Process for reducing iron in an al-si alloy

Abstract

The present application relates to the technical field of aluminum smelting, and particularly provides a method for reducing iron in aluminum-silicon alloy. The method comprises the following steps: 1) mixing aluminum melt and Ni, so that the mass ratio of Ni / Fe in the aluminum melt is 0.5-2.0; 2) adjusting the temperature of the aluminum melt treated in step 1) to 635-650 DEG C, and keeping the temperature for 20-45 min; 3) adjusting the temperature of the aluminum melt treated in step 2) to 605-631 DEG C, and keeping the temperature for 15-45 min; and 4) adjusting the temperature of the aluminum melt treated in step 3) to 575-594 DEG C, and keeping the temperature for 15-55 min. Compared with the prior art, the present application provides a method for reducing iron in Al-Si alloy by adding Ni, the main precipitate is Al9FeNi, the gradient holding temperature is set, the iron is reduced in layers, the iron reduction efficiency is high, the precipitation time is short, the aluminum liquid is not polluted and can be used, and the precipitate can be recycled and remelted for use.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum smelting, and more particularly to a method for reducing iron in aluminum-silicon alloy. BACKGROUND

[0002] Iron has always been considered as a harmful impurity in cast alloys and is limited. Because the solid solubility of iron in aluminum alloy is very low, once exceeding the solid solubility limit, coarse needle-like or flaky iron-rich phases are formed, which are hard and brittle, seriously cut the matrix, become the source of stress concentration, and greatly reduce the mechanical properties of aluminum alloy. In addition, the coarse needle-like or flaky iron-rich phases will hinder the flow of liquid between dendrites during feeding, thereby more easily producing shrinkage.

[0003] At present, with the continuous deepening of the influence of the lightweight design concept, automobile manufacturers have accelerated the research on automobile lightweight to compete for market share. Automobile lightweight has become an inevitable development trend. For example, ZL101 alloy is applied to the caliper of new energy vehicles, heat treatment-free aluminum alloy is applied to integrated large parts, and ZL109 alloy is applied to diesel engine pistons. The iron content of these alloy aluminum alloys is strictly controlled. Due to various factors such as smelting tools and raw materials in contact with aluminum liquid, iron is easily dissolved into the aluminum liquid, and the iron content slowly increases, which is difficult to remove. This poses a great challenge to the reuse of aluminum alloy or the use of other aluminum alloys as recycled materials.

[0004] In order to improve the iron removal effect on aluminum alloy, the current technical solutions are: on the one hand, adding Mn, Co, Mo, Cr, Ti and Be elements to the aluminum melt to change the morphology of iron-rich phases, but the essence does not reduce the Fe content, only reduces the influence range of alloy performance, and the iron content in the alloy will gradually increase; on the other hand, adding iron removal agent to react with Fe in the alloy melt to capture slag or produce precipitates to achieve the purpose of iron removal.

[0005] At present, the Chinese patent with the authorization announcement number CN 111254303 B, "Method for improving morphology of iron-rich phase in recycled aluminum and reducing iron", indicates that the iron reduction method mainly adds Mn or B elements, and the aluminum-silicon alloy precipitates mainly consist of Al 15 (FeMn)3Si2, which is greatly affected by the content of silicon element and has poor iron reduction efficiency for aluminum-silicon alloy. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a method for reducing iron in aluminum-silicon alloy, adding Ni to the aluminum-silicon alloy, setting a gradient holding temperature, and reducing iron in layers, so as to shorten the precipitation time.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0008] A method for reducing iron in an aluminum-silicon alloy, comprising:

[0009] 1) mixing aluminum melt and Ni, so that the mass ratio of Ni / Fe in the aluminum melt is 0.5-2.0;

[0010] 2) adjusting the temperature of the aluminum melt after step 1) to 635-650℃, and holding for 20-45 min;

[0011] 3) adjusting the temperature of the aluminum melt after step 2) to 605-631℃, and holding for 15-45 min;

[0012] 4) adjusting the temperature of the aluminum melt after step 3) to 575-594℃, and holding for 15-55 min.

[0013] The chemical reaction mainly occurring in step 2) of the present application is: L-Al+Al 13 Fe4=(Al)+Al9FeNi+Al8Fe2Si2;

[0014] The chemical reaction mainly occurring in step 3) is: L-Al+Al8Fe2Si=(Al)+Al9FeNi+Al8Fe2Si2;

[0015] The chemical reaction mainly occurring in step 4) is: L-Al+Al8Fe2Si=(Al)+(Si)+Al9FeNi;

[0016] L-Al in the above formula represents the liquid phase of the aluminum alloy containing the nickel component, and is preferably an aluminum-nickel alloy or pure nickel; and the precipitates produced in steps 2)-4) are all Al9FeNi.

[0017] In the present application, the aluminum melt and Ni are mixed so that the mass ratio of Ni / Fe in the aluminum melt is 0.7-1.2; during the mixing process, it is preferable to include stirring the system so that the Ni element is uniformly distributed in the aluminum melt; and during the mixing process, it is also preferable to include removing solid impurities in the system.

[0018] In the present application, step 2) is specifically adjusting the temperature of the aluminum melt after step 1) to 637-641℃, and holding for 36-40 min;

[0019] Step 3) is specifically adjusting the temperature of the aluminum melt after step 2) to 609-624℃, and holding for 32-44 min;

[0020] Step 4) is specifically adjusting the temperature of the aluminum melt after step 3) to 576-586℃, and holding for 34-48 min.

[0021] In the present application, step 2) is specifically: the temperature of the aluminum melt after step 1) is adjusted to 637-640℃, and the temperature is maintained for 38-40min.

[0022] Step 3) is specifically: the temperature of the aluminum melt after step 2) is adjusted to 609-620℃, and the temperature is maintained for 38-44min.

[0023] Step 4) is specifically: the temperature of the aluminum melt after step 3) is adjusted to 576-582℃, and the temperature is maintained for 40-48min.

[0024] In the present application, the Ni is mixed with the aluminum melt in the form of aluminum-nickel alloy or pure nickel; after the Ni is mixed with the aluminum melt, heating is performed to 847-892℃ before the treatment of step 2); the heating time is 15-25min; the mixing is preferably: adding Ni into the aluminum melt; stirring is preferably performed on the system during the mixing to make the Ni element uniformly distributed in the melt; and solid impurities in the system after the mixing are preferably removed.

[0025] In an embodiment of the present application, during the mixing of the Ni with the aluminum melt, the liquid surface is gently stirred with a preheated skimmer to ensure that there is no solid charge on the liquid surface, and then the liquid surface is stirred several times with a preheated stirring rod to remove the surface dross.

[0026] In the present application, the Fe content in the aluminum-silicon alloy is 0.5-4wt%, preferably 1-4wt%; and the Si content is 4-13wt%.

[0027] In the present application, the aluminum melt is obtained by heating the aluminum-silicon alloy to 750-770℃; the temperature maintaining time is 60-120min; and stirring is preferably performed on the system during the temperature maintaining. The heating and temperature maintaining treatment makes the aluminum-silicon alloy in a molten state.

[0028] In the present application, the aluminum-nickel alloy is one or more of AlNi10, AlNi20, and AlNi30.

[0029] In order to further obtain aluminum ingots of standard grades, the iron reduction method of the aluminum-silicon alloy further comprises: heating the aluminum melt after step 4) to 780-800℃, maintaining the temperature for 30-60min, and cooling to obtain an aluminum ingot; preferably, cooling to 740-760℃, mixing the melt with a modifier to perform refining; the modifier comprises strontium or phosphorus; the refining is performed under stirring at a speed of 350-400r / min, and the refining time is 8-10min; after the refining, the system is preferably mixed with a slagging agent to remove the slag, and the aluminum ingot is poured; the addition amount of the slagging agent is 0.5-1kg per 500kg of aluminum water.

[0030] The application provides a method for removing iron from an Al-Si alloy with the addition of Ni, and the main precipitate is Al9FeNi, a gradient holding temperature is set, iron is removed in stages, and the precipitate composition is single and stable, the iron removal efficiency is high, the precipitate time is short, the aluminum liquid is not polluted and can be used, and meanwhile, the Al9FeNi precipitate can be recycled and remelted for use as a high-temperature heat-resistant phase.

[0031] It is proved by the examples of the application that the iron removal rate of the Al-Si alloy is 64%-87% by using the method of the application, compared with the iron removal rate of 31.7% in the comparative example 1, the method of the application has an outstanding iron removal effect. The aluminum ingot finally prepared in the examples of the application fully meets the component requirements of the standard grade, and it can be seen that the application realizes the recycling of the aluminum alloy. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is an Al9FeNi precipitate diagram obtained in the example 1 of the application;

[0033] Figure 2 is the metallographic structure of the Al-Si alloy before (A) and after (B) iron removal in the example 1 of the application;

[0034] Figure 3 is the metallographic structure of the Al-Si alloy before (A) and after (B) iron removal in the example 2 of the application;

[0035] Figure 4 is the metallographic structure of the Al-Si alloy before (A) and after (B) iron removal in the example 3 of the application;

[0036] Figure 5 is a diagram of the change trend of the Fe and Ni contents with time during the iron removal process in the example 1 of the application;

[0037] Figure 6 is a diagram of the change trend of the Fe and Ni contents with time during the iron removal process in the example 2 of the application;

[0038] Figure 7 is a diagram of the change trend of the Fe and Ni contents with time during the iron removal process in the example 3 of the application;

[0039] Figure 8 is a diagram of the change trend of the Fe and Ni contents with time during the iron removal process in the comparative example 1 of the application. DETAILED DESCRIPTION

[0040] The technical solutions of the application will be described clearly and completely in combination with the examples of the application. Obviously, the described examples are only some of the examples of the application, but not all the examples. Based on the examples in the application, all the other examples obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0041] In order to further illustrate the present application, the following examples are given in detail. The raw materials used in the following examples of the present application are all commercially available.

[0042] Example 1-3

[0043] 1) Prepare a certain weight of alloy 1, alloy 2, alloy 3 respectively, put them into a smelting furnace, the Fe content is 1-4wt%, the silicon content is 4-13wt%, heat to 750-770℃, keep for 60-120min, the alloy is in a molten state. The composition table range of alloy 1, alloy 2, alloy 3 is shown in Table 1.

[0044] Table 1 composition of example alloy (wt%)

[0045] No. Si Fe Mg Mn Cu Zn Ti Al Example 1 Alloy 1 6.8 3.50 0.35 0.05 0.1 0.05 0.2 Bal. Example 2 Alloy 2 8.5 2.56 0.5 0.6 0.2 / 0.1 Bal. Example 3 Alloy 3 12.6 1.76 1.0 / 1.0 / 0.2 Bal.

[0046] 2) Add 1.78-3.45wt% of AlNi10 intermediate alloy to the aluminum-silicon alloy melt, heat the temperature of the aluminum water to 847-892℃, keep for 15-25min, so that the AlNi10 intermediate alloy is completely dissolved. Gently stir the liquid surface with a preheated skimmer, make sure that there is no solid charge on the liquid surface, then stir several times with a preheated stirring rod, remove the surface dross, and make the Ni element uniformly distributed in the melt. The added Ni composition is shown in Table 2.

[0047] Table 2 added Ni composition table (wt%)

[0048] No. Add Ni Example 1 Alloy 1 3.45 Example 2 Alloy 2 1.95 Example 3 Alloy 3 1.78

[0049] 3) Keep the temperature of the aluminum liquid at 578-664℃, keep for 95-155min. Take measures in three steps, as shown in Table 3, to gradually produce Al9FeNi precipitates, the iron removal rate is high, and the Al9FeNi precipitates are as shown in Table 3. Al9FeNi precipitates are high-temperature stable phases, which generally play a heat-resistant strengthening role in Al-Si multi-element alloys, the temperature range is 350-400℃, in Table 3, L-Al represents the liquid phase of aluminum alloy containing nickel components. Figure 1

[0050] Table 3 process parameters, iron removal rate, chemical reaction and precipitates in three steps

[0051]

[0052] Table 4 composition of alloy after iron removal (wt%)

[0053]

[0054] ​From Table 4 and Table 1, the iron removal rates of Examples 1-3 are 64.41%, 78.83%, and 86.68%, respectively.

[0055] 4) In order to further utilize the aluminum alloy after iron removal, the aluminum melt after iron removal is transferred to a refining furnace and heated to 780-800°C, and according to the difference between the actual composition of the aluminum melt and the design composition of ZL101, ZL109 or other non-standard alloy, (silicon, magnesium and other raw and auxiliary materials can be supplemented), and the temperature is maintained for 30-60 min.

[0056] 5) The temperature is reduced to 740-760°C, strontium modifier is added, the degassing machine is started, the rotor and baffle automatically sink, and the automatic refining stage is entered. After degassing, the rotor rises, the air hole of the rotor is immediately dredged with a tool, the molten slag on the liquid surface is stirred with a slag ladle, and the floating slag on the surface of the aluminum liquid is cleaned. The rotor speed is 350-400 rpm, the refining time is 8-10 min, and the air flow is 0.6-0.8 m 3 / h. The alloy after iron removal and the addition of modifier content are shown in Table 5. The metallographic structures of Examples 1-3 before iron removal and after the addition of modifier are shown in Figures 2-4 .

[0057] Table 5 Alloy after iron removal and addition of modifier content (wt%)

[0058] Sr P Example 1 0.151 0 Example 2 0.162 0 Example 3 0 0.0032

[0059] 6) According to the separation of the aluminum slag after refining, 0.5-1 kg of slag breaking agent can be added to the surface of 500 kg of aluminum water, and the molten slag on the liquid surface is stirred with a slag ladle for at least 2 min, and then the floating slag on the surface of the aluminum water is cleaned. The molten slag is poured into a slag frying platform or a slag frying barrel, and the remaining aluminum water can be poured into ZL101, ZL109 standard grade or other non-standard alloy aluminum ingots.

[0060] In Examples 1-3, the trends of Fe and Ni content with time at different temperatures are analyzed.

[0061] The results of Example 1 are shown in Table 6 and Figure 5 .

[0062] Table 6 Trends of Fe and Ni content with time at different temperatures in Example 1

[0063]

[0064] The results of Example 2 are shown in Table 7 and Figure 6 .

[0065] Table 7

[0066]

[0067]

[0068] The results of Example 3 are shown in Table 8 and Figure 7

[0069] Table 8

[0070]

[0071] Comparative Example 1

[0072] Comparative Example 2 was conducted in the same manner as Example 1, except that the holding temperature of the aluminum melt was adjusted, and 3.22 wt% of a Ni component was added to the aluminum-silicon alloy melt. The results of Comparative Example 2 are shown in Table 9 and Figure 8

[0073] Table 9

[0074]

[0075]

[0076] The above description of disclosed embodiments allows those skilled in the art to make and use the present application. Numerous modifications to these embodiments will be apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.​​

Claims

1. A method for reducing iron content in aluminum-silicon alloys, characterized in that, include: 1) Mix molten aluminum with Ni, such that the mass ratio of Ni / Fe in the molten aluminum is 0.5~2.0; 2) Adjust the temperature of the molten aluminum after step 1) to 635~650℃ and hold for 20~45 minutes; 3) Adjust the temperature of the molten aluminum after step 2) to 605~631℃ and hold for 15~45 minutes; 4) Adjust the temperature of the aluminum melt after step 3) to 575~594℃ and hold for 15~55 minutes.

2. The method for reducing iron content in aluminum-silicon alloys according to claim 1, characterized in that, The aluminum melt and Ni are mixed so that the Ni / Fe mass ratio in the aluminum melt is 0.7 to 1.

2.

3. The method for reducing iron content in aluminum-silicon alloys according to claim 1, characterized in that, Step 2) Specifically: Adjust the temperature of the molten aluminum after step 1) to 637~641℃ and hold for 36~40 minutes; Step 3) Specifically: Adjust the temperature of the molten aluminum after step 2) to 609~624℃ and hold for 32~44 minutes; Step 4) Specifically: Adjust the temperature of the aluminum melt after step 3) to 576~586℃ and hold for 34~48 minutes.

4. The method for reducing iron content in aluminum-silicon alloys according to claim 1, characterized in that, Step 2) Specifically: Adjust the temperature of the molten aluminum after step 1) to 637~640℃ and hold for 38~40 minutes; Step 3) Specifically: Adjust the temperature of the molten aluminum after step 2) to 609~620℃ and hold for 38~44 minutes; Step 4) Specifically: Adjust the temperature of the aluminum melt after step 3) to 576~582℃ and hold for 40~48 minutes.

5. The method for reducing iron content in aluminum-silicon alloys according to claim 1, characterized in that, After mixing Ni with the aluminum melt, heat it to 847~892℃ before proceeding with step 2).

6. The method for reducing iron content in aluminum-silicon alloys according to claim 5, characterized in that, The heating time is 15-25 minutes.

7. The method for reducing iron content in aluminum-silicon alloys according to claim 1, characterized in that, The aluminum-silicon alloy contains 0.5-4 wt% Fe and 4-13 wt% silicon.

8. The method for reducing iron content in aluminum-silicon alloys according to claim 1, characterized in that, The aluminum melt is obtained by heating an aluminum-silicon alloy to 750~770℃.

9. The method for reducing iron content in aluminum-silicon alloys according to claim 1, characterized in that, The Ni is mixed with the aluminum melt in the form of an aluminum-nickel alloy or pure nickel.

10. The method for reducing iron content in aluminum-silicon alloys according to claim 9, characterized in that, The aluminum-nickel alloy is one or more of AlNi10, AlNi20, and AlNi30.

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