Derek Cohen (in Perth, Australia)
Bill, I suspect that the defining quality for a scraper - which is prepared on a grinder - is the hardness of the steel. That this creates a suitable wire. After this, there will be some steels that are expected to hold the shape of the wire longer. M2 should respond to the heat issues in scraping, but is it as abrasion resistant as, say, M4?

Many years ago I made a scraping blade out of a hex key for a router plane for use when there was reversing grain. This steel was pretty hard ...

My website article is here: http://www.inthewoodshop.com/ShopMadeTools/Stringing%20Cutter%20or%20Scraper%20Blade%20for%20Router%20Plane.html

Regards from Perth

Derek