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16 Mar 2011
Gas Diffuser new Idea to remove gas from molten metal in induction furnace

01    02

Gas Diffusers have been developed for 25 years, firstly was introduced to be used in the ladle and launder in steel melting.  Capital Refractory has introduced the new development  to install the GD in the induction furnace since 2004 and registered legally.

Since 2004 the GD have installed in the induction furnace more than 200 units in Europe, America and Asia. The direct and indirect benefits that could obtain from the installation of GD in the induction furnace have improved the quality of molten metal especially in Steel and High Quality Special steel in which they were listed as followed:

                    1)     Temperature Homogenization throughout the furnace,
                    2)     Improve Casting Quality in term of reducing rework of the scrap that has the gas defect,
                    3)     Reduce N2 content,
                    4)     Obtain cleaner molten,
                    5)     Increase Lining Life

Using of Gas diffuser is to purify metals manufactured by usual practice in the manufacture of the iron-Carbon alloys known as steel or high grade steel by induction melting furnace. Gas diffuser provide noble gas through a porous body, the porous body being sufficiently porous to enable a gas flowing through and exit to solid sinter porous barrier (sintered lining) , the porous barrier being sufficiently porous to also enable gas as enter the molten metal bath .

The gas using in the refining operation of molten steel must have the following properties: 
                   1)     The composition of atom of the gas must be such electricity and heat will be readily conducted.
                   2)     The gas must be inert
                   3)     The gas must be insoluble in molten metal

The gases that have all of these properties and composition of atoms are only the noble gas to be found in group VII of the Mendeleef periodic table. The gases in group zero of periodic table are the noble gases helium, neon, argon, krypton and xenon. The uses of Helium or Argon are entirely practical and efficient. Helium and Argon gas has following properties important in Metallurgy.

                  1)     It is excellent conductor of heat
                  2)     It is insoluble in molten metal
                  3)     It is entirely entirely chemically indifferent or inert do not form any compounds, being inert to the iron and oxide.
                  4)     More over helium and argon is easily separated or purified from chemically active gases such as hydrogen or nitrogen.

Molten metal provided by furnace that utilize a gas diffuser promote the purity of a molten material and article cast therefore. By eliminating impurities, slag inclusions, dissolves gases such as hydrogen, oxygen, nitrogen, and other chemically active gases, thereby reducing the strength of the metal the microscope and physical tests. The chemistry is no way different from that of the chemistry of metal produced by usual method; the physical tests show substantial improvement in strength. Furthermore, all fatigue tests made to date show complete absences of stress risers such as dissolve gases. Accordingly steel made under this method be free fissures.

The operation with GD in the induction furnace is safe, easy for both installation and gas connection, economy to operate and installation.

Currently there are 2-3 customers in Thailand have been trying GD. The installation of GD could be placed at the same position of earth leakage and as much as possible to be placed near to the centre of the furnace.  The height of GD will be chosen in order to keep it under bottom of lining.  The gas equipment that customer need to prepare such as Argon Gas Tank, which the industrial grade is acceptable, Gas Pressure Regulator for both in the tank and GD, Flow Rate Regulator.  However, all details of ways to choose right GD to match with the capacity of furnace, installation procedure could be obtained directly from Pine-Pacific who is the authorized agent in Thailand.

By  Phetchai  Tirapornsanti 


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