CN110983129B - An integrated process control method for improving the flanging performance of aluminum alloy sheets for automobiles - Google Patents

Abstract

The invention relates to the technical field of aluminum alloys, in particular to an integrated process control method for improving the flanging performance of aluminum alloy sheets for automobiles. The method includes: configuring Al-Mg-Si-Cu-Zn series alloy; intermediate frequency induction melting, cooling the alloy melt after melting; adopting temperature field and ultrasonic physical field to cool the alloy melt in two stages and repeating the synergistic treatment ; Pouring the alloy melt into a forming die and cooling; Hot rolling process treatment; Two-stage heat treatment to control the size and distribution of the alloy structure and primary iron-rich phase; Large deformation cold rolling treatment; The treated alloy sample is cooled to room temperature; the quenched sample is transferred to an aging furnace for cooling and pre-aging treatment. The method of the invention is suitable for the manufacture of new aluminum alloys for automobiles, especially for the manufacture of complex-shaped parts with high requirements on stamping formability, strength, surface quality and edge bending performance.

Description

Integrated process regulation and control method for improving automobile aluminum alloy plate flanging performance

Technical Field

The invention belongs to the technical field of aluminum alloy, and particularly provides an integrated process regulation and control method for improving the bending performance of an aluminum alloy plate for an automobile, aiming at the current application situation that the bending performance of an aluminum alloy outer plate of an automobile body is still not high enough and the performance is continuously improved in the automobile field.

Background

In recent years, the automobile industry is developed rapidly with the continuous improvement of the living standard of people, but the environmental pollution and the energy crisis caused during the development are more and more serious. For this reason, governments of various countries adopt various means for control and improvement, and in comparison, the weight reduction of automobiles is one of effective ways to solve the above problems. Aluminum alloy has become a key material for automobile light weight due to the characteristics of light weight, corrosion resistance, high specific strength, easy processing, beautiful surface, abundant reserves, recyclability and the like. In addition, according to statistics, the energy saved by adopting the aluminum alloy in the automobile is 6-12 times of the energy consumed by the original aluminum used for producing the part. Therefore, the development and application of advanced aluminum alloy sheets for automobile light weight have attracted extensive attention from automobile manufacturers and researchers all over the world, and the amount of aluminum for automobiles has increased year by year in recent years.

In general, at present, wrought aluminum alloy sheets for automobile weight reduction mainly include 5xxx (Al-Mg) and 6xxx (Al-Mg-Si-Cu) aluminum alloy sheets applied to inner and outer panels of automobile bodies, and in addition, as the weight reduction of automobiles progresses, automobile body structural members are gradually beginning to be manufactured by using high-strength 7xxx (Al-Zn-Mg-Cu) aluminum alloy sheets to solve the problems of steel-aluminum dissimilar metal connection, poor corrosion resistance and the like. Al-Mg-Si-based aluminum alloys, such as AA6016, AA6111, and AA6022, are more widely used in the manufacture of outer panels of vehicle bodies because of their superior press formability and increase in the amount of hardening by baking finish, compared with other alloys. However, the alloy still has the disadvantages of higher cost, and further improvement of formability, crimping property and strength, etc. compared with the steel for automobiles.

In order to improve the comprehensive performance of the Al-Mg-Si-Cu alloy and reduce the production cost of the Al-Mg-Si-Cu alloy, a novel Al-Mg-Si-Cu-Zn-Fe-Mn alloy material containing Fe and Zn is developed by the recent research team, the forming performance, the edge bending performance and the baking varnish hardening increment of the alloy are all greatly improved by regulating and controlling the process, and because the recovered aluminum generally contains elements such as Fe, Zn and the like, the smelting preparation of the novel aluminum alloy material can also be widely carried out by using the recovered aluminum, so that the production cost of the alloy is greatly reduced. However, even in this case, the production cost and the crimping performance of the aluminum alloy sheet are still to be further improved compared to steel products, and only then, the aluminum alloy sheet can be more rapidly applied to the automobile field and the development of aluminum alloys for reducing the weight of automobiles is rapidly promoted.

Considering that dendritic, rod-shaped and thick primary iron-rich phases are mainly formed in the alloy casting process, the iron-rich phases are crushed and refined in the subsequent hot working process to form a structure with thick particles and fine particles, the thick particles can induce recrystallization nucleation to generate PSN effect in the subsequent heat treatment, the fine particles can prevent recrystallization grains from growing, and finally the coarse and fine particles can obviously weaken the texture of the pre-aged alloy plate and greatly improve the forming performance. However, it is difficult to completely crush coarse particles during hot working, and finally, the forming performance and the flanging performance of the alloy sheet are adversely affected due to incomplete crushing of the coarse particles or residual microcracks of the coarse particles, and the like, and the influence on the flanging performance of the alloy sheet is particularly remarkable. Therefore, how to reasonably control the size, the form, the composition, the distribution and the like of the primary iron-rich phase through the integrated regulation and control of the casting process and the hot working, and further better avoid the adverse effect caused by residual microcracks in the coarse particles due to incomplete crushing, and has important significance for further greatly improving the comprehensive performance of the alloy and large-scale popularization.

Disclosure of Invention

In order to solve the problems and better meet the actual application requirements of the aluminum alloy plate for light weight of the automobile, and the problem that the forming performance, the crimping performance, the baking varnish hardening performance and the like of the Al-Mg-Si-Cu alloy plate are not high enough, the invention provides an integrated process regulation and control method which is more suitable for promoting the improvement of the crimping performance of the aluminum alloy plate. According to the invention, the synergistic effect of the temperature field and the ultrasonic physical field is fully utilized to effectively control nucleation, growth, distribution and the like of original phases during alloy casting, so that multi-scale original phases are distributed in the as-cast alloy matrix, the problems of serious segregation and the like of original iron-rich phases in the traditional cast alloy matrix are effectively inhibited, and meanwhile, the multi-scale original phases can be better discretely distributed in the alloy matrix; on the basis, the primary phase distribution in the alloy matrix and the alloy structure and texture are further controlled in an integrated process by combining with the subsequent hot working, so that the structure of the pre-aged alloy plate is obviously refined, the texture is distributed nearly randomly, and meanwhile, the multi-scale primary phase can be uniformly dispersed in the alloy matrix, thereby achieving the purpose that the pre-aged Al-Mg-Si-Cu-Zn alloy plate has excellent flanging performance.

According to the first aspect of the invention, the integrated process control method for improving the hemming performance of the aluminum alloy plate for the automobile is provided, the aluminum alloy for the automobile is an Al-Mg-Si-Cu-Zn alloy, and the Al-Mg-Si-Cu-Zn alloy comprises the following chemical components in percentage by mass: 0.5-3.7 wt% of Zn, Mg: 0.6-1.0 wt%, Si: 0.4 to 1.0wt%, Cu: 0.1 to 0.4wt%, 0.1 to 0.7wt% of Fe, Mn: 0.3-0.7 wt%, Ni less than or equal to 0.12wt%, Cr less than 0.02wt%, Ti less than or equal to 0.1wt%, B less than 0.01wt%, and the balance of Al; the integrated process control method specifically comprises the following steps:

(1) preparing Al-Mg-Si-Cu-Zn alloy by adopting recovered aluminum or common aluminum;

(2) performing medium-frequency induction melting, and cooling the melt from 780 ℃ to 720 ℃ after the melting is finished;

(3) carrying out repeated synergistic treatment on the alloy melt cooling process for 2 times in stages by adopting a temperature field and an ultrasonic physical field (the power of an ultrasonic generator is 0.8-2 kW, the frequency is 19-22 kHz, the time is 5-30 min, the insertion mode is that an ultrasonic rod and the surface of the melt form 45-90 degrees, the melt cooling rate is 3-12 ℃/min, the melt temperature is controlled to be more than 690 ℃ in the first stage, the melt temperature is controlled to be more than 670 ℃ in the second stage, and the interval time between the first stage and the second stage is 2-15 min);

(4) pouring the melt into a forming die (cooling rate: 20-300 ℃/s);

(5) hot rolling (initial rolling temperature: 480-510 ℃, final rolling temperature: more than 300 ℃ and rolling deformation of 50-75%);

(6) the size and the distribution state of alloy tissues and primary iron-rich phases are regulated and controlled by two-stage heat treatment (the first stage is 440-485 ℃/1-3 h, the second stage is 520-575 ℃/7-20 h, the heating rate is 10-30 ℃/h, and the cooling rate is 46-200 ℃/h);

(7) cold rolling with large deformation (deformation: 40-95%);

(8) high-temperature short-time solution treatment (540-;

(9) transferring the quenched sample into an aging furnace within 1.5min for cooling and pre-aging treatment (the temperature is lower than 100 ℃, the time is longer than 10h, and the cooling rate is 2-4 ℃/h),

based on the integrated process regulation, the developed alloy plate can be ensured to have excellent flanging performance.

Preferably, the medium-frequency induction melting process comprises the following steps: firstly, melting recovered aluminum or general aluminum, controlling the temperature to be 780-840 ℃, then respectively adding Al-20wt% Fe, Al-10wt% Mn, Al-10wt% Cr and Al-10wt% Ti intermediate alloys, respectively adding Al-50wt% Cu and Al-20wt% Si intermediate alloys after melting, then stirring the melt for 5min at high power (if Ni element is required to be added, simultaneously adding pure Ni into the melt at the temperature, stirring the melt for 10min by utilizing the high power), then controlling the temperature to be above 720 ℃, respectively adding pure Zn and pure Mg, respectively pressing the melt into the bottom of the melt by using a graphite bell jar during adding, taking out the bell jar after the melt is completely melted, and regulating and controlling the power of a medium-frequency induction furnace to enable the temperature of the alloy melt to be stabilized at 720 ℃ again for next ultrasonic physical field treatment.

Preferably, the temperature field and the ultrasonic physical field carry out 2 times of repeated cooperative treatment in stages on the alloy melt cooling process (the power of an ultrasonic generator is 1.5-2 kW, the frequency is 20-22 kHz, and the time is 5-25 min, the insertion mode is that an ultrasonic rod and the melt surface form 70-90 degrees, the melt cooling rate is 3-10 ℃/min, the temperature of the melt is controlled to be above 700 ℃ in the first stage, the temperature of the melt is controlled to be above 680 ℃ in the second stage, and the interval time between the first stage and the second stage is 3-10 min).

Preferably, the hot rolling process comprises the following specific processes: the initial rolling temperature: 480-505 ℃; the finishing temperature is as follows: above 300 ℃, rolling deformation of 52-73%, deformation mode: and (4) unidirectional rolling.

Preferably, the specific process of the two-stage high-temperature heat treatment process is as follows: the first stage is as follows: 470-485 ℃/1.5-3 h, the second stage is: 530-565 ℃/7-18 h, the heating rate is 10-30 ℃/h, and the cooling rate is 50-200 ℃/h.

Preferably, the large-deformation cold rolling process specifically comprises the following steps: cold rolling (deformation amount: 70-93%, deformation temperature: room temperature).

Preferably, the specific process of the high-temperature short-time solution treatment is as follows: 545-565 ℃/1-6min, the heating rate is more than 100 ℃/s, and then the alloy sample after solution treatment is cooled to the room temperature from the solution treatment temperature at the cooling rate of more than 200 ℃/s.

Preferably, the cooling pre-aging treatment process specifically comprises the following steps: transferring the quenched sample into an aging furnace within 1.5min for cooling and pre-aging treatment, wherein the treatment temperature is as follows: below 85 ℃, time: 11-14 h, and the cooling rate is 3-3.6 ℃/h.

According to a second aspect of the present invention, there is provided an aluminum alloy sheet for an automobile, which is an Al-Mg-Si-Cu-Zn alloy sheet, the Al-Mg-Si-Cu-Zn alloy sheet being prepared and controlled by the integrated process control method according to any one of the above aspects,

the Al-Mg-Si-Cu-Zn alloy comprises the following chemical components in percentage by mass: 0.5-3.7 wt% of Zn, Mg: 0.6-1.0 wt%, Si: 0.4 to 1.0wt%, Cu: 0.1 to 0.4wt%, 0.1 to 0.7wt% of Fe, Mn: 0.3-0.7 wt%, Ni less than or equal to 0.12wt%, Cr less than 0.02wt%, Ti less than or equal to 0.1wt%, B less than 0.01wt%, and the balance of Al.

The alloy plate regulated and controlled by the integrated process can show excellent bending performance.

According to a third aspect of the present invention, there is provided a use of the aluminum alloy sheet for automobiles as described in the above aspect in automobiles.

The invention has the beneficial effects that:

by adopting the technical scheme, the invention has the following advantages: the invention not only can ensure that the primary iron-rich phase in the Al-Mg-Si-Cu-Zn-Fe alloy is distributed in a multi-scale manner, but also effectively avoids the segregation growth of the primary iron-rich phase in the casting process; meanwhile, the combination with subsequent further hot working integrated process regulation and control can ensure that the primary relative alloy structure and performance have positive influence, and the pre-aged alloy plate can show excellent flanging performance. The invention is very suitable for processing and producing aluminum alloy materials for automobiles, and producing and using other aluminum alloy materials with specific requirements on the original phase distribution state, and is also suitable for being applied to other technical industries with higher requirements on the organization and comprehensive performance of other series of aluminum alloy materials.

Drawings

FIG. 1 shows a flow chart of an integrated process control method for improving the hemming performance of an aluminum alloy sheet for an automobile according to the present invention;

FIG. 2 shows an as-cast SEM structure photograph of comparative example 1 treated alloy # 1;

FIG. 3 shows the prior aged 1# alloy crimp morphology and SEM microstructure photograph treated with comparative example 1;

FIG. 4 shows SEM structure (a) and outer surface morphology (b) of the alloy # 1 in the pre-aged state of example 1;

FIG. 5 shows the SEM structure (a) and the morphology (b) of the outer surface of the pre-aged alloy No. 1 of the example 2 after bending;

FIG. 6 is a TEM photograph showing the dispersed particle distribution in the two-stage homogenized 2# alloy matrix of example 3;

FIG. 7 shows the SEM structure (a) and the morphology (b) of the outer surface of the pre-aged 2# alloy of example 3 after bending.

Detailed Description

The invention will be further supplemented and explained below with reference to specific embodiments.

The invention provides an integrated process regulation method for improving the edge bending performance of an aluminum alloy plate for an automobile, aiming at the problems that impurity elements such as Fe are inevitably introduced during the casting of Al-Mg-Si-Cu alloy for the automobile, dendritic, rod-shaped or coarse granular Al (FeMn) Si primary iron-rich phases are further generated during the traditional casting, and the iron-rich phases are crushed and refined in the subsequent hot working process, but the forming performance and the edge bending performance of the aluminum alloy plate are also adversely affected due to incomplete crushing or residual microcracks of coarse particles and the like. In the casting process, the nucleation, growth and distribution of the primary iron-rich phase are comprehensively regulated and controlled through the synergistic effect of the temperature field and the ultrasonic physical field, so that the segregation of the primary iron-rich phase can be effectively inhibited, and the size of the primary iron-rich phase is characterized by multi-scale distribution; on the basis, the primary iron-rich phase, the size, the form, the orientation and the like of alloy grains are further regulated and controlled by combining a proper hot working process, so that on one hand, the uniform distribution degree of the multi-scale primary iron-rich phase can be further improved, the evolution of an alloy structure is positively influenced, on the other hand, the alloy grains can be fine and are distributed nearly randomly, and the pre-aged alloy plate can show excellent edge bending performance. The method is very suitable for manufacturing novel aluminum alloy for automobiles, and particularly suitable for manufacturing parts with complex shapes, which have higher requirements on stamping forming performance, strength, surface quality, bending performance and the like.

According to the integrated process control method for improving the automobile aluminum alloy plate flanging performance, as shown in figure 1, the following technical route is adopted:

step 101: disposition of Al-Mg-Si-Cu-Zn system alloy with recycled aluminum or plain aluminum → step 102: medium frequency induction melting → step 103: after smelting, cooling the melt from 780 ℃ to 720 ℃ → step 104: carrying out repeated synergistic treatment on the alloy melt cooling process for 2 times in stages by adopting a temperature field and an ultrasonic physical field (the power of an ultrasonic generator is 0.8-2 kW, the frequency is 19-22 kHz, the time is 5-30 min, the insertion mode is that an ultrasonic rod and the surface of the melt form 45-90 degrees, the melt cooling rate is 3-12 ℃/min, the melt temperature is controlled to be more than 690 ℃ in the first stage, the melt temperature is controlled to be more than 670 ℃ in the second stage, and the interval time between the first stage and the second stage is 2-15 min) → step 105: pouring the melt into a forming die (cooling rate: 20-300 ℃/s) → step 106: hot rolling (initial rolling temperature: 480-510 ℃, final rolling temperature: 300 ℃ or higher, rolling deformation 50-75%) → step 107: the size and distribution state of alloy structure and primary iron-rich phase are regulated and controlled by two-stage heat treatment (the first stage is 440-485 ℃/1-3 h, the second stage is 520-575 ℃/7-20 h, the heating rate is 10-30 ℃/h, the cooling rate is 46-200 ℃/h) → step 108: large deformation cold rolling (deformation: 40-95%) → step 109: carrying out high-temperature short-time solution treatment (540-575 ℃/1-10min), and then cooling the alloy sample subjected to solution treatment from the solution treatment temperature to the room temperature at a cooling rate of more than 200 ℃/s → step 110: transferring the quenched sample into an aging furnace within 1.5min for cooling and pre-aging treatment (the temperature is lower than 100 ℃, the time is longer than 10h, and the cooling rate is 2-4 ℃/h). Therefore, the developed alloy plate can be ensured to have excellent flanging performance.

Specifically, the treatment process comprises the following steps: the raw materials respectively adopt recycled aluminum or common aluminum, industrial pure Mg, industrial pure Zn, pure Ni, intermediate alloys such as Al-20wt% Si, Al-50wt% Cu, Al-20wt% Fe, Al-10wt% Mn, Al-10wt% Cr, Al-10wt% Ti and the like. Melting recycled aluminum or common aluminum by using medium-frequency induction melting, controlling the temperature to be 780-840 ℃, then respectively adding Al-20wt% of Fe, Al-10wt% of Mn, Al-10wt% of Cr and Al-10wt% of Ti intermediate alloy, respectively adding Al-50wt% of Cu and Al-20wt% of Si intermediate alloy after melting, then stirring the melt for 5min at high power, (if needing to add Ni element, simultaneously adding pure Ni into the melt at the temperature, stirring the melt for 10min by using high power), then controlling the temperature to be above 720 ℃, respectively adding pure Zn and pure Mg, respectively pressing the pure Zn and the pure Mg into the bottom of the melt by using a graphite bell jar during adding, taking out the bell jar after the pure Ni is completely melted, and regulating and controlling the power of a medium-frequency induction furnace to enable the temperature of the alloy melt to be stabilized at 720 ℃ again for next ultrasonic physical field treatment. The specific chemical compositions of the alloys of the invention are shown in table 1:

TABLE 1 alloy compositions (mass%; wt%) for carrying out the invention

Mg

Si

Cu

Fe

Mn

Zn

Cr

Ti

B

Ni

Al

1#

0.9

0.7

0.2

0.4

0.5

3.0

<0.02wt％

≤0.1wt％

<0.01

<0.01

Balance of

2#

0.9

0.7

0.2

0.4

0.5

3.0

<0.02wt％

≤0.1wt％

<0.01

0.1

Balance of

When the temperature of the melt is 720 ℃, carrying out repeated synergistic treatment on the alloy melt in stages for 2 times by using a temperature field and an ultrasonic physical field (the power of an ultrasonic generator is 0.8-2 kW, the frequency is 19-22 kHz, the time is 5-30 min, the insertion mode is that an ultrasonic rod and the surface of the melt form 45-90 degrees, the temperature of the melt is 3-12 ℃/min, the temperature of the melt is controlled to be more than 690 ℃ in the first stage, the temperature of the melt is controlled to be more than 670 ℃ in the second stage, the interval time between the first stage and the second stage is 2-15 min) → pouring the melt, and the rolling deformation amount is 50-75%) → two-stage heat treatment to regulate and control the sizes and the distribution state of an alloy structure and a primary iron-rich phase (the first stage is: 440-485 ℃/1-3 h, the second stage is as follows: 520-575 ℃/7-20 h, a heating rate of 10-30 ℃/h, a cooling rate of more than 46 ℃/h) → cold rolling (deformation: 40-95%) or cold rolling (deformation: 30-60%) + intermediate annealing (annealing temperature: 380-420 ℃/0.5-3 h), cold rolling (cold rolling deformation: 30-60%) → high-temperature short-time solution treatment (540-575 ℃/1-10min), then cooling the alloy sample after the solution treatment from the solution treatment temperature to room temperature at a cooling rate of more than 200 ℃/s → transferring the quenched sample into an aging furnace within 1.5min for cooling pre-aging treatment (temperature: below 100 ℃, time: the temperature reduction rate is 2-4 ℃/h) for more than 10h, and the developed alloy plate can be ensured to have excellent flanging performance through the integrated process regulation.

Comparative example 1

The alloy 1# is prepared by adopting the following intermediate frequency induction melting and casting modes, firstly, adding pure aluminum into a crucible and melting, controlling the temperature to be 780-880 ℃, then sequentially adding intermediate alloys of Al-20wt% Si, Al-50wt% Cu, Al-20wt% Fe and Al-10wt% Mn, preserving heat for 5-10 min after high-power melting, then adding pure Mg into a melt, fully stirring with high power to completely dissolve the Mg, preserving heat for 5min, adding solute element Ni if needed, avoiding that Ni sinks into the bottom, intermittently stirring with high power, controlling the temperature to be 830 ℃, and preserving heat for 10 min; continuously cooling the melt to 740 ℃, slagging off, and adding a refining agent for degassing and refining; then, when the temperature of the melt is reduced to about 720 ℃, adding Al-5 wt% Ti-1 wt% B grain refiner, properly stirring, and finally, preserving the temperature for 10min and casting the melt into a steel mould with water cooling at the periphery; then carrying out two-stage homogenization treatment on the mixture, wherein the treatment process comprises the following steps: heating to 485 ℃ at the speed of 30 ℃/h, preserving heat for 3h, continuing heating to 555 ℃ at the speed of 30 ℃/h, preserving heat for 30h, and then cooling to 100 ℃ along with the furnace at the cooling speed of 30 ℃/h, and taking out a sample; after homogenization, cutting the head and milling the cast ingot, reheating to 490-560 ℃ for hot rolling, wherein the pass reduction is 4% -30%, the total deformation of hot rolling is 70-96%, and the final rolling temperature is lower than 300 ℃ to obtain a hot rolled plate, and performing unidirectional rolling; then carrying out cold rolling deformation on the steel plate (the deformation is 35-55%, and the pass reduction is 10-35%); then, carrying out intermediate annealing on the cold-rolled sheet, raising the temperature to 390-410 ℃ at a temperature rise rate of 20-200 ℃/min, carrying out annealing treatment for 0.5-2 h, and then directly taking out for air cooling; then carrying out secondary cold rolling on the steel plate, wherein the deformation is 35-55%, and the pass reduction is 10-35%; then directly cutting a sample on the cold-rolled sheet, and putting the sample in a thermal treatment furnace at 545-565 ℃ for solid solution treatment for 1-6min, wherein the temperature rise rate of the sample is more than 100 ℃/s; then cooling the alloy sample after the solution treatment from the solution treatment temperature to room temperature at a cooling rate of more than 200 ℃/s; and then transferring the quenched sample into a heat treatment furnace within 1.5min for cooling and pre-aging treatment (the temperature is lower than 100 ℃, the time is longer than 10h, and the cooling rate is 2-4 ℃/h), and finally, carrying out bending performance measurement on the pre-aged alloy plate along the rolling direction (r/t is 0.5). The SEM microstructure of the as-cast # 1 alloy is shown in FIG. 2, and the pre-aged crimp properties are shown in FIG. 3.

Example 1

The alloy 1# is prepared by adopting the following intermediate frequency induction melting and casting modes, firstly, common aluminum is melted, the temperature is controlled to be 780-840 ℃, then intermediate alloys such as Al-20wt% of Fe, Al-10wt% of Mn, Al-10wt% of Cr and Al-10wt% of Ti are respectively added, after the intermediate alloys are melted, Al-50wt% of Cu, Al-20wt% of Si and the like are respectively added, then the melt is stirred for 5min at high power, the temperature is controlled to be higher than 720 ℃, then pure Zn and pure Mg are respectively added, during the addition, the intermediate frequency induction furnace power is regulated to enable the temperature of the alloy melt to be stabilized again at 720 ℃, and the next ultrasonic physical field treatment is prepared. When the temperature of the melt is 720 ℃, the alloy melt is treated by an ultrasonic physical field in a cooling process (the power of an ultrasonic generator is 1.5-2 kW, the frequency is 20-22 kHz, the time is 5-30 min, the ultrasonic rod and the surface of the melt are inserted in a way of 70-90 degrees), then the melt after ultrasonic treatment is directly poured into a forming die (the cooling rate is 20-300 ℃/s) → hot rolling (the start rolling temperature is 480-505 ℃, the finish rolling temperature is more than 300 ℃ and the rolling deformation is 52-73 percent), the deformation way is unidirectional rolling) → two-stage heat treatment regulation and control of an alloy structure and a primary iron-rich phase (the first stage is 470-485 ℃/1.5-3 h, the second stage is 530-565 ℃/7-18 h, the temperature rise and fall rate is 10-30 ℃/h) → cold rolling (the deformation is 35-55 percent, the deformation temperature is room temperature, and the unidirectional rolling and intermediate annealing (the annealing temperature is 390-410 ℃/0.5h-2h) + cold rolling deformation rate) + Quantity: 35-55%, deformation temperature: room temperature, mode: unidirectional rolling) → high-temperature short-time solution treatment (545-565 ℃/1-6min, the temperature rise rate is more than 100 ℃/s), then cooling the alloy sample after the solution treatment from the solution treatment temperature to room temperature at the temperature drop rate of more than 200 ℃/s → transferring the quenched sample into an aging furnace within 1.5min for temperature reduction pre-aging treatment (treatment temperature: below 85 ℃, time: and (3) 11-14 h, the cooling rate is 3-3.6 ℃/h), and finally, the bending performance of the pre-aged alloy plate is measured along the rolling direction (r/t is 0.5). The pre-aged crimp behavior is shown in FIG. 4.

Example 2

The alloy 1# is prepared by adopting the following intermediate frequency induction melting and casting modes, firstly, common aluminum is melted, the temperature is controlled to be 780-840 ℃, then respectively adding Al-20wt% of Fe, Al-10wt% of Mn, Al-10wt% of Cr and Al-10wt% of Ti intermediate alloy, respectively adding Al-50wt% of Cu and Al-20wt% of Si intermediate alloy after melting, and then stirring the melt for 5min at high power, (if Ni element is required to be added, adding pure Ni into the melt at the same time at the temperature, stirring the melt for 10min by using the power), then controlling the temperature to be above 720 ℃, then respectively adding pure Zn and pure Mg, respectively pressing the pure Ni into the bottom of the melt by using a graphite bell jar during the addition, taking out the bell jar after the pure Ni is completely dissolved, and regulating and controlling the power of a medium-frequency induction furnace to ensure that the temperature of the alloy melt is stabilized at 720 ℃ again to prepare the next ultrasonic physical field treatment. When the temperature of the melt is 720 ℃, carrying out repeated cooperative treatment on the alloy melt in stages for 2 times by using a temperature field and an ultrasonic physical field (the power of the ultrasonic generator is 1.5-2 kW, the frequency is 20-22 kHz, the time is 5-30 min, the insertion mode is that an ultrasonic rod and the surface of the melt form 70-90 DEG, the melt cooling rate is 3-10 ℃/min, the first stage is controlled to be above 700 ℃, the second stage is controlled to be above 680 ℃, the interval time between the first stage and the second stage is 3-10 min), then directly pouring the melt treated by the composite physical field into a forming die (the cooling rate is 20-300 ℃/s) → hot rolling (the initial rolling temperature is 480-505 ℃, the final rolling temperature is above 300 ℃, the rolling deformation is 52-73%, the deformation mode is unidirectional rolling) → two-stage heat treatment to regulate and control the alloy tissue and the primary iron-rich phase (the first stage is 470-485 ℃/1.5-3 h, the second stage is as follows: 530-565 ℃/7-18 h, a heating rate of 10-30 ℃/h, a cooling rate of more than 50 ℃/h) → large-deformation cold rolling (deformation: 70-93%, deformation temperature: room temperature) → high temperature short time solution treatment (545- & gt565 ℃/1-6min, the temperature rise rate is more than 100 ℃/s), then cooling the alloy sample after solution treatment from the solution treatment temperature to room temperature at the temperature drop rate of more than 200 ℃/s → transferring the quenched sample into an aging furnace within 1.5min for temperature reduction pre-aging treatment (treatment temperature: below 85 ℃, time: and (3) 11-14 h, the cooling rate is 3-3.6 ℃/h), and finally, the bending performance of the pre-aged alloy plate is measured along the rolling direction (r/t is 0.5). Finally, SEM structure observation and crimp performance measurement of the pre-aged alloy are shown in FIG. 5.

Example 3

The alloy 2# is prepared by adopting the following intermediate frequency induction melting and casting modes, firstly, melting common aluminum, controlling the temperature to be 780-840 ℃, then respectively adding Al-20wt% of Fe, Al-10wt% of Mn, Al-10wt% of Cr and Al-10wt% of Ti intermediate alloy, respectively adding Al-50wt% of Cu and Al-20wt% of Si intermediate alloy after melting, simultaneously adding pure Ni into the melt at the temperature, stirring the melt for 10min by using power, then controlling the temperature to be above 720 ℃, respectively adding pure Zn and pure Mg, respectively pressing the pure Ni and the pure Mg into the bottom of the melt by using a graphite bell jar during adding, taking out the bell jar after the pure Ni is completely melted, and regulating and controlling the power of an intermediate frequency induction furnace to enable the temperature of the alloy melt to be stabilized at 720 ℃ again for next ultrasonic physical field treatment. When the temperature of the melt is 720 ℃, carrying out repeated cooperative treatment on the alloy melt in stages for 2 times by using a temperature field and an ultrasonic physical field (the power of the ultrasonic generator is 1.5-2 kW, the frequency is 20-22 kHz, the time is 5-30 min, the insertion mode is that an ultrasonic rod and the surface of the melt form 70-90 DEG, the melt cooling rate is 3-10 ℃/min, the first stage is controlled to be above 700 ℃, the second stage is controlled to be above 680 ℃, the interval time between the first stage and the second stage is 3-10 min), then directly pouring the melt treated by the composite physical field into a forming die (the cooling rate is 20-300 ℃/s) → hot rolling (the initial rolling temperature is 480-505 ℃, the final rolling temperature is above 300 ℃, the rolling deformation is 52-73%, the deformation mode is unidirectional rolling) → two-stage heat treatment to regulate and control the alloy tissue and the primary iron-rich phase (the first stage is 470-485 ℃/1.5-3 h, the second stage is as follows: 530-565 ℃/7-18 h, a heating rate of 10-30 ℃/h, a cooling rate of more than 50 ℃/h) → large-deformation cold rolling (deformation: 70-93%, deformation temperature: room temperature) → high-temperature short-time solution treatment (545-565 ℃/1-6min, the temperature rise rate is more than 100 ℃/s), then cooling the alloy sample after the solution treatment from the solution treatment temperature to the room temperature at the temperature drop rate of more than 200 ℃/s → transferring the quenched sample into an aging furnace within 1.5min for temperature reduction and pre-aging treatment (treatment temperature: below 85 ℃, time: and (3) 11-14 h, the cooling rate is 3-3.6 ℃/h), and finally, the bending performance of the pre-aged alloy plate is measured along the rolling direction (r/t is 0.5). The nano-dispersed particles in the matrix after the two-stage homogenization treatment are shown in fig. 6. The pre-aged SEM texture and the crimp performance are shown in figure 7.

With the acceleration of the process of automobile light weight, the development of novel aluminum alloy for automobile body outer panels has also been rapidly developed, and various aluminum alloy materials with excellent comprehensive properties and preparation methods thereof have been developed on the basis of the conventional Al-Mg-Si-Cu alloy, wherein the Al-Mg-Si-Cu-Zn alloy added with solute element Zn not only has excellent baking varnish hardening increment, but also has excellent stamping forming properties, and the alloy has attracted extensive attention and research. However, in order to further reduce the production cost of the series of alloys, it is necessary to melt and cast the series of alloys by fully utilizing recycled aluminum. However, the recovered aluminum generally contains impurity element Fe, which is easily to generate dendritic, rod-like or coarse granular iron-rich phases in the as-cast alloy, such as the as-cast structure of the alloy prepared in comparative example 1 (as shown in FIG. 2), and these phases can be broken in the subsequent hot working process, but coarse iron-rich phase particles which are not broken completely are inevitably distributed in the final alloy matrix, and micro cracks remain in the interior of the matrix. These coarse iron-rich phase particles, which are not broken thoroughly, adversely affect the plasticity, formability, etc. of the alloy. Based on the quality of the external surface after crimping and the SEM texture analysis after cracking (as shown in fig. 3) of the pre-aged alloy prepared in comparative example 1, it can be readily seen that the segregation of the original iron-rich phase in the as-cast alloy matrix does have a severe deteriorating effect on the crimping performance of the alloy. Therefore, it is necessary to control nucleation, growth, distribution and the like of the primary iron-rich phase in the alloy matrix from the casting source, and then the adverse effect of the coarse primary iron-rich phase can be completely eliminated by the control of the subsequent hot working process. Therefore, the invention provides a process regulation and control method for effectively avoiding the segregation of the primary iron-rich phase by utilizing the synergistic effect of the temperature field and the ultrasonic physical field, and simultaneously, the subsequent hot working process regulation and control are fully utilized to further optimize and control the size, the form, the distribution and the like of the synthesized primary iron-rich phase particles, so that the method can generate positive influence on the evolution of the alloy structure, and the edge bending performance of the pre-aged alloy can be greatly improved.

According to the results of example 1, it can be found that if a temperature field and an ultrasonic physical field are introduced during the casting process, the iron-rich phase in the 1# alloy matrix can be controlled to a certain extent, and then the iron-rich phase in the alloy matrix is controlled to be uniformly dispersed and distributed (as shown in the (a) area in fig. 4) after the integrated process control treatment of hot rolling → homogenization → cold rolling + intermediate annealing + cold rolling deformation → solution quenching → preaging), but because the process parameters of the temperature field + the ultrasonic physical field and the control of the hot working process are not reasonable enough, the alloy structure does not obtain the best matching, such as the control of grain size, shape, orientation, and distribution of precipitation phase, and the like, the edge bending performance of the preaging alloy plate processed by the processing route of this embodiment is not improved, but is reduced to a certain extent, some cracking occurs after the alloy in the pre-aged state has been deformed by the crimp (as shown in the area (b) of fig. 4). Therefore, in order to greatly improve the bending performance of the alloy plate, the comprehensive regulation and control of the primary iron-rich phase and the alloy structure are very important, and after the primary iron-rich phase is well regulated and controlled, the bending performance can be greatly improved by being assisted with the integrated regulation and control of a proper hot working process.

Based on the above results and the process control of the primary nucleation and growth in the casting process by using a large number of temperature fields and ultrasonic physical fields, and the optimization of the parameters in the subsequent thermal processing process, it is finally found that the pre-aged alloy sheet material prepared by implementing alloy # 1 and using the method described in example 2 not only can obtain effective control of the primary phase size, morphology and distribution (as shown in (a) area in fig. 5), but also can obtain effective control of the grain size, orientation and the like after being controlled by the thermal processing process, and the pre-aged alloy sheet material shows excellent edge bending performance, and has a smooth and crack-free surface after edge bending (as shown in (b) area in fig. 5). Therefore, the control of the original phase in the alloy matrix is very important for improving the flanging performance of the alloy, but the grain size, orientation, form, distribution and the like of the alloy are also important, so that the pre-aged aluminum alloy plate can show excellent flanging performance only by carrying out reasonable integrated process control. In addition, since the size, morphology, distribution, and the like of the primary iron-rich phase are closely related to the nucleation process, it is considered that solute elements Ni and Fe have strong forces, and the melting point of Ni element is high. Therefore, if a certain amount of solute element Ni can be introduced into the alloy matrix, the nucleation stability of the primary iron-rich phase is improved to a certain extent, so that more primary iron-rich phase nuclei can be formed in the casting process, particularly in the casting and cooling process, and the same temperature field and physical field in the embodiment 2 are adopted to cooperate with each other to act on the solidification process of the alloy, so that the number density of nano dispersed particles in the alloy matrix is improved to a certain extent, and the evolution of an alloy structure is more actively acted in the subsequent hot working process. FIG. 6 shows the distribution of nano-dispersed particles in the matrix after the alloy is subjected to temperature field + ultrasonic physical field regulation, hot rolling and double-stage homogenization treatment. As can be seen, the nano-dispersed particles are not only significantly increased in number, uniform and fine in size, but also very uniform in distribution, as originally expected in the tissue characteristics. The alloy sheet was then subjected to further hot working and SEM observations and crimp performance measurements were made on the pre-aged alloy sheet (as shown in figure 7). It can be seen from the figure that, after the alloy is regulated by the temperature + ultrasonic composite physical field and the subsequent thermal processing process, a large number of uniformly dispersed nano particles (as shown in fig. 6) are distributed in the matrix, and the coarse particles are effectively regulated and distributed in the alloy matrix in a relatively uniform and dispersed manner. Furthermore, the solute element Ni-added No. 2 alloy contained more dispersed particles than the pre-aged SEM structure of the No. 1 alloy of example 2, mainly due to the fact that the solute element Ni can react with Fe to form a Ni-containing primary iron-rich phase. Meanwhile, after the 2# alloy is integrally regulated and controlled by the temperature field, the ultrasonic physical field and the hot working, the alloy can also show excellent bending performance (as shown in (b) in fig. 7), which has important significance for the practical application of the alloy.

In conclusion, after the temperature and ultrasonic composite physical field regulation and control of nucleation, growth and distribution of the primary iron-rich phase in the Al-Mg-Si-Cu-Zn alloy casting process, dendritic, rod-like and coarse primary iron-rich phases observed in the traditional casting process are well inhibited, and then the subsequent thermal processing integrated process regulation and control are carried out, so that not only can the primary iron-rich phase of the alloy be uniformly dispersed and distributed in an alloy matrix, but also the size of the primary iron-rich phase of the alloy can be in multi-scale distribution; and more importantly, under the positive influence of the multi-scale primary iron-rich phase, after the alloy plate is regulated and controlled in the hot working process, the grain size, the form, the orientation and the distribution of the alloy plate can be well regulated and controlled, and finally, the pre-aged alloy plate can show excellent flanging performance. This is very important for the subsequent practical application of the series of alloy sheets. In addition, once the primary iron-rich phase can be well regulated and controlled, the system alloy can be completely smelted by adopting recycled aluminum alloy or common aluminum with lower purity, which is very beneficial to reducing the production cost of the system alloy and has a positive effect on accelerating the wide application of the system alloy. Therefore, the treatment process is not only suitable for being widely applied to manufacturing of Al-Mg-Si-Cu-Zn alloy plates for automobiles, so that the process of aluminum alloy for light weight of automobiles is accelerated, but also has certain guiding significance on development, processing and application of high-formability and high-strength aluminum alloy in other fields, and is worthy of being paid attention to the invention by automobile manufacturers and aluminum alloy processing enterprises, so that the treatment process can be popularized and applied in the field as soon as possible.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (9)

1. The integrated process control method for improving the automobile aluminum alloy plate flanging performance is characterized in that the automobile aluminum alloy is an Al-Mg-Si-Cu-Zn alloy, and the Al-Mg-Si-Cu-Zn alloy comprises the following chemical components in percentage by mass: 0.5-3.7 wt% of Zn, Mg: 0.6-1.0 wt%, Si: 0.4 to 1.0wt%, Cu: 0.1 to 0.4wt%, 0.1 to 0.7wt% of Fe, Mn: 0.3-0.7 wt%, Ni is less than or equal to 0.12wt%, Cr is less than 0.02wt%, Ti is less than or equal to 0.1wt%, B is less than 0.01wt%, and the balance is Al, wherein the method specifically comprises the following steps:

(1) preparing Al-Mg-Si-Cu-Zn alloy for the automobile by adopting recycled aluminum or common aluminum;

(2) performing medium-frequency induction melting, and cooling the alloy melt from 780 ℃ to 720 ℃ after the melting is finished;

(3) carrying out stage-by-stage 2-time repeated synergistic treatment on the alloy melt in the cooling process by adopting a temperature field and an ultrasonic physical field: power of the ultrasonic generator: 0.8-2 kW, frequency: 19-22 kHz, time: 5-30 min, insertion mode: the ultrasonic rod and the surface of the melt are 45-90 degrees, and the cooling rate of the melt is as follows: 3-12 ℃/min, controlling the temperature of the melt to be more than 690 ℃ in the first stage, controlling the temperature of the melt to be more than 670 ℃ in the second stage, and separating the interval time between the first stage and the second stage for 2-15 min;

(4) pouring the alloy melt processed in the step (3) into a forming die and cooling, wherein the cooling rate is as follows: 20-300 ℃/s;

(5) and (3) hot rolling process treatment: the initial rolling temperature is 480-510 ℃; the finishing temperature is above 300 ℃, the rolling deformation is 50-75%, and the deformation mode is as follows: unidirectional rolling;

(6) the double-stage heat treatment regulates and controls the size and distribution state of alloy structure and primary iron-rich phase: the first stage is 440-485 ℃/1-3 h, the second stage is 520-575 ℃/7-20 h, the temperature rise rate is 10-30 ℃/h, and the temperature reduction rate is 46-200 ℃/h;

(7) and (3) large-deformation cold rolling treatment: cold rolling deformation of 40-95% and deformation temperature of room temperature;

(8) high-temperature short-time solution treatment: 540-;

(9) transferring the quenched sample into an aging furnace within 1.5min for cooling and pre-aging treatment, wherein the temperature is lower than 100 ℃, the time is longer than 10h, and the cooling rate is 2-4 ℃/h.

2. The integrated process control method for improving the flanging performance of the aluminum alloy plate for the automobile according to claim 1, wherein the medium-frequency induction melting process comprises the following steps: firstly, melting recovered aluminum or common aluminum, controlling the temperature to be 780-840 ℃, then respectively adding Al-20wt% of Fe, Al-10wt% of Mn, Al-10wt% of Cr and Al-10wt% of Ti intermediate alloy, respectively adding Al-50wt% of Cu and Al-20wt% of Si intermediate alloy after melting, then stirring the melt for 5min at high power, if needing to add Ni element, simultaneously adding pure Ni into the melt at the temperature, stirring the melt for 10min by utilizing the high power, then controlling the temperature to be above 720 ℃, then respectively adding pure Zn and pure Mg, respectively pressing the melt into the bottom of the melt by using a graphite bell jar during adding, taking out the bell jar after the melt is completely melted, and regulating and controlling the power of a medium-frequency induction furnace to enable the temperature of the alloy melt to be stabilized again at 720 ℃ for preparing the next temperature field and ultrasonic physical field treatment.

3. The integrated process control method for improving the flanging performance of the aluminum alloy plate for the automobile according to claim 1, characterized in that the temperature field and the ultrasonic physical field perform stage-by-stage 2 times of repeated cooperative treatment on the alloy melt cooling process: the power of the ultrasonic generator is 1.5-2 kW, the frequency is 20-22 kHz, the time is 5-25 min, and the insertion mode is as follows: the ultrasonic rod and the surface of the melt are 70-90 degrees, and the cooling rate of the melt is as follows: 3-10 ℃/min, controlling the temperature of the melt to be more than 700 ℃ in the first stage, controlling the temperature of the melt to be more than 680 ℃ in the second stage, and separating the interval time between the first stage and the second stage for 3-10 min.

4. The integrated process control method for improving the flanging performance of the aluminum alloy plate for the automobile according to claim 1, wherein the hot rolling process comprises the following specific treatment processes: the initial rolling temperature is 480-505 ℃; the finishing temperature is above 300 ℃, the rolling deformation is 52-73%, and the deformation mode is as follows: and (4) unidirectional rolling.

5. The integrated process control method for improving the flanging performance of the aluminum alloy plate for the automobile according to claim 1, wherein the specific process of the two-stage high-temperature heat treatment process is as follows: the first stage is 470-485 ℃/1.5-3 h, the second stage is 530-565 ℃/7-18 h, the heating rate is 10-30 ℃/h, and the cooling rate is 50-200 ℃/h.

6. The integrated process control method for improving the automobile aluminum alloy plate flanging performance according to claim 1, characterized in that the large-deformation cold rolling process specifically comprises the following steps: the cold rolling deformation is 70-93%, and the deformation temperature is room temperature.

7. The integrated process control method for improving the flanging performance of the aluminum alloy plate for the automobile as recited in claim 1, wherein the specific high-temperature short-time solution treatment process comprises the following steps: 545-565 ℃/1-6min, the heating rate is more than 100 ℃/s, and then the alloy sample after solution treatment is cooled to the room temperature from the solution treatment temperature at the cooling rate of more than 200 ℃/s.

8. The integrated process control method for improving the flanging performance of the aluminum alloy plate for the automobile according to claim 1, wherein the cooling pre-aging treatment process specifically comprises the following steps: transferring the quenched sample into an aging furnace within 1.5min for cooling pre-aging treatment, wherein the treatment temperature is lower than 85 ℃, the time is 11-14 h, and the cooling rate is 3-3.6 ℃/h.

9. An aluminum alloy sheet for an automobile, characterized in that the aluminum alloy sheet for an automobile is an Al-Mg-Si-Cu-Zn alloy sheet, the Al-Mg-Si-Cu-Zn alloy sheet is prepared and regulated by the integrated process regulation and control method according to any one of claims 1 to 8,

the Al-Mg-Si-Cu-Zn alloy comprises the following chemical components in percentage by mass: 0.5-3.7 wt% of Zn, Mg: 0.6-1.0 wt%, Si: 0.4 to 1.0wt%, Cu: 0.1 to 0.4wt%, 0.1 to 0.7wt% of Fe, Mn: 0.3-0.7 wt%, Ni less than or equal to 0.12wt%, Cr less than 0.02wt%, Ti less than or equal to 0.1wt%, B less than 0.01wt%, and the balance of Al.

Images