Method for improving the life of a hot forging die and hot forging die

Abstract

The application discloses a method for prolonging the service life of a hot forging die and the hot forging die, wherein a plurality of micro concaves are uniformly distributed on the convex corner and the flash surface of the forging die cavity which needs to be strengthened, and the recess corner part of the forging die cavity which needs to be strengthened is reserved with a machining allowance for extrusion, so that the residual compressive stress of the deformation part of the forging die cavity is improved, work hardening occurs, the hardness and the strength are improved, mechanical cracking is prevented, the micro concaves can accommodate lubricants (such as graphite), the graphite is prevented from being extruded away when the blank flows on the die surface, and the newly generated surface is prevented from directly contacting the die surface. Meanwhile, the micro concaves can also accommodate abrasive grains, and the abrasive grain wear of the surface of the forging die cavity is reduced. It can be seen that the method can prolong the service life of the hot forging die and is simple and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of mold technology, specifically relating to a method for improving the life of hot forging dies and the hot forging die itself. Background Technology

[0002] Currently, there are two main methods for improving the lifespan of hot forging dies: surface coating and surface modification. Typical surface coating methods include PVD and CVD. PVD and CVD coatings can effectively reduce wear-induced damage and improve the wear resistance of the substrate. However, coatings prepared by traditional PVD and CVD methods are prone to peeling off during use due to differences in thermal expansion coefficients and thermal conductivity with the substrate, making them unsuitable for hot forging dies. Surface modification involves using chemical or physical methods to alter the chemical composition or structure of the material surface, thereby improving material properties. Nitriding is a commonly used surface modification technique for improving the lifespan of hot forging dies. Through nitriding, a harder, wear-resistant nitride layer can be formed on the material surface. Studies have shown that a uniform nitride layer structure can effectively improve the lifespan of hot forging dies. However, completing the nitriding process on hot forging dies requires 48 hours, resulting in low efficiency and high cost. Meanwhile, surface modification processes such as shot peening and sandblasting have poor controllability and repeatability. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a method and a hot forging die for improving the lifespan of hot forging dies. This method is simple and easy to implement and can improve the lifespan of hot forging dies.

[0004] The technical solution adopted in this invention is as follows:

[0005] A method for improving the life of hot forging dies includes the following steps:

[0006] Multiple evenly distributed micro-dimples are pressed into the convex corner and flash surface that need to be reinforced in the forging die cavity. Machining allowance is reserved in the concave corner area that needs to be reinforced in the forging die cavity and local extrusion is performed. After extrusion, the concave corner area of ​​the forging die cavity has residual compressive stress.

[0007] The areas with micro-pits on the forging die cavity and the concave corners after extrusion are polished. After polishing, the final dimensions of the forging die cavity are achieved, and the surface of the forging die cavity retains the indentations of the micro-pits and the residual compressive stress layer.

[0008] Preferably, the bottom of the micro-pit is a smooth arc surface, and the upper edge of the arc surface is smoothly connected to the surface of the forging mold cavity by a section of arc-shaped curved surface.

[0009] Preferably, the micro-pits have a diameter of 0.1–0.2 mm, a depth of 0.05–0.1 mm, and a surface density of 15%–35%.

[0010] Preferably, the bottom shape of the micro-pit is a spherical segment, the height of which is less than the radius of the spherical segment, and the upper edge of the spherical segment is smoothly connected to the surface of the forging mold cavity through a section of arc-shaped curved surface with a radius of 0.08 mm.

[0011] Preferably, the machining allowance reserved for the concave corner of the forging die cavity that is prone to failure is 0.1 to 0.2 mm, and the convex corner of the anti-convex die comes into partial contact with and is squeezed by the concave corner of the forging die cavity.

[0012] Preferably, the multiple micro-dimples are distributed in an array on the surface of the convex corners and flash areas of the forging die cavity that require reinforcement.

[0013] Preferably, the reverse punch of the forging die cavity presses out a plurality of evenly distributed micro-dents at the convex corners and flash of the forging die cavity, and the reverse punch is provided with a protruding structure for pressing out the micro-dents.

[0014] Preferably, the areas with micro-pits on the forging die cavity and the concave corners after extrusion are polished. After polishing, the final dimensions of the forging die cavity are achieved.

[0015] Preferably, when the anti-punch presses out multiple uniformly distributed micro-dents on the surface of the convex corner and flash parts that need to be reinforced in the forging die cavity, the part of the anti-punch with the protruding structure makes local contact with the surface of the part of the forging die cavity that needs to be reinforced.

[0016] Preferably, when the anti-punch is extruding at the concave corner of the forging die cavity, the convex corner of the anti-punch comes into partial contact with and extrudes the concave corner of the forging die cavity.

[0017] Preferably, the protrusion structure is shaped like a spherical cap, and the spherical cap and the surface of the anti-convex mold are transitioned by an arc surface.

[0018] The present invention also provides a hot forging die, which is obtained by the method described above.

[0019] The present invention has the following beneficial effects:

[0020] This invention presses out multiple uniformly distributed micro-dimples on the convex corners and flash surfaces of the forging die cavity that require reinforcement. Machining allowances are reserved at the concave corners of the forging die cavity where reinforcement is needed. By pressing these concave corners, the residual compressive stress at the deformation points of the forging die cavity can be increased with a smaller load, causing surface work hardening, improving hardness and strength, and preventing mechanical cracking. The micro-dimples can accommodate lubricants (such as graphite), preventing the billet from displacing the graphite during flow on the die surface and preventing direct contact between the newly formed surface and the die surface. Simultaneously, the micro-dimples can also accommodate abrasive particles, reducing abrasive wear on the surface of the forging die cavity. It can be seen that the method of this invention can improve the life of hot forging dies and is simple and easy to implement. Attached Figure Description

[0021] Figure 1 These are the failure modes of different parts of the mold;

[0022] Figure 2 This is a schematic diagram of a reverse punch with micro-protrusions for extruding a forging die cavity in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the overall shape of the forging die cavity with reserved machining allowance in an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram showing the three-dimensional morphology and distribution of the micro-protrusions of the anti-convex die used for cavity extrusion in an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the micro-pits formed at the convex corners and flash of the forging die cavity after extrusion in an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram showing the three-dimensional morphology and distribution of micro-pits formed at the convex corners and flash of the die cavity after extrusion in an embodiment of the present invention.

[0027] Figure 7 This describes the morphology and size of a single micro-pit in an embodiment of the present invention;

[0028] Figure 8 The images show the morphology of the reverse punch used for extruding the forging die cavity at the concave corner of the forging die cavity and the morphology of the concave corner of the forging die cavity in the embodiments of the present invention.

[0029] Figure 9(a) is a polished morphology of the micro-pits formed at the convex corner of the forging mold cavity in an embodiment of the present invention; Figure 9(b) is a polished morphology of the micro-pits formed at the flash of the forging mold cavity in an embodiment of the present invention.

[0030] In the figure, 1-reverse punch, 2-micro-dimple, 3-forging die, 3-1-machining allowance, 4-micro-dimple morphology. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings.

[0032] The present invention provides a method for improving the life of hot forging dies, comprising: machining a forging die cavity from a heat-treated forging die blank (material H13, heat-treated hardness HRC46-48) using electrical discharge machining or machining; leaving a margin (generally 0.1-0.2 mm) at the concave corners of the forging die cavity; then using a counter-punch with locally micro-protrusions (material SKH51, hardness HRC60-62) to locally micro-extrude the easily worn protruding corners and flash areas of the forging die cavity (i.e., the protruding corners and flash that need reinforcement, the specific locations can be determined according to the actual situation); extruding and shaping the easily failing concave corner areas of the forging die cavity (i.e., the concave corner areas that need reinforcement, the specific locations can be determined according to the actual situation); polishing the surface of the forging die cavity with micro-pits generated after micro-extruded and the concave corner areas after extrusion; after polishing, the surface reaches the preset contour size of the forging die cavity, and the surface of the forging die cavity retains the pit marks of the micro-pits; after cleaning, the forging die can be put into use.

[0033] like Figure 1 As shown, the protruding corners and flash grooves of the forging die cavity are the most prone to wear and failure during use. This failure often results in workpiece dimensional deviations and surface scratches. Figure 1 The concave corners of the forging die cavity are the most prone to mechanical cracking. To address failure in these areas, a reverse punch with micro-protrusions is used, such as... Figure 2 As shown (giving the overall shape of the reverse punch), a forging die cavity with concave corners and machining allowance is used, such as... Figure 3 As shown (giving the overall morphology of the forging die cavity with reserved machining allowance), the three-dimensional morphology of these micro-protrusion anti-punches is as follows: Figure 4 As shown (the micro-protrusions of the anti-punch are given). Microtextures can be pressed into the convex corners and flashes where reinforcement is needed in the forging die cavity, forming micro-pits 2 with compressive stress on the surface, such as... Figure 5 As shown in Figure 4 (micro-pit morphology on the surface of the forging die cavity), the morphology and distribution of micro-pits on the forging die cavity are as follows. Figure 6 As shown, the morphology of a specific pit is as follows: Figure 7 As shown, the bottom of the micro-pit 2 is shaped like a spherical cap, with the height of the cap being less than its radius. The upper edge of the cap smoothly transitions to the surface of the forging die cavity via a curved arc with a radius of 0.08 mm. The diameter of the entire opening of the micro-pit 2 is 0.1–0.2 mm, and the depth is 0.05–0.1 mm. The specific dimensions and arrangement of the micro-pits 2 are determined based on the specific dimensions of the areas on the forging die cavity that require reinforcement, with a recommended surface density of 15%–35%. Simultaneously, this counter-punch can achieve extrusion shaping at the concave corners of the forging die cavity where reinforcement is needed, leaving sufficient margin. Figure 8As shown in Figures 9(a) and 9(b) (showing the morphology of the convex corner of the reverse punch and the concave corner of the forging die cavity), the concave corner of the forging die cavity reaches the final size after extrusion. Then, the convex corner and flash of the forging die cavity with micro-pits are polished and cleaned before use. After polishing, the surface reaches the final size of the forging die cavity, as shown in Figures 9(a) and 9(b) (showing the morphology of the micro-pits of the forging die cavity before and after polishing). During polishing, only the part that protruded during extrusion is removed.

[0034] This treatment method can improve the surface strength and hardness of the easily failed area of ​​the forging die cavity, increase wear resistance, and the resulting micro-pits can control the material flow rate, accommodate oxidized abrasive particles, and reduce abrasive wear.

[0035] The micro-dimples can also accommodate graphite, preventing the graphite from being squeezed out when the blank flows on the mold surface, and preventing the newly formed surface from directly contacting the mold surface.

[0036] The extrusion of the concave corner of the forging die cavity increases the residual compressive stress at the concave corner, achieving work hardening, improving hardness and strength, and preventing mechanical cracking.

[0037] As can be seen from the above scheme, the present invention has the following characteristics:

[0038] 1) Surface micro-texturing and micro-extrusion are performed only on the parts of the forging die cavity that are prone to wear, and a small machining allowance is reserved in the parts of the forging die cavity that are prone to fracture. This can increase the residual compressive stress at the deformation point of the forging die cavity, cause work hardening, increase hardness and strength, and prevent mechanical cracking.

[0039] 2) The anti-punch and the forging die cavity are only in partial contact, and the load during extrusion is small.

[0040] 3) The reverse punch can be reused, and the process is highly controllable;

[0041] 4) It can be completed in one press, which is highly efficient;

[0042] 5) The shape and proportion of the micro-protrusions of the anti-punch can be adjusted according to the wear condition, and the concave corner part with the reserved machining allowance can be adjusted, which has good process flexibility;

[0043] 6) The micro-dimples at the convex corners and flash of the forging die cavity can control the flow rate of the billet in the die cavity, accommodate hard abrasive grains, and reduce wear.

[0044] 7) The micro-pits can also accommodate graphite, preventing the graphite from being squeezed out when the blank flows on the mold surface, and preventing the newly formed surface from directly contacting the mold surface.

Claims

1. A method of improving the life of a hot forging die, characterized by, The method comprises the following steps: Uniformly distributed micro-pits (2) are pressed on the convex corner and the flash surface of the forging die cavity which needs to be strengthened, and a machining allowance is reserved and local extrusion is performed on the concave corner part of the forging die cavity which needs to be strengthened, so that the concave corner part of the forging die cavity has residual compressive stress after the extrusion is completed; The part of the forging die cavity on which the micro-pits are pressed and the concave corner part after the extrusion are polished, and the final size of the forging die cavity is reached after the polishing is completed, and the concave marks of the micro-pits are reserved on the surface of the forging die cavity; A counter punch (1) of the forging die cavity is used to press uniformly distributed micro-pits (2) on the convex corner and the flash surface of the forging die cavity, and the counter punch (1) is provided with a convex structure for pressing the micro-pits (2). The convex corner of the counter punch is locally in contact with the concave corner of the forging die cavity and is extruded.

2. A method of increasing the life of a hot swage die according to claim 1, wherein, The bottom of the micro-pit (2) is a smooth arc surface, and the upper edge of the arc surface is smoothly connected to the surface of the forging die cavity through a circular arc surface.

3. A method of increasing the life of a hot swage die according to claim 2, wherein, The diameter of the micro-pit (2) is 0.1-0.2 mm, the depth is 0.05-0.1 mm, and the area density is 15%-35%.

4. The method of increasing the life of a hot- forging die according to claim 3, wherein, The bottom of the micro-pit (2) is a spherical segment surface, the height of the spherical segment surface is less than the radius of the spherical segment, and the upper edge of the spherical segment surface is smoothly connected to the surface of the forging die cavity through a circular arc surface with a radius of 0.08 mm.

5. The method of increasing the life of a hot- forging die of claim 1, wherein, The machining allowance reserved for the concave corner part of the forging die cavity which is prone to failure is 0.1-0.2 mm.

6. The method of increasing the life of a hot- forging die of claim 1, wherein, The plurality of micro-pits (2) are arrayed on the convex corner and the flash surface of the forging die cavity which needs to be strengthened.

7. The method of increasing the life of a hot- forging die according to claim 1, wherein When the counter punch (1) presses uniformly distributed micro-pits (2) on the convex corner and the flash surface of the forging die cavity, the part of the counter punch (1) provided with the convex structure is locally in contact with the surface of the part of the forging die cavity which needs to be strengthened, and the shape of the convex structure is a spherical segment, and the spherical segment is connected to the surface of the counter punch (1) through a circular arc surface.

8. A hot forging die obtained by the method for prolonging the service life of the hot forging die according to any one of claims 1-7.

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