Thank you, but I'm sure is not japanese steel, what happens is that Valmont has the tendency to rename standard ASTM materials with a number of its own, and in their drawings they refer to the materials using that number.
I know for example that Valmont's S-22 is actually ASTM A572 Grade 65, but I have never came across S-25 before.
By the way below are the Valmont specs that I know their ASTM equivalent, hope they are useful for anyone.
S5 High Str Low Alloy Structure Steel (over 1.25in thk) ASTM A588 (50 KSI) WEATHERING
S23 Anchor Bolt Material ASTM A615 (75 KSI) ANCHORS
S99 High-Str Low-Allow Structural Steel (1.25in thk or less) ASTM A871 (65 KSI) WEATHERING
S228 Weathering and Low-Allow Steel Forging Matl for Base-Flange ASTM A871 (60 KSI) WEATHERING
S22 Copy not available ASTM A572 (65 KSI) STEEL
S128 Copy not available ASTM A633 (60 KSI) WEATHERING/STEEL
S29 Copy not available ASTM A633 (60 KSI) STEEL
S25 ?????