The raw materials used in forging are ingot, rolled, extruded and forged billets. The rolled, extruded and forged billets are the semi-finished products formed by rolling, extrusion and forging, respectively. In forging production, the organization and performance of raw materials can be improved by adopting reasonable technology and technological parameters in the following aspects; The columnar crystal is broken to improve the macroscopic segregation, and the cast structure is changed into forged structure. The internal pores are welded to improve the density of the material under suitable temperature and stress conditions. The ingot is forged to form fiber structure, and the forgings get reasonable fiber direction distribution through rolling, extrusion and die forging.
Control grain size and uniformity; Improving the distribution of the second phase (e.g., alloy carbide in lestenitic steel); Make the tissue get deformation strengthening or deformation - phase transformation strengthening. Due to the improvement of the above structure, the plasticity, impact toughness, fatigue strength and durability of the forgings have also been improved, and then through the last hot heel of the parts can get the parts required by the hardness, strength and plasticity of good comprehensive performance.
However, if the quality of raw materials is poor or the forging process is not reasonable, the forging defects may occur, including surface defects, internal defects or performance defects.
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.