Prediction method of mechanical properties of different parts of aluminum alloy castings using solidification time

Abstract

The present invention provides a method for predicting the mechanical properties of different parts of an aluminum alloy casting using solidification time, including: S1, designing step specimens with different solidification times by combining different wall thicknesses with cold iron; S2, Procast simulation to obtain the solidification time of the step specimen, and taking the average value of the solidification time of three points in the middle and two ends of the tensile test bar as the solidification time corresponding to the mechanical properties of the alloy at this position; S3, casting the step specimen in kind to obtain the mechanical properties of alloys with different solidification times; S4: using a linear fitting method to process the mechanical property values ​​of aluminum alloys with different solidification times, and selecting a linearly related model as a prediction model; S5: simulation to obtain the solidification time of different parts of the aluminum alloy casting; S6: bringing the solidification time into the prediction model to predict the mechanical properties of different parts of the casting. The present invention solves the problem that the mechanical properties of aluminum alloy castings are difficult to predict, and provides a design basis and guidance for casting and casting process designers.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy production, and in particular to a method for predicting mechanical properties of different parts of an aluminum alloy casting by using solidification time. Background Art

[0002] At present, the wall thickness of aluminum alloy castings in actual production is not the same. Different wall thickness will cause different solidification time. The mechanical properties of aluminum alloy are greatly affected by solidification time. The shorter the solidification time, the better the mechanical properties of the alloy, and the longer the solidification time, the worse the mechanical properties of the alloy. This causes the mechanical properties of different parts of aluminum alloy castings to be different in actual production. For casting structure designers and casting process designers, if they can predict the mechanical properties of different parts of the casting according to the design during the design stage, they can correct the design in time to prevent the problem of unqualified mechanical properties in parts of the casting, which can shorten the development cycle and R&D cost of the casting.

[0003] At present, the mainstream method of mechanical property prediction is to perform simulation calculations through commercial software, but there is a certain deviation between the predicted mechanical properties and the actual mechanical properties of castings, which makes it difficult to guide production design, especially in the prediction of newly developed alloy castings. Due to the lack of key material thermophysical parameters, the deviation of the predicted value is often greater. Procast is a professional casting simulation software developed by ESI GROUP, which has powerful casting simulation functions. Import the model in Procast, perform meshing and set simulation parameters to obtain casting solidification time data in the Procast post-processing module.

[0004] Therefore, how to utilize the influence of solidification time on the mechanical properties of aluminum alloys to obtain the mechanical property values ​​of alloys with different solidification times in the design of step specimens, process the data using linear fitting methods, select models with strong linear relationships, and predict the mechanical properties of aluminum alloy castings is an issue that the industry urgently needs to solve. Summary of the invention

[0005] A main purpose of the present invention is to overcome at least one defect of the above-mentioned prior art and to provide a method for predicting the mechanical properties of different parts of aluminum alloy castings, which can utilize the influence of solidification time on the mechanical properties of aluminum alloy, obtain the mechanical property values ​​of alloys with different solidification times by designing step samples, process the data by linear fitting, select a model with a strong linear relationship, and predict the mechanical properties of aluminum alloy castings.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0007] According to one aspect of the present invention, a method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time is provided, comprising the following steps:

[0008] Step S1, designing step specimens with different solidification times by combining different wall thicknesses and chills, the sampling location must be free of defects, and the specimen size must be sufficient to produce a tensile test bar;

[0009] Step S2, Procast simulation to obtain the solidification time of the step sample, and the average value of the solidification time at the middle and two ends of the tensile test rod is used as the solidification time corresponding to the mechanical properties of the alloy at the middle position;

[0010] Step S3, casting a step sample to obtain mechanical properties of alloys with different solidification times, the mechanical properties including tensile strength, yield strength, elongation and hardness;

[0011] Step S4: using a linear fitting method to process the mechanical property values ​​of aluminum alloys with different solidification times, and selecting a linearly related model with a coefficient of variation greater than 0.9 as a prediction model for the mechanical properties of different parts of the aluminum alloy casting;

[0012] Step S5: Procast simulation to obtain the solidification time of different parts of the aluminum alloy casting;

[0013] Step S6: Bring the solidification time into the prediction model to predict the mechanical properties of different parts of the casting.

[0014] According to one embodiment of the present invention, step S1 comprises:

[0015] S1.1. Design the step specimen, and use the tensile test bar size and sampling plan as the design basis for the test plate size. The test bar size is used as the length of the test plate, and the number of samples taken for each test plate determines the width of the test plate. The typical wall thickness of aluminum alloy castings is selected as the wall thickness variable of the test plate.

[0016] S1.2. According to the characteristics of aluminum alloy, design an open pouring system, use chilled iron as the second variable, design step specimens with different solidification times, and draw the model in UG;

[0017] S1.3. Use Procast to simulate the process of the step specimen, and check the internal quality of the test plates with different wall thicknesses in the post-processing module to ensure that the process design is reasonable, the test plates are defect-free, and will not affect the mechanical properties.

[0018] According to one embodiment of the present invention, step S1 includes: designing stepped test plates with different wall thicknesses and arranging them horizontally on both sides of the runner, and using the cross runner to compensate for shrinkage of the test plates to ensure internal quality; sampling the stepped test plates with different wall thicknesses at equal distances in the horizontal direction to reduce the temperature difference in the length direction of the standard tensile test rod, thereby ensuring the correspondence between the mechanical properties and the solidification time.

[0019] According to one embodiment of the present invention, step S2 comprises:

[0020] S2.1. Import the model into Procast and divide the mesh of the stepped specimen in the pre-processing module;

[0021] S2.2. Set the casting process parameters of the casting in the cast module of Procast;

[0022] S2.3. In the post-processing module of Procast, select Solidification Time to view the solidification time data. Select the entity information view for the viewing method. Use the slicing function to select the actual sampling position of the test bar, and obtain the solidification time data at the center and both ends of the test bar;

[0023] S2.4. Take the average value of the solidification times at three points as the solidification time corresponding to the mechanical properties of the alloy at this position.

[0024] According to an embodiment of the present invention, the step S3 includes:

[0025] S3.1. Perform the modeling of the stepped specimen and pour the physical stepped specimen according to the casting and pouring processes of the alloy;

[0026] S3.2. Dissect the stepped specimen according to the sampling plan to prepare standard tensile test bars and hardness blocks;

[0027] S3.2. Obtain the mechanical properties of the alloy with different solidification times according to the test standards.

[0028] According to an embodiment of the present invention, the step S3 includes: making a wooden mold of the stepped specimen, using the wooden mold for modeling, filling resin sand on the surface of the pattern. When the uniform covering thickness reaches 50 - 100 mm, tamp it, continue to add resin sand and tamp it until it is full, and finally level it; melt the aluminum liquid according to the melting process of the alloy, pour it into the sand mold of the stepped specimen, clean it, take out the physical stepped specimen, dissect the stepped specimen according to the sampling plan to prepare Φ6 tensile test bars and hardness blocks, conduct tensile tests and hardness inspections, and obtain the mechanical property values.

[0029] According to an embodiment of the present invention, the step S4 includes:

[0030] S4.1. Process the mechanical property data of the alloy with different solidification times by using the linear fitting method;

[0031] S4.2. Conduct model screening and select the model with a coefficient of variation percentage > 0.9.

[0032] According to an embodiment of the present invention, the step S4 includes: processing the solidification time and mechanical property data by using the linear fitting method, and requiring that the obtained prediction model has a coefficient of variation percentage > 0.9;

[0033] Changes in system free energy before and after embryo formation: where ΔG v is the volume free energy, ΔG s It is the surface free energy. During the formation of the embryo, the liquid-solid phase transition will reduce the volume free energy, and the newly formed phase boundary will increase the surface free energy.

[0034] The condition for nucleation is that the growth of the embryo reduces the free energy of the system. Only when the initial radius r of the embryo is greater than the critical nucleation radius can the growth of the embryo reduce the free energy of the system. It can be seen that the critical nucleation radius is affected by supercooling and the properties of the substance itself. The higher the supercooling, the smaller the critical nucleation radius.

[0035] According to the Hall-Page formula: The strength of the material is affected by the grain size. The smaller the grain size, the higher the strength of the material. Conversely, the coarser the grain, the lower the strength of the material. The relationship between grain size and toughness is: βT c =lnB-ln C-ln√d, where β, B, and C are constants, Tc is the brittle transition temperature, and the mechanical properties of the alloy are directly affected by the solidification time. The linear fitting method is used to process the mechanical properties of alloys with different solidification times. The percentage coefficient of variation of the prediction model is used to screen the model and predict the mechanical properties of different parts of the aluminum alloy castings.

[0036] According to one embodiment of the present invention, step S5 comprises:

[0037] S5.1. Import the casting model into Procast and perform mesh division in the pre-processing module;

[0038] S5.2. Use the same casting simulation parameter setting scheme as the step specimen to set the casting simulation parameters of the casting;

[0039] S5.3. Perform a simulation of the casting.

[0040] According to one embodiment of the present invention, step S6 comprises:

[0041] S6.1. In the Procast post-processing module, select the part whose mechanical properties need to be predicted, use the entity information viewing function, and obtain the solidification time data of the casting in Solidification Time;

[0042] S6.2, inputting the obtained solidification values ​​into a mechanical prediction model;

[0043] S6.3. Compare the predicted mechanical property values ​​with the required values ​​of the castings to promptly identify problems with unqualified mechanical properties in thick and large parts of the castings;

[0044] S6.4. If any non-conformity occurs, modify the design and return to S5 until the mechanical properties of different parts of the casting meet the requirements.

[0045] It can be seen from the above technical scheme that the advantages and positive effects of the method for predicting mechanical properties of different parts of aluminum alloy castings using solidification time of the present invention are:

[0046] In the present invention, the mechanical properties of aluminum alloys are affected by solidification time. The method designs step samples to obtain mechanical property values ​​of alloys with different solidification times, processes data by linear fitting, and selects a model with a strong linear relationship to predict the mechanical properties of aluminum alloy castings. The present invention can well solve the problem that the mechanical properties of aluminum alloy castings are difficult to predict, provide design basis and guidance for casting and casting process designers, improve the quality of aluminum alloy casting products, and promote the market development of aluminum alloy castings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The present invention is a flowchart of the method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time.

[0048] Figure 2 This is a process diagram of step samples with different solidification times in the method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time of the present invention.

[0049] Figure 3 It is a schematic diagram of Procast simulation data of the solidification time of a step sample in the method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time of the present invention. DETAILED DESCRIPTION

[0050] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that the present invention will be comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar structures, and thus their detailed description will be omitted.

[0051] In the following description of different examples of the present invention, reference is made to the accompanying drawings, which form a part of the present invention and in which different exemplary structures, systems and steps that can implement multiple aspects of the present invention are shown by way of example. It should be understood that other specific schemes of components, structures, exemplary devices, systems and steps can be used, and structural and functional modifications can be made without departing from the scope of the present invention. Moreover, although the terms "top", "bottom", "front", "rear", "side", etc. may be used in this specification to describe different exemplary features and elements of the present invention, these terms are used herein only for convenience, such as according to the direction of the examples described in the accompanying drawings. Nothing in this specification should be construed as requiring a specific three-dimensional orientation of the structure to fall within the scope of the present invention.

[0052] Figure 1 The present invention is a flowchart of the method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time.

[0053] Figure 2 This is a process diagram of step samples with different solidification times in the method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time of the present invention.

[0054] Figure 3 It is a schematic diagram of Procast simulation data of the solidification time of a step sample in the method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time of the present invention.

[0055] like Figures 1 to 3 As shown, a method for predicting the mechanical properties of different parts of an aluminum alloy casting using solidification time of the present invention first designs a step sample with different solidification times, uses Procast software to simulate and obtain the solidification time of different parts of the step sample, casts the step sample and dissects it to obtain the mechanical property values ​​of alloys with different solidification times, uses linear fitting to process the mechanical property values ​​of alloys with different solidification times, and obtains a mechanical property prediction model based on alloys with different solidification times. When producing aluminum alloy castings, the casting is simulated using Procast software to obtain the solidification time data of the casting, and then the prediction model is used to predict the mechanical properties of different parts of the aluminum alloy casting. The present invention can help casting designers and casting process designers to predict the mechanical properties of castings in the design stage, timely discover the problem of unqualified mechanical properties of local castings, correct the design, shorten the production cycle of castings, save the development cost of castings, and has great application value.

[0056] A method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time of the present invention comprises the following steps:

[0057] S1: Design step specimens with different solidification times;

[0058] S2: Procast simulation to obtain the solidification time of different parts of the step specimen;

[0059] S3: Casting step specimens to obtain mechanical property values ​​corresponding to different solidification times;

[0060] S4: The mechanical property prediction model of aluminum alloy based on solidification time is obtained by linear fitting;

[0061] S5: Procast simulation to obtain the solidification time of different parts of the casting;

[0062] S6: By bringing the solidification time into the prediction model to predict the mechanical properties, it is possible to promptly discover the problem of unqualified mechanical properties of local parts of the casting, correct the design, and then enter S5 until the mechanical properties of all parts of the casting meet the requirements.

[0063] Step S1 specifically includes: designing stepped test plates with different wall thicknesses and arranging them horizontally on both sides of the runner, and using the cross runner to compensate for shrinkage of the test plates to ensure internal quality. Stepped test plates with different wall thicknesses are sampled at equal distances laterally to reduce the temperature difference in the length direction of the standard tensile test bar and ensure the correspondence between mechanical properties and solidification time. The size of the stepped test plate is 105mm×60mm×wall thickness (mm) to prevent thermal interference from affecting the accuracy of the data. Each test plate with different wall thickness is 30mm apart. The cross-sectional area of ​​the trapezoidal cross runner is 1718mm2, and the cross-sectional area of ​​the straight runner is 182mm2.

[0064] Cold iron arrangement see Figure 2 The design dimensions of the cold iron with 7mm wall thickness on one side are 120mm×25mm×12mm for the upper cold iron, 120mm×40mm×35mm for the lower cold iron, and 120mm×25mm×16mm for the side cold iron, and there is no cold iron on the other side; the design dimensions of the cold iron with 10mm wall thickness on one side are 120mm×26mm×16mm for the upper cold iron, and there is no cold iron on the other side; the design dimensions of the cold iron with 13mm wall thickness on one side are 120mm×15mm×16mm for the upper cold iron, and 120mm×40mm×8mm for the lower cold iron, and there is no cold iron on the other side; the design dimensions of the cold iron with 16mm wall thickness on one side are 120mm×15mm×16mm for the side cold iron, and the upper cold iron on the other side is 120mm×30mm×18mm, the lower cold iron is 120mm×30mm×30mm, and the side cold iron is 120mm×35mm×25mm.

[0065] Step S2 specifically includes: using the material calculation function of the Procast software to calculate the thermophysical property values ​​of the alloy to solve the problem of vacancies in the database of newly developed materials, and other simulation parameters are set according to the actual casting process of the alloy.

[0066] Step S3 specifically includes: making a wooden mold for the step sample, using the wooden mold to shape, filling resin sand on the surface of the mold, and when the uniform coverage thickness reaches 50-100 mm, tamping, continuing to add resin sand, tamping, until it is filled, and finally scraping flat. Melting aluminum water according to the smelting process of the alloy, pouring it into the sand mold of the step sample, cleaning, taking out the step sample, dissecting the step sample according to the sampling plan to prepare Φ6 tensile test bars and hardness blocks, performing tensile tests and hardness tests, and obtaining mechanical property values.

[0067] Step S4 specifically includes: processing the solidification time and mechanical property data by linear fitting, and requiring that the coefficient of variation of the obtained prediction model is greater than 0.9.

[0068] Changes in system free energy before and after embryo formation: where ΔG v is the volume free energy, ΔG s It is the surface free energy. During the formation of the embryo, the liquid-solid phase transition will reduce the volume free energy, and the newly formed phase boundary will increase the surface free energy.

[0069] The condition for nucleation is that the growth of the embryo reduces the free energy of the system. Only when the initial radius r of the embryo is greater than the critical nucleation radius, the growth of the embryo can reduce the free energy of the system; otherwise, the reduction of the embryo can reduce the free energy. It can be seen that the critical nucleation radius is affected by the degree of supercooling and the properties of the material itself. The higher the degree of supercooling, the smaller the critical nucleation radius. According to the solidification theory, only when the degree of supercooling is higher than the critical degree of supercooling, the radius of the embryo spontaneously formed in the liquid will be larger than the critical nucleation radius and the liquid will begin to solidify. Generally, the faster the cooling speed of the aluminum alloy, the shorter the solidification time, the greater the degree of supercooling, the higher the nucleation rate, and the finer the grains in the alloy structure.

[0070] According to the Hall-Page formula: The strength of the material is affected by the grain size. The smaller the grain size, the higher the strength of the material. Conversely, the coarser the grain, the lower the strength of the material. The relationship between grain size and toughness is: Where β, B, and C are constants, and Tc is the brittle transition temperature. The mechanical properties of the alloy are directly affected by the solidification time. The patented method uses this influence relationship and uses a linear fitting method to process the mechanical properties of alloys with different solidification times. The variation percentage coefficient of the prediction model is used for model screening, and the mechanical properties of different parts of aluminum alloy castings can be predicted.

[0071] Example 1: Prediction of mechanical properties of Al-9Si-2Cu-0.4Mg alloy castings, comprising the following steps:

[0072] S1: Design step specimens with different solidification times. According to the size of the tensile test bar and the sampling plan, the size of the test plate is designed to be 105mm×60mm. The wall thicknesses of four typical aluminum alloy products are selected as wall thickness variables, which are 7mm, 10mm, 13mm and 16mm respectively. Set upper, lower and side chillers of different thicknesses on the test plates with different wall thicknesses to create different cooling conditions and obtain different solidification times. According to the characteristics of aluminum alloy, design an open casting system, and arrange the test plates horizontally on both sides of the cross runner. There is no riser and the cross runner is used to feed the shrinkage. Draw a three-dimensional model of the step specimen in UG, and use Procast simulation to confirm that the process is reasonable and there are no defects inside the test plate.

[0073] S2: Import the step specimen model into the mesh pre-processing module of Procast, and divide the step specimen into three-dimensional meshes; set the simulation parameters in the cast module of Procast: Step 1, set the gravity direction. The step specimen is cast by gravity, and the gravity direction is set to -Y axis. Step 2, set the material parameters. Select mold as the material type of the step specimen sand mold, set the material to ResinBonded Sand, set the initial filling rate to 100%, and set the initial temperature to 20°C; select mold as the material type of the chilled iron, set the material to EN AC-46400AlSi9Cu1Mg, set the initial filling rate to 100%, and set the initial temperature to 20°C; select Alloy as the material type of the step specimen, select cast Al-9Si-2Cu-0.4Mg alloy, set the initial filling rate to 0%, and set the initial temperature to 730°C. Step 3, set the interface heat transfer coefficient. The interface heat transfer coefficient between the chilled iron and the step specimen is set to 1000W / (m 2 ·K); the interface heat transfer coefficient between the cold iron and the sand mold is set to 300W / (m 2 ·K); the interface heat transfer coefficient between the sand mold and the step sample is set to AlSi7Mg03-silicaSand. The fourth step is to set the cooling parameters. The cooling parameters are set to Air Cooling. The cooling surface selects the outer surface of the step sample sand mold. The gate and vent are also selected. The fifth step is to set the pouring parameters, select the gate position, set the pouring temperature to 730°C, and the pouring time to 5S. The sixth step is to set the solver. According to the step sample pouring method, select the Gravity Filling solver. Finally, after checking that the parameter settings are correct, perform the simulation;

[0074] In the Solidification Time function of THERMAL, obtain the solidification time data of the step specimen, select the slicing method to view the information, add the ZX section, select the solid information in the software display drop-down bar, and follow the sampling plan of the step specimen tensile test bar to view the solidification time at both ends and the center of the tensile test bar in turn. The average value of the three-point solidification time is used as the solidification time corresponding to the mechanical properties of the test bar. The solidification time is shown in Table 1.

[0075] Table 1 Solidification time of cast Al-9Si-2Cu-0.4Mg alloy step specimen

[0076]

[0077]

[0078] S3: Cast the step specimens, dissect the step specimens according to the plan, and conduct tensile tests and hardness tests;

[0079] The mechanical properties data of the cast Al-9Si-2Cu-0.4Mg alloy at different solidification times were obtained, as shown in Table 2.

[0080] Table 2 Mechanical properties of cast Al-9Si-2Cu-0.4Mg alloy step specimens at different solidification times

[0081]

[0082] S4: The data were processed by linear fitting to obtain the following mechanical property prediction model: T6 tensile strength = 414.2-0.4766 × solidification time, with a percentage coefficient of variation of 0.92;

[0083] T6 yield strength = 316.3-0.1989 × solidification time, percentage coefficient of variation 0.91;

[0084] T6 elongation = 7.36-0.02026 × setting time, percentage coefficient of variation 0.9;

[0085] T6 hardness = 137.2-0.1402×setting time, percentage coefficient of variation 0.94.

[0086] S5: Import the casting model into the pre-processing module of Procast software and divide the mesh;

[0087] Set the simulation parameters in the Procast cast module: Step 1, create a virtual sand mold. Step 2, set the gravity direction, and set the gravity direction to -Y axis. Step 3, set the material parameters, verify the casting sand mold material type, select mold, set the material to Resin Bonded Sand, the initial filling rate is 100%, and the initial temperature is set to 20°C; select mold for the chilled iron material type, set the material to EN AC-46400AlSi9Cu1Mg, the initial filling rate is 100%, and the initial temperature is set to 20°C; select Alloy for the casting material type, select cast Al-9Si-2Cu-0.4Mg alloy, the initial filling rate is 0%, and the initial temperature is set to 710°C. Step 4, set the interface heat transfer coefficient, and set the interface heat transfer coefficient between the chilled iron and the casting to 1000W / (m 2 ·K); the interface heat transfer coefficient between the cold iron and the sand mold is selected as 300W / (m 2 ·K); the interface heat transfer coefficient between the sand mold and the casting is set to AlSi7Mg03-silicaSand. The fifth step is to set the cooling parameters. The cooling parameters are set to Air Cooling. The cooling surface selects the outer surface of the casting sand mold, and the riser is selected. The sixth step is to set the pouring parameters, select the gate position, set the pouring temperature to 710℃, and the pouring time to 18S. The seventh step is to set the solver and select the LPDC Filling solver according to the casting pouring method. Finally, after checking that the parameter settings are correct, perform the simulation.

[0088] S6: Use Solidification Time in the THERMAL function to obtain the solidification time data of the casting, view the information in a slicing manner, add sections, and view the solidification time at both ends and the center of the selected tensile test bar processing position in turn. The average value of the three-point solidification time is used as the solidification time corresponding to the mechanical properties of the test bar. Bring the solidification time of the part to be predicted into the mechanical property prediction model, calculate the predicted value of the mechanical properties of the casting, and compare it with the requirements. If it does not meet the requirements, re-revise the design and return to S5 until all parts of the casting meet the requirements.

[0089] Example 2: Prediction of mechanical properties of Al-7Si-0.55Mg-0.15Ti alloy castings, comprising the following steps:

[0090] S1: Design step specimens with different solidification times. According to the size of the tensile test bar and the sampling plan, the size of the test plate is designed to be 105mm×60mm. The wall thicknesses of four typical aluminum alloy products are selected as wall thickness variables, which are 7mm, 10mm, 13mm and 16mm respectively. Set upper, lower and side chillers of different thicknesses on the test plates with different wall thicknesses to create different cooling conditions and obtain different solidification times. According to the characteristics of aluminum alloy, design an open casting system, and arrange the test plates horizontally on both sides of the cross runner. There is no riser and the cross runner is used to feed the shrinkage. Draw a three-dimensional model of the step specimen in UG, and use Procast simulation to confirm that the process is reasonable and there are no defects inside the test plate.

[0091] S2: Import the step specimen model into the mesh pre-processing module of Procast, and divide the step specimen into three-dimensional meshes; set the simulation parameters in the cast module of Procast: Step 1, set the gravity direction. The step specimen is cast by gravity, and the gravity direction is set to -Y axis. Step 2, set the material parameters. Select mold as the material type of the step specimen sand mold, set the material to ResinBonded Sand, set the initial filling rate to 100%, and set the initial temperature to 20°C; select mold as the material type of the chilled iron, set the material to EN AC-46400AlSi9Cu1Mg, set the initial filling rate to 100%, and set the initial temperature to 20°C; select Alloy as the material type of the step specimen, select cast Al-7Si-0.55Mg-0.15Ti alloy, set the initial filling rate to 0%, and set the initial temperature to 730°C. Step 3, set the interface heat transfer coefficient. The interface heat transfer coefficient between the chilled iron and the step specimen is set to 1000W / (m 2 ·K); the interface heat transfer coefficient between the cold iron and the sand mold is set to 300W / (m 2 ·K); the interface heat transfer coefficient between the sand mold and the step sample is set to AlSi7Mg03-silicaSand. The fourth step is to set the cooling parameters. The cooling parameters are set to Air Cooling. The cooling surface selects the outer surface of the step sample sand mold. The gate and vent are also selected. The fifth step is to set the pouring parameters, select the gate position, set the pouring temperature to 730°C, and the pouring time to 5S. The sixth step is to set the solver. According to the step sample pouring method, select the Gravity Filling solver. Finally, after checking that the parameter settings are correct, perform the simulation;

[0092] In the Solidification Time function of THERMAL, obtain the solidification time data of the step specimen, select the slicing method to view the information, add the ZX section, select the solid information in the software display drop-down bar, and follow the sampling plan of the step specimen tensile test bar to view the solidification time at both ends and the center of the tensile test bar in turn. The average value of the three-point solidification time is used as the solidification time corresponding to the mechanical properties of the test bar. The solidification time is shown in Table 3.

[0093] Table 3 Solidification time of cast Al-7Si-0.55Mg-0.15Ti alloy step sample

[0094]

[0095]

[0096] S3: Cast the step specimens in real form, dissect the step specimens according to the plan, and conduct tensile tests and hardness tests;

[0097] The mechanical properties data of the cast Al-7Si-0.55Mg-0.15Ti alloy at different solidification times were obtained, as shown in Table 4.

[0098] Table 4 Mechanical properties of cast Al-7Si-0.55Mg-0.15Ti alloy step specimens at different solidification times

[0099]

[0100]

[0101] S4: The data were processed by linear fitting to obtain the following mechanical property prediction model: T6 tensile strength = 387.6-0.42088×solidification time, percentage coefficient of variation 0.97;

[0102] T6 yield strength = 306-0.3072 × solidification time, percentage coefficient of variation 0.97;

[0103] T6 elongation = 8.202-0.01824 × setting time, percentage coefficient of variation 0.93;

[0104] T6 hardness = 123.3-0.2089×setting time, percentage coefficient of variation 0.95.

[0105] S5: Import the casting model into the pre-processing module of Procast software and divide the mesh;

[0106] Set the simulation parameters in the Procast cast module: Step 1, create a virtual sand mold. Step 2, set the gravity direction, and set the gravity direction to -Y axis. Step 3, set the material parameters, verify the casting sand mold material type, select mold, set the material to Resin Bonded Sand, the initial filling rate is 100%, and the initial temperature is set to 20°C; select mold for the chilled iron material type, set the material to EN AC-46400AlSi9Cu1Mg, the initial filling rate is 100%, and the initial temperature is set to 20°C; select Alloy for the casting material type, select cast Al-9Si-2Cu-0.4Mg alloy, the initial filling rate is 0%, and the initial temperature is set to 710°C. Step 4, set the interface heat transfer coefficient, and set the interface heat transfer coefficient between the chilled iron and the casting to 1000W / (m 2 ·K); the interface heat transfer coefficient between the cold iron and the sand mold is selected as 300W / (m 2 ·K); the interface heat transfer coefficient between the sand mold and the casting is set to AlSi7Mg03-silicaSand. The fifth step is to set the cooling parameters. The cooling parameters are set to Air Cooling. The cooling surface selects the outer surface of the casting sand mold, and the riser is selected. The sixth step is to set the pouring parameters, select the gate position, set the pouring temperature to 710℃, and the pouring time to 18S. The seventh step is to set the solver and select the LPDC Filling solver according to the casting pouring method. Finally, after checking that the parameter settings are correct, perform the simulation.

[0107] S6: Use Solidification Time in the THERMAL function to obtain the solidification time data of the casting, view the information in a slicing manner, add sections, and view the solidification time at both ends and the center of the selected tensile test bar processing position in turn. The average value of the three-point solidification time is used as the solidification time corresponding to the mechanical properties of the test bar. Bring the solidification time of the part to be predicted into the mechanical property prediction model, calculate the predicted value of the mechanical properties of the casting, and compare it with the requirements. If it does not meet the requirements, re-revise the design and return to S5 until all parts of the casting meet the requirements.

[0108] The method of the present invention can help designers predict the mechanical properties of castings, greatly improving the efficiency of aluminum alloy casting design and development, which is of great significance.

[0109] Those skilled in the art should understand that the specific structures and processes shown in the above specific embodiments are only exemplary and not restrictive. Moreover, those skilled in the art can combine the various technical features shown above in various possible ways to form new technical solutions, or make other changes, which are all within the scope of the present invention.

Claims

1. A method for predicting mechanical properties of different parts of aluminum alloy castings using solidification time, characterized in that: The following steps are involved: Step S1, designing step specimens with different solidification times by combining different wall thicknesses and chills, the sampling location must be free of defects, and the specimen size must be sufficient to produce a tensile test bar; Step S2, Procast simulation to obtain the solidification time of the step sample, and the average value of the solidification time at the middle and two ends of the tensile test rod is used as the solidification time corresponding to the mechanical properties of the alloy at the middle position; Step S3, casting a step sample to obtain mechanical properties of alloys with different solidification times, the mechanical properties including tensile strength, yield strength, elongation and hardness; Step S4: using a linear fitting method to process the mechanical property values ​​of aluminum alloys with different solidification times, and selecting a linearly related model with a coefficient of variation greater than 0.9 as a prediction model for the mechanical properties of different parts of the aluminum alloy casting; Step S5: Procast simulation to obtain the solidification time of different parts of the aluminum alloy casting; Step S6: Bring the solidification time into the prediction model to predict the mechanical properties of different parts of the casting.

2. The method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time according to claim 1, characterized in that: The step S1 comprises: S1.

1. Design the step specimen, and use the tensile test bar size and sampling plan as the design basis for the test plate size. The test bar size is used as the length of the test plate, and the number of samples taken for each test plate determines the width of the test plate. The typical wall thickness of aluminum alloy castings is selected as the wall thickness variable of the test plate. S1.

2. According to the characteristics of aluminum alloy, design an open pouring system, use chilled iron as the second variable, design step specimens with different solidification times, and draw the model in UG; S1.

3. Use Procast to simulate the process of the step specimen, and check the internal quality of the test plates with different wall thicknesses in the post-processing module to ensure that the process design is reasonable, the test plates are defect-free, and will not affect the mechanical properties.

3. The method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time according to claim 2, characterized in that: Step S1 includes: designing step test plates with different wall thicknesses and arranging them horizontally on both sides of the runner, and using the cross runner to compensate for shrinkage of the test plates to ensure internal quality; sampling the step test plates with different wall thicknesses at equal distances in the horizontal direction to reduce the temperature difference in the length direction of the standard tensile test rod and ensure the correspondence between the mechanical properties and the solidification time.

4. The method for predicting mechanical properties of different parts of aluminum alloy castings using solidification time according to claim 1, characterized in that: The step S2 comprises: S2.

1. Import the model into Procast and divide the step sample grid in the pre-processing module; S2.

2. Set the casting process parameters of the casting in the cast module of Procast; S2.

3. In the Procast post-processing module, select Solidification Time to view the solidification time data, select entity information view as the viewing method, use the slicing function, select the actual test rod sampling position, and obtain the solidification time data of the center and both ends of the test rod; S2.

4. The average value of the three-point solidification time is taken as the solidification time corresponding to the mechanical properties of the alloy at that position.

5. The method for predicting mechanical properties of different parts of aluminum alloy castings using solidification time according to claim 1, characterized in that: The step S3 comprises: S3.

1. Carry out the modeling of the step specimen and cast the step specimen according to the casting and pouring process of the alloy; S3.

2. Dissect the step specimens according to the sampling plan and prepare standard tensile test bars and hardness blocks; S3.

2. According to the test standards, obtain the mechanical properties of alloys with different solidification times.

6. The method for predicting mechanical properties of different parts of an aluminum alloy casting using solidification time according to claim 5, characterized in that: The step S3 comprises: making a wooden mold of a step specimen, using the wooden mold to shape, filling resin sand on the surface of the mold, and when the uniform coverage thickness reaches 50 to 100 mm, tamping, continuing to add resin sand, tamping, until it is filled, and finally scraping flat; smelting aluminum water according to the smelting process of the alloy, pouring it into the sand mold of the step specimen, cleaning, taking out the actual step specimen, dissecting the step specimen according to the sampling plan to prepare a Φ6 tensile test rod and a hardness block, performing a tensile test and a hardness test, and obtaining the mechanical property value.

7. The method for predicting mechanical properties of different parts of aluminum alloy castings using solidification time according to claim 1, characterized in that: The step S4 comprises: S4.

1. Use linear fitting to process the mechanical property data of alloys with different solidification times; S4.

2. Perform model screening and select models with a coefficient of variation percentage greater than 0.

9.

8. The method for predicting mechanical properties of different parts of aluminum alloy castings using solidification time according to claim 1, characterized in that: The step S5 comprises: S5.

1. Import the casting model into Procast and divide the mesh in the pre-processing module; S5.

2. Use the same casting simulation parameter setting scheme as the step specimen to set the casting simulation parameters of the casting; S5.

3. Perform a simulation of the casting.

9. The method for predicting mechanical properties of different parts of aluminum alloy castings using solidification time according to claim 1, characterized in that: The step S6 comprises: S6.

1. In the Procast post-processing module, select the part whose mechanical properties need to be predicted, use the entity information viewing function, and obtain the solidification time data of the casting in Solidification Time; S6.2, inputting the obtained solidification values ​​into a mechanical prediction model; S6.

3. Compare the predicted mechanical property values ​​with the required values ​​of the castings to promptly identify problems with unqualified mechanical properties in thick and large parts of the castings; S6.

4. If any non-conformity occurs, modify the design and return to S5 until the mechanical properties of different parts of the casting meet the requirements.

Images