High-efficiency batch forging method for Cr12MoV steel

Abstract

This invention discloses a high-efficiency diffusion batch forging method for Cr12MoV steel. It employs a conventional heating furnace for pre-forging heating and holding, and a diffusion heating furnace for inter-forging diffusion annealing of the billets. The furnace temperature is controlled as follows: when the cumulative forging ratio of the billets entering the furnace is <2.0, the furnace temperature is controlled at 1160±5℃; when the cumulative forging ratio of the billets entering the furnace is 2.0≤ and <4.0, the furnace temperature is controlled at 1175±5℃; when the cumulative forging ratio of the billets entering the furnace is ≥4.0, the furnace temperature is controlled at 1190±5℃; when the cumulative forging ratios of the billets in the diffusion heating furnace are inconsistent, the furnace temperature is controlled according to the billet with the lowest cumulative forging ratio. This method designs a forging process that combines two types of heating furnaces, conventional heating furnace and diffusion heating furnace, for heating and heat preservation. Under the condition of almost no change in the total forging time, it innovatively integrates high-temperature diffusion annealing process into the forging process, which greatly improves the compositional segregation and eutectic carbide state of the billet, and successfully realizes efficient diffusion batch forging of Cr12MoV steel.

Description

Technical Field

[0001] This invention relates to a forging process, and more particularly to a high-efficiency diffusion batch forging method for Cr12MoV steel. Background Technology

[0002] Cr12MoV is a widely used cold work die steel in my country. It belongs to the high-carbon ledeburitic steel category, with a carbon content of approximately 1.5 wt%. In its as-cast state, it exhibits severe compositional segregation and highly developed eutectic carbide dendrites. If left uncontrolled, this can severely impact the steel's mechanical properties and the service life of the dies. The most effective methods to improve compositional segregation and break up eutectic carbides in Cr12MoV steel are forging and high-temperature diffusion annealing. Forging effectively breaks up eutectic carbides, especially in large-deformation, multi-directional, repeated upsetting forging. High-temperature diffusion annealing utilizes the long-range diffusion of elements at high temperatures to slowly promote element homogenization, improving compositional segregation. The higher the temperature of the high-temperature diffusion annealing, the more significant the improvement effect.

[0003] For Cr12MoV steel, its high carbon content and severe compositional segregation in the as-cast microstructure result in a relatively lower acceptable high-temperature diffusion annealing temperature compared to other low-carbon steels, approaching the holding temperature for forging. In the as-cast state, if the high-temperature diffusion temperature is too high, the segregated areas are prone to overheating and even re-liquefaction, leading to billet scrap. However, as the forging process progresses, the compositional segregation improves, and the acceptable high-temperature diffusion annealing temperature for the billet increases. Theoretically, continuously increasing the holding temperature of Cr12MoV steel during forging can maximize the improvement of compositional segregation and breakup of eutectic carbides. However, excessively high or low forging temperatures can reduce the plasticity of the billet, leading to forging cracks.

[0004] Therefore, designing a suitable method for forging Cr12MoV steel, making efficient and reasonable use of the characteristic that the compositional segregation of the billet continuously improves during the forging process, and carrying out targeted high-temperature diffusion annealing to maximize the improvement of compositional segregation and eutectic carbide state, thereby improving product quality, is of great significance, especially for large-batch batch forging of billets with large quantities and similar processes. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an efficient diffusion batch forging method for Cr12MoV steel that can optimize the compositional segregation and eutectic carbide state.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: to use a conventional heating furnace for pre-forging heating and heat preservation, and to use a diffusion heating furnace for heating and diffusion annealing of the billet between forging fires;

[0007] The furnace temperature of the diffusion heating furnace is controlled as follows: when the cumulative forging ratio of the billets entering the furnace is <2.0, the furnace temperature is controlled at 1160±5℃; when the cumulative forging ratio of the billets entering the furnace is 2.0≤ and <4.0, the furnace temperature is controlled at 1175±5℃; when the cumulative forging ratio of the billets entering the furnace is ≥4.0, the furnace temperature is controlled at 1190±5℃; when the cumulative forging ratio of the billets in the diffusion heating furnace is inconsistent, the furnace temperature is controlled according to the billet with the smallest cumulative forging ratio.

[0008] Furthermore, when the total number of billets N is even, after the first forging of the N / 2+1th billet is loaded into the diffusion heating furnace, the first billet loaded into the diffusion heating furnace is removed from the diffusion heating furnace and loaded into a conventional heating furnace for heating and heat preservation; when the total number of billets N is odd, after the first forging of the (N+1) / 2th billet is loaded into the diffusion heating furnace, the first billet loaded into the diffusion heating furnace is removed from the diffusion heating furnace and loaded into a conventional heating furnace for heating and heat preservation; subsequently, as each billet is loaded into the diffusion heating furnace, a billet is removed from the diffusion heating furnace in the order of loading into the diffusion heating furnace and loaded into a conventional heating furnace for heating and heat preservation; until the billet is forged to the final size; the furnace temperature of the conventional heating furnace is maintained at 1150±5℃.

[0009] Furthermore, the billet is held at a temperature of ≥2 hours after being loaded into a conventional heating furnace.

[0010] Furthermore, the final forging temperature of each forging pass is controlled to be ≥900℃.

[0011] The beneficial effects of adopting the above technical solution are as follows: In view of the characteristics of long forging time per forging and similar forging process when forging Cr12MoV steel in large batches, the present invention designs a forging process that combines two types of heating furnaces, namely conventional heating furnace and diffusion heating furnace, for heating and heat preservation. Under the condition of almost no change in the total forging time, the high-temperature diffusion annealing process is innovatively integrated into the forging process, which greatly improves the compositional segregation and eutectic carbide state of the billet, and successfully realizes efficient diffusion batch forging of Cr12MoV steel.

[0012] Compared to the traditional Cr12MoV steel forging process, which involves holding the steel at 1150℃ throughout the forging process, this invention significantly improves the compositional segregation and eutectic carbide state of the Cr12MoV forging billet due to the addition of gradient high-temperature diffusion annealing treatment. Compared to the traditional method of first high-temperature diffusion annealing and then forging, or first forging and then high-temperature diffusion annealing and then forging, this invention saves time and provides gradient high-temperature diffusion annealing treatment to improve the billet microstructure, resulting in a more significant improvement in the compositional segregation and eutectic carbide state of the billet.

[0013] To maximize the utilization of forging time per heat cycle, thereby improving the effect of high-temperature diffusion annealing and reducing compositional segregation and eutectic carbide state of the billet, this invention innovatively incorporates a furnace-turning process between heat cycles, sequentially transferring the billet from the diffusion heating furnace into a conventional heating furnace. This method almost evenly divides the forging reheating time into two parts: conventional heating and diffusion heating. This ensures the high-temperature diffusion annealing effect of the billet while minimizing the impact on the conventional heating and holding time, achieving high-efficiency forging of the billet. Attached Figure Description

[0014] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0015] Figure 1 This is a metallographic diagram of the Cr12MoV steel forging obtained in Example 1 of the present invention;

[0016] Figure 2 This is a metallographic diagram of a Cr12MoV steel forging obtained through conventional processes. Detailed Implementation

[0017] The high-efficiency diffusion batch forging method for this Cr12MoV steel employs two types of heating furnaces: conventional heating furnaces and diffusion heating furnaces, for heating and holding. The process includes pre-forging numbering, heating and holding, forging, and furnace pouring. The process details for each step are as follows:

[0018] 1) Pre-forging numbering: The batch forging refers to forging a group of billets as a batch. When loading the furnace, all billets in the batch are numbered to make it clearer and more identifiable during subsequent forging and furnace turning.

[0019] 2) Heating and heat preservation: All billets in this batch are heated in a conventional heating furnace. First, the conventional heating furnace is heated to 500-600℃ at a heating rate of 80-90℃ / h and held for 2-3 hours. Then, the conventional heating furnace is heated to 800-850℃ at a heating rate of 90-100℃ / h and held for 2-3 hours. Then, the conventional heating furnace is heated to 1150±5℃ at a heating rate of 100-120℃ / h and held for ≥2 hours, preferably 2-5 hours. Then, the billets are forged. During the forging process, the conventional heating furnace is kept at 1150±5℃ to heat and preserve the Cr12MoV billets before the inter-forging in the subsequent furnace turning process until the forging is completed. The hot working temperature range of the Cr12MoV steel is 900 to 1100℃. Therefore, the pre-forging holding temperature of the Cr12MoV steel billet is controlled at 1150±5℃ to ensure that the billet is in the optimal hot working temperature range during forging.

[0020] 3) Forging: During the first forging, one billet is taken out from the conventional heating furnace in sequence according to its number for forging. After each billet is forged, it is immediately sent to the diffusion heating furnace for heating and holding. During subsequent forging, each billet is forged in the order it was put into the conventional heating furnace. After each billet is forged, it is immediately sent to the diffusion heating furnace for heating and holding. During forging, the final forging temperature of each forging is controlled to be ≥900℃. After the billet is forged to the final size, it is immediately buried in a sand pit for slow cooling.

[0021] During the forging process, a diffusion heating furnace is used for heating and diffusion annealing of the billets between forging fires. The furnace temperature of the diffusion heating furnace is controlled as follows: when the cumulative forging ratio of the billets entering the furnace is <2.0, the furnace temperature is controlled at 1160±5℃; when the cumulative forging ratio of the billets entering the furnace is 2.0≤ and <4.0, the furnace temperature is controlled at 1175±5℃; when the cumulative forging ratio of the billets entering the furnace is ≥4.0, the furnace temperature is controlled at 1190±5℃; when the cumulative forging ratio of the billets in the diffusion heating furnace is inconsistent, the furnace temperature is calculated based on the billet with the smallest cumulative forging ratio.

[0022] Before forging, the Cr12MoV steel ingot exhibits severe compositional segregation in its as-cast microstructure. At high temperatures, areas with concentrated composition are prone to overheating, leading to material failure. Forging and high-temperature diffusion annealing are effective methods to reduce compositional segregation. The higher the cumulative forging ratio of the billet and the higher and longer the high-temperature diffusion annealing temperature, the better the effect on improving compositional segregation. During the forging process, as the number of forging passes increases, the cumulative forging ratio of the billet continuously increases, leading to a continuous improvement in the compositional segregation of the billet, and consequently, a continuous increase in the maximum acceptable diffusion annealing temperature of the billet. This method has been verified through multiple experiments. When Cr12MoV steel ingots are forged in a single firing and the cumulative forging ratio is <2.0, the furnace temperature of the diffusion heating furnace is controlled at 1160±5℃, allowing the billet to undergo high-temperature diffusion annealing at 1160±5℃. As the number of forging firings increases, when the cumulative forging ratio of the billet is 2.0≤4.0<4.0, the furnace temperature of the diffusion heating furnace is controlled at 1175±5℃, allowing the billet to undergo high-temperature diffusion annealing at 1175±5℃. As the number of forging firings increases, when the cumulative forging ratio of the billet is ≥4.0, the furnace temperature of the diffusion heating furnace is controlled at 1190±5℃, allowing the billet to undergo high-temperature diffusion annealing at 1190±5℃. This method can maximize the use of high-temperature diffusion annealing to improve compositional segregation and promote the re-dissolution of large blocky eutectic carbides while ensuring that the Cr12MoV steel billet does not suffer from overheating or burning failures.

[0023] 4) Furnace Reversal: The process of heating and holding the billet back and forth between a conventional heating furnace and a diffusion heating furnace during the forging process; The furnace reversal process is as follows: When the total number of billets N is even, after the first forging of the N / 2+1th billet is loaded into the diffusion heating furnace, the first billet loaded into the diffusion heating furnace is taken out of the diffusion heating furnace and loaded into the conventional heating furnace for heating and holding; When the total number of billets N is odd, after the first forging of the (N+1) / 2th billet is loaded into the diffusion heating furnace, the first billet loaded into the diffusion heating furnace is immediately taken out of the diffusion heating furnace and loaded into the conventional heating furnace for heating and holding; Subsequently, as each billet is loaded into the diffusion heating furnace, a billet is taken out from the diffusion heating furnace in the order of its entry into the diffusion heating furnace and loaded into the conventional heating furnace for heating and holding; until the billet is forged to the final size. The temperature of the conventional heating furnace is 1150±5℃. The billet is held in the conventional heating furnace for ≥2 hours each time it is poured into the conventional heating furnace. This ensures that the billet temperature drops to 1150±5℃ after being poured from the diffusion heating furnace into the conventional heating furnace, thus facilitating subsequent forging.

[0024] Example 1: The high-efficiency diffusion batch forging method of this Cr12MoV steel is described in detail below.

[0025] 1) Forge 12 Cr12MoV steel electroslag ingots with a diameter of φ300mm into Cr12MoV round bars with a diameter of φ100mm.

[0026] All Cr12MoV steel electroslag ingots were loaded into a conventional heating furnace at a furnace temperature of 100℃, and numbered 1#, 2#, 3#, 4#, 5#, 6#, 7#, 8#, 9#, 10#, 11#, and 12# according to the loading sequence. Then, the conventional heating furnace was started to heat up. First, the conventional heating furnace was heated to 500℃ at a heating rate of 80℃ / h and held for 2 hours; then, it was heated to 850℃ at a heating rate of 90℃ / h and held for 2 hours; then, it was heated to 1150℃ at a heating rate of 100℃ / h and held for 5 hours. This completes the heating process of the conventional heating furnace. Subsequently, until the forging process is completed, the conventional heating furnace is maintained at 1150℃.

[0027] 2) During the heating process of the conventional heating furnace, check the furnace temperature status of the diffusion heating furnace to ensure that the furnace temperature of the diffusion heating furnace is stable at 1160℃ when forging begins.

[0028] After holding the Cr12MoV steel electroslag ingot at 1150℃ for 2 hours in a conventional heating furnace, the No. 1 electroslag ingot was removed from the conventional heating furnace and forged. When the billet size reached 220mm×220mm and the temperature was 904℃, close to the final forging temperature of 900℃, the No. 1 billet was immediately sent to a diffusion heating furnace at 1160℃ for heating and holding. Then, the No. 2 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 220mm×220mm and the temperature was 906℃, close to the final forging temperature of 900℃, the No. 2 billet was immediately sent to a diffusion heating furnace at 1160℃ for heating and holding. Then, the #3 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 220mm × 220mm and the temperature was 907℃, close to the final forging temperature of 900℃, the #3 billet was immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Then, the #4 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 220mm × 220mm and the temperature was 901℃, close to the final forging temperature of 900℃, the #4 billet was immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Then, the #5 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 220mm × 220mm and the temperature was 905℃, close to the final forging temperature of 900℃, the #5 billet was immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Then, the No. 6 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 220mm × 220mm and the temperature was 902℃, close to the final forging temperature of 900℃, the No. 6 billet was immediately sent to a diffusion heating furnace at 1160℃ for heating and holding. Then, the No. 7 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 220mm × 220mm and the temperature was 905℃, close to the final forging temperature of 900℃, the No. 7 billet was immediately sent to a diffusion heating furnace at 1160℃ for heating and holding.

[0029] At this point, since billet #7 is the 12 / 2+1 billet, after it is heated and kept warm in a diffusion heating furnace at 1160℃, billet #1 is immediately taken out of the diffusion heating furnace and placed into a conventional heating furnace at 1150℃ for heating and keeping warm.

[0030] Then, the #8 electroslag ingot was removed from the conventional heating furnace and forged. It was forged to a billet size of 220mm × 220mm at a temperature of 903℃, close to the final forging temperature of 900℃. The #8 billet was immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Then, the #2 billet was immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Next, the #9 electroslag ingot was removed from the conventional heating furnace and forged. It was forged to a billet size of 220mm × 220mm at a temperature of 904℃, close to the final forging temperature of 900℃. The #9 billet was immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Then, the #3 billet was immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, the #10 electroslag ingot was removed from the conventional heating furnace and forged. It was forged to a billet size of 220mm × 220mm at a temperature of 905℃, close to the final forging temperature of 900℃. The #10 billet was immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Then, the #4 billet was immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Next, the #11 electroslag ingot was removed from the conventional heating furnace and forged. It was forged to a billet size of 220mm × 220mm at a temperature of 907℃, close to the final forging temperature of 900℃. The #11 billet was immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Then, the #5 billet was immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, the No. 12 electroslag ingot was taken out of the conventional heating furnace and forged. When the billet size was 220mm×220mm and the temperature was close to the final forging temperature of 900℃, the No. 12 billet was immediately sent to the diffusion heating furnace at 1160℃ for heating and heat preservation. Then, the No. 6 billet was immediately taken out of the diffusion heating furnace and put into the conventional heating furnace at 1150℃ for heating and heat preservation.

[0031] At this point, all 12 Cr12MoV electroslag ingots have completed their first forging. Since the holding time of billet #1 in the conventional heating furnace has not reached 2 hours, inter-forging holding is required.

[0032] After billet #1 has been held at a constant temperature in the conventional heating furnace for 2 hours, it is removed and forged. When the billet reaches a size of 180mm × 180mm and the temperature is close to the final forging temperature of 900℃ (909℃), billet #1 is immediately transferred to a diffusion heating furnace at 1160℃ for further heating and holding. Then, billet #7 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Next, billet #2 is removed from the conventional heating furnace and forged. Similarly, when the billet reaches a size of 180mm × 180mm and the temperature is close to the final forging temperature of 900℃ (902℃), billet #2 is immediately transferred to a diffusion heating furnace at 1160℃ for further heating and holding. Then, billet #8 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for further heating and holding. Then, billet #3 is removed from the conventional heating furnace and forged. It is forged to a size of 180mm × 180mm at a temperature of 905℃, close to the final forging temperature of 900℃. Billet #3 is then immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Billet #9 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Billet #4 is then removed from the conventional heating furnace and forged. It is forged to a size of 180mm × 180mm at a temperature of 905℃, close to the final forging temperature of 900℃. Billet #4 is then immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Billet #10 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, billet #5 is removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm and a temperature of 904℃, close to the final forging temperature of 900℃. Billet #5 is then immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Billet #11 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Billet #6 is then removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm and a temperature of 908℃, close to the final forging temperature of 900℃. Billet #6 is then immediately transferred to a diffusion heating furnace at 1160℃ for heating and holding. Billet #12 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding.

[0033] 3) At this point, the billets in the diffusion heating furnace are #1, #2, #3, #4, #5, and #6, and their cumulative forging ratio is approximately (3.14×150×150) / (180×180)≈2.18. Therefore, the furnace temperature of the diffusion heating furnace is immediately increased to 1175℃. At this time, since the holding time of billet #7 in the conventional heating furnace has not reached 2 hours, inter-fire holding is required.

[0034] After the No. 7 billet has been held in the conventional heating furnace for 2 hours, it is taken out of the conventional heating furnace and forged. When the billet size is 180mm×180mm and the temperature is close to the final forging temperature of 900℃, the No. 7 billet is immediately sent to the diffusion heating furnace at 1175℃ for heating and holding. Then, the No. 1 billet is immediately taken out of the diffusion heating furnace and placed in the conventional heating furnace at 1150℃ for heating and holding. Then, billet #8 is removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm. Billet #5 is then removed from the conventional heating furnace and forged until it reaches a size of 140mm × 140mm, at a temperature of 907℃, close to the final forging temperature of 900℃. Billet #5 is immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Billet #11 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Billet #6 is then removed from the conventional heating furnace and forged until it reaches a size of 140mm × 140mm, at a temperature of 903℃, close to the final forging temperature of 900℃. Billet #6 is then immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Billet #12 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding.

[0035] At this point, since the No. 7 billet has not been kept in the conventional heating furnace for 2 hours, it is necessary to keep it in the furnace between heating cycles.

[0036] After the No. 7 billet has been held at a constant temperature in the conventional heating furnace for 2 hours, it is removed and forged. When the billet reaches a size of 140mm × 140mm and the temperature is close to the final forging temperature of 900℃ (905℃), the No. 7 billet is immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Then, the No. 1 billet is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Next, the No. 8 billet is removed from the conventional heating furnace and forged. Similarly, when the billet reaches a size of 140mm × 140mm and the temperature is close to the final forging temperature of 900℃ (904℃), the No. 8 billet is immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Then, the No. 2 billet is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, billet #9 was removed from the conventional heating furnace and forged until it reached a size of 140mm × 140mm, at a temperature of 907℃, close to the final forging temperature of 900℃. Billet #9 was then immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Billet #3 was then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Billet #10 was then removed from the conventional heating furnace and forged until it reached a size of 140mm × 140mm, at a temperature of 910℃, close to the final forging temperature of 900℃. Billet #10 was then immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Billet #4 was then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, billet #11 was removed from the conventional heating furnace and forged until it reached a size of 140mm × 140mm, at a temperature of 904℃, close to the final forging temperature of 900℃. Billet #11 was then immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Billet #5 was then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Billet #12 was then removed from the conventional heating furnace and forged until it reached a size of 140mm × 140mm, at a temperature of 901℃, close to the final forging temperature of 900℃. Billet #12 was then immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Billet #6 was then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding.

[0037] At this point, all 12 Cr12MoV electroslag ingots have completed their third forging. Since the holding time of billet #1 in the conventional heating furnace has not reached 2 hours, inter-forging holding is required.

[0038] After billet #1 has been held at a constant temperature in the conventional heating furnace for 2 hours, it is removed and forged until it reaches a size of 110mm × 110mm and a temperature of 905℃, close to the final forging temperature of 900℃. Billet #1 is then immediately transferred to a diffusion heating furnace at 1175℃ for further heating and holding. Billet #7 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Billet #2 is then removed from the conventional heating furnace and forged until it reaches a size of 110mm × 110mm and a temperature of 909℃, close to the final forging temperature of 900℃. Billet #2 is then immediately transferred to a diffusion heating furnace at 1175℃ for further heating and holding. Billet #8 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for further heating and holding. Then, billet #3 was removed from the conventional heating furnace and forged until it reached a size of 110mm × 110mm, at a temperature of 906℃, close to the final forging temperature of 900℃. Billet #3 was then immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Billet #9 was then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Billet #4 was then removed from the conventional heating furnace and forged until it reached a size of 110mm × 110mm, at a temperature of 907℃, close to the final forging temperature of 900℃. Billet #4 was then immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Billet #10 was then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, billet #5 is removed from the conventional heating furnace and forged. It is forged to a size of 110mm × 110mm at a temperature of 902℃, close to the final forging temperature of 900℃. Billet #5 is then immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Billet #11 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Billet #6 is then removed from the conventional heating furnace and forged. It is forged to a size of 110mm × 110mm at a temperature of 906℃, close to the final forging temperature of 900℃. Billet #6 is then immediately transferred to a diffusion heating furnace at 1175℃ for heating and holding. Billet #12 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding.

[0039] 4) At this point, the billets in the diffusion heating furnace are #1, #2, #3, #4, #5, and #6, and their cumulative forging ratio is (3.14×150×150) / (110×110)≈5.84. Therefore, the furnace temperature of the diffusion heating furnace is immediately raised to 1190℃. At this time, since the holding time of billet #7 in the conventional heating furnace has not reached 2 hours, inter-fire holding is required.

[0040] After the No. 7 billet has been held at a constant temperature in the conventional heating furnace for 2 hours, it is removed and forged. When the billet reaches a size of 110mm × 110mm and the temperature is close to the final forging temperature of 900℃ (903℃), the No. 7 billet is immediately transferred to a diffusion heating furnace at 1190℃ for heating and holding. Then, the No. 1 billet is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Next, the No. 8 billet is removed from the conventional heating furnace and forged. Similarly, when the billet reaches a size of 110mm × 110mm and the temperature is close to the final forging temperature of 900℃ (902℃), the No. 8 billet is immediately transferred to a diffusion heating furnace at 1190℃ for heating and holding. Then, the No. 2 billet is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, billet #9 was removed from the conventional heating furnace and forged until it reached a size of 110mm × 110mm and a temperature of 907℃, close to the final forging temperature of 900℃. Billet #9 was then immediately transferred to a diffusion heating furnace at 1190℃ for heating and holding. Billet #3 was then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Billet #10 was then removed from the conventional heating furnace and forged until it reached a size of 110mm × 110mm and a temperature of 904℃. Billet #10 was then immediately transferred to a diffusion heating furnace at 1190℃ for heating and holding. Billet #4 was then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, billet #11 is removed from the conventional heating furnace and forged. It is forged to a size of 110mm × 110mm at a temperature of 907℃, close to the final forging temperature of 900℃. Billet #11 is then immediately transferred to a diffusion heating furnace at 1190℃ for heating and holding. Billet #5 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Billet #12 is then removed from the conventional heating furnace and forged. It is forged to a size of 110mm × 110mm at a temperature of 902℃, close to the final forging temperature of 900℃. Billet #12 is then immediately transferred to a diffusion heating furnace at 1190℃ for heating and holding. Billet #6 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding.

[0041] At this point, all 12 Cr12MoV electroslag ingots have completed their fourth forging. Since the holding time of billet #1 in the conventional heating furnace has not reached 2 hours, inter-forging holding is required.

[0042] After the holding time of billet #1 in the conventional heating furnace reaches 2 hours, billet #1 is removed from the conventional heating furnace and forged until the billet size is φ100mm. The forging of billet #1 is then completed, and it is immediately buried in a sand pit for slow cooling. Next, billet #7 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, billet #2 is removed from the conventional heating furnace and forged until the billet size is φ100mm. The forging of billet #2 is then completed, and it is immediately buried in a sand pit for slow cooling. Finally, billet #8 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, billet #3 is removed from the conventional heating furnace and forged until it reaches a size of φ100mm. It is then immediately buried in a sand pit for slow cooling. Next, billet #9 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, billet #4 is removed from the conventional heating furnace and forged until it reaches a size of φ100mm. It is then immediately buried in a sand pit for slow cooling. Next, billet #10 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, billet #5 is removed from the conventional heating furnace and forged until it reaches a size of φ100mm. It is then immediately buried in a sand pit for slow cooling. Next, billet #11 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and holding. Then, the No. 6 billet is taken out from the conventional heating furnace and forged. When the billet size is φ100mm, the forging of the No. 6 billet is completed and it is immediately buried in the sand pit for slow cooling. Then, the No. 12 billet is immediately taken out from the diffusion heating furnace and placed in a conventional heating furnace at 1150℃ for heating and heat preservation.

[0043] At this point, since the No. 7 billet has not been kept in the conventional heating furnace for 2 hours, it is necessary to keep it in the furnace between heating cycles.

[0044] After the No. 7 billet has been held at a constant temperature in the conventional heating furnace for 2 hours, it is removed and forged until it reaches a diameter of φ100mm. The forging process is then complete, and the billet is immediately buried in a sand pit for slow cooling. Next, the No. 8 billet is removed from the conventional heating furnace and forged until it reaches a diameter of φ100mm. The billet is then immediately buried in a sand pit for slow cooling. Finally, the No. 10 billet is removed from the conventional heating furnace and forged until it reaches a diameter of φ100mm. Then, billet #11 was removed from the conventional heating furnace and forged until it reached a size of φ100mm. The forging of billet #11 was then completed, and it was immediately buried in a sand pit for slow cooling. Similarly, billet #12 was removed from the conventional heating furnace and forged until it reached a size of φ100mm. The forging of billet #12 was then completed, and it was immediately buried in a sand pit for slow cooling.

[0045] 5) At this point, the forging process of all 12 Cr12MoV steel electroslag ingots is complete. Figure 1 The metallographic structure of the Cr12MoV steel forging obtained in this embodiment is shown below. Figure 2 The microstructure of Cr12MoV steel forgings obtained using conventional forging technology (forging at 1150℃ with holding temperature) is shown. (Comparison) Figure 1 , Figure 2 It can be observed that this method can effectively improve the compositional segregation of the billet, promote the re-dissolution of large eutectic carbides, and make the eutectic carbides fine and rounded, thereby improving product quality.

[0046] Example 2: The high-efficiency diffusion batch forging method of this Cr12MoV steel is described in detail below.

[0047] 1) Forge 15 Cr12MoV steel electroslag ingots with a diameter of φ400mm into Cr12MoV round bars with a diameter of φ120mm.

[0048] All Cr12MoV steel electroslag ingots were loaded into a conventional heating furnace at a furnace temperature of 50℃, and numbered 1#, 2#, 3#, 4#, 5#, 6#, 7#, 8#, 9#, 10#, 11#, 12#, 13#, 14#, and 15# according to the loading sequence. Then, the conventional heating furnace was started to heat up. First, the conventional heating furnace was heated to 600℃ at a heating rate of 90℃ / h and held for 3 hours; then, it was heated to 800℃ at a heating rate of 100℃ / h and held for 3 hours; then, it was heated to 1155℃ at a heating rate of 120℃ / h and held for 2 hours. This completes the heating process of the conventional heating furnace. Subsequently, until the forging process is completed, the conventional heating furnace is maintained at 1150±5℃.

[0049] 2) During the heating process of the conventional heating furnace, check the furnace temperature status of the diffusion heating furnace to ensure that the furnace temperature is stable at 1158℃ when the forging begins, and control the furnace temperature at 1160±5℃ thereafter.

[0050] After holding the Cr12MoV steel electroslag ingot at 1150℃ for 3 hours in a conventional heating furnace, the No. 1 electroslag ingot was removed from the conventional heating furnace and forged. When the billet size reached 300mm×300mm, the temperature was 904℃, close to the lower limit of the final forging temperature of 900℃. The No. 1 billet was immediately sent to a diffusion heating furnace for heating and holding. Then, the No. 2 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 300mm×300mm, the temperature was 903℃, close to the lower limit of the final forging temperature of 900℃. The No. 2 billet was immediately sent to a diffusion heating furnace for heating and holding. Then, the No. 3 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 300mm×300mm, the temperature was 903℃, close to the lower limit of the final forging temperature of 900℃. The No. 3 billet was immediately sent to a diffusion heating furnace for heating and holding. Then, the #4 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 300mm × 300mm and the temperature was 906℃, close to the final forging lower limit of 900℃, the #4 billet was immediately transferred to a diffusion heating furnace for heating and holding. Then, the #5 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 300mm × 300mm and the temperature was 907℃, close to the final forging lower limit of 900℃, the #5 billet was immediately transferred to a diffusion heating furnace for heating and holding. Then, the #6 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size reached 300mm × 300mm and the temperature was 902℃, close to the final forging lower limit of 900℃, the #6 billet was immediately transferred to a diffusion heating furnace for heating and holding. Then, the No. 7 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size was 300mm × 300mm and the temperature reached 903℃, close to the lower limit of the final forging temperature of 900℃, the No. 7 billet was immediately sent to a diffusion heating furnace for heating and holding. Then, the No. 8 electroslag ingot was removed from the conventional heating furnace and forged. Similarly, when the billet size was 300mm × 300mm and the temperature reached 904℃, close to the lower limit of the final forging temperature of 900℃, the No. 8 billet was immediately sent to a diffusion heating furnace for heating and holding.

[0051] At this point, since billet #8 is the (15+1) / 2nd billet, after it is heated and kept warm in a diffusion heating furnace at 1158℃, billet #1 is immediately taken out of the diffusion heating furnace and put into a conventional heating furnace at 1150℃ for heating and keeping warm.

[0052] Then, the #9 electroslag ingot was removed from the conventional heating furnace and forged. It was forged to a billet size of 300mm × 300mm, with a temperature of 907℃, close to the final forging lower limit of 900℃. The #9 billet was immediately transferred to a diffusion heating furnace for heating and holding. Then, the #2 billet was immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Next, the #10 electroslag ingot was removed from the conventional heating furnace and forged. It was forged to a billet size of 300mm × 300mm, with a temperature of 905℃, close to the final forging lower limit of 900℃. The #10 billet was immediately transferred to a diffusion heating furnace for heating and holding. Then, the #3 billet was immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, the #11 electroslag ingot was removed from the conventional heating furnace and forged. It was forged to a billet size of 300mm × 300mm, with a temperature of 905℃, close to the final forging lower limit of 900℃. The #11 billet was immediately transferred to a diffusion heating furnace for heating and holding. Then, the #4 billet was immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Next, the #12 electroslag ingot was removed from the conventional heating furnace and forged. It was forged to a billet size of 300mm × 300mm, with a temperature of 903℃, close to the final forging lower limit of 900℃. The #12 billet was immediately transferred to a diffusion heating furnace for heating and holding. Then, the #5 billet was immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, the #13 electroslag ingot was removed from the conventional heating furnace and forged. It was forged to a billet size of 300mm × 300mm, with a temperature of 906℃, close to the final forging lower limit of 900℃. The #13 billet was immediately transferred to a diffusion heating furnace for heating and holding. Then, the #6 billet was immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Next, the #14 electroslag ingot was removed from the conventional heating furnace and forged. It was forged to a billet size of 300mm × 300mm, with a temperature of 908℃, close to the final forging lower limit of 900℃. The #14 billet was immediately transferred to a diffusion heating furnace for heating and holding. Then, the #7 billet was immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, the No. 15 electroslag ingot was taken out of the conventional heating furnace and forged. When the billet size was 300mm×300mm and the temperature was close to the lower limit of the final forging temperature of 900℃, the No. 15 billet was immediately sent to the diffusion heating furnace for heating and heat preservation. Then, the No. 8 billet was immediately taken out of the diffusion heating furnace and put into the conventional heating furnace for heating and heat preservation.

[0053] At this point, all 15 Cr12MoV electroslag ingots had completed their first forging. The No. 1 billet had been held in the conventional heating furnace for 2 hours and could then proceed with forging.

[0054] Billet #1 was removed from the conventional heating furnace and forged until it reached a size of 240mm × 240mm, at a temperature of 906℃, close to the lower limit of the final forging temperature of 900℃. Billet #1 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #9 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #2 was then removed from the conventional heating furnace and forged until it reached a size of 240mm × 240mm, at a temperature of 909℃, close to the lower limit of the final forging temperature of 900℃. Billet #2 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #10 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #3 was removed from the conventional heating furnace and forged until it reached a size of 240mm × 240mm, at a temperature of 911℃, close to the lower limit of the final forging temperature of 900℃. Billet #3 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #11 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #4 was then removed from the conventional heating furnace and forged until it reached a size of 240mm × 240mm, at a temperature of 907℃, close to the lower limit of the final forging temperature of 900℃. Billet #4 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #12 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #5 is removed from the conventional heating furnace and forged until it reaches a size of 240mm × 240mm and a temperature of 908℃, close to the lower limit of the final forging temperature of 900℃. Billet #5 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #13 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #6 is then removed from the conventional heating furnace and forged until it reaches a size of 240mm × 240mm and a temperature of 901℃, close to the lower limit of the final forging temperature of 900℃. Billet #6 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #14 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, the No. 7 billet was taken out of the conventional heating furnace and forged. When the billet size was 240mm×240mm and the temperature was close to the lower limit of the final forging temperature of 900℃, the No. 7 billet was immediately sent to the diffusion heating furnace for heating and heat preservation. Then, the No. 15 billet was immediately taken out of the diffusion heating furnace and put into the conventional heating furnace for heating and heat preservation.

[0055] 3) At this point, the billets in the diffusion heating furnace are #1, #2, #3, #4, #5, #6, and #7, and their cumulative forging ratio is approximately (3.14×200×200) / (240×240)≈2.18. Therefore, the furnace temperature of the diffusion heating furnace is immediately raised to 1177℃, and the subsequent furnace temperature is controlled at 1175±5℃. At this time, the holding time of billet #8 in the conventional heating furnace has reached 2 hours, and forging can continue.

[0056] Billet #8 was removed from the conventional heating furnace and forged until it reached a size of 240mm × 240mm, at a temperature of 906℃, close to the lower limit of the final forging temperature of 900℃. Billet #8 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #1 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #9 was then removed from the conventional heating furnace and forged until it reached a size of 240mm × 240mm, at a temperature of 907℃, close to the lower limit of the final forging temperature of 900℃. Billet #9 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #2 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #10 is removed from the conventional heating furnace and forged until it reaches a size of 240mm × 240mm and a temperature of 904℃, close to the lower limit of the final forging temperature of 900℃. Billet #10 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #3 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #11 is then removed from the conventional heating furnace and forged until it reaches a size of 240mm × 240mm and a temperature of 905℃, close to the lower limit of the final forging temperature of 900℃. Billet #11 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #4 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #12 is removed from the conventional heating furnace and forged. It is forged to a size of 240mm × 240mm, with a temperature of 902℃, close to the lower limit of the final forging temperature (900℃). Billet #12 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #5 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Billet #13 is then removed from the conventional heating furnace and forged. It is forged to a size of 240mm × 240mm, with a temperature of 907℃, close to the lower limit of the final forging temperature (900℃). Billet #13 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #6 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Then, billet #14 was removed from the conventional heating furnace and forged until it reached a size of 240mm × 240mm, at a temperature of 903℃, close to the lower limit of the final forging temperature of 900℃. Billet #14 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #7 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #15 was then removed from the conventional heating furnace and forged until it reached a size of 240mm × 240mm, at a temperature of 905℃, close to the lower limit of the final forging temperature of 900℃. Billet #15 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #8 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding.

[0057] At this point, all 15 Cr12MoV electroslag ingots had completed their second forging. The No. 1 billet had been held in the conventional heating furnace for 2 hours and could then be forged further.

[0058] Billet #1 was removed from the conventional heating furnace and forged until it reached a size of 180mm × 180mm, at a temperature of 904℃, close to the lower limit of the final forging temperature of 900℃. Billet #1 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #9 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #2 was then removed from the conventional heating furnace and forged until it reached a size of 180mm × 180mm, at a temperature of 901℃, close to the lower limit of the final forging temperature of 900℃. Billet #2 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #10 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #3 is removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm and a temperature of 905℃, close to the lower limit of the final forging temperature of 900℃. Billet #3 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #11 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #4 is then removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm and a temperature of 909℃, close to the lower limit of the final forging temperature of 900℃. Billet #4 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #12 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #5 is removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm and a temperature of 903℃, close to the lower limit of the final forging temperature of 900℃. Billet #5 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #13 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #6 is then removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm and a temperature of 910℃, close to the lower limit of the final forging temperature of 900℃. Billet #6 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #14 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #7 is removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm and a temperature of 906℃, close to the lower limit of the final forging temperature of 900℃. Billet #7 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #15 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #8 is then removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm and a temperature of 905℃, close to the lower limit of the final forging temperature of 900℃. Billet #8 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #1 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding.Then, billet #9 is removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm and a temperature of 903℃, close to the lower limit of the final forging temperature of 900℃. Billet #9 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #2 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #10 is then removed from the conventional heating furnace and forged until it reaches a size of 180mm × 180mm and a temperature of 907℃, close to the lower limit of the final forging temperature of 900℃. Billet #10 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #3 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #11 was removed from the conventional heating furnace and forged until it reached a size of 180mm × 180mm, at a temperature of 904℃, close to the lower limit of the final forging temperature of 900℃. Billet #11 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #4 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #12 was then removed from the conventional heating furnace and forged until it reached a size of 180mm × 180mm, at a temperature of 909℃, close to the lower limit of the final forging temperature of 900℃. Billet #12 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #5 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #13 was removed from the conventional heating furnace and forged until it reached a size of 180mm × 180mm, at a temperature of 907℃, close to the lower limit of the final forging temperature of 900℃. Billet #13 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #6 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #14 was then removed from the conventional heating furnace and forged until it reached a size of 180mm × 180mm, at a temperature of 904℃, close to the lower limit of the final forging temperature of 900℃. Billet #14 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #7 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, the No. 15 billet was taken out of the conventional heating furnace and forged. When the billet size was 180mm×180mm and the temperature was close to the lower limit of the final forging temperature of 900℃, the No. 15 billet was immediately sent to the diffusion heating furnace for heating and heat preservation. Then, the No. 8 billet was immediately taken out of the diffusion heating furnace and put into the conventional heating furnace for heating and heat preservation.

[0059] At this point, all 15 Cr12MoV electroslag ingots had completed their third forging. The No. 1 billet had been held in the conventional heating furnace for 2 hours and could then be forged further.

[0060] Billet #1 was removed from the conventional heating furnace and forged until it reached a size of 140mm × 140mm, at a temperature of 907℃, close to the lower limit of the final forging temperature of 900℃. Billet #1 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #9 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #2 was then removed from the conventional heating furnace and forged until it reached a size of 140mm × 140mm, at a temperature of 906℃, close to the lower limit of the final forging temperature of 900℃. Billet #2 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #10 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #3 was removed from the conventional heating furnace and forged. Forging continued until the billet size reached 140mm × 140mm, with a temperature of 904℃, close to the lower limit of the final forging temperature of 900℃. Billet #3 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #11 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #4 was then removed from the conventional heating furnace and forged. Forging continued until the billet size reached 140mm × 140mm, with a temperature of 907℃, close to the lower limit of the final forging temperature of 900℃. Billet #4 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #12 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #5 is removed from the conventional heating furnace and forged until it reaches a size of 140mm × 140mm and a temperature of 905℃, close to the lower limit of the final forging temperature of 900℃. Billet #5 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #13 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #6 is then removed from the conventional heating furnace and forged until it reaches a size of 140mm × 140mm and a temperature of 910℃, close to the lower limit of the final forging temperature of 900℃. Billet #6 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #14 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, the No. 7 billet was taken out of the conventional heating furnace and forged. When the billet size was 140mm×140mm and the temperature was close to the lower limit of the final forging temperature of 900℃, the No. 7 billet was immediately sent to the diffusion heating furnace for heating and heat preservation. Then, the No. 15 billet was immediately taken out of the diffusion heating furnace and put into the conventional heating furnace for heating and heat preservation.

[0061] 4) At this point, the billets in the diffusion heating furnace are #1, #2, #3, #4, #5, #6, and #7, and their cumulative forging ratio is (3.14×200×200) / (140×140)≈6.4. Therefore, the furnace temperature of the diffusion heating furnace is immediately raised to 1193℃, and the subsequent furnace temperature is controlled at 1190±5℃. At this time, the holding time of billet #8 in the conventional heating furnace has reached 2 hours, and forging can continue.

[0062] Billet #8 was removed from the conventional heating furnace and forged until it reached a size of 140mm × 140mm, at a temperature of 912℃, close to the lower limit of the final forging temperature of 900℃. Billet #8 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #1 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #9 was then removed from the conventional heating furnace and forged until it reached a size of 140mm × 140mm, at a temperature of 906℃, close to the lower limit of the final forging temperature of 900℃. Billet #9 was then immediately transferred to a diffusion heating furnace for heating and holding. Billet #2 was then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #10 is removed from the conventional heating furnace and forged. It is forged to a size of 140mm × 140mm, with a temperature of 904℃, close to the lower limit of the final forging temperature (900℃). Billet #10 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #3 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Billet #11 is then removed from the conventional heating furnace and forged. It is forged to a size of 140mm × 140mm, with a temperature of 909℃, close to the lower limit of the final forging temperature (900℃). Billet #11 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #4 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Then, billet #12 is removed from the conventional heating furnace and forged until it reaches a size of 140mm × 140mm, at a temperature of 907℃, close to the lower limit of the final forging temperature of 900℃. Billet #12 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #5 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #13 is then removed from the conventional heating furnace and forged until it reaches a size of 140mm × 140mm, at a temperature of 902℃, close to the lower limit of the final forging temperature of 900℃. Billet #13 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #6 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Then, billet #14 is removed from the conventional heating furnace and forged until it reaches a size of 140mm × 140mm, at a temperature of 905℃, close to the lower limit of the final forging temperature of 900℃. Billet #14 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #7 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding. Billet #15 is then removed from the conventional heating furnace and forged until it reaches a size of 140mm × 140mm, at a temperature of 903℃, close to the lower limit of the final forging temperature of 900℃. Billet #15 is then immediately transferred to a diffusion heating furnace for heating and holding. Billet #8 is then immediately removed from the diffusion heating furnace and placed into a conventional heating furnace for heating and holding.

[0063] At this point, all 15 Cr12MoV electroslag ingots had completed their fourth forging. The No. 1 billet had been held in the conventional heating furnace for 2 hours and could then be forged further.

[0064] Billet #1 is removed from the conventional heating furnace and forged until it reaches a size of φ120mm. It is then immediately buried in a sand pit for slow cooling. Billet #9 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Billet #2 is then removed from the conventional heating furnace and forged until it reaches a size of φ120mm. It is then immediately buried in a sand pit for slow cooling. Billet #10 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Billet #3 is then removed from the conventional heating furnace and forged until it reaches a size of φ120mm. It is then immediately buried in a sand pit for slow cooling. Billet #11 is then immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Then, billet #4 is removed from the conventional heating furnace and forged until it reaches a size of φ120mm. It is then immediately buried in a sand pit for slow cooling. Next, billet #12 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Then, billet #5 is removed from the conventional heating furnace and forged until it reaches a size of φ120mm. It is then immediately buried in a sand pit for slow cooling. Next, billet #13 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Then, billet #6 is removed from the conventional heating furnace and forged until it reaches a size of φ120mm. It is then immediately buried in a sand pit for slow cooling. Next, billet #14 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Then, billet #7 is removed from the conventional heating furnace and forged until it reaches a size of φ120mm. It is then immediately buried in a sand pit for slow cooling. Next, billet #15 is immediately removed from the diffusion heating furnace and placed in a conventional heating furnace for heating and holding. Billet #8 is then removed from the conventional heating furnace and forged until it reaches a size of φ120mm. It is then immediately buried in a sand pit for slow cooling. Billet #9 is then removed from the conventional heating furnace and forged until it reaches a size of φ120mm. It is then immediately buried in a sand pit for slow cooling. Finally, billet #10 is removed from the conventional heating furnace and forged until it reaches a size of φ120mm. It is then immediately buried in a sand pit for slow cooling. Then, billet #11 was removed from the conventional heating furnace and forged until it reached a size of φ120mm. The forging of billet #11 was then completed, and it was immediately buried in a sand pit for slow cooling. Similarly, billet #12 was removed from the conventional heating furnace and forged until it reached a size of φ120mm. The forging of billet #12 was then completed, and it was immediately buried in a sand pit for slow cooling.Then, billet #13 was removed from the conventional heating furnace and forged until it reached a size of φ120mm. The forging process was then completed, and the billet was immediately buried in a sand pit for slow cooling. Next, billet #14 was removed from the conventional heating furnace and forged until it reached a size of φ120mm. The billet was then immediately buried in a sand pit for slow cooling. Finally, billet #15 was removed from the conventional heating furnace and forged until it reached a size of φ120mm. The billet was then immediately buried in a sand pit for slow cooling.

[0065] At this point, the forging of all 15 Cr12MoV steel electroslag ingots was completed. This method can effectively improve the compositional segregation of the billet, promote the re-dissolution of large eutectic carbides, and make the eutectic carbides fine and rounded, thereby improving product quality.

Claims

1. A high-efficiency forging method of a Cr12MoV steel, characterized in that: It adopts a conventional heating furnace for pre-forging heating and holding, and a diffusion heating furnace for heating and diffusion annealing of the blank between forging passes; The furnace temperature control of the diffusion heating furnace is as follows: when the cumulative forging ratio of the blank entering the furnace is < 2.0, the furnace temperature is controlled at 1160±5℃; when the cumulative forging ratio of the blank entering the furnace is 2.0≤cumulative forging ratio<4.0, the furnace temperature is controlled at 1175±5℃; when the cumulative forging ratio of the blank entering the furnace is ≥4.0, the furnace temperature is controlled at 1190±5℃; when the cumulative forging ratios of the blanks in the diffusion heating furnace are inconsistent, the furnace temperature is controlled according to the blank with the smallest cumulative forging ratio.

2. The efficient high frequency forging and diffusion batch forging method of Cr12MoV steel according to claim 1, characterized in that: When the total number of blanks N is even, the first to N / 2+1 blanks are loaded into the diffusion heating furnace, then the first blank loaded into the diffusion heating furnace is taken out from the diffusion heating furnace and loaded into the conventional heating furnace for heating and holding; when the total number of blanks N is odd, the first to (N+1) / 2 blanks are loaded into the diffusion heating furnace, then the first blank loaded into the diffusion heating furnace is taken out from the diffusion heating furnace and loaded into the conventional heating furnace for heating and holding; subsequently, one blank is loaded into the diffusion heating furnace and one blank is taken out from the diffusion heating furnace according to the loading order for heating and holding in the conventional heating furnace; until the blank is forged to the final size; the furnace temperature of the conventional heating furnace is kept at 1150±5℃.

3. The efficient high frequency batch forging method of Cr12MoV steel according to claim 2, characterized in that: The holding time of the blank in the conventional heating furnace is ≥2h.

4. The high-efficiency batch forging method of Cr12MoV steel according to claim 1, 2 or 3, characterized in that: The final forging temperature of each pass is controlled to be ≥900℃.

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