CN115846612A - Vacuum high-pressure die-casting forming method and product of light high-strength and high-toughness aluminum lithium alloy casting - Google Patents
Vacuum high-pressure die-casting forming method and product of light high-strength and high-toughness aluminum lithium alloy casting Download PDFInfo
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Abstract
The invention belongs to the field of metal casting, and discloses a vacuum die-casting forming method and a product of a light high-strength and high-toughness aluminum lithium alloy casting, which comprises the following steps: s1, preparing raw materials according to components of an aluminum lithium alloy casting, wherein the raw materials at least comprise an aluminum raw material and a lithium raw material; s2, carrying out low vacuum melting on the aluminum raw material, adding other raw materials except the lithium raw material after the aluminum raw material is completely melted, and refining by adopting a rotary inert gas blowing mode; s3, adjusting the temperature of the melt to 660-680 ℃, adding a lithium raw material, then adding a covering agent on the surface layer of the melt, and heating the alloy melt to 710-730 ℃ for smelting to obtain an aluminum-lithium alloy melt; and S4, carrying out ultrasonic refining treatment on the aluminum lithium alloy melt, and carrying out vacuum high-pressure die-casting forming on the aluminum lithium alloy melt after the refining treatment to obtain the required light high-strength and high-toughness aluminum lithium alloy casting. The invention can greatly improve the obdurability of the cast aluminum lithium alloy and effectively expand the application range of the cast aluminum lithium alloy.
Description
Technical Field
The invention belongs to the field of metal casting, and particularly relates to a vacuum high-pressure die-casting forming method and a product of a light high-strength and high-toughness aluminum lithium alloy casting.
Background
The aluminum lithium alloy is known as an ideal structural material for aerospace of the new generation, and the density of the aluminum alloy can be reduced by 3% and the elastic modulus can be improved by 6% when 1% of Li is added. The current research on aluminum lithium alloys is mainly limited to wrought aluminum lithium alloys, while relatively little research has been done on casting aluminum lithium alloys. The aluminum lithium alloy casting does not have the anisotropy problem easily generated by a plastic rolled piece, and the Li content can be higher, so the alloy has lower density and higher modulus. Meanwhile, the cast aluminum-lithium alloy also has good casting performance, particularly the copying capability of the alloy to cavity fine structures is generally better than that of the traditional aluminum alloy, and the alloy is easy to form large-scale complex parts such as torpedo shells, airplane external storage tanks and the like at one time and has wide application prospect.
Different from other aluminum alloys, because Li has high chemical activity and large density difference with other alloy elements, the aluminum-lithium alloy is easy to oxidize and absorb hydrogen in the casting process, so that casting defects such as air holes, shrinkage porosity, component segregation and the like are easy to occur in an alloy solidification structure. The melting of the aluminum lithium alloy mainly comprises a flux protection method, an inert gas protection method and a vacuum melting method. The existing cast aluminum lithium alloy is mostly smelted by adopting a flux and inert gas protection method, and a casting or a material is obtained by preparing and forming through a gravity casting method. Although the problems of hydrogen absorption and oxidation in the preparation process of the cast aluminum-lithium alloy can be better solved by adopting a mode of 'full vacuum melting and gravity casting', the method has low operability (such as incapability of slagging-off, degassing refining and the like), high cost and limited casting size, and more importantly, the casting defects of shrinkage porosity, shrinkage cavity, component segregation, coarse grains and the like can not be avoided. Because of the 'genetic effect', the solidification structure characteristics of the cast aluminum lithium alloy directly influence the toughness of the casting and the quality of the subsequent heat treatment product. For example, yang Kai et Al (Yang Kai. Study of cast Al-Li alloy structure and mechanical properties [ D ]. University of harabin industry, 2017) at harabin university of industry prepared 6 cast Al-Li-Cu- (Mg) -Zr alloys by melting with high purity argon protection, the elongation of the alloys was generally low (< 0.4%), and the tensile strength was 394MPa at the highest. Patent CN201610200924.5 discloses a low-density and high-rigidity cast aluminum-lithium alloy and a preparation method thereof, and through adding alloy elements (Li, cu, mg, ag, zr and Mn) and optimizing relevant heat treatment process conditions, the optimal tensile strength of the alloy can reach 408MPa, but the elongation of the alloy is only 2.9%.
It can be seen that poor toughness is an important bottleneck limiting the application of cast aluminum lithium alloys, and in particular, poor plasticity (elongation is often less than 4%). Therefore, the development of a preparation and forming method of a light-weight high-toughness cast aluminum lithium alloy material suitable for aerospace manufacturing is urgently needed in the field.
Disclosure of Invention
Aiming at the defects or improvement requirements in the prior art, the invention provides a vacuum high-pressure die-casting forming method for a light high-strength and high-toughness aluminum lithium alloy casting, which can realize the effective preparation of the light high-strength and high-toughness cast aluminum lithium alloy through the design of a preparation process and a corresponding process, greatly improve the strength and toughness of the cast aluminum lithium alloy, effectively expand the application range of the cast aluminum lithium alloy, and is particularly suitable for aerospace manufacturing.
In order to achieve the above object, according to one aspect of the present invention, a vacuum high-pressure die-casting forming method for a light high-strength and high-toughness aluminum lithium alloy casting is provided, which comprises the following steps:
s1, preparing raw materials according to components of an aluminum lithium alloy casting, wherein the raw materials at least comprise an aluminum raw material and a lithium raw material;
s2, carrying out low vacuum melting on the aluminum raw material, adding other raw materials except the lithium raw material after the aluminum raw material is completely melted, adjusting the temperature of the melt to 720-740 ℃, and refining the alloy melt by blowing inert gas in a rotating mode to obtain a high-quality lithium-free alloy melt;
s3, adjusting the temperature of the melt to 660-680 ℃, adding a lithium raw material into the lithium-free alloy melt, then adding a covering agent into the surface layer of the melt, and heating the alloy melt to 710-730 ℃ for smelting to obtain an aluminum-lithium alloy melt;
and S4, carrying out ultrasonic refining treatment on the aluminum lithium alloy melt, and carrying out vacuum die-casting forming on the aluminum lithium alloy melt after the refining treatment to obtain the required light high-strength and high-toughness aluminum lithium alloy casting.
More preferably, in step S2, the melting temperature of the aluminum raw material is 740 to 760 ℃; the refining treatment time is 3 min-5 min.
More preferably, in step S3, when the lithium raw material is added, the lithium raw material wrapped with aluminum foil is added to the lithium-free alloy melt by using a bell jar, and a protective gas is introduced to protect the lithium raw material.
More preferably, the steps S2 and S3 are carried out in a vacuum melting furnace to realize low vacuum melting, and the vacuum degree in the vacuum melting furnace is 50 kPa-60 kPa when the step S2 is carried out; and (4) when the step (S3) is executed, the vacuum degree in the vacuum melting furnace is 80 kPa-100 kPa.
More preferably, in step S4, the ultrasonic refining treatment specifically includes: preheating an ultrasonic amplitude transformer to 200-300 ℃, and then inserting the preheated amplitude transformer into the melt to carry out ultrasonic vibration by 10-15 mm below the liquid level; the ultrasonic vibration temperature is 660-680 ℃, the ultrasonic vibration time is 1-3 min, the ultrasonic power is 1.5-2.8 kW, and protective gas is introduced for protection during ultrasonic vibration.
More preferably, in step S4, the vacuum high-pressure die-casting is specifically: preheating a die in a die casting machine, and pumping out air in a die cavity of the die to form a preset vacuum degree; and (5) pouring the aluminum lithium alloy melt subjected to the ultrasonic refining treatment in the step (S4) into a pressure chamber of a die casting machine, and pressing the aluminum lithium alloy melt into a die cavity of a die to obtain the light high-strength high-toughness aluminum lithium alloy casting.
More preferably, the conditions for the vacuum high-pressure die-casting are as follows: the preheating temperature of the die is 200-250 ℃, the pouring temperature of the aluminum lithium alloy melt is 650-670 ℃, the injection pressure of the die casting machine is 80-120 MPa, the injection speed is 3-5 m/s, and the vacuum degree in the die cavity is 80-100 kPa.
According to another aspect of the invention, a light-weight high-strength and high-toughness aluminum lithium alloy casting prepared by the method is provided.
Preferably, the cast tensile strength of the light high-strength and high-toughness aluminum lithium alloy casting reaches 300MPa to 320MPa, and the elongation reaches 10 percent to 18.5 percent.
More preferably, the light high-strength and high-toughness aluminum-lithium alloy casting is an aluminum-lithium-copper-magnesium alloy casting containing 2% -3% of Li.
Generally, compared with the prior art, the technical scheme conceived by the invention mainly has the following technical advantages:
1. the invention makes the aluminum lithium alloy have high strength and toughness, keep better fluidity and do not stick to a die by melt processing and vacuum high-pressure die-casting forming methods of the aluminum lithium alloy, and is suitable for vacuum high-pressure die-casting, the cast tensile strength of the die-casting aluminum lithium alloy can reach 300MPa-320MPa, and the elongation can reach 10% -18.5%.
2. The invention combines 'low vacuum melting' with 'rotary degassing refining', not only overcomes the defect that the degassing and deslagging can not be carried out in the existing high vacuum melting process, but also solves the problems of poor degassing effect, long degassing time (about 15min is needed) and serious oxidation burning loss of the aluminum-lithium alloy liquid in the 'rotary degassing refining' under the non-vacuum condition; meanwhile, under the conditions of 'low vacuum melting' + 'rotary degassing refining', the degassing time can be shortened (within 3-5 min), and the efficiency is greatly improved.
3. In the alloy smelting process, a novel double-stage refining method of 'rotary blowing refining of Li-free alloy melt' + 'high-efficiency ultrasonic treatment refining of Li-containing alloy melt' is innovatively provided by adjusting and optimizing the adding sequence of alloy raw materials and a corresponding smelting process, so that the high-quality cast aluminum-lithium alloy melt is obtained. The method not only solves the problems of unsatisfactory degassing and refining effects, long degassing time or incapability of refining by adopting rotary blowing in the process of preparing the cast aluminum-lithium alloy melt by the traditional flux protection method and the inert gas protection method, but also can promote solute atoms in the melt to be uniformly dispersed and structure to be refined while ultrasonically degassing and deslagging, and particularly has short ultrasonic refining time and high efficiency. In addition, compared with a high vacuum melting method, the method has the advantages of simple required equipment, strong operability and lower production cost, and particularly, the method can be perfectly combined with subsequent large-scale melting refining and preparation forming processes such as a vacuum die casting method, so that the product quality and the production efficiency are greatly improved.
4. The invention provides a preparation and forming method of a cast aluminum-lithium alloy, and provides a new forming technology combining a low vacuum melting method, a rotary blowing refining and ultrasonic refining and vacuum high-pressure die casting for the first time. And filling the cavity with the ultrasonic aluminum-lithium alloy melt at an injection speed of 3-5 m/s by controlling the vacuum degree of the cavity to be above 80kPa, and quickly solidifying and forming under the high pressure of 80-120 MPa to obtain a high-quality cast aluminum-lithium alloy casting. The new technology has simple preparation process and convenient operation. Compared with the existing gravity casting method or the existing vacuum die-casting method with lower pressure of 40 MPa-60 MPa for preparing the aluminum lithium alloy, the novel technology can greatly reduce the defects of air holes, shrinkage porosity and the like in the aluminum lithium alloy casting, and the high pressure and quick cooling conditions generated by vacuum high-pressure die-casting can bring the effect (such as greatly refining the size of alloy grains and reducing segregation) which cannot be obtained by the gravity casting method or the common vacuum die-casting method, thereby improving the performance of casting the aluminum lithium alloy.
5. The ultrasonic treatment of the melt and the high-pressure forming of the casting can change a temperature field and a concentration field in the melt, accelerate the cooling speed of the front edge of a solidification interface, increase the dissolving amount of alloy elements in an alpha (Al) matrix, and ensure that the high-pressure die-casting aluminum-lithium alloy forms supersaturated solid solution to promote the precipitation of a strengthening phase in the subsequent heat treatment process, thereby further improving the heat treatment state performance of the alloy. In addition, the problem that the toughness of the alloy is low due to the fact that the content of strengthened trace elements such as Sc and Zr is limited (often less than 0.2%) in the existing cast aluminum-lithium alloy can be solved, the preparation method of the cast aluminum-lithium alloy can increase the content of Sc and Zr to a certain extent, improve the casting process performance of the cast aluminum-lithium alloy and refine the alloy structure, and is beneficial to improving the toughness of a die-cast aluminum-lithium alloy casting.
Drawings
FIG. 1 is a flow chart of a vacuum high-pressure die-casting forming method of a light high-strength and high-toughness aluminum lithium alloy casting provided by an embodiment of the invention;
FIG. 2 is a flow chart of vacuum high-pressure die-casting of an aluminum lithium alloy casting according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a vacuum well type smelting furnace provided by the embodiment of the invention;
FIG. 4 is a schematic structural diagram of an ultrasonic refining furnace provided by an embodiment of the invention;
fig. 5 is a schematic structural diagram of a vacuum high-pressure die casting apparatus according to an embodiment of the present invention;
FIG. 6 is OM (optical metallography) and SEM (scanning Electron microscope) images of Al-2Li-2Cu-0.5Mg-0.2Zr-0.15Ag high pressure die-cast aluminum lithium alloy prepared in inventive example 1.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
1-lithium-free alloy melt, 2-heating rod, 3-crucible, 4-sealing ring, 5-vent, 6-valve, 7-vacuum channel, 8-cooling water inlet and outlet, 9-protective gas channel, 10-vacuum furnace, 11-heat preserving furnace, 12-cover plate, 13-ultrasonic amplitude transformer, 14-gas pipe, 15-ladle, 16-aluminum lithium alloy melt, 17-injection punch, 18-injection chamber, 19-die casting die, 20-vacuum valve and 21-die cavity.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
As shown in fig. 1 and fig. 2, the vacuum high-pressure die-casting forming method for a light high-strength and high-toughness aluminum lithium alloy casting provided by the embodiment of the invention specifically comprises the following steps:
s1, preparing raw materials according to components of an aluminum lithium alloy casting, wherein the raw materials at least comprise an aluminum raw material and a lithium raw material;
s2, carrying out low vacuum melting on the aluminum raw material, adding other raw materials except the lithium raw material after the aluminum raw material is completely melted, adjusting the temperature of the melt to 720-740 ℃, and refining the alloy melt by blowing inert gas in a rotating mode to obtain a high-quality lithium-free alloy melt;
s3, adjusting the temperature of the melt to 660-680 ℃, adding a lithium raw material into the lithium-free alloy melt, then adding a covering agent into the surface layer of the melt, and heating the alloy melt to 710-730 ℃ for smelting to obtain an aluminum-lithium alloy melt;
and S4, carrying out ultrasonic refining treatment on the aluminum lithium alloy melt, and carrying out vacuum high-pressure die-casting forming on the aluminum lithium alloy melt after the refining treatment to obtain the required light high-strength and high-toughness aluminum lithium alloy casting.
For the raw material, the present invention is preferably directed to an aluminum-lithium-copper-magnesium alloy with a higher lithium content containing 2% to 3% of Li, or an aluminum-lithium-copper-magnesium alloy containing a small amount of scandium or silver. The raw materials may be pure aluminum, pure lithium, pure copper, pure magnesium, pure silver, pure zinc and Al-10% for compounding Mn, al-2% Sc, al-10% Zr master alloy, etc.
Specifically, step S2 and step S3 are performed in a vacuum melting furnace, step S2+ step S3 are the melting process of the alloy melt in the method of the present invention, and the melting of the alloy melt of the present invention (including high-quality lithium-free alloy melt melting and aluminum lithium alloy melt melting) is low vacuum melting. Further, when melting the lithium-free alloy melt (i.e. when performing step S2), the vacuum degree in the vacuum melting furnace is 50kPa to 60kPa; when the aluminum lithium alloy melt is smelted (namely, when the step S3 is executed), the vacuum degree in the vacuum smelting furnace is 80 kPa-100 kPa, low-vacuum smelting is realized, and a proper amount of protective gas (such as high-purity argon) is introduced into the vacuum smelting furnace for protection. Under the vacuum degree, the hydrogen absorption and oxidation of the alloy melt can be effectively reduced, excessive volatilization of magnesium and lithium elements caused by overhigh vacuum degree can be avoided, and energy consumption required by high vacuum can be saved.
Further, the vacuum melting furnace is specifically a vacuum well type melting furnace, as shown in fig. 3, the vacuum well type melting furnace comprises a vacuum furnace 10, the ultimate vacuum degree in the vacuum furnace 10 can approach 100kPa, a heating rod 2 is arranged in the vacuum furnace 10, a furnace cover is arranged above the vacuum furnace 10, a sealing ring 4 is arranged between the furnace cover and the vacuum furnace 10, a vacuumizing structure is inserted on the furnace cover and comprises a vacuumizing channel 7 and an air release port 5, valves 6 are arranged on the vacuumizing channel 7 and the air release port 5, a cooling water inlet and outlet 8 is further arranged on the furnace cover, a protective gas channel 9 is further arranged on the vacuum furnace 10 and used for introducing protective gas into the vacuum furnace 10, a crucible 3 is placed in the vacuum furnace 10, and the crucible 3 is used for containing a lithium-free alloy melt 1. Specifically, the crucible adopts a graphite material crucible or a silicon carbide material crucible or a mixed material crucible which is not iron. In the step S2, the inert gas can be argon, nitrogen, helium and the like during refining treatment, the refining treatment time is 3-5 min, and the gas content in the aluminum melt can be obviously reduced under the treatment time and the slag removal effect is achieved. In the step S2, the smelting temperature of the aluminum raw material is 740-760 ℃, and at the temperature, the aluminum raw material can be fully molten, and the phenomena of hydrogen absorption, oxidation, nitridation burning loss and the like of the aluminum liquid can be avoided.
More specifically, in step S3, a commercially available covering agent dedicated to aluminum lithium alloy may be used as the covering agent, and for example, a mixed flux of LiCl and LiF may be used. When adding lithium raw material, adding the lithium raw material wrapped by aluminum foil into the lithium-free alloy melt by using a bell jar, and introducing protective gas (such as high-purity argon) for protection. By adding the lithium raw material in the manner, the lithium raw material can be better melted in the alloy melt, and the burning loss of lithium can be effectively reduced.
Furthermore, in step S4, the aluminum-lithium alloy melt is refined by adopting an ultrasonic vibration technology, and the uniform dispersion and the tissue refinement of solute atoms are promoted while the gas and the slag are removed. The ultrasonic refining treatment is carried out in an ultrasonic refining furnace. As shown in fig. 4, the ultrasonic refining furnace comprises a holding furnace 11 and a cover plate 12 arranged above the holding furnace 11, a casting ladle 15 is arranged in the holding furnace 11, the casting ladle 15 is used for containing an aluminum lithium alloy melt 16, an ultrasonic amplitude transformer 13 is inserted on the cover plate 12, the lower end of the ultrasonic amplitude transformer 13 is immersed in the aluminum lithium alloy melt 16, and an air pipe 14 is inserted on the cover plate 12 and used for introducing shielding gas into the holding furnace 11.
Preferably, the aluminum lithium alloy melt is transferred to an ultrasonic refining furnace for ultrasonic refining treatment after being smelted. The ultrasonic refining treatment process specifically comprises the following steps: preheating an ultrasonic amplitude transformer to 200-300 ℃, and then inserting the preheated amplitude transformer into the melt to carry out ultrasonic vibration by 10-15 mm below the liquid level; the ultrasonic vibration temperature (namely the temperature of the melt during ultrasonic vibration) is 660-680 ℃, the ultrasonic vibration time is 1-3 min, the ultrasonic power is 1.5-2.8 kW, and protective gas (such as inert gas) is introduced for protection during ultrasonic vibration.
Specifically, the vacuum high-pressure die-casting is performed in a vacuum high-pressure die-casting device, as shown in fig. 5, the vacuum high-pressure die-casting device includes a die-casting mold 19, a mold cavity 21 is formed in the die-casting mold 19, the mold cavity 21 is connected to a vacuum valve 20, the mold cavity 21 is further communicated with the injection chamber 18, and the injection punch 17 is disposed in the injection chamber 18.
Preferably, the vacuum high-pressure die-casting in step S4 specifically includes: preheating a die in a die casting machine, and pumping out air in a die cavity of the die to form a preset vacuum degree; and pouring the aluminum lithium alloy melt subjected to ultrasonic refining into a pressure chamber of a die casting machine, and pressing the aluminum lithium alloy melt into a die cavity under high pressure to obtain the light high-strength and high-toughness aluminum lithium alloy casting.
Specifically, the conditions for vacuum high-pressure die-casting are as follows: the preheating temperature of the die is 200-250 ℃, the pouring temperature of the aluminum lithium alloy melt is 650-670 ℃, the injection pressure of the die casting machine is 80-120 MPa, the injection speed is 3-5 m/s, and the vacuum degree in the die cavity is 80-100 kPa. Under the conditions, the aluminum lithium alloy melt can be smoothly filled, and the defects of air suction, oxidation, slag inclusion and the like of the aluminum lithium alloy can be effectively improved.
The invention utilizes the vacuum high-pressure die casting to cast the aluminum lithium alloy, which not only can greatly reduce the defects of air holes, shrinkage porosity and the like in the aluminum lithium alloy die casting piece, but also can greatly refine the size of alloy crystal grains under the high-pressure and quick-cooling conditions brought by the die casting, thereby improving the performance of casting the aluminum lithium alloy. The method can be used for preparing the light high-strength and high-toughness aluminum lithium alloy die casting, and the Li element is the metal element with the minimum density, so that the aluminum lithium alloy die casting prepared by the method is the alloy casting with the lightest mass, and has the characteristic of light weight, the cast tensile strength of the die casting can reach 300-320 MPa, and the elongation can reach 10-18.5%.
The following are examples of the present invention.
Example 1
The die-casting aluminum-lithium alloy of the embodiment comprises the following alloy components in percentage by mass: 2% Li, 2% Cu, 0.5% Mg, 0.5% Mn, 0.3% Zn, 0.2% Zr, 0.15% Ag, impurity ≦ 0.20%, balance Al. The preparation method for preparing the die-casting aluminum lithium alloy comprises the following steps:
s101: according to the designed alloy component proportion, weighing pure aluminum, pure lithium, pure copper, pure magnesium, pure zinc, pure silver and Al-10% Mn, al-10% Zr intermediate alloy as raw materials;
s102: putting pure aluminum into a self-made vacuum well type smelting furnace for smelting, wherein the smelting temperature is 750 ℃, and the vacuum degree in the furnace is 50kPa; after it is completely melted, adding pure copper, pure magnesium, pure silver, and Al-10% of Mn, al-10% of Zr intermediate alloy, except for pure Li, for melting; then, adjusting the temperature of the melt to 720 ℃, and refining the alloy melt for 5min by adopting a rotary argon blowing mode to obtain a high-quality Li-free alloy melt;
s103: adjusting the temperature of the Li-free alloy melt to 660 ℃, opening a furnace cover, adding pure Li particles wrapped by aluminum foil into the Li-free alloy melt by using a bell jar, adding a covering agent special for a commercially available aluminum-lithium alloy on the surface layer of the melt, heating the melt to 730 ℃ in a vacuum furnace under the protection of high-purity argon, wherein the vacuum degree in the vacuum furnace is 100kPa, so as to obtain the final aluminum-lithium alloy melt;
s104: inserting an ultrasonic amplitude transformer subjected to preheating treatment at 250 ℃ into 15mm below the liquid level of the aluminum-lithium alloy melt for ultrasonic refining treatment, wherein the ultrasonic treatment time is 2min, the ultrasonic power is 2.0kW, and the ultrasonic temperature is 670 ℃;
and S105, before the molten metal enters a die cavity of the die-casting die, pumping out air in the die cavity, enabling the vacuum degree to reach more than 80kPa, pouring the aluminum-lithium alloy melt with the temperature of 660 ℃ after ultrasonic treatment into a die with the preheating temperature of 250 ℃, filling the die cavity at the injection speed of 3m/S, and carrying out vacuum high-pressure die-casting under the pressure of 80MPa to obtain the casting.
The OM and SEM images of the die-casting aluminum-lithium alloy prepared in this example are shown in fig. 6, and it can be seen from fig. 6 that α -Al crystal grains of the die-casting aluminum-lithium alloy prepared in the present invention are fine, and the second phase is uniformly distributed, and the structure has no defects such as component segregation, oxidation slag inclusion, shrinkage porosity, and the like.
Example 2
The die-casting aluminum-lithium alloy of the embodiment comprises the following alloy components in percentage by mass: 3% Li, 2% Cu, 0.5% Mg, 0.5% Mn, 0.3% Zn, 0.15% Zr, 0.2% Sc, impurity ≦ 0.20%, balance Al. The preparation method for preparing the die-casting aluminum lithium alloy comprises the following steps:
s101: according to the designed alloy component proportion, weighing pure aluminum, pure lithium, pure copper, pure magnesium, pure zinc and Al-10% Mn, al-2% Sc and Al-10% Zr intermediate alloy as raw materials;
s102: putting pure aluminum into a self-made vacuum well type smelting furnace for smelting, wherein the smelting temperature is 750 ℃, and the vacuum degree in the furnace is 50kPa; after it is completely melted, adding pure copper, pure magnesium, pure zinc and Al-10% of Mn, al-2% of Sc, al-10% of Zr intermediate alloy for melting; subsequently, adjusting the temperature of the melt to 730 ℃, and refining the alloy melt for 5min by adopting a rotary argon blowing mode to obtain a high-quality Li-free alloy melt;
s103: adjusting the temperature of the Li-free alloy melt to 680 ℃, opening a furnace cover, adding pure Li particles wrapped by aluminum foil into the Li-free alloy melt by using a bell jar, adding a covering agent special for a commercially available aluminum-lithium alloy on the surface layer of the melt, heating the melt to 720 ℃ in a vacuum furnace under the protection of high-purity argon, and keeping the vacuum degree in the furnace at 100kPa to obtain a final aluminum-lithium alloy melt;
s104: inserting an ultrasonic amplitude transformer subjected to preheating treatment at 250 ℃ 15mm below the liquid level of the aluminum-lithium alloy melt for ultrasonic refining treatment, wherein the ultrasonic treatment time is 2min, the ultrasonic power is 2.0kW, and the ultrasonic temperature is 670 ℃;
and S105, before the molten metal enters a die cavity of the die-casting die, pumping out air in the die cavity, enabling the vacuum degree to reach more than 80kPa, pouring the aluminum-lithium alloy melt with the temperature of 660 ℃ after ultrasonic treatment into a die with the preheating temperature of 250 ℃, filling the die cavity at the injection speed of 3m/S, and carrying out vacuum high-pressure die-casting under the pressure of 80MPa to obtain the casting.
Example 3
The die-casting aluminum-lithium alloy of the embodiment comprises the following alloy components in percentage by mass: 2.5% Li, 1.5% Cu, 0.5% Mg, 0.5% Mn, 0.3% Zn, 0.2% Zr, 0.2% Sc, less than 0.20% impurity, balance Al. The preparation method for preparing the die-casting aluminum-lithium alloy comprises the following steps:
s101: according to the designed alloy component proportion, weighing pure aluminum, pure lithium, pure copper, pure magnesium, pure zinc and Al-10% Mn, al-2 Sc and Al-10% Zr intermediate alloy with corresponding content as raw materials;
s102: putting pure aluminum into a self-made vacuum well type smelting furnace for smelting, wherein the smelting temperature is 750 ℃, and the vacuum degree in the furnace is 50kPa; after it is completely melted, adding pure copper, pure magnesium, pure zinc and Al-10% of Mn, al-2% of Sc, al-10% of Zr intermediate alloy for melting; subsequently, adjusting the temperature of the melt to 730 ℃, and refining the alloy melt for 5min by adopting a rotary nitrogen blowing mode to obtain a high-quality Li-free alloy melt;
s103: adjusting the temperature of the Li-free alloy melt to 680 ℃, opening a furnace cover, adding pure Li particles wrapped by aluminum foil into the Li-free alloy melt by using a bell jar, adding a covering agent special for a commercially available aluminum-lithium alloy on the surface layer of the melt, heating the melt to 720 ℃ in a vacuum furnace under the protection of high-purity argon, and keeping the vacuum degree in the furnace at 100kPa to obtain a final aluminum-lithium alloy melt;
s104: inserting an ultrasonic amplitude transformer subjected to preheating treatment at 250 ℃ into 15mm below the liquid level of the aluminum-lithium alloy melt for ultrasonic refining treatment, wherein the ultrasonic treatment time is 2min, the ultrasonic power is 2.0kW, and the ultrasonic temperature is 670 ℃;
and S105, before the molten metal enters a die cavity of the die-casting die, pumping out air in the die cavity, enabling the vacuum degree to reach more than 80kPa, pouring the aluminum-lithium alloy melt with the temperature of 660 ℃ after ultrasonic treatment into a die with the preheating temperature of 250 ℃, filling the die cavity at the injection speed of 3m/S, and carrying out vacuum high-pressure die-casting under the pressure of 80MPa to obtain the casting.
Example 4 to example 9:
the alloy compositions and preparation methods of the die-cast aluminum lithium alloy castings of examples 4 to 9 are the same as example 1 except for the difference in the injection pressure, injection speed and degree of vacuum of the die cavity, as shown in table 1.
Comparative example 1
The alloy composition and melting process of comparative example 1 correspond to example 1, respectively, except that comparative example 1 is formed by conventional gravity casting.
Table 1 shows as-cast tensile mechanical properties (tensile strength and elongation) of cast aluminum lithium alloys prepared in different examples and comparative examples.
TABLE 1 mechanical Property test results of aluminum lithium alloys prepared in different examples and comparative examples
It can be seen from table 1 that the die-casting aluminum lithium alloy die casting provided by the invention has good toughness, higher tensile strength and elongation, and the as-cast comprehensive mechanical property of the die-casting aluminum lithium alloy die casting is far higher than that of the cast aluminum lithium alloy die casting formed by traditional gravity casting (namely a comparative example).
The preparation method of the invention combines the rotary blowing technology and the ultrasonic vibration technology to refine the melt obtained by the low vacuum melting method, and promotes the solute atoms to be uniformly dispersed and refined while removing gas and slag, and realizes vacuum die casting by adopting the vacuum degree of the die cavity above 80kPa, and simultaneously combines the preparation process and the design of the corresponding process of the invention, thereby effectively solving the casting defects of shrinkage porosity, component segregation, coarse crystal grains and the like in the aluminum lithium alloy casting formed by the traditional gravity casting, and further improving the obdurability, especially the plasticity of the vacuum high-pressure die-casting aluminum lithium alloy. The invention develops a vacuum high-pressure die-casting process matched with the cast aluminum-lithium alloy, so that the cast aluminum-lithium alloy has good obdurability, and the problem that the application of the cast aluminum-lithium alloy is limited due to the poor obdurability of the cast aluminum-lithium alloy to be solved urgently in the field is effectively solved.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A vacuum high-pressure die-casting forming method of a light high-strength and high-toughness aluminum lithium alloy casting is characterized by comprising the following steps:
s1, preparing raw materials according to components of an aluminum lithium alloy casting, wherein the raw materials at least comprise an aluminum raw material and a lithium raw material;
s2, carrying out low vacuum melting on the aluminum raw material, adding other raw materials except the lithium raw material after the aluminum raw material is completely melted, adjusting the temperature of the melt to 720-740 ℃, and refining the alloy melt by blowing inert gas in a rotating mode to obtain a high-quality lithium-free alloy melt;
s3, adjusting the temperature of the melt to 660-680 ℃, adding a lithium raw material into the lithium-free alloy melt, then adding a covering agent into the surface layer of the melt, and heating the alloy melt to 710-730 ℃ for smelting to obtain an aluminum-lithium alloy melt;
and S4, carrying out ultrasonic refining treatment on the aluminum lithium alloy melt, and carrying out vacuum high-pressure die-casting forming on the aluminum lithium alloy melt after the refining treatment to obtain the required light high-strength and high-toughness aluminum lithium alloy casting.
2. The vacuum high-pressure die-casting forming method for the light high-strength and high-toughness aluminum lithium alloy casting as claimed in claim 1, wherein in the step S2, the melting temperature of the aluminum raw material is 740 to 760 ℃; the refining treatment time is 3 min-5 min.
3. The vacuum high-pressure die-casting forming method of the light high-strength and high-toughness aluminum-lithium alloy casting as claimed in claim 1, wherein in the step S3, when adding the lithium raw material, the lithium raw material wrapped by the aluminum foil is added into the lithium-free alloy melt by using a bell jar, and protective gas is introduced for protection.
4. The vacuum high-pressure die-casting forming method of the light high-strength and high-toughness aluminum-lithium alloy casting as claimed in claim 1, wherein the steps S2 and S3 are carried out in a vacuum smelting furnace and realize low-vacuum smelting, and the vacuum degree in the vacuum smelting furnace is 50 kPa-60 kPa when the step S2 is carried out; and when the step S3 is executed, the vacuum degree in the vacuum melting furnace is 80 kPa-100 kPa.
5. The vacuum high-pressure die-casting forming method for the light high-strength and high-toughness aluminum-lithium alloy casting as claimed in claim 1, wherein in the step S4, the ultrasonic refining treatment specifically comprises the following steps: preheating an ultrasonic amplitude transformer to 200-300 ℃, and then inserting the preheated amplitude transformer into the melt to carry out ultrasonic vibration by 10-15 mm below the liquid level; the ultrasonic vibration temperature is 660-680 ℃, the ultrasonic vibration time is 1-3 min, the ultrasonic power is 1.5-2.8 kW, and protective gas is introduced for protection during ultrasonic vibration.
6. The vacuum high-pressure die-casting forming method for the light high-strength and high-toughness aluminum lithium alloy casting as claimed in claim 1, wherein in the step S4, the vacuum high-pressure die-casting forming specifically comprises the following steps: preheating a die in a die casting machine, and pumping out air in a die cavity of the die to form a preset vacuum degree; and (5) pouring the aluminum lithium alloy melt subjected to the ultrasonic refining treatment in the step (S4) into a pressure chamber of a die casting machine, and pressing the aluminum lithium alloy melt into a die cavity of a die to obtain the light high-strength high-toughness aluminum lithium alloy casting.
7. The vacuum high-pressure die-casting forming method for the light high-strength and high-toughness aluminum lithium alloy casting as claimed in claim 6, wherein the conditions of the vacuum high-pressure die-casting forming are as follows: the preheating temperature of the die is 200-250 ℃, the pouring temperature of the aluminum lithium alloy melt is 650-670 ℃, the injection pressure of the die casting machine is 80-120 MPa, the injection speed is 3-5 m/s, and the vacuum degree in the die cavity is 80-100 kPa.
8. A light weight high strength and toughness aluminum lithium alloy casting made by the method of any one of claims 1-7.
9. The light-weight high-strength and high-toughness aluminum lithium alloy casting of claim 8, wherein the cast tensile strength of the light-weight high-strength and high-toughness aluminum lithium alloy casting reaches 300-320 MPa, and the elongation of the light-weight high-strength and high-toughness aluminum lithium alloy casting reaches 10% -18.5%.
10. The light-weight, high toughness aluminum lithium alloy casting of claim 8 wherein the light-weight, high toughness aluminum lithium alloy casting is an aluminum lithium copper magnesium alloy casting containing 2% to 3% li.
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| CN117816925A (en) * | 2024-03-04 | 2024-04-05 | 成都成德重型锻造有限公司 | Die casting device and die casting method for saturated filling of dense cavity |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117816925A (en) * | 2024-03-04 | 2024-04-05 | 成都成德重型锻造有限公司 | Die casting device and die casting method for saturated filling of dense cavity |
| CN117816925B (en) * | 2024-03-04 | 2024-05-17 | 成都成德重型锻造有限公司 | Die casting device and die casting method for saturated filling of dense cavity |
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