The machinability of a metal material refers to the difficulty level of cutting metal into machining parts that meet the requirements. There are many factors affecting machinability. Up to now, the machinability of a material cannot be fully represented by a certain property of the material, such as metallographic structure and mechanical property. People normally choose different methods to express it according to specific situations. At present, the most commonly used method in production is the cutting speed V60 when the tool life is 60 min. The higher the V60 is, the better the machinability of the material is. And the V60 of 45 steel with σb＝600MPa is used as a benchmark, which abbreviated as (V60) f. If compare (V60) f with the V60 of other materials, the ratio is called relative processability. The relative processability of common materials is shown in Table 1-1.
Relative processability of CNC Machining Material
If analyze according to the mechanical properties of metals, it is generally considered that the machinability is good when the hardness is in the range of 170-230 HB. If the hardness is too high, not only is it difficult to machining, but the tool will also be quickly worn. When HB>300, the machinability decreases significantly; When HB=400, the machinability is poor. If the hardness is too low, it is easy to form filings and winding, resulting in heating and wear of the tools. After machining the CNC parts, the surface roughness will be very high. When the plasticity of the material increases and ψ= 50%~60%, the machinability also decreases significantly.
Hard-to-work metals must be CNC machined by advanced tools such as carbide blade. For example, carbide blade YG6X can be used to process heat-resistant alloys.YG3 can be used to machining quenched steel and so on; YW1 can be used to working stainless steel, high manganese steel, etc. YW2 can be used to process titanium alloy, austenitic stainless steel, etc. YA6 can be used to machining high manganese steel, quenched steel, and hard cast iron, etc. White corundum 60# (ZR1) grinding wheel can used to grind nitrided piston rod with hardness≤70HRC, and so on; And YW1-YG6X tool can use for turning 45 quenched hard steel (55~62HRC. Surface roughness up to Ra63~16μm).