Forging cogging method for improving yield of nickel-based alloy large slab ingot

Abstract

The invention discloses a forging cogging method for improving the yield of a nickel-based alloy large slab ingot, which comprises the following steps: S1, heating a steel ingot according to the nickel-based alloy steel type and the thickness of the steel ingot; s2, forging cogging is conducted, after the steel ingot is discharged out of a furnace, segmented multi-heating-number forging is conducted, the tail of the steel ingot is forged to the target thickness, forging of the head of the steel ingot is conducted in the last heating number in a full-anvil large-rolling-reduction forging mode, and after forging is conducted to the target thickness, air cooling is conducted to obtain a plate blank; and S3, the surface of the plate blank is peeled, and the head and the tail are sawed after head and tail ultrasonic flaw detection. According to the method, the whole steel ingot is forged in a segmented mode, the steel ingot is gradually cogged to the target thickness from the tail of the steel ingot, forging of the head of the steel ingot serves as the final process, the forging strategy of increasing the heating temperature, cooling the surface and conducting single-pass wide anvil large reduction is adopted for the last heating number, and therefore the head cutting amount is reduced, and the yield is increased.

Description

Technical Field

[0001] This invention relates to the field of metal pressure processing, and more particularly to a forging method for improving the yield of large flat nickel alloy ingots. Background Technology

[0002] In recent years, with the popularization of new technologies leading to the upgrading and transformation of existing equipment, steel plates, as a basic material, are of great significance to national economic development and national defense construction. They form the foundation of national industrialization and modernization, and are also one of the key areas of national defense construction. With the trend towards larger equipment, the demand for thick plates is increasing, inevitably requiring the enlargement of original steel ingot sizes. However, controlling the solidification structure of large steel ingots has always been a difficult problem hindering the industry's development. Steel shrinkage can cause solidification defects at the ingot head, and even metallurgical defects such as protective slag inclusions. Before rolling into steel plates, large steel ingots need to be forged to obtain billets of suitable sizes. Among the defects at the ingot head, only closed shrinkage cavities can be closed during forging, while general shrinkage cavities and protective slag inclusions can only be removed after forging. In the previous large flat billet forging process, the ingot size may exceed the press stroke limit, generally requiring a single, uniform, multi-stage drawing forging process, making upsetting deformation difficult.

[0003] A search revealed that Chinese patent application CN202210685035.8 addressed the tongue-shaped and collapsed corners at the ends of H13 large electroslag ingot forging blanks by proposing the principle of "rapid temperature operation and combined forging cycles." This involves increasing the reduction amount at high temperatures and appropriately reducing the reduction amount at low temperatures to accelerate the forging frequency and improve the forging yield. Chinese patent application CN202311365531.6 proposed a forging method to improve the yield of titanium alloy plates, addressing issues such as poor straightness, large edges and corners, and excessive machining due to bending. This method specifies upsetting of the blank and adds flattening treatment at both ends of the blank during intermediate forging. Chinese patent application CN202410522945.3 discloses a forging method for high-temperature alloy blanks. By establishing a reasonable high-temperature homogenization process and specifying the rough forging and fine forging deformation ratio, a uniformly structured forging blank is obtained, improving the forging yield. However, none of these methods address solutions for defects at the ingot head. Therefore, improving the forging process to address the head defects of large flat billets, reducing the amount of blank head removed, and increasing product yield are of great significance for cost reduction and efficiency improvement. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a forging method for improving the yield of large flat nickel-based alloy ingots. The method involves forging the entire ingot in sections, starting from the tail end and gradually working towards the target thickness. The forging of the ingot head is the final process. The last forging pass employs a forging strategy of "increasing heating temperature - surface cooling - single-pass full anvil large reduction" to reduce the amount of head cut and improve the yield.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first aspect of the present invention provides a forging method for improving the yield of large flat nickel alloy ingots, comprising the following steps:

[0007] S1, steel ingot heating, heating is performed according to the nickel-based alloy steel grade and the thickness of the steel ingot;

[0008] S2, forging billet, after the steel ingot is taken out of the furnace, it is forged in sections and multiple times. First, the tail of the steel ingot is forged to the target thickness, and the head of the steel ingot is forged in the last time. The forging method of full anvil and large reduction is adopted to forge the steel ingot to the target thickness and then air cool to obtain the slab.

[0009] S3 involves peeling the surface of the slab, ultrasonically inspecting the head and tail, and then sawing off the head and tail.

[0010] Preferably, in step S1, when the steel ingot is heated, the upper limit of the heating temperature range is 100-150°C below the alloy solidus line, and the lower limit of the heating temperature range is the remelting temperature of the carbide or γ' phase. The holding time satisfies: t = 0.3*H ~ 0.8*H, where H is the thickness of the steel ingot in mm; t is the holding time in min.

[0011] Preferably, in step S1, when the steel ingot is heated by hot-delivery steel ingot, the hot-delivery steel ingot is put into the furnace at a furnace temperature ≤600℃ and heated to the target heating temperature T1 at a heating rate ≤100℃ / h and held at that temperature.

[0012] Preferably, in step S1, when cold steel ingots are used for heating the steel ingots, the cold steel ingots are put into the furnace at a furnace temperature ≤400℃, heated at a heating rate ≤80℃ / h to a platform temperature T2 of 600~900℃, held for 2~6h, and then heated at a heating rate ≤100℃ / h to the target heating temperature and held.

[0013] Preferably, the forging blanking in step S2 includes the following steps:

[0014] S21, the tail of the steel ingot is forged in multiple passes. After the steel ingot is taken out of the furnace, the first pass of forging begins from the tail of the steel ingot. The reduction in a single pass is controlled at 30-100mm. The single pass is forged to a position 500-1000mm away from the cap and then returned to the tail of the steel ingot for the next pass of forging. The forged part and the unforged part are smoothly transitioned with a step of no more than 30mm. The forging stop temperature is ≥850℃. After forging stops, the steel ingot is returned to the furnace for heating and heat preservation.

[0015] S22, after exiting the furnace, undergoes a second forging. The single-pass reduction is controlled at 30-80mm, and the forging stop temperature is ≥850℃. After stopping forging, it is returned to the furnace for heating and holding. Then, the next forging is carried out until the tail of the ingot is forged to the target thickness.

[0016] S23: After the tail end of the steel ingot is forged, it is reheated and kept warm in the furnace. After being taken out of the furnace and left to stand for 3 to 10 minutes, the head of the steel ingot is forged in the last forging. The forging method of full anvil and large reduction is adopted. After forging to the target thickness, it is air cooled to obtain the slab.

[0017] Preferably, in steps S21 and S22, the reheating temperature is 1140–1250°C, and the holding time is 90–240 min.

[0018] Preferably, the reheating temperature in step S23 is 10-30°C higher than the reheating temperatures in steps S21 and S22, and the holding time is 90-240 minutes.

[0019] Preferably, in step S23, in the full-anvil large-reduction forging method, the thickness of the first anvil covers the unforged part of the steel ingot, and the reduction is controlled at 200-400mm; the subsequent reduction continues from the tail to the head, and the reduction is controlled at 100-200mm, and it is divided into at most three anvil forging.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. In this invention, the forging of the head of the steel ingot is taken as the final process. The last forging adopts the forging strategy of "increasing the heating temperature - appropriately cooling the surface - large reduction of the full anvil in a single pass". That is, the heating temperature of the last forging is higher than that of the previous forging. After the furnace is removed, a static cooling process is added to form a significant internal and surface temperature difference. The deformation resistance of the surface is greater than that of the core. Metal rheology is more likely to occur inside the steel ingot. This helps to squeeze out metallurgical defects such as solidification defects or protective slag inclusions at the head of the steel ingot to the end, thereby reducing the amount of head cutting and improving the yield.

[0022] 2. This invention starts the forging of steel ingots from the tail end, using the cap as a clamp, eliminating the need to turn the forging process around, which helps to improve the forging rhythm. By using rapid forging, the amount of reduction per heat is increased, reducing the number of heats required for billet opening, improving efficiency and reducing energy consumption.

[0023] 3. Since solidification defects (porosity, shrinkage cavities, etc.) or metallurgical defects such as protective slag inclusions are easily formed at the head of the steel ingot during the solidification process, the present invention forges the entire steel ingot in sections, and first gradually opens the tail of the steel ingot to the target thickness. The forging of the tail of the steel ingot can be carried out with small deformation and multiple passes, while the forging of the head of the steel ingot requires a wide anvil and large pressing process, which is conducive to pressing and sealing solidification defects of the type of porosity and shrinkage cavities.

[0024] 4. The forging process of this invention is carried out in stages, and the two stages are transitioned by small steps with a step height of ≤30mm. This can effectively prevent the formation of large folding defects on the surface. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of a billet-making method for improving the yield of large flat nickel alloy ingots according to the present invention.

[0026] Figure 2 The heating curves of the steel ingots of the present invention are shown in (a) and (b).

[0027] Figure 3 This is a schematic diagram of the transition section during the forging process of the present invention;

[0028] Figure 4 A schematic diagram of a UNS N08810 steel ingot;

[0029] Figure 5 For along Figure 4 The longitudinal section mesh extracted from the width centerline;

[0030] Figure 6 The longitudinal section mesh diagram is obtained by simulating the deformation conditions according to the original forging process;

[0031] Figure 7 A longitudinal section mesh diagram simulating the deformation conditions of forging from the tail of a steel ingot according to the billet-opening method of the present invention;

[0032] Figure 8 The longitudinal section mesh diagram is obtained by simulating the deformation conditions of the blanking method according to the present invention. Detailed Implementation

[0033] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way.

[0034] With the trend towards larger equipment, the demand for large single-weight steel ingots is increasing. For plate products, large-sized steel ingots cannot be directly rolled into rolling mills and need to be forged into slabs of specific specifications. During the forging process, defects at the head of large steel ingots usually need to be removed after forging. Therefore, the larger the cross-section of the slab, the greater the impact of the amount removed on the yield. Thus, to improve the product yield and reduce the weight of the cut-off head, it is necessary to continuously optimize the forging process under the premise of the same raw materials. This invention proposes a forging method for improving the yield of large nickel-based alloy flat ingots, taking the forging of the ingot head as the final process. The final forging pass adopts a forging strategy of "increasing the heating temperature - appropriately cooling the surface - single-pass wide anvil large reduction," which helps to squeeze out metallurgical defects such as solidification defects or protective slag inclusions at the head of the ingot, thereby reducing the amount of cut-off head and improving the yield.

[0035] Combination Figure 1 As shown, the present invention provides a forging method for improving the yield of large flat nickel alloy ingots, comprising the following steps:

[0036] S1, steel ingot heating, heating is performed according to the nickel-based alloy steel grade and the thickness of the steel ingot;

[0037] The heating temperature of steel ingots should be determined according to the nickel-based alloy steel grade. It is generally necessary to consider the thermoplasticity and deformation resistance of the material at different temperatures, as well as to prevent overheating and burning due to excessively high temperatures. When heating steel ingots, the upper limit of the heating temperature range is 100–150°C below the alloy solidus line, and the lower limit is the dissolution temperature of the carbide or γ' phase. The holding time is determined by the thickness of the steel ingot (H, in mm), and the holding time (t, in min) satisfies: t = 0.3 * H ~ 0.8 * H.

[0038] To prevent thermal stress cracking caused by large internal temperature gradients during the heating process, hot-delivered and cold-state ingots are differentiated in the on-site heating process. Hot-delivered ingots can be directly heated to the target heating temperature T1 and held at a heating rate of ≤100℃ / h after being placed in the furnace at a furnace temperature ≤600℃. Cold-state ingots, however, require the furnace temperature to be lowered to below 400℃, then heated to a plateau temperature T2 (T2 = 600~900℃) at a heating rate of ≤80℃ / h, held for 2~6 hours, and then heated to the target heating temperature T1 and held at a heating rate of ≤100℃ / h. See the schematic diagrams of the heating curves for hot-delivered and cold-state ingots. Figure 2 As shown in (a) and (b).

[0039] S2, forging billet, after the steel ingot is taken out of the furnace, it is forged in sections and multiple times. First, the tail of the steel ingot is forged to the target thickness, and the head of the steel ingot is forged in the last time. The full anvil large reduction forging method is used. After forging to the target thickness, the slab is air cooled to obtain the billet.

[0040] Step S2, the forging of the billet, includes the following steps:

[0041] S21, the tail of the steel ingot undergoes multi-pass forging. After the ingot exits the furnace, the first forging begins from the tail of the ingot. The reduction per pass is controlled at 30-100mm. Forging continues until the ingot reaches a position 500-1000mm from the cap, then returns to the tail of the ingot for the next forging pass. The forged and unforged portions transition smoothly with a step not exceeding 30mm (see [reference]). Figure 3 As shown), the forging stop temperature is ≥850℃. The specific temperature requirement can be determined by conducting high-temperature thermoplasticity tests based on the nickel-based alloy steel grade. After forging stops, the steel is reheated in the furnace and held at that temperature. The reheating temperature is 1140~1250℃, and the holding time is 90~240min.

[0042] S22, after exiting the furnace, undergoes a second forging. The single-pass reduction is controlled at 30-80mm, and the forging stop temperature is ≥850℃. After stopping forging, it is returned to the furnace for heating and holding. Then, the next forging is carried out until the tail of the ingot is forged to the target thickness.

[0043] Specifically, after reheating, the steel ingot is forged a second time, starting from the tail and moving towards the head, with a single-pass reduction controlled at 30-80mm. The forged and unforged portions are smoothly transitioned with a step not exceeding 30mm. The forging stop temperature is ≥850℃, with the specific temperature requirement determined by conducting high-temperature thermoplasticity tests based on the nickel-based alloy steel grade. Reheating is then carried out for 90-240 minutes at a temperature of 1140-1250℃. This process is repeated until the tail of the ingot is forged to the target thickness.

[0044] S23: After the tail end of the steel ingot is forged, it is reheated and kept warm in the furnace. After being taken out of the furnace and left to stand for 3 to 10 minutes, the head of the steel ingot is forged in the last forging. The forging method of full anvil and large reduction is adopted. After forging to the target thickness, it is air cooled to obtain the slab.

[0045] The forging of the cap end, i.e., the head of the ingot, is placed in the last forging pass. The holding temperature should be increased compared to the previous passes, for example, 10-30℃ higher than the reheating temperature in steps S21 and S22 (1150-1280℃). The specific temperature should be based on the solidus temperature and thermoplasticity test results of the alloy. The holding time is 90-240 minutes. After exiting the furnace, the ingot should be allowed to stand for 3-10 minutes to reduce the surface temperature before forging begins. The purpose of this is to increase the deformation resistance of the ingot surface, so that more of the metal rheology during forging occurs in the core of the ingot, and to use the extrusion effect to squeeze out as many defects as possible from the head of the ingot. Therefore, the first pass of the last forging pass uses a full anvil and large reduction method. The anvil thickness should completely cover the unforged part of the billet (except for the cap), and the reduction is controlled at 200-400mm. Subsequent reductions continue from the tail to the head, with the reduction controlled at 100-200mm, and forging is done in up to three anvils, including the cap line area. Once the entire material has been forged to the target thickness, it is air-cooled to obtain a slab.

[0046] S3 involves peeling the surface of the slab, ultrasonically inspecting the head and tail, and then sawing off the head and tail.

[0047] The entire slab is edged, leveled, and hot-cut at the top. After air cooling, the top and bottom surfaces of the slab are peeled off. After ultrasonic flaw detection at the beginning and end, the beginning and end are sawn off to supply the slab for subsequent processes.

[0048] To verify the effectiveness of the above technical solutions, numerical simulation was used to simulate both the original forging process and the forging process proposed in this invention. UNS N08810 was used as the model material, and the model dimensions were set to 690mm × 2000mm × 1000mm (thickness × width × length). Figure 4 As shown, the heating temperature is 1150℃. Along... Figure 4 Extracting the longitudinal section mesh from the width centerline, as shown in the image. Figure 5 As shown.

[0049] The specific simulation scheme is as follows:

[0050] (1) Deformation conditions of the original forging process: the cross section thickness is from 690mm→600mm→550mm→500mm→450mm→400mm→350mm→320mm (from left to right), the anvil advance is 200mm each time, and the temperature is allowed to rise for 10 seconds before pressing. Figure 6 The mesh diagram is obtained by simulating the deformation conditions according to scheme (1). It can be seen that the deformation of the slab head is prone to indentation. If there is a solidification defect at the head, it will cause the defect to be pressed inward, resulting in an increase in the amount of subsequent head cutting.

[0051] (2) Deformation conditions of the forging process proposed in this invention: cross-sectional thickness from 690mm → 500mm → 380mm → 330mm → 320mm (the front section of the slab is pressed down, and the remaining 500mm of the rear section maintains the original slab thickness, see details). Figure 7 ), 690mm→320mm (finally using a large feed and large compression to press down to a thickness of 320mm), feed 300mm, wait 600 seconds before pressing down. Figure 8 The mesh diagram is obtained by simulating the deformation conditions according to scheme (2). As can be seen from the figure, the static cooling before forging and the large pressure of the head cause the metal in the core to flow outward, which has an obvious extrusion effect. It can effectively squeeze out the internal defects near the head, reduce the amount of subsequent head cutting, and improve the forging yield.

[0052] The forging method for improving the yield of large flat nickel alloy ingots according to the present invention will be further described below with specific examples.

[0053] Example 1

[0054] The process of producing 350mm×1600mm slabs from 20 tons of UNS N08810 alloy flat ingots (~700mm*1600mm*2300mm) in the example is as follows:

[0055] a. Hot-delivered steel ingots are fed into the furnace at a temperature ≤600℃, heated to 1180±10℃ at a heating rate of 80℃ / h and held for 350min before being removed from the furnace;

[0056] b. After exiting the furnace, use the ingot cap as a clamp and start the first forging from the tail of the ingot. The first forging is divided into two passes. The first pass is 80mm in reduction and 300-500mm in anvil advance. Stop forging when it is 600mm away from the cap line. The forged part and the unforged part are transitioned by a 30mm step. Then return to the tail to start the second forging. The reduction is 50mm and the anvil advance is 300-500mm. The forging stop temperature is above 900℃. Reheat in the furnace to 1180±10℃ and hold for 90min.

[0057] c. The second forging is divided into two passes. The first pass has a reduction of 80mm and an anvil advance of 300-500mm. The forged and unforged parts are transitioned by a 30mm step. Then, the second forging begins at the tail end with a reduction of 40mm and an anvil advance of 300-500mm. The forging stop temperature is above 900℃. The parts are then reheated in the furnace to 1180±10℃ and held for 90 minutes.

[0058] d. The third forging process is divided into two passes. The first pass involves a reduction of 70mm and an anvil advance of 300-500mm, transitioning to the unforged portion with a 30mm step. Then, the forging begins at the tail end with a reduction of 30mm and an anvil advance of 300-500mm. The forging is stopped at a temperature above 900℃, and the ingot is reheated to 1200±10℃ and held for 90 minutes. At this point, the tail end of the ingot has been forged to the target thickness of 350mm.

[0059] e. The forging of the ingot head is completed in the last forging pass. After exiting the furnace, it is allowed to stand for 6 minutes. The final forging pass uses a full anvil and large reduction method. The first reduction is 200mm, and then the ingot is drawn from near the tail towards the head, completed in two anvil passes with a reduction of 150mm. Finally, the entire ingot is edged, leveled, and the cap is hot-cut. After forging, it is air-cooled to obtain a slab.

[0060] f. Peel the top and bottom surfaces of the slab, perform ultrasonic flaw detection on the head and tail, and then saw off the head and tail to supply the slab for subsequent processes.

[0061] Statistics show that, compared with the original process, the average forging yield of forging billets produced by the above process can be increased by 1.97%.

[0062] Example 2

[0063] The process of producing 300mm×1400mm slabs from a 13-ton flat ingot of UNS N08120 alloy (thickness approximately 650mm~780mm, width approximately 1350mm, ingot length 1700mm) in the example is as follows:

[0064] a. Cold steel ingots are fed into the furnace at a furnace temperature of 350℃, heated to 650℃ at a rate of 60℃ / h and held for 3 hours, then heated to 1190±10℃ at a rate of 80℃ / h and held for 420 minutes before being removed from the furnace.

[0065] b. After exiting the furnace, use the ingot cap as a clamp and start the first forging from the tail. The first forging is divided into three passes. The first pass is about 90mm down and 300-500mm into the anvil. Stop forging when it is 750mm away from the cap line. The forged part and the unforged part are transitioned by a 30mm height step. Then return to the tail to start the second forging. The down is about 60mm down and 300-500mm into the anvil. The third pass is about 30mm down and 300-500mm into the anvil each time. The forging temperature is above 900℃. Reheat in the furnace to 1190±10℃ and hold for 90 minutes.

[0066] c. The second forging is divided into two passes. The first pass involves a reduction of about 80mm and an anvil advance of 300-500mm. It transitions to the unforged part with a 30mm step and then returns to the tail to start the second forging. The reduction is about 30mm and the anvil advance is 300-500mm. The forging stop temperature is above 900℃. It is then reheated in the furnace to 1190±10℃ and held for 90 minutes.

[0067] d. The third forging is divided into one pass of pressing down, with a pressing amount of 60-80mm and an anvil advance of 300-500mm. It transitions with the unforged part with a 30mm step. After the tail of the steel ingot is opened to the target thickness of 300mm, it is finished and flattened. The forging temperature is above 900℃. It is then reheated in the furnace to 1205±10℃ and held for 90 minutes. At this point, the tail of the steel ingot has been forged to the target thickness of 300mm.

[0068] e. The forging of the ingot head is completed in the last heat. After exiting the furnace, it is allowed to stand for 5 minutes. Forging is carried out using a full anvil and large reduction method. The first reduction is 250mm, and then the lengthening continues from near the tail towards the head. The second pass is completed with two anvils, with a reduction of 130mm, and the third pass is completed with three anvils, with a reduction of 100mm. Finally, the entire ingot is edged, leveled, and the cap is hot-cut. After forging, it is air-cooled to obtain a slab.

[0069] f. Peel the top and bottom surfaces of the slab, perform ultrasonic flaw detection on the head and tail, and then saw off the head and tail to supply the slab for subsequent processes.

[0070] Statistics show that, compared with the original process, the average forging yield of forging billets produced by the above process can be increased by 2.13%.

[0071] In summary, the forging method for improving the yield of large nickel-based alloy slabs proposed in this invention utilizes a segmented forging process to increase the heating temperature and forging reduction at the forging head of the ingot. This fully leverages the extrusion effect of the metal's hot deformation process, reducing the amount of ingot trimming and thus achieving the goal of increasing the forging yield. Furthermore, this method is versatile and reproducible, and can be extended to the forging of other alloy slabs besides nickel-based alloys.

[0072] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A forging method for improving the yield of large flat nickel alloy ingots, characterized in that, Includes the following steps: S1, steel ingot heating, heating is performed according to the nickel-based alloy steel grade and the thickness of the steel ingot; S2, forging billet, after the steel ingot is taken out of the furnace, it is forged in sections and multiple times. First, the tail of the steel ingot is forged to the target thickness, and the head of the steel ingot is forged in the last time. The forging method of full anvil and large reduction is adopted to forge the steel ingot to the target thickness and then air cool to obtain the slab. S3 involves peeling the surface of the slab, ultrasonically inspecting the head and tail, and then sawing off the head and tail.

2. The forging method for improving the yield of large flat nickel alloy ingots as described in claim 1, characterized in that, In step S1, when the steel ingot is heated, the upper limit of the heating temperature range is 100-150°C below the alloy solidus line, and the lower limit of the heating temperature range is the remelting temperature of the carbide or γ' phase. The holding time satisfies: t = 0.3*H ~ 0.8*H, where H is the thickness of the steel ingot in mm; t is the holding time in min.

3. The forging method for improving the yield of large flat nickel alloy ingots as described in claim 1, characterized in that, In step S1, when hot-delivered steel ingots are used for heating the steel ingots, the hot-delivered steel ingots are put into the furnace at a furnace temperature ≤600℃ and heated to the target heating temperature T1 at a heating rate ≤100℃ / h.

4. The forging method for improving the yield of large flat nickel alloy ingots as described in claim 1, characterized in that, In step S1, when cold steel ingots are used for heating the steel ingots, the cold steel ingots are put into the furnace at a furnace temperature ≤400℃, heated at a heating rate ≤80℃ / h to a platform temperature T2 of 600~900℃, held for 2~6h, and then heated at a heating rate ≤100℃ / h to the target heating temperature T1 and held.

5. The forging method for improving the yield of large flat nickel alloy ingots as described in claim 1, characterized in that, The forging process in step S2 includes the following steps: S21, the tail of the steel ingot is forged in multiple passes. After the steel ingot is taken out of the furnace, the first pass of forging begins from the tail of the steel ingot. The reduction in a single pass is controlled at 30-100mm. The single pass is forged to a position 500-1000mm away from the cap and then returned to the tail of the steel ingot for the next pass of forging. The forged part and the unforged part are smoothly transitioned with a step of no more than 30mm. The forging stop temperature is ≥850℃. After forging stops, the steel ingot is returned to the furnace for heating and heat preservation. S22, after exiting the furnace, undergoes a second forging. The single-pass reduction is controlled at 30-80mm, and the forging stop temperature is ≥850℃. After stopping forging, it is returned to the furnace for heating and holding. Then, the next forging is carried out until the tail of the ingot is forged to the target thickness. S23: After the tail end of the steel ingot is forged, it is reheated and kept warm in the furnace. After being taken out of the furnace and left to stand for 3 to 10 minutes, the head of the steel ingot is forged in the last forging. The forging method of full anvil and large reduction is adopted. After forging to the target thickness, it is air cooled to obtain the slab.

6. The forging method for improving the yield of large flat nickel alloy ingots as described in claim 5, characterized in that, In steps S21 and S22, the reheating temperature is 1140–1250°C, and the holding time is 90–240 min.

7. The forging method for improving the yield of large flat nickel alloy ingots as described in claim 5, characterized in that, The reheating temperature in step S23 is 10-30°C higher than the reheating temperatures in steps S21 and S22, and the holding time is 90-240 minutes.

8. The forging method for improving the yield of large flat nickel alloy ingots as described in claim 5, characterized in that, In step S23, in the full-anvil large-reduction forging method, the thickness of the first anvil covers the unforged part of the steel ingot, and the reduction is controlled at 200-400mm; subsequent reductions continue from the tail to the head, and the reduction is controlled at 100-200mm, with a maximum of three anvil forgings.

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