Nicu Marian TRANDAFIR


32-37 CONTACTE ELECTRICE CU DENSITATE RIDICATĂ PENTRU CURENŢI INTENŞI PRODUSE PRIN METALURGIA PULBERILOR

ELECTRICAL CONTACTS WITH HIGH DENSITY FOR STRONG CURRENTS, MADE BY POWDER METALLURGY

 

Electrical contacts for strong currents by infiltration after sintering, was not satisfactory because the final density is much higher (11,100 kg/m3) and porosity is much lower (10.85 %). The infiltration after sintering contains: powder mixture preparation (W – 52 mass %, Ni – 2 %, Cu – 46 %, zinc stearate – 0,7 %  – 7 g), homogenization, pressing (4,5 MPa), sintering (730 and 780 oC). The green density is almost constant, with an identical porosity of the first after the end of the process (14,28 %). By infiltration the density increased drastically (10,832 kg/m3), its variations were increased also and porosity decreased (at 10.85 %). The attained density is not sufficient for electrical contacts work (11,100 kg/m3), but it is closer. Way to improve density: pressing, sintering, and repressing (10,700 kg/m3).

 

Keywords: sintered electrical contacts, W-Cu

Cuvinte cheie: contacte electrice sinterizate, W-Cu

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32-35 BRAZARE NICHEL-ALUMINIU

BRAZING OF NICKEL-ALUMINIUM

 

The brazing between nickel and aluminium plates is a very sensible process being influenced by type of used materials and by brazing devices which maintain in contact the metal plates. These brazing devices have a very important purpose, their pressure affect directly the capillarity force. If the brazing devices are too tight (like 7 bar pressure), the filler melted metal escape from the grip, causing presence of defects in the joint; if the brazing devices are not tight enough (like 5 bar pressure) the capillarity forces become weak, allowing the voids inside the joint. Therefore, it’ is optimal for a nickel-aluminium brazed joint without defects a 6 bar pressure, created by brazing devices,

 

Keywords: brazing, Ni-Al

Cuvinte cheie: brazare, Ni-Al

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