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CN-121976068-A - Electrophoretic spraying-oriented casting process of excellent-surface-quality regenerated aluminum alloy

CN121976068ACN 121976068 ACN121976068 ACN 121976068ACN-121976068-A

Abstract

The invention relates to the technical field of metal casting and discloses an electrophoresis spraying-oriented casting process of a regenerated aluminum alloy with excellent surface quality, which comprises the steps of melt structuring tempering, melting and refining the regenerated aluminum alloy with the iron content of 0.8-1.2 wt%, adding an aluminum-rare earth-boron intermediate alloy to construct a rare earth-iron atomic cluster with high structural viscosity, shearing, crushing and filling, pressing the melt into a preheated die at high speed by using a vacuum die casting machine, and establishing a temperature not lower than that of the die through an inner pouring gate The invention utilizes the synergistic mechanism of rare earth tackifying-shearing crushing to break through the negative correlation restriction of the high iron content of the secondary aluminum and the excellent surface quality, realizes the spheroidization and dispersion distribution of the surface layer iron-rich phase and reduces the microcosmic corrosion potential difference.

Inventors

  • LIU ZONGYI
  • ZHAO JUNLIN

Assignees

  • 湖南千源铝业有限公司

Dates

Publication Date
20260505
Application Date
20260407

Claims (10)

  1. 1. The casting process of the reclaimed aluminum alloy with excellent surface quality for electrophoretic spraying is characterized by comprising the following steps of: Tempering the melt by structuring, wherein a secondary aluminum alloy with an iron content of 0.8wt% to 1.2wt% is used in the composition To the point of Adding an aluminum-rare earth-boron intermediate alloy into the refined regenerated aluminum alloy melt, controlling the mass percent of rare earth elements in the final regenerated aluminum alloy melt to be 0.08-0.12%, and the mass percent of boron to be 0.005-0.015%, wherein the rare earth elements consist of lanthanum and cerium and the mass ratio of lanthanum to cerium is 1:1.5-1:2.0, and constructing rare earth-iron atom clusters with high structural viscosity in the regenerated aluminum alloy melt by utilizing the adsorption effect of the rare earth elements on iron atoms; shearing, crushing and filling, preheating the surface of the die cavity of the die casting die to the temperature of To the point of The method comprises the steps of pressing a quenched and tempered regenerated aluminum alloy melt into a die casting mold by a vacuum die casting machine, selecting an inner gate with the thickness of 1.5-2.5 mm, controlling the flow speed of the regenerated aluminum alloy melt to be 45-55 m/s when the regenerated aluminum alloy melt flows through the inner gate, and establishing a position not lower than the inner gate through the coupling of the section geometric constraint of the inner gate and a high-speed flow field Using fluid shear stress to forcedly break up rare earth-iron clusters; Quenching and freezing, namely filling the die-casting die cavity with the regenerated aluminum alloy melt in a spray manner, and after the regenerated aluminum alloy melt contacts the surface of the die-casting die cavity for 0.02 to 0.05 seconds, reducing the surface temperature of the regenerated aluminum alloy melt to be below the solidus temperature, and freezing the crushed iron-rich phase on the surface of the casting in a spherical or polygonal particle manner; aging and passivating, namely placing the cast after demoulding The temperature is kept for 1.5 to 2.0 hours at the ambient temperature, and rare earth element atoms supersaturated and solid-dissolved are induced to carry out segregation towards an iron-rich phase interface so as to form a passivation layer.
  2. 2. The casting process of an electrophoretically-sprayed-facing excellent surface quality secondary aluminum alloy according to claim 1, wherein the addition temperature of the aluminum-rare earth-boron master alloy is strictly limited to To the point of Mechanical stirring is needed after the aluminum-rare earth-boron intermediate alloy is added into the regenerated aluminum alloy melt, the stirring rotating speed is set to 150-250 rpm, the stirring time is 8-12 min, and the stirring is kept stand for 15-20 min, so that the rare earth-iron atomic clusters can reach a thermodynamic metastable equilibrium state in the regenerated aluminum alloy melt, and oxidation loss of rare earth elements or excessive aggregation of the rare earth-iron atomic clusters caused by local overheating can be prevented.
  3. 3. The casting process of an electrophoretically-sprayed-oriented excellent surface quality secondary aluminum alloy of claim 1, wherein in the shear crushing and shaping step, the shear rate in the shear rate field is Flow rate from recycled aluminum alloy melt through in-gate And thickness of in-gate Together, and satisfy the following rheological kinetic constraints: , wherein, The unit is m/s for the average flow rate of the regenerated aluminum alloy melt when flowing through the inner gate; The constraint relation ensures that the input shearing energy exceeds the binding energy threshold of the rare earth-iron atom cluster, and the physical disintegration of the rare earth-iron atom cluster is initiated.
  4. 4. The casting process of the reclaimed aluminum alloy with excellent surface quality for electrophoretic spraying according to claim 1, wherein in the shearing, crushing and filling step, a layer of nano ceramic coating is sprayed on the surface of a cavity of the die casting mold in advance, and in the preheating process, the temperature of the surface of a movable mold of the die casting mold is controlled by using a mold temperature engine oil path circulation To the point of The surface temperature of the fixed mold is To the point of 。
  5. 5. The casting process of the reclaimed aluminum alloy with excellent surface quality for electrophoretic spraying according to claim 1, wherein in the melt structuring tempering step, the reclaimed aluminum alloy is ADC12 grade aluminum alloy, the mass percentage of manganese element in the chemical composition is controlled to be between 0.15% and 0.35%, cerium in the rare earth element preferentially occupies the surface sites of rare earth-iron atomic clusters, boron element and rare earth element generate high-melting-point diboride rare earth particles in situ, and the diboride rare earth particles are dispersed in the reclaimed aluminum alloy melt as heterogeneous nucleation cores.
  6. 6. The casting process of the reclaimed aluminum alloy with excellent surface quality for electrophoretic spraying according to claim 1, wherein in the shearing crushing and filling step, the cavity vacuum degree of the vacuum die casting machine in the injection process is maintained within an absolute pressure range of 3kPa to 5kPa, the inner gate adopts a fan-shaped structure, and the ratio of the sectional area to the cross gate sectional area is 1:3 to 1:4, so that stable laminar flow state of the reclaimed aluminum alloy melt is established before entering the inner gate, and rapid rheological conversion from laminar flow to turbulent flow occurs when passing through the inner gate.
  7. 7. The casting process of an electrophoretic spray-oriented excellent surface quality secondary aluminum alloy according to claim 1, wherein in the quenching and freezing step, the casting surface layer means a region of a depth of 0 to 100 μm from the casting outer surface, and wherein in the region, the average equivalent circular diameter of the iron-rich phase is controlled to be 0.5 to 2.0 μm and the aspect ratio is less than 2.0, and the iron-rich phase consists essentially of Phase constitution, and no needle-like structure continuously distributed in the region And (3) phase (C).
  8. 8. The casting process of the reclaimed aluminum alloy with excellent surface quality for electrophoretic spraying according to claim 1, wherein in the aging passivation step, the cast is directly sent into an aging furnace through a conveyer belt after being demolded, and the surface temperature of the cast before being sent into the furnace is not lower than The aging furnace adopts a hot air circulation heating mode, and the heating rate is controlled at To the point of 。
  9. 9. The electrophoretic spray-oriented excellent surface quality secondary aluminum alloy casting process according to claim 1, further comprising a surface pretreatment step performed after the aging passivation step, wherein the surface pretreatment step comprises washing the cast product with a phosphorus-free degreasing agent to perform chromium-free passivation treatment, and wherein the natural corrosion potential of the cast product in the surface pretreatment step is maintained with respect to a standard hydrogen electrode due to the spheroidization of the iron-rich phase of the cast product surface layer and the presence of the passivation layer To the point of And the potential difference between the surface microscopic cathode and the aluminum matrix is smaller than 。
  10. 10. The casting process of the reclaimed aluminum alloy with excellent surface quality for electrophoretic spraying according to claim 1, wherein in the melt structuring tempering step, the aluminum-rare earth-boron intermediate alloy is a prefabricated rod-shaped or block-shaped master alloy prepared by the steps of placing pure aluminum, pure lanthanum, pure cerium and potassium fluoborate in an induction furnace To the point of The aluminum-rare earth-boron intermediate alloy is prepared by smelting and casting, wherein the impurity content of the aluminum-rare earth-boron intermediate alloy is controlled to be less than 0.15 percent, the silicon content is less than 0.10 percent and the calcium content is less than 0.03 percent.

Description

Electrophoretic spraying-oriented casting process of excellent-surface-quality regenerated aluminum alloy Technical Field The invention relates to an electrophoretic spraying-oriented casting process of a reclaimed aluminum alloy with excellent surface quality, and belongs to the technical field of metal casting. Background The current recycling of recycled aluminum alloy die casting production and recycling of recycled aluminum material for preparing structural members to achieve recycling of resources and reducing cost are industry consensus, the requirements of appearance quality of automobile and consumer electronic structural members are met, the surface of a casting is required to be subjected to high corrosion resistance electrophoretic spraying treatment, as the iron content of the recycled aluminum raw material is generally high and the solid solubility of iron in an aluminum matrix is extremely low, the existing mainstream technology mostly adopts a ceramic filter plate to purify melt or adds pure aluminum liquid for dilution, attempts to improve the surface quality of the casting by reducing the total content of bulk impurities, and the component subtraction-based technical path is regarded as a standard mode for solving the surface defects of the recycled aluminum casting for a long time. However, in the face of the inherent quenching segregation working condition of a high-pressure casting process, the main flow path is difficult to overcome the dynamics bottleneck, the surface chilling action of a die cavity in the die casting process builds extremely steep temperature gradient on the outermost layer of a casting, drives solute elements at the front edge of a melt to undergo severe back diffusion, even if the content of bulk iron is controlled to be lower, the thermodynamic driving iron elements are still preferentially enriched towards the liquid phase side and move to the outermost layer of the casting along with the solidification front edge, finally, the needle-shaped beta-AlFeSi phase is separated out in a continuous distribution manner, the needle-shaped phase enriched surface has positive potential difference relative to an alpha-Al matrix, the acid washing or alkali washing step is processed before electrophoresis to form a cathode of a high-density microcosmic primary battery, so that the matrix is subjected to severe local pitting to form macroscopic star-shaped defects, the compactness adhesion of an electrophoretic coating is damaged, in order to cope with the challenge, the industry attempts to introduce manganese-chromium and other elements to undergo chemical modification treatment in an attempt to change the iron phase form, but the conventional modifier diffusion mechanism is limited by the quenching condition, the quenching condition is extremely short in a solidification window, and the phase is difficult to timely finish the phase transformation dynamics process in the chilling layer. Therefore, the technical problem to be solved by the invention is how to break through the restriction of precipitation kinetics of the surface iron phase under the quenching condition on the premise of not greatly increasing the cost of raw materials and realize the homogenization electrochemical passivation of the surface structure of the high-iron-content regenerated aluminum casting. Disclosure of Invention In order to solve the problems in the background technology, the technical scheme of the invention is as follows, an electrophoretic spraying-oriented casting process of the reclaimed aluminum alloy with excellent surface quality comprises the following steps: Tempering the melt by structuring, wherein a secondary aluminum alloy with an iron content of 0.8wt% to 1.2wt% is used in the composition To the point ofAdding an aluminum-rare earth-boron intermediate alloy into the refined regenerated aluminum alloy melt, controlling the mass percent of rare earth elements in the final regenerated aluminum alloy melt to be 0.08-0.12%, and the mass percent of boron to be 0.005-0.015%, wherein the rare earth elements consist of lanthanum and cerium and the mass ratio of lanthanum to cerium is 1:1.5-1:2.0, and constructing rare earth-iron atom clusters with high structural viscosity in the regenerated aluminum alloy melt by utilizing the adsorption effect of the rare earth elements on iron atoms; shearing, crushing and filling, preheating the surface of the die cavity of the die casting die to the temperature of To the point ofThe method comprises the steps of pressing a quenched and tempered regenerated aluminum alloy melt into a die casting mold by a vacuum die casting machine, selecting an inner gate with the thickness of 1.5-2.5 mm, controlling the flow speed of the regenerated aluminum alloy melt to be 45-55 m/s when the regenerated aluminum alloy melt flows through the inner gate, and establishing a position not lower than the inner gate through the coupling of the section geometric constrain