How to Choose Materials for CNC Machining?

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 CodeMachinability
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).

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