ARKM said:
There's no such thing as "spring steel" or "carbon steel" for that matter as all steel has carbon in it. They are marketing terms used by sword distributers. Sometimes the use of the term "spring steel" by sword distributers refers to the same grade of metal commonly used for leaf springs in vehicles but not always. Springs are made from steel, yes but the steel they are made from is not called spring steel, just... steel. The carbon content and the amount of tempering are the main things that determine the flexibility of the metal.
It sounds like what you need is a very flexible steel flat bar? Is that correct? If so, you may have trouble finding the right material. I doubt Home Depot or Lowes will have anything useful. Most metal distrubters sell untempered mild steel which also will not work. Sorry I couldn't be of more help. Maybe someone else can chime in here with something that will work for your needs.