High Pressure Jet Assistance in Steel Turning

Doctoral thesis, 2005

Steel turning is one of the most common industrial processes today. It is a very old process, where a lot of improvements and optimisations have been done throughout history. But, the struggle for further cost reductions pushes the process development into new areas. One of those is the use of pressurised cutting fluids in order to improve the machinability of the materials. This is a process predominantly used when turning high strength materials such as titanium and Inconel alloys. In this area the Ultra High Pressure Cooling (UHPC) process is accepted and used. But, when turning steel, the method has not been acknowledged to give enough benefits to be considered. Several tests showed that UHPC indeed could be a method giving substantial cost reductions when turning steels especially for long chipping grades. An extensive experimental investigation was therefore initiated with the purpose to increase the knowledge around UHPC in steel turning. From the start the research was focused upon quick industrial implementation, which has been done continuously for every new step in the development. Tests with high-pressure jets were done, both in laboratory and in industrial application. In combination with experiments available, diversified knowledge was collected into a coherent source of information to be used as a tool for implementation. Results show significant increase in chip control, its importance is sometimes overlooked in regard to production efficiency. In fact, chip control is more important than a long tool life. Improvements in tool life have been shown with possibilities to increase the cutting velocity with resulting improvement of productivity. To reach good results using UHPC in turning, certain rules of application are required. These have been defined. Especially important is the way the jet is applied into the cutting zone. It is not possible to achieve the benefits if the jet has an erroneous direction. Jet momentum has been found as the most comprehensive way to evaluate the effect on the chip form as a function of pressure and flow.