Aluminum alloy ingot casting homogenizing annealing stepped cooling process
Technical Field
The invention relates to an aluminum alloy manufacturing process, in particular to an aluminum alloy ingot casting homogenizing annealing stepped cooling process, and belongs to the field of aluminum alloy casting.
Background
The ingot homogenizing and cooling process is used as an important ring of heat treatment to directly influence the structure and the performance of the ingot. Because of the inheritability of the ingot structure, the ingot structure has great influence on the structure and the performance of the extruded profile, wherein the size, the quantity and the distribution of precipitates are mainly influenced.
When the cooling speed of the cast ingot is low, coarse and needle-shaped precipitates can be precipitated in the cast ingot structure, so that the cast ingot forms a band-shaped structure in subsequent processing, the extrusion deformation resistance is increased, and the extrusion process is not facilitated. The coarse precipitates are difficult to completely dissolve during quenching, so that the strength after quenching and artificial aging is reduced, and the surface quality of the product is seriously reduced.
When the cooling speed of the cast ingot is too high, fine and dispersed precipitates can be precipitated in the cast ingot structure, so that the yield strength of the product is improved, and the surface quality is improved. However, the cooling rate is too fast, which can produce a quenching effect.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the invention provides a homogenizing annealing stepped cooling process for an aluminum alloy cast ingot, aiming at overcoming the defects in the prior art and mastering the reasonable cooling speed of the cast ingot.
The technical scheme for solving the technical problems is as follows: a homogenizing annealing step cooling process for an aluminum alloy ingot, wherein the aluminum alloy is a 6XXX series ingot, and comprises the following steps:
(S1) heating the fusion-cast aluminum alloy ingot from room temperature to 560 ℃ at a heating rate of 80-100 ℃ and keeping the temperature for a minimum of 10 hours;
(S2) cooling the aluminum alloy ingot after heat preservation in the step (S1) to 440-460 ℃ at a cooling speed of 190-200 ℃/h by adopting a cooling process;
(S3) cooling the aluminum alloy ingot obtained in the step (S2) to 150-160 ℃ at a cooling speed of 240-260 ℃/h by adopting a cooling process;
(S4) cooling the aluminum alloy ingot obtained in the step (S3) to room temperature at a cooling speed of 110-120 ℃/h by adopting a cooling process.
Further, in the step (S2), after the aluminum alloy ingot is cooled to 440-460 ℃, the next stage of cooling is performed without heat preservation.
Further, in the step (S3), after the aluminum alloy ingot is cooled to 150-160 ℃, the cooling of the next stage is directly performed without heat preservation.
Further, the cooling process employed in steps (S2) to (S4) is air cooling, water cooling, or water mist cooling.
Further, the cooling process employed in the step (S2) is air cooling.
Further, the cooling process adopted in the step (S3) is air cooling and water mist cooling, wherein the water pressure of the water mist cooling is 0.01-0.02 Mpa.
Further, the cooling process used in the step (S4) is air cooling and water cooling, wherein the water pressure of the water cooling is 0.05-0.10 Mpa.
Has the advantages that: the aluminum alloy ingot homogenizing annealing stepped cooling process has the advantages that the cooling is divided into three stages, namely a high-temperature stage (555-; in order to verify that the production process disclosed by the invention is subjected to a comparative test, wherein an experimental group adopts the cooling process disclosed by the invention, and a comparative group adopts the existing cooling process, and through test comparison, the aluminum ingot adopting the cooling process disclosed by the invention is low in extrusion resistance and high in extrusion product speed when being extruded into an aluminum profile, so that the production efficiency is improved; meanwhile, the thickness of a coarse crystal layer of an extrusion-molded product is reduced, and the product quality is improved.
Drawings
FIG. 1 shows a metallographic structure of an ingot according to an experimental example of the present invention;
FIG. 2 is a metallographic structure of an ingot of comparative example of the present invention;
FIG. 3 shows a coarse-grained layer after extrusion according to a test example of the present invention;
FIG. 4 shows a coarse-grained layer after extrusion of a comparative example according to the invention.
Detailed Description
The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.
A casting ingot of aluminum alloy is 6A02, the diameter is 302mm, the casting ingot is heated from room temperature to 560 ℃ by 6 hours, and the temperature is preserved for 10 hours. Then cooling to 440-460 ℃ at a cooling speed of 190-200 ℃/h by adopting an air cooling manner; after the cooling temperature is qualified, the cooling speed is changed to 240-; after the cooling temperature is qualified, the cooling speed is changed to 110-.
After the ingot is subjected to homogenizing annealing and cooling, the metallographic structure of the ingot is checked, and the result is shown in the attached figure 1.
In order to verify the property characteristics of the aluminum ingot obtained by the cooling process of the scheme during extrusion of the aluminum alloy profile and after extrusion, three extrusion tests were performed as test examples, namely F21, F22 and F23, specifically as shown in table 1. The coarse grain layer thickness of the extruded aluminum profiles was then measured and was in the range of 112-117um as shown in fig. 3.
Table 1 test examples extrusion test
Comparative example
The existing aluminum alloy ingot casting annealing cooling process is utilized to cool the aluminum alloy under the same condition to room temperature. Specifically, air cooling is carried out for 70min, and then water pressure is adjusted to 0.1-0.15Mpa, and air cooling is carried out for 60 min.
After the ingot is subjected to homogenizing annealing and cooling, the metallographic structure of the ingot is checked, and the result is shown in the attached figure 2.
Similarly, three extrusion runs were performed on aluminum ingots using the cooling process described in the comparative examples, F11, F12, and F13, respectively, as shown in table 2. The coarse grain layer thickness of the extruded aluminum profiles was then measured to be in the range of 253-.
Table 2 comparative example squeeze test
As can be seen from a comparison of tables 1 and 2, the breakthrough pressure and the intermediate pressure in the test examples were reduced in comparison with the comparative example during the extrusion molding of the aluminum alloy profile, i.e., the extrusion resistance in the test examples was lower and the extrusion speed was faster.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.