The hardness can reach HB450-550, and the hardening layer depth can reach about 0.3mm. . In the process of deformation of high manganese steel under impact pressure, it will consume the impact force that continues to act on the surface of the steel, preventing the force from being transmitted to the deeper inner layer. In addition, the thermal conductivity of high manganese steel is very low, only 1/3 to 1/4 of carbon steel, which brings great difficulties to cutting. Especially when drilling, the tool wear is serious and the durability is low. Therefore, hard alloy group drills are often used to drill high manganese steel. The body of the high manganese steel hard alloy group drill is made of 40Cr, and the cutting part is YG8 or YW hard alloy.

The shape of the cutting part is similar to that of cast iron group drills, except that the drill tip height h is increased to 0.08D, and the arc radius of the arc edge is increased to 0.4D to increase the tip angle of the point B and increase the strength of the tip , Improve the heat dissipation conditions, and also play a role in chip separation. Similarly, a double front angle is ground at the outer edge, and a negative rake angle is ground, and the rear angle at the outer edge is increased to 20°, as shown in Figure 1. After the drill bit has been sharpened, carefully grind the cutting edge with oilstone without any jagged edges. 8. What should be paid attention to when using cemented carbide group drill to drill high manganese steel?

<p>High manganese steel has high plasticity and toughness and high cutting temperature. When drilling high manganese steel with cemented carbide group, you should pay attention to the following issues: (1) Reasonable choice of cutting amount: cutting speed is too low or feed rate is too large ,

Will increase the Mechanical Bearing 607 force and easily cause the cutting edge to break. Generally take Vc=30～40m/min, f=0.07～0.1mm/r. (2) Full use of coolant: high-manganese steel has a large linear expansion coefficient, and full use of coolant should be used when drilling. If possible, the workpiece can be immersed in coolant to drill the hole to prevent the bit from biting the drill due to the shrinkage of the hole. Dead damage. (3) Strictly control the bluntness of the drill bit: If you hear a harsh scream or find that the rear corner and edge of the outer corner of the drill bit are worn about 1mm during the drilling process, the drill bit should be reground in time, otherwise continue to use It will accelerate the wear of the drill and cause damage. (4