618HH the vacuum melting of chromium - nickel - molybdenum alloy steel, hardened and squandered by the factory prior to tempering, has the following advantages: * No quenching crack and the risk of heat deformation * No heat treatment costs * Reduce the molding cycle Reduced tooling costs required (eg: no need to correct distortion) * Die easily modified Can be subjected to nitrogen and flame hardened, the mold side to increase surface hardness and wear resistance

681HH since the production has remain high quality, low sulfur levels, the factory has been pre-hardening heat treatment to 36-40HRC steel can therefore have the following characteristics: * Good polishing performance of a few light etching * Good processing performance ? High purity of several excellent uniformity * Wear better, longer die life

Note: 681HH has been copied to 100% ultrasonic testing

Large size such as thickness over 100 mm has been pre-processing, steel milling by the rough surface. To provide the following support: * Save weight * Have to remove just the surface of the decarburization layer (black) * Standard size (positive tolerance) ? Reduce the amount of mechanical processing ? No oxide layer to reduce the amount of machining and tool wear