Material Machining Views: 8

Differences between machining stainless steel and carbon steel, and parameter adjustment: Stainless and carbon steel are the two most common metals, but machinability differs greatly. Comparison: 1) Tack - stainless is tacky: welds, BUE; carbon is less tacky (low carbon also welds, but less than stainless); 2) Thermal conductivity - stainless conducts poorly (1/3-1/4 of carbon): heat concentrates at the edge, tools overheat; carbon conducts well; 3) Work hardening - stainless hardens severely (50%-100% above base): accelerates wear; carbon hardens lightly; 4) Strength - stainless is strong and tough: high cutting force; carbon is weaker: low force; 5) Hardness - stainless medium (HB200-300); carbon ranges widely (HB150-500+); 6) Tool life - stainless shortens life (1/3-1/2 of carbon); carbon gives long life. Tool selection: 1) carbon - standard HSS or cobalt HSS, TiN or TiAlN; 2) stainless - MUST use cobalt HSS (HSS-E) or carbide; AlCrN or TiAlN recommended (heat-resistant, anti-welding); standard HSS wears extremely fast - not recommended. Parameter adjustment (cobalt HSS 90-degree countersink): 1) speed - carbon 800-1500rpm, stainless 400-800rpm (about 50% lower); 2) feed - carbon 0.1-0.2mm/rev, stainless 0.05-0.1mm/rev (about 50% lower); 3) fluid - carbon: emulsion or semi-synthetic; stainless: EP emulsion or stainless-specific fluid, 8%-12%, flood; 4) depth - carbon: large OK; stainless: small, stepped, avoid the hardening layer. Extra notes for stainless: 1) very sharp tools - dull tools worsen hardening; re-sharpen promptly; 2) never dry-cut - extremely short life; 3) avoid extremes - below 200rpm forms BUE, above 1000rpm overheats; find the right range; 4) reduce impact - tough but hardening-prone: avoid impact and interrupted cutting (or lower parameters); 5) clean promptly - long stringy chips tangle. Notes for carbon: 1) low carbon (Q235, 20) - watch welding; avoid low speed; 2) medium carbon (45) - easiest; parameters can be aggressive; 3) high carbon or hardened steel - carbide. Summary: stainless is harder - tacky, poor conductivity, severe hardening; use better tools (cobalt HSS + AlCrN), cut speed and feed about 50%, generous cooling. Carbon machines easily with ordinary tools and parameters. Our cobalt HSS countersinks are optimized for stainless and other hard materials - ask us.