4. How to choose tool materials when cutting high manganese steel?
High manganese steel is a difficult material to process, and requires high tool materials. In general, the tool material is required to have high red hardness, good wear resistance, and high strength, toughness, and thermal conductivity. For cutting high-manganese steel, you can use carbide or cermet as the tool material, or you can use CN25 coated blade or CBN (cubic boron nitride) tool. At present, the most common application is cemented carbide, in which YG-based cemented carbide has high flexural strength and impact toughness (compared with YT-based cemented carbide), which can reduce chipping during cutting. At the same time, the thermal conductivity of YG type hard alloy is good, which is beneficial to the removal of cutting heat from the tool tip, reducing the temperature of the tool tip and avoiding overheating and softening of the tool tip. YG-based cemented carbides have good grinding properties and can sharpen sharp edges. In general, the durability of the tool depends on the red hardness, wear resistance and impact toughness of the tool material. YG-based cemented carbides have high flexural strength and impact toughness, especially for improving fatigue strength, so they are suitable for roughing under shock and vibration conditions; It has high hardness, wear resistance and heat resistance and is suitable for finishing of continuous cutting.
YT-based cemented carbide has high hardness and high heat resistance, but it has low strength, high brittleness and poor thermal conductivity compared with YG-based cemented carbide. Therefore, when cutting high-manganese steel, it is common to use a tough YG-based hard alloy as a tool material. It should be noted that YG-type cemented carbide is not suitable for high-speed cutting, because at high-speed cutting of steel, the high temperature during cutting will cause strong crater wear on the rake face of the tool, and accelerate the wear of the flank. The tool is durable. Degree is reduced. In the case of high cutting speed and smooth cutting process, YT type hard alloy can be considered as the tool material.
An appropriate amount (generally about 0.5% to 3%) of TaC (tantalum carbide) or NbC (tantalum carbide) is added to the YG-based cemented carbide to improve its hardness and wear resistance without lowering its toughness. These advantages are more pronounced as the amount of cobalt in the cemented carbide increases. Therefore, general-purpose cemented carbides with Tac and NbC as additives are also suitable for the cutting of high-manganese steel.
Commonly used carbide grades for cutting high manganese steel are: YG8, YG6A, YG6X, YG8N, YW1, YW2A, YW3, YC45, 767, 798, 813, and the like.
The cermet blade is used for the finishing and semi-finishing of high-manganese steel. The cutting speed can be selected, the surface quality is good, and the tool durability is high. For example, the use of an Al 2 O 3 based ceramic tool for cutting 50Mn18Cr4 high manganese steel is 1 to 4 times more efficient than using a carbide tool.
CNC-coated blades and CBN (cubic boron nitride) tools are also available for cutting high manganese steel. When using CBN tools, it should be noted that the manganese content of the material to be cut cannot be higher than 14%. Otherwise, CBN may chemically react with Mn to make the tool wear severe and the cutting performance is degraded.
5. How to choose the tool geometry when cutting high manganese steel?
High manganese steel has high plasticity and toughness, severe work hardening, high cutting temperature, difficult chip breaking, and easy to cause chipping. Therefore, it is especially important to select the geometric parameters of the tool reasonably.
(1) Front angle and back angle: When cutting high manganese steel, in order to reduce work hardening, the tool is required to be sharp. However, it is generally not possible to use a large rake angle because the rake angle is not conducive to ensuring the edge strength and improving the heat dissipation conditions. A small rake angle or a negative rake angle and a large relief angle are often used, but too large a relief angle can weaken the edge strength and cause chipping. When using carbide tools, γ 0 = -3 ° ~ 3 °, α 0 = 8 ° ~ 12 °; when using ceramic tools, γ 0 = -5 ° ~ -10 °, α 0 = 5 ° ~ 10 ° . Take a small value when roughing the car, and take a big value when finishing the car.
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