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JOINING OF POWDER DETAILS BY MEANS OF PULSED ELECTROMAGNETIC FIELD Victor Mironov, Irina Boyko Riga Technical University, Riga, Latvia Lappeenranta, Finland, 21-24 August, 2007 Contents 1. Introduction 2. Theoretical background 3. Pulsed electromagnetic field 4. Equipments 5. MIOM application in PM 6. MIOM for production of composite materials 7. MIOM assembling 8. Conclusion Introduction MIOM – Magnet-impulse metal machining (USA, Germany) DMC – Dynamic Magnetic Compaction (Russia, USA) EMF – Electromagnetic forming (USA, Russia, Germany) PMW – Pulse Magnetic Welding (Germany, Russia) MIPP – Magnetic Impulse Pressing of Powder (Russia, Latvia) Pulse technological processes and their parameters Kinds of pulse Typical ratline Pressure and Time technological pressure-time Pm, MPa ta, s tk, s processes Types of explosion: 5∙104 1∙10-6 …1∙10-3 -contact 1∙104 1∙10-6 …1∙10-3 - in water 5∙103 500∙10-6 …5∙10-3 - unlimited Electro-hydraulic 100… 300 1…10∙10-6 effect 200∙10-6 Electromagnetic impulse (direct) 100 20…50∙10-6 500∙10-6 Generation of pulse electromagnetic field 1 – transformer 5 – tube 2 – rectifier 6 – detail 3 – capacitor’s battery 7 - coil 4 – discharger Theoretical background The electromagnetic force in the coil is determined by following equation: f v j H where j and H are the vectors of current density in the coil and electromagnetic intensity; μ is the magnetic inductivity. Impulse current i I me t sin t where Im is the current amplitude; ω is the circular frequency of discharge current; t is the time of current influence. The electromagnetic field intensity on surface of conductor respectively is determined as: H H e t sin t 1 m where Hm is the maximal value of intensity ; α is the attenuation coefficient. The pressure of electromagnetic forces on the surface of billet with high electric conductivity can be calculated as: p 1 H 12 2 Testing and control The electromagnetic field is induced in the gap between the coil and the plate at the instant an electric discharge of the capacitors. Scheme of compaction of a material in a rigid mold. 1 – impact plate; 2 – surge current generator; 3 – surge current generator; 4 – electromagnetic transducer; 5 – inductor with a winding; 6 – compacted material; 7 – mold. Main parameter range of IEG Equipment to the magnetic impulse compaction MIK-500 MIU-40 W = 0,5 kJ W = 40 kJ U = 0,8 kV Umax = 6 kV 1-60 imp/min 1-30 imp/min MIU-6 W = 6 kJ Umax = 6 kV MIK-300 1-600 imp/min W = 0,3 kJ U = 0,8 kV 1-30 imp/min Inductors for concentration of the magnetic field Spiral inductor Inductor with the concentrator and water cooling Flat inductor MIC for powder coating Pipe with an internal powder coating D0 = 16 mm, D1 = 13 mm, L = 80-300 mm. Preform of a worm Shell – copper, capillary - iron wheel with an external coating of Fe-C-Cu Manufacture of complex-shaped components by the magnetic pulse compaction method There is proposed method of preparing the multilayer components of tool. Working part consists of hard alloy (3) or steel (1), another of iron-copper alloy (2). Dimensions of parts can be increased due to using step pressing. To rise the density and the efficiency of the used forming envelope, it is expedient to use the infiltration method. 1 3 2 2 Components consisting of several parts: a) worm-wheel compact; b) inserts of mold dies. 1 – wheel, 2 – Fe-C-Cu ring, 3 – WC-Co insert. Magnetic pulse joining experintal research 1. Assembly diagram 2. Estimation of adhesion strength 3. Factors of the influence Assembly diagram Scheme of the built-up of powder Scheme of the assembling of powder detail detail: 1 – detail; 2 – rod; 3 – inductor; by expansion on the inside: 1 – inductor; 2 4 – pulse current generator – powder detail; 3 – bush Adhesive shearing strength Correlation between adhesive shearing strength depending on the energy level of the capacitive storage device W, rod surface roughness Rz and gap between details δ. MIOM device of discharge frequency 6 kHz. Energy levels: W=6 (1),W=8 (2), W=10 (3) Concentration of impulse magnetic field Concentrator Changing of magnetic induction Deformation of powder materials before sintering after sintering and MIC Changing of electromagnetic pressure on thickness of the detail from powder Deformation of sintered materials 1 1. Copper tube 2 D0 = 80 mm, δ0 = 2,0 mm 2. Preform from iron powder apparent density – 2,45 g/cm3, green density – 5,8 g/cm3 3. Iron powder after MIC (green density – 7,2 g/cm3) 3 Assembly of details One-piece connections of details from diverse materials Cu-steel, Al-bronze, Cu-Al MIOM application in powder metallurgy Part with unidirectional steel fibers in copper Macrostructure of fibers built-up onto holder (d = 0.7 mm) the copper holder (D = 0,7 mm, d = 15 mm) Assembling of bronze filters in Welds of the pipes (copper-steel, copper case. copper-titanium) Conclusions 1. Magnetic pulse joining method makes it possible to extend the field of application of powder metallurgy. 2. Features of the method enable one to press powder layers on steel compacts made by casting or forming. 3. Application of electromagnetic pulsed field in plastic deformation of metallic materials and in powder metallurgy gives new possibilities in producing of mechanical engineering and instrument-making details. 4. MIOM method is more effective in assembling of details from heterogeneous materials. 5. The optimal parameters must be determined in each MIOM process.
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