Welding Cu (80%) Ni(14%) Al(10%)Zn(8%)

[dwelding]

I'm welding with Plasma Transferred Arc technology, and we are
trying to weld MINOX.This is a kind of alleation with this
composition : Cu,Ni,Al,Zn. We preheat the pieces (pieces are
about 3 kg) about 400ºC (752Farenheit), and we are finding
porosities.... Why ?

I weld about 130Ampers of intensity,the surface is clean, but
the only problem is that we do not always WORK at 90º respect
the torch.


Am I doing the preparation well ? ?Maybe the temperature is to
hot ?? Is very important to work at perpendicular respect the
torch and piece ? ?

Thank you