I sell firesteels - you do not need a high carbon blade, or even an iron/steel blade to make the sparks. Got nothing to do with it.
Don't believe me? Try using a sharp piece of ordinary glass as a scraper. Sparks very well.
What you do need is something that is tough enough to keep a good edge while scraping against the firesteel. This produces tiny pieces of firesteel that spontaneously ignite upon contact with oxygen in the air. This is exactly the same thing as happens with the steel in "flint and steel" though firesteel metals spark exceedingly well.
Firesteels may vary in hardness, which is why they spark differently as the ease of scraping off tiny bits is harder/easier depending upon this.
See
Flint and Steel - What causes the Sparks though the materials are different the principle remains the same.