Definition of hard turning
The so-called hard turning usually refers to the turning of haggard hard steel as a process method for final machining or finishing, in order to avoid the grinding technology commonly used at present. Hardened steel usually refers to the workpiece material with martensitic structure after quenching, high hardness, high strength, and almost no plasticity. When the hardness of hardened steel is >55HRC, its strength sb is about 2100-2600N/mm2. Usually, the workpiece has been roughed before heat treatment and hardened, and only finishing is carried out in the hardened state. Fine grinding is the most commonly used processing technology for finishing, but its narrow processing range, large investment, low production efficiency, and easy environmental pollution have always plagued the economical and efficient processing of hardened steel. With the development of processing technology, it has become possible for hard turning to replace grinding, and it has achieved obvious benefits in production. At present, polycrystalline cubic boron nitride (PCBN) tools, ceramic tools or coated carbide tools are used to machine hardened steel (55~65HRC) on lathes or turning centers, and the machining accuracy can reach 5~ 10&micr0;m, the root mean square value of surface roughness is less than 20&micr0;m on average.
High processing efficiency
Hard turning has higher machining efficiency than grinding, and its energy consumption is 1/5 of that of ordinary grinding. Hard turning often adopts large cutting depth and high workpiece speed, and its metal removal rate is usually 3 to 4 times that of grinding. In turning, a variety of surface processing (such as outer circle, inner hole, and groove, etc.) can be completed in one clamping, while grinding requires multiple installations. Therefore, the auxiliary time is short and the position accuracy between the machined surfaces is high.