Method for separating Fe impurity element from aluminum alloy waste

Abstract

The invention belongs to the technical field of non-ferrous metal smelting, and particularly relates to a method for separating Fe impurity elements in aluminum alloy waste. Testing the components of the aluminum alloy waste, and determining the Fe content; melting the waste materials and adjusting the components. Casting an alloy ingot, cutting a cylindrical test bar, heating and solidifying; in the directional solidification process, Fe and transition metal elements are segregated towards one end of the sample, and an Fe-containing intermetallic compound is formed. The segregation of Fe impurity elements is promoted by utilizing the distribution coefficient difference of Fe impurity elements and alpha-Al solute and combining zone melting with directional solidification. And after the Fe impurity element enrichment end alloy is cut off, the process is repeated again, and the Fe impurity element content in the alloy is gradually reduced through multiple times of treatment until the alloy with the ultralow Fe impurity element content is obtained. According to the method, segregation and separation of the Fe element are achieved by combining zone melting with the directional solidification technology, the alloy with the extremely low Fe element content is obtained through multiple times of circulation, and high-quality regeneration of the aluminum alloy waste is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal smelting, and in particular relates to a method for separating Fe impurity elements from aluminium alloy waste. Background Art

[0002] Aluminum alloys are widely used in aerospace, transportation and other fields due to their low density, excellent mechanical properties, easy processing and corrosion resistance. Fe is one of the main harmful elements in aluminum alloys. It has low solubility and is easy to generate needle-shaped intermetallic compounds, which seriously damages the mechanical properties of the alloy and is difficult to remove. With the repeated recycling of aluminum alloys, Fe impurity elements gradually accumulate, resulting in the degradation of the alloy. Therefore, reducing the Fe content in aluminum alloys is of great significance for their high-quality recycling.

[0003] Chinese invention patent CN107619958A discloses a method for removing Fe from a regenerated Al-Mg-Si alloy, in which a certain amount of Mn is added to an iron-containing aluminum melt to form an α-AlFeMnSi phase, and the α-AlFeMnSi phase is separated by gravity sedimentation, thereby reducing the Fe content in the alloy. However, relying solely on gravity sedimentation, the separation time required is long, the separation efficiency is low, and a large amount of Fe impurity elements still remain in the alloy. Chinese invention patent CN103740947A discloses a deironing agent, in which a certain proportion of borax, manganese chloride, calcium chloride, calcium oxide, magnesium carbonate, sulfur, etc. are mixed to obtain a deironing agent, and the deironing agent is added to the molten waste aluminum for stirring, which can reduce the Fe content in the melt, but the deironing agent has a low reaction efficiency with the melt in this method, the required reaction time is long, and the deironing efficiency is limited.

[0004] One of the advantages of directional solidification technology is that it can separate elements with large differences in solubility in the solid and liquid phases. The Fe impurity element has a high solubility in the liquid phase aluminum alloy, while the solubility of Fe in the solid phase α-Al is only 0.01wt.%, so the Fe impurity element can be separated and removed by directional solidification technology. In view of the problem of low separation efficiency of Fe impurity elements in recycled aluminum alloys, the present invention uses a directional solidification method to separate Fe from recycled aluminum alloys, which can greatly reduce the Fe content in the melt and effectively promote the high-quality regeneration of recycled aluminum waste. Summary of the invention

[0005] In view of the problem that the current aluminum alloy recycling waste has low Fe removal efficiency, resulting in its inability to maintain grade regeneration, the present invention proposes a method for separating Fe impurity elements from aluminum alloy waste to improve the separation efficiency of Fe impurity elements and promote high-quality regeneration of aluminum alloy waste.

[0006] In order to solve the above-mentioned technical problems, this application provides the following technical solutions:

[0007] The present invention provides a method for separating Fe impurity elements from aluminum alloy waste, comprising the following steps:

[0008] S1: melting the aluminum alloy scrap, testing its composition, and adjusting the elemental composition of the aluminum alloy scrap; wherein the elemental composition is adjusted according to [Fe], [M], and [Si] of 1:3-10:4-12, wherein [Fe] is the mass fraction of Fe, [Si] is the mass fraction of Si, and [M] is the total mass fraction of the transition metal element M; and the adjustment method is to add the corresponding chemical elements;

[0009] S2: Casting the adjusted aluminum alloy scrap into ingots to obtain round bar samples;

[0010] S3: placing the round rod sample in a ceramic crucible for smelting, keeping the temperature, and then gradually solidifying the liquid alloy from top to bottom to obtain a solidified alloy; the smelting is performed by induction heating using a heating coil, and the solidification method is to vertically withdraw the ceramic crucible and cool it using a cooling medium;

[0011] S4: removing the Fe element-enriched alloy at the upper end of the solidified alloy to obtain an alloy with low Fe impurity element content;

[0012] S5: Take the alloy with low Fe impurity element content, repeat steps S1-S4, and complete the method for separating Fe impurity elements from aluminum alloy scrap.

[0013] Preferably, the aluminum alloy scrap is selected from a mixture of one or several aluminum scraps; in the aluminum alloy scrap, the Si content is 0-10wt%, and the Fe element content is 0.1-3wt%.

[0014] Preferably, the transition metal element M is selected from one or more of Mn, Cr, Co, Mo, Co, Be and W.

[0015] Preferably, in step S2, the alloy casting temperature is 730-780°C, and the cooling rate during ingot casting is 200-600K / S.

[0016] Preferably, the round rod sample has a diameter of 3-10 mm and a length of 40-150 mm.

[0017] Preferably, in step S3, the power of induction heating is 0.3-1.5Kw, and the vacuum degree in the furnace is higher than 5×10 - 3 Pa, the regional melting temperature is 680-750℃.

[0018] Preferably, in step S3, during smelting and heat preservation, a directional solidification furnace is used, and Ar or N2 is used for protection.

[0019] Preferably, in step S3, during solidification, the cooling medium is a low melting point liquid metal, and the pulling rate of the ceramic crucible is 1-20 mm / min, so that the cooling rate of the alloy is maintained at 50-300 K / min.

[0020] Preferably, in step S4, the removal method is to cut off the Fe element-enriched alloy at the upper end of the solidified alloy, and the length of the cut off is 0.3-5% of the total length of the round rod sample.

[0021] Preferably, in step S5, steps S1-S4 are repeated more than three times.

[0022] Specifically, the method for separating Fe impurity elements from aluminum alloy scrap comprises the following steps:

[0023] 1) Composition adjustment: melt the aluminum alloy scrap and perform composition test, and then adjust the composition according to the Fe content in the scrap according to Wt% (Fe): Wt% (M): Wt% (Si) = 1:3-10:4-12, where M is a transition metal element such as Mn, Cr, Co, Mo, Co, Be, or W;

[0024] 2) Sampling: After the composition adjustment is completed, the ingot is cast and the round bar sample is taken;

[0025] 3) Directional solidification: Place the round rod sample in a ceramic crucible, vertically place it in a heating coil for melting and heat preservation, then pull the ceramic crucible downward in the vertical direction at a pulling rate of 1mm / min-20mm / min to gradually solidify the liquid alloy until the alloy is completely solidified. Take out the sample and remove the Fe element enriched alloy at the top to obtain an alloy with low Fe impurity element content. Repeat the above process more than 3 times using the alloy with low Fe impurity element content until an alloy with ultra-low Fe impurity element content is obtained.

[0026] The technical solution of the present invention has the following advantages over the prior art:

[0027] The method for separating Fe impurity elements from aluminum alloy waste disclosed in the present invention realizes efficient removal of Fe impurity elements through directional solidification technology, and effectively solves the problem that recycled aluminum alloy waste cannot be regenerated with maintained grade due to low Fe removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a comparative photo of the original structure before Fe removal and the metallographic structure before and after Fe removal in Example 1 of the present invention; wherein, (a) the alloy structure before Fe impurity element separation; (b) the lower structure of the alloy after the solidification process is repeated once; (c) the upper structure of the alloy after the solidification process is repeated once; (d) the lower structure of the alloy after the solidification process is repeated six times; (e) the upper structure of the alloy after the solidification process is repeated six times;

[0029] Figure 2 The following are comparison photos of the original structure before Fe removal and the metallographic structure before and after Fe removal in Example 2 of the present invention; wherein, (a) the alloy structure before solidification treatment; (b) the lower structure of the alloy after the solidification process is repeated once; (c) the upper structure of the alloy after the solidification process is repeated once; (d) the lower structure of the alloy after the solidification process is repeated 10 times; (e) the upper structure of the alloy after the solidification process is repeated 10 times;

[0030] Figure 3 The following are comparison photos of the original structure before Fe removal and the metallographic structure before and after Fe removal of Example 3 of the present invention; wherein, (a) the alloy structure before solidification treatment; (b) the lower structure of the alloy after the solidification process is repeated once; (c) the upper structure of the alloy after the solidification process is repeated once; (d) the lower structure of the alloy after the solidification process is repeated 15 times; (e) the upper structure of the alloy after the solidification process is repeated 15 times;

[0031] Figure 4 The present invention implements example 4 and compares the original structure before Fe removal and the metallographic structure before and after Fe removal; wherein, (a) alloy structure before solidification treatment; (b) lower structure of the alloy after the solidification process is repeated once; (c) upper structure of the alloy after the solidification process is repeated once; (d) lower structure of the alloy after the solidification process is repeated 20 times; (e) upper structure of the alloy after the solidification process is repeated 20 times. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0033] Example 1

[0034] In this embodiment, Fe impurity elements are separated from recycled aluminum scrap with an Fe content of 2.1wt%, and the specific steps are as follows:

[0035] (1) 4000 series and 6000 series aluminum alloy scraps were placed in a crucible for melting and casting a standard spectrum sample, and the Fe content, Si content, and Mg content were measured to be 2.1wt%, 4wt%, and 0.29wt%, and then Mn agent and Al-Si master alloy were added to adjust the composition to Fe: 0.52wt%, Si: 7wt%, Mg: 0.29wt%, and Mn: 2wt%;

[0036] (2) Adjust the alloy composition and cut the ingot Test rod, machined to remove surface oxide scale;

[0037] (3) Alloy melting: The round rod is placed in a ceramic crucible and placed vertically in a heating coil together with the crucible for induction heating zone melting. The coil heating power is set to 1 kW and the vacuum degree in the furnace is 6 × 10-3 Pa, melting temperature is 740℃;

[0038] (4) Directional solidification: After the melting is completed, the pulling rate of the ceramic crucible is set to 10 mm / s and the temperature gradient is set to 10 k / mm. The ceramic crucible is gradually immersed in the gallium-indium alloy until the alloy is completely immersed in the cooling medium. The sample is taken out, and after removing the upper 5% length of the sample, the process is repeated for the remaining part.

[0039] (5) Step (4) was repeated 6 times, and the Fe content of the final alloy was measured to be 0.1%, and the Fe removal efficiency reached 95.2%.

[0040] The comparison of the organization before and after Fe removal in this embodiment is as follows: Figure 1 shown.

[0041] Example 2

[0042] In this embodiment, Fe impurity elements are separated from recycled aluminum scrap with an Fe content of 0.25wt%, and the specific steps are as follows:

[0043] (1) 1000 series and 6000 series aluminum alloy scraps were placed in a crucible for melting, and a standard spectrum sample was cast in front of the furnace. The Fe content, Si content, and Mg content were measured to be 0.31wt%, 0.8wt%, and 0.5wt%, and then Mn and Cr agents were added to adjust the composition of the Al-Si master alloy to Fe: 0.25wt%, Si: 2.5wt%, Mg: 0.5wt%, Mn: 2.5wt%, and Cr: 0.5wt%;

[0044] (2) After the composition is adjusted, the alloy is cast into Test rods are machined to remove the surface oxide scale;

[0045] (3) Alloy smelting: The round rod is placed in a ceramic crucible and placed vertically in a heating coil together with the crucible for induction heating zone smelting. The coil heating power is set to 1.5 kW and the vacuum degree in the furnace is 5.5 × 10 -3 Pa, melting temperature is 760℃;

[0046] (4) Directional solidification: After the melting is completed, the pulling rate of the ceramic crucible is set to 20 mm / s and the temperature gradient is set to 5 k / mm. The ceramic crucible is gradually immersed in the gallium-indium alloy until the alloy is completely immersed in the cooling medium. The sample is taken out, and after removing the upper 7% length of the sample, the process is repeated for the remaining part.

[0047] (5) Step (4) was repeated 10 times, and the Fe content of the final alloy was measured to be 0.08%, and the Fe removal efficiency reached 74.2%.

[0048] The comparison of the organization before and after Fe removal in this embodiment is as follows: Figure 2 shown.

[0049] Example 3

[0050] In this embodiment, Fe impurity elements are removed from recycled aluminum scrap with an Fe content of 1.2wt%, and the specific steps are as follows:

[0051] (1) 5000 series and 4000 series aluminum alloy scraps were placed in a crucible for melting, and a standard spectrum sample was cast in front of the furnace. The Fe content, Si content, and Mg content were measured to be 1.2wt%, 1.2wt%, and 0.5wt%, and then Mn agent was added. The Al-Si master alloy was adjusted to have a composition of Fe: 0.31wt%, Si: 4wt%, Mg: 0.5wt%, Mn: 1.5wt%, Co: 1.5wt%, and Ni: 0.6wt%;

[0052] (2) After the composition is adjusted, the alloy is cast into Test rods are machined to remove the surface oxide scale;

[0053] (3) Alloy melting: The round rod is placed in a ceramic crucible and placed vertically in a heating coil together with the crucible for induction heating zone melting. The coil heating power is set to 0.7 kW and the vacuum degree in the furnace is 7 × 10 -3 Pa, melting temperature is 730℃;

[0054] (4) Directional solidification: After the melting is completed, the pulling rate of the ceramic crucible is set to 5 mm / s, the temperature gradient is set to 15 k / mm, and the ceramic crucible is gradually immersed in the gallium-indium alloy until the alloy is completely immersed in the cooling medium. The sample is taken out, and after removing the upper 7% length of the sample, the process is repeated for the remaining part;

[0055] (5) Step (4) was repeated 15 times, and the Fe content of the final alloy was measured to be 0.11%, and the Fe removal efficiency reached 74.2%.

[0056] The comparison of the organization before and after Fe removal in this embodiment is as follows: Figure 3 shown.

[0057] Example 4

[0058] In this embodiment, Fe impurity elements are separated from recycled aluminum scrap with an Fe content of 4.99wt%, and the specific steps are as follows:

[0059] (1) 4000 series aluminum alloy scrap was placed in a crucible for melting, and a standard spectrum sample was cast in front of the furnace. The Fe content was measured to be 4.99wt%, the Si content was 9.2wt%, and the Mg content was 0.4wt%. Subsequently, Cu, Al-Ni, Al-Ti, and Al-Be master alloys were added to adjust the composition to Fe: 0.31wt%, Si: 9.2wt%, Mg: 0.5wt%, Cu: 0.5wt%, Ni: 1.5wt%, Ti: 0.3wt%, and Be: 1.8wt%;

[0060] (2) After the composition is adjusted, the alloy is cast into Test rods are machined to remove the surface oxide scale;

[0061] (3) Alloy melting: The cylindrical test rod was placed in a ceramic crucible and placed vertically in a heating coil together with the crucible for induction heating zone melting. The coil heating power was set to 0.7 kW and the vacuum degree in the furnace was 5.8 × 10 -3 Pa, melting temperature is 730℃;

[0062] (4) Directional solidification: After the melting is completed, the pulling rate of the ceramic crucible is set to 1 mm / s, the temperature gradient is set to 20 k / mm, and the ceramic crucible is gradually immersed in the gallium-indium alloy until the alloy is completely immersed in the cooling medium. The sample is taken out, and after removing the upper 7% length of the sample, the process is repeated for the remaining part;

[0063] (5) Step (4) was repeated 20 times, and the Fe content of the final alloy was measured to be 0.18%, and the Fe removal efficiency reached 90.8%.

[0064] The comparison of the organization before and after Fe removal in this embodiment is as follows: Figure 4 shown.

[0065] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for separating Fe impurity elements from aluminum alloy waste, characterized in that: The steps include: S1: melting the aluminum alloy scrap, testing its composition, and adjusting the elemental composition of the aluminum alloy scrap; wherein the elemental composition is adjusted according to [Fe], [M], and [Si] of 1:3-10:4-12, wherein [Fe] is the mass fraction of Fe, [Si] is the mass fraction of Si, and [M] is the total mass fraction of the transition metal element M; and the adjustment method is to add the corresponding chemical elements; S2: Casting the adjusted aluminum alloy scrap into ingots to obtain round bar samples; S3: placing the round rod sample in a ceramic crucible for smelting, keeping the temperature, and then gradually solidifying the liquid alloy from top to bottom to obtain a solidified alloy; the smelting is performed by induction heating using a heating coil, and the solidification method is to vertically withdraw the ceramic crucible and cool it using a cooling medium; S4: removing the Fe element-enriched alloy at the upper end of the solidified alloy to obtain an alloy with low Fe impurity element content; S5: Take the alloy with low Fe impurity element content, repeat steps S1-S4, and complete the method for separating Fe impurity elements from aluminum alloy scrap.

2. The method for separating Fe impurity elements from aluminum alloy scrap according to claim 1, characterized in that: The aluminum alloy scrap is selected from one or a mixture of several aluminum scraps; in the aluminum alloy scrap, the Si content is 0-10wt%, and the Fe element content is 0.1-3wt%.

3. The method for separating Fe impurity elements from aluminum alloy scrap according to claim 1, characterized in that: The transition metal element M is selected from one or more of Mn, Cr, Co, Mo, Co, Be and W.

4. The method for separating Fe impurity elements from aluminum alloy scrap according to claim 1, characterized in that: In step S2, the alloy casting temperature is 730-780°C, and the cooling rate during ingot casting is 200-600K / S.

5. The method for separating Fe impurity elements from aluminum alloy scrap according to claim 1, characterized in that: The round rod sample has a diameter of 3-10 mm and a length of 40-150 mm.

6. The method for separating Fe impurity elements from aluminum alloy scrap according to claim 1, characterized in that: In step S3, the power of induction heating is 0.3-1.5Kw, and the vacuum degree in the furnace is higher than 5×10 -3 Pa, the regional melting temperature is 680-750℃.

7. The method for separating Fe impurity elements from aluminum alloy scrap according to claim 1, characterized in that: In the step S3, during smelting and heat preservation, a directional solidification furnace is used, and Ar or N2 is used for protection.

8. The method for separating Fe impurity elements from aluminum alloy scrap according to claim 1, characterized in that: In the step S3, during solidification, the cooling medium is a low melting point liquid metal, and the pulling rate of the ceramic crucible is 1-20 mm / min, so that the cooling rate of the alloy is maintained at 50-300 K / min.

9. The method for separating Fe impurity elements from aluminum alloy scrap according to claim 1, characterized in that: In the step S4, the removal method is to cut off the Fe element-enriched alloy at the upper end of the solidified alloy, and the length of the cut off is 0.3-5% of the total length of the round rod sample.

10. The method for separating Fe impurity elements from aluminum alloy scrap according to claim 1, characterized in that: In step S5, steps S1-S4 are repeated more than three times.

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