CN114737144B

CN114737144B - Homogenization heat treatment method of 2324 aluminum alloy

Info

Publication number: CN114737144B
Application number: CN202210293211.3A
Authority: CN
Inventors: 付彦军; 祖立成; 程素玲; 宋俊强; 姜舒洁; 王知远; 金玉龙
Original assignee: Tianjin Zhongwang Aluminium Industry Co ltd
Current assignee: Tianjin Zhongwang Aluminium Industry Co ltd
Priority date: 2022-03-23
Filing date: 2022-03-23
Publication date: 2023-07-14
Anticipated expiration: 2042-03-23
Also published as: CN114737144A

Abstract

The invention relates to a homogenization heat treatment method of 2324 aluminum alloy, which belongs to the technical field of aluminum alloy heat treatment, and the homogenization heat treatment method of 2324 aluminum alloy comprises the steps of heating an aluminum alloy cast ingot to 494-495 ℃, then heating the aluminum alloy cast ingot to 498-500 ℃ for 25-30h, and finally air-cooling the aluminum alloy cast ingot to 20-25 ℃. According to the invention, the influence of temperature on the eutectic phase dissolution is fully exerted by slowly heating at the melting temperature of the low-melting-point eutectic phase, the dissolution of the low-melting-point eutectic phase is quickened under the condition that the cast ingot is not excessively burnt, and along with the rise of the temperature, the dissolution time of theta (Al 2 Cu) and S (Al 2 CuMg) formed by unbalanced solidification is also greatly reduced, so that the time of homogenizing heat treatment of the aluminum alloy cast ingot is greatly saved, the cost of heat treatment of the aluminum alloy is saved, and the processing efficiency of the aluminum alloy is improved.

Description

Homogenization heat treatment method of 2324 aluminum alloy

Technical Field

The invention belongs to the technical field of aluminum alloy heat treatment, and relates to a 2324 aluminum alloy homogenizing heat treatment method.

Background

2324 aluminum alloy is an Al-Cu-Mg alloy, and is a 2xxx aluminum alloy developed by reducing impurity element components and optimizing main alloy element components on the basis of 2024 aluminum alloy; the high-strength high-damage-tolerance composite material has the characteristics of high specific strength and high damage tolerance, is an important structural material in the aviation field, and is widely applied to design parts with high damage tolerance such as lower wings of an aircraft.

Various precipitated phases, such as low-melting ternary eutectic phases alpha (Al) +theta (Al 2 Cu) +S (Al 2 CuMg), primary phases containing impurity elements Fe, si and the like, and theta (Al 2 Cu), S (Al 2 CuMg) and the like formed by unbalanced solidification are formed in the solidification process of the 2324 alloy, the primary phases are large and hard and brittle, stress concentration is easy to occur around the phases, cracking can occur under lower stress, and become crack sources, so that the mechanical properties of the alloy are reduced, and meanwhile, the non-equilibrium phases collect a large amount of alloy elements Mg and Cu, so that the solid solubility of an aluminum alloy matrix is reduced, the aging precipitation power is reduced, the density and the volume fraction of the precipitated phases are reduced, and the aging strengthening effect is reduced. Therefore, the ingot is required to be subjected to homogenization heat treatment before subsequent processing, wherein the homogenization heat treatment is to heat the ingot below the liquidus temperature for a certain period of time, and the main purpose of the homogenization heat treatment is to eliminate eutectic structures formed by unbalanced solidification at a grain boundary in the casting process, coarse theta (Al 2 Cu), S (Al 2 CuMg) and the like.

The traditional 2324 aluminum alloy homogenization process mainly comprises single-stage and double-stage homogenization. Single-stage homogenization mainly refers to raising the ingot to a certain fixed temperature and preserving the ingot for a period of time, but the ingot can only be preserved at a lower temperature, because the melting point of the eutectic phase with a low melting point is lower, the eutectic phase with a low melting point is melted by continuously raising the temperature, overburning is generated, and the dissolution effect of the primary phase is not ideal due to the lower temperature. The two-stage homogenization is to keep the temperature for a period of time at a lower temperature, so as to dissolve the low-melting eutectic phase back, thereby increasing the temperature of the second-stage homogenization, and continuously heating to a higher temperature to keep the temperature, and the two-stage homogenization can achieve the purpose of eliminating the eutectic structure formed by unbalanced solidification and coarse theta and S phases, but has longer temperature keeping time, and particularly needs longer time at a lower temperature to fully dissolve the low-melting eutectic phase back.

In order to achieve the purposes of shortening the time, saving the energy and simultaneously ensuring the sufficient dissolution of the soluble coarse phase, the following production process is specially provided.

Disclosure of Invention

Accordingly, the present invention has an object to provide a method for homogenizing heat treatment of 2324 aluminum alloy, which can obtain 2324 ingots with sufficient primary phase dissolution and elimination of coarse θ (Al 2 Cu) and S (Al 2 CuMg) on the premise of time reduction and energy saving.

In order to achieve the above purpose, the present invention provides the following technical solutions:

a homogenization heat treatment method of 2324 aluminum alloy, comprising the following steps:

primary heating: heating an aluminum alloy ingot to 494-495 ℃;

and (3) secondary heating: heating the aluminum alloy cast ingot after primary heating to 498-500 ℃ for 25-30 h;

air cooling: and air-cooling the aluminum alloy cast ingot after secondary heating to 20-25 ℃.

Further, during the primary heating, the heating rate was 40 ℃/h.

Further, in the secondary heating process, the heating speed is 0.1-0.3 ℃/h.

Further, the aluminum alloy cast ingot comprises the following raw materials in percentage by weight: si less than or equal to 0.10%, fe less than or equal to 0.12%, cu:3.8 to 4.4 percent of Mn:0.30 to 0.90 percent of Mg:1.20 to 1.80 percent, less than or equal to 0.10 percent of Cr, less than or equal to 0.25 percent of Zn, less than or equal to 0.15 percent of Ti, less than or equal to 0.05 percent of single impurity, less than or equal to 0.15 percent of total and the balance of Al.

Further, the method comprises the following steps:

manufacturing an aluminum alloy cast ingot: the prepared raw materials are evenly mixed and then smelted into liquid aluminum alloy, and the liquid aluminum alloy is cast into aluminum alloy cast ingots after the procedures of standing, refining, slag skimming, online degassing and filtering.

Further, during the primary heating and/or the secondary heating, the aluminum alloy ingot is heated by an air furnace.

The invention also provides 2324 aluminum alloy which comprises less than or equal to 0.10% of Si, less than or equal to 0.12% of Fe and less than or equal to 0.12% of Cu by weight: 3.8 to 4.4 percent of Mn:0.30 to 0.90 percent of Mg:1.20 to 1.80 percent, less than or equal to 0.10 percent of Cr, less than or equal to 0.25 percent of Zn, less than or equal to 0.15 percent of Ti, less than or equal to 0.05 percent of single impurity, less than or equal to 0.15 percent of total and the balance of Al.

The invention has the beneficial effects that:

1. according to the invention, after the aluminum alloy ingot is heated to the melting temperature of the low-melting point eutectic phase, the aluminum alloy ingot is not kept at the same temperature for a long time, but is slowly heated, the influence of the temperature on the reflow of the low-melting point eutectic phase is fully exerted, and the overburning temperature is continuously increased in the process of continuously reflow the low-melting point eutectic phase, so that the overburning phenomenon of the ingot is not caused by the slow heating, the reflow speed of the primary phase is accelerated, and the reflow of theta (Al 2 Cu) and S (Al 2 CuMg) formed by unbalanced solidification can be performed more quickly along with the increase of the temperature, so that the homogenization time of the aluminum alloy ingot is greatly saved.

2. Compared with the traditional single-stage homogenization process, the invention has the advantages that the eutectic phase is fully dissolved back in the slow heating process, so that the overburning temperature point is increased, the temperature is continuously increased within a certain range, the ingot casting still can not generate overburning, and the theta (Al 2 Cu) and S (Al 2 CuMg) formed by unbalanced solidification have full dissolution effect and short homogenization time; in the traditional two-stage homogenization system, the low-melting eutectic phase can be fully dissolved back only after the first-stage temperature is kept for a long time, but along with the progress of the heat preservation, the effect of time on the dissolution back of the eutectic phase is not obvious, and the influence of the temperature on the dissolution back of the eutectic phase is fully exerted by slowly heating at the melting temperature of the low-melting eutectic phase, so that the dissolution back of the low-melting eutectic phase is accelerated under the condition that an ingot is not excessively burned, and along with the rise of the temperature, the dissolution back time of theta (Al 2 Cu) and S (Al 2 CuMg) formed by unbalanced solidification is also greatly reduced, and the ingot homogenization time is greatly saved.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and other advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the specification.

Drawings

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in the following preferred detail with reference to the accompanying drawings, in which:

FIG. 1 is a DSC curve of an aluminum alloy ingot after homogenization heat treatment in example 1;

FIG. 2 is a DSC curve of an aluminum alloy ingot after homogenization heat treatment in example 2;

FIG. 3 is a DSC curve of an aluminum alloy ingot after homogenization heat treatment in example 3;

FIG. 4 is a DSC curve of an aluminum alloy ingot after a homogenization heat treatment in comparative example 1;

FIG. 5 is a DSC curve of an aluminum alloy ingot after homogenization heat treatment in comparative example 2;

FIG. 6 is a DSC curve of an aluminum alloy ingot after homogenization heat treatment in comparative example 3;

FIG. 7 is a DSC curve of an aluminum alloy ingot after homogenization heat treatment in comparative example 4;

FIG. 8 is an SEM scanning photograph of an aluminum alloy ingot after being subjected to homogenization heat treatment in example 1;

FIG. 9 is an SEM scanning photograph of an aluminum alloy ingot after being subjected to homogenization heat treatment in example 2;

FIG. 10 is an SEM scanning photograph of an aluminum alloy ingot after homogenization heat treatment in example 3;

FIG. 11 is an SEM scanning photograph of an aluminum alloy ingot after being subjected to homogenization heat treatment in comparative example 1;

FIG. 12 is an SEM scanning photograph of an aluminum alloy ingot after being subjected to homogenization heat treatment in comparative example 2;

FIG. 13 is an SEM scanning photograph of an aluminum alloy ingot after homogenization heat treatment in comparative example 3;

FIG. 14 is an SEM scanning photograph of an aluminum alloy ingot after homogenization heat treatment in comparative example 4.

Detailed Description

Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the illustrations provided in the following embodiments merely illustrate the basic idea of the present invention by way of illustration, and the following embodiments and features in the embodiments may be combined with each other without conflict.

Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to limit the invention; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, it should be understood that, if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc., that indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but not for indicating or suggesting that the referred device or element must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and should not be construed as limiting the present invention, and that the specific meaning of the above terms may be understood by those of ordinary skill in the art according to the specific circumstances.

A. and (3) batching: the raw materials for preparing the high damage tolerance aluminum alloy cast ingot are proportioned according to the weight percentage, namely: si less than or equal to 0.10%, fe less than or equal to 0.12%, cu:3.8 to 4.4 percent of Mn:0.30 to 0.90 percent of Mg:1.20 to 1.80 percent, less than or equal to 0.10 percent of Cr, less than or equal to 0.25 percent of Zn, less than or equal to 0.15 percent of Ti, less than or equal to 0.05 percent of single impurity, less than or equal to 0.15 percent of total and the balance of Al.

B. And (3) casting: adding the prepared aluminum alloy raw materials into a smelting furnace, uniformly mixing, smelting into liquid aluminum alloy, and casting the liquid aluminum alloy into an aluminum alloy cast ingot after the procedures of standing, refining, slag skimming, online degassing and filtering;

C. homogenizing: heating the aluminum alloy ingot to 494-495 ℃ at a speed of 40 ℃/h in an air furnace, heating to 498-500 ℃ for 25-30h, and then discharging and air cooling to 20-25 ℃.

The present invention is further illustrated by the following examples and comparative examples, wherein the initial heating temperature in each example is determined from the overburning temperature of the low melting eutectic phase corresponding to the DSC experiment of the aluminum alloy ingot; the dissolution effect of the precipitated phase is determined by the areas of heat absorption peaks corresponding to the eutectic phase, theta (Al 2 Cu) and S (Al 2 CuMg) phases in DSC experiment after homogenization heat treatment, the smaller the areas of the heat absorption peaks are, the more obvious the dissolution effect is, and the dissolution degree of the precipitated phase and whether the tissue has overburning phenomenon are further determined by the area statistics of residual phases in SEM scanning pictures.

Example 1

A. And (3) batching: calculating the consumption of each aluminum alloy raw material, preparing the aluminum alloy raw materials according to the proportion, and Si:0.026%, fe:0.067%, cu:4.263%, mn:0.605%, mg:1.506%, cr:0.001%, zn:0.02%, ti:0.023% and the balance of Al.

B. And (3) casting: adding the prepared aluminum alloy raw materials into a smelting furnace, uniformly mixing, smelting into liquid aluminum alloy, and casting the liquid aluminum alloy into an aluminum alloy cast ingot with the specification of 450 multiplied by 1680 multiplied by 6500mm after the procedures of standing, refining, slag skimming, online degassing and filtering.

C. Homogenizing: heating the aluminum alloy ingot to 495 ℃ at a speed of 40 ℃/h in an air furnace, heating to 500 ℃ at a speed of 0.2 ℃/h, discharging and air cooling to 20 ℃, and taking 25 hours from 495 ℃ to 499 ℃ together.

Example 2

In the embodiment, in the step C, the aluminum alloy ingot is heated to 494 ℃ at a speed of 40 ℃/h in an air furnace, and then heated to 500 ℃ at a speed of 0.22 ℃/h, and the temperature is controlled to be between 494 ℃ and 500 ℃ for 27 hours.

Example 3

In this example, in step C, an aluminum alloy ingot was heated to 495℃at a rate of 40℃per hour in an air furnace, and then heated to 499℃at a rate of 0.13℃per hour, for a total of 30 hours from 494℃to 500 ℃.

Comparative example 1

In the comparative example, in the step C, an aluminum alloy cast ingot is heated to 493 ℃ at a speed of 40 ℃/h in an air furnace, is kept for 16 hours, is heated to 498 ℃ at a speed of 5 ℃/h, and is kept for 12 hours; the incubation was carried out from 493 to 498℃for a total of 29h.

Comparative example 2

In the comparative example, in the step C, an aluminum alloy cast ingot is heated to 495 ℃ at a speed of 40 ℃/h in an air furnace, is kept for 18 hours, is heated to 500 ℃ at a speed of 5 ℃/h, and is kept for 16 hours; the temperature is kept from 493 to 498 ℃ for 35 hours.

Comparative example 3

In the comparative example, in the step C, an aluminum alloy cast ingot is heated to 495 ℃ at a speed of 40 ℃/h in an air furnace, is insulated for 12h, is heated to 500 ℃ at a speed of 5 ℃/h, and is insulated for 20h; incubate from 495 to 500℃for a total of 33h.

Comparative example 4

In the comparative example, in the step C, an aluminum alloy ingot is heated to 495 ℃ in an air furnace at a speed of 40 ℃/h, and the temperature is kept for 40h, and the first-stage homogenization is adopted for 40 hours in total.

Table 1 is obtained from the homogenization time statistics of each of the above examples and comparative examples.

Table 1 statistics of homogenization time for each example and comparative example

Alloy	Homogenization/°c.h	Homogenization time/h
			Example 1	495-500 deg.C (heating rate 0.2 deg.C/h)	25
Example 2	494 ℃ -500 ℃ (heating rate 0.22 ℃/h)	27
			Example 3	495-499 deg.C (heating rate 0.13 deg.C/h)	30
Comparative example 1	493℃16h+498℃12h	29
			Comparative example 2	495℃18h+500℃16h	35
Comparative example 3	495℃12h+500℃20h	33
			Comparative example 4	495℃*40h	40

Please refer to fig. 1-7, which are DSC curves of the aluminum alloy ingots after the homogenization heat treatment in examples 1-3 and comparative examples 1-4, respectively, and fig. 8-14, which are SEM scanning photographs of the aluminum alloy ingots after the homogenization heat treatment in examples 1-3 and comparative examples 1-4, respectively, and the statistical data in table 2 are obtained through fig. 1-14.

TABLE 2 comparative examples and comparative examples homogenization effect comparison Table

Alloy	Endothermic peak area J/g	Residual phase content%	Whether or not to overcooke
				Example 1	1.284	1.10	Whether or not
Example 2	1.457	1.07	Whether or not
				Example 3	1.524	1.09	Whether or not
Comparative example 1	3.566	1.24	Whether or not
				Comparative example 2	1.415	1.05	Whether or not
Comparative example 3	1.252	1.01	Whether or not
				Comparative example 4	1.981	1.27	Whether or not

From the comparison of example 1 and comparative example 3 and example 2 and comparative example 2, it can be seen that: the heat absorption peak area of the embodiment is similar to that of the comparative example, but the homogenization time of the embodiment is 8 hours shorter than that of the comparative example, so that the homogenization time is shortened, the homogenization efficiency is greatly improved, and the energy is saved.

From the results of example 3 and comparative example 1, it can be seen that: the homogenization time of the two is similar, but the endothermic peak area and the residual phase proportion of the embodiment are respectively smaller than those of the comparative example by 2.042J/g and 0.15 percent, and the homogenization effect of the homogenization treatment method is obviously higher than that of the traditional homogenization treatment method.

As can be seen from comparative example 4: the area of the endothermic peak in the traditional single-stage homogenization DSC is 1.981J/g, and the heat preservation time reaches 40 hours, but the area of the endothermic peak is still larger than the area of the corresponding endothermic peak in the embodiment; as can also be seen from SEM scanning pictures, the area ratio of the non-redissolved second phase is 1.27%, which is higher than that of the homogenization heat treatment system corresponding to the examples, and the homogenization time is longer than that of any one of the examples.

Therefore, by adopting the homogenization heat treatment method provided by the invention, the initial heating temperature, the heating speed and the highest heating temperature are controlled, so that the dissolution effect equivalent to or even better than the traditional two-stage homogenization can be obtained under the condition of greatly reducing the homogenization time.

Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the claims of the present invention.

Claims

1. A homogenization heat treatment method of 2324 aluminum alloy, which is characterized by comprising the following steps:

primary heating: heating an aluminum alloy ingot to 494-495 ℃ at a heating speed of 40 ℃/h;

and (3) secondary heating: heating the aluminum alloy ingot after primary heating to 498-500 ℃ for 25-30h, wherein the heating speed is 0.1-0.3 ℃/h;

air cooling: and cooling the aluminum alloy cast ingot subjected to secondary heating to 20-25 ℃.

2. The homogenization heat treatment method of 2324 aluminum alloy of claim 1, wherein: the aluminum alloy cast ingot comprises the following raw materials in percentage by weight: si less than or equal to 0.10%, fe less than or equal to 0.12%, cu:3.8 to 4.4 percent of Mn:0.30 to 0.90 percent of Mg:1.20 to 1.80 percent, less than or equal to 0.10 percent of Cr, less than or equal to 0.25 percent of Zn, less than or equal to 0.15 percent of Ti, less than or equal to 0.05 percent of single impurity, less than or equal to 0.15 percent of total and the balance of Al.

3. The homogenization heat treatment method of 2324 aluminum alloy of claim 1, wherein: the method also comprises the following steps:

4. The homogenization heat treatment method of 2324 aluminum alloy of claim 1, wherein: in the primary heating and/or secondary heating process, the aluminum alloy ingot is heated by an air furnace.