阅读说明：本技术 一种铝锂合金废料废屑再生回收方法 (Method for regenerating and recycling scrap of aluminum-lithium alloy waste ) 是由 刘志鹏 肖阳 马凯杰 解海涛 刘振杰 刘金学 郭晓光 高华 王飞超 于 2020-08-05 设计创作，主要内容包括：本发明属于有色金属材料循环利用技术领域,具体涉及一种铝锂合金废料废屑再生回收方法。本发明采用真空中频感应熔铸工艺回收铝锂合金废料废屑,通过两次精炼,多级过滤方式进行铝锂合金废料废屑回收,添加除杂剂消除部分铝锂合金废料废屑引入的金属和非金属夹杂,并添加高效细化剂细化铝锂合金再生铸锭晶粒,从而获得高纯净晶粒细化的高品质铝锂合金再生铸锭。本发明的方法可有效回收航空航天、电子器件等领域所产生的铝锂合金废料废屑,安全环保、生产效率高、再生铸锭品质高,回收再生的产品仍能用于原领域,无需降级使用,为铝锂合金的再生利用提供了一条有效的途径。(The invention belongs to the technical field of non-ferrous metal material recycling, and particularly relates to a method for recycling scrap of an aluminum-lithium alloy waste material. The method adopts a vacuum medium-frequency induction fusion casting process to recover the aluminum-lithium alloy waste scraps, recovers the aluminum-lithium alloy waste scraps in a multi-stage filtration mode through twice refining, adds an impurity removing agent to eliminate metal and nonmetal impurities introduced by part of the aluminum-lithium alloy waste scraps, and adds a high-efficiency refiner to refine aluminum-lithium alloy regeneration ingot casting grains, thereby obtaining the high-quality aluminum-lithium alloy regeneration ingot casting with refined high-purity grains. The method can effectively recycle the aluminum lithium alloy waste scraps generated in the fields of aerospace, electronic devices and the like, is safe and environment-friendly, has high production efficiency and high quality of regenerated cast ingots, can still be used in the original field without degradation, and provides an effective way for recycling the aluminum lithium alloy.)

1. The method for recycling the aluminum lithium alloy waste scraps is characterized by comprising the following steps of:

(1) pretreatment:

sequentially polishing, cleaning and crushing the secondary aluminum lithium alloy waste to obtain secondary waste; sequentially carrying out magnetic separation, screening, cleaning and briquetting on the tertiary scraps of the aluminum lithium alloy to obtain cake-shaped aluminum lithium waste; mixing the obtained secondary waste with cake-shaped aluminum lithium waste according to a certain proportion to obtain aluminum lithium mixed waste;

(2) smelting:

drying the aluminum-lithium mixed waste obtained in the step (1), placing the dried aluminum-lithium mixed waste into vacuum smelting equipment, vacuumizing, slowly heating to 380-; after the aluminum-lithium mixed waste is completely melted, adding an impurity removing agent, and refining to obtain molten metal;

(3) casting:

adding a refiner into the molten metal obtained in the step (2), casting and forming at 720-780 ℃, performing multi-layer filtration to obtain an aluminum-lithium alloy regenerated ingot, cooling to 100-200 ℃, and taking out the aluminum-lithium alloy regenerated ingot.

2. The process of claim 1, wherein the aluminum lithium alloy of step (1) is an alloy having an alloy designation of 2A97, 5A90, 2195, 2050 or 8090.

3. The process according to claim 1, characterized in that the secondary waste obtained in step (1) has a size of 10 to 200 mm; carrying out magnetic separation, screening and cleaning on the tertiary aluminum lithium alloy scraps in the step (1) to obtain 1-10 mm tertiary aluminum lithium alloy clean scraps, and briquetting to obtain cake-shaped aluminum lithium waste with the size of phi 100-150 mm; the mass percentage of the cake-shaped aluminum lithium waste in the aluminum lithium mixed waste obtained in the step (1) is 30-70%.

4. The treatment method as claimed in claim 1, wherein during the smelting in the step (2), the vacuum is pumped to 0.1-10 Pa, and argon gas with the pressure of 1000-3000 Pa is introduced.

5. The treatment method according to claim 1, wherein the impurity removing agent in the step (2) is at least one of B, Be, La and Ce, and the mass percent of the added impurity removing agent is 0.03-0.15%.

6. The process according to claim 1, wherein the refining step in the step (2) is carried out by stirring with a mechanical rotor while introducing argon gas, the stirring speed is 60 to 150r/min, and the aeration rate of argon gas is 0.1 to 1.0L/min.

7. The treatment method according to claim 1, wherein during casting and molding in the step (3), the molten metal obtained in the step (2) is directly added into the aluminum-lithium alloy new material melt with the same components in a liquid transfer mode, and the mass percentage of the added molten metal is 5-30%.

8. The treatment method according to claim 1, wherein the refiner in the step (3) is any one of master alloys Al-Ti-B, Al-Ti-C and Al-Ti-C-Sr, and the mass percent of the added refiner is 0.03-0.2%.

9. The process of claim 1, wherein the multi-layer filtration of step (3) is carried out by: and sequentially filtering by using a 3-8-mesh stainless steel net, a 10-40-mesh titanium net and a 10-20-mesh magnesia ceramic filter disc layer by layer.

10. The treatment method of claim 1, wherein after the aluminum lithium alloy regenerated ingot obtained in the step (3) is obtained, the aluminum lithium alloy regenerated ingot obtained in the step (3) is subjected to material proportioning and remelting with a new aluminum lithium alloy material with the same composition in a raw material form, and the mass percentage of the added aluminum lithium alloy regenerated ingot is 10-50%.

Technical Field

The invention belongs to the technical field of non-ferrous metal material recycling, and particularly relates to a method for recycling aluminum lithium alloy waste scraps generated in the fields of aerospace, electronic devices and the like.

Background

The density is reduced by 3% when 1% of lithium is added into the aluminum alloy, the aluminum lithium alloy is adopted to replace the conventional aviation aluminum alloy, the structural mass can be reduced by 5% -15%, the elastic modulus is improved by 10% -16%, the rigidity is improved by 15% -20%, and the aluminum lithium alloy has a wide application prospect in the field of aerospace. On one hand, however, lithium is more active and volatile, the aluminum lithium alloy is difficult to melt and cast, and the ingot casting yield is low; on the other hand, the addition of the lithium element weakens the plasticity and toughness of the aluminum alloy, so that the formability and the deformation processing capability of the aluminum-lithium alloy are deteriorated, and the processing yield is low. The waste material generation rate of the domestic 5A90 aluminum lithium alloy product is as high as 60 percent, which is one of the main reasons that the price of the aluminum lithium alloy is always high. With the continuous improvement of the domestic aluminum lithium alloy production technology and the continuous maturity of the market, the yield of the aluminum lithium alloy will be obviously increased, and more aluminum lithium alloy waste materials will be accumulated in the future.

The waste materials are mainly divided into: first grade waste (60%): ingot casting process waste (dry material is put in an induction furnace and a vacuum furnace, and head and tail are cut), ingot casting is scrapped, and large blocks of scrapped and massive process waste generated in processing (rolling, extruding and forging) links are scrapped; secondary waste material: waste materials generated by the residue of thin-wall processed products (thin plates and profiles); tertiary waste: and (3) scrap scraps generated by turning, milling, sawing and other processing on the surface of the cast ingot. The large-block primary aluminum lithium alloy waste can be directly recycled after simple treatment, and recycling is realized. The second-level and third-level wastes have larger surface area, and the conventional smelting method is very easy to burn and slag and cannot be directly recycled.

The method is limited by the prior art, no good method for recovering the waste scraps of the second-level and third-level wastes exists at present, the waste scraps can be stored only in a centralized classified storage mode, and manpower and material resources are consumed. The aluminum lithium alloy can react with water at normal temperature, particularly, the three-level waste mainly comprises scraps, has large surface area, is easy to absorb moisture in a humid environment, is easy to cause fire and other safety accidents due to improper disposal, and has larger potential safety hazards.

Patent CN 200680028805.0 of Alcan aluminum company proposes a method for recovering aluminum-lithium type alloy waste, the method forms a floating scrap layer above the melt, adopts a mode of not using gas protection or using a small amount of gas protection, the upper scrap is easy to oxidize and burn during the recovery process, and the recovery rate of the scrap is difficult to guarantee. In addition, in the final melting process of the floating scrap layer, the method prevents the floating scrap layer from being oxidized by adding molten salt, but the introduced molten salt is difficult to remove and becomes new impurities, so that the purity of the recovered product is reduced.

The Chinese patent with the application number of 201811610910.6 provides a method for recovering aluminum lithium alloy processing scraps, the method adds aluminum lithium alloy scraps into molten pure aluminum liquid, and the gas protection effect is poor in the scrap adding process, so that the scraps are easy to oxidize, burn and slag; the aluminum scraps have large surface tension, are easy to float on the surface when being directly added into an aluminum melt, are easy to generate oxidation burning loss along with the flow of gas in a furnace in the adding process, and have poor integral recovery effect.

According to the prior art, the waste is mostly recovered in an inert gas protection mode, but the dynamic charging process disturbs the inert gas protection atmosphere, and the waste directly contacted with the gas in a high-temperature environment is very easy to be rapidly oxidized into slag due to the special activity of the lithium-containing alloy.

Therefore, how to avoid the oxidation burning loss of the aluminum lithium alloy waste scraps in the recovery process, the recovery effect and the utilization value of the aluminum lithium alloy waste scraps are improved, the circular economy of aluminum physical alloy is created, and the method has very important practical significance.

Disclosure of Invention

In view of the above problems, the present invention provides a method for recycling scrap of aluminum lithium alloy waste, so as to improve the utilization rate of secondary and tertiary aluminum lithium alloy waste.

Based on the purpose, the invention adopts the following technical scheme:

a method for recycling scrap of aluminum lithium alloy waste comprises the following steps:

(1) pretreatment:

sequentially polishing, cleaning and crushing the secondary aluminum lithium alloy waste to obtain secondary waste; sequentially carrying out magnetic separation, screening, cleaning and briquetting on the tertiary scraps of the aluminum lithium alloy to obtain cake-shaped aluminum lithium waste; mixing the obtained secondary waste with cake-shaped aluminum lithium waste according to a certain proportion to obtain aluminum lithium mixed waste;

(2) smelting:

drying the aluminum-lithium mixed waste obtained in the step (1), placing the dried aluminum-lithium mixed waste into vacuum smelting equipment, vacuumizing, slowly heating to 380-; after the aluminum-lithium mixed waste is completely melted, adding an impurity removing agent, refining for 10-30 min, and standing for 10-30 min (the refined aluminum-lithium mixed waste can be subjected to secondary refining for 10-30 min under the same conditions, and standing for 10-30 min again) to obtain molten metal;

(3) casting:

adding a refiner into the molten metal obtained in the step (2), standing for 15-40 min, casting and molding at 720-780 ℃, performing multi-layer filtration to obtain an aluminum-lithium alloy regenerated ingot, cooling to 100-200 ℃, and taking out the aluminum-lithium alloy regenerated ingot.

Preferably, the aluminum lithium alloy in step (1) is an aluminum lithium alloy with an alloy grade including but not limited to 2a97, 5a90, 2195, 2050 or 8090.

Preferably, the size of the secondary waste obtained in the step (1) is 50-100 mm; carrying out magnetic separation, screening and cleaning on the tertiary aluminum lithium alloy scraps in the step (1) to obtain 1-10 mm tertiary aluminum lithium alloy clean scraps, and briquetting to obtain cake-shaped aluminum lithium waste with the size of phi 100-150 mm; the mass percentage of the cake-shaped aluminum lithium waste in the aluminum lithium mixed waste obtained in the step (1) is 30-70%.

Preferably, the drying condition in the step (2) is drying for 2-4 hours at 120-250 ℃.

Preferably, during the smelting in the step (2), vacuumizing to 0.1-10 Pa, and introducing 1000-3000 Pa argon.

Preferably, the vacuum melting equipment in the step (2) is a vacuum induction melting furnace.

Preferably, the impurity removing agent in the step (2) is at least one of B, Be, La and Ce, and the mass percentage of the added impurity removing agent is 0.03-0.15%.

Preferably, in the refining process in the step (2), the mechanical rotor stirring is carried out while introducing argon, the stirring speed is 60-150 r/min, and the ventilation amount of argon is 0.1-1.0L/min.

Preferably, when the casting molding is carried out in the step (3), the molten metal obtained in the step (2) is directly added into the aluminum-lithium alloy new material melt with the same components in a liquid transferring mode to prepare a regenerated ingot, wherein the mass percentage of the added molten metal is 5-30%.

Preferably, the refiner in the step (3) is any one of master alloys Al-Ti-B, Al-Ti-C and Al-Ti-C-Sr, and the mass percent of the added refiner is 0.03-0.2%.

Preferably, the multi-layer filtration in step (3) is performed by: and sequentially filtering by using a 3-8-mesh stainless steel net, a 10-40-mesh titanium net and a 10-20-mesh magnesia ceramic filter disc layer by layer.

Preferably, after the aluminum lithium alloy regenerated ingot obtained in the step (3) is obtained, the aluminum lithium alloy regenerated ingot obtained in the step (3) is subjected to material proportioning and remelting with a new aluminum lithium alloy material with the same composition in a raw material form, and the mass percentage of the added aluminum lithium alloy regenerated ingot is 10-50%.

The invention has the beneficial effects that:

1. the method adopts a vacuum medium-frequency induction fusion casting process to recover the aluminum lithium alloy waste scraps, isolates air under the vacuum condition, and reduces the oxidation burning loss of the aluminum lithium alloy waste scraps; introducing a certain amount of protective gas to ensure that the pressure in the furnace is higher than the vapor pressure of the saturated values of the lithium and magnesium elements, thereby preventing the elements from being burnt and ensuring the components of the regenerated ingot casting to be stable; the method has the advantages that the magnesium oxide crucible is adopted to recover the aluminum lithium alloy waste, the melt is continuously stirred through electromagnetic induction, the contact time of the aluminum lithium alloy waste and the atmosphere in the furnace is reduced, oxidation burning loss caused by insufficient vacuum degree or insufficient purity of protective gas is prevented, accordingly, a high-purity aluminum lithium alloy regeneration cast ingot is obtained, and effective recovery of the aluminum lithium alloy waste and waste is realized.

2. The method adopts twice refining and a multi-stage filtering mode to recover the aluminum-lithium alloy waste scraps, and the original oxides of the waste scraps are agglomerated by mechanical stirring in the refining process, float upwards under the drive of argon and agglomerate on the surface of the melt, so that the gas and slag content in the melt is effectively reduced, and the melt is purified; in the filtering process, the separation and adsorption of fine impurities in the aluminum lithium alloy melt are realized through filter screens with different pores and different materials, and the aluminum lithium alloy melt is further purified.

3. In the process of smelting the aluminum lithium alloy waste scraps, the impurity removing agent is added to eliminate metal and nonmetal impurities introduced by partial aluminum lithium alloy waste scraps, the refiner is added to refine aluminum lithium alloy regeneration ingot casting grains, and the modified aluminum lithium alloy eutectic structure is refined, so that the high-quality aluminum lithium alloy regeneration ingot casting with refined high-purity grains is obtained.

4. The method has the advantages that the melt is purified by adopting various means such as an impurity removing agent, a refiner and the like, the preparation of the high-quality aluminum-lithium alloy waste scrap regeneration cast ingot is realized, the recovery efficiency is high compared with the conventional method, the quality of the regeneration cast ingot is good, the labor intensity and the environmental pollution in the recovery process are greatly reduced, the regeneration cast ingot can be subjected to deformation processing such as forging, extrusion, rolling and the like to prepare an aluminum-lithium alloy finished product or a semi-finished product, the comprehensive performance of the obtained product is equivalent to that of the newly prepared aluminum-lithium alloy product, and the recovered and regenerated aluminum-lithium alloy product can still be used in the original field without degradation. The method can effectively recycle the aluminum lithium alloy waste scraps generated in the fields of aerospace, electronic devices and the like, is safe and environment-friendly, has high production efficiency and high quality of regenerated cast ingots, can still be used in the original field without degradation, and provides an effective way for recycling the aluminum lithium alloy.

Detailed Description

In order to make the technical purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention are further described with reference to specific examples, which are intended to explain the present invention and are not to be construed as limiting the present invention, and those who do not specify a specific technique or condition in the examples follow the techniques or conditions described in the literature in the art or follow the product specification.

The procedures of grinding, crushing, magnetic separation, screening, briquetting, stirring, filtering and the like adopted in each embodiment are all carried out by adopting the prior art.

The grades and alloy compositions of the aluminum-lithium alloys according to the examples and comparative examples of the present invention are shown in Table 1.

Table 1 aluminum lithium alloy designations and alloy compositions.