A forging method of a large-size round cake forging of H13 die steel

Abstract

The application discloses a kind of H13 die steel large-specification round cake forgings and a forging method, using one ingot one material forging forming process, comprising the following steps: S1.Electroslag ingot saw cutting head and tail;S2.High temperature diffusion;S3.Multi-directional forging: the electroslag ingot treated in step S2 is forged twice: first time: the electroslag ingot is upset to 1 / 2 of original height, then transverse elongation is carried out;Second time: the blank after first time upsetting and elongation is upset to 1 / 2 of its height, then multiple rolling and spinning are carried out on rotating platform, and a boss is reserved in the center of the end face of the forging during the outer diameter rolling process;After rolling and spinning, the forging plane is shaped to obtain a black skin round cake forging;S4.Water cooling after forging;S5.Ultrafine water cooling;S6.Spheroidizing annealing.The application can realize the synchronous significant improvement of product quality stability, yield and production efficiency.

Description

Technical Field

[0001] This invention relates to the field of die steel forging technology, specifically to a forging method for large-sized round disc forgings made of H13 die steel. Background Technology

[0002] With the deepening of my country's industrialization, industrial aluminum profiles are being used more and more widely in the national economy. As the traditional building profile market gradually becomes saturated and even shrinks, more and more domestic aluminum profile manufacturers are joining the competition in the industrial aluminum profile market. Industrial aluminum profiles have higher requirements in terms of mechanical properties, surface quality, and dimensional accuracy. At the same time, their complex structure makes them more difficult to produce compared to traditional building aluminum profiles. Therefore, industrial aluminum profiles place higher demands on the quality of mold materials.

[0003] In the extrusion production of large, complex cross-section aluminum profiles, die technology is the core and key technology, and has become a technical bottleneck in large-scale aluminum extrusion production, restricting the high quality of large-scale profiles. The quality of the die directly affects the quality of extruded products, yield, and production efficiency. Die costs account for 30% to 40% of extrusion production costs, or even higher.

[0004] Currently, the raw material for large-sized round disc forgings made from H13 hot work die steel, commonly used in the aluminum extrusion industry, suffers from problems such as cumbersome production processes, low yield, large quality fluctuations, and low production efficiency, resulting in high hidden costs. Therefore, die material manufacturers urgently need a forging process that balances product quality and production costs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a forging method for large-size round disc forgings of H13 mold steel, which can simultaneously and significantly improve product quality stability, yield and production efficiency.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows.

[0007] A forging method for large-sized round disc forgings made of H13 mold steel, employing a one-ingot-one-material forging process, includes the following steps: S1. Sawing the head and tail of the electroslag ingot: Remove the ingot plate at the arc-starting end and the shrinkage defects at the feeding end of the H13 electroslag ingot; S2. High-temperature diffusion: The electroslag ingot treated in step S1 is heated to 1270±10℃ for high-temperature diffusion and heat preservation, and then cooled to 1180-1220℃ for heat preservation. S3. Multi-directional forging: The electroslag ingot treated in step S2 is subjected to two-stage forging: First firing: Upset the electroslag ingot to 1 / 2 of its original height, and then draw it laterally; Second upsetting: The billet after the first upsetting and drawing is upset again to 1 / 2 of its height, and then rolled and spun multiple times on a rotating platform. During the outer diameter rolling process, a boss is reserved at the center of the end face of the forging. After the rolling and spun process is completed, the plane of the forging is shaped to obtain the black round forging. S4. Residual water cooling after forging: The black round forging obtained in step S3 is rapidly water-cooled to 500-600℃; S5. Ultra-fine water cooling: The residual hot water-cooled forgings processed in step S4 are reheated to 1020±10℃ and held at that temperature. Then, they are cooled to 200~250℃ using a water-air alternating method. S6. Spheroidizing Annealing: The ultra-fine water-cooled forgings processed in step S5 are subjected to spheroidizing annealing to obtain the finished disc forgings.

[0008] Preferably, in step S2, the electroslag ingot needs to be placed in a heating furnace at a temperature ≤600℃ for 2 hours before heating, and then the temperature is gradually increased to 1270±10℃.

[0009] Preferably, in step S2, the high-temperature diffusion heat preservation time is 2.5~3.0h / 100mm; the temperature is reduced to 1180-1220℃ and kept for 3-5h.

[0010] Preferably, in the second firing process of step S3, the multiple rounding and spinning processes include: first edge rotational rolling and second overall rounding and spinning forming, and after the first edge rotational rolling, the forging thickness is equal to the finished product thickness + machining allowance of 20mm + reserved 0.25~0.30 times the finished product thickness.

[0011] Preferably, in step S3, the process of shaping the plane of the forging to obtain the black-skinned round forging is as follows: The forging with a boss in the center is placed on the upsetting platform. The upsetting disc with a concave center is placed on the forging and the concave center is aligned with the boss. Then the upsetting disc is driven to press down as a whole to shape the overall plane of the forging and flatten the boss. At the same time, the concave center of the upsetting disc forms a sampling platform on the forging to obtain a black round forging.

[0012] Preferably, in step S3, the black skin dimensions of the obtained black-skinned round forging are: outer diameter = finished product outer diameter + 30mm, thickness = finished product thickness + 20mm; the thickness of the inspection test piece on the sampling table is 30mm.

[0013] Preferably, in step S3, the diameter of the boss is 0.35 to 0.40 times the outer diameter of the finished round forging, and the thickness is 0.30 to 0.35 times the thickness of the finished round forging; the diameter of the concave center of the upsetting disc is 700 mm and the depth is 40 mm.

[0014] Preferably, in steps S4 and S5, for a disc forging with an outer diameter D and thickness H satisfying D≥2H, the effective dimension calculation formula during cooling is as follows: Effective size = .

[0015] Preferably, in step S5, the heat preservation time is 6-10 hours.

[0016] Preferably, in step S6, the spheroidizing annealing process is as follows: The ultra-fine water-cooled forgings are heated to 830℃-880℃ and held for 15-20 hours, then furnace-cooled to 730℃-760℃ and held for 25-30 hours. Finally, they are cooled to 400℃-450℃ at a rate of ≤25℃ / h and then air-cooled after being removed from the furnace.

[0017] Due to the adoption of the above technical solutions, the technical progress achieved by this invention is as follows.

[0018] This invention boasts high production efficiency and low cost: it adopts a direct forging process of "one ingot, one material", in which electroslag ingots are directly forged into cakes, eliminating the time-consuming processes of billet opening, material distribution, intermediate billet annealing, and reheating of the cakes in traditional processes. This simplifies the complex multi-fire production into a highly efficient two-fire forming process, significantly shortening the production cycle and reducing equipment occupation and energy consumption.

[0019] This invention produces high-quality products with excellent performance: high-temperature diffusion fully eliminates as-cast segregation and primary carbides, improving the original microstructure of the material; the use of "transverse-vertical reversal" multi-directional forging enables the forging to achieve uniform deformation in different directions, significantly improving the anisotropy of the material and greatly enhancing the transverse impact toughness (average value can reach above 22J); the innovative forming process of pre-reserved boss and upsetting disc with concave core effectively solves the problem of concave center of large-sized round disc forgings, while further compacting the core microstructure, improving the density and uniformity of the core.

[0020] This invention boasts a high yield: through precise spinning and pre-reserved boss design, the machining allowance at the end face and center is reduced; in particular, the sampling platform formed by the upsetting disc concave center not only meets the inspection requirements but also avoids the increased single-sided machining amount due to the central concave center in traditional processes, significantly improving material utilization and achieving a yield of over 75%.

[0021] The present invention has good microstructure uniformity: the combination of residual hot water cooling after forging and ultra-fine water cooling effectively inhibits the precipitation of network carbides, refines the grain structure, and provides a good microstructure basis for the final spheroidizing annealing, thus obtaining a uniform spheroidized structure, which can reach AS2 level according to the NADCA#207-2022 standard.

[0022] This invention features precise process control: A dedicated formula for calculating the effective dimensions of large-sized round forgings (D≥2H) is proposed, providing a scientific basis for controlling the cooling rate of residual hot water cooling and ultrafine water cooling after forging, thus avoiding quality problems caused by improper cooling. Attached Figure Description

[0023] Figure 1 This is a metallographic diagram of Embodiment 1 of the present invention. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0025] A forging method for large-sized round disc forgings made of H13 mold steel includes the following steps: sawing the head and tail of the electroslag ingot → high-temperature diffusion → multi-directional forging → hot water cooling after forging → ultra-fine water cooling → spheroidizing annealing. Furthermore, due to the large size of the product (≥φ1000mm), this method differs from the process of dividing the forging blank into sections and then upsetting the disc. Instead, it adopts a one-ingot-one-material forging process, which can effectively improve production efficiency and save on forging blanking and intermediate billet annealing costs. The specific steps are as follows: S1. Sawing the head and tail of the electroslag ingot.

[0026] The H13 electroslag ingot has a sprue plate at the arc-starting end and a small number of shrinkage cavities at the feeding end, which are metallurgically poor areas. In order to further improve product quality and facilitate subsequent multi-directional forging, it is necessary to saw off the head and tail of the H13 electroslag ingot to remove the sprue plate at the arc-starting end and the shrinkage cavities at the feeding end.

[0027] S2. High-temperature diffusion.

[0028] H13 mold steel contains a relatively high amount of strong carbide elements such as Cr, Mo, and V. Electroslag ingots contain harmful phases such as large-sized primary carbides and elemental segregation. The electroslag ingots treated in step S1 are placed in a furnace at ≤600℃ and held for 2 hours. Then, the temperature is gradually increased to a high-temperature diffusion temperature of 1270℃±10℃, and held for 2.5~3.0 hours per 100mm. Finally, the temperature is lowered to 1180-1220℃ and held for 3-5 hours.

[0029] H13 die steel mainly consists of MC, M6C, and M7C3 type carbides, with a commonly used high-temperature diffusion temperature of 1250℃~1300℃. Higher temperatures can easily cause intergranular melting and growth, deteriorating material properties. Furthermore, the presence of local segregation lowers the solidus temperature, leading to localized melting and affecting the material's forging plasticity. Therefore, the high-temperature diffusion temperature and time need to be properly controlled, followed by forging deformation of the ingot to eliminate the negative effects caused by high-temperature diffusion.

[0030] S3. Multi-directional forging.

[0031] This step employs a two-stage forging process, which can effectively improve production efficiency. Details are as follows: The electroslag ingot treated in step S2 is subjected to two-stage forging: ① First firing: The electroslag ingot is upset to 1 / 2 of its original height, and then horizontally drawn.

[0032] Specifically, after the electroslag ingot is upsetting by 1 / 2, unlike the traditional longitudinal drawing process, this invention adopts a transverse drawing process, namely transverse and longitudinal reversal forging, in order to further improve product quality.

[0033] ② Second upsetting: The billet after the first upsetting and drawing is upset again to 1 / 2 of its height, and then rolled and spun multiple times on a rotating platform. During the outer diameter rolling process, a boss is reserved at the center of the end face of the forging. After the rolling and spun process is completed, the plane of the forging is shaped to obtain the black round forging.

[0034] Specifically, after the second upsetting process, the material is subjected to multiple rounding and spinning processes using a rotating platform. These processes include: initial edge rotational rolling and a second overall rounding and spinning.

[0035] After the first edge rotational rolling, the forging thickness = finished product thickness + machining allowance of 20mm + reserve of 0.25~0.30 times the finished product thickness (reserved for spin forming to facilitate forming corners and reduce machining allowance).

[0036] The secondary overall rolling and spinning forming is to further improve the yield and internal quality. The second upsetting process requires rolling the outer diameter to reduce the curvature protrusion of the round forging. Secondly, the outer diameter rolling process can cause the center end face of the round forging to be concave. To solve this problem, a boss is pre-reserved at the center of the forging end face during the outer diameter rolling process. The diameter of the boss is 0.35 to 0.40 times the outer diameter of the finished round forging, and the thickness is 0.30 to 0.35 times the thickness of the finished round forging.

[0037] After the spinning process is completed, the forging surface is shaped to obtain the black-skinned round forging. A forging with a central boss is placed on an upsetting platform. An upsetting disc with a central concave center is then placed on the forging, aligning the concave center with the boss. The concave center of the upsetting disc has a diameter of 700mm and a depth of 40mm. The upsetting disc is then driven to press down, resulting in a black round forging. Specifically, under pressure, the pre-reserved boss further compacts the center of the round forging, improving product quality. Secondly, the forging material corresponding to the concave center of the upsetting disc protrudes upwards, forming a sampling platform, improving material utilization. The entire plane is shaped, and the flattened pre-reserved protrusion improves the product quality in the central area. Furthermore, it reduces the central concave center caused by outer diameter rounding, lowering machining allowance and further improving material utilization. These operations effectively improve product quality and yield.

[0038] The dimensions of the black skin of the obtained black skin round forging are: outer diameter = finished outer diameter + 30mm (machining allowance of 15mm on one side), thickness = finished thickness + 20mm (machining allowance of 10mm on one side); the thickness of the inspection test piece of the sampling table is 30mm.

[0039] S4. Cool the residual hot water after forging.

[0040] Rapidly water-cooling the black-skinned round forging obtained in step S3 to 500-600℃ can effectively prevent the precipitation of network carbides.

[0041] For disc forgings with an outer diameter D and thickness H satisfying D≥2H, neither the outer diameter D nor the height H is suitable as the effective dimension during cooling. Based on theoretical calculations and actual cooling temperature variations, the formula for calculating the effective dimension during cooling of such large-sized disc forgings is as follows: Effective size =

[0042] It is also applicable to ultra-fine water cooling.

[0043] S5. Ultra-fine water cooling.

[0044] The cold forgings processed in step S4 are placed in a heat treatment furnace, reheated to 1020±10℃ and held for 6-10 hours, and then cooled to 200~250℃ using a water-air alternating method.

[0045] S6. Spheroidizing annealing.

[0046] The ultra-fine water-cooled forging processed in step S5 is subjected to spheroidizing annealing to obtain the finished disc forging.

[0047] The spheroidizing annealing process is as follows: The ultra-fine water-cooled forgings are placed in a heat treatment furnace, heated to 830℃-880℃ and held for 15-20 hours, then furnace-cooled to 730℃-760℃ and held for 25-30 hours, and finally cooled to 400℃-450℃ at a rate of ≤25℃ / h, and then air-cooled after being removed from the furnace. Example 1

[0048] In this embodiment, H13 die steel round forgings with a forging specification of φ1040mm×330mm are used as raw materials for large industrial aluminum profile extrusion dies.

[0049] The specific steps are as follows: S1. Electroslag ingot sawing: head and tail: Using conventional H13 mold steel φ590mm electroslag ingots, the ingot plate part at the arc-starting end and the shrinkage cavity part at the feeding end are removed, and the weight after sawing the tail end is 2800-2850kg.

[0050] S2. High-temperature diffusion: The electroslag ingot processed in step S1 is placed in a heating furnace and first placed in a furnace at ≤600℃ for 2 hours to allow it to heat. Then, the temperature is gradually increased to 1270±10℃ for high-temperature diffusion heat preservation for 15 hours (calculated at 2.5~3.0 hours / 100mm, approximately 15 hours is required for a φ590mm ingot). After heat preservation, the furnace is cooled to 1180~1200℃ and held for 4~5 hours before being removed from the furnace for forging.

[0051] S3. Multi-directional forging: The two-stage forging process is adopted.

[0052] First firing: The electroslag ingot, after high-temperature diffusion, is upsetting to 1 / 2 of its original height, and then horizontally elongated, changing the traditional longitudinal elongation direction.

[0053] Second forging: The billet from the first forging is upset again to half its height, then rolled and spun on a rotary platform. After the initial edge rolling, the edge thickness is spun to 440mm (finished thickness 330mm + machining allowance 20mm + reserved 0.274 times the thickness, approximately 90mm). During the spun process, a boss is reserved at the center of the forging end face, with a boss diameter of approximately φ390mm (0.375 times the finished forging outer diameter of 1040mm) and a thickness of approximately 115mm (0.348 times the finished forging thickness of 330mm). Rolling continues until the outer diameter reaches φ1070mm.

[0054] Then, the forging surface is shaped: the forging with a central boss is placed on the upsetting platform, and an upsetting disc with a central concave core (φ700mm×40mm) is placed on top of the forging, aligning the concave core with the boss; the upsetting disc is driven to press down as a whole, flattening the boss, while simultaneously using the central concave core of the upsetting disc to form a sampling platform on the forging, obtaining a black-skinned round forging with specifications of φ1070×350mm. The black skin dimensions are: outer diameter = finished outer diameter + 30mm (15mm machining allowance on one side), thickness = finished thickness + 20mm (10mm machining allowance on one side), and the thickness of the inspection test piece on the sampling platform is 30mm.

[0055] S4. Cooling with residual hot water after forging: The black round forging obtained in step S3 is rapidly water-cooled to 500–600°C. During the cooling process, the outer diameter of the forging is D = 1070 mm and the thickness is H = 350 mm, satisfying D ≥ 2H. The effective cooling dimension is calculated according to the formula: control.

[0056] S5. Ultra-fine water cooling: The cold forgings treated in step S4 are reheated to 1020℃ and held for 6 hours. Then, they are cooled to 200-250℃ using an alternating water-air cooling method. The effective cooling dimensions are controlled according to the same formula.

[0057] S6. Spheroidizing Annealing: The ultra-fine water-cooled forging processed in step S5 was placed in a heat treatment furnace for spheroidizing annealing: heated to 850℃ and held for 15 hours, then furnace-cooled to 740℃ and held for 22 hours, and finally furnace-cooled to 400℃-450℃ at a rate of ≤25℃ / h, and then air-cooled to obtain the spheroidized annealed finished round forging. Its metallographic structure is shown in the figure below. Figure 1 As shown.

[0058] Test results: ① Annealed structure: Rated AS2 according to NADCA#207-2022 standard.

[0059] ② Transverse impact performance: Tested according to NADCA#207-2022 standard. After oil cooling at 1020℃ for 30 min + air cooling at 600℃ for 2 h + air cooling at 600℃ for 2 h, the hardness of the impact specimens was 44~46HRC. The impact results of the three transverse V2 notches were 22.0J, 23.5J and 22.9J, respectively, with an average of 22.8J.

[0060] ③ Yield rate: 76.83%. Example 2

[0061] In this embodiment, H13 die steel round forgings with a forging specification of φ1250mm×450mm are used as raw materials for large industrial aluminum profile extrusion dies.

[0062] The specific steps are as follows: S1. Electroslag ingot sawing: head and tail: Using conventional H13 mold steel φ750mm electroslag ingots, the ingot plate part at the arc-starting end and the shrinkage cavity part at the feeding end are removed, and the weight after sawing the tail end is 5700-5800kg.

[0063] S2. High-temperature diffusion: The electroslag ingot processed in step S1 is placed in a heating furnace and first placed in a furnace at ≤600℃ for 2 hours to anneal. Then, the temperature is gradually increased to 1270±10℃ for high-temperature diffusion heat preservation for 20 hours (calculated at 2.5~3.0 hours / 100mm, approximately 20 hours for a φ750mm ingot). After heat preservation, the furnace is cooled to 1200~1220℃ and held for 4~5 hours before being removed from the furnace for forging.

[0064] S3. Multi-directional forging: The two-stage forging process is adopted.

[0065] First firing: The electroslag ingot, after high-temperature diffusion, is upsetting to 1 / 2 of its original height, and then horizontally drawn.

[0066] Second forging: The billet from the first forging is upset again to half its height, then rolled and spun on a rotary platform. After the initial edge rolling, the edge thickness is spun to 600mm (finished thickness 450mm + machining allowance 20mm + reserved 0.29 times the thickness, approximately 130mm). During the spun process, a boss is reserved at the center of the forging end face, with a diameter of approximately φ450mm (0.36 times the finished forging outer diameter of 1250mm) and a thickness of approximately 135mm (0.30 times the finished forging thickness of 450mm). Rolling continues until the outer diameter reaches φ1280mm.

[0067] Then, the forging surface is shaped: the forging with a central boss is placed on the upsetting platform, and an upsetting disc with a central concave core (φ700mm×40mm) is placed on top of the forging, aligning the concave core with the boss; the upsetting disc is driven to press down as a whole, flattening the boss, while simultaneously using the central concave core of the upsetting disc to form a sampling platform on the forging, obtaining a black-skinned round forging with dimensions of φ1280×470mm. The black skin dimensions are: outer diameter = finished product outer diameter + 30mm, thickness = finished product thickness + 20mm, and the thickness of the inspection test piece on the sampling platform is 30mm.

[0068] S4. Cooling with residual hot water after forging: The black round forging obtained in step S3 is rapidly water-cooled to 500–600℃. During the cooling process, the outer diameter of the forging is D = 1280 mm and the thickness is H = 470 mm, satisfying D ≥ 2H. The effective cooling dimension is calculated according to the formula: control.

[0069] S5. Ultra-fine water cooling: The cold forgings treated with residual hot water in step S4 are reheated to 1020℃ and held for 10 hours. Then, they are cooled to a material temperature of 200-250℃ using an alternating water-air cooling method. The effective cooling dimensions are controlled according to the same formula.

[0070] S6. Spheroidizing Annealing: The ultra-fine water-cooled forgings processed in step S5 are placed in a heat treatment furnace for spheroidizing annealing: heated to 860℃ and held for 20 hours, then furnace cooled to 750℃ and held for 30 hours, and finally furnace cooled to 400℃-450℃ at a rate of ≤25℃ / h, and then air-cooled to obtain the spheroidized annealed finished round forgings.

[0071] Test results: ① Annealed structure: Rated AS2 according to NADCA#207-2022 standard.

[0072] ② Transverse impact performance: Tested according to NADCA#207-2022 standard. After oil cooling at 1020℃ for 30 min + air cooling at 600℃ for 2 h + air cooling at 600℃ for 2 h, the hardness of the impact specimens was 44-46 HRC. The impact results of the three transverse V2 notches were 22.3 J, 21.6 J and 22.4 J, respectively, with an average of 22.1 J.

[0073] ③ Yield rate: 75.56%. Comparative Example 1: A comparative test without lateral elongation.

[0074] The difference between this comparative example and Example 1 is that in the first heat of multi-directional forging in step S3, the traditional longitudinal drawing is used after upsetting instead of transverse drawing. The rest of the process is the same as in Example 1.

[0075] S1. Sawing the head and tail of the electroslag ingot: Same as in Example 1.

[0076] S2. High-temperature diffusion: Same as Example 1.

[0077] S3. Multi-directional forging: After the first forging is upsetting to 1 / 2 of the original height, longitudinal elongation is performed; the second forging is the same as in Example 1 (including pre-reserved boss and upsetting disc with concave core for shaping).

[0078] S4. Cooling with residual hot water after forging: Same as in Example 1.

[0079] S5. Ultra-fine water cooling: Same as Example 1.

[0080] S6. Spheroidizing annealing: Same as in Example 1.

[0081] Test results: ① Annealed structure: Rated AS3 according to NADCA#207-2022 standards.

[0082] ② Lateral impact performance: According to the NADCA#207-2022 standard, the three lateral V2 notch impact results are 18.5J, 18.7J and 17.0J, respectively, with an average of 18.06J.

[0083] ③ Yield rate: 76.15%.

[0084] The results show that without transverse elongation and reversal forging, the anisotropy of the material is not adequately improved, and the impact toughness is significantly reduced (the average value drops from 22.8 J to 18.06 J). Comparative Example 2: Comparative Test Without Pre-reserved End Face Bosses

[0085] The main difference between this comparative example and Example 1 is that, in the second spinning process of multi-directional forging in step S3, no boss is reserved in the center of the end face; the rest of the process is basically the same as in Example 1.

[0086] S1. Sawing the head and tail of the electroslag ingot: Using φ590mm electroslag ingot, the weight after sawing the tail is 2900-2950kg (slightly higher than in Example 1, because there is no reserved boss, more raw material is needed to achieve the target size).

[0087] S2. High-temperature diffusion: Same as Example 1.

[0088] S3. Multi-directional forging: The first forging is the same as in Example 1; during the second forging, the center boss is no longer reserved, and the forging is directly rolled to an outer diameter of φ1070mm, resulting in a φ1070×360mm black-skinned round forging. After machining 10mm on one side of the end face, a local black skin remains in the center, which needs to be machined another 5mm to completely disappear.

[0089] S4. Cooling with residual hot water after forging: Same as in Example 1.

[0090] S5. Ultra-fine water cooling: The hot water-cooled forgings processed in step S4 are reheated to 1020℃, held for 8 hours, and then cooled alternately by water and air to 200-250℃.

[0091] S6. Spheroidizing annealing: Same as in Example 1.

[0092] Test results: ① Annealed structure: Rated AS3 according to NADCA#207-2022 standards.

[0093] ② Transverse impact performance: According to the NADCA#207-2022 standard, the impact specimens were tested and after being oil-cooled at 1020℃ for 30 min + air-cooled at 600℃ for 2 h + air-cooled at 600℃ for 2 h, the hardness was 44~46HRC. The impact results of the three transverse V2 notches were 19.9J, 20.6J and 19.4J, respectively, with an average of 19.96J.

[0094] ③ Yield rate: 72.37%.

[0095] The results show that not reserving the boss will cause a concave center on the end face, requiring more processing to remove the black skin, resulting in a decrease in center density, a reduction in impact performance (mean value decreased from 22.8J to 19.96J), and a significant decrease in yield (from 76.83% to 72.37%).

[0096] The above embodiments and comparative examples demonstrate that the present invention, through the use of a "one ingot, one material" process, high-temperature diffusion, transverse-vertical reversing multi-directional forging, spin forging, pre-reserved bosses and upsetting discs with concave centers for shaping, graded cooling control, and optimized spheroidizing annealing process, can stably and efficiently produce large-sized round disc forgings of H13 die steel with high yield. The resulting products exhibit superior microstructure uniformity (AS2 grade), transverse impact toughness (above 22J), and yield (above 75%) compared to the comparative examples, fully verifying the advanced nature and beneficial effects of the present invention.

Claims

1. A forging method for large-sized round disc forgings made of H13 die steel, characterized in that: The forging process using a single ingot and a single material includes the following steps: S1. Sawing the head and tail of the electroslag ingot: Remove the ingot plate at the arc-starting end and the shrinkage defects at the feeding end of the H13 electroslag ingot; S2. High-temperature diffusion: The electroslag ingot treated in step S1 is heated to 1270±10℃ for high-temperature diffusion and heat preservation, and then cooled to 1180-1220℃ for heat preservation. S3. Multi-directional forging: The electroslag ingot treated in step S2 is subjected to two-stage forging: First firing: Upset the electroslag ingot to 1 / 2 of its original height, and then draw it laterally; Second upsetting: The billet after the first upsetting and drawing is upset again to 1 / 2 of its height, and then rolled and spun multiple times on a rotating platform. During the outer diameter rolling process, a boss is reserved at the center of the end face of the forging. After the rolling and spun process is completed, the plane of the forging is shaped to obtain the black round forging. S4. Residual water cooling after forging: The black round forging obtained in step S3 is rapidly water-cooled to 500-600℃; S5. Ultra-fine water cooling: The residual hot water-cooled forgings processed in step S4 are reheated to 1020±10℃ and held at that temperature. Then, they are cooled to 200~250℃ using a water-air alternating method. S6. Spheroidizing Annealing: The ultra-fine water-cooled forgings processed in step S5 are subjected to spheroidizing annealing to obtain the finished disc forgings.

2. The forging method for a large-size round disc forging of H13 mold steel according to claim 1, characterized in that: In step S2, the electroslag ingot needs to be placed in a heating furnace at a temperature of ≤600℃ for 2 hours before heating, and then the temperature is gradually increased to 1270±10℃.

3. The forging method for a large-size round disc forging of H13 mold steel according to claim 1, characterized in that: In step S2, the high-temperature diffusion and heat preservation time is 2.5~3.0h / 100mm; the temperature is then reduced to 1180-1220℃ and kept for 3-5h.

4. The forging method for a large-size round disc forging of H13 mold steel according to claim 1, characterized in that: In the second heat treatment of step S3, the multiple rounding and spinning processes include: first edge rotation rolling and second overall rounding and spinning forming. After the first edge rotation rolling, the thickness of the forging is equal to the finished product thickness plus a machining allowance of 20mm plus a reserve of 0.25 to 0.30 times the finished product thickness.

5. The forging method for a large-size round disc forging of H13 mold steel according to claim 1, characterized in that: In step S3, the process of shaping the plane of the forging to obtain the black-skinned round forging is as follows: The forging with a boss in the center is placed on the upsetting platform. The upsetting disc with a concave center is placed on the forging and the concave center is aligned with the boss. Then the upsetting disc is driven to press down as a whole to shape the overall plane of the forging and flatten the boss. At the same time, the concave center of the upsetting disc forms a sampling platform on the forging to obtain a black round forging.

6. The forging method for a large-size round disc forging of H13 mold steel according to claim 5, characterized in that: In step S3, the black skin dimensions of the obtained black-skinned round forging are: outer diameter = finished product outer diameter + 30mm, thickness = finished product thickness + 20mm; the thickness of the inspection test piece on the sampling table is 30mm.

7. The forging method for a large-size round disc forging of H13 mold steel according to claim 1, characterized in that: In step S3, the diameter of the boss is 0.35 to 0.40 times the outer diameter of the finished round forging, and the thickness is 0.30 to 0.35 times the thickness of the finished round forging; the diameter of the concave center of the upsetting disc is 700 mm and the depth is 40 mm.

8. The forging method for a large-size round disc forging of H13 mold steel according to claim 1, characterized in that: In steps S4 and S5, for a disc forging with an outer diameter D and thickness H satisfying D≥2H, the effective dimension calculation formula during cooling is as follows: Effective size = .

9. The forging method for a large-size round disc forging of H13 mold steel according to claim 1, characterized in that: In step S5, the heat preservation time is 6-10 hours.

10. A forging method for a large-size round disc forging of H13 mold steel according to claim 1, characterized in that: In step S6, the spheroidizing annealing process is as follows: The ultra-fine water-cooled forgings are heated to 830℃-880℃ and held for 15-20 hours, then furnace-cooled to 730℃-760℃ and held for 25-30 hours. Finally, they are cooled to 400℃-450℃ at a rate of ≤25℃ / h and then air-cooled after being removed from the furnace.

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