Explosive Welding of Plasma Chamber Cathodes
Development of Explosive Consolidation Technology for Producing Plasma Chamber Heat Stability Compound Cathodes
Tech Area / Field
3 Approved without Funding
G. Tsulukidze Mining Institute, Georgia, Tbilisi
- HITEC-MATERIALS Dr.Ing Keschtkar GmbH & Co..KG, Germany, Karlsruhe\nKarlsruhe University, Germany, Karlsruhe\nSouth Dakota School of Mines and Technology, USA, SD, Rapid City\nKumamoto University / Shock Wave and Condensed Matter Research Center, Japan, Kumamoto
Project summaryIt is well known that when the electric arc is compressed the temperature of the arc is increased and partially ionized gas jet – plasma flame is formed. Actually the plasma flame can serve for treating any metal and nonmetal material resisting treating by the oxyacetylene torch. Relatively new plasma technology is being widely used (Kjellberg Finsterwalde Elektroden & Masehinen GmbH, Institute of electric welding, St-Petersburg, Russia; Institute of electric welding, Kiev, Ukraine, etc). Basically such technologies are being applied in large industrial enterprises while their complexity and necessity of gas and water external supply hinders the use of these technologies in small enterprises and domestic conditions. Alongside with that, without the gas and water external supply when the arc plasma torch’s (plasmatron's) self-refrigeration is being used the thermal load upon the plasmatron's cathode is increased and its durability reduces. Project's authors solve this problem in the following way: in the fig.1 is shown the traditional plasmatrons' functioning principal.
The plasmatron's main units are anode (1) and cathode (2). The cathode consists of the copper hoop (3) and zirconium or hafnium embedded rod (4). The anode, which is blown by gas, compresses the arc, and the formed plasma flame (6) is directed toward the treated item (7).
The proposed plasmatron (fig.2) consists of the self-blowing mechanism (1), compound long rod cathode (2) and anode (3) also being blown by the self-blowing mechanism (1). The problem is to obtain a good contact with a high thermal conductance between the cathode's long embedded rod (diameters from 1 to 2 mm and length from 40 to 60 mm) and thin copper hoop (wall thickness from 1 to 2 mm and length from 40 to 50 mm). Pre-investigations showed that the lifetime of compound cathodes is significantly greater when they are manufactured using the shock-wave consolidation (explosive welding). The increase of the heat-resistance of long compound cathodes is provided by the formation of a transient zone between the hafnium or zirconium rod and copper hoop. The contacting surface is being formed better when the embedded rod is welded into the hoop by the explosive welding. The applications of the hot explosive compression technology and experiments under heated conditions permit to obtain compound cathodes without any crack and porous with simultaneous formation of the wide transient zone upon the whole length of the cathode. This provides a significant improvement of the cathode's heat-resistance and increase of the lifetime.
The Project's main objective foresees the development and manufacturing of the compound cathode for the plasmatron by means of consolidation and explosive welding. It provides the obtaining of compound cathodes with the improved heat-resistance For achieving this goal the following tasks are to be performed:
1. Calculation of thermal processes in plasmatrons' long compound rod cathodes.
2. Development of explosive welding (joining) technology for embedding coated and non-coated zirconium or hafnium rods into the copper hoop at different temperatures.
3. Investigation of the structure and mechanical properties of the transient zone between the embedded rod and hoop accordingly to treatment parameters.
4. Study of relationship between the structure and thermal-physical properties of compound rod cathodes in accordance with treatment parameters.
5. Development of the test bench for testing plasmatrons' compound cathodes manufactured by means of the explosive welding.
6. Defining of cathodes' technical characteristics and optimal parameters for cathodes manufacturing.
7. Preparation of the technical documentation for the commercial manufacturing of plasmatrons’ compounds cathodes by the explosive welding technology.
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