What is high manganese steel and what are the high manganese steel cutting characteristics?

High manganese steel refers to the steel with manganese content of about 11% to 18%. High manganese steel is a kind of wear resistant steel. High manganese steel treated by water toughening can obtain higher plasticity and impact toughness. High manganese steel has high wear resistance, although its hardness is only HB 210, but its yield point is lower, so it has higher plasticity and toughness. High manganese steel under external pressure and impact load, will have a large plastic deformation or severe hardening phenomenon, the steel is dramatically strengthened, hardness increased significantly, up to HB450 ~ 550, thus has higher wear resistance. High manganese steel can be divided into high carbon and high manganese wear-resistant steel, medium carbon high manganese non magnetic steel, low carbon high manganese stainless steel and high manganese heat-resistant steel.

High manganese steel has the following characteristics in cutting process:

(1) Work hardening is serious: During the cutting process of high manganese steel, the austenite structure changes into fine grained martensite structure due to the large plastic deformation, which leads to severe hardening. Before Machining,the hardness is generally HB200 ~ 220, after machining the surface hardness of HB 450 ~ 550, depth of hardened layer is 0.1 ~ 0.3 mm, the degree of hardening and depth to be several times higher than 45 steel. The serious work hardening causes the cutting force to increase, intensifies the tool wear, also easy to cause the tool to break the edge to damage.

(2) High cutting temperature: As the cutting power is large, the heat generated by more than the high manganese steel thermal conductivity is lower than that of stainless steel, only 1/4 of medium carbon steel, so the cutting zone temperature is very high. When the cutting speed Vc<50 m/min, cutting temperature of high manganese steel is 200℃~250 ℃ higher than 45 steel, therefore, serious tool wear durability decreased.

(3) Difficult to break up: The toughness of high manganese steel is 8 times that of 45 steel, cutting is not easy to break and frizz.

(4) The dimension accuracy is difficult to control: The coefficient of linear expansion of high manganese steel is similar to that of brass. At high cutting temperature, local thermal deformation occurs and the dimensional accuracy is difficult to control. Rough machining should be carried out when cutting high manganese steel, then finish machining after the workpiece was cooled, to ensure the dimensional accuracy of the workpiece.