Typical Die Less Forging Process For Typical Forgings

Under the current situation of fierce market competition, with the continuous improvement of forging technology, enterprises are pursuing higher material utilization rates, leading to the emergence of various practical new technologies. In the forging process of large hydraulic presses, the appropriate design and use of some block dies and leakage plates can reduce machining allowances, save materials, and lower production costs. However, this increases mold expenses and prolongs the production cycle. Sometimes, if considered solely from the perspective of process design, unexpected effects can be achieved through clever design and full utilization of metal flow patterns. There are many such examples in actual production. This article introduces the dieless forming processes for three different types of forgings: large spheres, lifting hooks, and relatively complex-shaped reduced-opening pipe box seats.

1.Dieless Forming Process for Large Spherical Forgings

A certain aerospace machinery company had two large spherical forgings made of 45# steel, with a product weight of 5,908 kg, forged from an 8-ton steel ingot, and a spherical forging diameter of Φ1,100 mm. Previously, many hydraulic press manufacturers had no experience in producing such forgings and would typically first consider making hemispherical block dies. However, manufacturing and processing these dies not only takes a long time but also incurs high costs and poses significant difficulties. Based on metal forming principles and flow patterns, we developed a new process as shown in Table 1, which was successfully implemented in production. The final shape of the forging was a polyhedral sphere composed of countless small flat surfaces. After post-forging heat treatment, ultrasonic testing detected no defects larger than Φ1 mm.

This process can be divided into two stages. The first stage prioritizes compaction and thorough forging according to the principles of the effective compaction forging method, while the second stage focuses on shaping. In the final stage of sphere formation, by simply following the marked height on the hydraulic press scale and repeatedly pressing the edges while turning the forging with tongs, a sphere composed of countless small facets naturally forms. During the shaping process, some edges and corners may gradually cool down, turning dark red or even black. However, as the shape progressively approximates a sphere, the surface temperature becomes more uniform, and the temperature of the edges and corners rises again. Upon completion, the sphere, made up of numerous small facets, appears sparkling and spectacular, especially in the darkness of night.

2. Optimized Process for Hook Forging

Traditional hook forging processes typically involve pressing the tang, upsetting, drawing out a flat square, notching, rolling the shank, and then hot cutting to shape. This method is relatively wasteful in terms of material and results in large machining allowances. This is because when notching the step for the hook shank, the significant step difference often results in only a tapered surface being forged. Based on the principles of metal flow, in the new method, approximately 85% of the material for the hook shank is first pressed into the tong hold during ingot pressing. Subsequently, during the upsetting and drawing process for forming the flat square, a portion of the material is squeezed into the tong hold with each upsetting operation. Finally, when rolling the tong hold round, it is precisely forged into shape. Consequently, for a hook forging weighing about 5 tons, the new process often reduces the forging weight by more than 1 ton compared to the old method. For a hook forging made of material 20Mn, weighing 10,330 kg, and using a 16-ton ingot, its new forging process is shown in Table 

3. Dieless Forging Process for the Reduced-Opening Pipe Box Seat

The reduced-opening pipe box seat has a somewhat complex shape, with one end featuring a larger opening and the other a smaller one, along with tapered inner and outer walls (narrower at the top and wider at the bottom). Traditionally, producing such a component requires manufacturing a correspondingly sized inner mold. After forging and pre-forming, the billet is set onto this mold for final shaping.In 2003, a company received an urgent order for three pipe box seat forgings of different specifications. The material was 20MnMo, with a product weight of 12,567 kg and an ingot weight of 18 tons. Due to the short delivery time, it was impractical to manufacture three different sets of molds. Through detailed analysis and calculation, a novel forging process was ingeniously designed, as outlined in Table 3. By precisely controlling the forming operations without using any molds, the order was successfully completed and delivered on time.From the final shaping process of the pipe box seat, it can be observed that using an upper flat anvil and a lower rotary table, and rotating the upper end of the cylinder with a narrow anvil, causes the material to flow both towards the inner bore and the outer diameter. Subsequently, during outer circle rolling, the metal is further driven towards the inner bore, while the lower end face of the cylinder remains largely undeformed (water cooling can be applied if necessary). Repeating this process approximately three times achieves the required shape of the forging.

From the final shaping process of the pipe box seat, it can be observed that using an upper flat anvil and a lower rotary table with narrow-anvil rotation to press the upper end of the cylinder causes the material to flow toward both the inner bore and the outer diameter. Subsequently, during outer circle rolling, the metal is further driven toward the inner bore, while the lower end face of the cylinder remains largely undeformed (water cooling can be applied if necessary). Repeating this process approximately three times achieves the required shape of the forging.

4. Conclusion

(1) By skillfully utilizing the principles of metal flow, complex forgings can often be produced using only free forging methods.

(2) Optimizing forging processes can significantly reduce production costs and shorten the production cycle.（This article is excerpted from the Forging Technology Circle public account. Special notice is hereby given.）