Automatic Ultrasonic Detecting Apparatus for Steel ... Product length; 700-2000mm(designed reference)4. Product material; 30CrMo,35CrMo,34CrMo4,37Mn5. Cylinder wall thickness; 4mm- ... interlayer, etc. of cylinder’s internal wall resulted by raw material, flow spinning, and heat treatment, etc.8. Couplant ... length of the cylinder as 2000mm) Automatic Ultrasonic Detecting Apparatus for Steel Cylinder