Environmental awareness and a growing demand for efficient resource utilization encourage the realization of lubricant-free forming processes. A first step in accomplishing dry sheet metal forming is to gain knowledge...Environmental awareness and a growing demand for efficient resource utilization encourage the realization of lubricant-free forming processes. A first step in accomplishing dry sheet metal forming is to gain knowledge about the changing tribological conditions and to identify the relevant influencing parameters. The commonly used flat strip drawing test was selected to investigate the tribological conditions in the flange area of deep drawing processes. The influencing factors of contact pressure and varying drawing velocities were analyzed under dry and lubricated conditions. Additionally,the tool and workpiece surfaces were characterized. Besides lubrication, the contact pressure mainly determines the tribological conditions. In lubricated tests higher normal pressure reduces friction, whereas without lubrication higher pressure results in slightly increasing friction. A changing drawing velocity affects the friction when lubricant is applied. In dry experiments, no influence of velocity was found. Results of surface characterization reveal adhesion as main wear mechanism under dry conditions. Based on the investigated influence of the process parameters, an increase in process understanding for dry forming operations is derived.展开更多
High performance components, e.g., fasteners, nowadays are usually made out of cold forged and heat treated steels like steel 1.5525 (20MnB4). To overcome the problems of heat treatment, e.g., low surface quality, new...High performance components, e.g., fasteners, nowadays are usually made out of cold forged and heat treated steels like steel 1.5525 (20MnB4). To overcome the problems of heat treatment, e.g., low surface quality, new workpiece materials for cold forging should be found to achieve the needlessness of heat treatment after cold forging. One possible material is given by high nitrogen steels like steel 1.3815 (X8CrMnN19-19). Due to the high strain hardening of these materials the process and tool design for an industrial batch process are challenging and should be conducted by FE-simulation. The numerical results show that, high strength tool materials, like PM-steels or cemented carbides, in most cases, are inevitable. Additionally to the selection of suitable tool materials, the tool layout should be developed further to achieve a high loadability of the tools. The FE-models, used for process and tool design, are validated with respect to the materials' flow and occurring forming force to assure a proper design process. Also the comparison of strength of components made out of steel 1.5525 in quenched and tempered conditions and steel 1.3815 in strain hardened condition is done. The results show that the component made of steel 1.3815 has a significantly higher strength than the component made of steel 1.5525. This shows that by the use of high nitrogen steels a high performance component can be manufactured by cold forging.展开更多
基金the German Research Foundation (DFG) for supporting the present investigations by funding the SPP 1676 project ME 2043/43-1
文摘Environmental awareness and a growing demand for efficient resource utilization encourage the realization of lubricant-free forming processes. A first step in accomplishing dry sheet metal forming is to gain knowledge about the changing tribological conditions and to identify the relevant influencing parameters. The commonly used flat strip drawing test was selected to investigate the tribological conditions in the flange area of deep drawing processes. The influencing factors of contact pressure and varying drawing velocities were analyzed under dry and lubricated conditions. Additionally,the tool and workpiece surfaces were characterized. Besides lubrication, the contact pressure mainly determines the tribological conditions. In lubricated tests higher normal pressure reduces friction, whereas without lubrication higher pressure results in slightly increasing friction. A changing drawing velocity affects the friction when lubricant is applied. In dry experiments, no influence of velocity was found. Results of surface characterization reveal adhesion as main wear mechanism under dry conditions. Based on the investigated influence of the process parameters, an increase in process understanding for dry forming operations is derived.
文摘High performance components, e.g., fasteners, nowadays are usually made out of cold forged and heat treated steels like steel 1.5525 (20MnB4). To overcome the problems of heat treatment, e.g., low surface quality, new workpiece materials for cold forging should be found to achieve the needlessness of heat treatment after cold forging. One possible material is given by high nitrogen steels like steel 1.3815 (X8CrMnN19-19). Due to the high strain hardening of these materials the process and tool design for an industrial batch process are challenging and should be conducted by FE-simulation. The numerical results show that, high strength tool materials, like PM-steels or cemented carbides, in most cases, are inevitable. Additionally to the selection of suitable tool materials, the tool layout should be developed further to achieve a high loadability of the tools. The FE-models, used for process and tool design, are validated with respect to the materials' flow and occurring forming force to assure a proper design process. Also the comparison of strength of components made out of steel 1.5525 in quenched and tempered conditions and steel 1.3815 in strain hardened condition is done. The results show that the component made of steel 1.3815 has a significantly higher strength than the component made of steel 1.5525. This shows that by the use of high nitrogen steels a high performance component can be manufactured by cold forging.
