CN1746327A - Production of semi-solid aluminium alloy size - Google Patents

Production of semi-solid aluminium alloy size Download PDF

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Publication number
CN1746327A
CN1746327A CN 200510086377 CN200510086377A CN1746327A CN 1746327 A CN1746327 A CN 1746327A CN 200510086377 CN200510086377 CN 200510086377 CN 200510086377 A CN200510086377 A CN 200510086377A CN 1746327 A CN1746327 A CN 1746327A
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Prior art keywords
stirring
melt
semi
crucible
solid
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CN 200510086377
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CN1333100C (en
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唐靖林
冯鹏发
曾大本
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Tsinghua University
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Tsinghua University
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Abstract

The invention provides to produce the semi-solid alloy slurry using the electromagnetic stirring method. First, prepare the low degree of the superheat fusant and keep the temperature of it; then, prepare the semi-solid slurry in the stirring pot; when the temperature is below the liquid line 5-10 Deg C., we can stop the stirring and get the product. The process can give us the uniform solid phase of the semi-solid alloy.

Description

A kind of method for preparing semi-solid aluminium alloy size
Technical field
The present invention relates to the method that a kind of electromagnetic stirring method prepares semi-solid alloy slurry, be suitable for low melting point alloys such as aluminium alloy.
Background technology
Semi-solid alloy slurry is the raw material of semi-solid-state shaping indispensability.The basic demand of semi-solid alloy slurry is the non-dendrite that wherein solid phase is tiny rounding, and consistent size, is evenly distributed.The technology of preparation semi-solid aluminium alloy size and technology have multiple, can realize that still the technology of online quick preparation and technology report are less.
In existing preparation semi-solid alloy slurry technology, mainly be divided into some class methods such as utilizing external force, interpolation nucleating agent, controlled chilling speed, heat tracing and low overheat casting according to preparation principle.The method of utilizing external force mainly is to adopt technology such as various stirrings and ultrasonic broken vibration that melt is produced an external force field, makes the convection current of alloy melt generation intensive, reaches the purpose of crystal grain thinning, inhibition dendritic growth, acquisition non-dendritic structure.The research of these class methods is more, comprise various mechanical mixing methods, electromagnetic stirring method and ultrasonic vibration method etc., but,, still be that problem to be solved is arranged to reach efficiently, to prepare fast problems such as semi-solid alloy slurry for the action effect that how to strengthen external force field.
The method of adding nucleating agent mainly be by in alloy melt, add the powder fining agent and (or) alterant, improve melt the forming core condition and (or) control grain growing mode, to reach the purpose of crystal grain thinning.The subject matter of this method is to be difficult to obtain the ideal spherulitic crystal structure, can't be separately as the preparation method of semi solid slurry; And be difficult to satisfy the coherence request of preparation material in the production scene.
The controlled chilling tachometric method is to promote dendrite to degenerate by the speed of cooling of slowing down melt, reaching the transformation of dendrite to equiax crystal, thereby obtains semi solid slurry.The grain-size that this method obtains is bigger, and the performance of drip molding is difficult to embody the advantage of semi-solid processing, and production efficiency is lower; The same coherence request that is difficult to satisfy the preparation material in the production scene.
Grain refining and to reheat thermal-insulating method be to utilize chemical grain-refining agent to prepare the tiny alloy ingot of crystal grain, ingot reheats solid-liquid two-phase region then, relies on the microstructure Evolution in for some time insulating process to obtain semi solid slurry.This method limitation is bigger, and suitable first grain-refining agent is extremely limited, and second preparation process is longer, and efficient is lower.
The low overheat casting also claims the casting of (closely) liquidus line, is by low overheat cast and entire pressurisation effect, make whole alloy liquid enter supercooled state simultaneously, realize simultaneously forming core and grow up simultaneously, but can only be used for the shaping of simple knot member, and production efficiency is lower.
In addition, the preparation method of semi solid slurry also has spray deposition, distortion mutagenesis activation method, turbulence effect method and various powders metallurgy method (comprising single, double airflow atomizing, the atomizing of high speed rotating tube, the atomizing of electricity-flow mechanics etc.) etc., but all be subjected to the restriction of preparation efficiency and preparation expense, can't large-scale production and application.
Summary of the invention
The present invention is intended to traditional electromagnetic stirring method and prepares on the basis of semi-solid alloy slurry, develops a kind of induction stirring novel process for preparing semi-solid alloy, i.e. the bi-directional electromagnetic stirring means.
A kind of method for preparing semi-solid aluminium alloy size may further comprise the steps:
(1) preparation low overheat melt
So-called low overheat is the superheating temperature of relative conventional cast process, i.e. the liquidus line of a little higher than alloy of melt temperature; Equipment is not had particular requirement, can adopt various heating means of the prior art to prepare the low overheat melt; Temperature remains on above 30~35 ℃ of liquidus line, and it is even, constant to prepare chemical ingredients, the low overheat melt of few (nothing) segregation;
(2) the low overheat melt with preparation is incubated
To the low-temperature resistance stove, insulation for some time, make melt temperature even the low overheat melt transfer of step (1) preparation;
(3) the bi-directional electromagnetic stirring means prepares semi solid slurry
Pour the low overheat melt of insulation in above-mentioned steps (2) the low-temperature resistance stove into stirring crucible, crucible is put into the magnetic stirrer inner chamber, adopt the bi-directional electromagnetic stirring means to begin induction stirring and prepare semi solid slurry; So-called bi-directional electromagnetic stirs, promptly by turning device, make melt in stir chamber according to " just changeing-reverse-just change " mode alternate rotation,
Mainly comprise following four steps:
(3.1) before the low overheat melt is poured stirring crucible into, stirring crucible is preheated to 350~400 ℃; After melt entered stirring crucible like this, the temperature of sidewall of crucible place melt was higher than stirring beginning temperature;
(3.2) 5~10s turn on agitator before crucible is put into the magnetic stirrer inner chamber;
Induction stirring frequency: 5~30Hz;
Induction stirring power: 15kw;
Alr mode can just adopt to be changeed, counter-rotating or alternate run;
Stirring turnaround time is 0~10s;
(3.3) the low overheat melt after the melt treatment (melt temperature is higher than 30~35 ℃ of liquidus lines) is changed in the stirring crucible, crucible is put into the magnetic stirrer inner chamber, and detect melt temperature immediately;
(3.4) carry out induction stirring according to setting alr mode;
This moment, main technologic parameters had: beginning whipping temp (liquidus line above 30~35 ℃), unidirectional churning time (5s), just change-reverse reversing mode (adopt and do not have intermittently commutation), stirring frequency (25~30Hz), stir voltage (maximum allowable voltage under the setting stirring frequency);
(4) in whipping process temperature is gathered in real time, churning time is set with final whipping temp, reduces to below the liquidus line 5~10 ℃ when melt temperature in the whipping process, promptly stops to stir, and obtains semi-solid alloy slurry.
Magnetic stirrer of the present invention is controlled stirring intensity by frequency modulation.
The present invention also can place insulating cotton at the magnetic stirrer inner chamber, to guarantee that sidewall of crucible part melt is unlikely to lower the temperature too fast in the induction stirring process.
The motional inertia that the present invention makes full use of melt produces very big velocity contrast and inertia impact, stirring efficiency is greatly improved, and help the uniform distribution of solid phase in the semi-solid alloy; Test shows, under the little situation of whipping force, can obtain the semi solid slurry of the tiny ring initial crystal tissue that is evenly distributed fast, thereby will become the new technology of rheological molding with the online preparation of semi-solid alloy slurry.
(1) effect of induction stirring is to make melt produce the intensive convection current, thereby is under same temperature or the minimum temperature gradient conditions, guarantees that whole melt enters supercooled state simultaneously, realizes forming core simultaneously.Nucleus is subjected to the influence of adjacent nuclei growth resistance in growth process subsequently, can not (or few) form flourishing dendrite, thereby obtain ideal spheric grain structure.The effect that is induction stirring is a dynamic conditions of creating the equiax crystal forming core, does not participate in the forming core of equiax crystal directly and grows up.Preparation chemical ingredients is even, constant, segregation is little low overheat melt (be temperature more than liquidus line 30~35 ℃) can shorten alloy cooling time, promptly shortens the induction stirring time, improves the preparation efficiency of semi solid slurry.
(2) adopt the bi-directional electromagnetic stirring means to prepare in the semi solid slurry process, (a) before sending into the bi-directional electromagnetic agitator, melt starts induction stirring mechanism, can promote the alloy melt forming core first, thereby shorten the slurrying time, improve slurrying efficient, can guarantee that second the central authorities of barrel and the alloy at inwall place are stirred fully, make that the interior hot-fluid transmission of barrel is abundant, guarantee that the each several part slurry tissues is even in the material letter, suppress the material tube inner wall place and dendrite occurs because of Quench; (b) place insulating cotton at the magnetic stirrer inner chamber, can guarantee not occur in the induction stirring process too fast being as the criterion of sidewall of crucible part melt cooling; (c) the bi-directional electromagnetic stirring mechanism makes the moment transformation of induction stirring direction by turning device, realizes " just changeing-reverse-just change " alternate run, utilizes the motional inertia of melt to produce very big velocity contrast and inertia impact, thereby stirring efficiency is greatly improved.
Major advantage of the present invention is as follows:
(1) electromagnetic agitating technology that pulp preparation efficient is more traditional greatly improves.Because electromagnetic stirring force is closely related with the velocity contrast between magnetic field rotating speed and the melt flow, the magnetic field rotating speed of unidirectional induction stirring and melt flow are in the same way, the velocity contrast of the two is limited, and bi-directional electromagnetic is when stirring, utilize the motional inertia of melt can produce very big velocity contrast and inertia impact, thereby stirring efficiency is greatly improved, help to realize the online preparation of semi-solid alloy slurry.
(2) semi-solid alloy slurry organizes more traditional electromagnetic agitating technology more excellent.Because during the moment commutation of induction stirring direction, can produce very great machinery impact with the motional inertia of melt, can suppress the growth of dendrite in the melt more effectively, and help to make the solid phase particles in the melt to be more evenly distributed, so the semi-solid alloy crystal grain that present method obtains is more tiny, even.
Embodiment
The preparation of embodiment A 356 alloy semi solid slurries
At first, adopt resistance furnace fusing A356 alloy pig, the temperature of A356 alloy melt is 640 ℃ ± 5 ℃, and soaking time is 30 minutes, and is even to guarantee melt temperature; In the melt insulation, stirring crucible is preheated to 400 ℃.Open magnetic stirrer subsequently, open about 10s after, the A356 alloy melt through low temperature insulation is poured into stirring crucible, crucible is put into the magnetic stirrer inner chamber, the beginning induction stirring.The induction stirring processing parameter is as follows: just-instead do not having intermittently two-way stirring, teeming temperature T 0=640 ℃, stirring frequency f=30Hz, output voltage U=220V, unidirectional churning time Δ τ=5s.Whipping process is gathered in real time to slurry temperature, when temperature is reduced to 607~605 ℃, promptly stops to stir.Trial sheet, the whole stirring roughly needs about 65s.
Adopt the semi solid slurry crystal grain diameter of this method preparation can reach below the 100 μ m, shape-dependent constant can reach more than 0.70, no typical column crystal and dentrite in the tissue, the involute liquid phenomenon of crystal grain few (Fig. 1).Fig. 1 is the semi-solid aluminium alloy size crystal grain synoptic diagram that adopts the present invention's preparation, and its tissue and rheological property satisfy the semi-solid processing requirement.

Claims (3)

1, a kind of method for preparing semi-solid aluminium alloy size is characterized in that, this method may further comprise the steps:
(1) preparation low overheat melt;
Adopt various heating means of the prior art to prepare the low overheat melt; Temperature remains on above 30~35 ℃ of liquidus line, and it is even, constant to prepare chemical ingredients, less or the low overheat melt of segregation-free;
(2) the low overheat melt with preparation is incubated
To the low-temperature resistance stove, insulation for some time, make melt temperature even the low overheat melt transfer of step (1) preparation;
(3) the bi-directional electromagnetic stirring means prepares semi solid slurry
Pour the low overheat melt of insulation in above-mentioned steps (2) the low-temperature resistance stove into stirring crucible, crucible is put into the magnetic stirrer inner chamber, adopt the bi-directional electromagnetic stirring means to begin induction stirring and prepare semi solid slurry;
Mainly comprise following four steps:
(3.1) before the low overheat melt is poured stirring crucible into, stirring crucible is preheated to 350~400 ℃;
(3.2) 5~10s turn on agitator before crucible is put into the magnetic stirrer inner chamber;
Induction stirring frequency: 5~30Hz;
Induction stirring power: 15kw;
Alr mode adopts just to be changeed, counter-rotating or alternate run;
Stirring turnaround time is 0~10s;
(3.3) the low overheat melt after the melt treatment is changed in the stirring crucible, crucible is put into the magnetic stirrer inner chamber, and detect melt temperature immediately;
(3.4) carry out induction stirring according to setting alr mode;
(4) in whipping process temperature is gathered in real time, churning time is set with final whipping temp, reduces to below the liquidus line 5~10 ℃ when melt temperature in the whipping process, promptly stops to stir, and obtains semi-solid alloy slurry.
2, a kind of method for preparing semi-solid aluminium alloy size according to claim 1 is characterized in that, controls stirring intensity by magnetic stirrer frequency modulation.
3, a kind of method for preparing semi-solid aluminium alloy size according to claim 1 is characterized in that, its magnetic stirrer inner chamber is placed with insulating cotton.
CNB2005100863774A 2005-09-09 2005-09-09 Production of semi-solid aluminium alloy size Expired - Fee Related CN1333100C (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100413985C (en) * 2006-06-08 2008-08-27 北京交通大学 QTi3.5-10 graphite semi-solid size mechanical stirring producing method
CN102181687A (en) * 2011-04-10 2011-09-14 北京交通大学 Mechanical uniform dispersion method of QTi3.5-10 graphite semi-solid slurry
CN102181689A (en) * 2011-04-10 2011-09-14 北京交通大学 Mechanical uniform dispersion method of aluminum 6.5 copper-9 graphite semi-solid slurry
CN102181683A (en) * 2011-04-10 2011-09-14 北京交通大学 Uniform dispersion method of graphite granules in aluminum 6.5 copper-9 graphite semi-solid slurry
CN110508760A (en) * 2019-10-10 2019-11-29 天津东义镁制品股份有限公司 A kind of preparation method and its process flow of non-dendritic structure semi-solid magnesium alloy

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1269978C (en) * 2004-07-01 2006-08-16 北京科技大学 Preparation method for semisolid metal and alloy pulp or blank

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100413985C (en) * 2006-06-08 2008-08-27 北京交通大学 QTi3.5-10 graphite semi-solid size mechanical stirring producing method
CN102181687A (en) * 2011-04-10 2011-09-14 北京交通大学 Mechanical uniform dispersion method of QTi3.5-10 graphite semi-solid slurry
CN102181689A (en) * 2011-04-10 2011-09-14 北京交通大学 Mechanical uniform dispersion method of aluminum 6.5 copper-9 graphite semi-solid slurry
CN102181683A (en) * 2011-04-10 2011-09-14 北京交通大学 Uniform dispersion method of graphite granules in aluminum 6.5 copper-9 graphite semi-solid slurry
CN110508760A (en) * 2019-10-10 2019-11-29 天津东义镁制品股份有限公司 A kind of preparation method and its process flow of non-dendritic structure semi-solid magnesium alloy

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