text: I worked in a Steel Foundry.  It would take a temperature of about 2700 degrees F to completely melt steel.  It took a temperature of just over 3000 degree F to boil it.\n\nNow as for just heating it up to break it, that would be the temperature of the ovens where they put the steel in to heat treat it so that its glowing red and then before you put it in water or oil.  That temperature is around 1500 degrees F if I remember.  They used to break off unwanted parts of the casting at this temperature.\n\nDo, I google search on Heat treating Steel to get your temperature(that wasn't my department)\n\nP.S.  If your trying to get in a safe, use a plasma cutter.  It works better, lol