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.
Material | Steel Code | Machinability |
Carbon Steel | 20 35 45 55 | 170 131 100 77 |
Alloy Steel | 35SiMn 42SiMn 38SiMnMo 38CrMoAlA 60SiMnMo 37SiMn2MoV 20MnMo 18MnMoNb 20Cr. 20CrMnMo 20Cr2Mn2Mo | 54 54 65 45 54 44 97 74 105 27 38 |
Alloy Steel | 40Cr 50Cr 35CrMo 40CrSi 38CrSiMnMo 35Cr2MnMo | 100 80 73 54 54 44 |
Roll Steel | 60CrMnMo 60CrMoV | 44 44 |
Spring Steel | 65Mn 60Cr2MoW 50CrVA | 50 33 44 |
Carbon Tool Steel | T7 T8 T10 T12 | 73 73 73 62 |
Carbon Tool Steel | 4CrW2Si Cr12MoV CrWMn 5CrMnMo GCr15 GCrI5SiMn W18Cr4V | 73 62 62 62 73 73 47 |
Stainless Steel | 2Cr13 3Cr13 1Cr18Ni9Ti | 100 77 62 |
Carbon Casting Steel | ZG230-450 ZG270-500 ZG310-570 | 144 144 118 |
Alloy Casting Steel | ZG35SiMn ZG35CrMnSi | 100 100 |
Alloy Casting Steel | ZG35CrMo ZGMn13 ZGCr22Ni2N | 100 118 100 |
Grey Casting Iron | HT150 HT200 HT250 HT300 | 83 65 52 45 |
Nonferrous Alloys | ZQSn6-6-3 ZQSn10-I ZQA19-4 ZHA166-6-3-2 ZHMn58-2-2 ZL104 ZL203 | 181 181 181 307 551 55I |
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).