Nicu Marian TRANDAFIR


34-41 BRAZAREA AlMn1/Ni 201 PLACAT CU Ag45CuZnSn

BRAZING OF AlMn1/Ni 201 CLADDED WITH Ag45CuZnSn
Brazing aluminium to nickel plates it is a very sensible process being influenced by physical brazing parameters, brazing devices, but also by type of materials used. Brazing process was carried out in a horizontally furnace under a controlled nitrogen atmosphere containing several enclosures. They were used two dissimilar base metals (an aluminium alloy and pure nickel) and the filler metal was the Ag45CuZnSn clad of the nickel base metal; this type of filler metal led to a brazed joint with percentages of defects below 6%, due to its very good adhesion to both the brazable surfaces of the base metals involved.
Keywords: brazing, Al-Ni
Cuvinte cheie: brazare, Al-Ni

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34-40 PRODUCEREA BILELOR MICI

MAKING SMALL SPHERES
The mill for the production of small balls, of hard and semi hard material contains as a main part a ring covered with the abrasive material (glued) on the abrasion surface. The ring has the vertical axis. The abrasive surface is made by gluing with glue that softens by heating. The moving of spherical material is made with compressed air, rotating in the grinding space, motion imprinted on the diffuser air. Compressed air comes through the center of the mill through a circuit with minimal aerodynamic resistances. Air pressure: 1 – 2 bar. Ball size: 1 mm. The grinding space has a 7 (horizontal) x 6 (vertical) mm section with an (average) length of 162 mm. The used raw material has cubic shape with a 30 % greater edge than the ball diameter.
Keywords: small spheres, technology, hard and half hard materials
Cuvinte cheie: sfere mici, tehnologie, materiale dure și semidure

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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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