Plazma modification of threading tools

A comprehensive model of the threading tool hardening on high-speed plasma heating has been presented as well as the mathematical description of the heating process. The reproduction of the model by means of computer simulation, based on the use of the finite elements method, including structural and physical parameters of the tool has been offered. The heat distribution in the heat-affected zone, and the relationship that makes it possible to determine the temperature at any point of the body, bringing the simulation results closer to the actual physical characteristics of the process have been shown. The analysis conducted in this article shows the prospects of using surface hardening methods to improve performance of thread-cutting tools. However, due to the complex profile of the working surface of the tools, application of any hardening method involves difficulties. On the strength of the above-said, with due regard to the established requirements for geometrical parameters of the thread-cutting tools and their loading conditions, as well as well-known recommendations for other types of tools, the technological processes for plasma processing of various types of thread-cutting tools have been developed. In developing the technology of plasma modification it is very important to select the optimum mode of heating, which ensures the formation of the modified zones of required size. This problem is solved by means of the analysis of thermal fields in the tool during plasma heating. The experience of using plasma hardening shows that the thermal cycle of heating and cooling materials can be controlled by varying such parameters as arc current and the speed of the plasma torch movement at a constant optimum level of the other parameters (plasma gas flow and the cooling water, the distance of the nozzle exit to the surface being machined)