Plasticizing anti-cracking forging method for high alloy steel ingot

Abstract

The invention relates to a plasticizing anti-cracking forging method for a high alloy steel ingot. The steel ingot is heated at a low speed, and high-temperature homogenization diffusion annealing treatment is carried out during heating and heat preservation before upsetting, so that segregation of chemical components and microscopic structures is relieved or eliminated; an upsetting leakage disc and an upper cover plate are preheated, too fast cooling caused by heat transfer is prevented, the upsetting deformation rate is controlled, deformation is uniform, stress concentration is reduced, and upsetting cracking is avoided; the wide anvil is preheated when the wide anvil is lengthened, and two new processes are designed, the first process is continuous forging two times in the same direction, the second process is forging one time, then turning over by 180 degrees and forging one time, turning over by 90 degrees and forging the other direction, the deformation amount of each time is 7-10%, the circulation is repeated, each time is started from the nozzle end to the riser end, and the total deformation amount of the two times is 14-20%. Equivalently, compared with the original process, the total deformation of the square blank section in the same direction is not changed, and the high alloy steel has time to recover or recrystallize by using self heat in two times, so that internal stress is eliminated, plasticity is recovered, and plastification and crack resistance are realized.

Description

Technical Field

[0001] This invention relates to the field of forging technology, specifically a method for forging high alloy steel ingots to enhance plasticity and resist cracking. Background Technology

[0002] High-alloy steels, due to the addition of a large number of alloying elements, improve mechanical properties and heat resistance, but significantly reduce process plasticity. High alloying causes severe segregation in the ingot, forming coarse columnar crystals. Because a large number of alloying elements are concentrated in the grain boundary regions, the grain boundary strength is lower than the intragranular strength at high temperatures. Simultaneously, many strengthening phase particles, such as carbides and borides, do not completely dissolve into the solid solution within the deformation temperature range. This means that in addition to the γ phase, strengthening phases also participate in deformation; that is, deformation does not occur in a single-phase state. Therefore, the process plasticity of alloy steel ingots is relatively low at high temperatures. Cracks often easily form along grain boundaries at weak points in the primary dendrite grain boundaries. Due to dendritic segregation, the alloying element content is low in the early crystallized parts and high in the later crystallized dendrite edges. Therefore, carbides and intermetallic compounds concentrate in the dendrite edges, thus reducing the alloy's forgeability.

[0003] Meanwhile, the slow recrystallization rate and high temperature of high-alloy steel result in higher deformation resistance at deformation temperatures. These characteristics make it prone to the formation of low-melting-point substances at grain boundaries during heating, especially at excessively high temperatures. In some austenitic steels, this can lead to the formation of the δ phase, while in ferritic steels, there is a risk of excessive grain growth. Therefore, the initial forging temperature of high-alloy steel is generally not higher than that of carbon steel, but the final forging temperature is higher. This is because high-alloy steel has a higher recrystallization temperature, higher deformation resistance, and lower plasticity than carbon steel, making it unsuitable for excessively low final forging temperatures. These factors combined result in a narrower forging temperature range for high-alloy steel compared to carbon steel.

[0004] In the existing technology, when forging high alloy steel ingots, the wide anvil is used to forge the length of the steel ingot. After one forging pass, the ingot is flipped 90 degrees and forged in another direction. Each forging pass results in a deformation amount of 14-20%, which is not conducive to increasing the speed of crack resistance.

[0005] Chinese Patent Application No. 202110200835.1 discloses a closed-loop forging method and tooling for improving the performance of high-alloy steel forgings. Belonging to the field of closed-loop forging technology, it solves the technical problem of poor grain uniformity and difficulty in meeting requirements in forgings prepared using existing forging methods. The method includes: Step 1, performing open forging on the billet; Step 2, after open forging, performing a first forging heat treatment, followed by furnace reheating; Step 3, assembling the closed-loop forging tooling; Step 4, placing the reheated billet inside the closed-loop forging tooling; Step 5, performing closed-loop upsetting treatment on the billet inside the closed-loop forging tooling; Step 6, directly producing the finished product after closed-loop upsetting treatment. Compared with free forging, the closed-loop forging method provided by this invention results in less billet cooling, better stress state, better billet surface quality, and less susceptibility to cracks. This patent describes a forming process for billets after large-deformation forging. However, large-deformation forging of billets makes them more prone to cracking, which the patent does not address. Furthermore, the method provided by this patent requires specialized closed-loop forging fixtures, increasing costs.

[0006] Chinese patent application number 202111581668.6 discloses a high-carbon high-alloy steel product and its preparation method. The main technical solution adopted is: a method for preparing a high-carbon high-alloy steel product, which includes the following steps: 1) preparing a high-carbon high-alloy steel low-segregation double-vacuum consumable billet; 2) high-temperature diffusion homogenization treatment and multi-fire cross-forging deformation blanking treatment to obtain a forging; 3) hot deformation extrusion treatment of the forging. This invention is mainly used to prepare a high-carbon high-alloy steel product with uniform distribution of fine carbides and elimination of porosity-type micro-defects. This patent does not have special process measures for multi-fire cross-forging deformation blanking treatment; the main invention part is in the hot deformation extrusion treatment to improve the material performance. Similarly, hot extrusion requires special molds, and the working conditions of the molds are harsh, the lifespan is limited, and the cost and energy consumption are high. In addition, the multi-fire cross-forging deformation blanking treatment process is more prone to cracking.

[0007] This invention is a new process method that addresses the issue of cracks easily generated during the large deformation forging process (or the multi-fire cross-forging deformation forging process) of billets. Summary of the Invention

[0008] To address the aforementioned problems, the present invention aims to provide a plasticizing and crack-resistant forging method for high alloy steel ingots.

[0009] The process route of this invention is as follows: first heating of steel ingot (hot charging or cold charging furnace) — pressing jaws, chamfering, and cutting ingot tail — second heating of steel ingot (high temperature homogenization diffusion annealing) — upsetting and wide anvil lengthening (also known as wide anvil squarening) — third heating of steel ingot — wide anvil lengthening.

[0010] Furthermore, if the lengthening workload is large, the number of heating cycles can be increased. Alternatively, if the billet temperature is below 900°C during the lengthening process, it needs to be returned to the heating furnace for reheating, which also requires increasing the number of heating cycles. Therefore, the above process route can also include a fourth (or even more) heating of the steel ingot and the corresponding wide anvil lengthening after heating.

[0011] The present invention provides a method for forging high alloy steel ingots to enhance plasticity and resist cracking, which specifically includes the following steps: (1) First heating of steel ingot; After the high alloy steel ingot is demolded, it is sent hot to the hot charging furnace in the forging workshop for heating, or cold steel ingot is sent cold to the charging furnace for heating. After heating, it is taken out of the furnace for the first forging. Furthermore, in step (1), if the high alloy steel ingot is hot-charged to the hot charging furnace after demolding, the hot charging furnace temperature is 900-950℃, the heating rate is no more than 60-80℃ / hour, the ingot holding temperature is 1150-1200℃, and the holding time is 0.7T hours (T= D / 100, where D is the effective cross-sectional size of the ingot before each furnace entry, in mm). Furthermore, in step (1), if the high alloy steel ingot is cold-loaded into the furnace after demolding, a segmented isothermal heating method should be adopted: first, heat the ingot to 300-350℃ at a rate not exceeding 40℃ / hour, and hold it for 0.5T hours (T= D / 100, where D is the effective cross-sectional size of the ingot before each furnace entry, in mm), then heat the ingot to 500-550℃ at a rate not exceeding 40℃ / hour, and hold it for 0.5T hours, then heat the ingot to 750±10℃ at a rate not exceeding 50℃ / hour, and hold it for 0.7T hours, then heat the ingot to 950±10℃ at a rate not exceeding 60-80℃ / hour, and hold it for 0.7T hours, then heat the ingot to 1150-1200℃ at a rate not exceeding 60-80℃ / hour, and hold it for 0.7T hours before it can be taken out of the furnace for the first forging. (2) First firing: Press the jaws, chamfer, and cut the spindle tail; (3) Second heating of steel ingot: After the first forging, the steel ingot is returned to the heating furnace for a second heating. While heating and holding at the temperature, the holding time is extended to carry out high-temperature homogenization diffusion annealing. The purpose is to eliminate or reduce dendritic segregation and regional segregation generated during the solidification process of the steel ingot, so as to homogenize the composition and structure, avoid cracks in weak links such as internal dendrite grain boundaries during forging, and improve the forgeability of the steel ingot. Furthermore, the specific process in step (3) is as follows: when the steel ingot is returned to the heating furnace after the first forging, the furnace temperature is 900-950℃. The steel ingot is heated to the diffusion annealing holding temperature at a rate of no more than 60-80℃ / hour. The diffusion annealing holding temperature is 1150℃-1200℃, and the holding time is T+(15~20) hours, where T is the same as T in step (1). After the holding time is completed, the steel ingot is taken out of the furnace for the second forging. (4) Second firing: After the steel ingot is heated a second time, namely high-temperature diffusion annealing, it is then subjected to upsetting and wide anvil lengthening in sequence. Upsetting has two purposes: first, to break up dendrites, forge together the internal cavities and porosity of the forging, improve the tangential properties of the forging, and reduce the anisotropy of the forging properties; second, to increase the diameter of the steel ingot so that the steel ingot can obtain a sufficient lengthening forging ratio.

[0012] Preheat the upsetting stencil and the top cover plate to 350-400℃ to prevent the steel ingot from cooling down too quickly due to heat transfer. Control the upsetting deformation rate to 5-7mm / s. Controlling the deformation rate is to prevent excessive deformation in the middle part from cracking due to excessive deformation, while excessive deformation will cause the steel ingot temperature to drop too quickly. When stretching the billet, the wide anvil should be preheated to 350-400℃ to prevent the billet from cooling down too quickly due to heat transfer. Two new processes are used to widen the anvil and lengthen the grain (such as...) Figure 1 One of the new processes is as follows: two consecutive forging passes in the same direction, that is, after forging one pass, the forging is not turned over, and then the next pass is forged. Then the forging is turned over 90 degrees and then the next pass is forged (in another direction). Then the previous process is repeated. Each pass starts from the nozzle end and ends at the riser end. Each pass has a deformation amount of 7-10%. The total deformation amount of the two passes (after forging one pass, the forging is not turned over, and then the next pass is forged) is 14-20%. Another new process is: after forging one pass, rotate the forging machine 180 degrees and forge the next pass, then rotate it 90 degrees and forge in another direction, and then repeat the previous process. Each pass has a deformation amount of 7-10%, and each pass starts from the sprue end and ends at the riser end. The total deformation amount of the two passes (forging one pass, rotating the forging machine 180 degrees and forging the next pass) is 14-20%.

[0013] The new wide-anvil forging process maintains the same total deformation in the same direction for the square billet cross-section as the original process. It successfully divides the original single forging pass into two, allowing high-alloy steel sufficient time to recover or recrystallize using its own heat, eliminating internal stress and restoring plasticity to achieve a plasticizing and crack-resistant effect. During the wide-anvil forging process, the billet temperature is constantly monitored to ensure it does not fall below 900℃. If the temperature drops below 900℃, the billet must be reheated in the furnace for 0.5T~0.7T hours before continuing forging.

[0014] (5) Third heating of steel ingot: After the second forging, the steel ingot is returned to the furnace for a third heating. The furnace temperature is 900-950℃, and the heating rate of the third heating is no more than 60-80℃ / hour. The holding temperature of the steel ingot is 1150℃-1200℃, and the holding time is 0.5T~0.7T hours. After the holding time is completed, the steel ingot is taken out of the furnace for the third forging. (6) Third fire: Continue to lengthen using a wide anvil, and do so in the same way as in step (4).

[0015] Furthermore, if the lengthening workload is large, the number of heating cycles can be increased, or if the temperature of the billet is lower than 900°C during the lengthening process, it needs to be returned to the heating furnace for reheating, and the number of heating cycles also needs to be increased. Therefore, the above-mentioned high alloy steel ingot plasticizing and crack-resistant forging method also includes the fourth (or even more) heating of the ingot and the corresponding wide anvil lengthening after heating. The wide anvil lengthening is the same as the wide anvil lengthening method in step (4).

[0016] High-alloy steel is a broad category, and the forging temperature range varies depending on the specific type, such as high-speed tool steel, special alloys, and high-temperature alloys. For example, the forging temperature range of high-speed tool steel is generally 200-280℃, while the forging temperature range of special alloys and high-temperature alloys is narrower, sometimes even less than 100℃. The initial forging temperature of 1150-1200℃ and the final forging temperature of 900℃ mentioned in this invention refer to general conditions. For high-alloy steels with even narrower forging temperature ranges, more suitable initial and final forging temperatures need to be determined based on specific circumstances, allowing for initial forging temperatures below 1150℃ and final forging temperatures above 900℃.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The high alloy steel ingot is heated slowly. During the heating and holding process before upsetting, a high-temperature homogenization diffusion annealing treatment is carried out to reduce or eliminate the segregation of chemical composition and microstructure of the ingot, so as to homogenize it. (2) When the steel ingot is upset, the upset tray and the top cover plate are preheated to prevent the steel ingot from cooling down too quickly due to heat transfer. The upset deformation rate is controlled at 5-7 mm / s. The purpose is to make it deform evenly, reduce stress concentration, and avoid upset cracking. (3) When lengthening a wide anvil, preheat the wide anvil and design two new wide anvil lengthening processes. The first is to forge two passes continuously in the same direction, that is, after forging one pass, do not turn it over, and then forge the next pass, repeating the above cycle, with a deformation of 7-10% per pass; the second is to forge one pass, then turn it 180 degrees and forge another pass, and then turn it 90 degrees and forge in another direction (e.g. Figure 1Each pass involves a 7-10% deformation, and the above cycle is repeated. Both processes start from the nozzle end and end at the riser end for each pass, with a total deformation of 14-20% for both passes. This means that the total deformation in the same direction for the square billet cross-section remains unchanged compared to the original process. Forging in two passes allows high-alloy steel sufficient time to recover or recrystallize using its own heat, eliminating internal stress and restoring plasticity, thereby achieving the effect of plasticizing and crack resistance. (4) This invention only uses general metallurgical tools and does not require the use of special tooling or special molds. Attached Figure Description

[0018] Figure 1 This is a comparative schematic diagram of the original wide-anvil square-making process in the prior art and the two new wide-anvil square-making processes proposed in this invention. Figure 2 This is a schematic diagram of the segmented isothermal heating process used in the first heating of the steel ingot in the plasticizing and crack-resistant forging method of high alloy steel ingot of the present invention. Detailed Implementation

[0019] To better understand the content of this invention, it will be further described below with reference to specific embodiments and accompanying drawings. The following embodiments are based on the technology of this invention and provide detailed implementation methods and operating steps, but the scope of protection of this invention is not limited to the following embodiments.

[0020] Please combine Figure 1-2 In order to better understand the new deformation process, the same parameters in the examples and comparative examples in the table are marked in bold.

[0021] Figure 1 This indicates the first two runs of the original process and the first four runs of the corresponding new process; subsequent forging runs repeat the previous process.

[0022] In the embodiments and comparative examples, the flipping is performed in only one direction within one firing cycle, that is, all flipping is performed in a clockwise direction or all flipping is performed in a counterclockwise direction within one firing cycle.

[0023] Example 1: In this embodiment, the part is named as follows: a stainless steel bar, made of 316H (07Cr17Ni12Mo2), with forging dimensions of Φ630mm×1160mm and a weight of 2830Kg. It was forged using a 5-ton cold-rolled steel ingot, resulting in an ingot utilization rate of 56.6%.

[0024] (1) First heating of steel ingot: For cold steel ingot charging furnaces, please refer to the heating process. Figure 2In this embodiment, the effective cross-sectional size of the steel ingot is D=630mm, so T=D / 100≈6 hours. First, the temperature is raised to 300-350℃ at a heating rate of V1 and held for 0.5T, i.e., 3 hours. Then, the temperature is raised to 500-550℃ at a heating rate of V1 and held for 0.5T, i.e., 3 hours. After that, the temperature is raised to 750±10℃ at a heating rate of V2 and held for 0.7T, i.e. 4 hours. Then, the temperature is raised to 950±10℃ at a heating rate of V3 and held for 0.7T, i.e. 4 hours. Finally, the temperature is raised to 1200℃ at a heating rate of V3 and held for 0.7T, i.e. 4 hours. After these 4 hours, the ingot can be taken out of the furnace for the first forging. Where V1≤40℃ / H, V2≤50℃ / H, and V3≤80℃ / H. (2) First firing: Press the jaws, chamfer, and cut the spindle tail; (3) Second heating of steel ingot, i.e., high-temperature homogenization diffusion annealing: After the first forging, the steel ingot is returned to the furnace. The furnace temperature is 900-950℃, and the heating rate is no more than 80℃ / hour. The diffusion annealing holding temperature of the steel ingot is 1200℃, and the diffusion annealing holding time is 21 hours (the effective cross-sectional size of the steel ingot is D=630mm). After the holding time is completed, the steel ingot is taken out of the furnace for the second forging. (4) Second firing: Preheat the upsetting sprue and top cover plate to 350℃. Control the upsetting deformation rate of the ingot to 7mm / s. Upset to a height H=540mm, at which point the diameter is approximately 1070mm. Then, use a 700mm wide anvil to forge the cross section to □1000×740×L. After one forging pass, rotate the anvil 180 degrees and forge again, then rotate it 90 degrees and forge again. Repeat the previous cycle for a total of 6 forging passes to achieve a cross section □1000×740×L. The reduction rate for each pass is approximately 10%. Each pass starts from the sprue end and ends at the riser end. Before lengthening the wide anvil, preheat the upper and lower wide anvils to approximately 350℃. The deformation parameters are shown in the table below (Table 1): Table 1 (5) Third heating of steel ingot: After the second forging, the steel ingot is returned to the furnace at a furnace temperature of 900-950℃ and a heating rate of no more than 80℃ / hour. The ingot is held at 1200℃ for 5 hours (at which point the effective cross-sectional size is 740mm). After the holding time is completed, the ingot is taken out of the furnace for the third forging. (6) Third fire: Continue using the wide anvil to forge the cross section □630×L. After forging one pass, rotate the anvil 180 degrees and forge the next pass, then rotate it 90 degrees and forge the next pass. Repeat the previous cycle for a total of 10 passes to forge the cross section □630×L. The reduction rate of each pass is about 10%. Each pass starts from the sprue end and ends at the riser end. Before lengthening the wide anvil, preheat the upper and lower wide anvils. The preheating temperature is about 350℃. The deformation parameters are shown in the table below (Table 2): Table 2 Then, the squares were rounded, the edges were rounded, and the piece was rolled and elongated to Φ630mm×L. One piece was cut to Φ630mm×1160mm, with a single weight of 2830Kg. After finishing, the finished product was hot-charged into the furnace for post-forging heat treatment.

[0025] Upon inspection, the surface of the finished product obtained after calcination and heat treatment was almost free of cracks, and all defects were within the machining allowance and could be removed by machining.

[0026] Comparative Example 1: In this comparative example, the part is a stainless steel bar, made of 316H (07Cr17Ni12Mo2), with forging dimensions of Φ630mm×1160mm and a weight of 2830Kg. It was forged using a 5-ton cold-rolled steel ingot, resulting in an ingot utilization rate of 56.6%.

[0027] (1) First heating of steel ingot: This step is the same as step (1) in Example 1. (2) First firing: Press the jaws, chamfer, and cut the spindle tail; (3) Second heating of steel ingot: After the first forging is completed, the steel ingot is returned to the furnace. The furnace temperature is 900-950℃, the heating rate is no more than 80℃ / hour, the ingot holding temperature is 1200℃, and the holding time is 6 hours. After the holding time is completed, the steel ingot is taken out of the furnace for the second forging. (4) Second firing: The steel ingot is upset to a height H=540mm, at which point the diameter is approximately 1070mm. Then, a 700mm wide anvil is used to forge the square ingot. After one forging pass, the ingot is rotated 90 degrees and forged again. This process is repeated for a total of 8 passes until the cross-section is □630×L. The reduction rate for each pass is approximately 20%. Each pass starts from the nozzle end and ends at the riser end.

[0028] The deformation parameters are shown in the table below (Table 3): Table 3 Then, the squares were rounded, the edges were rounded, and the piece was rolled and elongated to Φ635mm×L. One piece was cut to Φ635mm×1160mm, with a single weight of 2890Kg. After finishing, the finished product was hot-charged into the furnace for post-forging heat treatment.

[0029] The finished product obtained after heat treatment after forging has many cracks on its surface. After forging, the allowance is increased from the original Φ630mm to Φ635mm, and the defects are removed through subsequent processing.

[0030] Example 2: In this embodiment, the part is named as follows: a high-carbon, high-chromium heat-resistant steel bar, made of 102Cr17Mo, with forging dimensions of Φ750mm × 1290mm and a weight of 4460Kg. It was forged using an 8-ton hot steel ingot, resulting in an ingot utilization rate of 55.7%.

[0031] (1) First heating of steel ingot: The steel ingot is hot-charged into the furnace at a temperature of 900-950℃, with a heating rate not exceeding 60℃ / hour. The temperature is raised to the ingot holding temperature, which is 1150℃, and the holding time is 0.7T. In this embodiment, the effective cross-sectional size of the steel ingot is D = 770mm, so T = D / 100≈8 hours and the holding time is approximately 5.5 hours.

[0032] (2) First firing: Press the jaws, chamfer, and cut the spindle tail; (3) Second heating of steel ingot, i.e., high-temperature homogenization diffusion annealing: After the first forging, the steel ingot is returned to the furnace. The furnace temperature is 900-950℃, and the heating rate is no more than 60℃ / hour. The diffusion annealing holding temperature is 1150℃, and the diffusion annealing holding time is 28 hours (at this time, the effective cross-sectional size is 770mm). After the holding time is completed, the steel ingot is taken out of the furnace for the second forging. (4) Second firing: The upsetting sprue and top cover plate are preheated to 400℃. The upsetting deformation rate of the ingot is controlled at 5mm / s. The ingot is upset to a height H=655mm, at which point the diameter is approximately 1250mm. Then, a 700mm wide anvil is used for forging. After one forging pass, the ingot is not turned over, and then forging is repeated. Then, the ingot is turned over 90 degrees and forged again. This process is repeated for a total of 6 passes until the cross-section is □1200×960×L. The reduction rate for each pass is approximately 7%. Each pass starts from the sprue end and ends at the riser end. Before lengthening the wide anvil, the upper and lower wide anvils are preheated to approximately 400℃. The deformation parameters are shown in the table below (Table 4): Table 4 (5) Third heating of steel ingot: After the second forging, the steel ingot is returned to the furnace at a furnace temperature of 900-950℃, with a heating rate not exceeding 60℃ / hour. The ingot is held at 1150℃ for 6 hours (at which point the effective cross-sectional size is 960mm). After the holding period, the ingot is removed from the furnace for the third forging.

[0033] (6) Third fire: Continue to use a 700mm wide anvil to draw the square, and the wide anvil lengthening method is the same as in step (4). Forge a total of 10 passes to a cross section of approximately □880×L, with a reduction rate of approximately 7% per pass. Before lengthening the wide anvil, preheat the upper and lower wide anvils, with a preheating temperature of approximately 400℃. The deformation parameters are shown in the table below (Table 5): Table 5 (7) Fourth heating of steel ingot: After the third forging, the steel ingot is returned to the furnace at a furnace temperature of 900-950℃, with a heating rate not exceeding 60℃ / hour. The ingot is held at 1150℃ for 4.5 hours (at which point the effective cross-sectional size is 880mm). After the holding period, the ingot is removed from the furnace for the fourth forging. (8) Fourth fire: Continue to use 700mm wide anvil to draw square, and the wide anvil lengthening method is the same as in step (4). A total of 8 passes are forged to the cross section of approximately □770×L, with a reduction rate of approximately 7% per pass. Before lengthening the wide anvil, the upper and lower wide anvils are preheated, with a preheating temperature of approximately 400℃. The deformation parameters are shown in the table below (Table 6): Table 6 Then, the squares were rounded, the edges were rounded, and the piece was rolled and elongated to Φ750mm×L. One piece was cut to Φ750mm×1290mm, with a single weight of 4460Kg. The finished product was then hot-loaded into the furnace for post-forging heat treatment.

[0034] Upon inspection, the surface of the finished product obtained after forging and heat treatment showed almost no cracks, and all defects were within the machining allowance.

[0035] Comparative Example 2: In this embodiment, the part is named as follows: a high-carbon, high-chromium heat-resistant steel bar, made of 102Cr17Mo, with forging dimensions of Φ750mm × 1290mm and a weight of 4460Kg. It was forged using an 8-ton hot steel ingot, resulting in an ingot utilization rate of 55.7%.

[0036] (1) First heating of steel ingot: This step is the same as step (1) in Example 2. (2) First firing: This step is the same as step (2) in Example 2. (3) Second heating of steel ingot: After the first forging is completed, the steel ingot is returned to the furnace. The furnace temperature is 900-950℃, the heating rate is no more than 60℃ / hour, the ingot holding temperature is 1150℃, the holding time is 8 hours, and after the holding time is completed, it is taken out of the furnace for the second forging. (4) Second firing: The steel ingot is upset to a height H=655mm, at which point the diameter is approximately 1250mm. Then, it is forged using a 700mm wide anvil, rotated 90 degrees after one forging pass, and then forged again. This cycle is repeated for a total of 4 forging passes until the cross-section is □1030×L, with a reduction rate of approximately 14% per pass. Each pass starts from the nozzle end and ends at the riser end.

[0037] The deformation parameters are shown in the table below (Table 7): (5) Third heating of steel ingot: After the second forging, the steel ingot is returned to the furnace at a furnace temperature of 900-950℃ and a heating rate of no more than 60℃ / hour. The ingot is held at 1150℃ for 7 hours (at which point the effective cross-sectional size is 1030mm). After the holding time is completed, the ingot is taken out of the furnace for the third forging. (6) Third fire: Continue to use a 700mm wide anvil for square drawing, and the wide anvil for length drawing method is the same as in step (4). Forge a total of 8 passes to a cross section of approximately □770×L, with a reduction rate of approximately 7% per pass; The deformation parameters are shown in the table below (Table 8): Then, the squares were rounded, the edges were rounded, and the piece was rolled and elongated to Φ750mm×L. One piece was cut to Φ760mm×1300mm, with a single weight of 4630Kg. The finished product was then hot-charged into a furnace for post-forging heat treatment.

[0038] The finished product obtained after post-forging heat treatment exhibited numerous surface cracks and angular cracks at the ends. The forging allowance was increased from the original Φ750mm×1290mm to Φ760mm×1300mm, and the defects were removed through subsequent machining. However, the increased allowance resulted in less material removal at the sprue and riser ends of the ingot, potentially reducing internal quality or necessitating the use of a larger ingot for forging this workpiece.

[0039] This comparative example represents the first-generation improved process, refined after initial research. The original process lacked high-temperature diffusion annealing, resulting in deformation of only 20% per pass, and large cracks during forging led to scrapping. This invention represents the second-generation improved process, offering the best results and solving the problem of poor forgeability in high-carbon, high-chromium steel.

[0040] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method of plasticising and forging a high alloy steel ingot, characterised in that, Specifically comprising the following steps: (1) the first heating of the steel ingot; After the high-alloy steel ingot is demoulded, it is hot sent to a hot charging furnace in a forging workshop to heat the steel ingot or a cold steel ingot is cold charged to heat the steel ingot, after the heating is completed, the furnace is discharged to perform the first forging; (2) the first fire: pressing the jaw, chamfering, cutting the ingot tail; (3) the second heating of the steel ingot: after the first fire of the steel ingot is forged, the steel ingot is returned to the heating furnace to perform the second heating, that is, high-temperature homogenization diffusion annealing; (4) the second fire: after the steel ingot is heated for the second time, that is, high-temperature diffusion annealing, the furnace is discharged to perform upsetting and wide anvil lengthening on the steel ingot in turn, the upsetting disc and the upper cover plate are preheated when the upsetting is performed, and the wide anvil is preheated when the wide anvil lengthening is performed; the wide anvil lengthening adopts one of two new processes, one of which is: after one forging pass, the steel ingot is not turned over, the next forging pass is performed, then the steel ingot is turned over by 90 degrees to perform the next forging pass, and then the previous process is repeated, each pass is started from the water gap end and ended at the riser end, and the deformation amount of each pass is 7-10%; the other new process is: after one forging pass, the steel ingot is turned over by 180 degrees to perform the next forging pass, then the steel ingot is turned over by 90 degrees to perform the forging in the other direction, and then the previous process is repeated, the deformation amount of each pass is 7-10%, and each pass is started from the water gap end and ended at the riser end; (5) the third heating of the steel ingot: after the second fire is forged, the furnace is returned to perform the third heating, after the heating is completed, the furnace is discharged to perform the third fire forging; (6) the third fire: the wide anvil lengthening is continuously performed, and the wide anvil lengthening manner is the same as that in step (4).

2. The high alloy steel ingot plasticization and crack resistant forging method according to claim 1, characterized in that, In step (1), if the high-alloy steel ingot is hot sent to the hot charging furnace in the forging workshop after being demoulded, the temperature of the hot charging furnace is 900-950℃, the temperature rising speed is not greater than 60-80℃ / h, the steel ingot is kept at a temperature of 1150-1200℃, and the keeping time is 0.7T hours, wherein T=D / 100, D is the effective cross-sectional size of the steel ingot before entering the furnace each time, and the unit is mm.

3. The high alloy steel ingot plasticization and crack resistant forging method according to claim 1, characterized in that, In step (1), if the high-alloy steel ingot is cold charged to heat the steel ingot after being demoulded, a segmented isothermal temperature rising method is adopted: first, the temperature is raised to 300-350℃ at a speed not greater than 40℃ / h, and kept for 0.5T hours, then the temperature is raised to 500-550℃ at a speed not greater than 40℃ / h, and kept for 0.5T hours, then the temperature is raised to 750±10℃ at a speed not greater than 50℃ / h, and kept for 0.7T hours, then the temperature is raised to 950±10℃ at a speed not greater than 60-80℃ / h, and kept for 0.7T hours, then the temperature is raised to 1150-1200℃ at a speed not greater than 60-80℃ / h, and kept for 0.7T hours, and then the furnace can be discharged to perform the first fire forging, wherein T=D / 100, D is the effective cross-sectional size of the steel ingot before entering the furnace each time, and the unit is mm.

4. The high alloy steel ingot plasticization and crack resistant forging method of claim 1, wherein, In step (3), when the steel ingot is returned to the furnace after the first fire is forged, the charging temperature is 900-950℃, and the second heating is that the steel ingot is heated to the diffusion annealing keeping temperature at a speed not greater than 60-80℃ / h and kept, after the keeping is completed, the furnace is discharged to perform the second fire forging.

5. The high alloy steel ingot plasticization and crack resistant forging method according to claim 4, characterized in that, The diffusion annealing holding temperature is 1150-1200℃, and the holding time is T+(15-20) hours.

6. The high alloy steel ingot plasticization and crack resistant forging method of claim 1, wherein, The upsetting die and the upper cover plate are preheated to 350-400℃ during the upsetting in step (4), and the upsetting deformation rate is controlled to 5-7 mm / s.

7. The high alloy steel ingot plasticization and crack resistant forging method of claim 1, wherein, The anvil is preheated to 350-400℃ during the anvil lengthening in step (4).

8. The high alloy steel ingot plasticization and crack resistant forging method of claim 1, wherein, The temperature of the steel billet is monitored during the anvil lengthening in step (4), and the steel billet temperature is ensured to be not lower than 900℃, and the steel billet is reheated for 0.5T-0.7T hours when the temperature is lower than 900℃, and then the forging is continued.

9. The high alloy steel ingot plasticization and crack resistant forging method of claim 1 wherein, The furnace charging temperature is 900-950℃ in step (5), the third heating temperature increasing speed is not higher than 60-80℃ / hour, the steel ingot holding temperature is 1150-1200℃, and the holding time is 0.5T-0.7T hours.

10. The high alloy steel ingot plasticization and crack resistant forging method of claim 1 wherein, The forging method further comprises the fourth heating of the steel ingot and the corresponding anvil lengthening after the heating, or more times of heating of the steel ingot and the corresponding anvil lengthening after the heating.

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