CN102980415A - Method for driving periodic flow of metal melt on basis of spiral magnetic field of electrified coil - Google Patents

Abstract

The invention relates to a method for driving the periodic flow of a metal melt on the basis of a spiral magnetic field of an electrified coil, belonging to the technical field of metallurgical industry. The method comprises the following steps of: manufacturing a spiral magnetic field body which is formed by coaxially assembling a first group of coilers and a second group of coils in an overlaying manner in the space first, putting the metal melt in a cavity of the spiral magnetic field body, and enabling the spiral magnetic field body to rotate and the rotation directions to alternately change by a period p (=1/fm) to drive the metal melt to flow in a three-dimensional periodic spiral manner. The spiral magnetic field formed by using the method has the advantages of changing the distribution pattern of the magnetic field in the space and time, effectively enhancing and improving the flux redistribution process when the metal melt solidifies and ensuring that the solid and liquid solidifying interface carries out effective convection with a further flux so as to enable the flux to be sufficiently mixed. The method disclosed by the invention has the advantages of effectively reducing various defects in the solidifying process, increasing the temperature evenness, promoting the redistribution process of the flux and improving a metal solidification process and is suitable for different shapes of metal melts.

Description

Drive the method that metal bath periodically flows based on the hot-wire coil helical magnetic field

Technical field

The present invention relates to a kind of method that periodically flows based on hot-wire coil helical magnetic field driving metal bath, belong to technical field of metallurgy industry.

Background technology

It is important research direction of Electro-Magnetic Metallurgy that the way control molten metal of employing electromagnetism flows, technology such as electromagnetic agitation, electromagnetic braking.

At present, adopt the three-phase alternating current electric coil and can realize the magnetic field forms of motion such as row ripple, rotation, helical magnetic field, wherein helical magnetic field can be realized by the stack of row ripple and rotating excitation field.Be identical on the principle of above-mentioned field drives metal bath: molten metal self inner can produce induced-current, induced-current and magnetic field interaction and then generation electromagnetic body force-Lorentz force in moving magnetic field.Lorentz force because have electromagnetic equipment and conductor fluid non-ly directly to contact, show as body force, certain length of penetration arranged in conductor fluid, plurality of advantages the is widely used in metal solidification texture control such as force density is large and environmental pollution is less, metal fluid transport, in the remarkable heat of conductor fluid, the matter transmission.

Electromagnetic agitation has obvious effect to the microsegregation that improves metal solidification process, and this is tested by the great many of experiments chamber and industrial practice confirms, for example grain refinement technology.But the research to concentration segregation (or claiming the composition segregation) is not very deep.In general, owing to apply travelling-magnetic-field, rotating excitation field or helical magnetic field, the electromagnetic force forms of motion that acts on the metal freezing forward position is fixed, molten matter precipitation process can carry out with a kind of fixed mode, make the precipitation process temporal evolution of the molten matter of solidification front very little, molten matter is separated out with a kind of relatively-stationary form, applies magnetic field and not only can not improve the concentration segregation, and increase in addition the trend of concentration segregation.

Publication number is in the Chinese patent application of CN201558682U, a kind of multimode magnetic filed electromagnetic stirrer is disclosed, its principle is: the coil groups I(1 of the rotating excitation field of generation) with the coil groups II(2 that produces travelling-magnetic-field) through the rational composite design in space together, make rotating excitation field and travelling-magnetic-field produce synergistic effect in the space, form helical magnetic field.The combination of coil as shown in Figure 1, coil comprises the coil groups I(1 of vertical sleeve on iron core) and alternate horizontal circle be embedded in coil groups II(2 in iron core and the core teeth groove).Coil I(is as shown in Figure 1a) comprise winding A, B, C, D, E, F, wherein winding A, D series connection is a phase coil, and B, E series connection is a phase coil, and C, F series connection is that three Same Name of Ends of a phase coil are linked to be asterism, three-phase coil leads to the positive alternating current of three-phase, and the frequency of the positive alternating current of three-phase is f _RForm rotating excitation field in its heart section, drive the molten metal (3) that is positioned at its heart section and flow; Coil II(is shown in Fig. 1 b) comprise winding a, b, c, d, e, f, wherein winding a, d series connection is a phase coil, and b, e series connection is a phase coil, and c, f series connection is that three Same Name of Ends of a phase coil are linked to be asterism, three-phase coil leads to the positive alternating current of three-phase, and the frequency of the positive alternating current of three-phase is f _T, form travelling-magnetic-field in its heart section, drive the molten metal (3) that is positioned at its heart section and flow.Its shortcoming is: calutron although it is so can be realized rotating excitation field, travelling-magnetic-field, helical magnetic field, but the electromagnetic force that produces drives molten metal to flow when reaching stable state at molten metal, the flow field is temporal evolution not, be that flow pattern does not change, cause the aforesaid metallurgy that improves to solidify concentration segregation poor effect, sometimes even increase the weight of the concentration segregation.

Summary of the invention

The objective of the invention is to propose a kind of method that periodically flows based on hot-wire coil helical magnetic field driving metal bath, step mode to prior art improves, with periodically variable mode parameter helical magnetic field, the driving of special exercise form, stirring or dispersed metal melt and second-phase thereof, to reach the various defectives in the control metal solidification process, improve the purpose of metal freezing technique.

What the present invention proposed drives the method that metal bath periodically flows based on the hot-wire coil helical magnetic field, may further comprise the steps:

(1) helical magnetic field body of preparation, this helical magnetic field body is assembled at the space Coaxial Superimposed by first group of coil and second group of coil; Described first group of coil vertical sleeve is on iron core, first group of coil comprises winding A, B, C, D, E and F, wherein winding A, D series connection is a phase coil, B, E series connection is a phase coil, C, F series connection is a phase coil, the Same Name of Ends of three-phase coil is linked to be asterism, makes three-phase coil connect the positive alternating current of three-phase, and the frequency of the positive alternating current of three-phase is f _R, form rotating excitation field in the heart section of first group of three-phase coil; Described second group of alternate horizontal circle of coil is embedded in the core teeth groove of iron core, second group of coil comprises winding a, b, c, d, e and f, wherein winding a, d series connection is a phase coil, b, e series connection is a phase coil, c, f series connection is a phase coil, the Same Name of Ends of three-phase coil is linked to be asterism, makes three-phase coil connect the positive alternating current of three-phase, and the frequency of the positive alternating current of three-phase is f _T, forming travelling-magnetic-field in the heart section of second group of three-phase coil, described rotating excitation field and described travelling-magnetic-field form helical magnetic field at the space Coaxial Superimposed;

(2) metal bath is placed in the cavity of helical magnetic field body, the helical magnetic field body is rotated with angular velocity omega, and make direction of rotation with period p (=1/f _m) alternately change, drive metal bath and form the three-dimensional periodic helical flow.

What the present invention proposed drives the method that metal bath periodically flows based on the hot-wire coil helical magnetic field, has following characteristics and advantage:

(1) helical magnetic field of the inventive method formation, changed the distributional pattern in magnetic field at room and time, effectively tighten and improve the molten matter redistribution process of metal bath when solidifying, make place, solid, liquid freezing interface and molten matter far away carry out effectively convection current, molten matter is fully mixed.Under suitable commutating frequency, especially can improve the concentration segregation that capable ripple, rotation or helical magnetic field by single form can not improve even increase the weight of, comprise the tunnel type segregation.

When (2) the inventive method can obtain grand, microsegregation to solidification of metal melt, can also improve the microstructure of metal comprehensively.

(3) the inventive method has been strengthened the heat transmission of metal bath effectively, and forced convection periodic, spatial variations can make the Temperature Distribution in magnetic fields zone more even.These characteristics and advantage make the inventive method can effectively reduce the various defectives of solidifying, and can be used for increasing the uniformity of temperature, promote the redistribution process of molten matter, improve metal freezing technique.The inventive method is applicable to the shape of different metal baths.

Description of drawings

Fig. 1 is the structural representation of helical magnetic field body.

Fig. 2 is the basic principle schematic of helical magnetic field (A represents by magnetic vector potential) direction of motion commutation (π phase shift).

Fig. 3 is waveform (square wave) schematic diagram to mode function that helical magnetic field applies.

Fig. 4 is the schematic diagram of metal bath periodicity Three-dimensional Flow when helical magnetic field body shown in Figure 1 is applied the periodically variable driving force of direction.

Among Fig. 1 and Fig. 4, the 1st, first group of coil of generation rotating excitation field, the 2nd, second group of coil groups of generation travelling-magnetic-field, the 3rd, metal bath.

The specific embodiment

What the present invention proposed drives the method that metal bath periodically flows based on the hot-wire coil helical magnetic field, may further comprise the steps:

(1) preparation helical magnetic field body, its structure as shown in Figure 1, wherein Fig. 1 (a) is helical magnetic field body top view.Fig. 1 (b) is the front view of helical magnetic field body.This helical magnetic field body is assembled at the space Coaxial Superimposed by first group of coil 1 and second group of coil 2.First group of coil 1 vertical sleeve is on iron core, first group of coil comprises winding A, B, C, D, E and F, wherein winding A, D series connection is a phase coil, B, E series connection is a phase coil, C, F series connection is a phase coil, the Same Name of Ends of three-phase coil is linked to be asterism, makes three-phase coil connect the positive alternating current of three-phase, and the frequency of the positive alternating current of three-phase is f _R, form rotating excitation field in the heart section of first group of three-phase coil.Second group of coil 2 alternate horizontal circle is embedded in the core teeth groove of iron core, second group of coil comprises winding a, b, c, d, e and f, wherein winding a, d series connection is a phase coil, b, e series connection is a phase coil, c, f series connection is a phase coil, the Same Name of Ends of three-phase coil is linked to be asterism, makes three-phase coil connect the positive alternating current of three-phase, and the frequency of the positive alternating current of three-phase is f _T, forming travelling-magnetic-field in the heart section of second group of three-phase coil, described rotating excitation field and described travelling-magnetic-field form helical magnetic field at the space Coaxial Superimposed;

(2) metal bath 3 is placed in the cavity of helical magnetic field body, the helical magnetic field body is rotated with angular velocity omega, and make direction of rotation with period p (=1/f _m) alternately change, drive metal bath and form the three-dimensional periodic helical flow.

As shown in Figure 1, according to prior art, by first group of coil, 1 logical three-phase alternating current electric forming rotating excitation field; By second group of coil, 2 logical three-phase alternating current electric forming travelling-magnetic-fields, and polyphase winding arranges that along cylindrical surface the Coaxial Superimposed in the space forms helical magnetic field by rotating excitation field and travelling-magnetic-field; Make metal bath be positioned at the cavity of helical magnetic field body, the capable ripple and the rotating excitation field that form helical magnetic field are worked under same frequency, realize counter motion for making helical magnetic field, can realize by the principle identical with motor forward and backward control, get final product exchanging in any two-phase of synchronization in the phase sequence of travelling-magnetic-field and rotating excitation field.Normally V is mutually constant, and the U phase is exchanged mutually with W.Result of implementation transfers to the direction of motion of helical magnetic field on the contrary like this.Fig. 2 illustrates this commutation process, represents the magnetic vector potential of helical magnetic field with A, and the phase shift of implementing π can realize the operation of Movement in Magnetic Field opposite direction.Can be with the periodization of above-mentioned helical magnetic field switch operation by existing electrical process technology, namely the direction of motion of helical magnetic field is with cycle P (=1/f _m) alternately change f wherein _mBe commutating frequency.The forward and reverse time in common above-mentioned periodically variable each cycle is identical, as shown in Figure 3.Under such magnetic fields, the metal bath that drives forms the three-dimensional periodic helical flow, shown in Fig. 4 c and Fig. 4 d.If front half periodic table in each cycle is shown Fig. 4 c or Fig. 4 d, then rear half period can be expressed as Fig. 4 d or Fig. 4 c.The periodically variable function of above-mentioned expression direction (square wave) can be expressed as:

$m\left(t\right)=\frac{4}{\mathrm{\π}}\underset{n=1}{\overset{\∞}{\mathrm{\Σ}}}\frac{\sin [2\mathrm{\π}(2n-1)\·f_m\·t]}{2n-1}.$

Wherein: t is the time, and n is natural number.And commutating frequency f _mWith f _R, f _TSatisfy following relation:

f _m＜＜f _R，f _m＜＜f _T

Be relative f _RAnd f _T, be to order of magnitude when young.

In conjunction with Electro-Magnetic Metallurgy practice, can effectively intervene the three biography processes (heat transfer, mass transfer and MOMENTUM TRANSMISSION) of alloy graining for making electromagnetic force, the setting of frequency and Metal Melting matter are relevant in the convection current in solid-liquid interface forward position and the time scale separated out.Solidify spaced features around the time when what cycle of the forced convection of frequency drives and molten matter were separated out, the periodicity that helical magnetic field drives flows just can effectively disperse the molten matter separated out from liquid phase, thus more effective concentration segregation that improves in the metal solidification process.According to the above, frequency f _mRange of choice can be between 0.02 hertz to 1 hertz.

Claims (1)

1. one kind drives the method that metal bath periodically flows based on the hot-wire coil helical magnetic field, and the method may further comprise the steps:

(1) helical magnetic field body of preparation, this helical magnetic field body is assembled at the space Coaxial Superimposed by first group of coil and second group of coil; Described first group of coil vertical sleeve is on iron core, first group of coil comprises winding A, B, C, D, E and F, wherein winding A, D series connection is a phase coil, B, E series connection is a phase coil, C, F series connection is a phase coil, the Same Name of Ends of three-phase coil is linked to be asterism, makes three-phase coil connect the positive alternating current of three-phase, and the frequency of the positive alternating current of three-phase is f _R, form rotating excitation field in the heart section of first group of three-phase coil; Described second group of alternate horizontal circle of coil is embedded in the core teeth groove of iron core, second group of coil comprises winding a, b, c, d, e and f, wherein winding a, d series connection is a phase coil, b, e series connection is a phase coil, c, f series connection is a phase coil, the Same Name of Ends of three-phase coil is linked to be asterism, makes three-phase coil connect the positive alternating current of three-phase, and the frequency of the positive alternating current of three-phase is f _T, forming travelling-magnetic-field in the heart section of second group of three-phase coil, described rotating excitation field and described travelling-magnetic-field form helical magnetic field at the space Coaxial Superimposed;

(2) metal bath is placed in the cavity of helical magnetic field body, the helical magnetic field body is rotated with angular velocity omega, and make direction of rotation with period p (=1/f _m) alternately change, drive metal bath and form the three-dimensional periodic helical flow.

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