CN110941889B - Research method for germination and expansion of microscopic and macroscopic cracks of continuous casting special-shaped blank - Google Patents
Research method for germination and expansion of microscopic and macroscopic cracks of continuous casting special-shaped blank Download PDFInfo
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Abstract
The invention discloses a research method for germination and expansion of microscopic and macroscopic cracks of a continuous casting special-shaped blank, which comprises the steps of simulating a temperature field and a stress field of the special-shaped blank in a crystallizer through ANSYS, so as to find out the position where the crack of the casting blank is most easy to initiate and expand; then adopting ABAQUS finite element software and an extended finite element method, combining a high-temperature fracture experiment, and simulating the extension behavior of the surface crack of the casting blank based on XFEM; and finally, calculating the stress and displacement of the crack tip unit by the last step, and simulating the initiation and expansion behaviors of crystal cracks under the microscopic condition by taking the stress and displacement as boundary conditions. The optimization proposal of the production process condition can be proposed to reduce the defects, especially the cracks, on the surface of the casting blank, and solve the problem that the surface cracks of the special-shaped blank are difficult to effectively solve in the current engineering.
Description
Technical Field
The invention relates to a method for researching germination and expansion of microscopic and macroscopic cracks of a continuous casting special-shaped blank, in particular to a method for researching germination and expansion of microscopic and macroscopic cracks of a continuous casting special-shaped blank.
Background
In the continuous casting process, various defects are inevitably generated, and the proportion of casting blank cracks in the various defects is up to about 50 percent. This problem is exacerbated by the complex profile shape of the parison. The production efficiency and the product quality are seriously affected by the generation of cracks of casting blanks. In order to improve the situation, a great deal of work is done by a plurality of scholars on the reason and control method of the formation of the surface cracks of the continuous casting billet, wherein the research on the influence of factors such as molten steel components, drawing speed, casting powder thickness, mold vibration and the like on the surface cracks of the continuous casting billet is included, and the progressive straightening technology is adopted for continuous casting process operation equipment, and measures such as whole process protection casting and the like are proposed to reduce the generation of the cracks.
However, the above studies have focused mainly on macroscopic qualitative analysis of production data and theoretical analysis, and have been conducted on the basis of conventional parison types. The crack initiation and expansion processes in the production process of the special-shaped blank are rarely researched, and the establishment of a thermodynamic coupling model based on the stress genetic characteristics of the continuous casting blank shell is hardly researched, and particularly the crack expansion simulation of a crystal model is very little.
Disclosure of Invention
The invention aims to provide a research method for microscopic and macroscopic crack germination and expansion of a continuous casting special-shaped blank, which is used for comprehensively planning the whole process of microscopic and macroscopic crack germination and expansion research of the continuous casting blank, analyzing interaction rules of microscopic and microscopic surface cracks of the casting blank from the high-science analysis and calculation of the whole system, and discussing a macroscopic process parameter optimization scheme on the basis, so that optimization suggestions on production process conditions can be provided to reduce defects, particularly cracks, of the surface of the casting blank, and the problem that the surface cracks of the special-shaped blank are difficult to effectively solve in the current engineering is solved.
In order to solve the technical problems, the invention adopts the following technical means:
the research method for germination and expansion of the microscopic and macroscopic cracks of the continuous casting billet comprises the following steps:
1) Based on stress inheritance characteristics of a continuous casting blank shell, the fact that stress fields in continuous casting are continuously inherited is considered, so that defects at the upper part can be reflected at the lower part is considered, a casting blank solidification thermal coupling model in the crystallizer is established by utilizing a multi-load step method, and under the condition that conicity and air gaps are considered, the positions of the temperature fields, the blank shell thickness, equivalent stress, maximum principal stress and wide-narrow surface stress at each position of the casting blank are calculated according to a temperature field and a stress field simulated by ANSYS, so that the position where cracks of the casting blank are most prone to initiation and expansion is found;
2) Performing macroscopic expansion research on the surface cracks of the special-shaped blank, testing the yield stress and fracture toughness of the material at high temperature by using GLEEBLE-3500, and performing initial crack expansion dynamic simulation by using large-scale finite element analysis software ABAQUS and an X-FEM method combined with the large-scale finite element analysis software ABAQUS based on the theory of fracture mechanics to simulate the expansion condition of the surface cracks at the special-shaped blank web plate and the R angle in the crystallizer;
3) And (3) simulating crack initiation and expansion in the special-shaped blank crystal, establishing a special-shaped blank polycrystalline model through MATLAB, performing stress strain analysis of the defect-free crystal, polycrystalline model analysis containing multiple cracks, polycrystalline model analysis containing different porosities and polycrystalline model analysis containing inclusions with different proportions in ABAQUS software based on microscopic damage mechanics by utilizing a completely implicit stress iterative algorithm, and performing crack expansion simulation of the polycrystalline model.
Compared with the prior art, the invention adopting the technical scheme has the outstanding characteristics that:
step 1) finding out the position where the crack of the casting blank is most easy to initiate and expand, and step 2) simulating the expansion condition of surface cracks at the position of a special-shaped blank web plate and the position of an R angle in a crystallizer, thereby providing a foundation for deep research on the surface crack expansion of the special-shaped blank; and 3) performing crack extension simulation of the polycrystalline model, and providing theoretical guidance for generation of macrocracks and process optimization.
According to the technical scheme, the temperature field and the stress field of the special-shaped blank in the crystallizer are simulated through ANSYS, so that the position where the crack of the casting blank is most easy to initiate and expand is found out; then adopting ABAQUS finite element software and an extended finite element method, combining a high-temperature fracture experiment, and simulating the extension behavior of the surface crack of the casting blank based on XFEM; and finally, calculating the stress and displacement of the crack tip unit by the last step, and simulating the initiation and expansion behaviors of crystal cracks under the microscopic condition by taking the stress and displacement as boundary conditions, thereby providing a theoretical basis for reducing cracks on the surface of a casting blank.
Compared with the prior art, the invention adopting the technical research scheme adopts the research methods of thermal coupling analysis in the special-shaped blank continuous casting crystallizer, special-shaped blank surface crack macroscopic expansion research and special-shaped blank crystal internal crack initiation and expansion simulation multi-objective optimized continuous casting blank microscopic and macroscopic crack initiation and expansion, thereby providing optimization suggestions for production process conditions so as to reduce casting blank surface defects, particularly surface crack problems, and solving the problem that the special-shaped blank surface crack is difficult to effectively analyze and control in the current engineering. The invention integrally analyzes the whole process of microscopic and macroscopic crack germination and expansion research of the continuous casting blank, calculates from the high science analysis of the whole system, analyzes the interaction rule of macroscopic and microscopic surface cracks of the casting blank, and discusses the macroscopic process parameter optimization scheme on the basis.
Drawings
FIG. 1 is a block diagram of the thermal coupling step of the present invention based on stress inheritance.
FIG. 2 is a frame diagram of a step of macroscopic propagation of cracks on the surface of a preform according to the present invention.
FIG. 3 is a block diagram of a simulation step of crack initiation and propagation in a shaped-body crystal according to the present invention.
Fig. 4 is a cloud of temperature distribution for the parison at different locations in the mold.
Fig. 5 is a temperature change curve of each characteristic point.
Fig. 6 is a graph showing the thickness of the shell at each position of the parison in the mold.
FIG. 7 is a cloud of equivalent stress distributions of the cast strand at 175mm, 350mm, 525mm and 700mm from the crystallizer meniscus.
Fig. 8 is a graph of the maximum principal stress cloud of the strand at various locations in the mold.
Fig. 9 is a graph showing the maximum principal stress change curve at each characteristic point.
FIG. 10 is a graph showing the stress variation of the broad surface of each feature point of the cast slab at different positions of the mold.
FIG. 11 is a graph showing the stress variation of the narrow surface of each feature point of the cast slab at different positions of the mold.
Fig. 12 is a sub-model and pre-crack map.
FIG. 13 is a graph of surface longitudinal crack propagation at the web.
Fig. 14 is a graph of crack propagation at 30 ° to the direction of draw at the web.
Fig. 15 is a graph of longitudinal cracks at the R angle.
Fig. 16 is a graph of crack propagation at an R angle of 30 ° to the direction of draw.
Fig. 17 is a schematic diagram of the creation of a polycrystalline model.
FIG. 18 is a load profile of a polycrystalline model in ABAQUS.
FIG. 19 is a stress distribution diagram of a defect-free polycrystalline model.
Fig. 20 is a graph of crack propagation at 15 ° to the load direction.
Fig. 21 is a graph of crack propagation at 90 ° to the load direction.
FIG. 22 is a stress distribution diagram of polycrystalline models of different porosities.
FIG. 23 is a plot of stress distribution for different inclusion ratio polycrystalline models.
Fig. 24 is a diagram of a 45 ° crack primitive polycrystalline model.
FIG. 25 is a PHILSM cloud of a 45℃crack polycrystalline model at a pull rate of 0.9 m/min.
FIG. 26 is a PHILSM cloud of a 45℃crack polycrystalline model at a pull rate of 1.2 m/min.
Fig. 27 is a phililsm cloud of 45 ° crack polycrystalline models at 15 ℃ superheat.
Fig. 28 is a phililsm cloud of 45 ° crack polycrystalline models with a degree of superheat of 45 ℃.
Detailed Description
The invention will be further illustrated with reference to the following examples.
The invention is further illustrated below in connection with examples which, however, do not constitute any limitation of the invention.
Example 1 method for studying the germination and propagation of microscopic and macroscopic cracks in a continuously cast parison, comprising the steps of: step 1) combining with figure 1, it can be known that the thermodynamic coupling analysis in the special-shaped blank continuous casting crystallizer is based on the stress genetic characteristics of a continuous casting blank shell, namely, the stress field in continuous casting is considered, so that the defect generated at the upper position of the crystallizer can be reflected at the lower position, meanwhile, the fact that the casting blank entity changes when the temperature and the ferrostatic pressure are loaded is considered, a multi-load method is utilized to establish a casting blank solidification thermodynamic coupling model in the crystallizer, and under the condition of taking the taper and the air gap into consideration, the positions of the temperature field, the thickness of the blank shell at each position of the casting blank, the equivalent stress, the maximum main stress and the wide-narrow surface stress are calculated according to the temperature field and the stress field simulated by ANSYS, so that the position of the casting blank crack is most easy to initiate and expand is found.
In fig. 4, (a) 175mm from the meniscus; (b) 350mm from the meniscus; (c) 525mm from the meniscus; (d) 700mm from the meniscus.
As can be seen from fig. 4 and 5, the temperature distribution clouds of the special-shaped blank at different positions in the crystallizer and the temperature change curves of the characteristic points are identical to the previous study. As can be seen from fig. 6, the shell thickness calculation for each position of the cast slab: and (3) changing the thickness of the blank shell in the crystallizer at each position of the special-shaped blank.
In fig. 7, (a) 175mm from the meniscus; (b) 350mm from the meniscus; (c) 525mm from the meniscus; (d) 700mm from the meniscus.
As can be seen from the calculation of equivalent stress, the casting blank has a cloud of equivalent stress distribution at 175mm, 350mm, 525mm and 700mm from the meniscus of the crystallizer. According to the equivalent stress change curve of each characteristic point, the equivalent stress at the web plate always shows a growing trend, and reaches the maximum value at the second half section of the crystallizer and is larger than the inner angle of the flange.
In fig. 8, (a) 175mm from the meniscus; (b) 350mm from the meniscus; (c) 525mm from the meniscus; (d) 700mm from the meniscus.
As can be seen from fig. 8 and 9, the surface crack of the casting blank easily starts and propagates in the middle of the mold, and the most easily occurring position is the web, and then the R angle.
As can be seen in conjunction with fig. 10 and 11, comparison of the two figures verifies the conclusion of the combined temperature field and maximum principal stress: the casting blank wide surface is easier to initiate surface longitudinal crack, especially in the middle part of a crystallizer; in combination with the temperature field, the most likely position is the web, and then the R angle.
Step 2) study on macroscopic expansion of the surface cracks of the special-shaped blank is combined with fig. 2, the study analysis on macroscopic expansion of the surface cracks of the special-shaped blank is based on the later study carried out in the step 1, the temperature value and stress value of the material at the position where the cracks are easy to generate in the step 1 are extracted, the GLEEBLE-3500 is used for testing the yield stress and fracture toughness of the material at the corresponding temperature in the previous step, the high-temperature thermal physical parameters of the material at the corresponding temperature are obtained, then based on critical fracture toughness criterion indexes in fracture mechanics, the stress value extracted in the step 1 is applied to the model of the prefabricated crack as loading force to carry out dynamic simulation of initial crack expansion, and the expansion conditions of the surface cracks at the positions of the special-shaped blank web and the R angle in the crystallizer are simulated.
FIG. 12 submodel and pre-crack, (a) submodel meshing; (b) pre-forming surface cracks.
As can be seen in connection with fig. 12, crack modeling: the matrix model is built through an ABAQUS sub-model module, and the sub-model technology not only can save the mechanical boundary conditions of the whole model, but also can ensure that the subsequent stress analysis is carried out on the basis without being influenced. As shown in fig. 12.
As can be seen from fig. 13, 14, 15 and 16, the crack propagation process at the web and the R angle at the crack initiation site was simulated by the extended finite element method.
Under the same material parameters and external force conditions, the surface longitudinal crack is easier to expand, and the expansion is also maximum; the surface transverse crack is least prone to be expanded, and the expansion amount is also minimum; the crack forming an angle of 30 degrees and an angle of 60 degrees with the direction of the drawn blank can deviate in the direction in the process of expanding, but mainly expands along the direction of the drawn blank, namely longitudinally expands; surface cracks with the same angle with the direction of drawing the blank, the expansion of the cracks at the web plate is obviously larger than that at the R angle, which indicates that the cracks are easier to appear at the web plate.
Step 3) simulation of crack initiation and propagation in the special-shaped blank crystal is combined with fig. 3, wherein the simulation of crack initiation and propagation in the special-shaped blank crystal is characterized in that a special-shaped blank polycrystal Voronoi diagram is established through MATLAB, then a polycrystal model with different forms is established in ABAQUS, an X-FEM method in ABAQUS is utilized, a completely implicit stress iterative algorithm is utilized based on progressive failure in mesoscopic damage mechanics as a criterion index, physical parameters of materials at the corresponding temperature in step 2 are utilized, stress and displacement values of crack tip units obtained through calculation in step 2 are extracted, the stress and strain analysis of defect-free crystals, a polycrystal model analysis with multiple cracks, a polycrystal model analysis with different porosities and a polycrystal model analysis with different proportions are applied to the polycrystal model, and theoretical guidance is provided for generation and process optimization of macroscopic cracks by taking the completely implicit stress iterative algorithm as boundary conditions to be applied to the polycrystal model.
As can be seen from fig. 17, the modeling of the polycrystal is mainly implemented by MATLAB software programming, and a Voronoi diagram is drawn by using a related program.
It can be seen from the graph of FIG. 18 how the load distribution of the polycrystalline model in ABAQUS is applied.
As can be seen from fig. 19, the polycrystalline model grain boundaries and the intra-grain stress strain distribution are different in this example, and the stress strain value at the grain boundaries is significantly larger than that in the grains.
As can be seen from fig. 20 and 21, the propagation direction of the crack in the crystal is substantially the same as that of the macrocrack, and the crack propagates in the direction perpendicular to the tensile stress, and the crack propagation amount in this direction is also the largest; the expansion amount of cracks at the grain boundary is obviously higher than that of cracks in the crystal; the crack is irrelevant to the angle formed by the tensile stress and the final expansion direction of the crack, and the influence on the crack expansion is mainly reflected on the time, sequence and final expansion displacement of the crack.
As can be seen from fig. 22, there is a certain regularity in the stress distribution of the air holes, and stress concentration exists at the end of the air holes perpendicular to the tensile stress direction; the deformation range of the polycrystalline model is enlarged due to the increase of the porosity; under different porosities, the pores are expanded and gathered in the direction perpendicular to the tensile stress, the holes are continuously polymerized and expanded due to the localization of strain, and crack cracking is started from the direction.
As can be seen from fig. 23, stress concentration at different inclusion rates occurs at the inclusions, and the occurrence of strain at the inclusions is minimal, resulting in crack propagation along the inclusion direction, resulting in material failure and fracture. The higher the inclusion rate, the more pronounced the concentration of inclusion stress, and the greater the deformation of the matrix surrounding the inclusion.
It is known from fig. 22 and 23 that both the inclusions and the pores have some influence on crack initiation and propagation, but the pores have a larger influence on crack initiation and propagation than the inclusions.
As can be seen from fig. 24, 25 and 26, an increase in pull rate and an increase in phililsm value indicate a gradual increase in crack surface, and it is explained that an increase in pull rate is beneficial to crack propagation. This is in contrast to the increase in the pull rate, in which the surface temperature of the cast strand at the same point in the mold increases, so that the corresponding casting strand material parameters deteriorate, and the crack is easily broken.
As can be seen from fig. 24, 27 and 28, the degree of superheat increases, and the crack propagation displacement function phililsm gradually increases, which means that the degree of superheat increases, which is beneficial to crack propagation.
As can be seen from fig. 25, 26, 27, and 28, the increase in the philism value due to the increase in the pull rate is greater than the increase in the philism due to the increase in the superheat degree; the increase of the pulling speed is more beneficial to the crack growth of the casting blank relative to the increase of the superheat degree.
Through macroscopic and microscopic crack simulation, the porosity of the inclusions in the casting blank is increased, the crack is promoted to be expanded, and the expansion of pores to the cracks is higher than that of the inclusions; the increase of the drawing speed and the superheat degree is also beneficial to the crack growth of the casting blank, and the increase of the drawing speed is more beneficial to the crack growth of the casting blank.
The embodiment relies on experimental simulation analysis and expert knowledge, and is closely connected with production practice, so that a theoretical basis is provided for researching the germination and expansion of microscopic and macroscopic cracks of the continuous casting billet.
Simulating a temperature field and a stress field of the special-shaped blank in the crystallizer through ANSYS, so as to find out the position where the crack of the casting blank is most easy to initiate and expand; then adopting ABAQUS finite element software and an extended finite element method, combining a high-temperature fracture experiment, and simulating the extension behavior of the surface crack of the casting blank based on XFEM; and finally, calculating the stress and displacement of the crack tip unit by the last step, and simulating the initiation and expansion behaviors of crystal cracks under the microscopic condition by taking the stress and displacement as boundary conditions, so that a theoretical basis is provided for reducing cracks on the surface of a casting blank, and the method is accurate, reliable, practical and convenient.
Those skilled in the art can implement the present invention in many modifications without departing from the spirit and scope of the present invention, and the present invention is not limited to the preferred embodiments of the present invention, but includes all equivalent modifications within the scope of the appended claims.
Claims (1)
1. A research method for germination and expansion of microscopic and macroscopic cracks of a continuous casting special-shaped blank comprises the following steps: the method comprises the steps of 1) carrying out thermal coupling analysis in a special-shaped blank continuous casting crystallizer based on stress inheritance of a continuous casting blank shell, considering stress field continuous inheritance in continuous casting, enabling defects generated at the upper position of the crystallizer to be reflected at the lower position, simultaneously taking the fact that casting blank entity changes when loading temperature and ferrostatic pressure are taken into consideration, establishing a casting blank solidification thermal coupling model in the crystallizer by utilizing a multi-load method, and calculating blank shell thickness, equivalent stress, maximum principal stress and wide-narrow surface stress at each position of the temperature field and the casting blank according to a temperature field and a stress field simulated by ANSYS under the condition that conicity and air gap are considered, so as to find out the position where the casting blank crack is most easy to initiate and expand;
the temperature distribution clouds of the special-shaped blank at different positions in the crystallizer are matched with the temperature change curves of all characteristic points, and the calculation result of the temperature field is identical with the previous study;
calculating the thickness of the shell at each position of the casting blank: the thickness of the blank shell of each position of the special-shaped blank in the crystallizer is changed;
according to the equivalent stress change curve of each characteristic point, the equivalent stress at the web plate always shows a growing trend, and reaches the maximum value at the second half section of the crystallizer and is larger than the inner angle of the flange;
the surface crack of the casting blank is easy to initiate and expand in the middle part of the crystallizer, the most easy position is a web plate, and then the R angle is formed;
the conclusion of combining the temperature field and the maximum principal stress is: the casting blank wide surface is easier to initiate surface longitudinal crack, including the middle part of the crystallizer; combining the temperature field, wherein the most easily-appearing position is a web plate position, and then an R angle is formed;
step 2) analyzing the macroscopic expansion of the surface cracks of the special-shaped blank, wherein the macroscopic expansion analysis of the surface cracks of the special-shaped blank is based on the later study carried out in the step 1, extracting the temperature value and stress value of the material at the position where the cracks are easy to generate in the step 1, carrying out yield stress and fracture toughness test on the material at the corresponding temperature in the previous step by using GLEEBLE-3500, obtaining the thermal physical parameters of the material at the corresponding temperature, then applying the stress value extracted in the step 1 to the model of the pre-shaped blank as the loading force to carry out the dynamic simulation of the initial crack expansion by using the X-FEM method of ABAQUS and the combination of ABAQUS, and simulating the expansion condition of the surface cracks at the positions of the special-shaped blank web and the R angle in the crystallizer;
crack modeling: the matrix model is established through an ABAQUS sub-model module, so that the sub-model technology not only can save the mechanical boundary conditions of the whole model, but also can ensure that the subsequent stress analysis is carried out on the basis without being influenced;
simulating crack propagation processes at the web and the R angle of the crack-prone position by using an extended finite element method;
under the same material parameters and external force conditions, the surface longitudinal crack is easier to expand, and the expansion is also maximum; the surface transverse crack is least prone to be expanded, and the expansion amount is also minimum; the crack forming an angle of 30 degrees and an angle of 60 degrees with the direction of the drawn blank can deviate in the direction in the process of expanding, but mainly expands along the direction of the drawn blank, namely longitudinally expands; the surface cracks with the same angle with the direction of drawing the blank, the expansion of the cracks at the web plate is obviously larger than that at the R angle, which indicates that the cracks are easier to appear at the web plate;
step 3) simulation of crack initiation and propagation in the special-shaped blank crystal, namely establishing a special-shaped blank polycrystal Voronoi diagram through MATLAB, then introducing the special-shaped blank polycrystal Voronoi diagram into ABAQUS to establish different types of polycrystal models, performing crack propagation simulation of the polycrystal models by using an X-FEM method in the ABAQUS based on progressive failure in microscopic damage mechanics as a criterion index, using a completely implicit stress iterative algorithm, using physical parameters of the material at the temperature corresponding to the step 2, extracting stress and displacement values of the crack tip unit calculated in the step 2, applying the stress and displacement values as boundary conditions on the polycrystal models, performing stress strain analysis of defect-free crystals, polycrystal model analysis containing a plurality of cracks, polycrystal model analysis containing different porosities and polycrystal model analysis containing different proportions of inclusions in the ABAQUS software, and providing theoretical guidance for generation and process optimization of macroscopic cracks;
the establishment of the polycrystal model is mainly realized by MATLAB software programming, and a Voronoi diagram is drawn by using a related program;
the grain boundary of the polycrystalline model is different from the stress strain distribution in the crystal, and the stress strain value at the grain boundary is obviously larger than that in the crystal;
the propagation direction of the crack in the crystal is basically the same as that of the macrocrack, the crack propagates towards the direction perpendicular to the tensile stress, and the crack propagation amount in the direction is also the largest; the expansion amount of cracks at the grain boundary is obviously higher than that of cracks in the crystal; the angle of the crack is irrelevant to the tensile stress and the final expansion direction of the crack, and the influence of the crack on crack expansion is mainly reflected on the time, sequence and final expansion displacement of the crack;
the stress distribution of the air holes has certain regularity, and the end parts of the air holes perpendicular to the tensile stress direction have stress concentration; the deformation range of the polycrystalline model is enlarged due to the increase of the porosity; under different porosities, the pores are expanded and gathered in the direction perpendicular to the tensile stress, the holes are continuously polymerized and expanded due to the localization of strain, and crack cracking is often started from the direction;
stress concentration phenomena under different inclusion rates all occur at the inclusion positions, and the occurrence of strain at the inclusion positions is minimum, so that cracks can be expanded along the inclusion direction, and the materials are damaged and broken; the higher the inclusion rate, the more obvious the concentration of inclusion stress, and the larger the deformation of the matrix around the inclusion;
the inclusion and the air hole have certain influence on crack initiation and expansion, but the influence of the air hole on crack initiation and expansion is larger than that of the inclusion;
increasing the pulling speed, increasing the PHILSM value, indicating that the crack surface is gradually increased, and indicating that the increasing of the pulling speed is beneficial to crack growth; the temperature of the surface of the casting blank at the same position of the crystallizer is increased as the pulling speed is increased, so that the corresponding casting blank material parameters are deteriorated, and cracks are easy to crack;
the degree of superheat is increased, and the PHILSM value of the crack propagation displacement function is also gradually increased, which indicates that the degree of superheat is increased, thereby being beneficial to crack propagation;
the increase of PHILSM value caused by the increase of the pull rate is larger than that caused by the increase of the superheat degree; the increase of the pulling speed is more beneficial to the crack growth of the casting blank relative to the increase of the superheat degree;
through macroscopic and microscopic crack simulation, the porosity of the inclusion in the casting blank is increased, the crack is promoted to be expanded, and the pore pair crack is higher than the inclusion; the increase of the drawing speed and the superheat degree is also beneficial to the crack growth of the casting blank, and the increase of the drawing speed is more beneficial to the crack growth of the casting blank.
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