Preparation process of ultrahigh-strength high-thermal-conductivity semi-solid pressure casting aluminum alloy casting

Abstract

The invention belongs to the field of aluminum alloy castings, and particularly relates to a preparation process of an ultrahigh-strength high-thermal-conductivity semi-solid pressure casting aluminum alloy casting, which comprises the following steps of: smelting corresponding raw materials of Si, Mg, Fe and a part of Cu, Mn, Zn, Cr, Ti and Al to obtain a first aluminum alloy melt; the rest Cu and C are combined and added into the first aluminum alloy melt in the form of surface copper-plated graphene, and secondary smelting is carried out to obtain a second aluminum alloy melt; refining, deslagging and casting the second aluminum alloy melt to obtain a cast ingot; cutting the cast ingot into aluminum alloy blocks, heating the aluminum alloy blocks to 100-120 DEG C, pouring the aluminum alloy blocks into liquid nitrogen for freezing treatment, then re-melting the aluminum alloy blocks to 595-605 DEG C, and carrying out ultrasonic treatment to obtain semi-solid slurry; casting the semi-solid slurry into a casting through a semi-solid die-casting process, and carrying out solid solution and aging treatment on the casting. The aluminum alloy casting is small in hot crack tendency, high in mechanical strength and good in heat-conducting property.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum alloy casting, and particularly relates to a preparation process of an ultrahigh-strength high-thermal-conductivity semi-solid die-cast aluminum alloy casting. BACKGROUND

[0002] 6063 aluminum alloy is a medium-strength aluminum alloy widely used in various fields, and has good corrosion resistance, processability and weldability. For example, in the field of transportation, 6063 aluminum alloy is used to manufacture vehicle floor plates, wheel hubs, elevators and other components. Its good plasticity and processability make it an ideal choice for manufacturing complex structural parts. In the field of industrial equipment, 6063 aluminum alloy is widely used to manufacture various industrial frame structures, mechanical equipment parts, precision molds, etc. due to its good corrosion resistance and processability. In the field of aerospace, 6063 aluminum alloy is used to manufacture aircraft fuselages, wings and other components in the aviation field, which helps to reduce the weight of aircraft and improve fuel efficiency due to its lightweight and high-strength characteristics. In addition, its good corrosion resistance and weldability make it an indispensable material in the aviation industry. In the field of electronics and electrical appliances, 6063 aluminum alloy is used to manufacture the housings, heat sinks and electrical components of electronic devices, such as LED lamp housings, refrigerators and air conditioners, due to its good electrical conductivity.

[0003] However, the main shortcomings of 6063 aluminum alloy in semi-solid die casting are poor flowability, high risk of mold damage, insufficient mechanical properties, high tendency of hot cracking and high incidence of casting defects. These shortcomings limit its application in die casting process, and it is usually more suitable for forging or other processing methods.

[0004] Semi-solid die-cast aluminum alloy is an advanced manufacturing technology that combines traditional die casting process with the characteristics of semi-solid metal, and has significant performance advantages and application potential. This technology heats the aluminum alloy to a temperature range between the liquidus and solidus (usually 590-610℃), forming a mixture of liquid phase surrounding spherical solid phase, i.e. semi-solid slurry, and then using its unique rheological properties for die casting.

[0005] For 6063 aluminum alloy, a large number of experiments have found that the incidence of hot cracking is as high as 53% or more when using semi-solid die casting. Therefore, using semi-solid die casting to improve the mechanical properties of 6063 aluminum alloy while reducing the incidence of hot cracking is an urgent research topic.

[0006] Based on this, the present application is proposed. SUMMARY

[0007] The purpose of the present application is to provide a preparation process of an ultrahigh-strength high-thermal-conductivity semi-solid die-cast aluminum alloy casting to solve the above problems.

[0008] A preparation process of an ultra-high-strength high-thermal-conductivity semi-solid die-cast aluminum alloy casting, comprising the following steps:

[0009] Step 1, weighing aluminum alloy raw materials according to the following components in mass percentage:

[0010] Si: 0.20-0.60%;

[0011] Mg: 0.45-0.90%;

[0012] Fe: ≤0.35%;

[0013] Cu: ≤0.35%;

[0014] Mn: ≤0.10%;

[0015] Zn: ≤0.10%;

[0016] Cr: ≤0.10%;

[0017] Ti: ≤0.10%;

[0018] C: 0.12-0.15%;

[0019] the rest being Al and inevitable impurities;

[0020] Step 2, smelting Si, Mg, Fe, a part of Cu, Mn, Zn, Cr, Ti, Al corresponding raw materials to obtain a first aluminum alloy melt;

[0021] Step 3, adding the rest of Cu combined with C in the form of copper-plated graphene graphite into the first aluminum alloy melt, secondary smelting to obtain a second aluminum alloy melt;

[0022] Step 4, refining and deslagging the second aluminum alloy melt to obtain a casting ingot;

[0023] Step 5, cutting the casting ingot into aluminum alloy blocks, heating the aluminum alloy blocks to 100-120℃, pouring into liquid nitrogen for cold treatment, then remelting to 595-605℃, ultrasonic treatment to obtain a semi-solid slurry;

[0024] Step 6, die-casting the semi-solid slurry through a semi-solid die-casting process to obtain a casting, and then performing solid solution and aging treatment on the casting to obtain the ultra-high-strength high-thermal-conductivity semi-solid die-cast aluminum alloy casting.

[0025] Further improvement, the Si, Mg, Fe, a part of Cu, Mn, Zn, Cr, Ti, Al corresponding raw materials are single elements or compounds containing corresponding elements.

[0026] Further improvement, the surface copper-plated graphene is a conventional material, which can be plated with copper on the surface of graphene by solution reduction method, chemical copper plating method, electrochemical deposition method or thermal evaporation / magnetron sputtering method.

[0027] Further improvement, the mass ratio of copper to graphene in the surface copper-plated graphene is 2:1.

[0028] Further improvement, in step 3, the temperature of secondary smelting is 750-760℃.

[0029] Further improvement, in step 4, the refining is carried out by adding a refining agent and ultrasonic degassing.

[0030] Further improvement, in step 4, the pouring temperature is 740-750℃.

[0031] Further improvement, in step 5, the ultrasonic treatment is 20-30 min.

[0032] Further improvement, in step 6, in the semi-solid die casting process, the injection speed is 0.47-0.5 m / s, and the injection pressure is 120-130 MPa.

[0033] Further improvement, in step 5, pour into liquid nitrogen and freeze for 1-3 min.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] 1. By further optimizing and adjusting the formula of 6063 aluminum alloy, doping Cu and C, and adding copper-plated graphene to smelting, and improving the smelting process, pouring first, then liquid nitrogen quick freezing treatment, then re-melting to form a semi-solid die casting process, the defects of the existing 6063 aluminum alloy in the semi-solid die casting process can be solved, and the tendency of hot cracking is significantly improved.

[0036] 2. The ultra-high strength and high thermal conductivity semi-solid die casting aluminum alloy casting has high strength, good thermal conductivity, and an ultimate use temperature of up to 550℃, and good high temperature resistance. DETAILED DESCRIPTION

[0037] The present application will be further described in detail below through specific examples.

[0038] Example 1

[0039] 1. The aluminum alloy raw materials are weighed according to the following mass percentage composition:

[0040] Si: 0.20%;

[0041] Mg: 0.90%;

[0042] Fe: 0.3%;

[0043] Cu: 0.31%;

[0044] Mn: 0.05%;

[0045] Zn: 0.06%;

[0046] Cr: 0.08%;

[0047] Ti: 0.10%;

[0048] C: 0.12%;

[0049] the rest is Al and inevitable impurities.

[0050] 2, melt Si, Mg, Fe, part of Cu, Mn, Zn, Cr, Ti, Al corresponding raw materials to obtain a first aluminum alloy melt.

[0051] 3, the remaining Cu is combined with C to be added to the first aluminum alloy melt in the form of copper-plated graphene, and is subjected to secondary melting at a temperature of 750-760°C to obtain a second aluminum alloy melt; the mass ratio of copper to graphene in the copper-plated graphene is 2:1.

[0052] 4, the second aluminum alloy melt is refined and deslagged by adding a refining agent and ultrasonic degassing, and is cast at 740-750°C to obtain an ingot.

[0053] 5, the ingot is cut into aluminum alloy blocks, which are heated to 100-110°C, poured into liquid nitrogen for cold treatment for 1-3 min (preferably until the liquid nitrogen is completely volatilized), and then remelted to 595-605°C, and subjected to ultrasonic treatment for 30 min to obtain a semi-solid slurry.

[0054] 6, the semi-solid slurry is pressure cast into a casting by a semi-solid pressure casting process (the injection speed is 0.47-0.49 m / s, and the injection pressure is 120-125 MPa), and the casting is subjected to solid solution and aging treatment to obtain the ultra-high-strength high-thermal-conductivity semi-solid pressure-cast aluminum alloy casting.

[0055] Example 2

[0056] 1, aluminum alloy raw materials are weighed according to the following mass percentage composition:

[0057] Si: 0.60%;

[0058] Mg: 0.45%;

[0059] Fe: 0.35%;

[0060] Cu: 0.35%;

[0061] Mn: 0.08%;

[0062] Zn: 0.03%;

[0063] Cr: 0.07%;

[0064] Ti: 0.02%;

[0065] C: 0.15%;

[0066] the rest is Al and inevitable impurities.

[0067] 2, Si, Mg, Fe, part of Cu, Mn, Zn, Cr, Ti, Al corresponding raw materials are smelted to obtain a first aluminum alloy melt.

[0068] 3, the remaining Cu is combined with C to be added to the first aluminum alloy melt in the form of copper-plated graphene, and secondary smelting is carried out at a temperature of 750-760°C to obtain a second aluminum alloy melt; the mass ratio of copper to graphene in the copper-plated graphene is 2:1.

[0069] 4, the second aluminum alloy melt is refined and deslagged by adding a refining agent and ultrasonic degassing, and is cast at 740-750°C to obtain an ingot.

[0070] 5, the ingot is cut into aluminum alloy blocks, which are heated to 110-120°C, poured into liquid nitrogen and frozen for 1-3 min (preferably until the liquid nitrogen is completely volatilized), then remelted to 595-605°C, and ultrasonic treated for 20 min to obtain a semi-solid slurry.

[0071] 6, the semi-solid slurry is pressure cast by a semi-solid pressure casting process (injection speed is 0.48-0.5 m / s, injection pressure is 125-130 MPa) to obtain a casting, and the casting is subjected to solid solution and aging treatment to obtain the ultra-high-strength high-thermal-conductivity semi-solid pressure-cast aluminum alloy casting.

[0072] Example 3

[0073] 1, aluminum alloy raw materials are weighed according to the following mass percentage composition:

[0074] Si: 0.47%;

[0075] Mg: 0.65%;

[0076] Fe: 0.24%;

[0077] Cu: 0.31%;

[0078] Mn: 0.06%;

[0079] Zn: 0.05%;

[0080] Cr: 0.06%;

[0081] Ti: 0.07%;

[0082] C: 0.14%;

[0083] the rest is Al and inevitable impurities.

[0084] 2, Si, Mg, Fe, part of Cu, Mn, Zn, Cr, Ti, Al corresponding raw materials are smelted to obtain a first aluminum alloy melt.

[0085] 3, the remaining Cu is combined with C to be added to the first aluminum alloy melt in the form of copper-plated graphene, and secondary smelting is carried out at a temperature of 750-760°C to obtain a second aluminum alloy melt; the mass ratio of copper to graphene in the copper-plated graphene is 2:1.

[0086] 4, the second aluminum alloy melt is refined and deslagged by adding a refining agent and ultrasonic degassing, and is cast at 740-750°C to obtain an ingot.

[0087] 5, the ingot is cut into aluminum alloy blocks, which are heated to 100-120°C, poured into liquid nitrogen and frozen for 1-3 min (preferably until the liquid nitrogen is completely volatilized), then remelted to 595-605°C, and ultrasonic treated for 30 min to obtain a semi-solid slurry.

[0088] 6, the semi-solid slurry is pressure cast by a semi-solid pressure casting process (the injection speed is 0.48-0.5 m / s, and the injection pressure is 120-125 MPa) to obtain a casting, and the casting is subjected to solid solution and aging treatment to obtain the ultra-high-strength high-thermal-conductivity semi-solid pressure-cast aluminum alloy casting.

[0089] Comparative Example 1

[0090] 1, aluminum alloy raw materials are weighed according to the following mass percentage composition:

[0091] Si: 0.47%;

[0092] Mg: 0.65%;

[0093] Fe: 0.24%;

[0094] Cu: 0.05%;

[0095] Mn: 0.06%;

[0096] Zn: 0.05%;

[0097] Cr: 0.06%;

[0098] Ti: 0.07%;

[0099] the rest being Al and inevitable impurities.

[0100] 2. Melting the corresponding raw materials of Si, Mg, Fe, Cu, Mn, Zn, Cr, Ti, Al to obtain a first aluminum alloy melt.

[0101] 3. Refining and deslagging the first aluminum alloy melt by adding a refining agent and ultrasonic degassing, and pouring at 740-750°C to obtain an ingot.

[0102] 4. Cutting the ingot into aluminum alloy blocks, heating the aluminum alloy blocks to 100-120°C, pouring into liquid nitrogen for cold treatment for 1-3 min (preferably until the liquid nitrogen is completely volatilized), then remelting to 595-605°C, and ultrasonic treatment for 30 min to obtain a semi-solid slurry.

[0103] 5. Pressing the semi-solid slurry into a casting by a semi-solid die casting process (injection speed 0.48-0.5 m / s, injection pressure 120-125 MPa), and after solid solution and aging treatment of the casting, an aluminum alloy casting is obtained.

[0104] Comparative Example 2

[0105] 1. Weighing aluminum alloy raw materials according to the following mass percentage composition:

[0106] Si: 0.47%;

[0107] Mg: 0.65%;

[0108] Fe: 0.24%;

[0109] Cu: 0.31%;

[0110] Mn: 0.06%;

[0111] Zn: 0.05%;

[0112] Cr: 0.06%;

[0113] Ti: 0.07%;

[0114] C: 0.14%;

[0115] the rest being Al and inevitable impurities.

[0116] 2. Melting the corresponding raw materials of Si, Mg, Fe, Cu, Mn, Zn, Cr, Ti, Al, C to obtain a first aluminum alloy melt. That is, Cu and C are not added in the form of surface copper-plated graphene, but in the form of red copper and graphene.

[0117] 3. The first aluminum alloy melt is refined by adding a refining agent and ultrasonic degassing, and cast into an ingot at 740-750°C.

[0118] 4. The ingot is cut into aluminum alloy blocks, which are heated to 100-120°C, then poured into liquid nitrogen and frozen for 1-3 minutes, then remelted to 595-605°C, and ultrasonic treated for 30 minutes to obtain a semi-solid slurry.

[0119] 5. The semi-solid slurry is pressure cast into a casting by a semi-solid pressure casting process (injection speed 0.48-0.5 m / s, injection pressure 120-125 MPa), and the casting is subjected to solid solution and aging treatment to obtain the ultra-high strength and high thermal conductivity semi-solid pressure cast aluminum alloy casting.

[0120] Comparative Example 3

[0121] In this example, the first aluminum alloy melt is refined by adding a refining agent and ultrasonic degassing, and cooled to 595-605°C, and ultrasonic treated for 30 minutes to obtain a semi-solid slurry. The semi-solid slurry is pressure cast into a casting by a semi-solid pressure casting process (injection speed 0.48-0.5 m / s, injection pressure 120-125 MPa), and the casting is subjected to solid solution and aging treatment to obtain an aluminum alloy casting.

[0122] Comparative Example 4

[0123] In this example, the liquid carbon dioxide is poured and frozen for 1-3 minutes, and the rest is the same.

[0124] The performance of the aluminum alloy castings of Examples 1-3 and Comparative Examples 1-5 is shown in Table 1:

[0125] Table 1

[0126] Tensile strength (MPa) Thermal conductivity (W / m °C) Thermal cracking occurrence rate (%) Example 1 295 181 8.7 Example 2 298 182 9.2 Example 3 317 185 8.1 Comparative Example 1 196 165 41.3 Comparative Example 2 159 / 91.5 Comparative Example 3 214 178 50.6 Comparative Example 4 250 176 33.3

[0127] As shown in Comparative Example 1, for a conventional 6063 aluminum alloy, even after liquid nitrogen treatment after initial casting, the aluminum alloy casting made by a semi-solid pressure casting process has even slightly lower strength than a currently cast 6063 aluminum alloy.

[0128] As shown in Comparative Example 2, for Cu and C, if they are not added in the form of copper-plated graphene but in the form of simple substances, the "lubricating" effect of copper-plated graphene between aluminum alloy grains cannot be achieved, and finer grains cannot be formed, thereby limiting the improvement of the strength and thermal conductivity of the aluminum alloy and increasing the tendency of thermal cracking. The reason is that the addition of C simple substances (such as graphite) can seriously affect the structure between aluminum alloy grains.

[0129] From Comparative Example 3, if the internal structure of the crystallized aluminum alloy is not destroyed by liquid nitrogen before semi-solid die casting, the subsequent semi-solid die casting will still be affected when the semi-solid slurry is heated.

[0130] From Comparative Example 4, if the degree of quick freezing is not enough (such as using liquid carbon dioxide for quick freezing) before semi-solid die casting, the degree of destruction of the internal structure of the crystallized aluminum alloy is low, and the subsequent semi-solid die casting will still be affected when the semi-solid slurry is heated.

[0131] From the above, in the smelting process of the aluminum alloy, Cu and C must be added in the form of copper-plated graphene, and at the same time, the aluminum alloy must be cast first, then liquid nitrogen quick frozen, and then remelted to produce a die casting by the semi-solid die casting process. Finally, the defect that the hot cracking tendency of the existing 6063 aluminum alloy is significantly increased during the semi-solid die casting process can be solved.

[0132] Example 4

[0133] For the mass ratio of copper to graphene in the copper-plated graphene being 1:1, 1.5:1, 2:1, and 3:1, the corresponding failure high temperature value (the lowest temperature corresponding to a decrease in tensile strength of the aluminum alloy in a high temperature environment by more than 50%) is shown in Table 2:

[0134] Table 2

[0135]

[0136]

[0137] From Table 2, when the mass ratio of copper to graphene in the copper-plated graphene is 2:1, the corresponding failure high temperature value is the largest, indicating that the ultimate use temperature of the ultra-high strength and high thermal conductivity semi-solid die casting aluminum alloy casting according to the present application can be as high as 550℃, and at this temperature, the aluminum alloy will not lose strength.

[0138] The above is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for preparing ultra-high strength and high thermal conductivity semi-solid die-cast aluminum alloy castings, characterized by: The following steps are involved: Step 1: Weigh the aluminum alloy raw materials according to the following mass percentage composition: Si: 0.20~0.60%; Mg: 0.45~0.90%; Fe: ≤0.35%; Cu: ≤0.35%; Mn: ≤0.10%; Zn: ≤0.10%; Cr：≤0.10％； Ti: ≤0.10%; C：0.12～0.15％； The rest is Al and unavoidable impurities; Step 2: Smelting corresponding raw materials of Si, Mg, Fe, a portion of Cu, Mn, Zn, Cr, Ti, and Al to obtain a first aluminum alloy melt; Step 3: The remaining Cu is combined with C to form copper-coated graphene, which is then added to the first aluminum alloy melt, and then smelted for the second time to obtain a second aluminum alloy melt; Step 4: refining and deslagging the second aluminum alloy melt, and casting to obtain an ingot; Step 5: cutting the ingot into aluminum alloy blocks, heating the aluminum alloy blocks to 100-120° C., freezing them in liquid nitrogen, and then remelting them to 595-605° C. and ultrasonically treating them to obtain a semi-solid slurry; Step 6: Die-cast the semi-solid slurry into a casting through a semi-solid die-casting process, and perform solid solution and aging treatment on the casting to obtain the ultra-high strength and high thermal conductivity semi-solid die-cast aluminum alloy casting.

2. The process for preparing an ultra-high-strength and high-thermal-conductivity semi-solid die-cast aluminum alloy casting according to claim 1, characterized in that: The raw materials corresponding to Si, Mg, Fe, a part of Cu, Mn, Zn, Cr, Ti, and Al are simple substances of the corresponding elements or compounds containing the corresponding elements.

3. The process for preparing an ultra-high-strength and high-thermal-conductivity semi-solid die-cast aluminum alloy casting according to claim 1, characterized in that: The surface copper-plated graphene is prepared by copper plating on the graphene surface using a solution reduction method, a chemical copper plating method, an electrochemical deposition method or a thermal evaporation / magnetron sputtering method.

4. The process for preparing an ultra-high-strength and high-thermal-conductivity semi-solid die-cast aluminum alloy casting according to claim 3, characterized in that: The mass ratio of copper to graphene in the surface copper-plated graphene is 2:

1.

5. The process for preparing an ultra-high strength and high thermal conductivity semi-solid die-cast aluminum alloy casting according to claim 1, characterized in that: In step 3, the temperature of the secondary smelting is 750-760°C.

6. The process for preparing an ultra-high strength and high thermal conductivity semi-solid die-cast aluminum alloy casting according to claim 1, characterized in that: In step 4, refining is performed by adding a refining agent and combining ultrasonic degassing.

7. The process for preparing an ultra-high strength and high thermal conductivity semi-solid die-cast aluminum alloy casting according to claim 1, characterized in that: In step 4, the casting temperature is 740-750°C.

8. The process for preparing an ultra-high strength and high thermal conductivity semi-solid die-cast aluminum alloy casting according to claim 1, characterized in that: In step 5, ultrasonic treatment is performed for 20 to 30 minutes.

9. The process for preparing an ultra-high strength and high thermal conductivity semi-solid die-cast aluminum alloy casting according to claim 1, characterized in that: In step 6, in the semi-solid die-casting process, the injection speed is 0.47-0.5 m / s, and the injection pressure is 120-130 MPa.

10. The process for preparing an ultra-high strength and high thermal conductivity semi-solid die-cast aluminum alloy casting according to claim 1, characterized in that: In step 5, pour in liquid nitrogen and freeze for 1 to 3 minutes.

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