Stainless steel is more than just a material; it’s full of contradictions. It’s prized for its corrosion resistance and smooth surface, but it’s also notorious for turning machining shops into battlefields of broken tools, deformed parts, and frustrated engineers. But what if you could predict these characteristics and turn them to your advantage? Let’s clear up the confusion and explore the typical machining properties of stainless steel and possible strategies to master them.
1. Severe Work Hardening
In the world of stainless steels, work hardening is particularly pronounced in austenitic and duplex (austenitic-ferritic) grades. This is mainly due to their high plasticity, which leads to significant lattice distortion during plastic deformation, thereby greatly enhancing the material’s strength. Furthermore, the lower stability of austenitic stainless steel means that under cutting stresses, some of it may transform into martensite, further exacerbating work hardening. In addition, compound impurities found in stainless steel tend to break down under the heat generated during cutting, forming a dispersed hardening layer that complicates the machining process.
2. High Cutting Force Requirements
When cutting stainless steel, its high plasticity results in large amounts of plastic deformation. For instance, austenitic stainless steel can have an elongation that exceeds that of conventional 45# steel by more than 1.5 times, directly leading to a significant increase in cutting forces. The combined effects of severe work hardening and high thermal strength further raise the resistance to cutting. Moreover, the curling and fracturing of stainless steel chips is challenging, adding extra complexity to the machining process.
3. Elevated Cutting Temperatures
The large degree of plastic deformation and intense friction between the workpiece and the cutting tool generate considerable cutting heat. This heat is concentrated in the cutting zone and at the tool–workpiece interface, where poor heat dissipation can cause a noticeable rise in temperatures. Research indicates that under similar conditions, the cutting temperature for stainless steel can be approximately 200℃ higher than that of 45# steel, imposing stringent thermal resistance requirements on both cutting tools and machine tools.
4. Difficulty in Chip Breaking and a Tendency to Stick
Stainless steel’s inherent high plasticity and toughness mean that its chips do not break easily. In the high-temperature, high-pressure environment of machining, the metal tends to adhere strongly to the tool, often leading to built-up edge formation. This not only accelerates tool wear but may also compromise the quality of the machined surface. Low-carbon martensitic stainless steels, in particular, exhibit this adhesion tendency more prominently, requiring careful selection of cutting parameters and tool materials.
5. Accelerated Tool Wear
During the machining of stainless steel, the affinity between the material and the tool surface often results in both adhesive and diffusion wear. This can lead to characteristic “moon-shaped” depressions on the tool’s rake face along with tiny chipping and edge breaks. Additionally, the presence of extremely hard carbide particles (such as TiC) in stainless steel can scratch the tool surface during cutting. When combined with the challenges of work hardening, these factors contribute to accelerated tool wear, ultimately increasing both processing costs and production time.
Conclusion
The unique physical and chemical properties of stainless steel present several challenges during machining. Understanding these characteristics is key to selecting the right processing techniques and cutting tools, which in turn can improve both efficiency and product quality. For companies and professionals working in the stainless steel processing industry, mastering these insights is essential for enhancing competitiveness. We hope this article serves as a valuable resource, helping you achieve superior results in your stainless steel machining projects.