CN101629261B - A kind of rare earth flame-retardant magnesium alloy and preparation method thereof - Google Patents

Abstract

The invention relates to a rare-earth flame-retardant magnesium alloy and a preparation method thereof, and relates to a magnesium-based alloy in which rare-earth metals are used as secondary main components. The atomic percentage of constituent elements in the alloy is Mg _96.0-98.19 Y _0.31-0.5 Dy _1.5-3.5 , according to The mass percentage of the constituent elements is pure magnesium, the Mg-Y master alloy containing 29.05% by mass of Y and the Mg-Dy master alloy containing 29.025% by mass of Dy. Heating and smelting at 600°C, 650°C and 720°C, intermittently feeding a mixed protective gas of 99.5vol.% CO ₂ +0.5vol.% SF6, and then casting to obtain a composition of Mg _96.0～98.19 Y _{0.31～ 0.5} Dy _{1.5 ~ 3.5} flame retardant magnesium alloy products. The product has high purity and improved flame retardancy.

Description

A rare-earth flame-retardant magnesium alloy and its preparation method

technical field

The technical solution of the invention relates to a magnesium-based alloy with rare earth metal as the secondary main component, specifically a rare earth flame-retardant magnesium alloy and a preparation method thereof.

Background technique

The position of Mg in the periodic table is in the range of alkaline metals, and its extranuclear electrons are less, which determines that Mg has strong chemical activity. Mg is easy to react with oxidizing media, so that the application of Mg-based products and components is greatly limited. However, Mg has some excellent characteristics that other metals do not have: light weight, high specific strength and high specific stiffness, excellent antimagnetic and shock absorption, good chip processing and easy recycling, so magnesium alloys are used in aviation , transportation and electronics have irreplaceable advantages.

In view of the shortcomings of magnesium and magnesium alloys that are easy to oxidize and burn, so far, domestic and foreign researchers have studied a variety of preparation methods for flame-retardant magnesium alloys. These methods are roughly divided into: flux covering method, gas protection method and alloying flame retardant method. These three methods have brought some unavoidable side effects while improving the flame retardancy of magnesium alloys. The flux in the flux covering method mostly uses chlorine salt or a mixture of chloride salts. During the process of smelting magnesium alloys, due to the high density of chloride salts, the added chloride salts will continue to sink to the bottom and need to be added continuously. This is undoubtedly More inclusions are involved. In addition, chlorine salt is toxic and poses a threat to personal health and safety; although the gas protection method solves the operational complexity, the gas used is a rare gas or some mixture containing S. Gases, rare gases are expensive and scarce, not suitable for widespread use, and gases containing S will produce some toxic gases or gases with a strong greenhouse effect, which conflicts with the safe and environmentally friendly production proposed by the world; alloying The flame retardant method is currently an ideal method for preparing flame retardant magnesium alloys. However, among all flame retardant elements, Be and Ca have the best effects in terms of improving flame retardancy, but Be is a toxic substance, and calcium The addition of Mg makes the mechanical properties of the magnesium alloy greatly reduced. In addition, in addition to the above three common preparation methods of flame-retardant magnesium alloys, there is another one that is the renewal of manufacturing equipment. Large-scale equipment for vacuum smelting magnesium alloys has been developed abroad, but the initial capital investment is huge. Due to the limitations of my country's metallurgical equipment technology and business model, this method cannot be applied in China.

my country is a country rich in rare earth resources. For this reason, researchers in our country pay more and more attention to and continue to develop the special effects of rare earths on metal materials. Rare earths can not only purify molten metal, remove slag and exhaust, but also optimize the performance of materials. In order to make Mg, a material with excellent characteristics, obtain greater utilization value, researchers in our country have also carried out active research and development on the role of rare earths in magnesium alloys.

CN101376938 discloses a novel flame-retardant high-strength heat-resistant magnesium alloy and its preparation method, which is to add Al-Ca master alloy, Al-RE master alloy and Al-Sr master alloy into the molten magnesium alloy AZ91D; CN1400328 discloses strong A tough flame-retardant magnesium alloy whose components include Al, Zn, Mn, RE and Mg; CN1540016 reported a cast flame-retardant magnesium alloy whose components are Al, Zn, Mn, RE, Be and Mg. RE in the above patent documents is a mixed rare earth element. It can be seen that the composition of the existing disclosed rare earth flame-retardant magnesium alloys is based on the commonly used magnesium alloys Mg-Al series and Mg-Zn series alloys, and then adding a variety of mixed rare earth element master alloys and other master alloys, which also leads to The existing disclosed preparation methods of rare earth flame-retardant magnesium alloys will inevitably involve some impurities during the smelting and preparation process, and the heat resistance, ie, the ignition point, of the prepared flame-retardant magnesium alloys needs to be further improved.

CN200910069793.1 Flame-retardant foamed magnesium alloy and its preparation method discloses a flame-retardant foamed magnesium alloy product with a magnesium-yttrium-dysprosium ternary alloy as the matrix material by using a melt foaming two-step process. The structural performance of the product is essentially different from that of non-foamed flame-retardant magnesium alloys.

Contents of the invention

The technical problem to be solved by the present invention is to provide a rare-earth flame-retardant magnesium alloy and its preparation method, which uses pure magnesium as the matrix, and adds it and Mg-Y and Mg-Dy master alloys at the same time to make them melt together The prepared magnesium yttrium dysprosium ternary flame-retardant magnesium alloy has the composition atomic percentage of: Mg _96.0-98.19 Y _0.31-0.5 Dy _1.5-3.5 . This method overcomes the disadvantage that some impurities will inevitably be involved in the smelting and preparation process of the existing disclosed rare earth flame-retardant magnesium alloy preparation method, and the heat resistance of the flame-retardant magnesium alloy prepared by it, that is, the ignition point, is further improved. improve.

The technical solution adopted by the present invention to solve the technical problem is: a rare earth flame-retardant magnesium alloy, which is a magnesium-yttrium-dysprosium ternary flame-retardant magnesium alloy, and the atomic percentage of its constituent elements is Mg _96.0～98.19 Y _0.31～0.5 Dy _{1.5～ 3.5} .

The preparation method of above-mentioned a kind of rare earth flame retardant magnesium alloy, its steps are:

Step One, Ingredients

According to the mass percentage of the constituent elements, Mg:Y:Dy=96.0～98.19:0.31～0.5:1.5～3.5 Weigh pure magnesium, Mg-Y master alloy and Mg-Dy master alloy raw materials, wherein, Mg-Y master alloy contains The mass percentage of Y is 29.05% and the rest is Mg, and the mass percentage of Dy contained in the Mg-Dy master alloy is 29.025% and the rest is Mg;

The second step, smelting of rare earth flame retardant magnesium alloy

Preheat the crucible in a crucible-type resistance furnace to 500°C and take it out, add all the raw materials of pure magnesium, Mg-Y master alloy and Mg-Dy master alloy weighed in the first step into the crucible at one time, and then the crucible Quickly put it into a crucible-type resistance furnace, and immediately pass a protective gas, heat at a temperature of 600-720°C, and intermittently pass a protective gas at 600°C, 650°C and 720°C, so that all the raw materials are melted. Mechanical stirring is carried out above the melting point of the magnesium alloy to uniformly disperse the rare earth elements. While stirring, the residue floating above the magnesium alloy liquid is removed to melt the rare earth flame-retardant magnesium alloy. The protective gas is 99.5vol.% CO ₂ +0.5vol.% SF ₆ mixed gas;

The third step is casting into flame retardant magnesium alloy products

Heat the rare earth flame retardant magnesium alloy solution melted in the crucible in the second step crucible resistance furnace at 720°C to 740°C, let it stand for 10 minutes, and then cast it into a metal mold to obtain the constituent elements The atomic percentage is Mg _96.0～98.19 Y _0.31～0.5 Dy _1.5～3.5 flame retardant magnesium alloy products.

In the aforementioned rare-earth flame-retardant magnesium alloy and its preparation method, the pure magnesium raw material is industrially pure magnesium with a purity of 99.95% by mass.

The above-mentioned rare earth flame-retardant magnesium alloy and its preparation method, the raw materials of the Mg-Y master alloy and the Mg-Dy master alloy are purchased from Inner Mongolia Rare Earth Research Institute, and the pure magnesium raw materials are obtained from the general market, and the equipment used is generic.

The beneficial effects of the present invention are: compared with the prior art, the remarkable progress of the present invention lies in;

(1) The flame-retardant magnesium alloy prepared by the method of the present invention has very high purity, so various properties are excellent.

1. The parent material selected in the prior art CN101376938 is AZ91D, which is a common magnesium alloy made by refining industrial pure magnesium through a process. Some impurities will inevitably be involved in the smelting preparation process. The parent material selected in the present invention is pure Magnesium, to avoid the involvement of impurities.

2. the used master alloy of prior art CN101376938 has three kinds of Al-Ca master alloy, Al-RE master alloy and Al-Sr master alloy, and the master alloy used in the present invention has only two kinds of Mg-Y master alloy and Mg-Dy master alloy . The more types of master alloys selected, the lower the purity of the magnesium alloy solution during smelting.

③In the preparation process of magnesium alloy, the prior art CN101376938 adopts the preheated master alloy after melting the base material AZ91D at 740°C. At a high temperature of 740°C, the surface of the magnesium alloy liquid is easy to absorb gas in the air to react, which increases the impurities in the magnesium alloy liquid. When the intermediate alloy is added, it will stir the surface of the magnesium alloy liquid, causing the adsorbed gas to be involved in the Inside the magnesium alloy liquid, thereby reducing the performance of the prepared flame-retardant magnesium alloy. The method of the invention adopts the method of adding the base metal and the master alloy together, avoiding the gas involved when adding the master alloy for the second time, thereby ensuring the purity of the magnesium alloy liquid, thereby ensuring the excellent performance of the prepared flame-retardant magnesium alloy.

(2) The ignition point of the flame-retardant magnesium alloy prepared by the method of the present invention is improved, that is, the flame-retardant performance is improved.

The flame retardant test of the flame retardant magnesium alloy prepared by the method of the present invention shows that its ignition point is about 200°C higher than that of pure magnesium, and the average value of the ignition point reaches above 850°C. This result is better than the flame retardant overall effect of the flame retardant magnesium alloy reported by CN101376938, CN1400328 and CN1540016. In the process of testing the ignition point, when the flame-retardant magnesium alloy prepared by the method of the present invention has sparks flickering locally, it can quickly self-repair, preventing further combustion, and further heating, the flame-retardant magnesium alloy prepared by the method of the present invention After the alloy is melted, the oxide film on its surface has good toughness, which effectively protects the molten magnesium alloy liquid.

(3) The method of the present invention is implemented at some characteristic temperatures by feeding a part of the protective gas and then stopping the gas, that is, heating at a temperature of 600 to 720°C, and intermittently feeding the protective gas at 600°C, 650°C and 720°C to prevent raw materials from deep oxidation. Because the method of the present invention adopts the mixed protective gas of CO ₂ +SF ₆ , this intermittent way of feeding the protective gas greatly reduces the greenhouse effect caused by SF ₆ , effectively reduces the production cost, and is environmentally friendly. and personal safety will reduce the hazards.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a high-magnification metallographic photograph of a flame-retardant magnesium alloy product prepared in Example 1 of the present invention.

Fig. 2 is a low-magnification metallographic photograph of the flame-retardant magnesium alloy product prepared in Example 1 of the present invention.

Detailed ways

Example 1

Step One, Ingredients

Weigh pure magnesium, Mg-Y master alloy and Mg-Dy master alloy raw materials according to the mass percentage of constituent elements as Mg:Y:Dy=97.65:0.35:2.0, wherein, the mass percentage of Mg-Y master alloy containing Y is 29.05 The rest is Mg, the mass percentage of Dy contained in the Mg-Dy master alloy is 29.025%, and the rest is Mg. The pure magnesium used is a commercially available commodity. The Mg-Y master alloy and the Mg-Dy master alloy are purchased from Inner Mongolia Rare Earth Research Institute;

The second step, smelting of rare earth flame retardant magnesium alloy

Preheat the crucible in a crucible-type resistance furnace to 500°C and take it out, add all the raw materials of pure magnesium, Mg-Y master alloy and Mg-Dy master alloy weighed in the first step into the crucible at one time, and then the crucible Quickly put it into a crucible-type resistance furnace, and immediately pass a protective gas, heat at a temperature of 600-720°C, and intermittently pass a protective gas at 600°C, 650°C and 720°C, so that all the raw materials are melted. Mechanical stirring is carried out above the melting point of the magnesium alloy to uniformly disperse the rare earth elements. While stirring, the residue floating above the magnesium alloy liquid is removed to melt the rare earth flame-retardant magnesium alloy. The protective gas is 99.5vol.% CO ₂ +0.5vol.% SF6 mixed gas;

The third step is casting into flame retardant magnesium alloy products

Heat the rare earth flame retardant magnesium alloy solution melted in the crucible in the second step crucible resistance furnace at 720°C to 740°C, let it stand for 10 minutes, and then cast it into a metal mold to obtain the constituent elements The atomic percentage is a flame-retardant magnesium alloy product of Mg _97.65 Y _0.35 Dy _2.0 .

Fig. 1 is a 500 times metallographic photo of the flame retardant magnesium alloy product prepared in Example 1 of the present invention, and Fig. 2 is a 200 times metallographic photo of the flame retardant magnesium alloy product prepared in Example 1 of the present invention. It can be seen from these two photos that the flame-retardant magnesium alloy product prepared in Example 1 of the present invention has a dense structure, clear grain boundaries, and few impurities.

Example 2

Step One, Ingredients

According to the mass percent of the constituent elements, Mg:Y:Dy=96.1:0.40:3.5 Weigh pure magnesium, Mg-Y master alloy and Mg-Dy master alloy raw materials, wherein, the mass percent of Mg-Y master alloy containing Y is 29.05 The rest is Mg, the mass percentage of Dy contained in the Mg-Dy master alloy is 29.025%, and the rest is Mg. The pure magnesium used is a commercially available commodity. The Mg-Y master alloy and the Mg-Dy master alloy are purchased from Inner Mongolia Rare Earth Research Institute;

The second step, smelting of rare earth flame retardant magnesium alloy

With embodiment 1;

The third step is casting into flame retardant magnesium alloy products

Same as in Example 1, that is, a flame-retardant magnesium alloy product in which the atomic percentage of the constituent elements is Mg _96.1 Y _0.40 Dy _3.5 is obtained.

Example 3

Step One, Ingredients

According to the mass percentage of the constituent elements, Mg:Y:Dy=97.05:0.45:2.5 Weigh pure magnesium, Mg-Y master alloy and Mg-Dy master alloy raw materials, wherein, the mass percentage of Mg-Y master alloy containing Y is 29.05 The rest is Mg, the mass percentage of Dy contained in the Mg-Dy master alloy is 29.025%, and the rest is Mg. The pure magnesium used is a commercially available commodity. The Mg-Y master alloy and the Mg-Dy master alloy are purchased from Inner Mongolia Rare Earth Research Institute;

The second step, smelting of rare earth flame retardant magnesium alloy

With embodiment 1;

The third step is casting into flame retardant magnesium alloy products

The same as in Example 1, that is, a flame-retardant magnesium alloy product in which the atomic percentage of the constituent elements is Mg _97.05 Y _0.45 Dy _2.5 is obtained.

Example 4

Step One, Ingredients

According to the mass percent of the constituent elements, Mg:Y:Dy=98.19:0.31:1.5 Weigh pure magnesium, Mg-Y master alloy and Mg-Dy master alloy raw materials, wherein, the mass percent of Mg-Y master alloy containing Y is 29.05 The rest is Mg, and the mass percentage of Dy contained in the Mg-Dy master alloy is 29.025%, and the rest is Mg. The pure magnesium used is industrially pure magnesium with a commercially available purity of 99.95% by mass, the Mg-Y master alloy and the Mg-Dy master alloy. The alloy was purchased from Inner Mongolia Rare Earth Research Institute;

The second step, smelting of rare earth flame retardant magnesium alloy

With embodiment 1;

The third step is casting into flame retardant magnesium alloy products

The same as in Example 1, that is, the flame-retardant magnesium alloy product with the atomic percentage of the constituent elements being Mg _98.19 Y _0.31 Dy _1.5 was obtained.

Example 5

Step One, Ingredients

Weigh pure magnesium, Mg-Y master alloy and Mg-Dy master alloy raw materials according to the mass percentage of constituent elements as Mg:Y:Dy=96.0:0.50:3.5, wherein, the mass percentage of Mg-Y master alloy containing Y is 29.05 The rest is Mg, and the mass percentage of Dy contained in the Mg-Dy master alloy is 29.025%, and the rest is Mg. The pure magnesium used is industrially pure magnesium with a commercially available purity of 99.95% by mass, the Mg-Y master alloy and the Mg-Dy master alloy. The alloy was purchased from Inner Mongolia Rare Earth Research Institute;

The second step, smelting of rare earth flame retardant magnesium alloy

With embodiment 1;

The third step is casting into flame retardant magnesium alloy products

The same as in Example 1, that is, the flame-retardant magnesium alloy product with the atomic percentage of the constituent elements being Mg _96.0 Y _0.50 Dy _3.5 was obtained.

In the process of mechanically stirring the rare earth elements as described in the above-mentioned embodiments, the surface of the magnesium alloy liquid is stable and pure, and no ignition phenomenon occurs; and the liquid level on the surface of the magnesium alloy liquid can quickly self-repair during stirring, effectively The addition of outside air is prevented; the magnesium alloy liquid flow is stable during casting, without any sparks flickering and thick smoke coming out.

The flame retardant tests of the flame retardant magnesium alloys prepared in all the above examples showed that the ignition points of the alloys were all 200°C higher than that of pure magnesium, and the average value of the ignition points reached over 850°C. In the process of testing the ignition point, when the flame-retardant magnesium alloy made by all the above-mentioned embodiments has local sparks, it can quickly self-repair, preventing further combustion and further heating. After the flame-retardant magnesium alloy is melted, the toughness of the oxide film on its surface is very good, which effectively protects the molten magnesium alloy liquid.

Claims (1)

1. A rare-earth flame-retardant magnesium alloy, characterized in that it is a magnesium-yttrium-dysprosium ternary flame-retardant magnesium alloy, and the atomic percentage of its constituent elements is Mg _96.0-98.19 Y _0.31-0.5 Dy _1.5-3.5 .

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