Why Stainless Steel Is Hard to Machine?

Stainless steel is one of the main CNC machining materials in our machine shop. Compared with the high quality carbon steel, stainless steel material has added Cr, Ni, N, Nb, Mo and other alloying elements. The increase of these alloying elements not only improves the corrosion resistance of steel, but also has a certain effect on the mechanical properties of stainless steel. For example, martensitic stainless steel has the same carbon content when compared with AISI 1045 mild steel, , but the relative machinability is only 58% of AISI 1045 steel. Austenitic stainless steel is only 40%, while austenitic – ferrite duplex stainless steel has high toughness and worse cutting property.

Why Stainless Steel Is Hard to Machine

Below are the 4 factors to explain why it is hard to machine stainles steel material.

1. Large cutting force and high cutting temperature

Stainless steel has high strength, large tangential stress and plastic deformation when cutting, so the cutting force is large. In addition, the thermal conductivity of stainless steel is very poor, causing the cutting temperature to rise, and the high temperature is often concentrated in the narrow area near the edge of the tool, which speeds up the wear of the tool.

2. Serious work hardening

Austenitic stainless steel and some high alloy stainless steel are austenitic structure, so the tendency of work hardening during cutting is large, which is usually several times than carbon steel. Especially when the cutting tool works in the hardening area, the tool life will be greatly shortened during stainless steel machining process.

3. Easy to stick cutting tools

Both austenitic stainless steel and martensitic stainless steel have the characteristics of chip toughness and high cutting temperature during CNC machining process. When the strong chip flows through the front cutting tool surface, we can find bonding, fusion welding and other sticky tool phenomenon, which will affect the surface roughness of stainless steel machining parts.

4. Tool wear is accelerated

Stainless steel generally contains high melting point elements, large plasticity and high cutting temperature. These features speed up tools wear, so the tools need to be changed frequently. Therefore, thhe tool wear will affect the production efficiency and improve the cost of tool use.

From the above, we can see stainless steel machining is more difficult than other CNC machining metals, it is necessary to choose high quality cutting tools and reduce the machining speed slightly, thus to guarantee the quality of stainless steel machining. If you have a RFQ or want to know more on stainless steel CNC machining, pls feel free to contact us!

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