Material Machining Views: 8

Differences when machining different carbon steels and tool selection: Carbon steel is the most common metal; it is divided by carbon content into low, medium and high carbon. 1) Low carbon (Q235, A3, 20 steel, 10 steel - under 0.25% C) - characteristics: soft, ductile, tacky, welds easily, visible work hardening; low strength, good toughness. Machinability: fair; the main issue is welding and BUE - finish is hard to control. Use cobalt HSS + TiN or TiAlN, 800-1500rpm, feed 0.1-0.2mm/rev, semi-synthetic fluid, sharp tools; avoid low speed (50-200rpm forms BUE). 2) Medium carbon (45, 40, 35 steel - 0.25%-0.6% C) - characteristics: medium strength and hardness, good machinability, less tacky than low carbon - the easiest steel to machine. 45 steel is the most common medium-carbon grade with good all-round performance. Machinability: good; moderate force, good chip removal, easy finish control. Use cobalt HSS + TiAlN or standard HSS, 600-1200rpm, feed 0.08-0.15mm/rev, emulsion or semi-synthetic. 3) High carbon (T8, T10, 65Mn, 60Si2Mn - over 0.6% C) - characteristics: hard, wear-resistant, brittle; good machinability annealed, very hard after hardening. Annealed: cobalt HSS + TiAlN, 500-1000rpm, feed 0.06-0.12mm/rev; hardened (HRC45+): carbide or CBN, low speed, small feed. 4) Q235 and A3 - both low carbon; Q235 is the new standard name, A3 the old - essentially the same machinability. 5) 20 steel - low carbon, slightly better than Q235; often carburized - hard surface after carburizing/hardening. Summary: medium carbon (45) is easiest; low carbon (Q235, 20) is tacky - watch BUE; high carbon machines well annealed but needs carbide when hardened. Carbon steel is the most common material - cobalt HSS + TiAlN with sensible parameters gives quality chamfers.