Dr,

I have a drawing showing a shot peen proccess, the notes show an intesity 0.003/0.004A and the shot size is MI 70H, i havent found what the MI 70H means, could you please help me with this issue?

As a guess: the MI might refer to Metal Improvement, the 70 is obvious and the H might imply that "Special Hardness" cast steel shot is to be used. Overall it sounds as if it is an -n-house shorthand. The author of your drawing might confirm this.

MI 70H definitely refers to The Metal Improvement company. 70 is the size and H mean high hardness, likely 55-65rc.

More than likely there is no difference between MI-70H and ASH-70 as per AMS 2431/2. This was done as a marketing strategy to prevent competitors from processing parts.

Thank you very much for your help