1. Tool selection
Generally, most high manganese steel materials can choose yw1 and yw2 cemented carbides when machining. Yw1 has good thermal hardness, can withstand a certain impact load, and has good versatility. Yw2 has slightly lower wear resistance than yw1, but has high strength, and can withstand a large impact load. They have good thermal conductivity and are not easy to bond between chips and tools, so they are more suitable for processing high manganese steel materials.
When the shape, size and structure of the workpiece are not convenient to use cemented carbide tools, new high-speed steel tools can be used. It has the characteristics of high hardness, wear resistance, high red hardness and good thermoplastic.
2. Tool cutting parameters
Processing high manganese steel should consider the process characteristics of the part structure and materials, as well as the cutting force and cutting heat generated, because the parts are easy to deform and affect the product quality. At the same time, there are certain requirements for the geometric parameters of the internal thread turning tool: the front angle, rear angle and auxiliary rear angle of the internal thread turning tool should take into account the influence of the rising angle of the workpiece thread, so the large rear angle is selected for the coarse turning tool. The precision turning tool grinds out the arc radius on the rake face, which makes the formation and removal of chips more convenient. The roughness of the arc surface needs to be very low. Careful grinding after grinding will have a direct impact on the processing quality.
3. Cutting parameters
The cutting performance of high manganese steel is poor. In order to ensure that the tool has a certain durability, the cutting speed should not be too high. When turning with cemented carbide tools, the cutting speed is (20-40) m/min; When turning with ceramic tools, the cutting speed is (50-80) M-min. In order to avoid cutting the tool on the surface of the workpiece and the hardened layer after the previous cutting, the cutting depth and feed rate should not be too small. Sometimes, in order to improve the tool durability and ensure a certain cutting efficiency, a low cutting speed of (8-20) m/min and a large feed of (0.8-1.5) mm / R are used for rough turning.
The machinability of high manganese steel can be improved by heat treatment before rough machining. The method is to heat the high manganese steel to (600-650) ℃ and cool it after holding for 2 hours, so that the austenite structure of the high manganese steel can be transformed into austenite structure, so that the work surface hardening can be significantly reduced and the machinability can be significantly improved. The workpiece shall be quenched before finishing turning and use, so that the steel structure can be transformed into austenite again.