Yu, Y: Development and evaluation of protective sheet metal

The economic success of a hot closed-die forging process is highly dependent on the tooling costs, which account for up to 17-50% of the total price of forged parts. Improving the service life of forging dies is the most efficient way to reduce tooling costs. Since the degradation of the properties of forging dies occurs mainly at their surface layer, the most commonly used current method for prolonging tool life is to modify the material properties of the die surface by a surface treatment or coating such as nitriding, PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition), and duplex technology. These approaches can improve the hardness and thus the wear resistance of the die surface by producing protective material layers on it. However, these layers usually have a strong bond with the forging die, which impedes its removal after degradation. Therefore, the exchange of the whole forging die is necessary after the protective layer is worn away. As a result, the pace of production decreases, and total costs increase. In the search for a method that could reduce both tooling costs and repair time, a new concept, "protective sheet-metal die covers," was investigated. This concept proposes to develop an inexpensive and exchangeable sheet metal part for protecting forging dies from wear. The idea behind the proposed concept is to replace the die surface by a sheet metal part called a die cover. This cover protects the die from thermal and mechanical loads during forging cycles and can be easily exchanged after wearing out. Experimental studies of the die cover concept proved that the temperature of the die surface can be decreased by applying the die cover. However, these studies all faced the same problem: each die cover deformed and bonded with the billet after the first forging stroke.This work aims to evaluate the feasibility and protective effects of die covers and to develop the die cover concept into a feasible, effective, and cost-effective solution