CN117568673A - High-fluidity low-thermal-cracking cast aluminum alloy and preparation process thereof - Google Patents
High-fluidity low-thermal-cracking cast aluminum alloy and preparation process thereof Download PDFInfo
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- 238000005336 cracking Methods 0.000 claims abstract description 34
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 23
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 19
- 238000004519 manufacturing process Methods 0.000 claims abstract description 18
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 15
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 13
- 229910052802 copper Inorganic materials 0.000 claims abstract description 8
- 230000009471 action Effects 0.000 claims abstract description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 47
- 229910002804 graphite Inorganic materials 0.000 claims description 47
- 239000010439 graphite Substances 0.000 claims description 47
- 238000005266 casting Methods 0.000 claims description 40
- 238000007670 refining Methods 0.000 claims description 29
- 239000011701 zinc Substances 0.000 claims description 28
- 239000007788 liquid Substances 0.000 claims description 25
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- 239000012535 impurity Substances 0.000 claims description 6
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- 229910004806 Na2 SiO3.9H2 O Inorganic materials 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/02—Alloys based on aluminium with silicon as the next major constituent
- C22C21/04—Modified aluminium-silicon alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D37/00—Controlling or regulating the pouring of molten metal from a casting melt-holding vessel
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D7/00—Casting ingots, e.g. from ferrous metals
- B22D7/005—Casting ingots, e.g. from ferrous metals from non-ferrous metals
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/003—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals by induction
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/05—Refining by treating with gases, e.g. gas flushing also refining by means of a material generating gas in situ
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/026—Alloys based on aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/03—Making non-ferrous alloys by melting using master alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/06—Making non-ferrous alloys with the use of special agents for refining or deoxidising
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
- C22F1/043—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with silicon as the next major constituent
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
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- Metallurgy (AREA)
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- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
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Abstract
The invention discloses a high-fluidity low-thermal-cracking cast aluminum alloy and a preparation process thereof. The high-fluidity low-heat-cracking cast aluminum alloy comprises the following components in percentage by mass: 6.50 to 7.50 percent of Si, 0.25 to 0.45 percent of Mg, 0.10 to 0.20 percent of Cu, 0.015 to 0.025 percent of P, 0.40 to 0.80 percent of Mn, 0.60 to 0.90 percent of Zn, less than or equal to 0.12 percent of Fe and the balance of aluminum. P reduces the grain size of the alloy, improves the morphology of eutectic Si phase together with Mn and Zn, converts eutectic Si from needle shape into coral shape, simultaneously improves the morphology of Fe-rich phase together with Mn and Zn, converts long needle-shaped beta-Fe into Chinese character shape alpha-Fe, and weakens the splitting action of the long needle-shaped beta-Fe on a matrix. The invention ensures the high strength of the alloy, improves the fluidity and the hot cracking resistance of the alloy and reduces the production cost.
Description
Technical Field
The invention belongs to the field of new aluminum alloy materials, and particularly relates to a high-fluidity low-heat-cracking cast aluminum alloy and a preparation process thereof.
Background
The aluminum alloy is used as a material with low density and high specific strength, has the advantages of good plasticity, processability, rich raw materials and the like, and becomes a basic strategic material in the industrial fields of aviation, aerospace, rail transit and the like. With the development of science and technology, "environmental protection" and "green manufacturing" have become the main directions of the 21 st century manufacturing industry development, and green competitiveness must also become an important component of manufacturing industry competition. Under this general trend, how to change the traditional manufacturing mode, implement the green manufacturing technology, develop the related green materials, etc. becomes a current development trend and upgrade strategy. In order to cope with this trend, the automobile manufacturing industry production is advancing toward weight reduction.
The automobile is light, and besides the aluminum alloy part is adopted to replace the traditional steel part, the automobile can be realized through the thinning of complex parts. The alloy has excellent fluidity, which is the basic condition for obtaining high-quality castings of complex thin-walled parts. The alloy with poor fluidity is not easy to fill a thin and complex cavity, thereby being not favorable for casting castings with clear outlines, easily generating defects of insufficient casting, cold insulation and the like, and also being not favorable for feeding shrinkage generated in the solidification process of the alloy, and increasing the defects of air holes, slag inclusion, shrinkage cavities, shrinkage porosity and the like. In the casting production of complex thin-walled parts, thermal cracking is also a serious defect which is very easy to generate. If the heat cracking resistance of the casting is poor, when the thin-wall casting with large adjacent wall thickness difference is produced, hot cracks are easily formed due to large solidification shrinkage difference, and the performance, particularly the mechanical performance, of the part can be seriously affected. Thermal cracks present in the parts can develop under practical conditions and even lead to overall fracture, causing serious accidents and losses. Therefore, the production of complex thin-walled parts requires that the cast alloy have excellent fluidity and hot cracking resistance.
Al-Si cast alloys such as ZL101 are often used in the automobile industry, and as cast structures are composed of needle-shaped eutectic silicon and coarse alpha-Al dendrites, high-strength castings with complete casting shapes and few casting defects are difficult to obtain due to limited flowability and heat cracking resistance in the production of complex thin-walled parts (wall thickness is less than or equal to 5 mm) of automobiles, so that the yield is low in the production of such products. The compound modification is carried out by students to enlarge the application range. If rare earth elements are used for composite modification, the fluidity and the thermal cracking resistance can be improved, but the production cost is higher. In recent years, B-containing refiners (such as Al-Ti-B) have been used for complex modification to improve fluidity, but TiB is contained therein 2 The aggregation and precipitation are easy, the refining effect of the alloy is unstable, and the fluidity improving effect is also unstable. At present, the problems of insufficient production fluidity and thermal cracking defects of complex thin-walled parts cannot be met by the methods. Therefore, there is an urgent need to develop a high-flow low-thermal-cracking cast aluminum alloy and a preparation process thereof.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a high-flow low-heat-cracking cast aluminum alloy and a preparation process thereof. The invention adopts P, mn and Zn to carry out multielement composite modification on Al-Si alloy, improves the microstructure of the Al-Si alloy through the technological processes of smelting casting, heat treatment and the like, effectively avoids the influence of flaky eutectic silicon and coarse alpha-Al dendrites of an as-cast knitting needle of the Al-Si alloy on the fluidity and the heat cracking resistance of the alloy, prepares the high-flow low-heat-cracking cast aluminum alloy under the condition of ensuring the alloy to have high strength, reduces the production cost, and is favorable for being widely applied to the manufacturing industry of automobile parts.
The specific scheme is as follows:
the invention relates to a high-flow low-heat-cracking cast aluminum alloy which comprises the following components in percentage by mass:
6.50 to 7.50 percent of Si, 0.25 to 0.45 percent of Mg, 0.10 to 0.20 percent of Cu, 0.015 to 0.025 percent of P, 0.40 to 0.80 percent of Mn, 0.60 to 0.90 percent of Zn, less than or equal to 0.12 percent of Fe (impurity element) and the balance of aluminum.
The invention relates to a preparation process of a high-flow low-heat-cracking cast aluminum alloy, which comprises the following steps:
s1, proportioning: calculating theoretical batching amount according to raw material components and target components, weighing industrial pure aluminum with the purity of 99.9wt%, al-21.5wt% Si intermediate alloy, al-50wt% Mg intermediate alloy, al-10wt% Cu intermediate alloy, al-4wt% P intermediate alloy, al-10wt% Mn intermediate alloy and industrial pure zinc with the purity of 99.9wt% and drying to finish batching;
s2, coating and drying: in order to prevent the aluminum alloy melt from reacting with the tool in the casting process, uniformly coating the coating on the contact surfaces of a graphite clay crucible, a smelting tool and a die, drying the graphite clay crucible in a smelting furnace, polishing the weighed alloy by using sand paper to remove a surface oxide layer, and then drying and preheating the alloy in a drying oven at 200-300 ℃;
s3, smelting and casting: sequentially adding Al-Si intermediate alloy and pure aluminum into a graphite clay crucible preheated to 450 ℃, then heating to 750 ℃ along with a furnace, stirring, standing and preserving heat for 20min after all the Al-Si intermediate alloy and the pure aluminum are melted; then adding Al-Cu intermediate alloy, al-Mn intermediate alloy and pure Zn, fully stirring after all melting, and keeping the temperature and standing for 20min; then wrapping Al-Mg intermediate alloy and Al-P intermediate alloy with aluminum foil, rapidly placing into molten alloy liquid, pressing the molten alloy liquid into the bottom of the alloy liquid by using a slag ladle to reduce oxidation burning loss, fully stirring, adjusting the furnace temperature to 750 ℃, and keeping the temperature and standing for 20min;
s4, refining: removing dross on the surface of the alloy melt by a skimming ladle, introducing inert gas after skimming, and adding C 2 C1 6 Turning on the control device, refining the combination by using a graphite rotor and an alternating electromagnetic field, standing and preserving heat for 10-15min, and skimming again; then inert gas is introduced, a deslagging agent is added, a control device is opened, a graphite rotor and an alternating electromagnetic field are utilized for refining, standing and heat preservation are carried out for 10-15min, and deslagging is carried out; then heating the alloy melt to 750 ℃ along with a furnace, standing and preserving heat for 10-15min;
s5, pouring: taking out a metal mould preheated at 200-300 ℃ from a constant-temperature drying oven, pouring the alloy melt obtained in the step S4 into the mould, and cooling to obtain an alloy cast ingot;
s6, solution treatment and artificial aging treatment: and sequentially carrying out solution treatment and artificial aging treatment on the obtained alloy cast ingot.
Further, in step S1, the Al-21.5wt% Si master alloy is an Al-Si master alloy containing 21.5% Si by mass, and so on.
Further, in step S2, the chemical components of the coating are formed into Na according to the mass ratio 2 SiO 3 ·9H 2 O：ZnO：H 2 O＝1：4：15。
Further, in step S4, C 2 C1 6 And the adding amount of the deslagging agent is 0.5% of the total alloy, and the deslagging agent is wrapped by aluminum foil, wherein the deslagging agent comprises 50% NaCl+50% KCl.
Further, in the step S4, the inert gas is one of nitrogen and argon, the rotating speed of the graphite rotor is 400r/min, the blowing flow is 7-8L/min, the frequency of the alternating electromagnetic field is 50kHz, the coil current is 100-130A, and the acting time is 10-15min.
The graphite rotor comprises a plurality of turntables and a graphite rod connecting shaft, and the turntables are connected with the connecting shaft through threads; the rotary table is of a hollow structure, an axial through hole is formed in the middle of the connecting shaft, and the through hole is communicated with the interior of the rotary table; a plurality of through holes are arranged on the surface (comprising upper and lower surfaces and side walls) of the turntable.
Further, a plurality of groups of through holes are formed in the surface of the turntable along the circumferential direction, and each group of through holes comprises a plurality of through holes uniformly distributed along the radial direction at intervals.
Preferably, the turntables are arranged in three modes of up, down, and the distance between the turntables is equal, and the diameter ratio of the three turntables is 1:1.25:1.
Further, in step S5, the graphite clay crucible is taken out from the high-frequency induction furnace, and the time required for casting the alloy melt is not longer than 15S.
Further, in step S6, the solution treatment process is as follows: solid solution heat preservation at 550 ℃ for 5 hours; quenching with water and warm water at 70-80 ℃. The artificial aging process comprises the following steps: aging at 210 ℃ and preserving heat for 3-6h, discharging and air cooling.
The design basis of the method is as follows:
the invention relates to a high-flow low-heat-cracking cast aluminum alloy and a preparation process thereof, wherein in the casting process, a multi-layer nozzle graphite rotor and an alternating electromagnetic field combination shown in figure 1 are adopted for refining. Compared with a single-layer nozzle rotor, the multi-layer rotor increases the contact area between gas and molten liquid, and the upper, middle and lower three-layer rotor blades can refine different areas in the molten liquid, so that the disadvantages of refining blind areas are overcome; besides the gas sprayed by the rotor of the layer, the upper layer of molten liquid can be purified by the gas sprayed by the rotor of the layer, so that the multiple purifying effect is realized; meanwhile, the blades with different diameters not only reduce the resistance when the blades are put into a melt, but also are beneficial to gas purification and melt flow, and can promote the homogenization of alloy components under the conditions that the rotating speed of a rotor is 400r/min and the blowing flow is 7-8L/min. The electromagnetic field with the frequency of 50Hz and the coil current of 100-130A is added outside the crucible, and the impurities move to the top, the bottom or the container wall of the container under the pressure gradient formed by gravity, buoyancy, centrifugal force and electromagnetic force in the melt and are collided, separated and removed. Under the condition that the frequency of an alternating electromagnetic field is unchanged at 50Hz, when the coil current is lower than 100A, the separation rate of small-size inclusions in the melt is more than 95%, and the resultant force of large-size inclusions is insufficient and cannot move to the top, bottom or container wall of the melt to be removed; when the coil current is 100-130A, the impurities are almost completely moved to the top, the bottom or the container wall of the melt to be removed, and the separation rate is more than 95 percent to obtain castings with better quality; when the coil current is higher than 130A, the intensity of the flow of the melt increases due to the increase of the coil current, and the inclusions which are washed by the melt and migrate to the edge are re-entangled in the solution, so that the inclusion separation rate is reduced. The oxide inclusion content is proportional to the gas content, so that the removal of the oxide inclusion is beneficial to the escape and removal of the gas in the molten liquid, and the escape of the gas can adsorb the inclusion to float out of the surface of the molten liquid. Therefore, the multi-layer nozzle graphite rotor and the alternating electromagnetic field (the magnetic field frequency is 50Hz, the coil current is 120A) are combined for refining, the refining effect is improved, the casting defects and the flow resistance of the molten liquid are reduced, and the high-flow low-heat-cracking cast aluminum alloy is obtained.
According to the high-flow low-heat-cracking cast aluminum alloy and the preparation process thereof, P is used for improving the alpha-Al matrix, mn and Zn are used for improving the harmful influence of eutectic Si and Fe on the alloy, improving the heat-cracking performance of the alloy and increasing the compactness of castings. If the amount of P added is less than 0.015%, the AlP particles of the heterogeneous core point provided are insufficient, and the coarse and complex alpha-Al dendrite network formed during alloy solidification cannot be well improved, so that the flow filling of the melt is blocked, and casting defects such as shrinkage porosity and shrinkage cavity are easily generated. The Mn addition amount is lower than 0.4 weight percent, the Zn addition amount is lower than 0.6 weight percent, the eutectic Si phase modification effect is poor, and the morphology is still mainly in the shape of needle sheets; the needle-shaped beta-Fe is converted into dendritic or network-shaped iron-rich phases, and the needle-shaped beta-Fe has a small amount of Chinese character-shaped iron-rich phases, but the needle-shaped beta-Fe has relatively large size; although the cracking effect of the iron-rich phase relative to the matrix is reduced, and the generation of crack sources is reduced, the iron-rich phase is generated before the alpha-Al solid solution, dendritic or network-shaped iron-rich phase can increase the flow resistance of the melt, reduce the fluidity of the melt, and are not beneficial to filling the casting mould with the melt, so that a casting with good compactness and complete shape is obtained. If the ratio of the addition amounts of P, mn and Zn is (3-4): (80-160): and (120-180) the composite modification effect is good, and the cast aluminum alloy with few casting defects, high strength, high flow and low thermal cracking is obtained. Firstly, a large number of AlP particles can be used as heterogeneous nucleation substrates of alpha-Al which is precipitated first to play a role in refining grains; meanwhile, alP can play a role of a heterogeneous nucleation substrate in the precipitation process of Si phase, so that the nucleation supercooling degree of eutectic Si is reduced, the growth mode of the eutectic Si phase is changed, a plurality of silicon-poor areas are formed in the alloy due to the high nucleation rate of the eutectic Si phase, and the nucleation of alpha-Al is promoted, so that alpha-Al is thinned, fine grains are obtained, and the fluidity is improved. As the thermal cracking force of the alloy tends to increase along with the increase of the grain size of the alloy, the modification of 0.015-0.025 percent P reduces the thermal cracking force of the alloy, improves the thermal cracking resistance of the alloy and obtains the casting alloy with high flow and low thermal cracking. Secondly, 0.4 to 0.8 percent of Mn and 0.6 to 0.9 percent of Zn are compounded and modified to lead the eutectic Si phase to be composed ofThe needle is changed into a short rod shape or a coral shape, so that the flow resistance of molten liquid when the molten liquid fills the cavity is reduced, meanwhile, the thinned and modified eutectic silicon phase improves the elongation and strength of the alloy, and meanwhile, the grain boundary strength of the alloy is improved, the toughness of the alloy is further improved, and the thermal cracking performance of the alloy is improved. Finally, after 0.015 to 0.025 percent of P, 0.4 to 0.8 percent of Mn and 0.6 to 0.9 percent of Zn are compositely modified, the Fe-rich phase is mainly a Chinese character-shaped Fe-rich phase, and because the radiuses of Mn, zn and Fe atoms are similar to the crystal structure, part of Fe atoms are replaced by Mn and Zn atoms in the process of forming the Fe-rich phase, an alpha-AlSiFeMnZn Fe-rich phase is formed, the growth trend of the Fe-rich phase in a single direction is inhibited, and meanwhile, the two ends of the Fe-rich phase are not sharp any more and the size is reduced. The transformation of the iron-rich phase in morphology effectively reduces the flow resistance of the molten liquid when filling the cavity, and meanwhile, fe in the molten liquid reacts with P to generate Fe 3 P is precipitated to the bottom of the molten liquid, so that the harm of Fe to the fluidity is reduced, and the capacity of filling the molten liquid into the cavity is improved. In addition, P inhibits Al-Fe phase from generating at the grain boundary with higher energy, and the needle-shaped beta-Fe phase with larger brittleness is reduced, so that the alloy is not easy to break when being subjected to tensile force, and the alloy is beneficial to improving the mechanical property, especially the toughness, of the alloy, and is beneficial to improving the thermal cracking property of the alloy. If P is added more than 0.025%, alP particles are saturated as heterogeneous nucleation particles, agglomeration and growth phenomenon can occur, but the number of effective nucleation cores can be reduced, so that the refining effect is reduced, and meanwhile, excessive P promotes Al-Fe phases to be removed from grain boundaries, so that the heat cracking resistance of the alloy is poor, and the heat cracking force is increased. If the Mn content exceeds 0.8wt% and the Zn content exceeds 0.9wt%, the modification effect on eutectic Si is deteriorated, and the modification effect is changed from a short rod shape or coral shape to a previous needle shape, and the aspect ratio thereof is increased; the needle-shaped beta-Fe phase in the alloy is basically converted into Chinese character-shaped alpha-Fe phase, and then Mn is added to generate other intermetallic compounds ((Fe, mn) Al) 6 ) The fluidity of the alloy is reduced; on the other hand, a high Zn content tends to promote cracking due to an increase in shrinkage during solidification of the alloy. In summary, the mass fraction of P is preferably 0.015-0.025%, the mass fraction of Mn is preferably 0.4-0.8%, and the mass fraction of Zn is preferably 0.6-0.9％。
According to the high-flow low-heat-cracking cast aluminum alloy and the preparation process thereof, zn has the effects except the effects, and a T phase (AlZnMgCu quaternary phase) is generated in the alloy, so that the second-phase strengthening effect is achieved. If the Zn addition amount is less than 0.6wt%, zn is solid-dissolved in the matrix, and T phase is not formed in the alloy. If Zn is added in an amount of 0.6-0.9 wt%, granular T phase with a size of 1-2 mu m is generated in the alloy, dispersed and distributed in a matrix, and the movement of pinning dislocation is hindered in tensile deformation, so that the alloy strength is improved, the fracture mode is ductile-brittle mixed fracture mainly comprising ductile fracture, and more T phase and theta phase (Al are present at the fracture 2 Cu) and Al 3 Mg 2 The ductile fossa is more and deeper. In the subsequent heat treatment, the T phase has small size (50-100 nm) and dispersed (15-25/μm) 2 ) The dispersion strengthening effect is obvious, meanwhile, the T phase can induce the theta phase to form nuclei around the T phase to grow, the size is 1-3 nm, and the density is 50-75/mu m 2 And the theta phase in this state plays a strong second-phase strengthening role with respect to the alloy. The superposition of these factors greatly improves the strength of the alloy of the invention. However, the toughness of the alloy decreases with the increase of Zn, if the addition amount of Zn exceeds 0.9wt%, although T is continuously increased, a needle-shaped primary zinc-rich phase (AlZnMg phase) fracture matrix is generated in the alloy, so that the fracture mode is converted into ductile-brittle mixed fracture mainly comprising brittle fracture, more cleavage steps and tearing edges appear, and Al at the fracture part 3 Mg 2 The phase disappeared, the ductile fossa was less and shallow. This is disadvantageous in obtaining high flow low thermal cracking alloys with good overall mechanical properties.
Compared with the prior art, the invention has the beneficial effects that:
(1) According to the high-flow low-heat-cracking cast aluminum alloy and the preparation process thereof, in the casting process, the multi-layer nozzle graphite rotor and the alternating electromagnetic field are adopted for refining, so that the disadvantages of refining blind areas are overcome, the multiple purifying effect can be realized, the homogenization of the components of molten liquid is improved, the separation of impurities with different electromagnetic properties from the molten aluminum liquid is realized, the escape of gas is promoted, the refining effect is improved, the casting defects are reduced, and the high-flow low-heat-cracking cast aluminum alloy is obtained.
(2) The invention relates to a high-flow low-heat-cracking cast aluminum alloy and a preparation process thereof, wherein a P refiner, mn and Zn are mixed according to the following steps of (3-4): (80-160): the proportion of (120-180) is added into the alloy, and is applied to modification treatment and fluidity improvement of hypoeutectic Al-Si alloy, 80% of P element in the alloy exists in the form of AlP particles to serve as heterogeneous nuclear particles, grains are thinned, the harmful effects of eutectic Si and Fe on the alloy are improved, the fluidity, the compactness and mechanical properties of castings, especially toughness of the alloy are improved, and the hot cracking resistance of the alloy is also improved. The fluidity of the prepared casting alloy is measured by adopting a concentric three-helix alloy fluidity tester according to the national standard GB/T5611-2017, wherein the casting temperature is controlled to be 750 ℃, the length of the prepared alloy fluidity sample can reach 419.7-445.9 mm, and the fluidity of the prepared alloy is obviously superior to the performance of the common ZL101 casting aluminum alloy (the fluidity of the ZL101 alloy in use is generally not higher than 385 mm); the thermal cracking property is measured by adopting a ZQS-2000 thermal cracking tester, the thermal cracking force of the alloy is 1433.5N-1510.3N, and the reduction of 19.8-23.9 percent is realized.
(3) According to the high-fluidity low-heat-cracking cast aluminum alloy and the preparation process thereof, the added Zn generates dispersed fine T phases, so that the theta phases are promoted to be dispersed uniformly in the alloy, and the strength of the alloy is improved. In addition, the reinforcing phase T phase precipitated in the alloy in the subsequent solid solution aging heat treatment can induce the theta phase to nucleate and grow around the theta phase, and the alloy obtains higher strength through second phase reinforcement. The tensile strength of the alloy after heat treatment is 317.2-346.1 MPa, the elongation is 9.5-11.6%, which obviously exceeds the performance of common Al-Si casting alloy (according to national standard GB/T1173-2013, the tensile strength is not higher than 300MPa, and the elongation is lower than 6%).
(4) The high-fluidity low-heat-cracking cast aluminum alloy and the preparation process thereof have the advantages that the added P, mn and Zn elements are low in price and easy to obtain, the production cost is reduced by 20-30 percent relative to rare earth modified alloy and the like under the requirement of ensuring higher strength and obtaining the high-fluidity low-heat-cracking cast aluminum alloy.
Drawings
FIG. 1 is a schematic view of a casting apparatus for casting an aluminum alloy with high flow and low thermal cracking according to the present invention.
FIG. 2 is a schematic view of a multi-layer graphite rotor used in the present invention; fig. 3 is a top view of a rotor disk in a multi-layer graphite rotor.
FIG. 4 shows the morphology of eutectic Si alloy in the present invention, (a) unmodified, and (b) modified.
FIG. 5 shows a morphology diagram and an energy spectrum diagram of an Fe-rich phase of the alloy, and a morphology diagram of an Fe-rich phase and an energy spectrum diagram of an Fe-rich phase of the alloy.
FIG. 6 shows the structure patterns and energy spectra of the T phase and the theta phase after the heat treatment of the alloy, the structure patterns of the T phase and the theta phase, the energy spectrum of the point A, and the energy spectrum of the point B.
Detailed Description
Exemplary embodiments, features and aspects of the invention will be described below in conjunction with specific embodiments.
The embodiment of the invention uses a multi-layer graphite rotor which comprises a plurality of turntables and a graphite rod connecting shaft, wherein the turntables are specifically arranged as an upper turntable, a middle turntable and a lower turntable, the distance between the turntables is 50mm, and the diameter ratio of the turntables is 1:1.25:1. The diameter of the graphite rod connecting shaft is 20mm, the diameter of the inner through hole is 10mm, the turntable is provided with a threaded hole with the diameter of 20mm, and the turntable is connected with the connecting shaft through threads. The rotary table is of a hollow structure, an axial through hole is formed in the middle of the connecting shaft, and the through hole is communicated with the interior of the rotary table; and a plurality of groups of through holes are formed in the surface of the turntable along the circumferential direction, each group of through holes comprises a plurality of through holes uniformly distributed along the radial direction at intervals, and the center distances of the adjacent through holes are 10mm. The aperture ratio of the through holes formed by the upper turntable, the middle turntable and the lower turntable is 1:2:3, wherein the diameter of the through hole of the middle turntable is 2mm.
Specifically, the high-flow low-thermal cracking cast aluminum alloy comprises the following components in percentage by mass:
6.50 to 7.50 percent of Si, 0.25 to 0.45 percent of Mg, 0.10 to 0.20 percent of Cu, 0.015 to 0.025 percent of P, 0.40 to 0.80 percent of Mn, 0.60 to 0.90 percent of Zn, less than or equal to 0.12 percent of Fe (impurity element) and the balance of aluminum.
Specifically, the preparation process of the high-flow low-heat-cracking cast aluminum alloy comprises the following steps:
s1, proportioning: calculating theoretical batching amount according to raw material components and target components, weighing industrial pure aluminum with the purity of 99.9wt%, al-21.5wt% Si intermediate alloy, al-50wt% Mg intermediate alloy, al-10wt% Cu intermediate alloy, al-4wt% P intermediate alloy, al-10wt% Mn intermediate alloy and industrial pure zinc with the purity of 99.9wt% and drying to finish batching;
s2, coating and drying: in order to prevent the aluminum alloy melt from reacting with the tool in the casting process, uniformly coating the coating on the contact surfaces of a graphite clay crucible, a smelting tool and a die, drying the graphite clay crucible in a smelting furnace, polishing the weighed alloy by using sand paper to remove a surface oxide layer, and then drying and preheating the alloy in a drying oven at 200-300 ℃;
s3, smelting and casting: sequentially adding Al-Si intermediate alloy and pure aluminum into a graphite clay crucible preheated to 450 ℃, then heating to 750 ℃ along with a furnace, stirring, standing and preserving heat for 20min after all the Al-Si intermediate alloy and the pure aluminum are melted; then adding Al-Cu intermediate alloy, al-Mn intermediate alloy and pure Zn, fully stirring after all melting, and keeping the temperature and standing for 20min; then wrapping Al-Mg intermediate alloy and Al-P intermediate alloy with aluminum foil, rapidly placing into molten alloy liquid, pressing the molten alloy liquid into the bottom of the alloy liquid by using a slag ladle to reduce oxidation burning loss, fully stirring, adjusting the furnace temperature to 750 ℃, and keeping the temperature and standing for 20min;
s4, refining: removing dross on the surface of the alloy melt by a skimming ladle, introducing inert gas after skimming, and adding C 2 C1 6 Turning on the control device, refining the combination by using a graphite rotor and an alternating electromagnetic field, standing and preserving heat for 10-15min, and skimming again; then inert gas is introduced, a deslagging agent is added, a control device is opened, a graphite rotor and an alternating electromagnetic field are utilized for refining, standing and heat preservation are carried out for 10-15min, and deslagging is carried out; then heating the alloy melt to 750 ℃ along with a furnace, standing and preserving heat for 10-15min;
s5, pouring: taking out a metal mould preheated at 200-300 ℃ from a constant-temperature drying oven, pouring the alloy melt obtained in the step S4 into the mould, and cooling to obtain an alloy cast ingot;
s6, solution treatment and artificial aging treatment: and sequentially carrying out solution treatment and artificial aging treatment on the obtained alloy cast ingot. The solution treatment process comprises the following steps: solid solution heat preservation at 550 ℃ for 5 hours; quenching with water and warm water at 70-80 ℃. The artificial aging process comprises the following steps: aging at 210 ℃ and preserving heat for 3-6h, discharging and air cooling.
In the step S2, the chemical components of the coating are Na 2 SiO 3 .9H 2 O：ZnO：H 2 O＝1：4：15。
In step S4, C 2 C1 6 And the adding amount of the deslagging agent is 0.5% of the total alloy, and the deslagging agent is wrapped by aluminum foil, wherein the deslagging agent comprises 50% NaCl+50% KCl.
In the step S4, the inert gas is one of nitrogen and argon, the rotating speed of the multi-nozzle graphite rotor is 400r/min, the blowing flow is 7-8L/min, the frequency of the alternating electromagnetic field is 50kHz, the coil current is 100-130A, and the acting time is 10-15min.
In the step S5, the graphite clay crucible is taken out from the pit furnace, and the time required for casting the alloy melt is not more than 15 seconds.
TABLE 1 raw materials for alloys in comparative examples, examples 1 to 15 were composed by mass percent
Comparative example:
calculating theoretical batching amount by using raw material components and target components, weighing industrial pure aluminum with the purity of 99.9wt%, al-21.5wt% Si master alloy, al-50wt% Mg master alloy and Al-10wt% Cu master alloy, and drying to finish batching.
In order to prevent the aluminum alloy melt from reacting with the tool in the casting process, the coating is uniformly coated on a graphite clay crucible, a smelting tool and a mould, the graphite clay crucible is placed in a smelting furnace for drying, and the weighed alloy is polished by sand paper to remove a surface oxide layer and then placed in a drying box at 200-300 ℃ for drying and preheating.
Sequentially adding the Al-Si intermediate alloy and pure aluminum into a graphite clay crucible preheated to 450 ℃, then heating to 750 ℃ along with a furnace, stirring, standing and preserving heat for 20min after all the Al-Si intermediate alloy and the pure aluminum are melted; then adding Al-Cu intermediate alloy, fully stirring after all melting, and keeping the temperature and standing for 20min; then wrapping Al-Mg intermediate alloy with aluminum foil, rapidly placing into molten alloy liquid, pressing into the bottom of the alloy liquid by using a slag ladle to reduce oxidation burning loss, fully stirring, adjusting the furnace temperature to 750 ℃, and keeping the temperature and standing for 20min.
Removing dross on the surface of the alloy melt by a skimming ladle, adding C 2 C1 6 Standing and preserving heat for 10-15min, and skimming again; adding deslagging agent, standing and preserving heat for 10-15min, and deslagging; and then heating the alloy melt to 750 ℃ along with a furnace, standing and preserving heat for 10-15min.
Taking out the preheated metal mould at 200-300 ℃ from the constant temperature drying oven, then pouring the obtained alloy melt into the mould, and cooling to obtain the alloy cast ingot.
And sequentially carrying out solution treatment and artificial aging treatment on the obtained alloy cast ingot. The solution treatment process comprises the following steps: solid solution heat preservation at 550 ℃ for 5 hours; quenching with water and warm water at 70-80 ℃. The artificial aging process comprises the following steps: aging at 210 ℃ and preserving heat for 3 hours, discharging and air cooling.
Example 1:
the ingredients of this example are shown in Table 1.
The preparation method of this example is the same as that of the comparative example.
Example 2:
the ingredients of this example are shown in Table 1.
The preparation method of this example is the same as that of the comparative example.
Example 3:
the ingredients of this example are shown in Table 1.
The preparation method of this example is the same as that of the comparative example.
Example 4:
the ingredients of this example are shown in Table 1.
The preparation method of this example is the same as that of the comparative example.
Example 5:
the ingredients of this example are shown in Table 1.
The preparation method of this example is the same as that of the comparative example.
Example 6:
the ingredients of this example are shown in Table 1.
The preparation method of this example is the same as that of the comparative example.
Example 7:
the ingredients of this example are shown in Table 1.
The preparation method of this example is the same as that of the comparative example.
Example 8:
the ingredients of this example are shown in Table 1.
The preparation method of this example is the same as that of the comparative example.
Example 9:
the ingredients of this example are shown in Table 1.
The preparation method of this example is the same as that of the comparative example.
Example 10:
the ingredients of this example are shown in Table 1.
The preparation method of the embodiment is the same as that of the comparative example, but the single-layer graphite rotor is added for refining, the rotating speed of the graphite rotor is 400r/min, the blowing flow is 7L/min, and the action time is 10min.
Example 11:
the ingredients of this example are shown in Table 1.
The preparation method of the embodiment is the same as that of the comparative example, but the multi-layer graphite rotor is added for refining, the rotating speed of the graphite rotor is 400r/min, the blowing flow is 7L/min, and the action time is 10min.
Example 12:
the ingredients of this example are shown in Table 1.
The preparation method of the embodiment is the same as that of the comparative example, but a multi-layer graphite rotor and an alternating electromagnetic field refining combination are added during refining, wherein the rotating speed of the graphite rotor is 400r/min, the blowing flow is 7L/min, the frequency of the alternating electromagnetic field magnetic field is 50Hz, the coil current is 100A, and the acting time is 10min.
Example 13:
the ingredients of this example are shown in Table 1.
The preparation method of the embodiment is the same as that of the comparative example, but a multi-layer graphite rotor and an alternating electromagnetic field refining combination are added during refining, wherein the rotating speed of the graphite rotor is 400r/min, the blowing flow is 7L/min, the frequency of the alternating electromagnetic field magnetic field is 50Hz, the coil current is 120A, and the acting time is 10min.
Example 14:
the ingredients of this example are shown in Table 1.
The preparation method of the embodiment is the same as that of the comparative example, but a multi-layer graphite rotor and an alternating electromagnetic field refining combination are added during refining, wherein the rotating speed of the graphite rotor is 400r/min, the blowing flow is 7L/min, the frequency of the alternating electromagnetic field magnetic field is 50Hz, the coil current is 130A, and the acting time is 10min.
Example 15:
the ingredients of this example are shown in Table 1.
The preparation method of the embodiment is the same as that of the comparative example, but a multi-layer graphite rotor and an alternating electromagnetic field refining combination are added during refining, wherein the rotating speed of the graphite rotor is 400r/min, the blowing flow is 7L/min, the frequency of the alternating electromagnetic field magnetic field is 50Hz, the coil current is 120A, and the acting time is 10min.
The overall properties of the alloy produced by the present invention are shown in Table 2 below.
Table 2 alloy combination properties
* A is before heat treatment, and b is after heat treatment.
2. The flow test sample length was repeated 3 times and averaged.
According to the high-fluidity low-heat-cracking cast aluminum alloy and the preparation process thereof, the mechanical property of the Al-Si cast aluminum alloy is improved, and compared with a comparative example, the tensile strength in an as-cast state is maximally improved to 231.1MPa, the tensile strength is increased by 48.8%, the elongation is maximally improved to 7.1%, and the tensile strength is increased by 121.9%; the tensile strength after solution aging treatment is maximally improved to 346.1MPa, increased by 38.8%, the elongation is maximally improved to 11.6%, and increased by 110.9%; the P, mn and Zn composite modification improves the fluidity and the hot cracking performance of the alloy, the average length of a fluidity sample is increased to 445.9mm to the maximum extent, the hot cracking force is reduced to 1433.5N to the minimum extent by 18.8%, the compactness of the casting is improved, the hot cracking resistance of the alloy is improved, the possibility of generating hot cracks of the complex casting is reduced, and the high-fluidity low-hot-cracking cast aluminum alloy is obtained.
Finally, it should be noted that the above-mentioned embodiments are only for illustrating the technical solution of the present invention, and are not limiting; various process schemes without substantial differences from the inventive concept are within the scope of the present invention.
Claims (10)
1. The high-fluidity low-heat-cracking cast aluminum alloy is characterized by comprising the following components in percentage by mass:
6.50 to 7.50 percent of Si, 0.25 to 0.45 percent of Mg, 0.10 to 0.20 percent of Cu, 0.015 to 0.025 percent of P, 0.40 to 0.80 percent of Mn, 0.60 to 0.90 percent of Zn, less than or equal to 0.12 percent of impurity element Fe and the balance of aluminum.
2. The process for preparing a high flow low thermal cracking cast aluminum alloy as defined in claim 1, comprising the steps of:
s1, proportioning: weighing industrial pure aluminum with the purity of 99.9 weight percent, al-21.5 weight percent of Si intermediate alloy, al-50 weight percent of Mg intermediate alloy, al-10 weight percent of Cu intermediate alloy, al-4 weight percent of P intermediate alloy, al-10 weight percent of Mn intermediate alloy and industrial pure zinc with the purity of 99.9 weight percent according to the proportioning amount, and drying to finish the batching;
s2, coating and drying: in order to prevent the aluminum alloy melt from reacting with the tool in the casting process, uniformly coating the coating on the contact surfaces of a graphite clay crucible, a smelting tool and a die, drying the graphite clay crucible in a smelting furnace, polishing the alloy raw material by sand paper to remove a surface oxide layer, and then drying and preheating the alloy raw material in a drying oven at 200-300 ℃;
s3, smelting and casting: sequentially adding Al-Si intermediate alloy and pure aluminum into a graphite clay crucible preheated to 450 ℃, then heating to 750 ℃ along with a furnace, stirring, standing and preserving heat for 20min after all the Al-Si intermediate alloy and the pure aluminum are melted; then adding Al-Cu intermediate alloy, al-Mn intermediate alloy and pure Zn, fully stirring after all melting, and keeping the temperature and standing for 20min; then wrapping Al-Mg intermediate alloy and Al-P intermediate alloy with aluminum foil, rapidly placing into molten alloy liquid, pressing the molten alloy liquid into the bottom of the alloy liquid by using a slag ladle to reduce oxidation burning loss, fully stirring, adjusting the furnace temperature to 750 ℃, and keeping the temperature and standing for 20min;
s4, refining: removing dross on the surface of the alloy melt by a skimming ladle, introducing inert gas after skimming, and adding C 2 C1 6 Turning on the control device, refining the combination by using a graphite rotor and an alternating electromagnetic field, standing and preserving heat for 10-15min, and skimming again; then inert gas is introduced, a deslagging agent is added, a control device is opened, a graphite rotor and an alternating electromagnetic field are utilized for refining, standing and heat preservation are carried out for 10-15min, and deslagging is carried out; then heating the alloy melt to 750 ℃ along with a furnace, standing and preserving heat for 10-15min;
s5, pouring: taking out a metal mould preheated at 200-300 ℃ from a constant-temperature drying oven, pouring the alloy melt obtained in the step S4 into the mould, and cooling to obtain an alloy cast ingot;
s6, solution treatment and artificial aging treatment: and sequentially carrying out solution treatment and artificial aging treatment on the obtained alloy cast ingot.
3. The preparation process according to claim 2, characterized in that:
in the step S2, the chemical components of the coating are formed into Na according to the mass ratio 2 SiO 3 ·9H 2 O：ZnO：H 2 O＝1：4：15。
4. The preparation process according to claim 2, characterized in that:
in step S4, C 2 C1 6 And the adding amount of the deslagging agent is 0.5% of the total alloy, wherein the deslagging agent is formed by compounding NaCl and KCl.
5. The preparation process according to claim 2, characterized in that:
in step S4, the graphite rotor includes a plurality of turntables and a graphite rod connecting shaft, and the turntables are connected with the connecting shaft through threads; the rotary table is of a hollow structure, an axial through hole is formed in the middle of the connecting shaft, and the through hole is communicated with the interior of the rotary table; and a plurality of through holes are formed in the surface of the turntable.
6. The preparation process according to claim 5, characterized in that:
and a plurality of groups of through holes are circumferentially arranged on the surface of the turntable, and each group of through holes comprises a plurality of through holes uniformly distributed along the radial direction at intervals.
7. The preparation process according to claim 2, characterized in that:
in the step S4, the inert gas is one of nitrogen and argon, the rotating speed of the multi-nozzle graphite rotor is 400r/min, and the blowing flow is 7-8L/min.
8. The preparation process according to claim 2, characterized in that:
in the step S4, the frequency of the alternating electromagnetic field is 50kHz, the coil current is 100-130A, and the action time is 10-15min.
9. The preparation process according to claim 2, characterized in that:
in step S6, the solution treatment process is as follows: solid solution heat preservation at 550 ℃ for 5 hours; quenching with water and warm water at 70-80 ℃.
10. The preparation process according to claim 2, characterized in that:
in step S6, the artificial aging process comprises the following steps: aging at 210 ℃ and preserving heat for 3-6h, discharging and air cooling.
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