400-002-0311 0311-88705580
石家庄爱迪尔电气有限公司
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Shijiazhuang Idea electric co., LTD

Tel:400-002-0311 0311-88705580
Fax:0311-88705583
Phone:13932124930
Email:idea.zhang@ideadq.com
Websitehttp://www.ideadq.com
Address:No.2 of FuKang Road,NanWei Village,Yuhua District, Shijiazhuang City,Heibei Province,China.

Electromagnetic stirring

Semi-solid electromagnetic stirrer

1.summary of the Semi-solid electromagnetic stirrer

Since 1971, D.B.Spencer and M.C.Flemingsthe who were from united States at the Massachusetts institute of technology, has created a new process of stir casting (stir cast), since to use the rotating double bucket mechanical mixing method produce the Srr15%pb rheological slurry, semi-solid metal (SSM) casting technology has experienced more than 20 years of research and development. Stir casting preparation of alloy commonly referred to as non dendritic structure or partially solidified casting alloys. Because adopting this technology’s product has the characteristics of high quality, high performance and high alloying, so it is of strong vitality. In addition to the application of military equipment, began mainly used for the key components of automotive, for example, for the automobile wheel hub, can improve performance, reduce weight, reduce scrap rate. Since then, gradually been used in other areas, produce the high-performance and near net shape parts. The molding machinery of semi-solid metal casting process has introduced. At present has developed to produce the semi-solid casting die casting machine from 600 tons to 2000 tons, forming parts can reach more than 7 kg in weight. At present, in the United States and Europe, the application of the technology is more widely. Semi-solid metal casting process is considered to be one of the most promising near net shape and a new materials preparation technology in the 21st century.

2.Technical principle

  In the ordinary course of casting, primary crystal grew up in dendritic manner, when solid rate around 0.2, dendritic crystal to form a continuous network skeleton, loss the macro liquidity. If get strong stirring when the liquid metal from liquid phase to solid phase in the process of cooling, make the casting is easy to form the branch crystal network skeleton in normal be broken and retains the dispersed particle morphology, suspended in the surplus liquid phase. This kind of granular non-dendrite microstructural, in steady rheological aspect in 0.5-0.6 still has certain rheology, which can use conventional forming process, such as die casting, extrusion, forging and metal forming.
 
3.Semi-solid die casting technology and product advantages
Technics predominance
1Without any grain refining agent can obtain fine grain structure, eliminates the traditional rough casting of columnar crystals and dendrites.
2Forming temperature is low (Such as aluminum alloy can reduce more than 1200 ), can save energy.
3Die longevity is longer. Solid and low temperature of semi-solid slurry forming shear stress, is smaller than traditional dendrite size three orders of magnitude, therefore, smooth filling, heat load is small, thermal fatigue strength degradation.
4Reduce pollution and unsafe factors. When working it get rid of the high temperature liquid metal environment.
5Resistance to deformation is small, use smaller force can achieve homogeneous processing, forming the difficult-to-machine materials is easily.
6Solidification speed faster, productivity higher, the process cycle shorter.
7Suitable for using computer aided design and manufacturing, enhance the automation of the production.
4.product superiority
1A high quality. Due to the grain refinement, microstructure Distribution Homogenize, reduce body contraction, cracking tendency to decline, eliminated shrinkage tendency on the base, mechanical properties increase significantly.
2Closed narrowing of solidification, so the molding body size precision is high, machining allowance is small, near-net forming.
3Forming alloy is wide. Nonferrous alloy are aluminum, magnesium, zinc, tin, copper, nickel base alloy; Iron base alloys such as stainless steel, low alloy steel.
4Manufacture of metal matrix composite materials.  Use high viscosity of semi-solid metal, make the density difference, small solid solubility of metal alloys, also can effectively make mixing different materials, making a new composite materials.

4.Look into the distance

Although the semisolid continuous casting technology haven't reached the level of large-scale industrial applications, but in the existing experiment research and small-scale production has showed a strong vitality. Comprehensive domestic and foreign relevant research it is not hard to see, semi-solid casting technology will has a bright application prospect in the following areas:
(1) High alloy and difficult deformation materials’ forming
High alloy and difficult deformation materials’ forming has always been a difficult problem in the field of material in processing. The semisolid continuous casting billet in the semi-solid temperature has similar to liquid molding directly forming’s advantage, for high alloy materials’ no segregation, no defects casting and the difficult deformation’s material’s forming find a feasible technical route. This research study, usually think which not for forging like white iron, high manganese steel, after made of semi-solid casting billet, in the semi-solid temperature can smoothly forming wall thickness 2 mm, length is 100 mm or more complex parts. Therefore, materials forming semi-solid casting in difficult deformation with the billet production have a brilliant future.
(2)The develop of new generation of iron and steel materials
Now all countries in the world is in super steel research, our country also has significant foundation program start” a new generation of iron and steel materials research”. A new generation of iron and steel materials requires high clean, ultrafine, ultra-high strength, at the same time also has the potential of large-scale application. To achieve this goal, Will need to use continuous casting technology has been using, while the existing continuous casting billet is common area of the columnar crystal, macrosegregation defects seriously, semi-solid casting billet grain size is small, macrosegregation advantage will no doubt be less for a new generation of iron and steel material blocking a worth exploring the technical route.
(3) Composite mat and molding
Composite materials science is a rookie, yet so far, the preparation of composite materials. The semisolid continuous casting in solving this problem will go a long way, it has been many test by a great number of experimental study.
   In a word, the semisolid continuous casting technology in high alloy material, difficult deformation, fine crystal homogenization steel material and new material of high bonus attached molding has unique technical advantages.

 

5.Electromagnetic stirring method
1 The principle of electromagnetic stirrer
   The basic structure of an electromagnetic stirrer in terms of ac induction method, is actually a can stimulate the magnetic field sensor, It likely imitation in the motor stator, crystallizer is equal to the rotor. The effects of the magnetic field sensors in molten metal which produced by molten steel in mold, and relative movement with metal, liquid metal and a conductive body, so, among them also produce feelings should be current, the current interact with sensor produced by the magnetic field generated by electromagnetic force, push the metal liquid movement. The way of movement determined by the magnetic field way movement, at present, widespread application of magnetic field are rotating magnetic field and travelling wave magnetic field.
   Electromagnetic stirring method is the use of electromagnetic inductions effect make the precipitate dentrite broken into granule, belong to the contactless stirring. So, metal molten is pure, not involved in gas, easy to control, high yield, is one of the main methods of industrial applications currently. This method applies to the high melting point alloy. Now, the dominant in the industrial production is electromagnetic stirring technology which called MHD (Magnetohydrofynamic), used in the production of continuous rheological ingot, including aluminum alloy ingots of a diameter of 50-110 mm.
2The effect of stirring
 To adopt advanced technology of electromagnetic stirring, through a large number of experiments at home and abroad and industrial manufacture through the use of electromagnetic stirring achieved the major results:
Reduce the slag content;
Reduce the center shrinkage cavity;
Eliminate macrosegregation;
Increase the equiaxial crystal ratio;
Improve solidification organization, etc.
6Semi-solid experimental electromagnetic stirrer
1working principle
Electromagnetic stirring method using electromagnetic induction in half frozen produce induced current in the metal, induced current under the action of the plus a magnetic field make the metal solid liquid slurry strongly agitation, make traditional dendritic structure turn into non-dendrites mixing organization.
2system composition
This system make up with high-performance 16 bit single chip microcomputer as the core system of AC-DC-AC frequency conversion power supply, electromagnetic sensors, operational control interface, cooling system, etc.
3system advantage
In order to convenient laboratory research, the semi-solid metal in the sensors stress relations with dendrite. This system adopted voltage, frequency, stirring time continuous adjustable, make the semi-solid metal stress condition be clear at a glance. Simple operation control interface, man-machine interface simple and clear, all operations on the control panel can be finished immediately.
4main technical parameters
Our company can customize equipment according to user requirements.
 
5)System overview:
1、The system adopts IPM Intelligent power module as the core component, Itself has short circuit, over-current, under voltage protection function, in the design of system add a reliable snubber circuit and other anti-interference circuit.
2、Adopts industrial-grade single-chip computer as core control, it can be adapted to the harsh industrial field, accurate data acquisition, and processing speed is fast.
3、Switch, contactor, rectifier, filter, buffer circuits and other electronic devices, all choose reliable devices, in design choose the larger pressure, flow coefficient, thermal protection.
4、In the structure design and manufacturing try to reduce the distributed capacitance, inductance and resistance to radiation, induction and coupling interference ability.
5、Parameters and program design closely, system logic inputs and downtime, can better prevent the error operation and outage system damage caused by the accident.
6) Basic functions:
1、There is the input voltage, output current dial indicator, working frequency, working voltage digital indicator.
2、Current and frequency in stepless adjustment setting work scope.
3、System in the mixing state can change work by adjusting the voltage current.
4、There are three kinds of mixing way mixed ,stirred and automatic mixed, Under any stirring conditions mixing time, stop time, stop time in phase can be arbitrarily set in the parameter scope.
5、Fault indicator is divided into three type, that are system outage, mixing stop fault, and the alarm fault.
A、System outage: Including the cooling fan not work, the IPM module failure, rectifier fuse failure, main contactor faults, control of power failure, etc.
B、Mixing stop failures: Including a serious shortage of water, blender winding serious overheating, cooling fan stopped.
C、The alarm fault: Including water, water pressure is insufficient, over current, under voltage, three-phase current unbalance, etc.
 
7) Installation considerations
1、The power supply into line should strictly guarantee the wiring is correct, otherwise it can't work normally.
2、The connecting cable specification must conform to the requirements for the manufacturer.
3、In all parts of the whole equipment shell shall be reliable grounding, in case of interference.
4、All lines to ensure that the insulation is good.
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