Machine free forging can be divided into hammer free forging and hydraulic press free forging according to the different types of equipment used. The former is used to forge small and medium free forgings, while the latter is mainly used to forge large free forgings. Radial forging machine has been developed in recent ten years. It is mainly used for forming step shaft and special-section shaft forgings.
The essence of the free forging process is to use simple tools to gradually change the shape, size and structure of the original blank to obtain the desired forging process. The research content of free forging process is the forming law of forgings and the method of improving the quality of forgings.
The advantages of free forging are: the tool used is simple, strong versatility, flexibility, so suitable for single and small forging, especially the production of large forging, which provides an economic and quick method for the trial production of new products, non-standard tooling fixture and die manufacturing. In order to reduce the burden of die forging equipment or make full use of the existing die forging equipment, simplify the structure of die forging, some die forging parts of the blank step is also completed on the free forging equipment. However, the disadvantages of free forging are: low precision of forging, large processing allowance, low productivity, high labor intensity, etc.
The design process and design principle of forging drawing are the same as that of hammer die forging, but the technological parameters and specific work steps should be handled appropriately according to the characteristics of the forging press.
The characteristics of choosing the parting position: for some forgings, the parting surface is no longer on the longitudinal section of the forging, as in the hammer die forging, but on its maximum cross section. This parting has many advantages.
The length of the parting contour line is reduced, the shape is simplified, the volume of the rough edge is reduced, the blank, the die material and the machining time are saved. Cutting die becomes simpler and easier to manufacture. When the die forging is set up, the deep hole cavity that is difficult to forge on the hammer can be forged. The forming method of forgings is changed in the process of erect die forging. Extrusion and block roughing can be used instead of drawing and rolling.
For forgings with complex shapes, the die parting method is the same as the hammer die forging, and the maximum longitudinal profile is still divided.
Allowance and tolerance: Generally speaking, the allowance of die forging on the crank press is 30%-50% smaller than that on the hammer, and the tolerance is reduced accordingly, usually within 0.2-0.5mm. When the extrusion deformation is adopted, the radial allowance of the rod can be smaller, generally only 0.2-0.8mm.
Die forging inclination, fillet radius and punching with skin: The die forging inclination is the same as on the hammer when the jacking rod is not used. If the jacking rod is used, the die forging inclination can be significantly reduced. Due to the low inertia and poor capacity of metal filling groove, the radius of rounded corner should be larger than that of die forging on hammer. The method of determining the radius of fillet and punching and the drawing rules of forgings can refer to the processing of hammer die forgings.