DIY Arc Furnace
Here is a simple DIY arc furnace for melting refractory metals such as nickel, molybdenum or tungsten under an inert gas atmosphere. The furnace requires a current source - a 200A stick welder works just fine for our purposes. The furnace can reach temperatures in excess of 3500°C (6332°F). The design is based on the Arc lamp or the furnace of Henri Moissan. The positive electrode and the crucible (which itself is the negative electrode) are made of graphite.
The crucible
The graphite crucible is mounted to an aluminium base. The cavity should have a conical shape suited to the melt. The large cross-section of the crucible (here 3") prevents its overheating (which would increase the carbon contamination unnecessarily). For the inside edge of the cavity, sharp edges are to be avoided, since they will concentrate the arc and melt, introducing further carbon into the melt.
I use an old stainless steel vacuum evaporation chamber. This chamber has two SiO2 windows.
First try
