Development of Shaped Ring Rolling via Numerical Simulation
Italian companies Felb, a forging company, and EnginSoft, a design company, collaborated on a simulation for a profiled rolled ring using FORGE NxT® simulation software by Transvalor. Felb forged the rings after verifying its equipment requirements and optimized part grain structure using the simulation. They cut costs in production and shipped a high-performance part to the customer.
Felb Srl of Breno, Italy, was established in 2006 to meet market demand for medium-weight forgings of up to 10 tons. This market sector refers to medium-size forgings of a maximum length of 20 feet (6 meters), maximum diameter of 8 feet (2,500 mm) and maximum width of 6.5 feet (2,000 mm). Maximum dimensions for rings are 13 feet in diameter (4,000 mm) and a maximum height of nearly 3 feet (870 mm). Special equipment allows the production of shaped forgings according to drawings, bars of various sectional sizes, discs, shafts, rollers, molds, forms, bushings and flanges. All manufactured pieces can be submitted for machining and heat-treatment processes.
Some time ago, Felb received an order from a new customer to supply 200 A105 steel rings (Figure 1) of approximate machined dimensions of 3 feet (900 mm) in diameter and about 20 inches (500 mm) in height. The part could have been produced by the traditional process of ring rolling and subsequent machining. Given the nature of this part and the size of this order, however, Felb management decided to evaluate the possibility of forming a shaped ring in order to optimize material usage and to provide a final part with better in-service performance.
Due to Felb’s limited experience on the shaped rolling process, the company employed EnginSoft of Trento, Italy, a consulting firm in the field of simulation-based engineering science (SBES) to collaborate on this project. EnginSoft used the modeling software system FORGE NxT® developed by Transvalor – a package with which they had 20 years of experience – to speed the design process and shorten the lead time for manufacturing.
Fabio Fioletti, Felb’s material engineer and technical manager with experience in design and simulation of forging processes, developed the preliminary numerical analysis of the ring-rolling process along with EnginSoft’s Metal Forming Team. The aim of this analysis was to evaluate the technical feasibility of this project, particularly regarding the upper flange of the part starting from different preformed rings.
Based on company experience with ring rolling, the studies and simulations of several scenarios (Figure 2) and geometries of the king roll allowed the validation of feasibility using Felb’s equipment. Specifically, we needed to verify the limits of the maximum allowable torque on the king roll and axial force on the mandrel (Figure 3). These preliminary evaluations were completed in less than a week, and the order was issued to the shop floor.
Concurrently, simulation activities were focused on the evaluation of the best forging sequence to obtain the optimal preform in order to minimize the material required for the job. At this point, several modifications on flange height and both internal and external diameters were evaluated. All the solutions were subsequently validated by numerical simulations of ring-rolling processes (Figure 4).
The numerical simulations allowed us to evaluate the technical feasibility of the part by forging and shaped ring-rolling processes. The traditional process involved massive machining, which led to high material waste. Furthermore, machining altered the material grain structure, which would lead to a lower capacity of the ring to withstand in-service loads. The process we developed led to a minimum of oversize and better grain distribution (Figure 5), leading to improved part performance. Verification of final parts showed an increase in hardness (+40HB) that led to a revision of required thermal-treatment cycles as evaluated by the software.
Benefits of Simulation
Had we used the trial-and-error approach, the development of the shaped ring-rolling technique for this job would have taken four to five times longer and added costs of real tests and equipment. With the use of digital simulation techniques, however, we developed a process that yielded an actual result very close to one we modeled (Figure 6). The developed simulations allowed for a very fast fine-tuning phase, highlighting the causes of some filling defects on the flanges and suggesting the best actions to be performed in order to complete the profile on the real process.
The overall benefits of simulation for Felb included:
- Radical innovation of the production processes, with implementation of shaped ring rolling and drastic reduction of development times and costs
- Optimization of lead time – approving necessary equipment orders in less than one week
- Validation of the rolling machine requirements – forces and torques below 70% of the nominal performance
- Optimization of material usage, with weight reduction higher than 15% compared to the previous solution
The overall benefits of simulation for the customer included:
- A faster reply to their quotation request
- Enhanced performance of the final parts due to the better compaction of the material and to the optimized grain distribution provided by the shaped ring-rolling process
- Reduction of time and cost related to machining operations (up to 40%)
Conclusion and Future Developments
Thanks to the knowledge developed with the collaboration with EnginSoft, Felb was able to glean the advantages of numerical simulation.
Felb is now developing similar approaches to other customers, with high-value proposals supported by the contribution of numerical simulation. This has already led to returns on business. Additionally, Felb has expanded the use of simulation to heat-treatment processes of forged and rolled parts in order to perform a complete integration of numerical simulation in major company processes.
Authors Federico Fracasso (email@example.com) and Marcello Gabrieli (firstname.lastname@example.org) are simulation experts with EnginSoft, Trento, Italy. Author Fabio Fioletti is a material engineer and technical manager with Felb Srl, Breno, Italy. He may be reached at email@example.com.