1,ASTM 4340 Alloy Steel Flat Bar 2,Thickness:10~90mm 3,Width:60~610mm 4, ... Co., Ltd.alloy structural steel AISI 4340/GB 40CrNi2Mo Dimensions:Flat steel: thickness:10mm~90mm; width: 60mm~610mm; length: 4~6m ... high strength such as aircraft engine ,cross beam,undercarrige,pressure vessel,rocket hull,heavy-load torsion shaft,etc.