Vacuum Levitation Melting Technology

Vacuum Levitation Melting Technology

  Vacuum levitation melting technology uses the electromagnetic force to levitate the liquid metal pool or cause quasi-levitation, which adopts electromagnetic induction heating power supply and melts the material
under the vacuum or inert gas atmosphere.
  Levitation Melting is known as the most advanced melting technology in the world, its
advancement is reflected in two aspects: first, it eliminates the gas and crucible contamination to the
melt with vacuum technology, due to this characteristic, levitation melting technology has important
significance to produce and research the active metals and alloys, high purity and super pure metals
and alloys, as well as the complex alloys and intermetallic compound,etc; Second, it gets rid of the
limitation on melting temperature from crucible material——most ceramic crucibles are unable to
endure the high temperature above 2000 ℃. So the levitation melting technology has important
significance to research and develop refractory metals and alloys, compounds and ceramic material,
etc
  Levitation Melting Technology includes two kinds: Complete levitation melting technology and
Cold crucible induction melting technology.
Complete Levitation Melting Technology does not use crucible, the involved high frequency
power output of sensor consists of levitation coils and above stable rewind coils, and the liquid
metal pool is levitating in the coils during melting (Fig.1).Although the effect of complete levitation
melting is ideal, its melting capacity is a few grams which only applicable to small-scale laboratory
test.
  Cold crucible induction melting technology is developed on the basis of vacuum induction
melting, uses the segmented water-cooled cold copper crucible and supersonic frequency power, the
electromagnetic field passes through the cold crucible to produce the induced eddy current, the eddy
current heats and melts the metal charge, meanwhile, the eddy current interacts with magnetic line
of force so that produces the Lorentz force which supports and levitates the liquid metal pool or
causes the quasi-levitation. Fig.2 shows the core part of this technology. Fig.3 shows the hump
shaped levitation liquid metal pool in the cold crucible.

Using Cold Curcible Induction Melting for Functional Materials and Metal Single Crystal

Cold Crucible Induction Melting technology has significant importance to the development of Function materials and Metal single crystal. Below reviews the main developments in China.

  Since 1988,Bei Li started to produce the rare earth giant magnetostrictive alloy TbDyFe2 by cold crucible induction melting technology on the production scale, gained 2 authorized patents respectively in 2002 and 2005 [1,2]. In 2007, Zeng-Lin Zhou, et al [3] reported that they melted the A2B7 model La - Mg - Ni base hydrogen storage alloy by using the cold crucible induction melting technology. 

  Domestic development of Czochralski metal single crystal growth by using cold crucible induction Melting equipment includes: 
  In 1987,Da-Liang Sun,et al [4] for the first time in the world grew the large size Nd2Fe14B single crystal. 
  In 2000, Qiang Li,et al[5],grew the < 112 > oriented Φ 15 x 200 mm Tb0.27 Dy0.73 Fe2 single crystal. Guang-Heng Wu,et al[6] grew the < 111 > oriented Tb0.27 Dy0.73 Fe2 single crystal.
  About NiMnGa series Heusler alloy, Jing-Lan Chen,et al[7] grew the Ni52Mn24Ga24 single crystal in 2000. Liang Wu,et al[8] grew the [001] oriented Ni46Mn35Ga19 single crystal in 2009, and the increase rate of transformation strain for the magnetic enhancement reached 1.90%. 
  Regarding the β phrase Ni - Al high temperature shape memory alloy, Feng-Bing Song, et al[9] have done lots of researches on single crystal growth and composition control of Ni - Al alloy in 2001,etc.

 Shenzhen Summit Levitation Metallurgical S&T Co.,Ltd is a sole Chinese hi-tech enterprise specializing in researching and developing levitation metallurgical technology with emphasis on cold crucible induction melting technology,it have developed two series of cold crucible induction melting equipment which including Standard type and Special type to meet different users' requirement. 

Reference:

[1] Bei Li, ZL01274217.1, Cold crucible vacuum melting equipment with multifunctional operating system, 2002

[2] Bei Li, ZL02110945.1, Directional solidification method of producing the TbDyFe base alloy, 2005

[3] Zeng-Lin Zhou, Yue-Qing Song, Shun Cui, et al, Effect of replacing the Nb by La on La - Mg - Ni A2B7 type hydrogen storage electrode property [J], Journal of Nonferrous Metals, 2007, 17 (1) : 45-52.

[4] Da-Liang Sun, Min-Hua Jiang, Huan-Chu Chen,et al, New magnetic Nd2Fe14B single crystal Production by utilizing cold crucible technology [J]. Journal of Science, 1987, 14:1071-1073

[5] Yi-Ling Zhang, Qiang Li,et al, Research of crystal growth by utilizing cold crucible, Journal of Material Science and Engineering 2000( z1)

[6] Guang-Heng Wu,et al <111> Oriented and twin-free single crystals of Terfenol-D grown by Czochralski 

method with cold crucible. Progress in Natural Science, 1995, 5(6): 115-119. 

[7] Jing-Lan Chen, et al, Institute of physics, Chinese academy of sciences, Single crystal growth and phase transition properties of Heusler alloy Ni52Mn24Ga24 single [J]. Journal of Artificial Crystal, 2000, S1:25.

[8] Liang Wu,et al, Physical characterization and Shape memory effect of the Martensitic transformation and metamagnetic transition in the single crystal Ni46Mn35Ga19 [J]. Journal of Chongqing Normal University, 2009, 26 (4) : 94-97

[9] Feng-Bing Song, Qiang Li, Yi-Ling Zhang, et al, Research of the production of Martensite NiAl alloy by Czochralski method [J]. Journal of Wuhan University, 2001, 23 (6) : 14-17.

Hannah Zhang(Ms.)

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Shenzhen Summit Levitation Metallurgical S&T Co., Ltd
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