Aluminum alloy profile and sensitization repair process thereof

Abstract

The invention relates to an aluminum alloy profile and a sensitization repair process thereof, and belongs to the field of metal material heat treatment processing. According to the process, a cast ingot is subjected to two-stage homogenization treatment; extruding the homogenized cast ingot to obtain a pipe; the obtained pipe is subjected to cold machining; the pipe subjected to cold machining is subjected to sensitization treatment, and the sensitization degree of the pipe is larger than 25 mg / cm < 2 >; and finally, sensitization repair treatment is conducted, and the aluminum alloy profile is obtained. The technology comprises the steps of two-stage homogenization treatment, extrusion, cold machining, sensitization, sensitization repair treatment and the like, the sensitization degree of the aluminum alloy profile can be reduced to be smaller than 7 mg / cm < 2 >, the sensitization time can be prolonged, the performance of the aluminum alloy profile is guaranteed, the tensile strength is made to be 380 MPa or above, the yield strength is made to be 210 MPa or above, and the percentage elongation after fracture is made to be 10% or above.

Description

Technical Field

[0001] The invention relates to the field of heat treatment of metal materials, and in particular to an aluminum alloy profile and a sensitization repair process thereof. Background Art

[0002] With the rapid development of the shipbuilding industry, the demand for small and medium-sized yachts, passenger ships and light alloy high-speed ships has increased dramatically, and the corresponding requirements for ship lightweight and speed have become increasingly higher. Compared with other non-ferrous metals, steel, etc., aluminum alloy profiles have the characteristics of low density, good plasticity and processing ability, and are increasingly widely used in the shipbuilding industry, such as ship hulls, marine superstructures, various facilities or pipelines, etc.

[0003] In order to improve the strength and corrosion resistance of aluminum alloy profiles, Mg is often added to the aluminum alloy. However, Mg will cause magnesium to spontaneously precipitate in the form of β phase (called sensitization), especially when the Mg content is above 5%, the sensitization is more serious. Since the β phase is continuously distributed along the grain boundary, once intergranular corrosion occurs to a certain extent, it will cause severe exfoliation corrosion, posing a huge safety hazard. In order to reduce the sensitization degree, existing research mainly controls the sensitization degree of aluminum alloy profiles to 25mg / cm by adding alloying elements, such as Ag, or annealing. 2 the following.

[0004] However, high-magnesium aluminum alloy profiles (Mg ≥ 5%) can spontaneously sensitize at room temperature. After being placed for a period of time (for example, more than 20 natural months), the sensitization degree gradually exceeds 25 mg / cm 2 , so the performance of its aluminum alloy profiles is seriously affected. Summary of the invention

[0005] In view of the above analysis, the present invention aims to provide an aluminum alloy profile and a sensitization repair process thereof, so as to extend the sensitization time of the aluminum alloy profile and ensure the performance of the aluminum alloy profile.

[0006] In one aspect, the present invention provides a sensitization repair process for an aluminum alloy profile, comprising the following steps:

[0007] S1: subjecting the ingot to a two-stage homogenization treatment;

[0008] S2: Extruding the homogenized ingot to obtain a tube;

[0009] S3: cold working the obtained pipe;

[0010] S4: The cold-worked pipe is sensitized to a sensitization degree greater than 25 mg / cm 2 ;

[0011] S5: Finally, a sensitization repair process is performed to obtain an aluminum alloy profile.

[0012] Furthermore, in the double-stage homogenization treatment, the temperature of the first stage homogenization treatment is 474-480°C; and the temperature of the second stage homogenization treatment is 494-500°C.

[0013] Furthermore, in step S2, before extrusion, the extrusion barrel, the mold and the ingot need to be preheated;

[0014] The preheating temperature of the extrusion barrel is 400-460°C, and the heating rate is 80-120°C / h; the preheating temperature of the mold is 440-480°C, and the heating rate is 80-200°C / h; the preheating temperature of the ingot is 460-480°C, and the heating rate is 40-80°C / h.

[0015] Further, in step S2, the extrusion process is divided into an upsetting stage, a breakthrough stage, a stabilization stage, and a finishing stage;

[0016] The extrusion speed in the upsetting stage is 0.4-0.7 mm / s, the extrusion speed in the breakthrough stage is 0.1-0.3 mm / s, the extrusion speed in the stabilization stage is 0.6-1.0 mm / s, and the extrusion speed in the finishing stage is 0.2-0.4 mm / s.

[0017] Furthermore, in step S3, the cold working is tension stretching, wherein the permanent plastic deformation rate is 1.5-3.0%; and the stretching speed is 5-10 mm / s.

[0018] Furthermore, the sensitization treatment is natural sensitization or accelerated sensitization; the temperature of the accelerated sensitization is 150-200°C.

[0019] Furthermore, the heating temperature of the sensitization repair treatment is 265-285° C., and the insulation time is 25-35 minutes.

[0020] Furthermore, the sensitization degree of the aluminum alloy profile is less than 7 mg / cm 2 .

[0021] Furthermore, the chemical composition of the aluminum alloy profile, in terms of weight percentage, includes Si<0.3%; Fe<0.3; Cu<0.1%; Mn: 0.7%-1.1%; Mg: 5.5%-6.5%; Zn<0.1%; Zr: 0.02%-0.12%; Sc: 0.01%-0.02%.

[0022] On the other hand, the present invention provides an aluminum alloy profile obtained by the sensitization repair process described in the present invention.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. The present invention provides a sensitization repair process for aluminum alloy profiles, which includes the steps of two-stage homogenization treatment, extrusion, cold working, sensitization and sensitization repair treatment, which can not only reduce the sensitization degree of aluminum alloy profiles to less than 7 mg / cm 2 , and can also prolong the sensitization time to ensure the performance of aluminum alloy profiles, so that the tensile strength is above 380MPa, the yield strength is above 210MPa, and the elongation after fracture is above 10%;

[0025] 2. In the double-stage homogenization treatment of the present invention, the temperature of the first-stage homogenization treatment is 474-480°C; the temperature of the second-stage homogenization treatment is 494-500°C. During the double-stage homogenization process, Mn-containing phases and Al3Sc phases are precipitated. These precipitated phases will also precipitate at the grain boundaries. During the sensitization repair process, the β phase will melt back and the Mn phase and Al3Sc phase will recrystallize and grow at the same time, which will cause the grain boundaries to be occupied by the growing Mn phase and Al3Sc phase. In this way, in the subsequent sensitization process, the β phase cannot be enriched at the grain boundaries, thereby extending the sensitization time.

[0026] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings are only for the purpose of illustrating specific embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0028] Figure 1 This is a photo of the corrosion depth of the aluminum alloy profile obtained in Example 1;

[0029] Figure 2 This is a photo of the corrosion depth of the aluminum alloy profile obtained in Comparative Example 4. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0031] With the rapid development of the shipbuilding industry, the demand for small and medium-sized yachts, passenger ships and light alloy high-speed ships has increased dramatically, and the corresponding requirements for ship lightweight and speed have become increasingly higher.

[0032] Currently in the shipbuilding industry, aluminum alloy profiles are often used to replace the original steel materials. In order to improve the strength and corrosion resistance of aluminum alloy profiles, Mg is often added to the aluminum alloy. However, Mg will cause magnesium to spontaneously precipitate in the form of β phase (called sensitization), especially when the Mg content is above 5%, the sensitization is more serious.

[0033] In order to reduce the sensitization, existing research mainly controls the sensitization of aluminum alloy profiles to 25 mg / cm by adding alloying elements such as Ag or annealing. 2 However, high-magnesium aluminum alloy profiles (Mg ≥ 5%) can spontaneously sensitize at room temperature. After being placed for a period of time (for example, more than 20 natural months), the sensitization degree gradually exceeds 25 mg / cm 2 , so the performance of its aluminum alloy profiles is seriously affected.

[0034] The present invention provides a sensitization repair process for an aluminum alloy profile, comprising the following steps:

[0035] S1: subjecting the ingot to a two-stage homogenization treatment;

[0036] S2: Extruding the homogenized ingot to obtain a tube;

[0037] S3: cold working the obtained pipe;

[0038] S4: The cold-worked pipe is subjected to natural sensitization or accelerated sensitization to make its sensitization degree greater than 25 mg / cm 2 ;

[0039] S5: Finally, a sensitization repair process is performed to obtain an aluminum alloy profile.

[0040] Compared with the prior art, the preparation of the aluminum alloy profile of the present invention includes two-stage homogenization treatment, extrusion, cold working, sensitization and sensitization repair treatment, which can not only reduce the sensitization degree of the aluminum alloy profile to less than 7 mg / cm 2 It can also prolong the sensitization time and ensure the performance of aluminum alloy profiles, so that the tensile strength is above 380MPa, the yield strength is above 210MPa, and the elongation after fracture is above 10%.

[0041] Specifically, in the double-stage homogenization treatment, the temperature of the first stage homogenization treatment is 474-480°C; the temperature of the second stage homogenization treatment is 494-500°C.

[0042] It should be noted that, in the present invention, the ingot is subjected to a two-stage homogenization treatment, which can fully diffuse the alloy atoms, make the ingot structure uniform, eliminate casting stress, reduce deformation resistance, and improve the resistance to exfoliation corrosion and intergranular corrosion.

[0043] In the present invention, the temperatures of the two-stage homogenization treatment cannot be interchanged, and the temperature of the first-stage homogenization must be lower than the temperature of the second-stage homogenization. The temperature of the first-stage homogenization treatment is 474-480°C; its purpose is to dissolve the Al3Mg2 phase back, but if it is higher than its temperature, it will cause the Al3Mg2 phase to coarsen rapidly, and the coarse Al3Mg2 phase will greatly reduce the mechanical properties of the material and cause the material's intergranular corrosion resistance to decrease. The temperature of the second-stage homogenization treatment is 494-500°C, and its purpose is to promote the precipitation of the manganese-containing phase, play a role in pinning the grain boundaries and improving the mechanical properties of the material; this temperature will also lead to the precipitation of Al3Zr and Al3Sc, and the rod-shaped Al3Zr phase will be interspersed between the grain boundaries, which plays a role in inhibiting recrystallization.

[0044] The double-stage homogenization treatment adopted in the present invention is completely different from the existing single-stage aging system at 490°C for 24 hours. The sensitization degree is generally 12 mg / cm 2 After double-stage homogenization treatment, the sensitization degree of aluminum alloy profiles is less than 7mg / cm 2 .

[0045] Specifically, in step S2, the extrusion barrel, the mold and the ingot need to be preheated before extrusion;

[0046] The preheating temperature of the extrusion barrel is 400-460°C, and the heating rate is 80-120°C / h; the preheating temperature of the mold is 440-480°C, and the heating rate is 80-200°C / h; the preheating temperature of the ingot is 460-480°C, and the heating rate is 40-80°C / h.

[0047] It should be noted that in the present invention, the ingot is a hollow cylindrical shape, and is prepared into a pipe by an extrusion process. First, the ingot is placed in a high-temperature electric furnace for heating and heat preservation. Then, the heating coil of the extrusion barrel is adjusted to a predetermined temperature. Finally, after the ingot is heated for 1 hour, the extruder is started and the mold is installed, and then the ingot is placed in the extrusion barrel for hot extrusion. Extrusion affects the quality of the pipe, especially its surface quality. When the extrusion temperature and the preheating temperature of the ingot are lower than the above temperature, more serious scratches and tiger skin problems will occur.

[0048] Specifically, the preheating temperature of the extrusion barrel may be 400° C., 410° C., 420° C., 430° C., 440° C., 450° C. or 460° C. The heating rate may be 80° C. / h, 90° C. / h, 100° C. / h, 110° C. / h or 120° C. / h.

[0049] Specifically, the preheating temperature of the mold can be 440°C, 450°C, 460°C, 470°C or 480°C, and the heating rate can be 80°C / h, 90°C / h, 100°C / h, 110°C / h, 120°C / h, 130°C / h, 140°C / h, 150°C / h, 160°C / h, 170°C / h, 180°C / h, 190°C / h or 200°C / h.

[0050] Specifically, the preheating temperature of the ingot may be 460° C., 470° C. or 480° C. The heating rate may be 40° C. / h, 50° C. / h, 60° C. / h, 70° C. / h or 80° C. / h.

[0051] Specifically, in step S2, the extrusion process is divided into an upsetting stage, a breakthrough stage, a stabilization stage, and a finishing stage;

[0052] The extrusion speed in the upsetting stage is 0.4-0.7 mm / s, the extrusion speed in the breakthrough stage is 0.1-0.3 mm / s, the extrusion speed in the stabilization stage is 0.6-1.0 mm / s, and the extrusion speed in the finishing stage is 0.2-0.4 mm / s.

[0053] It should be noted that during the extrusion process, the extrusion speed needs to be set reasonably, and the extrusion speed in each stage is slightly different. A faster extrusion speed can meet relatively high production efficiency.

[0054] Specifically, the extrusion speed in the upsetting stage may be 0.4 mm / s, 0.5 mm / s, 0.6 mm / s or 0.7 mm / s; the extrusion speed in the breakthrough stage may be 0.1 mm / s, 0.2 mm / s or 0.3 mm / s; the extrusion speed in the stabilization stage may be 0.6 mm / s, 0.7 mm / s, 0.8 mm / s, 0.9 mm / s or 1.0 mm / s; the extrusion speed in the finishing stage may be 0.2 mm / s, 0.3 mm / s or 0.4 mm / s.

[0055] Specifically, in step S3, the cold working is tension stretching, wherein the permanent plastic deformation rate is 1.5-3.0%; and the stretching speed is 5-10 mm / s.

[0056] It should be noted that after extrusion, tension stretching is required, and the permanent plastic deformation rate, stretching speed and tension need to be controlled to ensure the uniformity of deformation during the stretching process, thereby improving the mechanical properties of the resulting aluminum alloy profile. If the stretching rate is greater than 3%, the aluminum alloy profile will have large deformation in some areas and poor uniformity. The range of the tensile force value for stretching is: the tensile force is greater than the product of the yield strength of the material and the cross-sectional area of ​​the material, and the tensile force is less than the product of the tensile strength of the material and the cross-sectional area of ​​the material.

[0057] Specifically, the sensitization treatment is natural sensitization or accelerated sensitization.

[0058] Specifically, the conditions for natural sensitization are room temperature and constant humidity environment.

[0059] It should be noted that natural sensitization means that when the product is placed in the use environment (generally considered to be room temperature and constant humidity environment), the high Mg aluminum alloy will spontaneously transform from β' phase to β phase.

[0060] Specifically, the temperature for accelerated sensitization is 150-200°C.

[0061] It should be noted that the sensitization process of high Mg aluminum alloys occurs rapidly above 150°C, while the accelerated sensitization process for related products is usually carried out between 150 and 200°C. The higher the temperature, the shorter the time required. This process actually provides external energy to accelerate the transformation of β' phase to β phase.

[0062] Specifically, the heating temperature of the sensitization repair treatment is 265-285° C., and the insulation time is 25-35 minutes.

[0063] It should be noted that after sensitization repair treatment, a large amount of β precipitated phase at the grain boundary is dissolved. After repair, the β phase at the grain boundary of the profile is dissolved, no longer causing intergranular corrosion, and restored to the level before sensitization, and the sensitization time can be extended.

[0064] The accelerated sensitization process accelerates the transformation of the β' phase to the β phase by providing external energy, while the sensitization repair treatment raises the temperature to the dissolution temperature of the β phase to melt it back into the matrix.

[0065] During the two-stage homogenization process, Mn phase and Al3Sc phase are precipitated, and these precipitated phases will also precipitate at the grain boundaries. During the sensitization repair process, the β phase will melt back and the Mn phase and Al3Sc phase will recrystallize and grow at the same time, which will cause the grain boundaries to be occupied by the growing Mn phase and Al3Sc phase. In this way, in the subsequent sensitization process, the β phase cannot be enriched at the grain boundaries, thereby extending the sensitization time.

[0066] Specifically, the chemical composition of the aluminum alloy profile, by weight percentage, includes Si<0.3%; Fe<0.3; Cu<0.1%; Mn: 0.7%-1.1%; Mg: 5.5%-6.5%; Zn<0.1%; Zr: 0.02%-0.12%; Sc: 0.01%-0.02%.

[0067] It should be noted that the elements have the following functions:

[0068] Mg: The increase of Mg content is significantly related to the increase of intergranular corrosion sensitivity of the alloy. As the Mg content in the alloy increases, the strength of the alloy gradually increases. Although high Mg content will increase the strength of the alloy, it will also make the processing performance of the alloy worse. At the same time, excessive Mg elements will lead to the precipitation of Al3Mg2 phase, and the strength, plasticity and corrosion resistance of the alloy will be greatly reduced.

[0069] Mn: Mn can increase the recrystallization temperature of the alloy and coarsen the grain size, which can improve the stability of the alloy in high-temperature service environment to a certain extent. At the same time, Mn can slightly increase the strength of the alloy, especially the yield strength.

[0070] Si and Cu are both harmful impurities. Too high Si content will lead to a decrease in the plasticity of the alloy; a small amount of copper will cause the corrosion resistance of the alloy to deteriorate; therefore, it is necessary to control Si < 0.3% and Cu < 0.1%.

[0071] Zn: Adding a small amount of Zn to high magnesium alloys can improve the tensile strength.

[0072] Zr and Sc: They mainly play the role of grain refinement, which can significantly improve the strength of the alloy and form Al3Zr and Al3Sc, thereby significantly improving the alloy's resistance to intergranular corrosion.

[0073] The present invention provides an aluminum alloy profile obtained by the sensitization repair process of the present invention. The obtained aluminum alloy profile has a low sensitization degree, and the sensitization degree is relatively low after being placed for a long period of time, and the performance is excellent, and can be used in the shipbuilding industry.

[0074] In order to more clearly describe the present invention, it is further illustrated by the following examples and comparative examples.

[0075] Example 1

[0076] The sensitization repair process of aluminum alloy profiles includes the following steps:

[0077] S1: subjecting the ingot to a two-stage homogenization treatment;

[0078] The chemical composition of the ingot, in terms of weight percentage, includes Si: 0.1%; Fe: 0.16%; Cu: 0.05%; Mn: 0.8%; Mg: 6.3%; Zn: 0.05%; Zr: 0.09%; Sc: 0.01%;

[0079] The temperature of the first stage homogenization treatment is 474℃, heating for 2h and keeping warm for 18h; the temperature of the second stage homogenization treatment is 494℃, heating for 30min, keeping warm for 6h, and cooling by air;

[0080] S2: Extruding the homogenized ingot to obtain a tube;

[0081] The preheating temperature of the extrusion barrel is 400°C, and the heating rate is 80°C / h; the preheating temperature of the mold is 440°C, and the heating rate is 80°C / h; the preheating temperature of the ingot is 460°C, and the heating rate is 40°C / h;

[0082] The extrusion process is divided into upsetting stage, breakthrough stage, stabilization stage and finishing stage;

[0083] The extrusion speed in the upsetting stage is 0.4 mm / s, the extrusion speed in the breakthrough stage is 0.1 mm / s, the extrusion speed in the stabilization stage is 0.6 mm / s, and the extrusion speed in the finishing stage is 0.2 mm / s.

[0084] S3: cold working the obtained pipe;

[0085] The cold working is tension stretching, wherein the permanent plastic deformation rate is 1.5%; the stretching speed is 5 mm / s;

[0086] S4: The cold-worked pipe is subjected to accelerated sensitization at a temperature of 150°C for 24 hours. The sensitization degree after sensitization is 46 mg / cm 2 ;

[0087] S5: Finally, a sensitization repair process is performed to obtain an aluminum alloy profile;

[0088] The heating temperature of the sensitization repair treatment is 265°C and the insulation time is 35 minutes.

[0089] Example 2

[0090] The preparation process of Example 2 is substantially the same as that of Example 1, except that

[0091] S1: subjecting the ingot to a two-stage homogenization treatment;

[0092] The chemical composition of the ingot, in terms of weight percentage, includes Si: 0.15%; Fe: 0.22%; Cu: 0.05%; Mn: 1.1%; Mg: 6.5%; Zn: 0.04%; Zr: 0.12%; Sc: 0.02%;

[0093] The temperature of the first stage homogenization treatment is 480℃, heating for 2h and keeping warm for 18h; the temperature of the second stage homogenization treatment is 500℃, heating for 30min, keeping warm for 6h, and cooling by air;

[0094] S2: Extruding the homogenized ingot to obtain a tube;

[0095] The preheating temperature of the extrusion barrel is 460°C, and the heating rate is 120°C / h; the preheating temperature of the mold is 480°C, and the heating rate is 200°C / h; the preheating temperature of the ingot is 480°C, and the heating rate is 80°C / h;

[0096] The extrusion process is divided into upsetting stage, breakthrough stage, stabilization stage and finishing stage;

[0097] The extrusion speed in the upsetting stage is 0.7 mm / s, the extrusion speed in the breakthrough stage is 0.3 mm / s, the extrusion speed in the stabilization stage is 1.0 mm / s, and the extrusion speed in the finishing stage is 0.4 mm / s.

[0098] S3: cold working the obtained pipe;

[0099] The cold working is tension stretching, wherein the permanent plastic deformation rate is 3.0%; the stretching speed is 10 mm / s;

[0100] S4: The cold-worked pipe is subjected to accelerated sensitization at a temperature of 200°C for 15 hours. The sensitization degree after sensitization is 53 mg / cm 2 ;

[0101] S5: Finally, a sensitization repair process is performed to obtain an aluminum alloy profile;

[0102] The heating temperature of the sensitization repair treatment is 270°C and the insulation time is 30 minutes.

[0103] Example 3

[0104] The preparation process of Example 3 is substantially the same as that of Example 2, except that, in Example 3, S1: performing a two-stage homogenization treatment on the ingot;

[0105] S2: Extruding the homogenized ingot to obtain a tube;

[0106] The preheating temperature of the extrusion barrel is 440°C, and the heating rate is 100°C / h; the preheating temperature of the mold is 460°C, and the heating rate is 120°C / h; the preheating temperature of the ingot is 470°C, and the heating rate is 60°C / h;

[0107] The extrusion process is divided into upsetting stage, breakthrough stage, stabilization stage and finishing stage;

[0108] The extrusion speed in the upsetting stage is 0.55 mm / s, the extrusion speed in the breakthrough stage is 0.2 mm / s, the extrusion speed in the stabilization stage is 0.8 mm / s, and the extrusion speed in the finishing stage is 0.3 mm / s.

[0109] S3: cold working the obtained pipe;

[0110] The cold working is tension stretching, wherein the permanent plastic deformation rate is 2.0%; the stretching speed is 7 mm / s;

[0111] S4: The cold-worked pipe is subjected to accelerated sensitization at a temperature of 180°C for 20 hours. The sensitization degree after sensitization is 50 mg / cm 2 ;

[0112] S5: Finally, a sensitization repair process is performed to obtain an aluminum alloy profile;

[0113] The heating temperature of the sensitization repair treatment is 285°C and the insulation time is 25 minutes.

[0114] Comparative Example 1

[0115] The preparation process of Comparative Example 1 is substantially the same as that of Example 1, except that in Comparative Example 1, a single-stage aging system is adopted in step S1, the heating temperature is 490° C., and the holding time is 24 h.

[0116] Comparative Example 2

[0117] The preparation process of Comparative Example 2 is substantially the same as that of Example 1, except that in step S5 of Comparative Example 2, the heating temperature of the sensitization repair treatment is 260°C.

[0118] Comparative Example 3

[0119] The preparation process of Comparative Example 3 is substantially the same as that of Example 1, except that in step S5 of Comparative Example 3, the heating temperature of the sensitization repair treatment is 300°C.

[0120] Comparative Example 4

[0121] The preparation process of Comparative Example 4 is substantially the same as that of Example 1, except that Comparative Example 4 does not include steps S4 and S5.

[0122] Performance Testing

[0123] The above Examples 1-3 and Comparative Examples 1-4 were subjected to sensitization tests and performance tests, mainly including tensile strength, yield strength and elongation after forging, and the test results are shown in Table 1;

[0124] One common test method for evaluating the sensitivity of aluminum alloys to intergranular corrosion is the nitric acid mass loss test (NAMLT), which is also called the Degree of Sensitization (DoS). If the alloy is "sensitized", the β phase will dissolve, corresponding to a higher weight loss measurement in concentrated nitric acid for 24 hours.

[0125] Table 1 Performance test results

[0126]

[0127] Combining Examples 1-3 and Comparative Examples 1-4 and referring to Table 1, it can be seen that the preparation of the aluminum alloy profile of the present invention includes two-stage homogenization treatment, extrusion, cold working, sensitization and sensitization repair treatment, which can not only reduce the sensitization degree of the aluminum alloy profile to less than 7 mg / cm 2 , ensuring the performance of aluminum alloy profiles, making the tensile strength above 380MPa, the yield strength above 210MPa, and the elongation after fracture above 16%.

[0128] Since the aluminum alloy profile of the present invention is mainly used in the shipbuilding industry and its main service environment is room temperature, the above-mentioned Examples 1-3 and Comparative Examples 1-4 were subjected to long-term, room temperature sensitization tests, and the specific test results are shown in Table 2.

[0129] Table 2 Sensitization test results at different time periods (unit: mg / cm 2 )

[0130] Group 3 months 6 months 9 months 12 months 15 months Example 1 4.62 4.92 5.02 5.36 5.34 Example 2 4.86 4.99 5.05 5.36 5.66 Example 3 5.12 5.17 5.35 5.74 5.84 Comparative Example 1 10.2 19.4 29.72 - - Comparative Example 2 9.82 16.4 25.66 - - Comparative Example 3 16.3 27.5 - - - Comparative Example 4 19.2 35.41 - - -

[0131] *“-” in Table 2 indicates that the sensitization degree is greater than 25 mg / cm 2 No further testing will be performed.

[0132] Combining Examples 1-3 and Comparative Examples 1-4 with Table 2, it can be seen that the aluminum alloy profiles prepared by the sensitization repair process provided by the present invention can prolong their sensitization time. After a long period of testing, the sensitization degree of the aluminum alloy profiles prepared by Examples 1-3 of the present invention is still 7 mg / cm after 15 months. 2 the following.

[0133] Combined with Example 1 and Comparative Example 4 and Figure 1 and Figure 2 As can be seen from the figure, the corrosion depth of the aluminum alloy profile obtained in Example 1 is 24.2 μm, and the corrosion depth of the aluminum alloy profile obtained in Comparative Example 4 is 37.6 μm, indicating that the performance of the aluminum alloy profile obtained in Example 1 is better, and its anti-sensitization or anti-corrosion performance is better.

[0134] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A sensitization repair process for aluminum alloy profiles, characterized in that: The following steps are involved: S1: subjecting the ingot to a two-stage homogenization treatment; S2: Extruding the homogenized ingot to obtain a tube; S3: cold working the obtained pipe; S4: The cold-worked pipe is sensitized to a sensitization degree greater than 25 mg / cm 2 ; S5: Finally, a sensitization repair process is performed to obtain an aluminum alloy profile.

2. The sensitization repair process for aluminum alloy profiles according to claim 1, characterized in that: In the double-stage homogenization treatment, the temperature of the first stage homogenization treatment is 474-480°C; the temperature of the second stage homogenization treatment is 494-500°C.

3. The sensitization repair process for aluminum alloy profiles according to claim 1, characterized in that: In step S2, before extrusion, the extrusion barrel, the mold and the ingot need to be preheated; The preheating temperature of the extrusion barrel is 400-460°C, and the heating rate is 80-120°C / h; the preheating temperature of the mold is 440-480°C, and the heating rate is 80-200°C / h; the preheating temperature of the ingot is 460-480°C, and the heating rate is 40-80°C / h.

4. The sensitization repair process for aluminum alloy profiles according to claim 1, characterized in that: In step S2, the extrusion process is divided into the upsetting stage, the breakthrough stage, the stabilization stage and the finishing stage; The extrusion speed in the upsetting stage is 0.4-0.7 mm / s, the extrusion speed in the breakthrough stage is 0.1-0.3 mm / s, the extrusion speed in the stabilization stage is 0.6-1.0 mm / s, and the extrusion speed in the finishing stage is 0.2-0.4 mm / s.

5. The sensitization repair process for aluminum alloy profiles according to claim 1, characterized in that: In step S3, the cold working is tension stretching, wherein the permanent plastic deformation rate is 1.5-3.0%; and the stretching speed is 5-10 mm / s.

6. The sensitization repair process for aluminum alloy profiles according to claim 1, characterized in that: The sensitization treatment is natural sensitization or accelerated sensitization; The temperature of the accelerated sensitization is 150-200°C.

7. The sensitization repair process for aluminum alloy profiles according to claim 1, characterized in that: The heating temperature of the sensitization repair treatment is 265-285° C., and the insulation time is 25-35 minutes.

8. The sensitization repair process for aluminum alloy profiles according to claim 1, characterized in that: The sensitization degree of the aluminum alloy profile is less than 7 mg / cm 2 .

9. The sensitization repair process for aluminum alloy profiles according to claim 1, characterized in that: The chemical composition of the aluminum alloy profile, in terms of weight percentage, includes Si < 0.3%; Fe < 0.3; Cu < 0.1%; Mn: 0.7%-1.1%; Mg: 5.5%-6.5%; Zn<0.1%; Zr：0.02％-0.12％； Sc: 0.01%-0.02%.

10. An aluminum alloy profile, characterized in that: Obtained by the sensitization repair process described in any one of claims 1-9.

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