CN100392127C - Method for preparing foamed aluminum alloy products by secondary foaming - Google Patents

Abstract

The invention discloses a method for preparing foamed aluminum alloy products by secondary foaming. First, the aluminum alloy is heated to melt, and the temperature is adjusted to 630°C-680°C, calcium is added to the aluminum alloy melt, and stirred for 1-30 minutes. Then add titanium hydride and stir to make titanium hydride evenly distributed in the melt, and cool the stirred melt to obtain a primary foamed aluminum alloy preform with a porosity lower than 70%; the second step: make the above porosity lower than 70% of the primary foamed aluminum alloy prefabricated parts are put into the mold, and kept at a temperature of 700°C to 1200°C for 3 to 40 minutes, so that the primary foamed aluminum alloy prefabricated After the foamed aluminum alloy is cooled, a foamed aluminum alloy product is obtained. The method of the invention is simple and low in cost, and can be used for preparing foamed aluminum alloy special-shaped parts, sandwich structures, foamed aluminum alloy filling parts and foamed aluminum alloy products with embedded parts with uniform porosity and various porosities.

Description

Method for preparing foamed aluminum alloy products by secondary foaming

technical field

The invention relates to a method for preparing a foamed aluminum alloy product, in particular to a method for preparing a foamed aluminum alloy product through secondary foaming.

Background technique

The ultra-light metal structure with closed-cell aluminum foam as the focus realizes lightweight and multi-functional structural materials due to its special pore structure, thus becoming a hot spot in aerospace and high technology.

Due to the needs of civil and high-tech fields such as automobiles, aluminum foam special-shaped parts and sandwich structures are becoming the forefront of the field of foam metal preparation. There are insurmountable difficulties in the direct preparation of special-shaped parts, sandwich structures, foamed aluminum alloy fillers, embedded parts, etc. by the traditional melt foaming method, while there are costs in the preparation of foamed aluminum special-shaped parts, sandwich structures, etc. High, unstable process and other defects.

Contents of the invention

The invention provides a method for preparing foamed aluminum alloy products by secondary foaming. The method is mainly used to prepare foamed aluminum alloy special-shaped parts with complex shapes, sandwich structures, small ball filling parts and foams with embedded parts. Various products such as aluminum alloy products, the method is simple, low in cost and reliable, and the prepared foamed aluminum alloy products have uniform pore structure and controllable porosity.

The present invention adopts following technical scheme:

A method for preparing foamed aluminum alloy products through secondary foaming, comprising the following steps:

Step 1: Heat the aluminum alloy to melt, and adjust the temperature to 630°C-680°C, add calcium equivalent to 0.5%-5% of the weight of the aluminum alloy to the molten aluminum alloy, stir for 1-30 minutes, and then add Titanium hydride equivalent to 0.5%-5% of the weight of the aluminum alloy, stirring to distribute the titanium hydride evenly in the melt, cooling the stirred melt, and obtaining a primary foamed aluminum alloy preform with a porosity lower than 70%;

Step 2: Put the above-mentioned primary foamed aluminum alloy prefabricated part with a porosity lower than 70% into the mold, and keep it warm at a temperature of 700°C to 1200°C for 3 to 40 minutes, so that the primary foamed aluminum alloy preformed Secondary foaming in the mould, cooling the foamed aluminum alloy to obtain a foamed aluminum alloy product.

Invention principle:

Titanium hydride is the driving force for the foaming of aluminum alloys. In the process of foaming, the amount of decomposition of titanium hydride has not attracted people's attention. The present invention obtains the results of the present invention on the basis of quantitative analysis of the decomposition process of titanium hydride. Technical solutions.

The effect of titanium hydride decomposition temperature on hydrogen yield: For titanium hydride decomposition kinetic equations, the curve of primary hydrogen yield f ₁ changing with time at 903k, 913k, 923k, 933k, and 943k can be calculated. Under the same decomposition time, the higher the temperature, the higher the hydrogen primary yield _f1 ; the longer the decomposition time, the higher the hydrogen primary yield _f1 . The hydrogen production rate _f1 at 670°C is more than 60% higher than that at 650°C.

The effect of titanium hydride decomposition time on hydrogen yield: It can be calculated that the secondary hydrogen yield _f2 changes with time at a temperature of 923K and a pre-decomposition time of 0s (ie, primary decomposition), 60s, 80s, 100s, 120s, and 150s. Relationship. The shape of the secondary decomposition curve is similar to that of the pre-decomposition curve, but the secondary yield f ₂ is significantly lower, and the longer the pre-decomposition time, the lower the secondary decomposition hydrogen yield f ₂ . However, even if the pre-decomposition time reaches 150s, the secondary decomposition hydrogen yield _f2 is greater than 10%.

The hydrogen production rate of the secondary decomposition of titanium hydride under the condition of continuous heating: it is the second continuous heating decomposition curve with the pre-decomposition temperature of 923k, 933k, 943k, 953k and the pre-decomposition time of 80s, and the heating rate is 1.26k/s. Under the same pre-decomposition time, the higher the pre-decomposition temperature, the lower the hydrogen yield of the secondary decomposition of continuous temperature rise. The secondary yields of hydrogen under the condition of continuous temperature rise are all greater than 10%.

The calculation of the hydrogen necessary to form the foamed aluminum alloy is as follows:

During a foaming process, most of the hydrogen generated by the decomposition of titanium hydride escapes into the air or burns due to stirring, and only a part remains in the melt to form foamed aluminum alloy. The amount of hydrogen necessary to form a foamed aluminum alloy with a certain porosity is calculated as follows: the mass of hydrogen in the melt foam before the melt is foamed and cooled.

Take the calculation of the foaming conditions of the melt foaming method as an example: the foaming temperature is T, the mass of the aluminum alloy melt is m _Al , the percentage of the added mass of titanium hydride to the aluminum alloy is a, and the hydrogen in the foamed aluminum alloy before cooling The volume is V _g , the porosity is Pr, and the average internal pressure of the bubbles is P. _During the rapid cooling process, the amount of gas released by the decomposition of titanium hydride is negligible (the porosity of the foamed aluminum alloy melt can be controlled to be low so that Make it cool quickly), so the mass m _f of the gas in the bubble before the foamed aluminum alloy is cooled is:

The total hydrogen content m ₀ of titanium hydride is:

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; al</span>}}<span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; .</span>\frac{\mathrm{<span\; class="notranslate">\; 1.94</span>}}{\mathrm{<span\; class="notranslate">\; 1.94</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 48</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Thus the mass m _f of the gas in the bubble before the foamed aluminum alloy is cooled (i.e. the hydrogen mass necessary to form the foamed aluminum alloy) accounts for the total hydrogen-containing mass m of titanium hydride The _percentage k is:

Calculating k also needs to determine _{the inside of} P, the process is as follows:

The bubble resistance is mainly composed of three parts: the static pressure P _l of the aluminum alloy melt, the additional pressure ΔP caused by the surface tension and the atmospheric pressure P _{atmospheric pressure} , which achieves a dynamic balance between the _internal pressure P of the bubble and the resistance of the bubble expansion:

P _inside = P _{atmospheric pressure} + P _l + ΔP (4)

Among them, P _l = ρ _Al .gh, under normal foaming conditions, the highest height h of foamed aluminum alloy can reach 200mm, then the maximum static pressure of the melt P _l = 0.054×10 ⁵ N/m ² , additional The pressure is ΔP=2σ/r, the surface tension of the aluminum alloy is 0.98N/m, and the average radius of the bubbles (after homogenization and stirring) is about 0.0008m~0.003m, so the maximum value of the additional pressure is about 0.0245×10 ⁵ N /m ² . For tiny bubbles, the internal pressure due to the additional pressure is relatively large, but their total volume is also very small, so the total amount is very small and can be ignored.

Therefore, it can be obtained from formula (4): P _g ≈1.09175×10 ⁵ Pa;

From (3), it can be calculated that the mass of hydrogen necessary to form the foamed aluminum alloy accounts for no more than 7.13% of the total mass of hydrogen contained in titanium hydride.

Therefore, the amount of secondary decomposition gas of titanium hydride under conventional foaming conditions (more than 10%) is greater than the amount of hydrogen necessary to form aluminum alloy foam (less than 7.13%), and secondary foaming is theoretically feasible.

The present invention obtains following technical effect:

1. The present invention utilizes the hydrogen gas produced by the decomposition of residual titanium hydride due to the incomplete decomposition of titanium hydride in the primary foaming process, so that the aluminum alloy melt after heating and melting is foamed for the second time to obtain foamed aluminum alloy; the present invention utilizes hydrogenation The thermal decomposition amount of titanium is closely related to the temperature. By controlling the primary thermal decomposition temperature to be 630-680°C, the primary thermal decomposition amount of titanium hydride is controlled, and the hydrogen decomposition amount in the second foaming process is guaranteed. Therefore, the present invention No need to do any treatment on titanium hydride, thus simplifying the process and reducing the cost.

2. The present invention does not need to press the primary foamed aluminum alloy prefabricated parts, so the method is simple and the cost is low. Relatively speaking, other methods such as powder metallurgy require higher pressure densification and thus have higher costs.

3. In the present invention, since the primary foamed aluminum alloy prefabricated part already has a certain porosity, the drainage speed of the foamed aluminum alloy is suppressed, so the pore structure of the secondary foamed aluminum alloy obtained is relatively uniform.

4. The present invention controls the thermal decomposition of titanium hydride by controlling the primary foaming temperature, and requires relatively wide control of the secondary foaming time. Therefore, a sufficiently long stirring time can be used to make the titanium hydride evenly dispersed in the foamed aluminum alloy. Therefore, the pore structure of the foamed aluminum alloy product prepared by secondary foaming is uniform.

5. The present invention is developed on the basis of the melt foaming method of calcium viscosification. The mechanism of calcium viscosification is different from that of silicon carbide ceramic particles. The viscosification produced after calcium is added to the aluminum alloy melt The main effect is the intermetallic compound; the calcium-adhesive aluminum alloy melt reacts during the stirring process to obtain uniformly distributed intermetallic compounds, so it has the characteristics of uniform viscosity. These intermetallic compounds are distributed during hot pressing and reheating. It is still uniform, so it is easy to obtain a secondary foamed aluminum alloy with uniform pore structure; and the foamed aluminum alloy increased by silicon carbide ceramics is not easy to distribute uniformly, so the prepared foamed aluminum alloy is not easy to be uniform. In addition, due to the silicon carbide ceramic particles themselves Instability can also lead to product quality issues.

6. Since the remaining titanium hydride under the primary foaming condition can generate enough hydrogen during the reheating process, the present invention can prepare secondary foamed aluminum alloy special-shaped parts with higher porosity (porosity range 50-90%), Sandwich structure, foamed aluminum alloy filled balls and other contoured fillers, foamed aluminum alloy products with embedded parts, etc., realize the contour of the foamed aluminum alloy products by changing the shape of the inner cavity of the secondary foaming mold Change. The foamed aluminum alloy products prepared by these secondary foaming methods have the characteristics of high strength, rigidity and high energy absorption, and have important application prospects.

7. The present invention performs surface treatment on aluminum plates and prefabricated parts to remove oxygen on the aluminum surface, thereby making the plate cores bonded firmly, thereby improving the mechanical properties of the structure.

8. Heating the primary foamed aluminum alloy preform with lower porosity can melt the secondary foamed aluminum alloy preform, and at the same time, the residual titanium hydride decomposes to generate hydrogen to make it foam, and obtain the secondary foamed aluminum foam Alloy, increasing the heating temperature can increase the heating speed of the preform, thereby reducing the loss of hydrogen, and can further increase the decomposition of titanium hydride, thereby increasing the porosity of the foamed aluminum alloy.

9. The present invention can manufacture the foamed aluminum alloy special-shaped parts with complex external shape with the skin, can prepare the sandwich structure with the foamed aluminum alloy as the sandwich, can prepare the foamed aluminum alloy filled ball (so-called foamed aluminum alloy filled ball refers to , the profile of foamed aluminum alloy products is spherical and has a layer of skin. effect of vibration reduction and energy absorption), various foamed aluminum alloy products with embedded parts can also be prepared, and the method is simple and the cost is low.

Description of drawings

Figure 1 is a pore structure diagram of a foamed aluminum alloy product prepared by secondary foaming (porosity 85%, pore diameter 1.5-2.5mm,)

Figure 2 is a product diagram of various shapes of foamed aluminum alloys prepared by secondary foaming (including filled balls, porosity 50%-90%, pore diameter 1-5mm)

Figure 3 is a diagram of foamed aluminum alloy special-shaped parts and fillers prepared by secondary foaming (porosity 50%-90%, pore diameter 1-5mm)

Detailed ways

Embodiment 1 A method for preparing foamed aluminum alloy products through secondary foaming, comprising the following steps:

Step 1: Heat the aluminum alloy to melt, and adjust the temperature to 630°C-680°C, add calcium equivalent to 0.5%-5% of the weight of the aluminum alloy to the molten aluminum alloy, stir for 1-30 minutes, and then add Titanium hydride equivalent to 0.5%-5% of the weight of the aluminum alloy, stirring to distribute the titanium hydride evenly in the melt, cooling the stirred melt, and obtaining a primary foamed aluminum alloy preform with a porosity lower than 70%;

Step 2: Put the above-mentioned primary foamed aluminum alloy prefabricated part with a porosity lower than 70% into the mold, and keep it warm at a temperature of 700°C to 1200°C for 3 to 40 minutes, so that the primary foamed aluminum alloy preformed Secondary foaming in the mould, cooling the foamed aluminum alloy to obtain a foamed aluminum alloy product.

Embodiment 2 A method for preparing foamed aluminum alloy products through secondary foaming, comprising the following steps:

Step 1: Heat the aluminum alloy until it melts. Among them, aluminum alloys such as ZL101, ZL102, ZL111 series alloys, or cast aluminum-copper alloys, grades such as ZL201, ZL202, ZL205 series alloys, or alloys mainly containing copper or Mainly deformed aluminum alloys containing silicon, can also be aluminum alloys containing magnesium, such as ZL301, etc., adjust the temperature to 630°C-680°C, and the temperature can be 635°C, 642°C, 650°C, 660°C, 665°C, 670°C , adding calcium equivalent to 0.5%-5% of the weight of the aluminum alloy to the molten aluminum alloy, the amount of calcium added can be selected as 0.8%, 1.2%, 1.5%, 2.0%, 2.8%, 3.5%, 4.2%, 4.7%, stirring for 1-30 minutes, the stirring time can be selected as 3 minutes, 8 minutes, 10 minutes, 15 minutes, 22 minutes, 25 minutes, the stirring speed can be 300-600rpm, and then add 0.5% of the weight of the aluminum alloy -5% titanium hydride, the addition of titanium hydride can be selected as 0.8%, 1.2%, 1.5%, 2.0%, 2.8%, 3.5%, 4.2%, 4.7%, stirring makes titanium hydride evenly distributed in the melt, It can be stirred at a speed of 800-5000rpm for 60-1000 seconds. The stirring speed can be selected as 4500rpm, 4000rpm, 3200rpm, 2500rpm, 1000rpm, 900rpm. The stirring time can be selected as 70s, 90s, 150s, 250s, 400s, 550s, 600s, 800s , 900s, cooling the stirred melt to obtain a primary foamed aluminum alloy preform with a porosity lower than 70%, for example, a porosity of 60%, 55%, 54%, 52%, 45%, 39%, 35% , 28%, 22%, 18%, 15%;

Step 2: Put the primary foamed aluminum alloy prefabricated part with a porosity lower than 70% into the mold, and keep it warm at a temperature of 700°C to 1200°C for 3 to 40 minutes, wherein the temperature can be selected as 750°C, 800°C, 850°C, 880°C, 950°C, 1000°C, 1150°C, the holding time can be selected as 5 minutes, 8 minutes, 12 minutes, 20 minutes, 27 minutes, 33 minutes, 38 minutes, so that the aluminum alloy can be foamed once The preform is secondary foamed in the mold, and the foamed aluminum alloy is cooled to obtain a foamed aluminum alloy product. The porosity ranges from 50% to 90%, which can be 50%, 60%, 70%, 80%, 85%, 90%, the aperture is 1-5mm.

In this embodiment, the mold is a mold with a cavity, and its shape is set according to actual needs, which can be spherical, cylindrical, square column, or irregular paraboloid, etc. At the same time, foamed aluminum alloy can be prepared as needed Other foamed aluminum alloy products with a sandwich structure and embedded parts. The foamed aluminum alloy products can have various shapes and sizes, and are used as fillers and structures for energy absorption and bearing, damping, vibration reduction, etc. parts and functions. The shape and profile of the foamed aluminum alloy filling part is mainly realized by changing the shape of the inner cavity of the mold, while the control of the porosity of the foamed aluminum alloy prepared by secondary foaming is mainly controlled by the quality of the prefabricated part, that is, by controlling The control of the quality of the primary foamed aluminum alloy prefabricated parts realizes the control of the average porosity of the foamed aluminum alloy special-shaped parts. The relationship between the quality of the prefabricated parts and the porosity of the foamed aluminum alloy prepared by secondary foaming is: ), where Prb is the average porosity of the foamed aluminum alloy prepared by secondary foaming, m is the quality of the primary foamed aluminum alloy preform, ρ is the density of the aluminum alloy, and V is the volume of the mold cavity. For example, the density of aluminum can be taken as 2,780 kilograms per cubic meter, the primary foamed aluminum alloy prefabricated part can be chosen as 68 grams, the volume of the inner cavity of the mold is 163,000 cubic millimeters, and the foamed aluminum alloy prepared by foaming fills the entire mold The cavity has an average porosity of 85%.

Embodiment 3 A method for preparing foamed aluminum alloy products through secondary foaming, comprising the following steps:

Step 1: Heat the aluminum alloy until it melts. Among them, aluminum alloys such as ZL101, ZL102, ZL111 series alloys, or cast aluminum-copper alloys, such as ZL201, ZL202, ZL205 series alloys, or mainly copper-containing or mainly Silicon-containing deformed aluminum alloy, adjust the temperature to 630°C-680°C, the temperature can be 635°C, 642°C, 650°C, 660°C, 665°C, 670°C, add 0.5%-5% of the weight of the aluminum alloy Calcium to the aluminum alloy melt, the addition of calcium can be selected as 0.8%, 1.2%, 1.5%, 2.0%, 2.8%, 3.5%, 4.2%, 4.7%, stirring for 1-30 minutes, the stirring time can be selected as 3 minutes, 8 minutes, 10 minutes, 15 minutes, 22 minutes, 25 minutes, the stirring speed can be 300-600rpm, and then add titanium hydride equivalent to 0.5%-5% of the weight of the aluminum alloy, the amount of titanium hydride can be selected 0.8%, 1.2%, 1.5%, 2.0%, 2.8%, 3.5%, 4.2%, 4.7%, stirring at a speed of 800-5000rpm for 60-1000 seconds, for example, the stirring speed can be selected as, 4500rpm, 4000rpm, 3200rpm , 2500rpm, 1000rpm, 900rpm, the stirring time can be selected as 70s, 90s, 150s, 250s, 400s, 550s, 600s, 800s, 900s, so that the titanium hydride is evenly distributed in the melt, and the melt is cooled after stirring to obtain porosity Primary foamed aluminum alloy prefabricated parts less than 70%, such as porosity 60%, 54%, 52%, 45%, 39%, 35%, 28%, 22%, 18%, 15%; this foamed aluminum Alloy prefabricated parts have larger wall thickness and better air tightness, which can effectively prevent gas from escaping during the secondary heating process.

Step 2: Put the primary foamed aluminum alloy prefabricated part with a porosity lower than 70% into the mold, and keep it warm at a temperature of 700°C to 1200°C for 3 to 40 minutes, wherein the temperature can be selected as 750°C, 800°C, 850°C, 880°C, 950°C, 1000°C, 1150°C, so that the primary foamed aluminum alloy preform is foamed in the mold for the second time, and the foamed aluminum alloy is cooled to obtain the foamed aluminum alloy product. The porosity range is 50%-90%, and the pore diameter is 1-5mm. Wherein, the mold is a mold with a cavity, and its shape is set according to actual needs, and can be spherical, cylindrical, square column, or irregular paraboloid.

In this embodiment, in order to obtain a foamed aluminum alloy profiled part with a skin, the hollow shape of the mold cavity of the profiled hollow mold can be any shape, including regular shapes and irregular shapes, and can be spherical, cylindrical, and square. Or irregular paraboloids, during implementation, the prefabricated parts can be pre-placed in the hollow part of the mold or part that needs to be filled with aluminum foam; the holding time can be 5 minutes, 7.5 minutes, 8.8 minutes, 11 minutes, 14 minutes, 16 minutes minutes, 19 minutes.

Embodiment 4 A method for preparing foamed aluminum alloy products through secondary foaming, comprising the following steps:

Step 1: Heat the aluminum alloy until it melts. Among them, aluminum alloys such as ZL101, ZL102, ZL111 series alloys, or cast aluminum-copper alloys, such as ZL201, ZL202, ZL205 series alloys, or mainly copper-containing or mainly For the deformed aluminum alloy containing silicon, adjust the temperature to 630°C-680°C, add calcium equivalent to 0.5%-5% of the weight of the aluminum alloy to the molten aluminum alloy, and the amount of calcium added can be selected as 0.8%, 1.2%, 1.5%, 2.0%, 2.8%, 3.5%, 4.2%, 4.7%, stirring for 1-30 minutes, the stirring time can be selected as 3 minutes, 8 minutes, 10 minutes, 15 minutes, 22 minutes, 25 minutes, the stirring speed can be 300-600rpm, and then add titanium hydride equivalent to 0.5%-5% of the weight of the aluminum alloy, the amount of titanium hydride can be selected as 0.8%, 1.2%, 1.5%, 2.0%, 2.8%, 3.5%, 4.2% , 4.7%, stirring at a speed of 800-5000rpm for 60-1000 seconds, for example, the stirring speed can be selected as 4500rpm, 4000rpm, 3200rpm, 2500rpm, 1000rpm, 900rpm, and the stirring time can be selected as 70s, 90s, 150s, 250s, 400s , 550s, 600s, 800s, 900s, so that titanium hydride is evenly distributed in the melt, and the stirred melt is cooled to obtain a primary foamed aluminum alloy preform with a porosity of less than 70%, for example, a porosity of 54%, 52 %, 45%, 39%, 35%, 28%, 22%, 18%, 15%;

Step 2: Put the primary foamed aluminum alloy prefabricated part with a porosity lower than 70% into the mold, and keep it warm at a temperature of 700°C to 1200°C for 3 to 40 minutes, wherein the temperature can be selected as 750°C, 800°C, 850°C, 880°C, 950°C, 1000°C, 1150°C, so that the primary foamed aluminum alloy preform is foamed in the mold for the second time, and the foamed aluminum alloy is cooled to obtain the foamed aluminum alloy product. The porosity range is 50%-90%, and the pore diameter is 1-5mm. Wherein, the mold is a mold with a cavity, and its shape is set according to actual needs, and can be spherical, cylindrical, square column, or irregular paraboloid.

In this embodiment, in the second step, the above-mentioned primary foamed aluminum alloy prefabricated part with a porosity lower than 70% is subjected to surface deoxidation treatment, and then the aluminum plate or aluminum alloy plate whose surface has been deoxidized is placed on the prefabricated part Then put it into the mold, if necessary, add inert gas such as argon, nitrogen or carbon dioxide to protect the preform in the mold to avoid further oxidation, so that the preform and skin are at a temperature of 700 ° C ~ 1200 ° C Keep warm for 3-40 minutes, so as to obtain foamed aluminum alloy products with thicker skins, such as sandwich structures with aluminum or aluminum alloys as panels, foamed aluminum alloys as sandwich cores, and thicker skins. For fillers with complex shapes, the foamed aluminum alloy used for the skin can be commonly used deformed aluminum alloys, such as hard aluminum alloys, super hard aluminum alloys, anti-rust aluminum alloys, etc., and the grades can be LY12, F5, etc.

The method of surface deoxidation treatment is as follows:

The surface treatment is similar to the method of deoxidizing the surface of aluminum alloy. Firstly, chemical degreasing is carried out: the process of chemical degreasing is to remove the oil stain on the surface of the workpiece through chemical reaction and physical and chemical action. Chemical degreasing is carried out in weak alkaline solution. Formula and process conditions of chemical degreasing liquid: 1. Formula: sodium hydroxide 30-50G/L, industrial detergent 0.5-1ML/L, water 70-125G; 2. Process conditions: temperature: 50-60°C, time : 1-2min; 3. Rinse with clean water after degreasing; 4. Chemical oxidation film removal: carry out pickling treatment to neutralize the residual lye on the surface of the workpiece, and remove its natural oxide film to expose the aluminum of the workpiece And the aluminum alloy substrate, for the production of silicon-containing aluminum alloy, it must be pickled with a mixed solution to remove the dark silicon floating ash on the surface; the formula of the pickling solution: concentrated nitric acid solution 200 ~ 270ML/L; temperature: room temperature time: 1-3min. The pickling solution formula for removing the oxide film and silicon floating ash on the surface of silicon-containing aluminum alloy parts: 3 volumes of concentrated nitric acid; 1 volume of concentrated hydrofluoric acid, temperature: room temperature, time: 5-15 minutes.

Embodiment 5 A method for preparing foamed aluminum alloy products through secondary foaming, comprising the following steps:

Step 1: Heat the aluminum alloy until it melts. Among them, aluminum alloys such as ZL101, ZL102, ZL111 series alloys, or cast aluminum-copper alloys, such as ZL201, ZL202, ZL205 series alloys, or mainly copper-containing or mainly Silicon-containing deformed aluminum alloy, adjust the temperature to 630°C-680°C, the temperature can be 635°C, 642°C, 650°C, 660°C, 665°C, 670°C, add 0.5%-5% of the weight of the aluminum alloy Calcium to the aluminum alloy melt, the addition of calcium can be selected as 0.8%, 1.2%, 1.5%, 2.0%, 2.8%, 3.5%, 4.2%, 4.7%, stirring for 1-30 minutes, the stirring time can be selected as 3 minutes, 8 minutes, 10 minutes, 15 minutes, 22 minutes, 25 minutes, the stirring speed can be 300-600rpm, and then add titanium hydride equivalent to 0.5%-5% of the weight of the aluminum alloy, the amount of titanium hydride can be selected 0.8%, 1.2%, 1.5%, 2.0%, 2.8%, 3.5%, 4.2%, 4.7%, stirring at a speed of 800-5000rpm for 60-1000 seconds, for example, the stirring speed can be selected as, 4500rpm, 4000rpm, 3200rpm , 2500rpm, 1000rpm, 900rpm, the stirring time can be selected as 70s, 90s, 150s, 250s, 400s, 550s, 600s, 800s, 900s, so that the titanium hydride is evenly distributed in the melt, and the stirred melt is cooled to obtain pores Primary foam aluminum alloy prefabricated parts with porosity lower than 70%, such as porosity 60%, 54%, 52%, 45%, 39%, 35%, 28%, 22%, 18%, 15%;

Step 2: Put the primary foamed aluminum alloy prefabricated part with a porosity lower than 70% into the mold, and keep it warm at a temperature of 700°C to 1200°C for 3 to 40 minutes, wherein the temperature can be selected as 750°C, 800°C, 850°C, 880°C, 950°C, 1000°C, 1150°C, so that the primary foamed aluminum alloy preform is foamed in the mold for the second time, and the foamed aluminum alloy is cooled to obtain the foamed aluminum alloy product. The porosity can be 50%, 60%, 70%, 80%, 85%, 90%. Wherein, the mold is a mold with a cavity, and its shape is set according to actual needs, and can be spherical, cylindrical, square column, or irregular paraboloid.

In this embodiment, in the second step, the above-mentioned primary foamed aluminum alloy with a porosity lower than 70% is placed in a mold with a spherical cavity, and kept at a temperature of 700° C. to 1200° C. for 3 to 40 minutes, so that The primary foamed aluminum alloy prefabricated part is secondary foamed in the mold, and the foamed aluminum alloy is cooled to obtain a spherical foamed aluminum alloy product. The foamed aluminum alloy ball has a skin, and for some irregular occasions that need to be filled with the foamed aluminum alloy, it can be filled with foamed aluminum alloy balls with smaller dimensions (such as 1cm-5cm), and the method is simpler.

Embodiment 6 A method for preparing foamed aluminum alloy products through secondary foaming, comprising the following steps:

Step 1: Heat the aluminum alloy until it melts. Among them, aluminum alloys such as ZL101, ZL102, ZL111 series alloys, or cast aluminum-copper alloys, such as ZL201, ZL202, ZL205 series alloys, or mainly copper-containing or mainly For the deformed aluminum alloy containing silicon, adjust the temperature to 630°C-680°C, add calcium equivalent to 0.5%-5% of the weight of the aluminum alloy to the molten aluminum alloy, and the amount of calcium added can be selected as 0.8%, 1.2%, 1.5%, 2.0%, 2.8%, 3.5%, 4.2%, 4.7%, stirring for 1-30 minutes, the stirring time can be selected as 3 minutes, 8 minutes, 10 minutes, 15 minutes, 22 minutes, 25 minutes, the stirring speed can be 300-600rpm, and then add titanium hydride equivalent to 0.5%-5% of the weight of the aluminum alloy, the amount of titanium hydride can be selected as 0.8%, 1.2%, 1.5%, 2.0%, 2.8%, 3.5%, 4.2% , 4.7%, stirring at a speed of 800-5000rpm for 60-1000 seconds, for example, the stirring speed can be selected as 4500rpm, 4000rpm, 3200rpm, 2500rpm, 1000rpm, 900rpm, and the stirring time can be selected as 70s, 90s, 150s, 250s, 400s , 550s, 600s, 800s, 900s, make titanium hydride evenly distributed in the melt, cool the stirred melt, and obtain a primary foamed aluminum alloy preform with a porosity lower than 70%, for example, a porosity of 60%, 54 %, 52%, 45%, 39%, 35%, 28%, 22%, 18%, 15%;

Step 2: Put the primary foamed aluminum alloy prefabricated part with a porosity lower than 70% into the mold, and keep it warm at a temperature of 700°C to 1200°C for 3 to 40 minutes, wherein the temperature can be selected as 750°C, 800°C, 850°C, 880°C, 950°C, 1000°C, 1150°C, so that the primary foamed aluminum alloy preform is foamed in the mold for the second time, and the foamed aluminum alloy is cooled to obtain the foamed aluminum alloy product. Wherein, the mold is a mold with a cavity, and its shape is set according to actual needs, and can be spherical, cylindrical, square column, or irregular paraboloid.

In this embodiment, after the first step, the embedded part is implanted into the above-mentioned primary foamed aluminum alloy prefabricated part with a porosity lower than 70%, and the prefabricated part is placed in the mold, at a temperature of 700°C to 1200°C The temperature is kept at a temperature of 3 to 40 minutes, so that the primary foamed aluminum alloy prefabricated part is foamed in the mold for the second time, and the foamed aluminum alloy is cooled to obtain a foamed aluminum alloy product with embedded parts. The embedded part can be an internal thread, a screw hole, etc., and the material is usually steel or copper, which has a higher melting point than aluminum.

Claims (6)

1. A method for preparing foamed aluminum alloy products by secondary foaming, is characterized in that it comprises the following steps: Step 1: Heat the aluminum alloy to melt, and adjust the temperature to 630°C-680°C, add calcium equivalent to 0.5%-5% of the weight of the aluminum alloy to the molten aluminum alloy, stir for 1-30 minutes, and then add Titanium hydride equivalent to 0.5%-5% of the weight of the aluminum alloy, stirring to distribute the titanium hydride evenly in the melt, cooling the stirred melt, and obtaining a primary foamed aluminum alloy preform with a porosity lower than 70%; Step 2: Put the above-mentioned primary foamed aluminum alloy prefabricated part with a porosity lower than 70% into the mold, and keep it warm at a temperature of 700°C to 1200°C for 3 to 40 minutes, so that the primary foamed aluminum alloy preformed Secondary foaming in the mould, cooling the foamed aluminum alloy to obtain a foamed aluminum alloy product. 2. The method for preparing foamed aluminum alloy products through secondary foaming according to claim 1, characterized in that the mold in the second step has a complex-shaped inner cavity. 3. The method for preparing foamed aluminum alloy products by secondary foaming according to claim 1, characterized in that, in the second step, the primary foamed aluminum alloy prefabricated parts with a porosity lower than 70% are deoxidized on the surface treatment, and then place the aluminum plate or aluminum alloy plate that has been deoxidized on the surface on the surface of the prefabricated part, and then put it into the mold to heat. 4. The method for preparing foamed aluminum alloy products through secondary foaming according to claim 3, characterized in that, during the heating process of the preform, the preform is protected with an inert gas. 5. The method for preparing foamed aluminum alloy products through secondary foaming according to claim 1, characterized in that the inner cavity of the mold in the second step is spherical. 6. The method for preparing foamed aluminum alloy products by secondary foaming according to claim 1, characterized in that, in the second step, the embedded part is implanted into the primary foamed aluminum alloy prefabricated with a porosity lower than 70%. , and place the prefabricated part with embedded parts in the mold to heat the secondary foam.

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