I know that Dicyanoacetylene (carbon subnitride) combusts at a flame temperature of 4990°C. This is hot enough to melt almost all metals, except maybe some superalloys.

 

But what about thermite? At what temperature does thermite burn and how is it actually calculated?

hi

i don't know that temperature exactly BUT you may use burning magnesium bar to ignite it.

You could calculate it from the enthalpy of reaction, heat capacity, and some thermal conductivity parameters. The temperature will be different for different locations within the medium though. I know it's at least above the melting temperature for iron which is about 1811 K as per wikipedia.

It is difficult to predict the temperature a reaction rises too. I know its used to weld railway lines together and so is above the melying point of iron.

It melts the alumina too so it's hotter than 2070C or about 2340K.

Estimates probably vary a bit but 2500C (from wiki) looks to be about right