A casting process simulation method based on cooling rate

Abstract

The present invention belongs to the technical field of numerical simulation of casting process, and specifically relates to a casting process simulation method based on cooling rate. The method disclosed in the present invention sets different solidification solid phase ratio curves according to the different cooling rates in the solidification process, and controls the latent heat release and the melt flow behavior in the mushy zone during the solidification process through the solid phase ratio. The specific steps include: ① preliminarily evaluating the cooling rate of different positions of the ingot, ② determining the solidification solid phase ratio curve according to different cooling rates, ③ establishing the energy conservation equation, ④ establishing the momentum conservation equation, ⑤ solving the coupling equations of the temperature field and the flow field, and ⑥ processing the simulation results. The present invention takes into account the influence of different cooling rates on the solidification solid phase ratio during the casting process, and more realistically reflects the heat release and the behavior of the mushy zone in the solidification process, which is closer to reality and improves the accuracy of the solidification simulation.

Description

Technical Field

[0001] The invention belongs to the technical field of numerical simulation of casting process, and in particular relates to a casting process simulation method based on cooling rate. Background Art

[0002] Metal casting is a manufacturing process that melts metal and then cools and solidifies it through a certain mold to form parts or products of specific shapes and sizes. It is crucial in the metal processing industry. Casting numerical simulation is a method that uses computer technology to simulate and analyze the casting process. It plays an important role in casting process optimization, defect prediction and product quality improvement. Numerical simulation can optimize the process before casting production, predict and adjust various parameters in the filling, solidification and cooling processes, thereby reducing trial and error costs and improving production efficiency. Numerical simulation can also predict the microstructure and macroscopic properties of castings, and help select the most appropriate materials and process parameters to meet specific performance requirements. By simulating the metal filling and solidification process, it is possible to predict defects such as shrinkage cavities, shrinkage porosity, and cracks that may appear in castings, which is of great significance to improving the technical level, product quality and market competitiveness of the foundry industry.

[0003] Numerical simulation of casting involves the solidification process, in which the solidification solid phase ratio is a quantitative parameter describing the degree of solidification. The equilibrium solidification model or Scheil model is usually used to describe the solidification behavior of the alloy. For example, Venneker et al. [Venneker BC H, Katgerman L. Modelling issues in macrosegregation predictions in directchill castings[J]. , 2003, 2(2002): 149–159.] adopt the equilibrium solidification model in the casting process:

[0004] (1)

[0005] Where T is the temperature, is the solid phase ratio, which is a function of temperature T, k is the solidification distribution coefficient, is the liquidus temperature, is the solidus temperature, is the melting point temperature of pure metal.

[0006] Or use the Scheil solidification model [Lebon GSB, Li HT, Patel JB, Assadi H, FanZ. Elsevier Inc., 2020. Numerical modelling of melt-conditioned direct-chillcasting[J]. Applied Mathematical Modelling, 2020, 77: 1310–1330.], such as Figure 1 As shown, the solid fraction is a function of the temperature T.

[0007] However, during the solidification process of metal, the solidification solid phase ratio of casting is related to the cooling rate. For example, when the cooling rate is slow, the liquid phase diffuses more fully and the solidus temperature is higher; when the cooling rate is faster, the solute atoms have no time to diffuse, and most of the solute atoms are dissolved in the matrix, and the solidus temperature is lower. Figure 2 During the solidification process, due to the limitation of cooling conditions, the cooling rate inside the ingot is often uneven. Generally, the core cools slowly, while the surface of the ingot cools quickly. For the casting process, it is unreasonable to use one solidification solid phase ratio model for the entire ingot, which leads to unreasonable simulation results and may be misleading when studying solidification problems or guiding production. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention provides a casting process simulation method based on cooling rate. The method fully considers the cooling rates of different regions of the ingot during the casting process, determines the solid phase ratio of the corresponding region according to different cooling rates, and then further simulates the solidification heat release of the casting process and the melt flow in the mushy zone according to the solid phase ratio. The present invention specifically includes the following contents:

[0009] A casting process simulation method based on cooling rate comprises the following steps:

[0010] S1, obtain cooling rate: obtain the cooling rate at different ingot positions P , establish the cooling rate Functional relationship with the ingot position P;

[0011] S2, obtain solidification solid phase ratio curve: according to different cooling rates Get solidification solid fraction curve , or according to the ingot position Determine the solidification solid fraction curve , T represents temperature;

[0012] S3, release the latent heat of crystallization in proportion to the solid phase ratio, and establish the energy conservation equation:

[0013] , (2)

[0014] or ,

[0015] in,

[0016] Indicates density;

[0017] represents the velocity vector;

[0018] Indicates time;

[0019] represents thermal enthalpy;

[0020] represents thermal conductivity;

[0021] represents the latent heat of crystallization;

[0022] represents the solid phase ratio;

[0023] S4, simulates the flow of liquid between dendrite networks by infiltration during solidification. The permeability of the infiltration is related to the solid phase ratio, and the momentum conservation equation is established:

[0024] (3)

[0025] in,

[0026] represents equivalent viscosity;

[0027] represents the source term of the penetration Darcy force, which is a function of the solid fraction;

[0028] S5, in combination with the specific ingot shape, according to the energy conservation equation and momentum conservation equation, a coupling model of the temperature field and the flow field is established and solved, and the temperature field and the flow field of the casting solidification process are further obtained.

[0029] Furthermore, in step S1, the cooling rate at different ingot positions P is obtained. The method is to embed thermocouples for measurement or to establish a numerical simulation model of the casting process for calculation.

[0030] Furthermore, the method for establishing the numerical simulation model of the casting process is: based on the Scheil solidification model, the Level model or other suitable models, combined with the ingot shape, to establish the numerical simulation model of the casting process. It should be noted that the model used in this step is not limited to the Scheil solidification model or the Level model, and only two feasible examples are given here.

[0031] Further, in step S2, according to different cooling rates Calculate the solidification solid phase ratio curve of the corresponding ingot position P The method is: according to different cooling rates , different cooling rates were calculated using the Back diffusion model using software such as Thermo-calc The corresponding solidification curve It should be noted that the software used in this step is not limited to Thermo-calc software, and this is just a feasible example.

[0032] Further, in step S2, according to different cooling rates Calculate the solidification solid phase ratio curve of the corresponding ingot position P The method is: use DSC and other experimental methods to measure different cooling rates Solidification curve under .

[0033] Furthermore, step S4 adopts the Blake-Kozeny model to describe the Darcy force source term. It should be noted that the model used in this step is not limited to the Blake-Kozeny model, and this is just a feasible example.

[0034] Furthermore, in step S5, a coupled solution model of temperature field and flow field is established by combining the ingot shape with Fluent software, etc. It should be noted that the software used in this step is not limited to Fluent software, and this is just a feasible example.

[0035] Furthermore, the method further includes step S6: processing the casting process simulation results.

[0036] Further, the processing includes: extracting physical fields / quantities of the casting process according to the casting process simulation results. The physical fields / quantities represent physical fields and / or physical quantities.

[0037] Furthermore, the physical fields / quantities include temperature field, flow field, cooling rate, and / or liquid cavity morphology.

[0038] The processing includes: extracting the temperature field, flow field, cooling rate, and / or liquid cavity morphology of the casting process according to the casting process simulation results.

[0039] Beneficial effects of the present invention:

[0040] The present invention provides a casting process simulation method based on cooling rate. The method disclosed in the present invention sets different solidification solid phase ratio curves according to different cooling rates during the solidification process, and controls the latent heat release and the melt flow behavior in the mushy zone during the solidification process through the solid phase ratio. The specific steps include: ① preliminary evaluation of the cooling rate at different positions of the ingot, ② determination of the solidification solid phase ratio curve according to different cooling rates, ③ establishment of energy conservation equation, ④ establishment of momentum conservation equation, ⑤ solving the coupled equations of temperature field and flow field, ⑥ simulation result processing. The present invention takes into account the influence of different cooling rates on the solidification solid phase ratio during the casting process, more realistically reflects the heat release and the behavior of the mushy zone during the solidification process, is closer to reality, and improves the accuracy of solidification simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Scheil solidification model adopted for semi-continuous casting simulation;

[0042] Figure 2 The effect of cooling rate on the solid phase ratio during solidification;

[0043] Figure 3 The cooling rate measurement results of 7050 alloy with a diameter of 300mm;

[0044] Figure 4 The liquid cavity measurement and simulation results of 7050 alloy ingot with a diameter of 300mm;

[0045] Figure 5 Cooling rate distribution of 5A06 alloy flat ingot with specification of 420×1620mm. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments shown below do not limit the invention content described in the claims. In addition, the entire contents of the structures represented by the following embodiments are not limited to those necessary as solutions to the invention described in the claims. Example 1

[0047] The simulation method disclosed in the present invention is used to carry out numerical simulation of solidification during semi-continuous casting of 7050 aluminum alloy round ingots. The ingot diameter is 300 mm, the casting temperature is 690° C., the casting speed is 60 mm / min, the cooling water volume is 75 L / min, and the cooling water temperature is 25° C.

[0048] The simulation method specifically comprises the following steps:

[0049] S1, obtain cooling rate: During the casting process, the cooling curves at different radial positions of the ingot are measured by pre-embedded thermocouples to obtain the cooling rates at different positions of the ingot, and the distribution law of the cooling rate along the radial direction of the ingot is obtained by fitting, such as Figure 3 shown.

[0050] S2, obtain solidification solid phase ratio curve: according to different cooling rates, the solidification curve under the cooling rate conditions is calculated by the Backdiffusion model of Thermo-calc software. , and determine the solidus temperature. It is a function of the ingot position P. Considering the symmetry of the ingot, the solid phase ratio is formed with the temperature and the radial distance of the ingot. Function .

[0051] S3, establish the energy conservation equation:

[0052] (4),

[0053] in, represents the crystal density; represents the velocity vector of crystallization; Indicates crystallization time; represents the crystal enthalpy; represents the thermal conductivity of the crystal; represents the latent heat of crystallization; Represents the solid fraction.

[0054] S4, the Blake-Kozeny model is used to describe the Darcy force source term and establish the momentum conservation equation:

[0055] (5)

[0056] in, Represents equivalent viscosity; the last term is the Darcy force source term, is the permeability of the mushy zone.

[0057] S5, a coupled solution model of the temperature field and flow field of the semi-continuous casting process of Φ300mm 7050 aluminum alloy was established by Fluent software, and the temperature field and flow field were obtained by solving and calculating on a computer.

[0058] S6, after the calculation is completed, the numerical simulation results are processed to extract the liquid cavity morphology according to the different solid phase ratios at different positions. Example 2

[0059] The method disclosed in the present invention is used to carry out numerical simulation of solidification during semi-continuous casting of 5A06 aluminum alloy 420×1620 mm flat ingot, with a casting temperature of 700°C, a casting speed of 50 mm / min, and a cooling water volume of 20 m 3 / h, the cooling water temperature is 20℃.

[0060] The specific steps include:

[0061] S1, based on the Scheil solidification model, a numerical simulation model of the casting process of 5A06 with a specification of 420×1620 mm was established to obtain the cooling rate distribution of the casting process, such as Figure 5 shown.

[0062] S2, according to different cooling rates, the solidification curves under the conditions of 0.5K / s, 1 K / s, 2K / s, 3K / s, 4K / s, and 5K / s were obtained by DSC experimental measurement. , and determine the solidus temperature, and obtain the solidification curve at other cooling rates by interpolation table lookup method In the steady-state case, the cooling rate Considering the symmetry of the flat ingot, a 1 / 4 symmetric model is established to form a function of the solid phase ratio, temperature and ingot position (x, y). .

[0063] S3, establish the energy conservation equation:

[0064] (8)

[0065] S4, material Blake-Kozeny model describes the Darcy force source term and establishes the momentum conservation equation:

[0066] (9)

[0067] The last term is the Darcy force source term, The permeability is taken for the paste.

[0068] S5, a coupled solution model of the temperature field and flow field of the semi-continuous casting process of 5A06 aluminum alloy with a specification of 420×1620mm was established by Fluent software, and the temperature field and flow field were obtained by solving and calculating on a computer.

[0069] S6, after the calculation is completed, the numerical simulation results are analyzed and the cooling rate is evaluated. If there is a large difference with the result of step 1, return to step 1 and update the cooling rate, and repeat steps 2-6 until the cooling rate is stable. The numerical simulation method described in this embodiment fully considers the influence of different cooling rates on the solidification solid phase ratio during the casting process, more realistically reflects the heat release behavior of the solidification process, is closer to reality, and can effectively improve the accuracy of the solidification simulation.

[0070] Comparative Example 1

[0071] This comparative example adopts the equilibrium solidification model to describe the solidification behavior of the alloy. The casting method and ingot specifications are the same as those in Example 1, that is, a casting numerical simulation is carried out for semi-continuous casting of 7050 aluminum alloy round ingots. The ingot diameter is 300 mm, the casting temperature is 690°C, the casting speed is 60 mm / min, the cooling water volume is 75 L / min, and the cooling water temperature is 25°C.

[0072] This comparative example specifically comprises the following steps:

[0073] S1, the solid phase ratio of 7050 alloy is calculated by the equilibrium solidification model (using formula 1), the liquidus temperature is 630℃, the liquidus temperature of pure aluminum is 660℃, and the distribution coefficient is 0.185. The solidification curve of the whole ingot is used.

[0074] S2, establish the energy conservation equation:

[0075] (6)

[0076] S3, the Blake-Kozeny model is used to describe the Darcy force source term and the momentum conservation equation is established:

[0077] (7)

[0078] The last term is the Darcy force source term, is the permeability of the mushy zone.

[0079] S4, using Fluent software to establish a coupled solution model of the temperature field and flow field in the semi-continuous casting process of Φ300mm 7050 aluminum alloy, and perform solution calculations on a computer to obtain the temperature field and flow field.

[0080] S5, after the calculation is completed, the numerical simulation results are processed and the liquid cavity morphology is extracted according to the isothermal surface of the solidus temperature T=523℃.

[0081] The prediction results of the liquid cavity morphology and the experimental measurement results of Example 1 and Comparative Example 1 are as follows: Figure 4As shown, by comparing with the experimental measurement results, it can be seen that compared with Comparative Example 1, the simulation method described in Example 1 is more accurate in predicting the liquid cavity morphology.

[0082] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A casting process simulation method based on cooling rate, characterized in that: The following steps are involved: S1, obtain cooling rate: obtain the cooling rate at different ingot positions P , establish the cooling rate Functional relationship with the ingot position P; S2, obtain solidification solid phase ratio curve: according to different cooling rates Get solidification solid fraction curve , or according to the ingot position Determine the solidification solid fraction curve , the specific method is: According to different cooling rates, the solidification curves under the cooling rate conditions are calculated by the Back diffusion model of the Thermo-calc software. , and determine the solidus temperature, since It is a function of the ingot position P. Considering the symmetry of the ingot, the solid phase ratio is formed with the temperature and the radial distance of the ingot. Function ; or, According to different cooling rates, the solidification curves at 0.5K / s, 1K / s, 2K / s, 3K / s, 4K / s, and 5K / s were obtained through DSC experimental measurement. , and determine the solidus temperature, and obtain the solidification curve at other cooling rates by interpolation table lookup method , in the steady state, the cooling rate It is a function of position. Considering the symmetry of the flat ingot, a 1 / 4 symmetric model is established to form a function of the solid phase ratio, temperature and ingot position (x, y). ; Said T represents temperature; S3, release the latent heat of crystallization in proportion to the solid phase ratio, and establish the energy conservation equation: ， or , in, Indicates density; represents the velocity vector; Indicates time; represents thermal enthalpy; represents thermal conductivity; represents the latent heat of crystallization; represents the solid phase ratio; S4, considering that the liquid phase flows between the dendrite networks by infiltration during solidification, the permeability of the infiltration is related to the solid phase ratio, and the momentum conservation equation is established: in, represents equivalent viscosity; represents the penetration Darcy force source term, and is the solid phase rate The function of or ; is the permeability of the mushy zone; S5, in combination with the specific ingot shape, according to the energy conservation equation and momentum conservation equation, a coupling model of the temperature field and the flow field is established and solved.

2. A casting process simulation method based on cooling rate according to claim 1, characterized in that: Step S1: obtaining the cooling rate at different ingot positions P The method is to embed thermocouples for measurement or to establish a numerical simulation model of the casting process for calculation.

3. A casting process simulation method based on cooling rate according to claim 2, characterized in that: The method for establishing the numerical simulation model of the casting process is: based on the Scheil solidification model or the Level model, combined with the ingot shape, to establish the numerical simulation model of the casting process.

4. A casting process simulation method based on cooling rate according to claim 1, characterized in that: Step S2: According to different cooling rates Calculate the solidification solid phase ratio curve of the corresponding ingot position P The method is: according to different cooling rates , different cooling rates were calculated by Back diffusion solidification model The corresponding solidification curve .

5. The casting process simulation method based on cooling rate according to claim 1, characterized in that: Step S2: According to different cooling rates Calculate the solidification solid phase ratio curve of the corresponding ingot position P The method is to use experimental methods to measure different cooling rates Solidification curve under .

6. A casting process simulation method based on cooling rate according to claim 1, characterized in that: Step S5 uses simulation software combined with the ingot shape to establish a coupled solution model for the temperature field and the flow field.

7. The casting process simulation method based on cooling rate according to any one of claims 1 to 6, characterized in that: The method further includes step S6: processing the casting process simulation results.

8. A casting process simulation method based on cooling rate according to claim 7, characterized in that: The processing includes: extracting physical fields / quantities of the casting process according to the casting process simulation results.

9. A casting process simulation method based on cooling rate according to claim 8, characterized in that: The physical fields / quantities include temperature field, flow field, cooling rate, and / or liquid cavity morphology.

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