Method for preparing semi-solid aluminum alloy slurry at high efficiency and low cost

A semi-solid, low-cost technology, applied in the field of related materials, can solve the problems of preparation efficiency and preparation cost limitations, inability to apply large-scale production, limited grain refiners, etc., to inhibit the growth of dendrites and realize online preparation , The effect of improving the production efficiency

Inactive Publication Date: 2015-10-07
CHENGDU YISHENGKE BIOTECH
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Problems solved by technology

This method has relatively large limitations, one is that the suitable grain refiner is extremely limited, and the other is that the preparation process is long and the efficiency is low
[0010] Low superheat casting, also known as (near) liquidus casting, is through low superheat pouring and overall pressurization effect, so that the entire alloy liquid enters a supercooled state at the same time, and realizes simultaneous nucleation and simultaneous growth, but it can only be used For the forming of simple st...
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Abstract

The invention discloses a method for preparing semi-solid aluminum alloy slurry at high efficiency and low cost. The method comprises the following steps: (1) heating an aluminum alloy ingot by adopting various heating methods in the prior art to prepare a low super-heat melt body; keeping the temperature of 36-42DEG C over a liquid phase line to prepare the low super-eat melt body which is uniform and constant in chemical components and has less or no segregation; (2) transferring the low super-heat melt body prepared in the step (1) to a low-temperature resistance furnace, and preserving temperature to ensure that the temperature of the melt body is uniform; (3) pouring the low super-heat melt body which is subjected to heat preservation in the low-temperature resistance furnace in the step (2) to a stirring crucible, putting the stirring crucible to an inner cavity of an electromagnetic stirrer, and beginning to carry out electromagnetic stirring by adopting a bidirectional electromagnetic stirring method to prepare semi-solid slurry. According to the method disclosed by the invention, a novel electromagnetic stirring technology, namely the bidirectional electromagnetic stirring method, for preparing a semi-solid alloy is developed, and large speed difference and inertial impact generated by the movement inertia of the melt body are sufficiently utilized, so that the stirring efficiency is greatly improved, and uniform distribution of a solid phase in the semi-solid aluminum alloy is facilitated.

Technology Topic

Examples

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Example Embodiment

[0034] Example 1:
[0035] A method for preparing semi-solid aluminum alloy slurry with high efficiency and low cost includes the following steps:
[0036] 1) Preparation of low-superheat melt, using various heating methods in the prior art to heat aluminum alloy ingots to prepare low-superheat melt; the temperature is maintained at 36~42℃ above the liquidus, and the chemical composition is uniform and constant. Low-superheated melt with little or no segregation;
[0037] 2) Insulate the prepared low-superheated melt, transfer the low-superheated melt prepared in step 1) to a low-temperature resistance furnace, and keep it warm to make the melt temperature uniform;
[0038] 3) The semi-solid slurry is prepared by the two-way electromagnetic stirring method. The low-superheated melt in the step 2) low-temperature resistance furnace is poured into the stirring crucible, and the stirring crucible is placed in the inner cavity of the electromagnetic stirrer, and the two-way electromagnetic stirring method is adopted Start electromagnetic stirring to prepare semi-solid slurry;
[0039] It mainly includes the following steps:
[0040] 3.1) Before the low superheat melt is poured into the stirring crucible, the stirring crucible is preheated to 360~390℃;
[0041] 3.2) Turn on the stirrer 11-15s before putting the stirring crucible into the inner cavity of the electromagnetic stirrer;
[0042] Electromagnetic stirring frequency: 10~25Hz;
[0043] Electromagnetic stirring power: 15kw;
[0044] The mixing method adopts forward rotation, reverse rotation or alternate operation;
[0045] Stirring reversal time is 3~8s;
[0046] 3.3) Transfer the low-superheated melt insulated in the low-temperature resistance furnace in the step 2) into the stirring crucible, put the stirring crucible into the inner cavity of the electromagnetic stirrer, and immediately detect the melt temperature;
[0047] 3.4) Electromagnetic stirring according to the set stirring mode;
[0048] 4) The temperature is collected in real time during the stirring process, and the stirring time is set at the final stirring temperature. When the melt temperature drops to 11-18°C below the liquidus during the stirring process, the stirring is stopped to obtain a semi-solid alloy slurry.
[0049] Further, in order to better realize the present invention, in the step 3), the stirring intensity is controlled by frequency modulation of the electromagnetic stirrer.
[0050] Further, in order to better realize the present invention, a thermal insulation cotton is placed between the stirring crucible and the inner cavity of the electromagnetic stirrer. The addition of thermal insulation cotton can ensure that part of the melt on the wall of the stirring crucible does not cool down during the electromagnetic stirring process. Fast, thereby improving product quality.
[0051] The function of electromagnetic stirring is to cause the melt to produce strong convection, so that it is at the same temperature or a very small temperature gradient, ensuring that the entire melt enters the supercooled state at the same time, and achieves simultaneous nucleation. In the subsequent growth process of crystal nuclei, affected by the growth resistance of adjacent crystal nuclei, it is impossible (or very rarely) to form developed dendrites, thereby obtaining an ideal spherical crystal grain structure. That is, the role of electromagnetic stirring is to create the dynamic conditions for the nucleation of equiaxed crystals, and it does not directly participate in the nucleation and growth of equiaxed crystals. The preparation of a low superheated melt with uniform, constant chemical composition and small segregation (that is, the temperature is 30-35°C above the liquidus line) can shorten the alloy cooling time, that is, shorten the electromagnetic stirring time, and improve the preparation efficiency of the semi-solid slurry.
[0052] In the process of preparing semi-solid slurry by the two-way electromagnetic stirring method, (a) start the electromagnetic stirring mechanism before the melt is fed into the two-way electromagnetic stirrer, one can promote the nucleation of the alloy melt, thereby shortening the pulping time and improving the pulping Second, it can ensure that the alloy in the center and the inner wall of the barrel is fully stirred, so that the heat flow in the barrel is fully transferred, and the slurry structure in the barrel is uniform, and the branching on the inner wall of the barrel is suppressed due to chilling. Crystal; (b) Place insulation cotton in the inner cavity of the electromagnetic stirrer to ensure that the crucible wall part of the melt will not cool down too quickly during the electromagnetic stirring process; (c) The bidirectional electromagnetic stirring mechanism changes the direction of electromagnetic stirring instantaneously through the steering mechanism , To achieve "forward rotation-reverse rotation-forward rotation" alternate operation, using the inertia of the melt to produce a large speed difference and inertial impact, so that the mixing efficiency is greatly improved.
[0053] The semi-solid slurry prepared by this method has a crystal grain diameter of less than 80 μm, a shape factor of more than 0.75, no typical columnar crystals and dendrites in the structure, and very little liquid entrapment in the crystal grains.
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