I recently got some leafsprings steel from my work it's off an industrial frontload garbage truck, I was getting ready to drill holes in my tang for the scales before I quenched my blade and noticed it was already hard, I skated a file right off it, I went and grabbed a blade I forged but had not cleaned up yet and it was also hard, file tested it skated right of long story short I could not drill the blade and had to drift holes what could have caused this