Between the inner and outer, shells of a safe the vois is usually filled with insulation, steel and cast iron bars and anything else thy have handy to stop drilling and penetration by an angle grinder, as peeps have said previously, there will be dead bolts that wind out with the handle, along with a key operated lock.So cutting off the hinge knucles will have little effect.
You could try a safe engineer but not many of them around and they do charge quite a bit,as the safes they open have lots of cash inside.