CN108286029B

CN108286029B - Method for improving corrosion resistance of 5083 aluminum alloy plate

Info

Publication number: CN108286029B
Application number: CN201810236794.XA
Authority: CN
Inventors: 黄元春; 邵虹榜; 郭晓芳
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2018-03-21
Filing date: 2018-03-21
Publication date: 2020-02-18
Anticipated expiration: 2038-03-21
Also published as: CN108286029A

Abstract

The invention discloses a cast ingot homogenizing method for improving corrosion resistance of a 5083 aluminum alloy plate, which comprises the following steps of cutting a cast ingot into blocks; then the ingot is subjected to heat preservation for 4-8h at the temperature of 500-560 ℃ for homogenization treatment; hot rolling the cast ingot to 8-10 mm; performing cold rolling with low deformation for five passes, wherein the thickness of the rolled aluminum plate is 4 mm; after cold rolling, the material is annealed to obtain an O-state plate of the 5083 aluminum alloy with high corrosion resistance. Solves the problems of large homogenized energy consumption, long time and serious metal oxidation loss of a 5083 aluminum alloy plate in the prior industrial production, and has good corrosion resistance.

Description

Method for improving corrosion resistance of 5083 aluminum alloy plate

Technical Field

The invention belongs to the technical field of aluminum alloy processing, and relates to a cast ingot homogenizing method for improving corrosion resistance of a 5083 aluminum alloy plate.

Background

5083 aluminum alloys have high strength and good corrosion resistance, and are widely used in shipbuilding. The industrial production process flow of the 5083 ship plate mainly comprises casting, homogenizing, hot rolling, cold rolling and annealing. Where the homogenization heat treatment has been considered an indispensable part of the production of 5083 sheets, the homogenization process affects the recovery and recrystallization behavior of the sheet during the subsequent heat treatment, resulting in a different microstructure; homogenization also has a significant effect on the size, density and distribution of the second phase; elimination or reduction of genetic microstructure deviating from equilibrium organization under actual crystallization conditions can also be achieved by homogenization.

The traditional ingot casting homogenization process for 5083 plates is 460-470 ℃/24h, the process is high in energy consumption, the oxidation loss effect of materials is serious, and the demand of 5083 ship plates with high corrosion resistance, high efficiency and low cost is more and more urgent. Therefore, in order to improve the economic efficiency, save energy and meet the increasing market demand, some enterprises want to optimize the homogenization process in the production of the sheet material. On the other hand, domestic and foreign scholars research on microstructure, corrosion resistance and the like of plates under 5083 cast ingot unhomogenization, low-temperature single-stage homogenization and low-temperature-high temperature composite homogenization systems, and partial scholars research that the influence of cast ingot homogenization on grain size and second phase precipitation is small, while 5083 aluminum alloy is mainly used in ship plate industry and has high requirement on corrosion resistance, but the research on corrosion resistance of plates processed by cast ingots through homogenization is few.

Chinese patent CN102876939A discloses a process for carrying out homogenization annealing treatment on 5083 magnesium-aluminum alloy at the temperature of 460-475 ℃ for 24-25 h. But the homogenization energy consumption is large, the time is long, and the metal oxidation loss is serious. Patent CN101880802A discloses a method for manufacturing Al-Mg series high magnesium aluminum alloy, the homogenization system is 450-480 ℃, the processing time is 10-24h, although the strength and the tensile property are good, softening does not occur after baking varnish, the formability and the impact resistance are satisfied, but the important performance of corrosion resistance is not considered. Therefore, it is imperative to explore a scientific and reasonable 5083 ship plate homogenization system and a corresponding processing technology to produce the plate meeting the requirements.

Disclosure of Invention

In order to achieve the purpose, the invention provides a method for homogenizing an ingot casting to improve the corrosion resistance of a 5083 aluminum alloy plate, which solves the problems of high energy consumption, long time and serious metal oxidation loss of a 5083 aluminum alloy plate in the existing industrial production and has good corrosion resistance.

In order to solve the technical problems, the technical scheme adopted by the invention is that the ingot casting homogenization method for improving the corrosion resistance of the 5083 aluminum alloy plate is carried out according to the following steps:

step 1, cutting an ingot into blocks;

step 2, then carrying out homogenization treatment on the ingot at the temperature of 500-;

step 3, hot rolling the cast ingot to 8-10 mm;

step 4, performing cold rolling with low deformation for five passes, wherein the thickness of the rolled aluminum plate is 4 mm;

and 5, after cold rolling, annealing the material to obtain the O-state plate of the 5083 aluminum alloy with high corrosion resistance.

Further, in the step 1, the ingot is cut into blocks with the thickness of 510-530 mm.

Further, in the step 3, the ingot is subjected to multi-pass hot rolling at 510 ℃ to 8-10 mm.

Further, in the step 3, the temperature is ensured to be higher than 360 ℃ in the whole hot processing process.

Further, in the step 4, the cold rolling deformation is 45% -55%.

Further, in the step 5, the material is annealed at 520 ℃ for 3 hours at 500 ℃.

The invention has the beneficial effects that the 5083 aluminum alloy ingot is kept warm at the temperature of 500-8) h, carrying out homogenization treatment, and then carrying out hot rolling, cold rolling and annealing; by changing the temperature and time in the homogenization process, Al in the plate can be obtained₆More Mn phase, no Mg₂The Si phase reduces the dislocation density in the plate matrix, the grain size is finer and more uniform, and the microstructure characteristics jointly determine that the corrosion resistance of the plate is enhanced. Meanwhile, the energy is saved, the economic benefit is improved, and the ever-increasing market demand is met.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a graph showing the results of polarization curve tests of sheets O-1, O-2 and O-3 in a 3.5% NaCl solution in examples of the present invention.

FIG. 2 derives E by Tafel region and linear fitting_corr(FIG. 2a) and j_corr(FIG. 2 b).

FIG. 3 is a grain distribution plot of the rolled face and cross-section of a 5083-O temper sheet wherein (a) O-1 RS; (b) o-1 HS; (c) o-2 RS; (d) o-2 HS; (e) o-3 RS; (f) o-3 HS.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

A cast ingot homogenizing method for improving corrosion resistance of a 5083 aluminum alloy plate is carried out according to the following steps:

step 1, cutting the ingot into blocks with the thickness of 510-530 mm;

the homogenization temperature is the most significant factor affecting the alloy structure, and it has been found that when the homogenization heat treatment is performed at a temperature lower than the solidus line and close to this temperature, the second phase is melted and spheroidized, but if the heat treatment temperature is too high, a liquid phase is generated, and the alloy is excessively burned. Therefore, under the condition of ensuring that the alloy is not over-sintered, the higher the temperature of the homogenizing annealing, the more favorable the melting of the second phase is, the more dispersed the structure is, and the better the performance is.

Through experiments, the iron-rich phase has small morphological change, more second phases and coarse dendritic crystals after homogenization treatment at a lower temperature (below 500 ℃); when the temperature is raised to 530 ℃ and 560 ℃, the coarse second phase is melted and changed into a short rod shape, the finer the dendritic crystal structure is, the more dispersed the structure is, and the indissolvable second phase in the aluminum alloy is mainly an iron-rich phase; however, continued temperature increases can result in coarse second phases (575 ℃ C.) and even overburning (590 ℃ C.). Therefore, the temperature is 500-560 ℃, and the heat preservation time is shortened to 4-8 h. The invention has the advantages of short heat preservation time, low energy consumption, short period and the like.

Step 3, carrying out hot rolling on the cast ingot at 510 ℃ for multiple times (not less than 3) to 8-10mm, wherein the temperature is ensured to be higher than 360 ℃ in the whole hot processing process;

step 4, performing cold rolling with low deformation for five passes, wherein the cold rolling deformation is 45% -55%, and the thickness of the rolled aluminum plate is about 4 mm;

and 5, annealing the material at the temperature of 500-520 ℃ for 3 hours after cold rolling to obtain the O-state plate of the 5083 aluminum alloy with high corrosion resistance.

The test specimen samples were cut into rectangular bars (40mm × 25mm × 4mm) and the edges of the wire cut samples were ground with metallographic sandpaper to # 2000 metallographic sandpaper. The samples were pretreated according to the intergranular corrosion standard before corrosion, followed by observation under a metallographic microscope and counting of the maximum penetration depth, the intergranular corrosion rating and determination of the EXCO rating by visual inspection, and the polarization curve thereof was determined.

Example 1

Cutting the cast ingot into blocks with the thickness of 510 mm; then, the cast ingot is subjected to heat preservation for 4 hours at the temperature of 500 ℃ for homogenization treatment; carrying out 3-pass hot rolling on the cast ingot at 510 ℃ to 8mm, and ensuring the temperature to be higher than 360 ℃ in the whole hot processing process; performing cold rolling with low deformation for five passes, wherein the cold rolling deformation is 45-55%, and the thickness of the rolled aluminum plate is 4 mm; after cold rolling, the material was annealed at 500 ℃ for 3 hours to obtain an O-plate of a 5083 aluminum alloy with high corrosion resistance.

Example 2

Cutting the cast ingot into blocks with the thickness of 520 mm; then the cast ingot is subjected to heat preservation for 6 hours at the temperature of 530 ℃ for homogenization treatment; carrying out hot rolling on the cast ingot at 510 ℃ for 4 times to 9mm, and ensuring the temperature to be higher than 360 ℃ in the whole hot processing process; performing cold rolling with low deformation for five passes, wherein the cold rolling deformation is 45-55%, and the thickness of the rolled aluminum plate is 4 mm; after cold rolling, the material was annealed at 510 ℃ for 3 hours to obtain an O-plate of a highly corrosion resistant 5083 aluminum alloy.

Example 3

Cutting the cast ingot into blocks with the thickness of 530 mm; then the ingot is subjected to heat preservation for 8 hours at the temperature of 560 ℃ for homogenization treatment; carrying out 3-pass hot rolling on the cast ingot at 510 ℃ to 10mm, and ensuring the temperature to be higher than 360 ℃ in the whole hot processing process; performing cold rolling with low deformation for five passes, wherein the cold rolling deformation is 45-55%, and the thickness of the rolled aluminum plate is 4 mm; after cold rolling, the material was annealed at 520 ℃ for 3 hours to obtain an O-plate of a highly corrosion-resistant 5083 aluminum alloy.

Comparative example 1

And (3) keeping the temperature of the cast ingot at 465 ℃ for 24h, carrying out 4-pass hot rolling at 510 ℃ to 9mm, and ensuring the temperature to be higher than 360 ℃ in the whole hot processing process. And finally, performing cold machining with low deformation in five passes, and cold-rolling to 4 mm. After cold rolling, the material was annealed at 510 ℃ for 3 hours.

Comparative example 2

No homogenization treatment was performed, and the other conditions were the same as in comparative example 1.

Comparative example 3

The ingot is kept at 560 ℃ for 24h for homogenization treatment, and other conditions are the same as in comparative example 1.

Comparative example 4

The ingot is kept at 500 ℃ for 12h for homogenization treatment, and other conditions are the same as in comparative example 1.

Comparative example 5

The ingot is kept warm at 450 ℃ for 5h for homogenization treatment, and other conditions are the same as in comparative example 1.

Table 1 shows the maximum intergranular corrosion depths measured by the samples taken from the two plates, the maximum corrosion depths of 3 samples taken from each plate have smaller difference, the maximum corrosion penetration depths are 47.66 μm, 42.97 μm, 62.50 μm, 55.47 μm and 48.36 μm respectively compared with the maximum corrosion penetration depths of comparative examples 1-5, namely the corrosion performance of 465 ℃ multiplied by 24h and the non-homogenized system plate is slightly better than the other, the intergranular corrosion grades are all 3 grades, the maximum corrosion penetration depths of examples 1, 2 and 3 are 26.69, 26.15 and 27.10 μm respectively, namely the intergranular corrosion depths of 530 ℃ multiplied by 6h are the shallowest, the intergranular corrosion resistance is the best, the intergranular corrosion grades are all 2 grades, the corrosion resistance of the plates of the examples is better than that of the comparative examples, and the influence of different homogenization systems on the intergranular corrosion resistance of the plates is different.

TABLE 1 intergranular Corrosion test results statistics

According to the table 1, comparative examples 1 and 2 with better intergranular corrosion performance and example 2 with best performance are selected for comparative analysis of electrochemical behavior. FIG. 2 is a graph showing values of the self-etching potential (Ecorr) and the self-etching current density (jcorr) calculated by Tafel extrapolation and linear fitting method from a polarization curve (FIG. 1) measured in an aqueous solution containing 3.5% NaCl. In order to make the result more reliable, each plate was subjected to three corrosion tests. Comparative example 1, example 2 and comparative example 2 are represented by O-1, O-2 and O-3, respectively. The average value of Ecorr of the sample O-1 is-462.2 mV, which can be obtained from an error bar of the experimental result obtained in the step (a) of FIG. 2, the fluctuation of the experimental result is small, and the corrosion resistance of the plate is stable. The Ecorr mean of the O-3 sample was-455.8 mV, slightly greater than O-1 and the test results were more stable. The Ecorr of sample O-2 was-437.8 mV with slight fluctuations in the test results. According to the meaning of the self-corrosion potential, the lower the potential is, the more corrosion is easy to occur, and the corrosion resistance of the plate is poorer, so that the overall corrosion resistance of the O-2 plate is better than that of O-1 and O-3. FIG. 2(b) is a jcorr calculation result and an error analysis of each sample of the O-state plate, wherein the jcorr mean values of O-1, O-2 and O-3 are 46.1875 μ A/cm2, 37.1924 μ A/cm2 and 37.9643 μ A/cm2 respectively, and the analysis and comparison show that compared with O-3, O-1 has high self-corrosion current density and high corrosion rate, but the test result is stable when the error is small; the O-3 self-corrosion current density is slightly larger than O-2, namely the corrosion rate of the whole O-2 plate is low, and the corrosion resistance is excellent.

Fig. 3 is the metallographic structure of the rolling face (RS) and cross section (HS) of the O-plate produced after casting, rolling and annealing. FIG. 3(a) shows that the grain structure in the O-1 plate material is recrystallized grains, small grains and grains having a slightly larger size coexist, the deformed structure is unevenly distributed when the deformed structure is not completely transformed into new, distortion-free isometric crystals, i.e., recrystallized nuclei, and the average size measured by the grain structure is 24.47. mu.m. The grain size and distribution of O-3 and O-1 are similar, and overall, the grain size is not uniform, the size grains are randomly distributed, and the average size of the grains is 23.64 mu m and is slightly smaller than O-1.

FIG. 3(c) is a distribution diagram of crystal grains in the O-2 rolling face, from which it can be seen that the crystal grains are fine and are distortion-free equiaxial crystals, and the average size of the crystal grains is 21.75 μm. Intergranular corrosion is measured by the depth of maximum corrosion penetration along the cross-section, and it is therefore necessary to study the cross-sectional grain structure of the three sheets. From the grain structures of the cross-sections of O-1 and O-3 in FIGS. 3(b) and (f), respectively, it can be seen from the grain distribution diagram of the O-3 plate that the size of No. 1 portion is larger than that of No. 2 portion, the size distribution is not uniform, but the overall grain size is smaller than O-1. FIG. 3(d) shows the grain structure of the cross section of O-2, and the fine recrystallization is uniformly distributed, compared with the O-1 and O-3, the grain size is small, and the distribution is more uniform. Therefore, the cross sections of the plates after different homogenization have different grain structures, and the differences result in different corrosion resistance of the plates.

It can be shown that, under the same rolling and annealing process conditions, the results of tests on intercrystalline corrosion, exfoliation corrosion and polarization curve of an O-state plate homogenized at 465 ℃ for 24h all show that the corrosion sensitivity is greater than that of an unhomogenized O-state plate, the corrosion resistance of the plate homogenized at 530 ℃ for 6h is optimal, and the intercrystalline corrosion and exfoliation corrosion of the three plates are in the form of pitting corrosion without forming intercrystalline network and exfoliation corrosion, so that the corrosion resistance sensitivity of the plate is high, and the requirement on the corrosion resistance of the ship plate is met.

All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims

1. A cast ingot homogenizing method for improving corrosion resistance of a 5083 aluminum alloy plate is characterized by comprising the following steps:

step 1, cutting an ingot into blocks with the thickness of 510-520 mm;

step 2, then carrying out homogenization treatment on the ingot at the temperature of 500-530 ℃ for 4-6 h;

step 3, carrying out 3-4 times of hot rolling on the cast ingot at 510 ℃ to 8-9mm, and ensuring the temperature to be higher than 360 ℃ in the whole hot processing process;

step 4, performing cold rolling with low deformation for five passes, wherein the cold rolling deformation is 45% -55%, and the thickness of the rolled aluminum plate is 4 mm;

and 5, after cold rolling, annealing the material, and annealing at the temperature of 500-510 ℃ for 3 hours to obtain the O-state plate of the 5083 aluminum alloy with high corrosion resistance.