A high magnesium zinc aluminum magnesium alloy for super-high corrosion resistant coating and a production method thereof

Abstract

The application discloses a high-magnesium zinc-aluminum-magnesium alloy for super-high corrosion-resistant plating layer and a production method thereof, and relates to the technical field of metal alloys.The high-magnesium zinc-aluminum-magnesium alloy comprises elements such as Zn, Al, Mg, Si, La and Ce, and the chemical components are as follows in percentage by weight: Al 15-30%, Mg 5-8%, Si 0.15-0.4%, La 0.01-0.05%, Ce 0.05-0.2%, and the balance of Zn and inevitable impurities.The alloy comprises Ce and CeO2.The production method comprises the following steps: heating zinc ingots to 550-650 DEG C in an induction furnace, increasing the temperature of the molten liquid to 750-780 DEG C after complete melting, adding aluminum ingots, magnesium ingots, aluminum lanthanum intermediate alloy, aluminum cerium intermediate alloy and CeO2, uniformly stirring the molten liquid by using a magnetic stirring device, and waiting for complete dissolution of the added alloy, then cooling the molten liquid to 600-630 DEG C for refining and deslagging, finally reducing the temperature of the molten liquid to 530-560 DEG C for slagging and casting the alloy ingots, and the cooling speed of the alloy ingots after casting is less than 10 DEG C / s.The zinc-aluminum-magnesium alloy obtained by the application is uniform in composition, and the problems of segregation and brittle fracture of the alloy ingots during casting of the high-magnesium zinc-aluminum-magnesium alloy are solved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of metal alloys, in particular to a high-magnesium zinc-aluminum-magnesium alloy for an ultrahigh corrosion-resistant coating and a production method thereof. BACKGROUND

[0002] A zinc-aluminum-magnesium coating is a newly developed alloy coating in recent years, and has become an important development direction of alloy coatings due to excellent surface corrosion resistance and notch corrosion resistance, and has been widely applied. Since 2020, with the increasing corrosion demand in some special fields, developing a zinc-aluminum-magnesium coating with higher corrosion resistance has become a trend.

[0003] When producing a zinc-aluminum-magnesium alloy with a magnesium content greater than 3%, surface oxidation occurs during casting.

[0004] The patent with the application number 201811157769.9 "A hot-dip galvanized zinc-aluminum-magnesium alloy containing titanium and antimony and a preparation method thereof" contains 2.5-3.5% of magnesium, 10-12% of aluminum, 0.1-0.2% of titanium, 0.1-0.1% of antimony, and the balance of zinc. The process adds pure zinc, pure aluminum, Al-50% Mg intermediate alloy, Al-5% Ti intermediate alloy, and Al-5% Sb intermediate alloy into a crucible, heats the crucible to 700-720 DEG C, adds a covering agent (NaCl+KCl) to melt, refines and removes slag by using ZnCl2, and casts at a temperature of 550 DEG C. The process technology uses a covering agent (NaCl+KCl) to melt and directly cast. It cannot be directly used for smelting a zinc-aluminum-magnesium alloy with a magnesium content greater than 3.5%, and oxidation occurs during casting, the surface is black, and qualified products cannot be produced.

[0005] The patent with the application number 202211010328.2 "A production method of a high-magnesium zinc-aluminum-magnesium alloy" uses a refining agent for refining, which can further enhance the diffusion performance, surface tension and chemical stability of the flux. The melting point and specific gravity of the refining agent are lower than those of the zinc-aluminum-magnesium alloy, and the refining agent is scattered on the surface to play a role in isolating the melt and air, reducing the oxidation and combustion of magnesium metal, improving the direct recovery rate of magnesium, and reducing the burning loss.

[0006] In the production of a high-magnesium zinc-aluminum-magnesium alloy, in addition to surface oxidation, the high magnesium content leads to the formation of a large number of Mg x Zn y alloy, which increases the brittleness of the alloy, and the alloy ingot is prone to breakage. At the same time, due to uneven cooling, the segregation of alloy elements is serious, which seriously affects the quality and yield of the product. SUMMARY

[0007] The present application adds La and Ce elements in the production of high-magnesium zinc-aluminum-magnesium alloy, the chemical composition of the zinc-aluminum-magnesium alloy includes Zn, Al, Mg, Si, La, Ce and other elements in the alloy ingot, in terms of percentage by weight: Al 15-30%, Mg 5-8%, Si 0.15-0.4%, the balance being zinc and unavoidable impurities; La: 0.01-0.05%, Ce: 0.05-0.2%; the alloy contains Ce including Ce and CeO2. The preparation method is: heating the zinc ingot to 550-650 °C in an induction furnace, after complete melting, increasing the temperature of the molten liquid to 750-780 °C, adding aluminum ingot, magnesium ingot, aluminum lanthanum master alloy, aluminum cerium master alloy, CeO2, using a magnetic stirring device to stir the molten liquid uniformly until the added alloy is completely dissolved, then cooling the molten liquid to 600-630 °C for refining and deslagging, and finally reducing the temperature of the molten liquid to 530-560 °C for slagging and casting into alloy ingot, the cooling speed of the alloy ingot after casting is less than 10 °C / s.

[0008] The beneficial technical effects of the present application are as follows:

[0009] The purification effect of La and Ce mainly manifests in significantly reducing inclusions and harmful elements in the aluminum liquid of the alloy, reducing the pinhole rate and porosity; at the same time, La and Ce can also refine grains and dendrites, inhibit the appearance of coarse phases, enhance the toughness of the alloy, and reduce the fracture phenomenon of the alloy ingot after casting; adding a certain amount of La and Ce in the aluminum alloy can effectively improve the high-temperature oxidation resistance of the alloy and reduce the surface oxidation during alloy casting. Especially, the Ce element is added in the form of Ce and CeO2, CeO2 can reduce the surface tension and critical nucleation resistance of the liquid metal, promote nucleation, hinder grain growth, and at the same time, CeO2 makes the flow of the molten pool more sufficient, so the structure is more dense and uniform.

[0010] The addition of La and Ce adopts the mode of aluminum lanthanum master alloy, aluminum cerium master alloy and CeO2, without greatly increasing the heating temperature of the molten liquid; the casting temperature is controlled at 530-560 °C, and the cooling speed is less than 10 °C / s, so that the obtained alloy is uniformly solidified, the brittleness and internal shrinkage of the alloy are reduced, and the segregation problem of alloy elements is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is the qualified high-magnesium zinc-aluminum-magnesium alloy ingot produced by the embodiment 3 of the present application.

[0012] Figure 2 is the brittle fracture high-magnesium zinc-aluminum-magnesium alloy ingot produced by the comparative example 1 of the present application. DETAILED DESCRIPTION

[0013] The following detailed description of various exemplary embodiments of the application should not be considered to be limitations on the present application, which is described in terms of certain embodiments, aspects, and implementations. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application.

[0014] In addition, for numerical ranges of the present application, it is to be understood that every numerical value, range, or equivalent thereof between the recited upper and lower limits is specifically included. Any smaller ranges or individual values not recited are excluded from the application. The upper and lower limits of these smaller ranges are independently combinable with each other as well as with the ranges explicitly recited.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described.

[0016] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended terms that are intended to mean including, but not limited to.

[0017] The high magnesium zinc aluminum magnesium alloy for super-high corrosion resistant coating and the method of producing the same according to the present application will be described in more detail below with reference to specific examples.

[0018] In the embodiments according to the present application, the high magnesium zinc aluminum magnesium alloy for super-high corrosion resistant coating is manufactured by the following method.

[0019] The high magnesium zinc aluminum magnesium alloy for super-high corrosion resistant coating has the following chemical composition in terms of weight percentage: Al 15-30%, Mg 5-8%, Si 0.15-0.4%, and the balance of zinc and unavoidable impurities.

[0020] The high magnesium zinc aluminum magnesium alloy further includes, in terms of weight percentage, La: 0.01-0.05%, and Ce: 0.05-0.2%.

[0021] The alloy includes Ce including Ce and CeO2.

[0022] The preparation method of the high-magnesium zinc-aluminum-magnesium alloy is as follows: zinc ingots are heated to 550-650 °C in an induction furnace, the temperature of the molten liquid is raised to 750-780 °C after complete melting, aluminum ingots, magnesium ingots, aluminum-lanthanum master alloy, aluminum-cerium master alloy, and CeO2 are added, the molten liquid is stirred uniformly by using a magnetic stirring device until the added alloy is completely dissolved, then the molten liquid is cooled to 600-630 °C for refining and slag removal, and finally the temperature of the molten liquid is reduced to 530-560 °C for slagging and casting into alloy ingots.

[0023] The cooling speed of the alloy ingots after casting is less than 10 °C / s. The high-magnesium zinc-aluminum-magnesium alloy for ultra-high corrosion-resistant coating will be described below in combination with specific examples.

[0024] Example 1

[0025] 1. The chemical composition of the high-magnesium zinc-aluminum-magnesium alloy for ultra-high corrosion-resistant coating, by weight percentage: Al 15%, Mg 5%, Si 0.15%, and the balance being zinc and unavoidable impurities.

[0026] 2. The high-magnesium zinc-aluminum-magnesium alloy further comprises La: 0.01%, and Ce: 0.05%, by weight percentage.

[0027] 3. The Ce contained in the alloy includes Ce and CeO2.

[0028] 4. The preparation method of the high-magnesium zinc-aluminum-magnesium alloy is as follows: zinc ingots are heated to 550 °C in an induction furnace, the temperature of the molten liquid is raised to 750 °C after complete melting, aluminum ingots, magnesium ingots, aluminum-lanthanum master alloy, aluminum-cerium master alloy, and CeO2 are added, the molten liquid is stirred uniformly by using a magnetic stirring device until the added alloy is completely dissolved, then the molten liquid is cooled to 600 °C for refining and slag removal, and finally the temperature of the molten liquid is reduced to 530 °C for slagging and casting into alloy ingots.

[0029] 5. The cooling speed of the alloy ingots after casting is 5 °C / s.

[0030] Example 2

[0031] 1. The chemical composition of the high-magnesium zinc-aluminum-magnesium alloy for ultra-high corrosion-resistant coating, by weight percentage: Al 30%, Mg 8%, Si 0.4%, and the balance being zinc and unavoidable impurities.

[0032] 2. The high-magnesium zinc-aluminum-magnesium alloy further comprises La 0.05%, and Ce 0.2%, by weight percentage.

[0033] 3. The Ce contained in the alloy includes Ce and CeO2.

[0034] 4. The high-magnesium zinc-aluminum-magnesium preparation method is as follows: zinc ingots are heated to 650°C in an induction furnace, the temperature of the molten liquid is raised to 780°C after complete melting, aluminum ingots, magnesium ingots, and aluminum-lanthanum master alloy, aluminum-cerium master alloy, and Ce02 are added, the molten liquid is stirred uniformly by a magnetic stirring device until the added alloy is completely dissolved, then the molten liquid is cooled to 630°C for refining and slag removal, and finally the temperature of the molten liquid is reduced to 560°C for slagging and casting into alloy ingots.

[0035] 5. The cooling speed of the alloy ingots after casting is 10°C / s.

[0036] Example 3

[0037] 1. The chemical composition of the high-magnesium zinc-aluminum-magnesium alloy for super-high corrosion-resistant coating is as follows: Al 19%, Mg 6%, Si 0.25%, and the balance being zinc and unavoidable impurities.

[0038] 2. The high-magnesium zinc-aluminum-magnesium alloy further comprises La: 0.03% and Ce: 0.1% by weight percentage.

[0039] 3. The alloy comprises Ce including Ce and Ce02.

[0040] 4. The high-magnesium zinc-aluminum-magnesium preparation method is as follows: zinc ingots are heated to 600°C in an induction furnace, the temperature of the molten liquid is raised to 760°C after complete melting, aluminum ingots, magnesium ingots, and aluminum-lanthanum master alloy, aluminum-cerium master alloy, and Ce02 are added, the molten liquid is stirred uniformly by a magnetic stirring device until the added alloy is completely dissolved, then the molten liquid is cooled to 620°C for refining and slag removal, and finally the temperature of the molten liquid is reduced to 550°C for slagging and casting into alloy ingots.

[0041] 5. The cooling speed of the alloy ingots after casting is 8°C / s.

[0042] Comparative Example 1

[0043] 1. The chemical composition of the high-magnesium zinc-aluminum-magnesium alloy is as follows: Al 15-30%, Mg 5-8%, Si 0.15-0.4, and the balance being zinc and unavoidable impurities.

[0044] 2. The high-magnesium zinc-aluminum-magnesium preparation method is as follows: zinc ingots are heated to 600°C in an induction furnace, the temperature of the molten liquid is raised to 760°C after complete melting, aluminum ingots and magnesium ingots are added, the molten liquid is stirred uniformly by a magnetic stirring device until the added alloy is completely dissolved, then the molten liquid is cooled to 620°C for refining and slag removal, and finally the temperature of the molten liquid is reduced to 550°C for slagging and casting into alloy ingots.

[0045] 3. The cooling speed of the alloy ingots after casting is 8°C / s.

[0046] Comparative Example 2

[0047] 1. High magnesium zinc-aluminum-magnesium alloy chemical composition, in percentage by weight: Al 19%, Mg 6%, Si 0.25%, the rest being zinc and unavoidable impurities.

[0048] 2. The alloy also comprises La: 0.03% in percentage by weight.

[0049] 3. High magnesium zinc-aluminum-magnesium production method: zinc ingots are heated to 600°C in an induction furnace, the temperature of the molten liquid is increased to 760°C after complete melting, aluminum ingots, magnesium ingots and aluminum lanthanum master alloy are added, the molten liquid is stirred uniformly using a magnetic stirring device until the added alloy is completely dissolved, after that the molten liquid is cooled to 620°C for refining and slag removal, finally the temperature of the molten liquid is reduced to 550°C for slagging and casting into alloy ingots.

[0050] 4. The cooling speed of the alloy ingots after casting is 15°C / s.

[0051] Evaluation Example

[0052] The high magnesium zinc-aluminum-magnesium alloys obtained through Examples 1-3 and Comparative Examples 1-2 above are analyzed respectively, 2mm x 2mm x 2mm size alloy is taken from 20 different positions on the alloy ingot to analyze its chemical composition, and the probability of segregation phenomenon in the alloy is counted. The effect of solving the alloy composition segregation problem in the present application is evaluated, and the results are shown in Table 1 below.

[0053] Table 1

[0054] No. Number of points of compositional segregation in the alloy ingot (20 regions analyzed) Example 1 1 Example 2 2 Example 3 1 Comparative Example 1 11 Comparative Example 2 9

[0055] As can be seen from Table 1, the proportion of composition segregation points in the alloys of Examples 1-3 is much smaller than that of Comparative Examples 1 and 2, which shows that the addition of La, Ce, especially CeO2, and the method of reducing the cooling speed after casting in the present application can greatly reduce the segregation.

[0056] The brittleness of the high magnesium zinc-aluminum-magnesium alloy ingots obtained through Examples 1-3 and Comparative Examples 1-2 above is analyzed respectively, impact detection is carried out on the large ingots (weight 800Kg / each) after casting, and the proportion of 20 large ingots broken is counted. The effect of solving the problem of brittle fracture of high magnesium zinc-aluminum-magnesium alloy in the present application is evaluated, and the results are shown in Table 2 below.

[0057] Table 2

[0058] No. Number of brittle fractures of the alloy ingot (20 ingots impacted) Example 1 0 Example 2 1 Example 3 0 Comparative Example 1 15 Comparative Example 2 10

[0059] As shown in Table 2, the proportion of brittle fracture of the alloy ingots of Examples 1-3 after impact is far less than that of Comparative Examples 1 and 2, which indicates that the method of adding La, Ce, especially CeO2 in the present application to reduce the casting cold speed can increase the plasticity of the alloy and reduce the brittle fracture of the alloy ingots.

[0060] While the application has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details can be made therein without departing from the spirit and scope of the application as defined by the appended claims and their equivalents. Embodiments should only be considered exemplary and should not be used to construe the scope of the present application. The scope of the application is therefore not to be limited by the specific embodiments herein, but only by the claims.

Claims

1. A high-magnesium zinc-aluminum-magnesium alloy for use in ultra-high corrosion-resistant coatings, characterized in that, The chemical composition of the high-magnesium zinc-aluminum-magnesium alloy, by weight percentage, is: Al 15-30%, Mg 5-8%, Si 0.15-0.4%, La 0.01-0.05%, Ce 0.05-0.2%, with the balance being zinc and unavoidable impurities; The Ce includes Ce and CeO2; The preparation steps of the high-magnesium zinc-aluminum-magnesium alloy are as follows: zinc ingots are heated to 550-650°C in an induction furnace. After complete melting, the temperature of the melt is raised to 750-780°C. Aluminum ingots, magnesium ingots, aluminum-lanthanum master alloy, aluminum-cerium master alloy, and CeO2 are added. The melt is stirred evenly with a magnetic stirring device until the added alloys are completely dissolved. Then, the melt is cooled to 600-630°C for refining and slag removal. Finally, the temperature of the melt is lowered to 530-560°C for slag removal and casting into alloy ingots. The cooling rate of the alloy ingot after casting is less than 10℃ / s.

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