CN114939604A - Isothermal extrusion method of aluminum alloy section - Google Patents
Isothermal extrusion method of aluminum alloy section Download PDFInfo
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Abstract
The invention discloses an isothermal extrusion method of an aluminum alloy section bar, which comprises the steps of measuring the initial heating temperature of an aluminum alloy cast bar to be extruded and the average size of subgrain of a microstructure of the section bar at each selected measuring position on the extruded section bar, calculating the temperature of a die outlet of the section bar at each measuring position according to the average size of the subgrain and Z parameters, comparing the temperature of the die outlet with the initial heating temperature before the extrusion of the section bar to obtain the temperature rise condition of each part in the extrusion process of the section bar, and further setting the gradient heating temperature of the cast bar to realize isothermal extrusion. According to the invention, the section tissue is correlated with the actual temperature, so that the accurate calculation of the outlet temperature of the extrusion die is realized, and the accurate setting of the gradient heating temperature during the isothermal extrusion of the aluminum alloy section is realized.
Description
Technical Field
The invention relates to the technical field of processing of aluminum alloy materials, in particular to an isothermal extrusion method of an aluminum alloy profile.
Background
In the conventional hot extrusion of aluminum alloys, the temperature and deformation of the cast bar are very non-uniform, which results in non-uniformity in the quality of the product in terms of size, shape, texture and properties, and isothermal extrusion, which reduces these non-uniformities, is an ideal extrusion process. The isothermal extrusion is characterized in that the temperature of metal in a deformation area near a die hole is always kept constant or basically constant in the whole extrusion process, the resistance to metal deformation and the uniformity of metal flow are kept as much as possible, so that higher extrusion speed is obtained, and meanwhile, the shape and the size of an extruded section are accurate, and the uniformity of the structure and the performance along the section and the length direction is also improved. The isothermal extrusion can ensure that the geometric dimension, the surface quality, the internal structure, the physical property and the like of the head and the tail of the whole product can achieve the best effect, thereby greatly improving the production efficiency. Therefore, the implementation of isothermal extrusion is of great importance to improve both the productivity and the quality of the extruded product.
The key technology of the isothermal extrusion process is that the temperature of an extruded product at the outlet of a die is controlled, and isothermal extrusion can be really realized only in a range of controlling the temperature fluctuation at the outlet to be very small. Therefore, two practical problems are caused, namely how to accurately measure the actual temperature of the section at the outlet of the die and how to reasonably set the heating gradient of the cast rod.
Currently, two methods are mainly adopted for measuring the outlet temperature of the section bar in industrial production: the two methods have the common defects that the actual temperature at the outlet of a die cannot be directly measured, the measured temperature is usually the temperature of a profile after the distance from the outlet of the die is 0.5-1.5m (due to the structural limitation of a front beam of an extruder), and the actual temperature of the profile is far lower than the temperature at the outlet of the die after the profile is cooled by air after the profile is discharged from the die for a period of time, so that the isothermal extrusion effect cannot be really realized if the heating gradient of a casting rod is set at the temperature. Therefore, how to accurately measure the actual temperature of the profile at the outlet of the die becomes a key problem for realizing the isothermal extrusion process.
In the technology of realizing isothermal extrusion by a blank isothermal extrusion method, no reasonable reference basis exists for setting the temperature gradient in the industry at present, the temperature gradient is often set by approximate estimation according to experience, and the final real isothermal extrusion effect is often difficult to realize completely.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an isothermal extrusion method of an aluminum alloy section, which correlates the section structure with the actual temperature, calculates the actual temperature of the section structure according to Z parameters to accurately measure the temperature, and further calculates the temperature at the outlet of an extrusion die accurately to reasonably set the gradient heating temperature gradient of the aluminum alloy section.
In order to achieve the purpose, the invention provides an isothermal extrusion method of an aluminum alloy profile, which comprises the steps of measuring the initial heating temperature of an aluminum alloy cast rod to be extruded, measuring the average size of subgrain of a microstructure of the profile at each selected measuring position on the extruded profile, calculating the temperature of a die outlet at each measuring position through a Z parameter, and performing gradient heating temperature setting on the cast rod according to the comparison calculation of the temperature of the die outlet and the initial heating temperature so as to achieve isothermal extrusion.
Preferably, the calculation of the die outlet temperature is obtained by selecting a head of the profile and a certain measuring position behind the head, and obtaining lnZ function relation formula calculation of profile deformation of the head of the profile and the certain measuring position behind the head according to the relation between the Z parameter and the deformation rate and the temperature.
Preferably, after the temperature of the outlet of the mold is compared with the initial heating temperature, the temperature increase value of each measurement position is obtained; and calculating to obtain the gradient heating temperature of the cast rod according to the temperature increase value and the preset profile extrusion temperature.
Preferably, the lnZ function is as follows:
wherein Q is deformation activation energy/J/mol, R is gas constant, R is 8.341/J/(mol. K), T is deformation temperature/K, T is F For initial heating of the profile, T R Die outlet temperature, Z, for a certain measuring position behind the head F And Z R Z for the head and a certain measuring position behind the head of the profile F And (4) parameters.
Preferably, in the isothermal extrusion process, the obtaining of the gradient heating temperature comprises the following steps:
s1, measuring to obtain the initial heating temperature of the aluminum alloy section to be extruded before extrusion;
s2, selecting each measuring position according to setting requirements, taking a metallographic sample of the section bar in each measuring position, measuring to obtain the average size of the subgrain of the microstructure of the section bar at each measuring position, and calculating to obtain the Z parameter of the section bar at each measuring position;
s3, selecting a certain measuring position behind the head and the head of the profile, and obtaining a lnZ function relation of the profile deformation at the certain measuring position behind the head and the head of the profile according to the relation between the Z parameter and the deformation rate and temperature:
calculating the die outlet temperature of the section at a certain measuring position behind the head, wherein Q is deformation activation energy/J/mol, R is a gas constant, R is 8.341/J/(mol. K), T is deformation temperature/K, and T is deformation temperature/K F Initial heating temperature, T, of the profile R Die exit temperature, Z, for a certain measuring position behind the head F And Z R Z for the head and a certain measuring position behind the head of the profile F A parameter;
s4, repeating the calculation process of the step S3 to obtain the die outlet temperature of the section bar at other measuring positions;
s5, comparing the die outlet temperature of the section at each measuring position with the initial heating temperature before the section is extruded to obtain the temperature increase value of each section;
and S6, calculating the gradient heating temperature of the cast rod according to the temperature increment value and the preset profile extrusion temperature.
Preferably, in S2, the sample is subjected to EBSD metallographic observation by making a cross section of the profile structure in each measurement position, and the average size of the subgrain of the profile microstructure at each measurement position is measured.
The preset profile extrusion temperature is the die outlet temperature of each part of the extruded profile set according to the process requirements, and the measurement position is selected according to the length of the profile, the process requirements and the like.
Preferably, the setting of the gradient heating temperature of the casting bar corresponds to the measurement position of the profile.
The invention also provides an isothermal extrusion method of the aluminum alloy section, and the gradient heating temperature is obtained by the following steps:
s1, measuring to obtain the initial heating temperature of the aluminum alloy section to be extruded before extrusion;
s2, selecting each measuring position according to setting requirements, taking a metallographic sample of the section bar in each measuring position, measuring to obtain the average size of the subgrain of the microstructure of the section bar at each measuring position, and calculating to obtain the Z parameter of the section bar at each measuring position;
s3, selecting the head part and a certain measuring position behind the head part of the profile, and obtaining a lnZ function relation of the profile deformation of the head part and the certain measuring position behind the head part of the profile according to the relation between the Z parameter and the deformation rate and the temperature:
calculating the die outlet temperature of the section at a certain measuring position behind the head, wherein Q is deformation activation energy/J/mol, R is a gas constant, R is 8.341/J/(mol. K), T is deformation temperature/K, and T is deformation temperature/K F For initial heating of the profile, T R Die exit temperature, Z, for a certain measuring position behind the head F And Z R Z for the head and a certain measuring position behind the head of the profile F A parameter;
s4, repeating the calculation process of the step S3 to obtain the die outlet temperature of the section bar at other measurement positions;
s5, comparing the die outlet temperature of the section at each measuring position with the initial heating temperature before the section is extruded to obtain the temperature increase value of each section;
and S6, calculating the gradient heating temperature of the cast rod according to the temperature increase value and the preset profile extrusion temperature.
Preferably, in S3, the Z parameter of the profile structure at each measurement position is calculated by the following formula:
lnZ＝A+Bδ -1 。
preferably, in step S4, the lnZ functional formula of the profile deformation of the profile head and a certain measuring position behind the head is obtained through the following formula of the relationship between the Z parameter and the deformation rate and the temperature
Wherein,
is strain rate/s -1 。
Preferably, in step S4, Z of the head of the profile during the extrusion process F Z of the extruded profile for the parameters and for a certain measuring position behind the head R The relationship of the parameters is:
preferably, in S2, the sample is subjected to EBSD metallographic observation by making a cross section of the profile structure in each measurement position, and the average size of the subgrain of the profile microstructure at each measurement position is measured.
The invention obtains the effect of isothermal extrusion by quantitatively analyzing the temperature rise degree in the extrusion process, because the microstructure of the section bar is usually composed of a surface coarse crystal layer and a fibrous deformation structure containing equiaxed subgrains inside, the invention calculates the actual deformation temperature in the extrusion process by calculating the real temperature of the section bar at the outlet of an extrusion die by using Zener-Hollomon parameters according to the subgrain size of the microstructure at each position of the section bar, further calculates the gradient heating temperature of a cast rod, realizes the accurate calculation of the outlet temperature of the extrusion die by correlating the section bar structure with the actual temperature, realizes the accurate setting of the gradient heating temperature in the isothermal extrusion of the cast rod section bar, and provides a reasonable and accurate calculation method of the temperature gradient for realizing the isothermal extrusion by a blank gradient heating extrusion method.
Meanwhile, the gradient heating temperature set by the invention ensures that the temperature of the metal in the deformation area near the die hole is always kept constant or basically constant, the resistance to metal deformation and the uniformity of metal flow are kept, and the pressure of the die surface is constant or basically constant, so that higher extrusion speed is obtained, and meanwhile, the shape and the size of the extruded section are accurate, and the uniformity of the structure and the performance along the section and the length direction is also improved. The isothermal extrusion can ensure that the geometric dimension, the surface quality, the internal structure, the physical property and the like of the head and the tail of the whole product can achieve the optimal effect, thereby greatly improving the production efficiency.
Drawings
FIG. 1 is a schematic view of an aluminum alloy round section of the present invention before isothermal extrusion;
FIG. 2 is a schematic view of the aluminum alloy profile of the present invention at an initial stage of isothermal extrusion;
FIG. 3 is a schematic diagram of the middle stage of isothermal extrusion of the aluminum alloy profile of the present invention;
FIG. 4 is a schematic diagram of the aluminum alloy profile of the present invention at the later stage of isothermal extrusion;
FIG. 5 is a flow chart of the isothermal extrusion method of aluminum alloy sections according to the present invention;
FIG. 6 is a flow chart of an isothermal extrusion process according to an embodiment of the present invention.
Detailed Description
The following detailed description of the present invention is provided in conjunction with the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments. Variations in structure, method, or function that may be apparent to those of ordinary skill in the art upon reading the foregoing description are intended to be within the scope of the present invention.
As shown in fig. 1-4, a schematic diagram of the whole process of the aluminum alloy cast bar (or round bar, round cast ingot) before starting isothermal extrusion, in the initial stage of extrusion, in the middle stage and in the later stage is implemented by using a gradient heating method, the cast bar to be extruded is placed in an extrusion barrel, the front end of the cast bar is extruded by a front beam and a base fixed extrusion die holder of an extruder and a die, the rear end of the cast bar is connected with an extrusion rod through an extrusion pad, the heating gradients of the cast bar in the diagram are set correspondingly according to the selected measurement positions on the profile, in this embodiment, three gradient heating temperatures are set, namely T1, T2 and T3, and the temperature of the profile corresponding to each measurement position on the profile at the die outlet is set as T1, T2 and T3. Of course, in other embodiments of the present invention, the measurement positions of the profile and the temperature heating gradient of the casting bar corresponding to the measurement positions can be theoretically set to be n according to actual situations, wherein n is a natural number greater than or equal to 2.
Under the ideal condition that the extrusion speed is unchanged and the extrusion barrel and the die reach a thermal equilibrium state, isothermal extrusion can be realized by setting a reasonable heating gradient of the cast rod. For example, assuming the temperature gradient Δ T1-T1-T2 and Δ T2-T2-T3 of the bar in the figure, the temperature of the profile extrusion at the die exit should be uniform, i.e., T1-T2-T3. In actual production, Δ T1, Δ T2, Δ Tn and the like are empirically estimated, and are not the most reasonable temperature gradients, and further, isothermal extrusion cannot be achieved due to the fact that the extrusion barrel, the die and the like do not reach a thermal equilibrium state. Among these, the unreasonable heating temperature gradient of the cast bar is the most important cause of the failure of isothermal extrusion.
Under the condition that the alloy grade, the extrusion speed, the extrusion ratio and the like are determined, the structure and the performance of the section are mainly determined by the temperature of the section at the outlet of the die, and different outlet temperatures can cause different microstructures and mechanical properties. For example, t1 is not equal to t2 is not equal to t3, the corresponding micro-structures of the section bars at the three positions of t1, t2 and t3 have obvious differences, the differences are mainly reflected by the fact that the sizes of sub-crystalline grains at different positions of the section bars are different, the actual deformation temperature of the section bars in the extrusion process is calculated by calculating the actual temperature of the section bars at the outlet of an extrusion die through the sizes of the sub-crystalline grains in the micro-structures at all positions of the section bars and utilizing Zener-Hollomon parameters, and the heating temperature gradient of the cast bars is further calculated.
Since the microstructure of the profile generally consists of a coarse crystalline layer on the surface and a fibrous deformed structure containing equiaxed subgrains on the inside. The size of the subgrains is related to the Z parameter as follows:
lnZ＝A+Bδ -1 (I)
wherein Z is a Zener-Hollomon parameter, A and B are material constants, and δ is a subgrain average size. The relationship of the Z parameter to deformation rate and temperature is as follows:
wherein
Is strain rate/s -1 Q is deformation activation energy/J/mol, R is a gas constant, R is 8.341/J/(mol. K), and T is deformation temperature/K.
Considering the rate of deformation of the material at the center of the section of the profile at different positions during constant-speed extrusion
Are identical except for the deformation temperature T. The deformation temperature of the profile head during extrusion is assumed to be the initial deformation temperature T F Then Z of the corresponding profile head F Z of the extruded profile for the parameters and for a certain measuring position behind the head R The parameters have the following relations:
this can result in:
by expressing equation (5) as a function of lnZ, we obtain:
and the initial deformation temperature T of the head of the profile F And Z of the head of the profile F The parameters can be obtained by constitutive equation and microstructure characterization, so that the deformation temperature T of the profile at different measurement positions in the deformation process R The temperature gradient can be calculated by the formula, and then the extrusion casting rod can be subjected to gradient heating to obtain the temperature gradient same as the temperature rise, so that the extrusion is ensured to be carried out at the equal temperature.
For the round ingot shown in fig. 1-4, for example, the initial heating temperature of the head end of the casting rod for extrusion is 480 ℃, the head, middle and tail portions of the profile are selected as the measurement positions, and the temperatures t1, t2, t 520, and t3 of the head, middle and tail portions of the profile at the outlet of the die are calculated according to the above method, which indicates that the temperature rises of the head, middle and tail portions of the profile at the measurement positions are 20 ℃, 40 ℃ and 60 ℃, respectively, so that the temperature gradients among the head, middle and tail portions of the corresponding casting rod for extrusion should correspond to the temperature rises, and if the extrusion temperature, i.e., the preset profile extrusion temperature, is 520 ℃, the gradient heating temperatures of the head, middle and tail portions of the casting rod should be 500 ℃, 480 ℃ and 460 ℃, respectively.
Therefore, as shown in fig. 5, in the isothermal extrusion process of the aluminum alloy profile of the present invention, the obtaining of the gradient heating temperature at each measurement position of the profile comprises the following steps:
s1, measuring and obtaining the initial heating temperature T when the extrusion of the aluminum alloy section to be extruded begins F ；
S2, selecting each measuring position to be measured according to the setting requirements of the process, the length of the section bar and the like, taking a metallographic sample of the section bar in each measuring position, preparing an EBSD metallographic observation sample for the section bar tissue cross section of each measuring position, measuring to obtain the subgrain average size of the section bar microstructure at each measuring position, calculating to obtain the Z parameter of the section bar tissue at each measuring position through the following formula,
lnZ＝A+Bδ -1
s3, selecting the head of the section and a certain measuring position behind the head, according to the relation between the Z parameter and the deformation rate and temperature,
obtaining lnZ values and lnZ functional relations of the deformation of the aluminum alloy section at the head part and a certain measuring position behind the head part:
wherein,
is strain rate/s -1 Q is the strain activation energy/J/mol, R is a gas constant, R is 8.341/J/(mol. K), T is a deformation temperature/K, Z F And Z R Respectively the Z parameter of the head of the section and a certain measuring position behind the head,
calculating the die outlet temperature T of a certain section of section bar selected behind the head R 。
S4, repeating the calculation process of the step S3 to obtain the mold outlet temperature of other measurement positions;
s5, setting the die outlet temperature T of each section R Comparing the initial heating temperature with the initial heating temperature before the section bar is extruded to obtain the temperature increase value of each measuring position;
and S6, adjusting the heating setting temperature of each measuring position according to the temperature increase value and the preset profile extrusion temperature, and calculating to obtain the gradient heating temperature of the cast rod.
The preset profile extrusion temperature is the die outlet temperature of each part of the extruded profile set according to the process requirements, and the measurement position is selected according to the length of the profile, the process requirements and the like. The gradient heating temperature of the casting bar, such as the gradient number of the temperature, is set corresponding to the measuring position and the measuring number of the section bar. If the preset gradient heating temperature is 3-section gradient, at least 3 points on the section bar need to be selected for sampling.
The calculation process of the gradient heating temperature is described below with an embodiment.
Extruding a 6061 alloy round cast ingot with the specification of phi 178 x 500mm on an extruder with the tonnage of 18MN to produce an extruded sheet with the section specification of 20 x 40mm, wherein the extruded length of the section bar is 15.6m, the extrusion ratio is 30, the extrusion speed is 3mm/s, the initial heating temperature of the cast ingot before extrusion is 490 ℃, namely the initial heating temperature T of the original cast ingot before extrusion at the die opening F 490 ℃, the initial heating temperature, that is, the initial temperature of the extruded sheet is 490 ℃; selecting three measuring positions of the head, the middle and the tail of the section, respectively setting the die outlet temperatures of the head, the middle and the tail of the extruded sheet as t1, t2 and t3, respectively sampling the head, the middle and the tail of the section with the length of 15.6 meters, respectively preparing EBSD metallographic observation samples on the cross sections of the section, and respectively carrying out EBSD metallographic observation on the samplesMeasurement, the following results were obtained:
the average size of the primary tissue subgrain is 2.03 mu m;
the average size of the head tissue subgrain is 2.12 mu m;
the average size of the subgrains of the middle structure is 2.25 mu m;
the average size of the tail tissue subgrade is 2.32 mu m;
substituting the above sub-crystal measurement results into the following formula
lnZ＝A+Bδ -1
The 6061 alloy has a material constant a of 27.4, a gas constant R of 8.341/J/(mol · K) of 61, a Q of 249.67KJ/mol, and an initial heating temperature of the ingot at the die opening of 490 ℃, and therefore the initial temperature of the sheet after extrusion is considered to be 490 ℃, and can be calculated from the above formula:
lnZ first stage ＝27.4+61*2.03 -1 ＝57.449
lnZ Head ＝27.4+61*2.32 -1 ＝53.693
lnZ In ＝27.4+61*2.65 -1 ＝50.419
lnZ Tail ＝27.4+61*2.86 -1 ＝48.728
Further calculations yield:
t1＝522℃
t2＝554℃
t3＝572℃
therefore, the die outlet temperatures of the head part, the middle part and the tail part of the section are 522 ℃, 554 ℃ and 572 ℃ respectively in the actual extrusion process, and the temperatures of the head part, the middle part and the tail part of the extruded section are respectively increased by 32 ℃, 64 ℃ and 82 ℃ compared with the initial heating temperature of the cast ingot before extrusion, so that the heating temperature of the cast ingot is set according to a certain gradient if the temperature of the section at the die outlet in the extrusion process, namely the preset extrusion temperature of the section is 560 ℃, and the gradient heating temperatures of the head part, the middle part and the tail part of the cast ingot are respectively set to 528 ℃, 496 ℃ and 478 ℃ according to the calculated temperature rise value.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications. It is intended that the scope of the invention be defined by the claims and their equivalents.
Claims (10)
1. The isothermal extrusion method of the aluminum alloy profile is characterized by measuring the initial heating temperature of an aluminum alloy cast rod to be extruded, measuring the average size of subgrain microstructure of the profile at each selected measuring position on the extruded profile, calculating the temperature of a die outlet at each measuring position through a Z parameter, and performing gradient heating temperature setting on the cast rod according to the comparison between the temperature of the die outlet and the initial heating temperature so as to realize isothermal extrusion.
2. The method for isothermal extrusion of aluminum alloy sections according to claim 1, wherein the die exit temperature is calculated by selecting a certain measuring position behind the head of the section and obtaining lnZ function relation expression of section deformation at the certain measuring position behind the head of the section and according to the relation between the Z parameter and the deformation rate and temperature.
3. The method of claim 2, wherein the lnZ function is as follows:
wherein Q is the strain activation energy/J/mol, R is the gas constant, R is 8.341/J/(mol. K), T is the strain temperature/K, T is F Initial heating temperature, T, of the profile R Die exit temperature, Z, for a certain measuring position behind the head F And Z R Respectively the Z parameter of the head of the profile and a certain measuring position behind the head.
4. Isothermal extrusion process of aluminium alloy sections according to claim 1, characterized by comprising the following steps:
s1, measuring and obtaining the initial heating temperature of the aluminum alloy cast rod to be extruded when the extrusion is started;
s2, selecting each measuring position according to setting requirements, taking a metallographic sample of the section bar at each measuring position, measuring to obtain the average size of the subgrain of the microstructure of the section bar at each measuring position, and calculating to obtain the Z parameter of the section bar at each measuring position;
s3, selecting the head part and a certain measuring position behind the head part of the profile, and obtaining a lnZ function relation of the profile deformation of the head part and the certain measuring position behind the head part of the profile according to the relation between the Z parameter and the deformation rate and the temperature:
calculating the die outlet temperature of the section at a certain measuring position behind the head, wherein Q is deformation activation energy/J/mol, R is a gas constant, R is 8.341/J/(mol. K), T is deformation temperature/K, and T is deformation temperature/K F For initial heating of the profile, T R Die exit temperature, Z, for a certain measuring position behind the head F And Z R Z parameters of the head and a certain measuring position behind the head of the profile are respectively set;
s4, repeating the calculation process of the step S3 to obtain the die outlet temperature of the section bar at other measuring positions;
s5, comparing the die outlet temperature of the profile at each measuring position with the initial heating temperature at the beginning of extrusion to obtain the temperature increase value at each measuring position;
and S6, calculating the gradient heating temperature of the cast rod according to the temperature increase value and the preset profile extrusion temperature.
5. The method for isothermal extrusion of aluminum alloy profiles according to claim 4, wherein EBSD metallographic observation samples are prepared for the cross section of the profile structure at each measurement position in S2, and the average size of subgrain of the microstructure of the profile at each measurement position is measured.
6. An isothermal extrusion method of an aluminum alloy profile is characterized by comprising the following steps:
s1, measuring and obtaining the initial heating temperature of the aluminum alloy cast rod to be extruded when the extrusion is started;
s2, selecting each measuring position according to setting requirements, taking a metallographic sample of the section bar at each measuring position, measuring to obtain the average size of the subgrain of the microstructure of the section bar at each measuring position, and calculating to obtain the Z parameter of the section bar at each measuring position;
s3, selecting a certain measuring position behind the head and the head of the profile, and obtaining a lnZ function relation of the profile deformation at the certain measuring position behind the head and the head of the profile according to the relation between the Z parameter and the deformation rate and temperature:
calculating the die outlet temperature of the section at a certain measuring position behind the head, wherein Q is deformation activation energy/J/mol, R is a gas constant, R is 8.341/J/(mol. K), T is deformation temperature/K, and T is deformation temperature/K F Initial heating temperature, T, of the profile R Die outlet temperature, Z, for a certain measuring position behind the head F And Z R Z parameters of the head and a certain measuring position behind the head of the profile are respectively set;
s4, repeating the calculation process of the step S3 to obtain the die outlet temperature of the section bar at other measuring positions;
s5, comparing the die outlet temperature of the profile at each measuring position with the initial heating temperature at the beginning of extrusion to obtain the temperature increase value at each measuring position;
and S6, calculating the gradient heating temperature of the cast rod according to the temperature increase value and the preset profile extrusion temperature.
7. The method as claimed in claim 6, wherein the Z parameter of the profile structure at each measurement position is calculated in S3 according to the following formula:
lnZ＝A+Bδ -1 。
8. the method of claim 6, wherein in step S4, the following formula of Z parameter as deformation rate and temperature is used to obtain lnZ functional formula of profile deformation at the head and a certain measurement position behind the head
Wherein,
is strain rate/s -1 。
9. The method of claim 6, wherein in step S4, Z is the profile head Z during extrusion F Z of the extruded profile for the parameters and for a certain measuring position behind the head R The relationship of the parameters is:
10. the method as claimed in claim 6, wherein the step S2 comprises obtaining EBSD metallographic observation samples of the section bar microstructure at each measuring position by measuring the section bar microstructure cross section at each measuring position, and obtaining the average size of the subgrain of the section bar microstructure at each measuring position.
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