阅读说明：本技术 一种再生变形铝合金熔体的复合处理方法 (Composite treatment method for regenerated wrought aluminum alloy melt ) 是由 何健松 杜军 史明波 周炳坚 何杏霖 于 2020-03-18 设计创作，主要内容包括：本发明公开了一种再生变形铝合金熔体的复合处理方法,所述复合处理方法主要是通过Mg、Sr和含C细化剂对6xxx系再生铝合金熔体进行复合处理,改变合金第二相形态和分布,使得针状杂质相转变为汉字状,共晶组织均匀分布,同时细化晶粒,改变合金凝固方式。经本发明复合处理后,再生变形铝合金的铸锭热裂敏感性显著降低,降低率高达32％,综合力学性能也显著提升,抗拉强度最高提升35％,硬度最高提升45％。(The invention discloses a composite treatment method of a regenerated wrought aluminum alloy melt, which is mainly characterized in that a 6xxx series regenerated aluminum alloy melt is subjected to composite treatment through Mg, Sr and a C-containing refiner, the shape and distribution of a second phase of an alloy are changed, needle-shaped impurity phases are changed into Chinese characters, eutectic structures are uniformly distributed, crystal grains are refined, and the solidification mode of the alloy is changed. After the composite treatment of the invention, the ingot casting hot cracking sensitivity of the regenerated wrought aluminum alloy is obviously reduced, the reduction rate is up to 32 percent, the comprehensive mechanical property is also obviously improved, the tensile strength is improved by 35 percent to the maximum, and the hardness is improved by 45 percent to the maximum.)

1. The composite treatment method of the regenerated wrought aluminum alloy melt is characterized by comprising the following steps of:

(1) melting 6xxx series waste aluminum, and obtaining a regenerated wrought aluminum alloy melt after slagging-off;

(2) adding a metal Mg, an Al-Ti series refiner and an Al-10Sr alterant into the melt obtained in the step (1) for composite treatment, uniformly stirring after melting, and standing at a constant temperature;

(3) refining and deslagging the melt obtained in the step (2), and preserving heat and standing after deslagging;

(4) casting and molding the melt obtained in the step (3) to obtain a regenerated wrought aluminum alloy ingot;

(5) carrying out homogenization heat treatment on the aluminum alloy ingot obtained in the step (4) to obtain a cast plate;

(6) and (5) rolling the cast plate obtained in the step (5) for multiple times to obtain the regenerated wrought aluminum alloy.

2. The composite treatment method for the renewable wrought aluminum alloy melt according to claim 1, wherein in the step (2), the Al-Ti series refiner is added in an amount of 0.3-0.7% by mass of the melt, the Al-10Sr modifier is added in an amount of 0.2-0.6% by mass of the melt, and the Mg content in the melt after the metal Mg is added is 0.8-1.4% by mass.

3. The composite treatment method of a wrought aluminum alloy melt according to claim 1, wherein the Al-Ti series refiner comprises at least one of a C-containing refiner and an Al-5Ti-B refiner; preferably, the Al-Ti series refiner is a C-containing refiner.

4. The method for compositely treating a wrought aluminum alloy melt according to claim 3, wherein the C-containing refiner comprises the following components in mass fraction: 4.5 to 5.5 percent of Ti, 0.25 to 0.35 percent of B and 0.15 to 0.25 percent of C.

5. The composite treatment method of the renewable wrought aluminum alloy melt as claimed in claim 1, wherein in the step (2), the temperature of the composite treatment is 720-750 ℃, and the time of heat preservation and standing is 10-20 min.

6. The composite treatment method of the renewable wrought aluminum alloy melt as claimed in claim 1, wherein in the step (3), the refining deslagging treatment is to add a refining agent and a deslagging agent into the melt, the treatment temperature is controlled to be 720-750 ℃, and the treatment time is 10-20 min; preferably, the refining agent and the slag former are added by blowing.

7. The composite treatment method of the wrought aluminum alloy melt as recited in claim 6, wherein in the step (3), the total addition amount of the refining agent and the slag striking agent is 1% of the melt mass, and the mass ratio of the refining agent to the slag striking agent is 1: 4.

8. the composite treatment method of the wrought aluminum alloy melt of claim 1, wherein in step (5), the homogenizing heat treatment process comprises: the temperature is 480-500 ℃, and the heat preservation time is 8-12 h.

9. The method for producing a wrought aluminum alloy according to claim 1, wherein in step (6), the rolling process comprises: the maximum deformation of each pass is 10 percent, and the total deformation is 50 percent.

10. A 6 xxx-series wrought aluminum alloy produced by a composite treatment method of the wrought aluminum alloy melt of any of claims 1-9.

Technical Field

The invention relates to the technical field of composite treatment of regenerated wrought aluminum alloy melts, in particular to a composite treatment method capable of reducing the heat cracking sensitivity of a 6xxx series regenerated wrought aluminum alloy cast ingot and improving the comprehensive mechanical property of the cast ingot.

Background

Aluminum and aluminum alloy have the characteristics of small specific gravity, good conductivity, good heat dissipation performance, high specific strength, easiness in processing and the like, are increasingly applied to the fields of automobiles, traffic, aviation and the like, and become indispensable basic raw materials of national economy. On one hand, the demand of the high-speed development of national economy on aluminum products is continuously increased, and on the other hand, the large-batch aluminum products reach the service life each year, so that a large amount of waste aluminum resources are enriched, and the rapid development of the secondary aluminum industry is promoted. In addition, the regenerated metal has the characteristic of energy conservation, and the unit energy consumption of the production of the regenerated aluminum is not more than 5 percent of that of the production of electrolytic aluminum. The development of the secondary aluminum industry has important significance for realizing the strategy of green economy and sustainable development.

The secondary aluminum is aluminum alloy or aluminum metal obtained by remelting and refining various recovered waste aluminum serving as raw materials, and is an important source for obtaining metal aluminum. The waste aluminum has various types and different components, so that the components of the regenerated aluminum are very complex, main impurities comprise Zn, Fe, Cu, Mn and the like, and the existence of the impurity elements reduces the performance of the regenerated aluminum alloy, so that the degraded use of the aluminum alloy is caused. Particularly, in the casting and forming process of the regenerated aluminum alloy, the existence of the impurity elements obviously increases the heat crack sensitivity of the aluminum alloy cast ingot, reduces the yield and causes the waste of resources.

The patent (CN102127665B) adopts high Zn and Mg contents, and the Sc and Zr composite micro-alloying treatment realizes the purposes of increasing the proportion of eutectic phases, inhibiting dendritic crystal growth and changing the solidification mode of the alloy, thereby reducing the hot cracking sensitivity of the alloy and improving the casting performance of the alloy.

Currently, research on the hot cracking tendency of aluminum alloys is mainly focused on mature commercial alloys, and relatively few hot cracking tendency of scrap-based secondary aluminum alloys is focused. The 6xxx series wrought aluminum alloy represented by 6061 is one of the aluminum alloys with the largest market share at present, is mainly applied to the civil field, and has large recovery amount which exceeds 300 million tons per year. After remelting and recycling, the components are complex, so that the casting production process has a great hot cracking tendency, the process yield is reduced, and the performance is obviously reduced. Therefore, for regenerated 6xxx series wrought aluminum alloy with complex components, how to utilize a melt composite treatment method reduces the heat cracking sensitivity of the alloy in the casting process, and simultaneously gives consideration to excellent comprehensive performance, thereby having important significance for practical application of the regenerated aluminum.

Disclosure of Invention

In order to solve the defects and shortcomings in the prior art, the invention aims to provide a composite treatment method for a regenerated wrought aluminum alloy melt. The regenerated wrought aluminum alloy treated by the method has small hot cracking sensitivity in the casting process, high casting blank yield, excellent comprehensive mechanical property and wide application range.

In order to achieve the purpose, the technical scheme adopted by the invention comprises the following aspects:

a composite treatment method for a regenerated wrought aluminum alloy melt comprises the following steps:

(1) melting 6xxx series waste aluminum, and obtaining a regenerated wrought aluminum alloy melt after slagging-off;

(2) adding a metal Mg, an Al-Ti series refiner and an Al-10Sr alterant into the melt obtained in the step (1) for composite treatment, uniformly stirring after melting, and standing at a constant temperature;

(3) refining and deslagging the melt obtained in the step (2), and preserving heat and standing after deslagging;

(4) casting and molding the melt obtained in the step (3) to obtain a regenerated wrought aluminum alloy ingot;

(5) carrying out homogenization heat treatment on the aluminum alloy ingot obtained in the step (4) to obtain a cast plate;

(6) and (5) rolling the cast plate obtained in the step (5) for multiple times to obtain the regenerated wrought aluminum alloy.

Preferably, in the step (1), the melting temperature of the 6xxx series aluminum scrap is 750 ℃.

Preferably, in the step (2), the addition amount of the Al-Ti series refiner accounts for 0.3-0.7% of the mass of the melt, and the addition amount of the Al-10Sr alterant accounts for 0.2-0.6% of the mass of the melt.

Preferably, the Al-Ti series refiner includes at least one of a C-containing refiner and an Al-5Ti-B refiner. More preferably, the Al-Ti series refiner is a C-containing refiner. The C-containing refiner comprises the following components in percentage by mass: 4.5 to 5.5 percent of Ti, 0.25 to 0.35 percent of B and 0.15 to 0.25 percent of C.

Preferably, after the metal Mg is added, the mass percentage of Mg in the melt is 0.8-1.4%.

Preferably, in the step (2), the temperature of the composite treatment is 720-750 ℃, and the time of heat preservation and standing is 10-20 min.

Preferably, in the step (3), the refining and deslagging treatment is to add a refining agent and a deslagging agent into the melt, the treatment temperature is controlled to be 720-750 ℃, and the treatment time is 10-20 min.

Preferably, the total adding amount of the refining agent and the slag removing agent is 1% of the mass of the melt, and the mass ratio of the refining agent to the slag removing agent is 1: 4.

preferably, the refining agent and the slag former are uniformly mixed and then added into the melt by a blowing method.

Preferably, the commercial brands of the refining agent and the slagging agent are the refining agent YT-J-1 and the slagging agent YT-D-4 respectively.

Preferably, in the step (3), the heat preservation and standing time is 30 min.

Preferably, in the step (4), the casting and forming manner is gravity casting and forming.

Preferably, in the step (5), the homogenizing heat treatment process comprises: the temperature is 480-500 ℃, and the heat preservation time is 8-12 h.

Preferably, in step (6), the rolling process is as follows: the maximum deformation of each pass is 10 percent, and the total deformation is 50 percent.

The invention also provides a 6xxx series regenerative wrought aluminum alloy prepared by the composite treatment method of the regenerative wrought aluminum alloy melt.

Because the raw material source of the 6xxx series regenerated wrought aluminum alloy is complex, the 6xxx series regenerated wrought aluminum alloy contains a plurality of impurity elements such as Fe, Cu, Mn, Zn and the like, and the content is high, such as Fe: 0.95%, Cu: 0.45 percent. The impurity elements are easy to form coarse and brittle iron-copper-rich impurity phases and other low-melting-point phases in the alloy, so that the continuity of a matrix is damaged, the solidification interval of the alloy is increased, the hot cracking sensitivity of the alloy is increased, the mechanical property is reduced, and the alloy can only be degraded for use. In the treatment method, the purification treatment of the regenerated wrought aluminum alloy melt can effectively reduce air holes and oxide slag inclusion and reduce crack sources. Meanwhile, under the action of Sr alterant and C-containing refiner, the broken long-needle-shaped iron-rich phase in the alloy is converted into Chinese character shape and is combined with the matrix more tightly, the crystal grains are further refined, and the thermal stress resistance is enhanced. Mg is an important alloy element in 6xxx series aluminum alloy, Mg is added for component regulation and control, and Mg is generated at the final stage of alloy solidification₂Si eutectic phase can be well fed, the generation of hot cracks is prevented, and Mg₂Si is the main hard strengthening phase of the 6xxx series aluminum alloy and can be promotedHardness and mechanical properties. Therefore, compared with single modification treatment, the composite treatment of the invention on the melt can effectively reduce the hot cracking sensitivity of the alloy, and simultaneously improve the mechanical property of the alloy, so that the obtained regenerated aluminum alloy can meet the requirements of household and light industrial manufacturing molds, and the like, thereby not only realizing the grade-keeping utilization of the regenerated and deformed aluminum alloy, but also expanding the application range and field of the regenerated and deformed aluminum alloy.

Compared with the prior art, the invention has the beneficial effects that: according to the invention, the composite treatment of Mg, Sr alterant and C-containing refiner is carried out on the 6xxx series regenerative wrought aluminum alloy melt, so that the multielement composite effect is fully exerted, the form and distribution of the second phase in the regenerative wrought aluminum alloy are improved, the iron-rich impurity phase is changed into a Chinese character shape from a needle shape, the eutectic phase is uniformly distributed, the grain structure is refined, and the alloy solidification mode is changed; the invention also purifies the melt, further reduces crack sources in the alloy, finally performs homogenization and rolling deformation control, finally obtains the 6xxx series regenerated wrought aluminum alloy with small casting hot cracking sensitivity, excellent comprehensive mechanical property and high casting yield, and widens the industrial application of the 6xxx series regenerated wrought aluminum alloy.

Drawings

FIG. 1 is an as-cast optical microstructure of a virgin wrought aluminum alloy prepared in comparative example 1;

FIG. 2 is an as-cast optical microstructure of a wrought aluminum alloy prepared in comparative example 2;

FIG. 3 is an as-cast optical microstructure of a wrought aluminum alloy prepared in comparative example 3;

FIG. 4 is an as-cast optical microstructure of a wrought aluminum alloy prepared in comparative example 4;

FIG. 5 is an as-cast optical microstructure of a wrought aluminum alloy prepared in example 1;

FIG. 6 is a CRC restraint bar hot crack test sample of a virgin wrought aluminum alloy prepared in comparative example 1;

FIG. 7 is a CRC restraint bar hot crack test sample of the wrought aluminum alloy prepared in example 1.

FIG. 8 is a comparison of the hot crack sensitivity of the regenerated wrought aluminum alloy ingots made in the examples and comparative examples.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention is further illustrated by the following examples. It is apparent that the following examples are only a part of the embodiments of the present invention, and not all of them. It should be understood that the embodiments of the present invention are only for illustrating the technical effects of the present invention, and are not intended to limit the scope of the present invention.

Comparative example 1

Preparation of original 6xxx series regenerated wrought aluminum alloy: melting the primarily screened 6xxx series recycled aluminum scrap, including 6061, 6063, 6151, 6201 and the like, wherein the melting temperature is 750 ℃, fully melting and stirring until the melt components are uniform, removing dross on the surface of the melt, and keeping the temperature and standing for 20 min. Uniformly mixing a refining agent YT-J-1 and a slag striking agent YT-D-4 according to the mass ratio of 1:4, adding the mixture into a melt by using a nitrogen blowing method, carrying out refining and slag striking treatment on the melt, controlling the treatment temperature to be 720 ℃, treating for 20min, taking the total addition amount of the refining agent and the slag striking agent as 1% of the mass of the melt, removing floating slag on the surface of the melt, and standing for 30min under heat preservation to obtain a regenerated wrought aluminum alloy melt, wherein the regenerated wrought aluminum alloy melt comprises the following components in percentage by mass: si: 0.63%, Fe: 0.95%, Mg: 0.72%, Cu: 0.45%, Mn: 0.12%, Zn: 0.15%, the total amount of other impurities is not more than 0.30%, and the balance is Al. And (3) casting and molding the regenerated wrought aluminum alloy melt by using a gravity casting method to obtain a regenerated wrought aluminum alloy ingot, wherein the preheating temperature of the metal mold is 200 ℃. And placing the cast ingot in a resistance furnace for homogenization heat treatment, wherein the homogenization temperature is 480 ℃, and the heat preservation time is 8 hours. And (3) rolling the ingot subjected to the homogenization heat treatment for multiple times, wherein the deformation amount of each time is 5 percent, and the total deformation amount is 50 percent, so as to obtain the original regeneration deformation aluminum alloy.

In order to compare the structure and performance characteristics of the alloy, the thermal cracking sensitivity of the regenerated aluminum alloy is evaluated by a CRC (constrained RodCast) constraint rod thermal cracking evaluation method; meanwhile, preparing a metallographic specimen for tissue observation; testing the hardness value of the alloy by using a HB3000 Brinell hardness tester; and tensile tests are carried out by using an AG-X100KN universal testing machine to obtain mechanical property parameters.

FIG. 1 is an optical microstructure of the wrought aluminum alloy prepared in comparative example 1, in which it can be seen that the wrought aluminum alloy without the compound treatment has coarse dendrites, eutectic structure phase and impurity phase, and is concentrated and distributed at grain boundaries. As-cast properties were measured, the tensile strength of the alloy was 178.9MPa, the elongation 9.4%, and the hardness 48 HB. FIG. 6 is a thermal cracking test sample of the CRC restraining rod of the alloy, wherein the long arm and the second long arm are completely cracked, the second short arm is partially cracked, and according to the evaluation mode of CRC, the thermal cracking sensitivity coefficient HTS of the alloy is calculated to be 178, and the casting thermal cracking sensitivity is high. The rolling state performance is measured, the tensile strength of the alloy is only 202.2MPa, the elongation is 6.2%, the hardness is 63.9HB, and the comprehensive performance is poor.

Comparative example 2

Preparation of a Mg-treated-alone 6 xxx-series wrought aluminum alloy: the 6xxx series recycled aluminum scrap after primary screening is melted according to the method of the comparative example 1, the initial basic components are the same as the comparative example 1, the scum is removed, and the aluminum scrap is kept warm and kept stand for 20 min. Adding Mg ingots into the melt, keeping the temperature of the melt at 720 ℃, uniformly stirring after melting, and keeping the temperature and standing for 20 min; wherein the addition amount of Mg is 0.55 percent of the mass of the melt, the burning loss rate is 10 percent, and the Mg content mass fraction of the added alloy is 1.2 percent. And casting the melt into an ingot by the method of the comparative example 1, and then placing the ingot in a resistance furnace for homogenization heat treatment, wherein the homogenization temperature is 490 ℃, and the heat preservation time is 10 hours. And (4) carrying out multi-pass rolling after homogenization, wherein the deformation amount of each pass is 5%, and the total deformation amount is 50%, so as to obtain the regenerated wrought aluminum alloy.

FIG. 2 is an as-cast optical microstructure of a wrought aluminum alloy prepared in comparative example 2 and subjected to melt processing with Mg alone, and it can be seen that bulk interconnected eutectic structures appear in the alloy and that eutectic structures and impurity phases are increased at grain boundaries. The hot cracking sensitivity coefficient HTS of the alloy in an as-cast state is 154, the tensile strength of the alloy in the as-cast state is 185.2MPa, the elongation is 9.1 percent, and the hardness is 54.4 HB. In the rolled state, the tensile strength of the alloy was 212.5MPa, the elongation was 7.2%, and the hardness was 75.4 HB.

Comparative example 3

Preparation of Sr-treated 6 xxx-series wrought aluminium alloys: the 6xxx series recycled aluminum scrap after primary screening is melted according to the method of the comparative example 1, the initial basic components are the same as the comparative example 1, the scum is removed, and the aluminum scrap is kept warm and kept stand for 20 min. Adding Al-10Sr alterant into the melt, keeping the melt temperature at 720 ℃, uniformly stirring after melting, and standing for 20min with heat preservation; wherein the addition amount of the Al-10Sr alterant is 0.5 percent of the mass of the melt. And casting the melt into an ingot by the method of the comparative example 1, and then placing the ingot in a resistance furnace for homogenization heat treatment, wherein the homogenization temperature is 480 ℃ and the heat preservation time is 8 hours. And (4) carrying out multi-pass rolling after homogenization, wherein the deformation amount of each pass is 5%, and the total deformation amount is 50%, so as to obtain the regenerated wrought aluminum alloy.

FIG. 3 is an as-cast optical microstructure of the wrought aluminum alloy prepared in comparative example 3 after being subjected to melt treatment with Mg alone, which is similar to the as-cast optical microstructure of the wrought aluminum alloy prepared in comparative example 2 after being subjected to melt treatment with Mg alone, and it can be seen from FIG. 3 that bulk eutectic structures and impurity phases in the alloy disappear and are uniformly distributed around grains. The hot cracking sensitivity coefficient HTS of the alloy in an as-cast state is 164, the tensile strength is 190.2MPa, the elongation is 10.2 percent, and the hardness is 53.7 HB. The tensile strength of the alloy in the rolled state is 217.5MPa, the elongation is 6.9 percent, and the hardness is 68.5 HB.

Comparative example 4

Preparation of a 6xxx series wrought aluminum alloy compositely treated with Sr/Al-5 Ti-B: the 6xxx series recycled aluminum scrap after primary screening is melted according to the method of the comparative example 1, the initial basic components are the same as the comparative example 1, the scum is removed, and the aluminum scrap is kept warm and kept stand for 20 min. Adding an Al-10Sr alterant and an Al-5Ti-B refiner into the melt, keeping the temperature of the melt at 720 ℃, uniformly stirring after melting, and standing for 20min with heat preservation; wherein the addition amount of the Al-10Sr alterant and the Al-5Ti-B refiner is 0.5 percent of the mass of the melt. And casting the melt into an ingot by the method of the comparative example 1, and then placing the ingot in a resistance furnace for homogenization heat treatment, wherein the homogenization temperature is 480 ℃ and the heat preservation time is 8 hours. And (4) carrying out multi-pass rolling after homogenization, wherein the deformation amount of each pass is 5%, and the total deformation amount is 50%, so as to obtain the regenerated wrought aluminum alloy.

FIG. 4 shows the as-cast optical microstructure of the wrought aluminum alloy prepared in comparative example 4, in which the morphology of the wrought aluminum alloy phase prepared in comparative example 4 by Sr/Al-5Ti-B complex treatment is changed, the dendritic structure is broken, the needle-like phase is transformed into Chinese character-like, and other impurity phases are transformed into ellipsoid-like phases distributed in the interior of the grains or in the grain boundary. The hot cracking sensitivity coefficient HTS of the alloy in an as-cast state is 160, the tensile strength is 200.2MPa, the elongation is 10.8 percent, and the hardness is 53.3 HB. The tensile strength of the alloy in the rolled state was 229.4MPa, the elongation was 7.5%, and the hardness was 69.6 HB.