Resource efficient forging process chain for complicated high duty parts

Flash-reduced forging is a promising alternative for forging complicated high-duty parts. With a new process chain, the ability to reduce the existing flash quota of complex high-duty parts can make the difference in the competition and reduce the costs compared to flashless forging. The European Union is funding a research project which deals with the improvement of the forging sequence of a two-cylinder crankshaft by using flash-reduced forging. To increase the forecast quality of simulations using Finite-Element-Analysis for a future process chain design, the conventional existing process chain is simulated with FORGE3 and compared with industrial forging trials. Furthermore, a variation of simulation parameters has been used to get the significant influence parameters, fitting the results of these forging trials.

Forging, crankshaft, flash reduced, investigation simulation parameters

Flash-reduced forging is a promising alternative for the forging of complex heavy-duty parts. The use of flashless preforming operations is one possible approach in achieving this. Avoiding flash in preforming by keeping dies completely closed during the forging operation is the main challenge in flashless forging, especially when the parting line of the die is located at the center of the part. In order to do this, an advanced closing mechanism that completely locks the dies mechanically without the use of any spring mechanism was developed.

closed-die forging, closing mechanism, flashless forging, forging process, preforms

In common forging processes for geometrically complicated parts such as crankshafts, an excess on material (flash) is technically needed to produce a good part, which results often in a material utilization between 60 % and 80 %. But the material costs in forging represent up to 50 % of the total production costs. By decreasing the flash ratio, the material usage and production costs in forging operations can be reduced significantly. For a crankshaft, the development of a new forging sequence was necessary, to achieve the reduction of flash. This development was performed for an industrial two-cylinder crankshaft, based on finite element analysis (FEA) simulations. The new forging sequence consists of three flashless preforming operations, an induction reheating followed by a multidirectional forging and the final forging. By use of this forging sequence the flash ratio was reduced from about 54 % to less than 10 %. Due to the huge reduction of the flash ratio, material as well as energy can be saved from now on, thus increasing the competitiveness of the company.

hot forging, FEA simulation, reduction of flash, multidirectional forging, resource efficiency

The more complicated a forging geometry is, the more flash is necessary to achieve a form filling and a part free of defects. Most small and medium sized enterprises (SME) forge many different parts in small and medium batch sizes and cannot afford the high effort to design more efficient forging processes. In the paper the development of a resource efficient forging process chain for crankshafts is summarized. The forging sequence consists of flashless preforming steps and a flash reduced final forging. The tools were designed to work on industrially used fast moving mechanical presses. The last of the four flashless preforming steps is a multidirectional forming of the crank webs and a pin offset. To keep the forging forces on a low level and enable a stable forging process, an induction reheating of the preform before multidirectional forging was designed. The crankshaft was successfully forged with a reduced flash ratio of less than 10 %.

forging, flash, induction heating, preform, crankshaft

In modern business, the efficient use of resources, the optimization of processes and managing costs are key competitive factors. In the metal forming industry the pressure of competition is constantly increasing and the implementation of these competitive factors is important for staying in business. The increasing prices for energy and steel because the manufacturers to reduce these cost factors. With research activities even SME’s are able to improve their quality, for example by using warm forging processes. To keep the costs in a low level a reduction of the used material is necessary. Due to this aim, flashless preforming operations for a two cylinder crankshaft were developed. But the challenges are very long simulation and development time for designing the preforming dies. Further a highly qualified die steel material is required for complex preforming dies.

closed die forging, multididrectional forging, process chain, resource efficiency

The project REFoCh is about resource efficient forging of complex high duty parts, e.g. crankshafts. Within this project founded by the European Union, a new process chain for a crankshaft will be developed with the aim of reducing the flash quota significantly. In the conventional forging sequence, 54 % flash occur, the aimed flash quota is 15 %. To reach this objective, a multidirectional forging step will be implemented in the new process chain in order to reduce the material significantly.

flash reduced, multidirerectional forging, cranskshafts

The material costs represent up to 50 % of the total production costs. By decreasing the flash ratio the material usage and production costs in forging operations can be reduced. For complicated forging parts the development of a new forging sequence is necessary to achieve a flash reduced forging sequence. This development was performed for a two-cylinder crankshaft. The new flash reduced forging sequence is using flashless preforming operations, an induction reheating of the preformed complicated work piece and a flash reduced final forging. With the reduction of the flash ratio from 54 % down to 10 % the total energy consumption was reduced and the competitive capacity of forging SME’s is increasing.

flash reduced, process chain, crankshaft, induction heating