Low-cost flame-retardant magnesium alloy and low-requirement preparation method thereof

Abstract

The invention relates to the technical field of magnesium alloy materials, in particular to a low-cost flame-retardant magnesium alloy and a low-requirement preparation method thereof, and the low-cost flame-retardant magnesium alloy comprises the following raw materials in parts by weight: 7.0-7.2 wt.% of Al, 0.9-1.2 wt.% of Zn, 0.3-0.5 wt.% of Ca, 0.2-0.3 wt.% of Sr and the balance of Mg. The added rare earth element Sr can remarkably improve the flame retardant property of the alloy, the price is lower than that of rare earth elements such as Y added in current mainstream flame retardant alloy, the homogenization process requirement is lower, the alloy preparation cost is greatly reduced by cooperating with the smelting system, and the requirement for equipment is high under an existing flame retardant magnesium alloy smelting system, so that the cost is low. The smelting conditions are harsh, the smelting conditions and system greatly reduce the requirements of flame-retardant magnesium alloy smelting for devices and personnel, the magnesium alloy technology can be better popularized, and the method has great significance in practical application.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloy materials, and in particular to a low-cost flame-retardant magnesium alloy and a low-requirement preparation method thereof. Background Art

[0002] As the lowest-density metal engineering structural material currently available, magnesium alloy combines low density with excellent specific strength and stiffness, along with superior electromagnetic shielding and vibration damping capabilities. These unique advantages precisely meet the multiple demands of new energy vehicles for lightweighting, including noise absorption, vibration reduction, weight reduction, and radiation protection. The use of magnesium alloy not only significantly reduces vehicle energy consumption and effectively reduces vehicle body weight, but also further enhances vehicle maneuverability and safety, providing crucial material support for the greener and more intelligent upgrades of the automotive industry.

[0003] The innovative application of flame-retardant magnesium alloys in new energy vehicles will effectively open up new opportunities in the high-value-added magnesium alloy deep processing industry. This will not only propel the magnesium alloy industry to leapfrog development, significantly enhance its overall competitiveness and technological innovation, and consolidate its leading position in the domestic industry, but the widespread application of these technological achievements will also inject strong momentum into the development of high-value-added magnesium alloy products in my country. The implementation of this technology will bring significant economic and social benefits, providing important support for the industry's high-quality development and green, low-carbon transition.

[0004] Chinese patent publication number CN103468987B discloses a "method for preparing a flame-retardant magnesium alloy." The Mg-AL-Mn-Ca-Y alloy developed therein contains the rare earth element Y. This alloy has high production costs and high production equipment requirements, making it difficult to universally promote the process.

[0005] Based on this, the present invention provides a low-cost flame-retardant magnesium alloy and a low-requirement preparation method thereof to solve the above-mentioned technical problems. Summary of the Invention

[0006] The object of the present invention is to provide a low-cost flame-retardant magnesium alloy and a low-requirement preparation method thereof, so as to solve the problems mentioned in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The invention provides a low-cost flame-retardant magnesium alloy, which is composed of the following raw materials in parts by weight: 7.0-7.2 wt.% of Al, 0.9-1.2 wt.% of Zn, 0.3-0.5 wt.% of Ca, 0.2-0.3 wt.% of Sr, and the balance being Mg.

[0009] Preferably, it is composed of the following raw materials in parts by weight: 7.1 wt% of Al, 0.9 wt% of Zn, 0.5 wt% of Ca, 0.2 wt% of Sr, and the balance is Mg.

[0010] Preferably, it is composed of the following raw materials in parts by weight: 7.1 wt% of Al, 0.9 wt% of Zn, 0.3 wt% of Ca, 0.3 wt% of Sr, and the balance is Mg.

[0011] Based on the above formula, the present invention also proposes a low-cost and low-requirement preparation method of flame-retardant magnesium alloy, comprising the following steps:

[0012] 1) Prepare raw materials: Using magnesium ingots, aluminum blocks, magnesium-calcium master alloys, and magnesium-strontium master alloys as raw materials, calculate the weight percentage of each element according to 7.0-7.2 wt.% Al, 0.9-1.2 wt.% Zn, 0.3-0.5 wt.% Ca, 0.2-0.3 wt.% Sr, and the balance Mg;

[0013] Prepare the smelting system;

[0014] 2) Melting: First, preheat the magnesium ingot, place it in the furnace, start the furnace, and raise the furnace temperature to 680°C. After the magnesium ingot is completely melted, add the preheated aluminum ingot and zinc ingot into the furnace, raise the temperature to 720°C, stir for 15 minutes after melting, and then let it stand for 20-30 minutes;

[0015] Then, the temperature was raised to 750°C, and the preheated magnesium-calcium alloy and magnesium-strontium master alloy were added. After melting, the mixture was stirred for 15 minutes to remove the oxides and slag on the surface of the melt. The temperature was maintained at 750°C, and the mixture was allowed to stand for 40 to 50 minutes.

[0016] If burning occurs during the feeding process, add an appropriate amount of magnesium alloy covering agent;

[0017] 3) Casting: Stirring the alloy melt, skimming, standing for 20 minutes, and rapidly and steadily pouring the alloy melt to obtain an ingot of the low-cost flame-retardant magnesium alloy;

[0018] 4) Heat treatment extrusion: preheat the magnesium alloy ingot at 380°C for 45 to 60 minutes;

[0019] The preheated magnesium alloy ingot is extruded at 320-240° C. to obtain a magnesium alloy sheet with an extrusion ratio of 10.

[0020] Preferably, the preheating temperature of the preheating treatment in step 2) is 280-300° C., and the preheating time is 30-40 minutes.

[0021] Preferably, in step 1), the smelting system adopts a crucible furnace.

[0022] Compared with the prior art, the present invention has the following beneficial effects: the present invention strictly limits the weight percentage of the Ca element to the range of 0.3 to 0.5 wt.%. The Ca element plays multiple key roles in the alloy system: on the one hand, the addition of Ca can significantly refine the grains and optimize the alloy structure, thereby improving the forming performance of the material; on the other hand, Ca can be dissolved in the β-Mg17Al12 phase, effectively improving the melting point and thermal stability of the phase, while inhibiting the sliding of the grain boundaries at high temperatures. In addition, Ca can also form a dense oxide film on the surface of the alloy, blocking the inward diffusion of oxygen atoms, and significantly improving the ignition point of the alloy. However, when the Ca content exceeds the threshold, a coarse second phase is easily generated, resulting in impaired strength and plasticity of the alloy. Therefore, the Ca content range defined by the present invention, while exerting the beneficial effects of the Ca element, effectively avoids its potential drawbacks and achieves optimization of the alloy performance;

[0023] Compared with the existing technology, the rare earth element Sr added in the present invention can significantly improve the flame retardant properties of the alloy, and the price is lower than the rare earth elements such as Y added to the current mainstream flame retardant alloys, and the homogenization process requirements are lower. Combined with the smelting system described in the present invention, the alloy preparation cost is greatly reduced. Under the existing flame retardant magnesium alloy smelting system, high equipment requirements and harsh smelting conditions are placed on the equipment and personnel. The smelting conditions and system described in the present invention greatly reduce the requirements for flame retardant magnesium alloy smelting on equipment and personnel, which helps to better promote magnesium alloy technology and is of considerable significance in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the EDS image of the low-cost flame-retardant magnesium alloy according to Example 1 of the present invention.

[0025] Figure 2 This is the SEM image of the low-cost flame-retardant magnesium alloy described in Example 2 of the present invention.

[0026] Figure 3 This is a metallographic image of the magnesium alloy described in Example 2 of the present invention, with a magnification of 500;

[0027] Figure 4 This is a table of combustion grade test parameters for the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] For examples, see Figure 1-4The purpose of the present invention is to provide a low-cost flame-retardant magnesium alloy and a preparation method thereof, which not only has good comprehensive mechanical properties, but also has the advantages of high ignition point and low cost;

[0030] The low-cost flame-retardant magnesium alloy of the present invention comprises the following components by weight: Al 7.0-7.2%, Zn 0.9-1.2%, Ca 0.3-0.5%, Sr 0.2-0.3% and the balance;

[0031] Furthermore, the balance is Mg and other unavoidable impurities;

[0032] The alloy of the present invention has an ignition point of 815°C or above, a combustion grade of A, a yield strength of 180 MPa or more, a tensile strength of 285 MPa or more, and an elongation of 10% or more.

[0033] The preparation method of the low-cost flame-retardant magnesium alloy is characterized in that the preparation method comprises the following steps:

[0034] S1: Using magnesium ingot, aluminum block, magnesium-calcium master alloy and magnesium-strontium master alloy as raw materials, the weight percentage of each element is calculated and proportioned according to claim 1;

[0035] Prepare the smelting system;

[0036] S2: First, the magnesium ingot is preheated. The preheated magnesium ingot is placed in the furnace body, the furnace is ignited, and the furnace temperature is raised to 680°C. After the magnesium ingot is completely melted, the preheated aluminum ingot and zinc ingot are added into the furnace, and the temperature is raised to 720°C. After melting, they are stirred for 15 minutes and then left to stand for 20-30 minutes.

[0037] Then, the temperature was raised to 750°C, and the preheated magnesium-calcium alloy and magnesium-strontium master alloy were added. After melting, the mixture was stirred for 15 minutes to remove the oxides and slag on the surface of the melt. The temperature was maintained at 750°C, and the mixture was allowed to stand for 40 to 50 minutes.

[0038] Then cast;

[0039] If burning occurs during the feeding process, add an appropriate amount of magnesium alloy covering agent;

[0040] S3: Casting: Stirring the alloy melt, skimming, standing for 20 minutes, and rapidly and steadily pouring the alloy melt to obtain an ingot of the low-cost flame-retardant magnesium alloy;

[0041] S4: preheating the magnesium alloy ingot at 380°C for 45-60 minutes;

[0042] The preheated magnesium alloy ingot is extruded at 320-240°C to obtain a magnesium alloy sheet with an extrusion ratio of 10;

[0043] According to the present invention, preferably in step S1:

[0044] The content of Mg in the pure Mg is ≥99.98wt%;

[0045] The content of Al in the pure Al is ≥99.98 wt%;

[0046] The content of Zn in the pure Zn is ≥99.98wt%;

[0047] The Mg-Ca master alloy is a Mg-20wt%Ca master alloy; the Mg-Sr master alloy is a Mg-20wt%Sr master alloy;

[0048] Carry out ignition point performance test and tensile mechanics test, the tensile testing machine tensile rate is 1mm / min;

[0049] The flash point test is carried out in accordance with GB / T9343-2008 Test method for combustion performance of plastics - Determination of flash temperature and auto-ignition temperature, and the tensile test is carried out in accordance with GB / T16865-2013 Test specimens and methods for tensile testing of deformed aluminum, magnesium and their alloy products;

[0050] Conduct combustion grade test. Test environment: ambient temperature: 24.7℃; humidity: 52.4%RH. Test basis: GB / T5464-2010, GB / T14402-2007, GB / T20284-2006;

[0051] Assessment basis: GB8624-2012

[0052] Sample temperature rise △T≤50℃, mass loss rate △m≤50%, continuous burning time tf≤20s,

[0053] The total calorific value PCS is ≤ 3.0 MJ / kg, the combustion growth rate index FIGRA is 0.2 MJ ≤ 120 W / s, the flame spreads laterally and does not reach the edge of the long wing of the specimen, and the total heat release THR600 in 600 s is ≤ 7.5 MJ;

[0054] Specific example results are as follows Figure 4 As shown;

[0055] The mechanical properties of the magnesium alloy parts were tested. The mechanical properties of the magnesium alloy parts obtained in the embodiment of the present invention are shown in Table 1.

[0056] Table 1 Mechanical properties of samples in the examples

[0057]

[0058]

[0059] Comparative Example 1 is a "high-strength, flame-resistant, and extrudable aviation-grade magnesium alloy into tubes" disclosed in Chinese Patent 2019800995010, with a "Zn content of 0.1-0.8wt%, an Al content of 7-11wt%, and Ca and Y element contents of 0.75-1.50wt%."

[0060] The highest performance of the extruded tube or rectangular bar is a yield strength of 208 MPa, a tensile strength of 306 MPa, and an elongation of 9.46%. In comparison, the present invention reduces the Ca content and replaces the Y element with the lower-cost Sr. At the same time, the yield strength and tensile strength are comparable, and the elongation is increased by about 53%.

[0061] Comparative Example 2 is "Non-combustible magnesium alloy with excellent mechanical properties and preparation method thereof" disclosed in Chinese Patent No. 2011800055846. The Mg alloy comprises, by weight, 1.0% to 7.0% Al, 0.05% to 2.0% Ca, 0.05% to 2.0% Y, 0% to 6.0% Zn, and the balance Mg and other unavoidable impurities.

[0062] The total content of Ca and Y is equal to or higher than 0.1% but lower than 2.5% based on the total weight of the magnesium alloy;

[0063] The invention Al / (Ca+Y) is not within the scope of the rights described in the present invention;

[0064] The yield strength of the magnesium alloy extrusion material prepared by the method does not exceed 156 MPa, indicating that the material is more susceptible to deformation replication than the material of the present invention;

[0065] Various embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments.

[0066] Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

[0067] In summary, the present invention strictly limits the weight percentage of the Ca element to the range of 0.3 to 0.5wt.%. The Ca element plays multiple key roles in the alloy system: on the one hand, the addition of Ca can significantly refine the grains and optimize the alloy structure, thereby improving the forming performance of the material; on the other hand, Ca can be dissolved in the β-Mg17Al12 phase, effectively improving the melting point and thermal stability of the phase, while inhibiting the sliding of the grain boundaries at high temperatures. In addition, Ca can also form a dense oxide film on the surface of the alloy, blocking the inward diffusion of oxygen atoms, and significantly improving the ignition point of the alloy. However, when the Ca content exceeds the threshold, a coarse second phase is easily generated, resulting in damage to the strength and plasticity of the alloy. Therefore, the Ca content range defined by the present invention, while exerting the beneficial effects of the Ca element, effectively avoids its potential disadvantages and achieves the optimization of alloy properties;

[0068] Compared with the existing technology, the rare earth element Sr added in the present invention can significantly improve the flame retardant properties of the alloy. Compared with the rare earth elements such as Y added to the current mainstream flame retardant alloys, the price is lower and the homogenization process requirements are lower. Combined with the smelting system of the present invention, the alloy preparation cost is greatly reduced.

[0069] The existing flame retardant magnesium alloy smelting system has high requirements for equipment and harsh smelting conditions. The smelting conditions and system of the present invention greatly reduce the requirements for equipment and personnel in the smelting of flame retardant magnesium alloy, which helps to better promote the magnesium alloy process and has considerable significance in practical applications.

[0070] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0071] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A low-cost flame-retardant magnesium alloy, characterized in that: The invention is composed of the following raw materials in parts by weight: 7.0-7.2 wt.% of Al, 0.9-1.2 wt.% of Zn, 0.3-0.5 wt.% of Ca, 0.2-0.3 wt.% of Sr, and the balance of Mg.

2. A low-cost flame-retardant magnesium alloy according to claim 1, characterized in that: The composite material is composed of the following raw materials in parts by weight: 7.1 wt% of Al, 0.9 wt% of Zn, 0.5 wt% of Ca, 0.2 wt% of Sr, and the balance of Mg.

3. A low-cost flame-retardant magnesium alloy according to claim 2, characterized in that: The composite material is composed of the following raw materials in parts by weight: 7.1 wt% of Al, 0.9 wt% of Zn, 0.3 wt% of Ca, 0.3 wt% of Sr, and the balance of Mg.

4. A low-cost flame-retardant magnesium alloy preparation method according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) Prepare raw materials: Using magnesium ingots, aluminum blocks, magnesium-calcium master alloys, and magnesium-strontium master alloys as raw materials, calculate the weight percentage of each element according to 7.0-7.2 wt.% Al, 0.9-1.2 wt.% Zn, 0.3-0.5 wt.% Ca, 0.2-0.3 wt.% Sr, and the balance Mg; Prepare the smelting system; 2) Melting: First, preheat the magnesium ingot, place it in the furnace, start the furnace, and raise the furnace temperature to 680°C. After the magnesium ingot is completely melted, add the preheated aluminum ingot and zinc ingot into the furnace, raise the temperature to 720°C, stir for 15 minutes after melting, and then let it stand for 20-30 minutes; Then, the temperature was raised to 750°C, and the preheated magnesium-calcium alloy and magnesium-strontium master alloy were added. After melting, the mixture was stirred for 15 minutes to remove the oxides and slag on the surface of the melt. The temperature was maintained at 750°C, and the mixture was allowed to stand for 40 to 50 minutes. If burning occurs during the feeding process, add an appropriate amount of magnesium alloy covering agent; 3) Casting: Stirring the alloy melt, skimming, standing for 20 minutes, and rapidly and steadily pouring the alloy melt to obtain an ingot of the low-cost flame-retardant magnesium alloy; 4) Heat treatment extrusion: preheat the magnesium alloy ingot at 380°C for 45 to 60 minutes; The preheated magnesium alloy ingot is extruded at 320-240° C. to obtain a magnesium alloy sheet with an extrusion ratio of 10.

5. The low-cost flame-retardant magnesium alloy preparation method according to claim 4, characterized in that: The preheating temperature of the preheating treatment in step 2) is 280-300° C., and the preheating time is 30-40 minutes.

6. The low-cost flame-retardant magnesium alloy preparation method according to claim 4, characterized in that: In the step 1), the smelting system adopts a crucible furnace.

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