Would it be possible? Yes. Is it the most practical way? Not necessarily. Depending on the spring shape, it could possibly be made from pre-tempered spring steel without going through the heat treatment process. However it is not likely to work as long and as well as one that is properly made. What kind of equipment do you have? Mapp torch? Fire bricks? If you don't have this type stuff, then it would likely be cheaper to have it made. And do you have the broken spring parts or is it missing?