Experimental study has been conducted for an interstitial free(IF) sheet steel on its surface roughness evolution and formability with respect to grain size and sheet thickness effect. The surface roughness of IF sheet steel is proportional to effective strain, grain size and inversely proportional to sheet thickness; the larger grain reduces the formability by accelerating the surface roughening rate and enhance formability by raising the workhardening rate, while the latter effect plays the dominate role. The grain size effect on surface roughening and formability is more obvious when the sheets are thinner.
