Hi! I would say the best answer is: they want a homogenous electrode, but that is not all. For explanation: it is because of the nature of the process they use, called Consumable Electrode Vacuum Arc Remelting. Titanium is highly reactive, especially when heated up. In molten state in reacts even with refractory materials (say stones), from which the normal crucibles and casting dies are made. The best choice so far is to cast the molten Ti in 'water-cooled copper' molds. And it has to be done in a closed chamber, where no air (oxygen and nitrogen) exists, that is, in vacuum or under an inert gas like argon. Both these conditions are fulfilled in Vacuum Arc Remelting method. All they need now is to form an electrode. But, the quality and efficiency of this method is affected by the strength, density, cleanliness and many other factors of the electrode (when consumable electrode is used as here). That is why they have to first crush the sponge and press it into two half cylinders which then will be joined to form an electrode. The initial sponge is too porous and can not be compressed enough. Another point is, when they crush it and then press the particles, it helps to have a much more homogene electrode, which is a really key point.
There is a lot to say or read about this, but that is what Metallurgists and Materials engineers need to do ;).
Hi! I would say the best answer is: they want a homogenous electrode, but that is not all. For explanation: it is because of the nature of the process they use, called Consumable Electrode Vacuum Arc Remelting. Titanium is highly reactive, especially when heated up. In molten state in reacts even with refractory materials (say stones), from which the normal crucibles and casting dies are made. The best choice so far is to cast the molten Ti in 'water-cooled copper' molds. And it has to be done in a closed chamber, where no air (oxygen and nitrogen) exists, that is, in vacuum or under an inert gas like argon. Both these conditions are fulfilled in Vacuum Arc Remelting method. All they need now is to form an electrode. But, the quality and efficiency of this method is affected by the strength, density, cleanliness and many other factors of the electrode (when consumable electrode is used as here). That is why they have to first crush the sponge and press it into two half cylinders which then will be joined to form an electrode. The initial sponge is too porous and can not be compressed enough. Another point is, when they crush it and then press the particles, it helps to have a much more homogene electrode, which is a really key point.There is a lot to say or read about this, but that is what Metallurgists and Materials engineers need to do ;).
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