... 9.Series of Air Suspension . First is to produce a master pattern , Second is mouldmaking , Third is to produce the wax patterns , ... Fourth is investment ,Fifth is to dewax ,Sixth is burnout and preheating ,Seventh is pouring ,Eighth is removal . The Investment Casting ... 2).medium alloy steel , and 3).high alloy steel). Connecting rod assembly-Semi-trailer Mechanical Suspension