A method of processing a shrapnel warhead

Abstract

The application discloses a processing method of a shrapnel warhead and belongs to the technical field of machining, and solves the technical problems of profile limitation, material waste and mold scrap in stamping a shrapnel warhead by using a traditional integrated cylindrical lower mold. The stamping mold comprises an upper mold and a lower mold, the lower mold comprises a left module and a right module which are split into two halves along an axis, and the left module and the right module form a mold cavity matched with the outer profile of the target shrapnel warhead after being closed. The application can realize the stamping processing of twice stamping into a hole in one mold cavity for products with complex profiles such as equal-diameter, large-diameter-down-small-diameter, avoid heat loss caused by mold cavity replacement, reduce the contact time of the punch and the blank, avoid the tempering of the punch, greatly reduce the subsequent machining amount, simplify the machining process, and facilitate the repair of the split lower mold. The mold cavity can be reprocessed by machining, the upper mold can be repaired by using the cladding welding technology, and the mold can be repeatedly repaired and utilized.

Description

Technical Field

[0001] This invention relates to the field of machining technology, and in particular to a method for machining a grenade warhead. Background Technology

[0002] The shell forming of a grenade warhead is one of the core processes in grenade manufacturing. Traditional stamping processes generally use an integrated cylindrical lower die. After a solid round steel billet is placed into the cylindrical lower die, a blind hole is formed by stamping from the opening end of the shell of the lower die through an upper die. Because the integrated cylindrical lower die needs to ensure that the product can be easily removed after stamping, the die cavity can only be designed as a tapered structure with a smaller bottom and a larger top. This results in the outer surface of the stamped grenade warhead inevitably having a fixed taper, making it impossible to achieve complex outer peripheral contours such as uniform diameter and a larger bottom and a smaller top. This restricts the diversity of grenade warhead shapes and makes it difficult to meet the diverse requirements of modern ammunition for aerodynamic performance, fragmentation killing effect, and filler utilization.

[0003] Meanwhile, the one-piece cylindrical lower die has poor tolerance for blanks. For warheads with special local structures or specific wall thickness distribution requirements, it is difficult to achieve precise forming. Stress concentration and uneven material flow are prone to occur during the stamping process, resulting in product shell cracking and excessive wall thickness deviation, which affects product quality and production qualification rate.

[0004] To address the contour limitation issue, existing technologies employ a "multi-pass stamping + subsequent machining" process. This involves first stamping to obtain a tapered blank, followed by machining on lathes, milling machines, etc. However, this process has significant drawbacks: multi-pass stamping increases process complexity and production costs; extensive machining results in a serious waste of high-value metal materials and prolongs the production cycle; the cutting forces and heat from machining can damage the internal structure of the grenade warhead shell, reducing the material's mechanical properties and affecting the overall strength and explosive power of the grenade warhead; for thin-walled grenade warheads with complex internal structures, machining is also prone to deformation due to insufficient workpiece rigidity, further reducing the yield rate.

[0005] In addition, the thickness of the traditional one-piece cylindrical lower mold is limited by the structure, and the mold cavity is narrow. After the mold cavity is worn, it is difficult to repair it effectively in the narrow space. The only option is to replace it with a new mold, which results in high usage costs and frequent mold replacements will reduce production efficiency.

[0006] In addition, the traditional method of processing grenade warheads generally involves pressing, punching, and stretching. Pressing involves pressing the blank into a solid block, then transferring it to the punching cavity for punching, and then transferring it to the stretching cavity for stretching. During the transfer of mold cavities, heat loss is inevitable, which will also affect the processing rhythm and requires multiple sets of molds.

[0007] Therefore, there is an urgent need to develop a processing method for grenade warheads that can remove the constraints on the outer contour of the product, achieve precise and efficient forming, improve material utilization and product quality, and reduce mold usage costs. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for processing grenade warheads, solving the technical problems of limited contours, material waste, low forming accuracy, poor product qualification rate, and easy mold scrapping when using traditional one-piece cylindrical lower molds to stamp grenade warheads. This method enables direct stamping forming of grenade warheads with complex outer contours, improves material utilization and processing efficiency, allows for repeated use of molds, and reduces production costs.

[0009] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for processing a grenade warhead uses a stamping die for processing the grenade warhead, including an upper die and a lower die. The lower die has a split structure and includes a left module and a right module that are split in half along the axis. When the lower die is closed, it forms a cavity that matches the outer contour of the target grenade warhead.

[0011] The specific processing steps are as follows:

[0012] S1. Lower mold closing: The left and right modules of the lower mold are spliced ​​together using a hydraulic mechanism to ensure a tight seam between the left and right modules;

[0013] S2. Blank placement:

[0014] S21. Pre-stamping and positioning: A solid round steel billet heated to a preset temperature is placed in the cavity of the lower mold. A variable diameter positioning cylinder is installed on it. The lower end of the variable diameter positioning cylinder has a positioning flange that matches the solid round steel billet. The upper end of the variable diameter positioning cylinder has a positioning hole for accommodating the primary punch. The lower diameter of the variable diameter positioning cylinder is smaller than the inner diameter of the cavity of the lower mold, and the upper diameter of the variable diameter positioning cylinder is larger than the inner diameter of the cavity of the lower mold. The variable diameter positioning cylinder is used to initially position the solid round steel billet so that the solid round steel billet is in the center position in the cavity. Then, the primary punch presses down on the variable diameter positioning cylinder, so that the solid round steel billet undergoes lateral deformation in the cavity of the lower mold until the outer contour of the billet abuts against the inner wall of the cavity of the lower mold, ensuring that the billet and the cavity are coaxial and without offset.

[0015] S22. Pre-punching: Remove the variable diameter positioning cylinder, press down the primary punch again, and directly punch the blank in the mold cavity of the lower die. Under the action of the primary punch, the blank undergoes plastic deformation in the mold cavity and extends upward in the cavity formed by the mold cavity of the lower die and the primary punch, forming a blank with a primary blind hole in the mold cavity.

[0016] S3. Blind hole punching: Adjust the punching speed and pressure of the upper die, and control the upper die to punch at a constant speed from the opening end of the primary blind hole of the blank into the mold cavity, so that the blank undergoes plastic deformation under the constraint of the mold cavity, and its outer contour fits the inner wall of the mold cavity. At the same time, a blind hole of a preset depth is punched in the blank to form the preliminary shell structure of the grenade warhead.

[0017] S4. Mold Disassembly and Product Removal: After the stamping operation is completed, the upper mold is lifted and the upper mold is separated from the lower mold. Then, the left and right modules of the lower mold are separated along the splitting surface. The formed grenade warhead shell is removed, and the stamping process is completed.

[0018] Furthermore, the cavities of the upper and lower dies are coaxial. During the stamping process, the blank with the primary blind hole will automatically center under the downward pressure of the upper die, ensuring that the subsequent stamping pressure is evenly transmitted and avoiding local deformation or cracking of the blank due to uneven force.

[0019] Furthermore, after the upper mold is worn, it is repaired using cladding welding technology, and after the lower mold is worn, the mold cavity surface is re-machined by machining. The upper mold and the lower mold are made of H13 hot work die steel.

[0020] Furthermore, the specific steps for repairing the upper mold using cladding welding technology are as follows:

[0021] S101. Grinding and impurity removal: Grind the worn parts of the upper mold to remove surface oxide scale, oil stains, rust and fatigue layer, and expose fresh metal substrate. The roughness is controlled at Ra 3.2~6.3μm to increase the contact area between the cladding layer and the substrate.

[0022] S102. Preheating treatment: Preheat the entire upper mold to 300~400℃, with a heating rate of ≤50℃ / h, to eliminate internal stress in the upper mold and prevent cold cracks in the substrate due to excessive temperature difference during cladding, thus creating conditions for diffusion bonding between the molten pool and the substrate.

[0023] S103. Select electric arc cladding or laser cladding process, use cobalt-based alloy welding materials, control the cladding current to 180-220A, voltage to 22-26V, and welding speed to 5-8mm / s, and ensure that the molten pool temperature is moderate so that the cobalt-based alloy of the welding material can undergo sufficient element diffusion at the interface with the upper mold substrate to form a continuous bonding layer.

[0024] S104. When using multi-layer and multi-pass cladding, the interlayer temperature should be maintained at 200~300℃ to avoid interlayer cold shut. At the same time, after each cladding pass, lightly hammer to eliminate interlayer stress and ensure the continuity of metallurgical bonding between the interlayer and the substrate.

[0025] S105. After the cladding is completed, place the upper mold in an asbestos felt or a heat preservation box to cool to room temperature. The cooling rate should be ≤30℃ / h to prevent microcracks from forming on the bonding surface due to thermal stress, which could damage the metallurgical bonding interface.

[0026] S106. Post-repair inspection: Conduct performance testing on the cladding layer;

[0027] S107. Machining to the required dimensions.

[0028] Furthermore, in step S103, the welding material is dried at 200~250℃ for 1~2 hours before use to remove moisture from the welding material and avoid the formation of pores during cladding.

[0029] Furthermore, in step S104, the thickness of a single cladding layer is controlled to be between 0.5 and 1 mm to prevent excessive thickness of the single cladding layer from causing stress concentration and cracking.

[0030] Furthermore, in step S104, the subsequent cladding layer slightly remelts the surface of the previous cladding layer to eliminate the coarse grain area of ​​the previous cladding layer, so that the entire layer structure remains uniform and fine.

[0031] The beneficial effects of this invention are:

[0032] The lower mold adopts a split structure, which allows the product to be removed by disassembling the lower mold. This completely eliminates the limitations of the traditional one-piece cylindrical lower mold on the tapered shape of the product's outer perimeter, which is smaller at the bottom and larger at the top. It can directly stamp and form grenade warheads with various complex outer perimeters, such as those with the same diameter and larger at the bottom and smaller at the top. This provides full freedom for the shape design of the warhead and can meet the diverse needs of modern ammunition in terms of aerodynamic performance and fragmentation killing effect.

[0033] The mold cavity can be precisely matched with the outer contour and wall thickness distribution according to the design requirements of the target warhead. The blank undergoes plastic deformation under the full constraint of the mold cavity. There is no need to consider the constraint condition of small bottom and large top that must be followed when taking it out axially. The stampable shape structure is greatly expanded.

[0034] The processing method of the present invention uses two punches to punch holes in the same mold cavity in two stages, which avoids heat loss caused by changing mold cavities during the forming process, reduces the contact time between a single punch and the hot blank, reduces the risk of the punch itself being tempered, and improves the service life of the punch. Since there is no time to change mold cavities, the processing speed is also improved.

[0035] In addition, the upper and lower molds are made of H13 hot work die steel, and the split structure design makes the repair of the lower mold extremely convenient.

[0036] During the stamping process, the surface of the die cavity is prone to wear. When the wear is severe, the worn lower die, due to its split structure with symmetrical cutting along the axis, can have its cavity formed by the surface of either the left or right module. This surface can be machined and repaired separately. After repair, the stroke of the hydraulic mechanism can be adjusted so that the left and right modules can be closed to form the required cavity. Thus, the split-type lower die can be repaired repeatedly. If the split structure is thick enough, it can even be repaired dozens or even hundreds of times, greatly improving the service life of the lower die and avoiding the situation where the lower die had to be replaced directly after damage.

[0037] For worn upper molds, the worn parts can be repaired by cladding welding. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of the grenade warhead to be processed according to the present invention;

[0039] Figure 2 This is a schematic diagram of the left module structure of the lower mold of the present invention;

[0040] Figure 3 This is a perspective structural diagram of the mold of the present invention, which is divided into a left module and a right module;

[0041] Figure 4 This is a structural schematic diagram of the left and right modules of the mold in the mold-closing state of the present invention;

[0042] Figure 5 This is a simplified cross-sectional view of the lower mold in the closed state.

[0043] Figure 6 This is a schematic diagram of step S21 of the stamping process of the present invention;

[0044] Figure 7 This is a schematic diagram of the first half of step S22 of the stamping process of the present invention;

[0045] Figure 8 This is a schematic diagram of the second half of step S22 in the stamping process of the present invention;

[0046] Figure 9 This is a schematic diagram of the first half of step S3 in the stamping process of the present invention;

[0047] Figure 10 This is a schematic diagram of the second half of step S3 in the stamping process of the present invention;

[0048] Figure 11 This is a schematic diagram of step S4 of the stamping process of the present invention.

[0049] The component names indicated by the numbers in the attached diagram are as follows:

[0050] 1. Positioning structure; 2. Lower mold; 21. Left module; 22. Right module; 3. Mold cavity; 4. Positioning hole; 5. Variable diameter positioning cylinder; 6. Primary punch; 7. Solid round steel billet; 8. Primary blank; 9. Second punch; 10. Grenade warhead. Detailed Implementation

[0051] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0052] Example 1

[0053] This invention provides a processing method such as Figure 1 The method for manufacturing the grenade warhead with a narrow waist-shaped profile shown employs a stamping die. The stamping die includes an upper die and a lower die 2. The lower die 2 can be split horizontally along its axis into a left module 21 and a right module 22. The structural diagram of the left module 21 is shown below. Figure 2 As shown, the left module 21 and the right module 22 are assembled to obtain the mold cavity 3 of the lower mold 2; as Figure 3 As shown, the left module 21 and the right module 22 are provided with positioning structures 1. The positioning structure 1 includes a positioning boss on the left module 21 and a corresponding positioning recess on the right module 22. The positioning boss and the positioning recess cooperate to achieve precise positioning of the two during mold closing. After closing, the left module 21 and the right module 22 are spliced ​​together to form a complete lower mold 2, as shown. Figure 4 As shown, Figure 5 This is a simplified cross-sectional view of the lower mold 2 in the closed state.

[0054] The specific processing steps are as follows:

[0055] Mold assembly: The left module 21 and right module 22 of the lower mold 2, which are detachable along the axis, are precisely spliced ​​together to form a complete lower mold 2, with no gaps after the splicing point is positioned;

[0056] Billet placement: Place the 45# steel solid round billet 7 heated to 1000 to 1150℃ into the mold cavity 3 of the lower mold 2 mentioned above;

[0057] Pre-stamping positioning: Since the diameter of the solid round steel billet 7 before deformation is much smaller than the cavity 3 of the lower die 2, direct stamping may cause eccentricity. Therefore, the billet is pre-positioned using the variable diameter positioning cylinder 5. Figure 6As shown, the lower end of the variable diameter positioning cylinder 5 is provided with a positioning flange, which is adapted to the solid round steel billet 7. The upper end of the variable diameter positioning cylinder 5 is provided with a positioning hole 4 for accommodating the primary punch 6. The lower diameter of the variable diameter positioning cylinder 5 is smaller than the inner diameter of the cavity 3 of the lower mold 2, and the upper diameter of the variable diameter positioning cylinder 5 is larger than the inner diameter of the cavity 3 of the lower mold 2. With the help of this variable diameter positioning cylinder 5, the solid round steel billet 7 is initially positioned so that the solid round steel billet 7 is located in the center position in the cavity 3. Then, the primary punch 6 presses down on the variable diameter positioning cylinder 5, and the pressing speed is controlled at 50-200mm / s, so that the solid round steel billet 7 undergoes lateral deformation in the cavity 3 of the lower mold 2 until the billet radially thickens and deforms, and the outer contour abuts against the inner wall of the cavity 3 of the lower mold 2, forming a shape like... Figure 7 The primary blank 8 shown has a cavity 3 of the lower die 2 coaxially fitted with the primary punch 6. The inner wall of the cavity 3 is constrained to achieve strong centering, ensuring that the blank and the cavity 3 are coaxial and that the blank will not be eccentric or skewed during subsequent stamping.

[0058] Pre-punching during machining: such as Figure 8 As shown, the variable diameter positioning cylinder 5 is removed, so that the primary punch 6 is pressed down again and directly punches the blank in the cavity 3 of the lower mold 2. Under the action of the primary punch 6, the blank undergoes plastic deformation extending along the axial direction in the cavity 3. The blank extends upward along the cavity 3 formed by the cavity 3 of the lower mold 2 and the primary punch 6, forming a blank with a primary blind hole.

[0059] Blind hole punching: such as Figure 9 As shown, the second punch 9 is switched. The outer contour of the second punch 9 is the same as the inner contour required for the final product. The second punch 9 continues to punch based on the primary blind hole obtained by the primary punch 6, so that the blank continues to undergo plastic deformation under the constraint of the mold cavity 3. The outer periphery is tightly attached to the inner wall of the lower mold 2. The blank continues to extend and deform upward along the cavity 3 formed by the mold cavity 3 of the lower mold 2 and the primary punch 6, as shown. Figure 10 As shown, the final result is as follows: Figure 11 The preliminary casing structure of the required grenade warhead 10 is shown;

[0060] Mold disassembly and product removal: After stamping, the upper mold rises and exits, and the lower mold 2 separates under the drive of the hydraulic mechanism, directly removing the preliminary shell structure of the formed grenade warhead 10, and then obtaining the final product through subsequent precision machining and other processes.

[0061] The shell of the grenade warhead 10 with a narrow waist obtained by stamping using the method of this embodiment does not require cutting processing compared with the traditional one-piece cylindrical lower mold stamping and then machining of the waisted cylindrical body. Compared with the lower small and upper large cylindrical body, the material usage is reduced by 20% and the production cycle is shortened by 60%.

[0062] This invention employs a lower die 2 that can be split along its axis, enabling the production of a product with a thicker middle and thinner ends in a single process. This avoids the limitation of traditional grenade warhead 10 manufacturing processes where the outer contour must be conical. Furthermore, dividing the punching process into pre-punching with a primary punch 6 and blind hole punching with a second punch 9 shortens the continuous heating time of the primary and second punches 6 and 9, preventing material degradation due to prolonged heating during punching and extending the punch's service life. In addition, step-by-step punching allows for more precise control of the blank's deformation amount and rate, further reducing internal stress caused by sudden, intense deformation, lowering the risk of product cracking, and improving the structural integrity and dimensional accuracy of the warhead shell. In this embodiment, the diameter of the primary punch 6 is slightly smaller than that of the second punch 9, and the depth of the primary punch is approximately two-thirds of the final blind hole depth. This provides sufficient deformation space for blind hole punching and allows for preliminary determination of the blank's axial position through the primary punching, ensuring the coaxiality of the punch and blank during blind hole punching.

[0063] Example 2

[0064] The mold in Example 1 is made of H13 hot work die steel (4Cr5MoSiV1). When the mold wears out due to long-term use, the upper mold can be repaired using cladding welding technology: cobalt-based alloy welding wire (thermal expansion coefficient 14.2×10) is used. -6 The worn parts are repaired by cladding welding at ℃ (20-600℃). The process parameters are strictly controlled during the welding process to ensure that the cladding layer forms a metallurgical bond with the H13 substrate.

[0065] The specific steps are as follows:

[0066] S101. Grinding and cleaning: Use an angle grinder and sandpaper to grind the worn parts of the mold on H13 to remove surface oxide scale, oil, rust and fatigue layer, and expose fresh metal substrate. The roughness is controlled at Ra 3.2~6.3μm to increase the contact area between the cladding layer and the substrate.

[0067] S102. Preheating treatment: Preheat the entire upper mold of H13 to 300~400℃ (using medium frequency heating or oven heating), slowly increase the temperature (heating rate ≤50℃ / h), eliminate the internal stress of the upper mold, and at the same time avoid cold cracks in the substrate due to excessive temperature difference during cladding, and create conditions for diffusion bonding between the molten pool and the substrate.

[0068] S103. Select either arc cladding or laser cladding (arc cladding is preferred for on-site repair), control the cladding current to 180-220A, voltage to 22-26V, and welding speed to 5-8mm / s, and ensure a moderate molten pool temperature so that the cobalt-based alloy of the welding wire and the H13 matrix undergo sufficient element diffusion (bidirectional diffusion of Cr and Mo elements) to form a continuous bonding layer. Before use, the welding wire should be dried at 200-250℃ for 1-2 hours to remove any moisture that may be present in the welding wire and avoid porosity during cladding.

[0069] S104. When using multi-layer, multi-pass cladding, the interlayer temperature should be maintained at 200~300℃ to avoid interlayer cold shuts. At the same time, after each cladding pass, the interlayer stress should be lightly hammered to eliminate the stress between the layers and ensure the continuity of the metallurgical bond between the layers and the substrate. The electric arc of the subsequent cladding pass slightly remelts the surface of the previous cladding layer to eliminate the coarse grain areas of the previous cladding layer, so that the overall microstructure remains uniform and fine. The thickness of a single cladding layer should be controlled between 0.5 and 1 mm to prevent stress concentration and cracking caused by excessive thickness of a single cladding layer.

[0070] S105. After the cladding is completed, place the upper mold in an asbestos felt or a heat preservation box and slowly cool it to room temperature (cooling rate ≤30℃ / h) to prevent microcracks from forming on the bonding surface due to thermal stress, which would damage the metallurgical bonding interface.

[0071] S106. Post-repair inspection: The performance of the cladding layer is tested. The hardness of the cladding layer is 56HRC. The microstructure is fine dendrites with no coarse grains or defects. The surface is flat and free of pores, cracks, and inclusions. The difference in the coefficient of thermal expansion between the cladding layer and H13 hot work die steel is 8%, which meets the matching requirements.

[0072] S107. Machining Re-manufacturing: Perform CNC precision machining on the cladding layer to restore the upper mold to the preset dimensions.

[0073] In the above steps, Stellite6 / Stellite12 cobalt-based alloy welding wire (suitable for high-temperature and wear-resistant conditions) is preferred. It contains 25-30% Cr and 4-6% W. After cladding, the hardness of the substrate can reach 55-62 HRC. With slight adjustments to the process, it can fall within the target range of 53-60 HRC.

[0074] Control the dilution rate during the cladding process to 10% to 15% (too high a dilution rate will cause the cobalt-based alloy to be diluted by the H13 matrix, resulting in a decrease in hardness). By adjusting the welding torch angle (70 to 80 degrees from the matrix) and the wire feeding speed, avoid excessive melting of the matrix and ensure the alloy composition ratio of the cladding layer.

[0075] After the cladding is completed and slowly cooled to room temperature, the upper mold is tempered at a low temperature of 200~250℃, held for 2~3 hours and then air-cooled to eliminate the quenching stress of the cladding layer. At the same time, the hardness is finely adjusted to the target range (e.g., the hardness of Stellite6 before tempering after cladding is 60~62HRC, and after tempering it is reduced to 55~58HRC), taking into account both hardness and toughness.

[0076] For the worn lower mold 2, since the lower mold 2 with the split structure is thick enough, after the mold cavity 3 is worn, the surface of the mold cavity 3 can be re-machined by machining to form a new mold cavity 3 surface. Then, by adjusting the stroke of the hydraulic mechanism, a brand new lower mold 2 can be obtained.

[0077] In summary, both the upper and lower molds 2 of this stamping die can be easily repaired and processed. In practice, it has been processed and used thousands of times, and it can still guarantee the stamping accuracy and product quality of the grenade warhead 10.

[0078] In addition, to ensure the bonding performance and usability of the repaired cladding layer with the upper mold substrate, the cladding welding must strictly adhere to the following quality standards:

[0079] Bonding strength requirements: The cladding layer and the H13 hot work die steel substrate should form a metallurgical bond to ensure that the upper die has the performance of high temperature resistance, extrusion resistance and wear resistance, and to prevent the cladding layer from falling off during the stamping process.

[0080] Hardness requirement: When using cobalt-based welding wire for cladding, the hardness of the cladding layer needs to reach 53-60 HRC to match the hardness requirements of the die stamping process.

[0081] Microstructure requirements: The cladding layer should have a fine and uniform microstructure, such as dendrites and equiaxed crystals, to avoid coarse grains or defective structures, ensure the uniformity of the cladding layer's performance, and prevent localized weakness from causing rapid wear of the upper mold again.

[0082] Surface quality requirements: The surface of the cladding layer should be flat and uniform, and free from defects such as pores, cracks, and inclusions, to reduce the workload of subsequent mold repair and to avoid defects causing surface flaws on the product during the stamping process.

[0083] Thermal expansion coefficient matching requirements: The thermal expansion coefficient of cobalt-based alloys should be controlled at 13.0-15.0×10⁻⁶ within the temperature range of 20-600℃. -6 / ℃, the difference in thermal expansion coefficient between it and H13 mold steel in the same temperature range must be ≤15%; it is strictly forbidden to use cobalt-based materials with a thermal expansion coefficient difference exceeding 30%, to avoid interface failure and network microcracks in the cladding layer due to the mismatch in thermal expansion coefficients during the stamping heating or cooling process of the mold.

[0084] Standardization of cladding welding technology ensures repair quality: The core technical points of cladding welding, such as metallurgical bonding, hardness, microstructure, surface quality and matching of thermal expansion coefficient, are clarified to ensure the bonding performance and service performance of the cladding layer and the H13 mold steel substrate. This avoids problems such as cladding layer peeling, microcracks and interface failure in the mold after repair, and ensures the stamping accuracy and wear resistance of the mold after repair.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for processing a grenade warhead, comprising a stamping die, wherein the stamping die includes an upper die and a lower die (2), the lower die (2) being a split structure comprising a left module (21) and a right module (22) split in half along an axis, wherein the lower die (2), when closed, forms a cavity (3) matching the outer contour of the target grenade warhead (10), characterized in that, The specific processing steps are as follows: S1. Lower mold (2) closing: The left module (21) and right module (22) of the lower mold (2) are spliced ​​together by hydraulic mechanism; S2. Blank placement: S21, Pre-stamping and positioning: The solid round steel billet (7) heated to the preset temperature is placed in the mold cavity (3), and a variable diameter positioning cylinder (5) is provided on it; the lower diameter of the variable diameter positioning cylinder (5) is smaller than the inner diameter of the mold cavity (3), and a positioning protrusion is provided on it; the upper diameter of the variable diameter positioning cylinder (5) is larger than the inner diameter of the mold cavity (3), and a positioning hole (4) for accommodating the primary punch (6) is provided on it; the variable diameter positioning cylinder (5) performs preliminary positioning of the solid round steel billet (7), and the primary punch (6) presses down on the variable diameter positioning cylinder (5), so that the solid round steel billet (7) undergoes lateral deformation in the mold cavity (3) until the outer contour of the solid round steel billet (7) abuts against the inner wall of the mold cavity (3); S22, Pre-punching: Remove the variable diameter positioning cylinder (5), and press down the primary punch (6) again to directly punch the blank. Under the action of the primary punch (6), the blank undergoes plastic deformation in the mold cavity (3) and extends upward in the cavity formed by the mold cavity (3) and the primary punch (6) to form a blank with a primary blind hole in the mold cavity (3). S3, Blind hole punching: Control the upper die to punch into the mold cavity (3) at a uniform speed, so that the blank undergoes plastic deformation under the constraint of the mold cavity (3), and a blind hole of a preset depth is punched into the blank to form the preliminary shell structure of the grenade warhead (10); S4. Mold disassembly and product removal: The upper mold and the lower mold (2) are separated, the left module (21) and the right module (22) are separated, and the formed grenade warhead (10) shell is removed.

2. The processing method for the grenade warhead according to claim 1, characterized in that, The upper mold and the cavity (3) of the lower mold (2) are coaxial. During the stamping process, the blank with the primary blind hole will automatically be centered under the pressure of the upper mold, ensuring that the subsequent stamping pressure is evenly transmitted and avoiding local deformation or cracking of the blank due to uneven force.

3. The processing method for the grenade warhead according to claim 2, characterized in that, After the upper mold is worn, it is repaired by cladding welding technology. After the lower mold (2) is worn, the surface of the mold cavity is re-machined by machining. The upper mold and the lower mold (2) are made of H13 hot work die steel.

4. The method for processing a grenade warhead according to claim 3, characterized in that, The specific steps for repairing the upper mold using cladding welding technology are as follows: S101. Grinding and impurity removal: Grind the worn parts of the upper mold to remove surface oxide scale, oil stains, rust and fatigue layer, and expose fresh metal substrate. The roughness is controlled at Ra 3.2~6.3μm to increase the contact area between the cladding layer and the substrate. S102. Preheating treatment: The upper mold is preheated to 300~400℃, with a heating rate of ≤50℃ / h, to eliminate the internal stress of the upper mold and at the same time to avoid cold cracks in the substrate due to excessive temperature difference during cladding, thus creating conditions for diffusion bonding between the molten pool and the substrate. S103. Select an electric arc cladding or laser cladding process, use cobalt-based alloy welding materials, control the cladding current to 180-220A, voltage to 22-26V, and welding speed to 5-8mm / s, and ensure that the molten pool temperature is moderate so that the cobalt-based alloy of the welding materials and the upper mold substrate interface can undergo sufficient element diffusion to form a continuous bonding layer. S104. When using multi-layer and multi-pass cladding, the interlayer temperature should be maintained at 200~300℃ to avoid interlayer cold shut. At the same time, after each cladding pass, lightly hammer to eliminate interlayer stress and ensure the continuity of metallurgical bonding between the interlayer and the substrate. S105. After the cladding is completed, the upper mold is placed in an asbestos felt or a heat preservation box to cool to room temperature. The cooling rate is ≤30℃ / h to prevent microcracks from forming on the bonding surface due to thermal stress, which would damage the metallurgical bonding interface. S106. Post-repair inspection: Conduct performance testing on the cladding layer; S107. Machining to the required dimensions.

5. The method for processing a grenade warhead according to claim 4, characterized in that, In step S103, the welding material is dried at 200~250℃ for 1~2 hours before use to remove moisture from the welding material and avoid the formation of pores during cladding.

6. The method for processing a grenade warhead according to claim 4, characterized in that, In step S104, the thickness of a single cladding layer is controlled to be between 0.5 and 1 mm to prevent stress concentration and cracking caused by excessive thickness of the single cladding layer.

7. The method for processing a grenade warhead according to claim 4, characterized in that, In step S104, the subsequent cladding layer slightly remelts the surface of the previous cladding layer to eliminate the coarse grain area of ​​the previous cladding layer, so that the entire layer structure remains uniform and fine.

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