Why SAE standard flanges of ISO 6162 must be forged
SAE flanges conforming to ISO 6162 are mainly used for piping connection of hydraulic system. Hydraulic system is a power transmission device, in order to improve the efficiency of transmission, usually using higher working pressure, high working pressure will make the flange subject to a large load.
For example: for DN 25 (1") flange, when the system pressure is 250 bar, the hydraulic force will be more than 15 kN. In addition, the hydraulic system work, due to changes in the movement of the load, commutation and other circumstances, the circuit pressure is constantly changing, so the flange is subject to dynamic strong load, or even shock load. Therefore, SAE flanges must be machined from forged blanks, and not from cast parts.
Casting in its cooling and curing process from the liquid state, metal crystals from the surface began to crystallize and extend to the center, so its organization is relatively neat and loose, crystal interface along the cross-sectional direction, the tensile and shear strength of the casting is poor. According to the load condition of SAE flange, it is mainly subjected to shear stress, which is the weak point of the casting, casting SAE flange is obviously not suitable.
The forged parts are different from the castings, the crystalline fiber structure is longitudinally arranged, high shear strength, at the same time, the forging material is extruded and deformed in the process of forging and forming, the structure becomes tight, and the comprehensive strength is greatly improved. In addition, the forged blank parts, less porosity, cracks and other defects often found in castings. The above factors are the reasons why forged parts are used to make SAE flanges.
