An aluminum alloy having high resistance to pitting corrosion, a method for producing the same, and an aluminum alloy product

Abstract

The application provides an aluminum alloy with high pitting corrosion resistance, comprising: Si 0-0.10wt% and not equal to 0; Fe 0-0.20wt% and not equal to 0; Cu 0-0.01wt% and not equal to 0; Mn 1.1-1.2wt%; Mg 0-0.01wt% and not equal to 0; Cr 0-0.15wt% and not equal to 0; Ni 0-0.01wt% and not equal to 0; Zn 0-0.2wt% and not equal to 0; Ti 0-0.02wt% and not equal to 0; and the balance being Al. The application also provides a preparation method of the aluminum alloy. The aluminum alloy provided by the application has good corrosion resistance by reducing the content of Fe and Si, appropriately increasing the content of Cu, Mg, Cr, Ti, Ni and other elements, reducing the generation of harmful second phases, reducing the area percentage, reducing the generation of pitting corrosion, promoting the conversion of pitting corrosion into uniform corrosion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy, in particular to a high-point corrosion resistant aluminum alloy and a preparation method thereof and an aluminum alloy product. BACKGROUND

[0002] Copper is widely used in the evaporator, condenser and indoor and outdoor machine connecting pipe of heat exchanger in air conditioning industry due to its excellent electrical conductivity, thermal conductivity and long service life. With the shortage of copper resources and the continuous rise of copper price, the cost of air conditioning enterprises increases dramatically. In order to reduce the cost of air conditioning and effectively utilize natural resources, the air conditioning industry breaks the dependence on copper resources by using aluminum pipe instead of copper pipe in heat exchanger, evaporator and radiator.

[0003] Among the aluminum alloy series, 3 series aluminum alloy has good corrosion resistance, electrical conductivity, thermal conductivity, weldability and machinability, and is favored in the air conditioning field. The 3003, 3103 and other 3 series aluminum alloy pipes widely used in air conditioning heat exchangers are facing various service environments. In harsh working environment, ordinary aluminum pipes are easily corroded. With the aggravation of corrosion depth, the aluminum pipe is prone to perforation corrosion, that is, corrosion from the surface of the aluminum pipe to the inside, which is called pitting corrosion, and can cause refrigerant leakage and heat exchanger scrap.

[0004] The service life of copper pipe used in air conditioning heat exchanger can reach more than 10 years, while the service life of aluminum pipe is less than 1 year. In addition, according to the industry requirements, the SWAAT salt spray corrosion is currently mainly used to evaluate the corrosion resistance of aluminum pipe. The SWAAT salt spray corrosion resistance time of ordinary 3003 aluminum alloy is about 700h, and the SWAAT salt spray corrosion resistance time of 3103 aluminum alloy is only about 400h. With the increasing demand of customers for corrosion resistance of air conditioner, the existing aluminum pipe is difficult to meet the actual needs of enterprises, and it is urgent to provide an aluminum pipe with high pitting corrosion resistance. SUMMARY

[0005] The technical problem solved by the present application is to provide an aluminum alloy with high pitting corrosion resistance. The aluminum alloy provided by the present application has good mechanical properties and corrosion resistance.

[0006] Therefore, the present application provides an aluminum alloy with high pitting corrosion resistance, which comprises:

[0007] Si 0~0.10wt% and not equal to 0;

[0008] Fe 0~0.20wt% and not equal to 0;

[0009] Cu 0~0.01wt% and not equal to 0;

[0010] Mn 1.1~1.2wt%.

[0011] Mg 0~0.01wt% and not equal to 0;

[0012] Cr 0~0.15wt% and not equal to 0;

[0013] Ni 0~0.01wt% and not equal to 0;

[0014] Zn 0~0.2wt% and not equal to 0;

[0015] Ti 0~0.02wt% and not equal to 0;

[0016] Zr 0~0.10wt%;

[0017] the balance being Al.

[0018] Preferably, the content of Cu is 0~0.005wt%, the content of Cr is 0~0.10wt%, the content of Zn is 0~0.05wt%, and the content of Zr is 0.

[0019] Preferably, the content of Si is 0~0.05wt%, the content of Fe is 0~0.10wt%, the content of Cu is 0~0.005wt%, the content of Cr is 0~0.10wt%, the content of Zn is 0~0.05wt%, and the content of Zr is 0.

[0020] Preferably, the content of Si is 0~0.05wt%, the content of Fe is 0~0.10wt%, the content of Cu is 0~0.005wt%, the content of Cr is 0~0.10wt%, the content of Zn is 0~0.05wt%, and the content of Zr is 0~0.10wt% and not equal to 0.

[0021] Preferably, the content of Si is 0.04~0.09wt%, and / or, the content of Fe is 0.07~0.16wt%, and / or, the content of Cu is 0.002~0.008wt%.

[0022] Preferably, the content of Mn is 1.12~1.17wt%, and / or, the content of Mg is 0.002~0.007wt%, and / or, the content of Cr is 0.07~0.14wt%.

[0023] Preferably, the content of Ni is 0.002~0.008wt%, and / or, the content of Zn is 0.002~0.180wt%, and / or, the content of Ti is 0.013~0.016wt%, and / or, the content of Zr is 0~0.081wt%.

[0024] The application also provides a preparation method of the aluminum alloy, comprising the following steps:

[0025] mixing the aluminum raw material, the copper raw material, the magnesium raw material, the nickel raw material and the zinc raw material and heating to melting to obtain a molten liquid one;

[0026] removing slag from the molten liquid one to obtain a molten liquid two;

[0027] adding iron, manganese, titanium, chromium and zirconium into the molten liquid two to obtain a molten liquid three;

[0028] refining the molten liquid three, removing slag and gas to obtain a molten liquid four;

[0029] casting the molten liquid four and homogenizing to obtain an aluminum alloy.

[0030] Preferably, the temperature of the melting is 730-760℃, the temperature of the molten liquid two is 730-760℃, the temperature of the molten liquid three is 750-790℃, the temperature of the molten liquid four is 740-770℃, argon is introduced to remove gas before casting, and aluminum-titanium-boron wire is added to remove gas again; the temperature of the homogenizing is 590-620℃, and the holding time is 10-12h.

[0031] The application also provides an aluminum alloy product prepared from the aluminum alloy or prepared by the preparation method.

[0032] The application provides an aluminum alloy with high point corrosion resistance, which comprises: Si 0-0.10wt% and not equal to 0; Fe 0-0.20wt% and not equal to 0; Cu 0-0.01wt% and not equal to 0; Mn 1.1-1.2wt%; Mg 0-0.01wt% and not equal to 0; Cr 0-0.15wt% and not equal to 0; Ni 0-0.01wt% and not equal to 0; Zn 0-0.2wt% and not equal to 0; Ti 0-0.02wt% and not equal to 0; Zr 0-0.10wt%; and the balance is Al. The aluminum alloy provided by the application can reduce the generation of harmful second phases, reduce the second phase area percentage, reduce the generation of point corrosion of the aluminum alloy, promote the point corrosion to be converted into uniform corrosion, and improve the corrosion performance of the aluminum alloy by reducing the content of Fe and Si and appropriately increasing the content of Cu, Mg, Cr, Ti, Ni and the like; meanwhile, the mechanical properties of the aluminum alloy are improved by adjusting the content of each element in the aluminum alloy; further, the alloy elements in the aluminum alloy can be diffused by homogenizing treatment, the second phases can be uniformly distributed in the grains, the possibility of local concentration difference in the alloy is reduced, and the uniformity and stability of the aluminum alloy are improved. Experimental results show that the aluminum alloy provided by the application has good strength and plasticity, the tensile strength is 110-130MPa, the yield strength is 60-70MPa, and the elongation is ≥40%; the salt spray corrosion resistance of the aluminum alloy provided by the application is ≥1000h. BRIEF DESCRIPTION OF DRAWINGS

[0033] Si Corrosion depth photos of the aluminum alloy pipe prepared for the present application comparative example 1 and comparative example 2 after corrosion;

[0034] Fe Corrosion depth photos of the aluminum alloy pipe prepared for the present application example 1 after corrosion;

[0035] Cu Second phase organization observation photos of the aluminum alloy pipe prepared for the present application comparative example 1 and comparative example 2;

[0036] Mn Second phase organization observation photos of the aluminum alloy pipe prepared for the present application example;

[0037] Mg Second phase area percentage statistical column chart of the aluminum alloy pipe prepared for the present application example and comparative example;

[0038] Ni Second phase organization energy spectrum analysis of the aluminum alloy pipe prepared for the present application comparative example 1;

[0039] Zn Second phase organization energy spectrum analysis of the aluminum alloy pipe prepared for the present application comparative example 2;

[0040] Ti Second phase organization energy spectrum analysis of the aluminum alloy pipe prepared for the present application example. DETAILED DESCRIPTION

[0041] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not limitations to the claims of the present application.

[0042] In view of the problem that the mechanical properties and corrosion resistance of the aluminum alloy product in the prior art cannot meet the actual needs of enterprises, the present application discloses an aluminum alloy with high point corrosion resistance, which adjusts the types and contents of alloying elements, reduces the number of harmful second phases, reduces the generation of point corrosion, promotes the conversion of point corrosion into uniform corrosion, and makes the aluminum alloy have both mechanical properties and corrosion resistance; specifically, the present application example discloses that Si is 0~0.10wt% and not equal to 0;

[0043] Fe is 0~0.20wt% and not equal to 0;

[0044] Cu is 0~0.01wt% and not equal to 0;

[0045] Mn is 1.1~1.2wt%;

[0046] Mg 0~0.01wt% and not equal to 0;

[0047] Cr 0~0.15wt% and not equal to 0;

[0048] Ni 0~0.01wt% and not equal to 0;

[0049] Zn 0~0.2wt% and not equal to 0;

[0050] Ti 0~0.02wt% and not equal to 0;

[0051] Zr 0~0.10wt%;

[0052] The balance is Al.

[0053] The aluminum alloy provided in this application specifically includes: Si: 0~0.10wt%, Fe: 0~0.20wt%, Cu: 0~0.01wt%, Mn: 1.1~1.2wt%, Mg: 0~0.01wt%, Cr: 0~0.15wt%, Ni: 0~0.01wt%, Zn: 0~0.2wt%, Mg: 0~0.02wt%, Zr=0, and the balance is Al.

[0054] Specifically, it includes: Si: 0~0.10wt%, Fe: 0~0.20wt%, Cu: 0~0.005wt%, Mn: 1.1~1.2wt%, Mg: 0~0.01wt%, Cr: 0~0.10wt%, Ni: 0~0.01wt%, Zn: 0~0.05wt%, Ti: 0~0.02wt%, Zr=0, and the balance is Al.

[0055] Specifically, it includes: Si: 0~0.05wt%, Fe: 0~0.10wt%, Cu: 0~0.005wt%, Mn: 1.1~1.2wt%, Mg: 0~0.01wt%, Cr: 0~0.10wt%, Ni: 0~0.01wt%, Zn: 0~0.05wt%, Ti: 0~0.02wt%, Zr=0wt%, with the balance being Al.

[0056] Specifically, it includes: Si: 0~0.05wt%, Fe: 0~0.10wt%, Cu: 0~0.005wt%, Mn: 1.1~1.2wt%, Mg: 0~0.01wt%, Cr: 0~0.10wt%, Ni: 0~0.01wt%, Zn: 0~0.05wt%, Ti: 0~0.02wt%, Zr: 0~0.10wt%, with the balance being Al.

[0057] Furthermore, the Si content is 0.04~0.09 wt%, specifically, the Si energy is 0.05~0.08 wt%. The Fe content is 0.07~0.16 wt%, specifically, the Fe content is 0.09~0.15 wt%. The Cu content is 0.002~0.008 wt%, specifically, the Cu content is 0.003~0.006 wt%. The Mn content is 1.12~1.17 wt%, specifically, the Mn content is 1.13~1.16 wt%. The Mg content is 0.002~0.007 wt%, specifically, the Mg content is 0.003~0.006 wt%. The Cr content is 0.07~0.14 wt%, specifically, the Cr content is 0.09~0.12 wt%. The Ni content is 0.002~0.008 wt%, specifically, the Ni content is 0.003~0.005 wt%. The Zn content is 0.002~0.180wt%, specifically 0.005~0.120wt%. The Ti content is 0.013~0.016wt%, specifically 0.014~0.015wt%. The Zr content is 0~0.081wt%.

[0058] This application also provides a method for preparing the above-mentioned aluminum alloy, which includes the following steps: melting → online degassing → casting → homogenization → casting rod.

[0059] The aluminum ingot and the master alloy are heated to melt to obtain molten liquid one;

[0060] After removing the slag from the first melt, the second melt is obtained;

[0061] Iron, manganese, titanium, chromium, and zirconium are added to the second melt to obtain the third melt;

[0062] After refining the molten liquid three times, slag and gas were removed to obtain molten liquid four times;

[0063] The molten metal is cast into a homogenized state to obtain an aluminum alloy.

[0064] In the above-mentioned aluminum alloy preparation process, the melting temperature is 730~760℃, the temperature of the second melt is 730~760℃, the temperature of the third melt is 750~790℃, and the temperature of the fourth melt is 740~770℃. Before casting, argon gas is introduced for degassing, and then aluminum-titanium-boron wire is added for further degassing. The homogenization treatment temperature is 590~620℃, and the holding time is 10~12h; specifically, the homogenization temperature is 600~610℃, and the holding time is 10~11h.

[0065] Furthermore, the specific method for preparing the aluminum alloy is as follows:

[0066] S1) Mix aluminum, copper, magnesium, nickel and zinc raw materials and put them into a furnace and heat them to 730~760℃ to melt them to obtain molten liquid one;

[0067] S2) Sprinkle the slag remover evenly into the molten liquid and stir for 5-10 minutes. Then remove the slag from the surface of the aluminum liquid to obtain molten liquid two.

[0068] S3) Control the temperature of the second melt to 730~760℃, then add iron, manganese, titanium, chromium and zirconium to the second melt and stir for 10~15min to obtain the third melt;

[0069] S4) Control the temperature of the third melt to 750~790℃, then add refining agent to the third melt, stir and remove the slag, and pass pure argon gas to degas for 15~20 minutes. After standing for 50~60 minutes, remove the slag on the surface of the liquid to obtain the fourth melt.

[0070] S5) Control the temperature of the molten liquid four to 740~770℃, introduce pure argon gas to degas for 10 minutes, add aluminum titanium boron wire, melt it, degas it again for 5 minutes, and then filter the molten liquid through a preheated filter box so that it enters the casting system for casting to obtain ingots.

[0071] S6) Cut the ingot into short aluminum alloy round casting rods, heat them in a soaking furnace to 590~620℃, hold for 10~12h, and air cool.

[0072] This application also provides an aluminum alloy article prepared from the aluminum alloy described in the above scheme.

[0073] In the aluminum alloy provided in this application, by reducing the content of Fe and Si and appropriately increasing the content of elements such as Cu, Mg, Cr, Ti, and Ni, the generation of harmful second phases is reduced, their area percentage is decreased, pitting corrosion is reduced, and the transformation of pitting corrosion into uniform corrosion is promoted. At the same time, the zinc content is reduced and the rare earth element zirconium is increased. In the production process, the process steps and process parameters are optimized, and the alloying elements in the aluminum alloy can be diffused through homogenization treatment, so that the second phase is evenly distributed in the grains, reducing the possibility of local concentration differences in the alloy, which helps to improve the uniformity and stability of the alloy.

[0074] To further understand the present invention, the following detailed description of the highly pitting corrosion resistant aluminum alloy provided by the present invention is provided in conjunction with embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0075] The salt spray corrosion resistance tests in the following examples were conducted in accordance with the "Standard Operating Procedure for Salt Spray Testing after Modification of ASTM G85-2011 and its Appendix A3 Seawater Acidification Cyclic Test".

[0076] Example

[0077] S1) Raw materials such as aluminum ingots and intermediate alloys are put into the furnace and heated to 760°C to melt them, resulting in molten liquid one;

[0078] S2) Sprinkle the slag remover evenly into the melt and stir for 8 minutes. Then remove the slag from the surface of the melt to obtain melt two.

[0079] S3) Control the temperature of the second melt to 760℃, then add iron, manganese, titanium, chromium and zirconium to the second melt and stir for 12 minutes to obtain the third melt;

[0080] S4) Control the temperature of molten liquid three to 790℃, then add refining agent to molten liquid three, stir and remove slag, and pass pure argon gas to remove gas for 20 minutes. After standing for 60 minutes, remove the slag on the liquid surface to obtain molten liquid four.

[0081] S5) Control the temperature of the molten liquid to 770℃, introduce pure argon gas to degas for 10 minutes, add aluminum titanium boron wire, melt it, degas for another 5 minutes, and then filter the molten liquid through a preheated filter box so that it enters the casting system for casting to obtain an ingot.

[0082] S6) The ingot is cut into short aluminum alloy round casting rods, heated to 620°C in a soaking furnace, held for 12 hours, and air-cooled to obtain aluminum alloy ingots. Then, it is drawn by extrusion, thread forming and other processes to obtain aluminum alloy tubes.

[0083] The aluminum alloys provided in the examples and comparative examples were prepared according to the above method. Table 1 is a composition data table of the four aluminum alloys designed in this invention, and Table 2 is a chemical composition data table of 3003 aluminum alloy and 3103 aluminum alloy.

[0084] Table 1. Composition data of the four alloys in the examples.

[0085] Example 1 Balance Example 2 Balance Example 3 Cr Balance Example 4 Balance Zr Al Si 0.091 0.158 0.008 1.125 0.007 0.142 0.008 0.198 0.016 _ Fe Cu 0.087 0.152 0.006 1.138 0.003 0.094 0.005 0.005 0.015 _ Mn Mg 0.045 0.078 0.002 1.169 0.006 0.082 0.003 0.003 0.013 _ Zn Comparative Example 1 0.039 0.074 0.002 1.156 0.002 0.076 0.002 0.002 0.016 0.081 Balance

[0086] Table 2. Composition data of the two alloys in the comparative example.

[0087] Comparative Example 2 Balance Example Tensile strength / Mpa Yield strength / Mpa Cr Elongation / % Al Salt spray corrosion resistance / h 0.518 0.586 0.154 1.52 - - 0.115 Example 1 Example 2 0.527 0.697 0.101 1.47 0.304 0.112 0.203 Example 3

[0088] The performance of the aluminum alloy tubes prepared in the above embodiments and comparative examples was tested, and the results are shown in Table 3. Table 3 is a data table of mechanical properties and corrosion resistance of the aluminum alloy tubes prepared in the embodiments.

[0089] Table 3. Mechanical and corrosion resistance data of the aluminum alloy tubes provided in the embodiments.

[0090] Example 4 Alloy Salt spray corrosion resistance / h Example 1 Example 2 Example 3 112 67 44 1000 Example 4 116 61 46 1300 Comparative Example 1 114 60 48 1650 Comparative Example 2 120 64 47 1800

[0091] As shown in Table 3, the aluminum alloy tubes prepared in the examples have a tensile strength of 110~120 MPa, a yield strength of ≥60 MPa, an elongation of ≥40%, and a corrosion resistance of 1000~2000 h.

[0092] The corrosion resistance of the aluminum alloy tubes prepared in the examples was compared with that of the aluminum alloy tubes prepared in the comparative examples, as shown in Table 4.

[0093] Table 4. Comparison of corrosion resistance data of aluminum alloy tubes prepared in the examples and comparative examples.

[0094] Figure 1 Figure 2 Figure 1 1000 Figure 1 1300 Figure 2 1650 Figure 1 1800 Figure 2 700 Figures 3~5 500

[0095] As can be seen from Table 4, the aluminum alloy tube prepared by this invention has better corrosion resistance than the comparative example.

[0096] The aluminum alloy tube prepared in Example 1 of this invention was subjected to corrosion evaluation tests with the aluminum alloy tubes prepared in Comparative Examples 1 and 2, and the depth of their corrosion pits was compared. Figure 3 and Figure 4 As shown.

[0097] Figure 5 The images show the corrosion depth of the aluminum alloy tubes after corrosion, as prepared for Comparative Example 1 (left) and Comparative Example 2 (right). Figure 5 It can be seen that the corrosion depths of the aluminum alloy tubes prepared in Comparative Example 1 and Comparative Example 2 are 363.77 μm and 457.1 μm, respectively. Figures 6~8 The aluminum alloy tube prepared in Example 1 had a corrosion depth of 86.83 μm after corrosion; from Figures 6 to 8 and ​ It can be observed that the corrosion of the aluminum alloy tube prepared in the comparative example is pitting corrosion, while the corrosion of the aluminum alloy tube prepared in the embodiment of the present invention is uniform corrosion.

[0098] To further investigate the corrosion mechanism of the aforementioned aluminum alloy tube, a second-phase microstructure analysis was performed on the tube. ​ As shown. ​ These are photographs showing the second-phase microstructure of aluminum alloy tubes prepared for Comparative Example 1 (left) and Comparative Example 2 (right). ​ The images show the microstructure of the second phase of the aluminum alloy tube prepared in Example 1; quantitative statistics were performed on the second phase of the aluminum alloy tubes prepared in Example 1 and the comparative example, such as... ​ As shown; from ​ It can be seen that the percentage of the second phase area for each alloy is: Comparative Example 2 > Comparative Example 1 > Example 1.

[0099] Further investigation was conducted on the elemental content of the second phase. Scanning energy dispersive spectroscopy (EDS) analysis was performed on the aluminum alloy tubes prepared in Comparative Example 1, Comparative Example 2, and Example 1, respectively. ​ As shown; from ​It was observed that the second phases of the aluminum alloy tube prepared in Example 1 and the aluminum alloy tube prepared in Comparative Example 1 were AlFeMnSi and AlFeMnSiCr, and there were significant differences in their quantity and size morphology.

[0100] In summary, the large area percentage and coarse size of the AlFeMnSi(Cr) second phase provide a path for the propagation of pitting corrosion in aluminum alloys, accelerating the pitting corrosion of aluminum alloys; while the aluminum alloy products prepared by the present invention have fewer second phases and more rounded morphology, which promotes the transformation of aluminum alloys from pitting corrosion to uniform corrosion during the corrosion process.

[0101] Compared with existing 3-series aluminum alloys, the aluminum alloy products prepared by this invention take into account the mechanical properties of the alloy and improve its corrosion resistance, which is conducive to promoting the use of aluminum alloy pipes in air conditioning heat exchangers.

[0102] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0103] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An aluminum alloy with high resistance to pitting corrosion, comprising: Si 0.039~0.09wt%; Fe 0.07~0.16wt%; Cu 0.002~0.006wt%; Mn 1.12~1.17wt%; Mg 0.002~0.006wt%; Cr 0.07~0.10wt%; Ni 0.002~0.005wt%; Zn 0.002~0.005wt%; Ti 0.013~0.015wt%; Zr 0 or 0.081 wt%; The balance is Al.

2. The aluminum alloy according to claim 1, characterized in that, The Si content is 0.04~0.09wt%.

3. An aluminum alloy product, prepared from the aluminum alloy according to any one of claims 1 to 2.

Images