Hard wire tends to stay straighter without tension or support. It will retain a bend without deforming such as being to used to form a spring. Hard wire can easily be softened by annealing just by quickly passing it through a candle flame. Half hard and soft wire is easier to form and ls used for simulating electrical wire such as spark plug leads. Soft and half hard wire can be hardened through a process called tempering where the wire is heated and then quickly quenched in water or oil but this is trickier to do than annealing. Sometimes metal that has be heated is placed in a relatively low heat(350 F) for an hour instead of quenching so the metal does not become brittle. Easier just to buy hard wire.
