A method for solving solidification characteristic parameters in semi-continuous casting process

Abstract

The present invention belongs to the technical field of metal semi-continuous casting, and specifically relates to a method for solving solidification characteristic parameters of a semi-continuous casting process. The method for solving solidification characteristic parameters of a semi-continuous casting process provided by the present invention first establishes a three-dimensional geometric model based on the casting equipment and the shape of the ingot, and then solves the flow field and temperature field of the semi-continuous casting process based on the thermal-fluid coupling numerical simulation; then after the casting enters a steady state, the cooling curve is solved based on the streamline or trace, and then the cooling curve, streamline or trace are combined to solve a variety of solidification characteristic parameters of the semi-continuous casting process. When calculating the cooling curve, the present invention fully considers the internal flow of the slurry zone in the semi-continuous casting process, and the obtained cooling curve is more accurate than the existing methods in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of metal semi-continuous casting, and in particular relates to a method for solving solidification characteristic parameters in a semi-continuous casting process. Background Art

[0002] Semi-continuous casting of aluminum alloy is the most important process in aluminum processing. The quality of aluminum alloy in the ingot largely determines the subsequent processing and the final service performance of the product. The cooling curve is a curve with time (t) as the horizontal axis and temperature (T) as the vertical axis, which records the solidification history of each point in the ingot, such as Figure 1 The cooling history or cooling curve of each point in the ingot during the solidification process is an important carrier for studying the solidification behavior of metals.

[0003] Multiple solidification characteristic parameters can be analyzed through the cooling curve, such as the further calculation of the solidification solid fraction curve (the horizontal axis is time (t), the vertical axis is solid fraction (fs)), solidification time, cooling rate, thermal cracking sensitivity, etc. These solidification characteristics are closely related to the ingot porosity, macrosegregation, grain size and second phase precipitation. Obtaining an accurate ingot cooling curve is the key to understanding and studying the formation mechanism of ingot defects and evaluating ingot defects.

[0004] According to the flow characteristics of aluminum alloy during solidification, there are several key temperature points: liquidus T L , and the dendrite lap temperature T COH and solidus T S According to the above key points, the solidification process can be divided into liquid phase ( T > T L )、Two-phase region( T L ≥ T ≥ T S ) and the solid phase ( T < T S ). According to the fluidity, the two phases can be divided into slurry zone ( T L ≥T > T COH ) and the mushy zone ( T COH ≥T≥ T L ),like Figure 2As shown in the figure, the primary aluminum in the slurry zone begins to nucleate and grow, but there is no overlap between the primary aluminum, and it can flow with the melt. When the temperature is lower than the overlap temperature, the primary aluminum overlaps each other to form a dendrite network, which cannot flow, and the remaining liquid phase flows between the dendrites.

[0005] At present, there are two methods to obtain the cooling curve of ingot casting: ① By pre-embedding thermocouples in the casting mold, after the molten metal is poured into the mold, the thermocouple records the temperature history data of the position point as the solidification process proceeds, and the thermocouple solidifies inside the ingot (reference: Anyalebechi, PN, Rouns, TN, Sanders, RE (2016). Effects of Cooling Rate and Grain Refining on Constituent Phase Particle Size in As-Cast 3004 Alloy. In: Grandfield, JF, Eskin, DG (eds) Essential Readings in Light Metals. Springer, Cham. https: / / doi.org / 10.1007 / 978-3-319-48228-6_60). However, this method will cause the cast product to be scrapped. ② Calculate the temperature field of the casting process through numerical simulation, extract temperature history data, and process these data (slope or secant slope) to obtain the cooling curve (Reference: Wu Yongfu, Zhang Baocun, Wang Ning, et al. Effect of cooling rate on eutectic silicon modification during DC semi-continuous casting of 4032 aluminum alloy round ingot [J]. Journal of Aeronautical Materials, 2021, 41(02): 53-60.). However, these methods do not take into account the flow of the solid phase with the melt in the slurry zone (above the overlap temperature TCOH), which is inconsistent with the actual situation, resulting in inaccurate calculation of the cooling curve, which may be misleading when studying solidification problems or guiding production. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for solving the solidification characteristic parameters of a semi-continuous casting process. Through a data processing method based on thermal-flux coupling numerical simulation, the internal flow of the slurry zone is fully considered to accurately calculate the cooling curve of the semi-continuous casting process. Then, the cooling curve, streamlines and traces are combined to solve multiple solidification characteristic parameters of the semi-continuous casting process.

[0007] The present invention specifically includes the following contents:

[0008] A method for solving solidification characteristic parameters in a semi-continuous casting process comprises the following steps:

[0009] S1, solving the flow field and temperature field: a three-dimensional geometric model is established according to the casting equipment and the ingot shape, and a thermal-fluid coupling numerical simulation is performed on the semi-continuous casting process to solve the flow field and temperature field of the semi-continuous casting process;

[0010] S2, solving the cooling curve: after the casting enters the steady state, the streamline or trace of the solidification process is extracted with the point of the solidified area on the cross section of the ingot as the end point, and the node coordinates, temperature T and time t on the streamline or trace are derived, and the time t and temperature T on the streamline or trace are taken to solve the cooling curve; repeat the above operation to obtain the cooling curve of any point on the cross section of the entire ingot;

[0011] S3, cooling curve data analysis: performing data analysis on the cooling curve of a certain point to obtain solidification characteristic parameters of the point, wherein the solidification characteristic parameters include solidification time, cooling rate, thermal crack sensitivity, etc.

[0012] The streamline refers to a curve that describes the direction and speed of the fluid (molten metal) at a certain moment. The trace refers to the movement trajectory of a fluid particle (which can be understood as a small unit in the molten metal during the alloy ingot casting process) over a continuous period of time. The method disclosed in the present invention includes two schemes: using streamlines to solve the solidification characteristic parameters of the semi-continuous casting process and using traces to solve the solidification characteristic parameters of the semi-continuous casting process. The use of streamlines or traces to solve are both within the protection scope of the present invention.

[0013] Furthermore, the step S3 also includes: analyzing enough cooling curves obtained to obtain the distribution of solidification characteristic parameters on the entire ingot cross section.

[0014] Furthermore, the solidification characteristic parameters include solidification time, which refers to the time from the liquidus temperature T L To solidus temperature T S The time elapsed, the solution method of the solidification time is:

[0015]

[0016] in,

[0017] t L-S Indicates the setting time;

[0018] t L Indicates that the temperature on a cooling curve reaches the liquidus temperature T L time;

[0019] t S Indicates that the temperature on the cooling curve reaches the solidus temperature T S time.

[0020] Furthermore, the solidification characteristic parameter includes an instantaneous cooling rate, and the method for calculating the instantaneous cooling rate is:

[0021]

[0022] in,

[0023] represents the instantaneous cooling rate of the i-th node on a cooling curve;

[0024] represents the temperature of the i-th node on the cooling curve;

[0025] represents the temperature of the i+1th node on the cooling curve;

[0026] represents the time corresponding to the i-th node on the cooling curve;

[0027] Indicates the time corresponding to the i+1th node on the cooling curve.

[0028] Furthermore, the solidification characteristic parameter includes a cooling rate in a certain cooling temperature range, and the method for calculating the cooling rate includes:

[0029] Determine the upper temperature limit and the lower temperature limit of the cooling temperature range;

[0030] Obtain the time corresponding to the upper temperature limit and the lower temperature limit on a cooling curve;

[0031] The cooling rate is then calculated as follows:

[0032]

[0033] in,

[0034] represents the cooling rate in the cooling temperature range;

[0035] T up Indicates the upper temperature limit of the cooling temperature range;

[0036] T down Indicates the temperature bottom line of the cooling temperature range;

[0037] t up Indicates the time corresponding to the upper temperature limit on the cooling curve;

[0038] t downIt indicates the time when the temperature bottom line corresponds to on the cooling curve.

[0039] Furthermore, the coordinates of the end point of the cooling curve are assigned to the calculated cooling rate , that is, the cooling rate of a point on the cross section of the ingot.

[0040] Furthermore, the cooling rates are calculated for all points on the ingot cross section to obtain the cooling rate distribution of the ingot cross section.

[0041] Further, when studying the high temperature phase that precipitates preferentially in the alloy, the T up The value is equal to the precipitation temperature of the high temperature phase, T down The value is higher than the temperature corresponding to the solidus line of the alloy; the high temperature phase refers to the alloy composition whose nucleation is above the liquidus line.

[0042] Further, when studying the cooling rate of primary aluminum grains in the liquid cavity, the T up The value is equal to the liquidus temperature , T down The value is equal to the solidus temperature The liquid cavity refers to a region of molten metal that has not yet completely solidified and is formed inside the alloy ingot due to the uneven cooling conditions during the solidification process of the alloy ingot.

[0043] Further, when studying the cooling rate after overlapping, the The value is equal to the dendrite lap temperature , T down The value is equal to the solidus temperature .

[0044] Furthermore, the solidification characteristic parameters include thermal cracking sensitivity, and the method for calculating the thermal cracking sensitivity is:

[0045]

[0046] in,

[0047] HCS It represents the thermal cracking sensitivity, which refers to the ratio of the duration of the late solidification brittle period to the duration of the stress relief period.

[0048] t V Indicates the duration of the stress relief period;

[0049] t R Indicates the duration of the weak period after solidification;

[0050] Indicates the time when the solid phase rate reaches 99%;

[0051] Indicates the time when the solid phase rate reaches 90%;

[0052] Indicates the time when the solid fraction reaches 40%.

[0053] Beneficial effects of the present invention:

[0054] The method for solving the solidification characteristic parameters of the semi-continuous casting process provided by the present invention first establishes a three-dimensional geometric model according to the casting equipment and the ingot shape, and then solves the flow field and temperature field of the semi-continuous casting process based on the thermal flow coupling numerical simulation; then after the casting enters the steady state, the cooling curve is solved according to the streamline or trace, and then the cooling curve, streamline or trace are combined to solve and obtain a variety of solidification characteristic parameters of the semi-continuous casting process. The present invention fully considers the internal flow of the slurry zone in the semi-continuous casting process when calculating the cooling curve, and the obtained cooling curve is more accurate than the existing methods in the prior art.

[0055] The method for solving the solidification characteristic parameters of the semi-continuous casting process disclosed in the present invention has wide applicability and can be used not only for the semi-continuous casting of aluminum alloys, but also for different casting processes of other metal materials, such as the continuous casting of steel, the semi-continuous casting and horizontal continuous casting of copper alloys, and the sand core casting, metal mold casting, high pressure casting, low pressure casting and other casting forming processes of cast iron, aluminum alloys, magnesium alloys, copper alloys, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a schematic diagram of cooling curve;

[0057] Figure 2 This is a comparison diagram of the area division and cooling paths of the semi-continuous casting process;

[0058] Figure 3 It is a schematic diagram of the ingot flow line and cooling curve;

[0059] Figure 4 This is a center streamline diagram of a 7050 aluminum alloy ingot with a diameter of 400 mm in an embodiment of the present invention;

[0060] Figure 5 It is a comparison diagram of cooling curves of 7050 aluminum alloy with a diameter of 400 mm in the embodiment of the present invention and the comparative example;

[0061] Figure 6 This is a comparison chart of the instantaneous cooling rate of 7050 aluminum alloy with a diameter of 400 mm in the embodiment of the present invention and the comparative example;

[0062] Figure 7 It is a streamline diagram of a 5083 alloy flat ingot with a specification of 420×1620 mm in an embodiment of the present invention;

[0063] Figure 8 It is a comparison chart of the cooling rates in the thickness direction of the 5083 alloy slab with a specification of 420×1620 mm in the embodiment of the present invention and the comparative example. DETAILED DESCRIPTION

[0064] A method for solving solidification characteristic parameters in a semi-continuous casting process comprises the following steps:

[0065] S1, solving the flow field and temperature field: a three-dimensional geometric model is established according to the casting equipment and the ingot shape, and a thermal-fluid coupling numerical simulation is performed on the semi-continuous casting process to solve the flow field and temperature field of the semi-continuous casting process;

[0066] S2, solving the cooling curve: after the casting enters the steady state, the streamline or trace of the solidification process is extracted with the point of the solidified area on the cross section of the ingot as the end point, and the node coordinates, temperature T and time t on the streamline or trace are derived, and the time t and temperature T on the streamline or trace are taken to solve the cooling curve; repeat the above operation to obtain the cooling curve of any point on the cross section of the entire ingot;

[0067] S3, cooling curve data analysis: perform data analysis on the cooling curve of a certain point to obtain the solidification characteristic parameters of the point, and analyze enough cooling curves to obtain the distribution of the solidification characteristic parameters on the entire ingot cross section.

[0068] The solidification characteristic parameters of the present invention include solidification time, cooling rate, thermal cracking sensitivity, etc., wherein:

[0069] (1) Solidification time refers to the time from the liquidus temperature T during the solidification process. L To solidus temperature T S The time elapsed, the solution for the solidification time is:

[0070] (1)

[0071] in,

[0072] t L-S Indicates the setting time;

[0073] t L Indicates the time when the temperature on a cooling curve reaches the liquidus temperature TL;

[0074] t S It represents the time when the temperature on the cooling curve reaches the solidus temperature TS.

[0075] (2) The solution method for the instantaneous cooling rate is:

[0076] (2)

[0077] in,

[0078] represents the instantaneous cooling rate of the i-th node on a cooling curve;

[0079] represents the temperature of the i-th node on the cooling curve;

[0080] represents the temperature of the i+1th node on the cooling curve;

[0081] represents the streamline time corresponding to the i-th node on the cooling curve;

[0082] Indicates the streamline time corresponding to the i+1th node on the cooling curve.

[0083] (3) The methods for calculating the cooling rate in a certain cooling temperature range include:

[0084] Determine the upper temperature limit and the lower temperature limit of the cooling temperature range;

[0085] Obtain the time corresponding to the upper temperature limit and the lower temperature limit on a cooling curve;

[0086] The cooling rate is then calculated as follows:

[0087] (3)

[0088] in,

[0089] represents the cooling rate in the cooling temperature range;

[0090] T up Indicates the upper temperature limit of the cooling temperature range;

[0091] T down Indicates the temperature bottom line of the cooling temperature range;

[0092] t up Indicates the time corresponding to the upper temperature limit on the cooling curve;

[0093] t down It indicates the time when the temperature bottom line corresponds to on the cooling curve.

[0094] Assign the coordinates of the end point of the streamline to the calculated cooling rate , the cooling rate of a point on the ingot cross section can be obtained.

[0095] The cooling rate is calculated for all points on the ingot cross section to obtain the cooling rate distribution of the ingot cross section.

[0096] When studying the high-temperature phase that precipitates preferentially in an alloy: T up The value is equal to the precipitation temperature of the high temperature phase, T down The value is higher than the temperature corresponding to the solidus line of the alloy; the high temperature phase refers to the alloy composition whose nucleation is above the liquidus line.

[0097] When studying the cooling rate of primary aluminum grains in liquid pockets: T up The value is equal to the liquidus temperature , T down The value is equal to the solidus temperature .

[0098] When studying the cooling rate after lap joint: The value is equal to the dendrite lap temperature , T down The value is equal to the solidus temperature .

[0099] (4) The solution method for thermal cracking sensitivity is:

[0100] (4)

[0101] in,

[0102] HCSrepresents hot tearing sensitivity, which refers to the ratio of the duration of the brittle period in the late solidification period to the duration of the stress relief period (reference: Nallathambi, AK, Penumakala, PK, Specht, E. (2013). Review of Hot Tearing Studies in Al Alloys during Direct Chill Casting. In: Krane, MJM, Jardy, A., Williamson, RL, Beaman, JJ (eds) Proceedings ofthe 2013 International Symposium on Liquid Metal Processing & Casting. Springer, Cham. https: / / doi.org / 10.1007 / 978-3-319-48102-9_40),

[0103] t V Indicates the duration of the stress relief period;

[0104] t R Indicates the duration of the weak period after solidification;

[0105] Indicates the time when the solid phase rate reaches 99%;

[0106] Indicates the time when the solid phase rate reaches 90%;

[0107] Indicates the time when the solid fraction reaches 40%.

[0108] The following is combined with Figure 1-8 The present invention is described in detail with specific embodiments, wherein Figure 1 It is a schematic diagram of cooling curve; Figure 2 This is a comparison diagram of the area division and cooling paths of the semi-continuous casting process; Figure 3 It is a schematic diagram of the ingot flow line and cooling curve; Figure 4 This is a center streamline diagram of a 7050 aluminum alloy ingot with a diameter of 400 mm in an embodiment of the present invention; Figure 5 It is a comparison diagram of cooling curves of 7050 aluminum alloy with a diameter of 400 mm in the embodiment of the present invention and the comparative example; Figure 6 This is a comparison chart of the instantaneous cooling rate of 7050 aluminum alloy with a diameter of 400 mm in the embodiment of the present invention and the comparative example; Figure 7It is a streamline diagram of a 5083 alloy flat ingot with a specification of 420×1620 mm in an embodiment of the present invention; Figure 8 The following is a comparison of the cooling rates of the 5083 alloy slab in the thickness direction of the embodiment of the present invention and the comparative example with a specification of 420×1620 mm. The following embodiment does not limit the invention described in the claims in any way. In addition, the entire contents of the configurations shown in the following embodiment are not limited to the solutions required by the invention described in the claims. Example 1

[0109] The casting temperature of 7050 alloy is about 700℃. During the semi-continuous casting process, Al3Zr phase will precipitate at a temperature higher than the alloy liquidus temperature. The cooling rate has a certain influence on the precipitation of Al3Zr phase. Therefore, to study the precipitation behavior of Al3Zr phase, it is necessary to solve the cooling rate during the solidification process.

[0110] This embodiment uses the method disclosed in the present invention to solve the cooling rate of the core of a 7050 aluminum alloy round ingot with a diameter of 400 mm, including the following steps:

[0111] S1, solving the flow field and temperature field: establishing a simulation model of the aluminum alloy casting process, calculating the temperature field and flow field from the start of the car to 2000s of casting, at which time the ingot has reached a steady state;

[0112] S2, solve the cooling curve: take the bottom of the ingot as the end point, extract the streamline, and output the nodes on the streamline. The streamline is as follows Figure 4 The temperature and flow time on the flow line are extracted and processed to obtain the temperature-time curve during the cooling process, as shown in Figure 5 shown.

[0113] S3, solve the cooling rate: Use formula (2) to solve the cooling rate at adjacent points on the convection line. The result is as follows: Figure 6 shown.

[0114] from Figure 6 It can be obtained that in the precipitation temperature range of 630~700℃ of Al3Zr phase, the maximum cooling rate can reach 10℃ / s. Example 2

[0115] The cooling rate distribution of the ingot has a significant effect on the microstructure distribution of the ingot. The cooling rate at the edge of the ingot is fast, the grains are fine, and the cooling rate at the core is slow, the grains are coarse.

[0116] This embodiment adopts the method of the present invention to analyze the cooling rate of the 420×1620mm flat ingot 5083 in the thickness direction of the ingot, and the casting temperature is 700°C and the casting speed is 50mm / min. The following steps are included:

[0117] S1, solving the flow field and temperature field: establishing a steady-state simulation model of the aluminum alloy casting process, and extracting data on the temperature field and flow field after the calculation converges;

[0118] S2, extract streamlines: draw a straight line from the center of the width direction of the ingot bottom, set 10 points on the straight line, and draw a streamline diagram backward from these 10 points, such as Figure 7 shown.

[0119] S3, this embodiment adopts the interval average cooling rate calculation method, the interval temperature is the liquidus line (=639℃) to the solidus line (=450℃) of the alloy, for each streamline, and Perform the difference to obtain the corresponding streamline time and , the cooling rate of each streamline is calculated according to formula (3).

[0120] The cooling rate in the thickness direction of the ingot obtained in this embodiment is as follows: Figure 8 As shown. Due to the presence of the diverter bag of the flat ingot, the melt flows out of the diverter bag outlet, flows to the small surface of the ingot, and then stays in the lower part of the liquid cavity and returns to the center of the ingot. That is, the primary phase undergoes a long period of movement inside the liquid cavity after nucleation, so the cooling rate is slow. The cooling rate at the center of the ingot is about 0.166℃ / s.

[0121] Comparative Example 1

[0122] This comparative example solves the cooling rate of the core of a 7050 aluminum alloy round ingot with a diameter of 400 mm according to a traditional method, comprising the following steps:

[0123] S1, solving the flow field and temperature field: establishing a simulation model of the aluminum alloy casting process, calculating the temperature field and flow field from the start of the car to 2000s of casting, at which time the inside of the ingot has reached a steady state, this step is the same as Example 1;

[0124] S2, extract the temperature-time curve at the center of the ingot, such as Figure 5 As shown;

[0125] S3, find the tangent line of the temperature-time curve and obtain the cooling rate, such as Figure 6 shown.

[0126] In this comparative example, the cooling rate is less than 1°C / s at 630°C-700°C. The initially formed Al3Zr phase will flow in the melt along the flow field, and the flow velocity of the melt is significantly greater than the casting velocity, so the Al3Zr phase can quickly deposit to the bottom of the liquid cavity (compared to vertically depositing to the bottom of the liquid cavity at the casting velocity), so the time spent is shorter and the cooling rate in the liquid phase is faster.

[0127] from Figure 5-6It can be seen that the traditional method does not take into account the slurry area (lap temperature T COH The above) situation of solid phase flowing with melt is deviated from the actual situation. However, the present invention fully considers the internal flow of slurry zone in semi-continuous casting process when calculating the cooling curve, and the obtained cooling curve and instantaneous cooling rate are more accurate than the existing methods in the prior art.

[0128] Comparative Example 2

[0129] This comparative example analyzes the cooling rate of a 420×1620 mm flat ingot 5083 in the thickness direction according to a conventional method, including the following steps:

[0130] S1, establishing a steady-state simulation model of the aluminum alloy casting process. This step is consistent with Example 2.

[0131] S2, after the calculation converges, the temperature-time curves of 10 points in the thickness direction of the ingot (vertically downward according to the casting direction) are extracted;

[0132] S3, calculate the cooling rate according to formula (3), and obtain the cooling rate as Figure 8 shown.

[0133] from Figure 8 It can be seen that the traditional method does not take into account the flow of the solid phase in the slurry zone with the melt, which is inconsistent with the actual situation. However, the present invention fully considers the internal flow of the slurry zone in the semi-continuous casting process when calculating the cooling curve, and the obtained cooling rate is more accurate than the existing methods in the prior art.

[0134] 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 method for solving solidification characteristic parameters in a semi-continuous casting process, characterized in that: The following steps are involved: S1, solving the flow field and temperature field: a three-dimensional geometric model is established according to the casting equipment and the ingot shape, and a thermal-fluid coupling numerical simulation is performed on the semi-continuous casting process to solve the flow field and temperature field of the semi-continuous casting process; S2, solving the cooling curve: after the casting enters the steady state, the streamline or trace of the solidification process is extracted with the point of the solidified area on the cross section of the ingot as the end point, and the node coordinates, temperature T and time t on the streamline or trace are derived, and the time t and temperature T on the streamline or trace are taken to solve the cooling curve; repeat the above operation to obtain the cooling curve of any point on the cross section of the entire ingot; S3, cooling curve data analysis: perform data analysis on the cooling curve of a certain point to obtain the solidification characteristic parameters of the point. The solidification characteristic parameters include solidification time, which refers to the time from the liquidus temperature T L To solidus temperature T S The time elapsed, the solution method of the solidification time is: in, t L-S Indicates the setting time; t L Indicates that the temperature on a cooling curve reaches the liquidus temperature T L time; t S Indicates that the temperature on the cooling curve reaches the solidus temperature T S time.

2. The method for solving the solidification characteristic parameters of a semi-continuous casting process according to claim 1, characterized in that: The S3 also includes: analyzing the obtained multiple cooling curves to obtain the distribution of solidification characteristic parameters on the entire ingot cross section.

3. The method for solving the solidification characteristic parameters of a semi-continuous casting process according to claim 1, characterized in that: The solidification characteristic parameters also include an instantaneous cooling rate, and the method for calculating the instantaneous cooling rate is: in, represents the instantaneous cooling rate of the i-th node on a cooling curve; represents the temperature of the i-th node on the cooling curve; represents the temperature of the i+1th node on the cooling curve; represents the time corresponding to the i-th node on the cooling curve; Indicates the time corresponding to the i+1th node on the cooling curve.

4. The method for solving the solidification characteristic parameters of a semi-continuous casting process according to claim 1, characterized in that: The solidification characteristic parameter also includes a cooling rate in a certain cooling temperature range, and the method for calculating the cooling rate includes: a. Determine the upper and lower temperature limits of the cooling temperature range; b. Obtain the time corresponding to the upper temperature limit and the lower temperature limit on a cooling curve; c. Then calculate the cooling rate according to the following formula: in, represents the cooling rate in the cooling temperature range; T up Indicates the upper temperature limit of the cooling temperature range; T down Indicates the temperature bottom line of the cooling temperature range; t up Indicates the time corresponding to the upper temperature limit on the cooling curve; t down It indicates the time when the temperature bottom line corresponds to on the cooling curve.

5. The method for solving the solidification characteristic parameters of a semi-continuous casting process according to claim 4, characterized in that: Assign the coordinates of the end point of the cooling curve to the calculated cooling rate , that is, the cooling rate of a point on the cross section of the ingot.

6. The method for solving the solidification characteristic parameters of a semi-continuous casting process according to claim 5, characterized in that: The cooling rate is calculated for all points on the ingot cross section to obtain the cooling rate distribution of the ingot cross section.

7. The method for solving the solidification characteristic parameters of the semi-continuous casting process according to any one of claims 4 to 6, characterized in that: When studying the high-temperature phase that precipitates preferentially in an alloy, the T up The value is equal to the precipitation temperature of the high temperature phase, T down The value is higher than the temperature corresponding to the solidus of the alloy; the high temperature phase refers to the alloy composition whose nucleation is above the liquidus.

8. The method for solving the solidification characteristic parameters of the semi-continuous casting process according to any one of claims 4 to 6, characterized in that: When studying the cooling rate of primary aluminum grains in the liquid cavity, the T up The value is equal to the liquidus temperature , T down The value is equal to the solidus temperature .

9. The method for solving the solidification characteristic parameters of the semi-continuous casting process according to any one of claims 4 to 6, characterized in that: When studying the cooling rate after lap joint, the The value is equal to the dendrite lap temperature , T down The value is equal to the solidus temperature .

10. The method for solving solidification characteristic parameters in a semi-continuous casting process according to claim 1, characterized in that: The solidification characteristic parameters also include thermal cracking sensitivity, and the thermal cracking sensitivity is calculated as follows: in, HCS The thermal cracking sensitivity refers to the ratio of the duration of the brittle period in the late solidification period to the duration of the stress relief period; t V Indicates the duration of the stress relief period; t R Indicates the duration of the weak period after solidification; Indicates the time when the solid phase rate reaches 99%; Indicates the time when the solid phase rate reaches 90%; Indicates the time when the solid fraction reaches 40%.

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