There is not really an easy answer to your question because there are so many different types of spring steel. From high Carbon (1%) to Cr-Mo steel with any in between.
The first question is obviously what the "strut" is made from. Are you sure it is a spring steel?
I would also agree with Bill that you must be sure that it is worth your while to actually attempt the repair. If you already have a lot of cracks just waiting to break, it would be better to just replace the strut.
Regards
Niekie Jooste