High-temperature alloy ingot cogging process based on finite element computational analysis

Abstract

The invention provides a high-temperature alloy ingot cogging process based on finite element computational analysis, which comprises the following steps of: establishing a finite element model of a blank, and performing parameter endowing and grid division; a heat transfer procedure and a deformation procedure required by cogging are combined into a flow chain; finite element analysis software is used for sequentially calculating blanks in the procedures included in the process chain, and the reasonability of the cogging process is confirmed according to the calculation result. According to the process, temperature field changes in the technological processes of blank preheating, blank transferring, air cooling after upsetting, secondary heating, multi-pass drawing-out and the like and the influence of the temperature field changes on a strain field are considered, the cogging process for ensuring the forging penetration and deformation uniformity of the forging stock for the large-size cast ingot is determined, and guidance can be provided for the cogging process design of the large-size cast ingot of the nickel-based high-temperature alloy.

Description

Technical Field

[0001] The invention belongs to the field of alloy manufacturing and relates to a high-temperature alloy ingot blanking process based on finite element calculation and analysis. Background Art

[0002] As the first hot deformation of high-temperature alloy materials, billet opening plays an important role in the entire production process, such as breaking the dendritic cast structure, fully refining the columnar grains, optimizing the size and morphology of the precipitated phase, reducing the critical strain required for dynamic recrystallization of the alloy during hot deformation, improving the machinability under high temperature conditions, and reducing crack sensitivity.

[0003] With the increasingly stringent service conditions and the requirement to reduce costs, the alloying degree of high-temperature alloys has increased accordingly, and the size of the smelting ingots has continued to expand, resulting in unfavorable conditions such as a narrow processing temperature range, low high-temperature plasticity, increased structural heterogeneity, and a large temperature drop on the ingot surface. Any carelessness in the temperature control and deformation of the billet surface will lead to severe cracking, resulting in high energy consumption and low yield rate in the billet opening process.

[0004] For the blanking of large ingots, free forging is still the most commonly used method. Due to the long production cycle of free forging, high test cost and many process parameters, the traditional method uses trial and error to optimize the process parameters, which cannot accurately analyze the influence of dimensional factors. At the same time, most of the numerical simulations of blanking only analyze the hot forming stage of a single upsetting or a single drawing process, without considering the heat loss process of the blank transfer and reheating process involved in the actual blanking process. In this process, the surface temperature of the blank is reduced due to heat transfer with the air; heat transfer will also occur in the upper and lower anvils of the blanking process and the upsetting process, and the clamps of the drawing process. Although the mold will also be preheated, the general preheating temperature of the mold is quite different from the hot forging temperature. Summary of the invention

[0005] In order to solve the technical problems existing in the prior art, the present invention provides a high-temperature alloy ingot blanking process based on finite element calculation and analysis, which takes into account the temperature field changes and their influence on the strain field during the process of billet preheating, billet transfer, air cooling after upsetting, secondary heating and multi-pass drawing, and determines the blanking process for large-size ingots to ensure the forging permeability and deformation uniformity of the forging billet, which can provide guidance for the design of the blanking process for large-size ingots of nickel-based high-temperature alloys.

[0006] In order to achieve the above technical effects, the present invention adopts the following technical solutions:

[0007] The present invention provides a high-temperature alloy ingot blanking process based on finite element calculation and analysis, the process comprising:

[0008] Establish the finite element model of the blank, assign parameters and divide the mesh;

[0009] Combine the heat transfer process and deformation process required for blanking into a process chain;

[0010] The finite element analysis software is used to calculate the blanks in the processes included in the process chain in turn, and the rationality of the blanking process is confirmed based on the calculation results.

[0011] As a preferred technical solution of the present invention, the finite element model includes upper and lower anvils for fixing the blank during the deformation process.

[0012] As a preferred technical solution of the present invention, the parameter assignment includes adding thermal physical property parameters of the blank material using a DEFORM-MO preprocessor.

[0013] As a preferred technical solution of the present invention, the grid division includes using an adaptive grid re-division algorithm.

[0014] As a preferred technical solution of the present invention, the heat transfer process includes any one of preheating, cooling and heating, or a combination of at least two of them.

[0015] As a preferred technical solution of the present invention, the deformation process includes upsetting and / or stretching.

[0016] As a preferred technical solution of the present invention, the calculation includes calculating the temperature field and strain field of the blank.

[0017] As a preferred technical solution of the present invention, the finite element analysis calculation results of the previous process included in the process chain are transferred to the subsequent process through a .DB data file for use in the finite element analysis calculation of the subsequent process.

[0018] As a preferred technical solution of the present invention, the calculation process of the heat transfer step includes heat radiation and heat convection between the blank and the environment.

[0019] As a preferred technical solution of the present invention, the calculation process of the heat transfer step includes the friction and heat transfer between the blank and the upper and lower anvils.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] (1) The present invention provides a high-temperature alloy ingot blanking process based on finite element calculation and analysis. The process uses a full three-dimensional finite element method to perform deformation and heat transfer coupling analysis on the blanking process of a large ingot, thereby achieving accurate simulation of thermal deformation, heat exchange, and heat transfer processes. Compared with the blanking simulation of a single process, it is closer to the actual blanking production process;

[0022] (2) The invention provides a high-temperature alloy ingot blanking process based on finite element calculation and analysis, which can provide a technical path for optimizing the blanking process parameters of high-temperature alloys, pre-simulate and optimize the blanking process on a computer, reduce the dependence on actual forging experiments, and help improve the blanking yield rate of high-temperature alloys, reduce the processing cycle, and achieve the purpose of grain refinement and crushing the cast structure during blanking;

[0023] (3) The invention provides a high-temperature alloy ingot blanking process based on finite element calculation and analysis. The process is used to optimize the blanking process of similar ingots. The method can also be used to simulate and model the blanking process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of overall modeling of the upsetting-stretching process in the high-temperature alloy ingot blanking process based on finite element calculation and analysis provided in Example 1 of the present invention;

[0025] Figure 2 A schematic diagram of a process for forming a high-temperature alloy ingot based on finite element calculation and analysis provided in Example 1 of the present invention;

[0026] Figure 3 A simulation result diagram of the temperature field of 1150°C upsetting-1120°C drawing in the high-temperature alloy ingot blanking process based on finite element calculation analysis provided in Example 1 of the present invention;

[0027] Figure 4 This is a diagram of simulation results of the opening strain field of 1150°C upsetting-1120°C drawing in the high-temperature alloy ingot opening process based on finite element calculation analysis provided in Example 1 of the present invention.

[0028] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0029] The technical solution of the present application is further described below through specific implementation methods.

[0030] The specific embodiment of the present invention provides a high-temperature alloy ingot blanking process based on finite element calculation and analysis, and the process includes:

[0031] Establish the finite element model of the blank, assign parameters and divide the mesh;

[0032] Combine the heat transfer process and deformation process required for blanking into a process chain;

[0033] The finite element analysis software is used to calculate the blanks in the processes included in the process chain in turn, and the rationality of the blanking process is confirmed based on the calculation results.

[0034] In a specific embodiment of the present invention, the finite element model includes upper and lower anvils for fixing the blank in the deformation process. For example, in the upsetting process, the upper and lower anvils can be regarded as wide flat anvils; in the drawing process, the upper and lower anvils can be regarded as two pairs of holders to ensure that the blank can remain horizontal and stable when the upper and lower anvils are axially fed.

[0035] In a specific embodiment of the present invention, the sizes of the upper and lower anvils in the finite element model are adjusted according to the size of the high-temperature alloy ingot, which is not specifically limited herein.

[0036] In a specific embodiment of the present invention, the DEFORM-MO preprocessor is used to add thermal physical property parameters of the billet material, and the high-temperature alloy manual is referred to and selected from the DEFORM material database.

[0037] In a specific embodiment of the present invention, the blank and the upper and lower anvils are meshed, and an adaptive remeshing algorithm (ALE) is used to continue the simulation when the old mesh is excessively distorted.

[0038] In a specific embodiment of the present invention, the deformation and heat exchange and heat transfer processes are comprehensively considered, and the Conjugate gradient solver and the Lagrangian incremental simulation method can be used, but they are not limited to the above solvers and simulation methods, which can be reasonably selected according to the material of the blank, the heat transfer and the requirements of the deformation process.

[0039] In a specific embodiment of the present invention, the heat transfer process may include preheating, cooling and heating, etc. The heat transfer method may be heat transfer with the environment (air), such as air cooling, or heat transfer inside the device, such as heating inside the heating device, etc., but it is not limited to the above-mentioned heat transfer processes. Other heat transfer processes suitable for high-temperature alloy ingots can also be used.

[0040] In a specific embodiment of the present invention, the deformation process may include upsetting and / or stretching, but is not limited to the above deformation processes. Other deformation processes suitable for high-temperature alloy ingot blanking may also be used.

[0041] In a specific embodiment of the present invention, the number and order of each heat transfer process and deformation process can be selected according to the needs of high-temperature alloy ingot opening. The number can be 0, that is, the corresponding process is not used. The heat transfer process and the deformation process can be performed alternately or continuously.

[0042] In a specific embodiment of the present invention, the Air Transfer process step can be selected to simulate the process of transferring the blank from the preheating temperature to the deformation process.

[0043] In a specific embodiment of the present invention, a Forming process step or a Cogging process step can be selected to simulate the deformation process of the blank.

[0044] In a specific embodiment of the present invention, an Air Transfer process step may be selected to simulate the air heat transfer process before the blank is transferred to the heating device after the blank deformation process is completed.

[0045] In a specific embodiment of the present invention, the Heating Express process can be selected to simulate the heating process of the blank in the heating device.

[0046] In a specific embodiment of the present invention, the parameters of the heat transfer process and the deformation process in each process chain in the billeting of the high-temperature alloy ingot, such as temperature, pressing amount, pressing speed of the press, etc., can be adjusted according to the material of the billet and the requirements of billeting, and are not specifically limited here.

[0047] In the present invention, an overall model of the blanking and upsetting process is established, and the MO multi-process forming module of the finite element software is used to form a process chain of various heat transfer and deformation processes according to the actual blanking process sequence. By transferring the .DB data file obtained after the blank calculation, the calculation result of the previous process is transferred, and the blanking process parameters are set once or continuously to simulate the actual blanking process. A calculation process is designed, which is different from the ordinary single process in that the temperature field changes of the process such as blank preheating, blank transfer, air cooling after upsetting, secondary heating and multi-pass drawing and their influence on the strain field are taken into account, and the blanking process of large-size ingots to ensure the forging permeability and deformation uniformity of the forging blank is determined.

[0048] In a specific embodiment of the present invention, based on the temperature field and equivalent strain field results obtained by finite element analysis of the overall high-temperature alloy ingot, the mutual influence of various parameters in the whole process is quantitatively analyzed.

[0049] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0050] Example 1

[0051] This embodiment provides a high-temperature alloy ingot blanking process based on finite element calculation and analysis, the process comprising:

[0052] (1) Finite element modeling: The overall modeling of the upsetting-stretching process is as follows: Figure 1As shown in the figure, the original ingot size is Ф660×2000mm, and the height-to-diameter ratio is 3; the upsetting process adopts the Forming process step, and the upper and lower anvils have the size of Ф1000×300mm, which can be regarded as wide flat anvils; the drawing process adopts the Cogging process step, and the upper and lower flat anvils have the size of Ф1000×450×300mm, and the upper and lower anvils have the chamfer R=60mm. Two pairs of holders are used to ensure that the billet can maintain horizontal stability when the upper and lower anvils are axially fed; the billet will undergo high plastic deformation at high temperatures, so the upper and lower anvils are set as Rigid rigid anvils, and the billet is set as Plastic plastic material to simplify finite element analysis;

[0053] (2) Use the DEFORM-MO preprocessor to add the thermal properties of the billet material, refer to the high-temperature alloy manual, and select WASPALOY [1800-2050F (980-1120C)] in the DEFORM material database; mesh the billet and the upper and lower anvils, and use the adaptive meshing algorithm (ALE) to continue the simulation when the old mesh is excessively distorted. Considering the deformation, heat exchange, and heat transfer process, the Conjugate gradient solver and Lagrangian incremental simulation method are used;

[0054] (3) Setting of multiple steps of blanking process MO: According to the actual blanking process, formulate the steps of finite element modeling of the whole process of blanking process, comprehensively consider the deformation process (process 2 upsetting + process 5 drawing) and heat transfer process (process 1 air heat transfer + process 3 air heat transfer + process 4 billet heating). The whole process of blanking is divided into five consecutive steps, 1 air cooling after billet preheating Air Transfer - 2 upsetting Forming - 3 air cooling after billet upsetting Air Transfer - 4 secondary heating Heating Express - 5 drawing Cogging; the multi-step configuration of blanking process MO is as follows Figure 2 As shown, the .DB data file obtained after the blank calculation is transferred between processes to transfer the calculation results of the previous process;

[0055] (4) In process 1, the Air Transfer step is selected to simulate the process of transferring the blank to the upsetting process after reaching the preheating temperature: after the blank is preheated, in the process of transferring to the upsetting lower anvil, the blank exchanges heat with the air to reduce the temperature. In order to ensure that the temperature drop is not too large and the temperature gradient does not increase, which affects the optimal temperature of subsequent forming, the air heat transfer time is set to 15s; considering the thermal radiation and thermal convection between the workpiece and the surrounding environment, the ambient temperature is set to 20℃ as the reference point for the calculation of convection and radiation heat transfer. For the heat transfer from the blank to the environment, the convection coefficient is set to 0.02N / s / mm / ℃, the preheating temperature of the upper and lower anvils is 200℃, and the preheating temperature of the blank is 1150℃. Considering the effects of the sheath and lubricant, the equivalent friction coefficient between the workpiece and the die is 0.2;

[0056] (5) Select the Forming process step in process 2 to simulate the upsetting process of the blank: the workpiece and the lower anvil remain constant, the upper anvil is used as the Primary die, the movement rate is set to 30 mm / s, and the stroke is 600 mm to simulate the case where the upsetting pressure is 30%. Since the height-to-diameter ratio is greater than 3, a double drum phenomenon occurs at the end of upsetting. The minimum unit size of the mesh division is 19 mm, so the total step length is set to 100 steps, 6 mm / step;

[0057] (6) In process 3, the Air Transfer process is selected to simulate the air heat transfer process of the blank after upsetting and before it is transferred to the furnace for reheating: the time interval is set to 90 s, the ambient temperature is set to 20 °C, and the convection coefficient of the heat transfer from the blank to the environment is set to 0.02 N / s / mm / °C;

[0058] (7) In process 4, select the Heating Express process step to simulate the secondary heating process of the billet in the heating furnace: set the heating furnace temperature to 1120°C and the heating time to 3600s to ensure that the large billet is heated to the target second heating temperature as a whole;

[0059] (8) In process 5, select the Cogging step to simulate the billet drawing process: the billet mesh is inherited from the distorted mesh after the upsetting process, and the forging speed of the upper and lower anvils is 30 mm / s. A total of 4 drawing passes are set, and the system automatically calculates the bite to automatically calculate the number of bites in each pass; the feed amount of the upper anvil is 300 mm each time it is pressed down, so when the width of the upper anvil is 450 mm, the anvil connection amount is 150 mm. The thickness of the billet after each pressing is 600 mm, so as to obtain a square billet with a side length of about 600 mm after drawing. After each pass, the billet is rotated 90°, and the heat transfer time is set to 5s. The heat transfer coefficient at the workpiece-die interface is set to 11N / sec / mm / ℃.

[0060] The simulation results of the temperature field of the blanking process at 1150℃ upsetting and 1120℃ drawing are as follows: Figure 3 As shown in the figure, the whole upsetting heat transfer process is divided into six stages:

[0061] In stage 1, before the original billet at the pre-forging heating temperature of 1150℃ is transferred to the next upsetting process by the robot, the outer surface temperature drops by 20-30℃ due to heat convection and heat radiation with the air; while the temperature of the core of the ingot is evenly distributed, basically at the preset first-fire temperature of 1150℃;

[0062] In stage 2, after upsetting, the temperature of the blank surface rose to 1160℃ due to the temperature rise effect of the thermal processing process, which was about 10℃ higher than the preheating temperature. The temperature rise effect was not large, which showed that the selected upsetting deformation was appropriate to avoid overheating inside the blank. However, due to the contact between the upper and lower surfaces and the upper and lower anvil surfaces, more heat transfer occurred, causing the temperature to drop to 366℃, which was 200℃ higher than the preheating temperature of the upper and lower anvils.

[0063] In stage 3, it is the temperature field distribution when the blank is transferred to the heating furnace after upsetting. At the first-fire temperature of 1150℃, the core of the blank maintains the temperature rise of 1160℃ after upsetting, and only the surface temperature drops significantly, with an average drop of about 140℃. Considering that the blank transfer time is 90s and the cooling rate at the end face and end corner is relatively large, the temperature drop is normal. The subsequent process optimization can consider appropriately reducing the blank transfer time to reduce the temperature drop.

[0064] In stage 4, after the heating furnace is heated to the second-fire temperature of 1120℃, after 3600s of heating time, it can be seen that the surface of the billet including the two end faces reaches the second-fire temperature of 1120℃. However, due to the large size of the billet, the temperature of its core is distributed in a layered gradient. The core part of about 700mm still maintains the first-fire temperature of 1150℃. The cooling rate of the core is low, which hinders the shrinkage of the billet surface and makes its interior mainly in a compressive stress state.

[0065] In stage 5, as the upper and lower anvils contact the surface of the billet during the drawing process, a large amount of heat transfer obviously occurs in the contact part, causing its temperature to drop to the lowest temperature of the entire billet, 896°C. In addition, the edges of the two end faces, due to their small cross-sectional area, undergo heat transfer with the air, and the temperature is also reduced to about 900°C. It can be seen from the temperature distribution in its core that after two drawing processes, the temperature rise effect inside the billet is not obvious, and it still maintains at 1150°C. This is probably because the accumulated strain in the second pass is not enough, so the temperature does not rise much. This also shows that only two drawing passes cannot achieve the effect of breaking the uniform grains of the cast structure for the opening of large ingots.

[0066] In stage 6, i.e., four-pass drawing, after the entire upsetting and drawing process is completed, the temperature distribution on the surface of the billet is relatively uniform, and the overall outer surface reaches about 992°C.

[0067] The simulation results of the strain field of the blank during 1150℃ upsetting and 1120℃ drawing are as follows: Figure 4 As shown in the figure, the equivalent strain distribution of the entire upsetting and drawing process is divided into three stages: 1. After upsetting, 2. After two-pass drawing, 3. After four-pass drawing:

[0068] In stage 1, as the stroke of the upper anvil continues to increase, the equivalent strain value of the entire billet continues to increase. By the end of upsetting, most of the equivalent strain values ​​on the billet surface reach between 0.334 and 0.445. However, due to the friction between the billet and the upper and lower anvils during high-temperature upsetting, the contact parts between the two ends of the cylindrical billet and the upper and lower anvils belong to the difficult deformation area and exist throughout the entire upsetting process. The equivalent strain value does not increase much, only reaching 0.112. It can be seen from the equivalent strain distribution cloud map of its 1 / 2 cross section that under a deformation of 30%, the core of the billet can be basically forged through by selecting this forging parameter, and the compaction effect is relatively good. At the same time, since the billet is an axisymmetric workpiece, its equivalent strain distribution is roughly symmetrical, and the structure after forging is layered.

[0069] In stage 2, the equivalent strain distribution of the part where the blank contacts the upper and lower anvils increases significantly. After two stretching passes, the equivalent strain value of most parts of the blank can reach more than 1.06.

[0070] In stage 3, after four drawing passes, the distribution is basically 1.37, and the compaction effect of the core of the billet is very good, indicating that the billet has been basically forged through. Compared with the equivalent strain of the single drawing stage, the effect of the entire billet opening process on the equivalent strain is very significant, and the cumulative strain distribution in the core has also reached the level of complete recrystallization of the structure, achieving the purpose of billet opening to refine the grains and break the cast structure.

[0071] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0072] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0073] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0074] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A high-temperature alloy ingot forming process based on finite element calculation and analysis, characterized in that: The process comprises: Establish the finite element model of the blank, assign parameters and divide the mesh; Combine the heat transfer process and deformation process required for blanking into a process chain; The finite element analysis software is used to calculate the blanks in the processes included in the process chain in turn, and the rationality of the blanking process is confirmed based on the calculation results.

2. The process according to claim 1, characterized in that The finite element model includes upper and lower anvils used to fix the blank during the deformation process.

3. The process according to claim 1, characterized in that The parameter assignment includes adding thermal physical property parameters of the blank material using a DEFORM-MO preprocessor.

4. The process according to claim 1, characterized in that The meshing includes using an adaptive remeshing algorithm.

5. The process according to claim 1, characterized in that The heat transfer process includes any one of preheating, cooling and heating or a combination of at least two of them.

6. The process according to claim 1, characterized in that The deformation process includes upsetting and / or drawing.

7. The process according to claim 1, characterized in that The calculation includes calculating the temperature field and strain field of the blank.

8. The process according to claim 1, characterized in that The finite element analysis calculation results of the preceding process included in the process chain are transferred to the subsequent process via a .DB data file for use in the finite element analysis calculation of the subsequent process.

9. The process according to claim 1, characterized in that The calculation process of the heat transfer step includes heat radiation and heat convection between the blank and the environment.

10. The process according to claim 2, characterized in that The calculation process of the heat transfer step includes the friction and heat transfer between the blank and the upper and lower anvils.

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