a composite coating is provided on the inner diameter surfaces of the upper chamber and the forming groove and the bottom of the upper die. The composite coating is composed of alternately deposited TiN layers and MoS2 layers, with a total thickness of 15 - 20 μm, a friction coefficient ≤ 0.15, and a temperature - resistant performance ≥ 1000 °C.

[0013] Preferably, in step S6, when machining the formed convex part, a diamond - coated carbide milling cutter is selected as the machining tool. The tool diameter is 6 - 10 mm, the milling speed is set at 8000 - 12000 r / min, the feed speed is 500 - 800 mm / min, the milling depth is controlled within 0.1 - 0.3 mm, and the surface roughness Ra ≤ 0.8 μm.

[0014] Preferably, after the machining treatment in step S6, the forging is subjected to aging treatment. The aging temperature is controlled at 180 - 220 °C, and the aging time is 6 - 8 hours to eliminate the internal residual stress of the forging and improve the dimensional stability and mechanical properties of the forging.

[0015] The present invention provides a method for forming a nail-shaped forging. It has the following beneficial effects: 1. In the present invention, a detachable shell cover is assembled on the basic mold, and coaxial positioning is achieved by using concave-convex positioning rings, providing a stable guiding structure for the bar stock. During the extrusion process, the bar stock is inserted along the shell cover pipeline and extends to the upper chamber of the mold, realizing precise positioning and guiding. When the bar stock bears the pressure of the press hydraulic cylinder, it can be evenly stressed, greatly avoiding the bending phenomenon caused by uneven stress, and ensuring the accuracy and quality of the forging forming.

[0016] 2. In the present invention, the shell cover pipeline adopts a cylindrical hole structure that is the same up and down, allowing the selection of bar stock with a diameter slightly larger than the forming groove. Through the metal flow compensation of dimensional differences during the extrusion process and in combination with the gradient heating technology, the plasticity adaptability of the material is enhanced, enabling the compatibility of bar stock with different alloy compositions. The most suitable bar stock can be selected according to different production requirements and material characteristics, improving the product performance.

[0017] 3. In the present invention, through staged extrusion control and pressure feedback mechanism, insufficient material filling or over-compression is avoided. The gradient heating technology combined with the composite coating significantly reduces the forming resistance and die wear, ensuring the uniformity of the internal structure of the forging. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a step flow chart of a method for forming a nail-shaped forging according to the present invention; Figure 2 is a three-dimensional schematic diagram of a method for forming a nail-shaped forging according to the present invention; Figure 3 is an unfolded schematic diagram of the basic mold and the detachable shell cover of a method for forming a nail-shaped forging according to the present invention; Figure 4 is a cross-sectional schematic diagram of the basic mold of a method for forming a nail-shaped forging according to the present invention; Figure 5 is an exploded cross-sectional schematic diagram of the basic mold of a method for forming a nail-shaped forging according to the present invention.

[0019] Among them, 1. Basic mold; 2. Upper mold; 3. Detachable shell cover; 4. Hydraulic cylinder; 5. Upper chamber; 6. Forming groove; 7. Shell cover pipeline; 8. Concave-convex positioning ring. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] Please refer to the attached Figure 1 - attachment Figure 5 , an embodiment of the present invention provides a method for forming a nail-shaped forging, including the following steps: S1: Select the processed metal bar stock; S2: Assemble the detachable shell cover 3 on the basic mold 1, and the shell cover 3 is coaxially positioned with the basic mold 1 through the concave-convex positioning ring 8; The design of the concave-convex positioning ring 8 enables the shell cover 3 to have a high coaxial positioning accuracy with the basic mold 1. The clearance between the annular boss and the annular groove is small, only 0.05 - 0.1 mm, ensuring the accurate relative position of the two, restricting the radial swing. Three groups of positioning pins evenly distributed in the circumferential direction further enhance the stability, preventing the shell cover 3 from displacing during the extrusion process. By using the tight fit and multi-point positioning, the overall structure of the mold is ensured to be stable, enabling the bar stock to be uniformly stressed during extrusion, thereby improving the forming accuracy of the forging.

[0022] S3: Connect the shell cover pipeline 7 with the upper chamber 5 of the basic mold 1; The connection between the shell cover pipeline 7 and the upper chamber 5 provides a channel for the flow of the metal material. During the extrusion process, the metal material flows from the position of the bar stock to the designated area through this channel, ensuring that the material can smoothly fill the upper chamber 5 and guaranteeing the complete forming of the forging. It is similar to a "transport pipeline", guiding the material to flow along the designed path, avoiding material accumulation or uneven filling, and ensuring that the density and shape of each part of the forging meet the requirements.

[0023] S4: Insert the bar stock into the shell cover pipeline 7 and make its lower end extend into the upper chamber 5; Inserting the bar stock into the shell cover pipeline 7 and extending it into the upper chamber 5 positions the bar stock at the predetermined extrusion position. The shell cover pipeline 7 guides the bar stock, ensuring the accurate position of the bar stock before the start of extrusion. Extending into the upper chamber 5 prepares for subsequent extrusion filling, enabling the metal material to smoothly enter the upper chamber 5 and the forming groove 6 from the bar stock, ensuring the accuracy of the extrusion starting position and providing a basis for subsequent precise forming.

[0024] S5: The output end of the press hydraulic cylinder 4 squeezes the bar stock downward, filling the forming groove 6 with the metal material. Then, the press controls the hydraulic cylinder 4 to pressurize, so that the output end of the hydraulic cylinder 4 continues to squeeze the bar stock to fill the upper chamber 5 with the metal material, forming a nail-shaped forging with a horizontal section and a vertical section; The extrusion process is divided into two stages. In the first stage, the upper die 2 and the detachable shell cover 3 are advanced at a speed of 5 - 8 mm / s to quickly fill the forming groove 6. This speed can ensure the rapid flow and filling of the material while avoiding uneven material distribution caused by too fast a speed. In the second stage, the output end of the hydraulic cylinder 4 is advanced at a speed of 2 - 4 mm / s to fill the upper chamber 5. The slower speed is beneficial for the material to fully fill the complex structure, reduce internal defects, and hold the pressure for 10 - 15 seconds to allow the material to be fully densified under pressure and eliminate internal voids. When the extrusion pressure reaches 800 - 1000 kN, the pressure holding program is triggered and the pressure is increased. At this time, the material is close to being dense, and increasing the pressure can further improve the density and strength of the forging.

[0025] S6: Machine-process the raised parts formed by material overflow on the surface of the forging.

[0026] Select a diamond-coated cemented carbide milling cutter. Because of its high hardness and good wear resistance, it can efficiently machine metal materials. The parameter combination of a tool diameter of 6 - 10 mm, a milling speed of 8000 - 12000 r / min, a feed speed of 500 - 800 mm / min, and a milling depth of 0.1 - 0.3 mm ensures that while removing the raised parts, the requirement of a surface roughness Ra ≤ 0.8 μm is met, making the surface of the forging smooth and meeting the use standards, and avoiding affecting the assembly or use performance due to surface protrusions.

[0027] Please refer to the appendix Figure 1 and the appendix Figure 2 , in step S2, the concave-convex positioning ring 8 includes: A ring-shaped boss provided at the bottom of the detachable shell cover 3 and a corresponding ring-shaped groove provided at the top of the basic die 1. The fitting clearance between the boss and the groove is 0.05 - 0.1 mm, and three groups of positioning pins are circumferentially evenly distributed to limit the radial displacement.

[0028] Please refer to the appendix Figure 1 and the appendix Figure 5 , the extrusion process in step S5 is divided into two stages: The first stage: The upper die 2 and the detachable shell cover 3 are advanced at a speed of 5 - 8 mm / s until the forming groove 6 is completely filled; The second stage: The output end of the hydraulic cylinder 4 is advanced at a speed of 2 - 4 mm / s until the upper chamber 5 is filled, and the pressure is held for 10 - 15 seconds after filling.

[0029] Please refer to the appendix Figure 1, gradient heating treatment, different temperatures are set according to the different structural and material filling requirements of the forming groove 6 and the upper chamber 5. The temperature of the area corresponding to the forming groove 6 is relatively high, making the plasticity of the metal material in this area better and facilitating the filling of the forming groove 6. The temperature of the area corresponding to the upper chamber 5 is slightly lower to ensure that the material has a certain rigidity during the filling process and avoid excessive flow. The induction coil is controlled in zones to achieve zone heating, and different amounts of heat are generated in different areas of the metal through electromagnetic induction, thereby improving the forming quality of the forging and reducing defects caused by uneven temperature. Please refer to the appendix Figure 1 , during the second stage of the extrusion process, when it is detected that the extrusion pressure reaches 800 - 1000 kN, the pressure holding program is automatically triggered, and the output pressure of the hydraulic cylinder 4 is increased to 120% - 150% of the rated value.

[0030] In the second stage of forging forming, when the extrusion pressure reaches the range of 800 - 1000 kN, it means that the internal structure of the forging gradually becomes dense and the voids between materials decrease. At this time, the pressure holding program is automatically triggered and the pressure is increased, which can further compact the metal material, fill the microvoids, enhance the bonding force between particles inside the forging, and increase the pressure to 120% - 150% of the rated value, which can further improve the density of the forging, thereby significantly enhancing the strength and toughness of the forging and meeting the requirements for high performance of the forging. Based on the material compaction principle, the micro-structure of the forging is changed through pressure variation to improve the overall performance.

[0031] Please refer to the appendix Figure 1 , before the operation of step S5, gradient heating treatment is performed on the bar stock: The area corresponding to the forming groove 6 is heated to 950 ± 20 °C, and the area corresponding to the upper chamber 5 is heated to 850 ± 20 °C. The heating gradient is achieved through the zonal control of the induction coil, and the temperature error ≤ ±10 °C.

[0032] The gradient heating treatment is based on the forming requirements of different areas. The temperature of the area of the forming groove 6 is relatively high, which is 950 ± 20 °C. At this temperature, the plasticity of the metal material is enhanced and the fluidity is improved, which is beneficial to filling the complex shape structure of the forming groove 6. The temperature of 850 ± 20 °C in the area of the upper chamber 5 can not only ensure that the material has sufficient fluidity to fill this area, but also prevent excessive deformation of the material due to too high temperature. The zonal control of the induction coil precisely realizes the required temperature for each area by adjusting the electromagnetic induction intensity of different areas, and controls the temperature error within ≤ ±10 °C, ensuring that the tissue properties of each part of the forging are uniform, improving the quality stability of the forging, and improving the overall quality of the forging. Please refer to the appendix Figure 4 And the appendix Figure 5 , the upper chamber 5 is opened at the central position on the top of the basic die 1, and the forming groove 6 is also opened on the basic die 1. The upper chamber 5 and the forming groove 6 communicate with each other; The detachable housing 2 is coaxially connected to the base mold 1 through the concave-convex positioning ring 8. Two slot holes are provided on both the upper mold 2 and the detachable housing 3. Both of the two slot holes are housing pipes 7 and are mutually penetrated.

[0033] The upper cavity 5 and the forming groove 6 are designed in terms of the opening position and mutual penetration to conform to the structure of the nail-shaped forging, which is convenient for the metal material to be naturally filled to form the required shape during extrusion. The detachable housing 2 is coaxially connected to the base mold 1 through the concave-convex positioning ring 8 to ensure the coaxiality of the entire mold system and make the extrusion path of the bar stock accurate. The housing pipes 7 on the upper mold 2 and the detachable housing 3 are mutually penetrated, providing a continuous channel for the material flow, ensuring the smooth transfer of the material in each part, and guaranteeing the integrity of the forging forming.

[0034] Please refer to the appendix Figure 2 For the concave-convex positioning ring 8, the height of the annular boss is 20 - 25 mm, and its surface is provided with a tungsten carbide wear-resistant coating. The coating thickness is 10 - 15 μm, and the hardness ≥ HV1500.

[0035] The height of the annular boss is 20 - 25 mm, providing sufficient positioning depth and enhancing the positioning stability. The surface tungsten carbide wear-resistant coating can effectively reduce the wear of the boss during multiple opening and closing of the mold and the extrusion process, extend the service life of the mold. The principle of the wear-resistant coating is that tungsten carbide itself has high hardness and wear resistance, which can resist friction loss and ensure that the concave-convex positioning ring 8 maintains high-precision positioning performance for a long time.

[0036] Please refer to the appendix Figure 1 For the upper cavity 5 and the inner diameter surface of the forming groove 6 and the bottom of the upper mold 2, a composite coating is provided. The composite coating is composed of alternately deposited TiN layers and MoS2 layers, with a total thickness of 15 - 20 μm, a friction coefficient ≤ 0.15, and a temperature resistance performance ≥ 1000 °C.

[0037] TiN is titanium nitride, and MoS2 is molybdenum disulfide. In the composite coating, the TiN layer has high hardness and can improve the wear resistance of the mold surface. The MoS2 layer has a low friction coefficient and can reduce the friction force between the metal material and the mold surface. The two are alternately deposited to form a coating with a total thickness of 15 - 20 μm. Under the condition of a temperature resistance performance ≥ 1000 °C, it can not only ensure the smoothness of the mold surface and make the material flow smoothly, but also prevent the mold from affecting the dimensional accuracy and surface quality of the forging due to wear, extend the service life of the mold, and reduce the production cost.

[0038] Please refer to the appendix Figure 1 For step S6, when machining the formed raised part, a diamond-coated cemented carbide milling cutter is selected as the machining tool. The tool diameter is 6 - 10 mm, the milling speed is set at 8000 - 12000 r / min, the feed rate is 500 - 800 mm / min, the milling depth is controlled within 0.1 - 0.3 mm, and the surface roughness Ra ≤ 0.8 μm.

[0039] Please refer to the appendix Figure 1 After the machining process in step S6, the forging is subjected to aging treatment. The aging temperature is controlled at 180 - 220 °C, and the aging time is 6 - 8 hours to eliminate the internal residual stress of the forging and improve the dimensional stability and mechanical properties of the forging.

[0040] Performing aging treatment at 180 - 220 °C for 6 - 8 hours can cause changes in the internal microstructure of the forging. Within this temperature and time range, metal atoms obtain sufficient energy for diffusion and rearrangement, thereby eliminating the internal residual stress. The elimination of residual stress can effectively prevent the forging from deforming due to stress release during subsequent use, improving dimensional stability. At the same time, the optimization of the microstructure can also enhance the mechanical properties of the forging, increasing strength and toughness, enabling the forging to better withstand external forces in practical applications.

[0041] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for forming a nail-shaped forging, characterized in that: The following steps are involved: S1: Select the processed metal bar; S2: Assembling a detachable shell cover (3) on the basic mold (1), wherein the shell cover (3) is coaxially positioned with the basic mold (1) via a concave and convex positioning ring (8); S3: connecting the shell cover pipe (7) to the upper chamber (5) of the base mold (1); S4: inserting the rod into the housing pipe (7) and extending the lower end of the rod into the upper chamber (5); S5: the output end of the press hydraulic cylinder (4) squeezes the bar material downward so that the metal material fills the forming groove (6), and then the press controls the hydraulic cylinder (4) to increase the pressure so that the output end of the hydraulic cylinder (4) continues to squeeze the bar material so that the metal material fills the upper chamber (5), forming a nail-shaped forging having horizontal and vertical sections; S6: Machining the raised parts on the forging surface formed by material overflow.

2. A nail-shaped forging forming method according to claim 1, characterized in that: In step S2, the concave-convex positioning ring (8) comprises: An annular boss is arranged at the bottom of the detachable shell cover (3), and an annular groove is correspondingly arranged at the top of the basic mold (1), the matching clearance between the boss and the groove is 0.05-0.1mm, and three groups of positioning pins are evenly distributed in the circumferential direction to limit radial displacement.

3. A nail-shaped forging forming method according to claim 1, characterized in that: The extrusion process of step S5 is divided into two stages: First stage: the upper mold (2) and the removable shell cover (3) are advanced at a speed of 5-8 mm / s until the molding groove (6) is completely filled; The second stage: the output end of the hydraulic cylinder (4) is pushed forward at a speed of 2-4 mm / s until the upper chamber (5) is filled, and the pressure is maintained for 10-15 seconds after the filling is completed.

4. A nail-shaped forging forming method according to claim 3, characterized in that: During the second stage of extrusion, when it is detected that the extrusion force reaches 800-1000 kN, the pressure holding program is automatically triggered, so that the output pressure of the hydraulic cylinder (4) is increased to 120%-150% of the rated value.

5. A nail-shaped forging forming method according to claim 1, characterized in that: Before the step S5, the bar material is subjected to a gradient heating treatment: The corresponding area of ​​the molding groove (6) is heated to 950±20°C, and the corresponding area of ​​the upper chamber (5) is heated to 850±20°C. The heating gradient is achieved by zoning control of the induction coil, and the temperature error is ≤±10°C.

6. A nail-shaped forging forming method according to claim 1, characterized in that: The upper chamber (5) is opened at the center of the top of the basic mold (1), and a molding groove (6) is also opened on the basic mold (1), and the upper chamber (5) and the molding groove (6) are interconnected; The detachable shell cover (2) is coaxially connected to the base mold (1) via a concave-convex positioning ring (8), and two slots are provided on the upper mold (2) and the detachable shell cover (3), and the two slots are shell cover pipes (7) and are interconnected.

7. A nail-shaped forging forming method according to claim 1, characterized in that: The annular boss of the concave-convex positioning ring (8) has a height of 20-25 mm and a tungsten carbide wear-resistant coating on its surface with a coating thickness of 10-15 μm and a hardness of ≥ HV1500.

8. A nail-shaped forging forming method according to claim 1, characterized in that: The inner diameter surfaces of the upper chamber (5) and the molding groove (6) and the bottom of the upper mold (2) are all provided with a composite coating, wherein the composite coating is composed of TiN layers and MoS2 layers deposited alternately, has a total thickness of 15-20 μm, a friction coefficient of ≤0.15, and a temperature resistance of ≥1000°C.

9. A nail-shaped forging forming method according to claim 1, characterized in that: In step S6, when machining the formed raised portion, a diamond coated carbide milling cutter is selected as the machining tool, the tool diameter is 6-10 mm, the milling speed is set to 8000-12000 r / min, the feed speed is 500-800 mm / min, the milling depth is controlled at 0.1-0.3 mm, and the surface roughness Ra≤0.8 μm.

10. A nail-shaped forging forming method according to claim 1, characterized in that: After the machining treatment in step S6, the forging is subjected to aging treatment, the aging temperature is controlled at 180-220° C., and the aging time is 6-8 hours.

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