Forging process development and batch production of hinge beam forgings

A new intermediate billet and forging process was designed for the structure and dimensions of a certain type of hinge beam, and was optimized in detail by combining numerical simulation and test verification, and a new process method for intermediate billet and forgings was determined.

The six hinged beams of the six-sided top press are arranged symmetrically from the front, back, left, right, top and bottom, and are the key force-bearing parts of the six-sided top press, working under the ultra-high pressure of 110MPa of single-cylinder high-pressure oil pressure, which is the core part of the diamond press, and this puts high demands on its strength and life.
Restricted by manufacturing cost and manufacturing capacity, the hinge beam has been produced by casting from the 1960s to the present, but the defects such as looseness, inclusions and segregation existing in castings are inherently deficient compared with forgings, and the cast hinge beam is prone to fracture at the ears when used under the alternating load of the press for a long time, resulting in a short service life of the press, generally about 3 years.
With the improvement of equipment manufacturing level, six-sided top presses show the trend of higher technical requirements, larger specifications, longer life and higher precision, and the use of cast hinge beams can no longer meet the design requirements of large-tonnage, high-quality presses and market demand, and forged hinge beams are born with higher performance quality.

1. Forging drawing development

The part diagram of a certain type of hinge beam is shown in Figure 1(a), the part structure is cross-shaped structure, the middle is the cylinder, surrounded by symmetrical lug structure, the lug distance is about 170mm, the shape is more complex, from the analysis of material forming point of view, it is impossible to forge the lug even by using large die forging press, in order to reduce the forging weight as much as possible, the lug is formed by envelope, the cylinder is forged by copy, the forging structure The dimensions are shown in Figure 1(b).

Figure.1 Hinge beam part diagram and forging diagram

2. Forming scheme

2.1 Process flow

This hinge beam forging has a round structure in the middle and a wall structure with large dimensions around it, and the cross-sectional dimensions vary greatly. Then the forging billet is used for die forming.
The process flow is: ingot press jaws → upsetting, rounding → forging intermediate billet → die forming, of which the most critical is the intermediate billet structure and size determination and the design of forming die.
The manufacture of intermediate billet is usually made by longitudinal upper triangle division and transversal drawing, but no matter using square billet or round billet, the longitudinal upper triangle always has the problem that the upper, lower, left and right triangles are not aligned, so it is difficult to forge a billet with uniform size and shape, and in response to this problem, a special billet making die is designed, which can quickly and accurately complete the forging of intermediate billet, and the intermediate billet size is more uniform, creating good conditions for This will create good conditions for future die forming.

2.2 Die structure design

The structure of the forging die is designed according to the structure of the forging part and the structural parameters of the press, and the die consists of a lower die and a punch, as shown in Figure 2.

Figure.2 Forging die structure diagram

Figure.3 Structure of intermediate billet

Fig.4 Forging intermediate billet

Figure.5 Hinge beam forging

2.3 Process scheme

The main steps of the hinge beam forging process are: ingot rounding, press clamp handle → upsetting, rounding → forging intermediate billet → gas cutting down → die forming.
The most critical part of the process is the design of the structure size of the intermediate billet, which directly determines the final forming quality and forming size. The final structural parameters of the intermediate billet need to be optimized by combining with numerical simulation, and the final billet structure is shown in Figure 3.
The billet with the cross section in Figure 3 is used for forging production, and the main process steps are as follows:

• (1) Ingot forging intermediate billet with gas cutting down.
• (2) The billet is discharged from the furnace and the surface is cleaned of oxidation.
• (3) The billet is put into the die, and the billet is roughened to flush with the lower die by using flat header plate or flat anvil.
• (4) Upper punch, punch is positioned by special positioning device to prevent eccentricity of placement, and press machine presses down punch to size line.
• (5) Press down the blank all around to flush with the lower die.
• (6) Stripping the punch and leveling the end face.
• (7) Stripping the forging from the die.

3. Trial verification

After the numerical simulation optimization of the forging process, the basic forging process was determined, and the forging production of the trial product was carried out. Firstly, special billet making tool was used to forge the intermediate billet, as shown in Fig. 4, and the final die forming was carried out on a press with a pressure of over 80MN. The forging forming effect was good, as shown in Fig. 5, and the dimensions of the forgings basically met the requirements.

4. Batch production and quality control

According to the experience of small batch production, the forging process was optimized locally, and the problems in the production process were improved, and each key process parameter affecting the quality of forgings was sorted out and the corresponding control standard was formulated.
Batch production is very different from traditional single-piece production, and deviations in batch production can often have a fatal impact on the final forming:

• (1) Set up process nodes according to the process flow and manufacturing experience, and develop operation standards for each process to form standardized operations.
• (2) Set up professional working groups, set up responsible persons for each process, and collaborate with each work type to form a rapid response working mechanism.
• (3) Design special molds and tooling required for each process to improve production efficiency and quality.
• (4) Optimize the production flow and organize the production arrangement reasonably to make each process run stably.
• (5) Manufacture multiple sets of forging dies and develop specifications for die use and maintenance to prevent damage to the dies.

The forgings after the completion of batch forging were subjected to UT and performance testing after heat treatment and machining processes, and the results met the standards as well as the design requirements. The forgings after finishing are shown in Figure 6, and the final assembled six-sided top press is shown in Figure 7.

Figure.6 Finishing diagram of hinge beam

Figure.7 Six-sided top press

5. Conclusion

• (1) The process method can complete the forging and forming of the hinge beam forgings, and the forgings are qualified after later processing and heat treatment, UT and performance testing.
• (2) With the development of standardized operation procedures and rational organization of production arrangements, the batch production of large-size hinge beam forgings has been initially realized, with a production capacity of 5-8 pieces per day.
• (3) Nearly 1000 pieces of various types of hinge beam forgings have been completed, and on the basis of continued optimization of subsequent new processes and production organization, the annual production capacity of about 3000 pieces is expected to be realized.

Source: China Forgings Manufacturer – Yaang Pipe Industry (www.epowermetals.com)