What are the cutting properties of different metals?

The difficulty of cutting metal materials is called machinability. If the material is easy to cut, it is called good machinability, otherwise it is called poor machinability. Usually it can be measured by cutting force, cutting heat, tool wear and tool durability, workpiece surface quality and chip control. What are the factors that affect the properties of cutting materials?

I. Physical characteristics:

Thermal conductivity: Materials with high thermal conductivity will allow higher cutting speed.

Linear expansion coefficient: it affects the degree of thermal expansion and cold contraction of materials and the machining accuracy.

2. Chemical composition: The chemical composition and proportion of materials are the fundamental factors that affect the mechanical properties, physical properties, heat treatment properties, metallographic structure and machinability of materials.

Carbon: The hardness and strength of materials increase with the increase of carbon content.

Nickel: Nickel can improve the heat resistance of materials, but significantly reduce the thermal conductivity of materials; Austenitic steel containing a large amount of nickel is severely hardened.

Vanadium: With the increase of vanadium content, the grinding performance of the material becomes worse.

Molybdenum: It can improve the strength and toughness of materials, but the thermal conductivity of materials decreases.

Tungsten: It can improve the thermal strength, high temperature strength, hardness and normal temperature strength. However, the thermal conductivity of the material decreased obviously.

Manganese: It can improve the hardness and strength of materials and reduce the toughness of materials. When the manganese content is too high, the machinability of the material becomes poor.

Silicon: It can reduce the thermal conductivity of materials.

Titanium: Titanium is an element which is easy to form carbide and has poor machinability.

Third, the mechanical properties of materials:

Hardness and strength: the material has moderate hardness and strength and good machinability. The higher the hardness and strength, the worse the machinability.

Toughness and plasticity: materials with high toughness and plasticity have large resistance, large deformation, large heat production and poor machinability when cutting.

Elastic modulus: it is an index of material stiffness, and a large elastic modulus means that the material is not easy to produce elastic deformation under the action of external force. However, the material with small elastic modulus has large elastic recovery when cutting, and it is difficult to cut because of large tool friction.

Four, metallographic structure:

Ferrite: its hardness and strength are very low, its plasticity and toughness are high, and it is easy to produce chips when cutting, so its machinability is poor.

Pearlite: Spherical pearlite has good machinability.

Carbide: high hardness but fragile, easy to crack and difficult to cut.

Austenite: Hardness is not high, but plasticity and toughness are high. Surface hardening and cold welding of chips with tools will seriously affect cutting performance.

Verb (abbreviation of verb) Selection of cutting oil:

Non-ferrous metals: When cutting copper, aluminum alloy and non-ferrous and light metals, the cutting force and cutting temperature are not high, so special cutting oil for copper-aluminum alloy with low anti-wear agent ratio and good corrosion resistance can be selected.

Cast iron: When cutting cast iron, choose cutting oil with strong antirust function. When cast iron and bronze are brittle materials, chips are often formed during cutting, which are easy to flow around with cutting oil and between machine tool rails, causing parts damage. Cutting oil with good cooling and cleaning performance can be used and filtered.

Alloy steel: When cutting alloy steel and titanium alloy, if the cutting amount is low and there is no requirement for surface roughness, such as broaching and thread cutting, extreme pressure cutting oil with excellent extreme pressure performance can be selected as the main additive.