When selecting cutting tools for machining SUS630 (martensitic precipitation-hardening stainless steel), its heat treatment condition (lower hardness in the solution-treated state and higher hardness in the aged state) must be considered. Tool selection should focus on wear resistance, impact resistance, and chip evacuation performance, as outlined below.
I. Machining in the solution-treated condition (Hardness: 28–32 HRB; good plasticity)
In the solution-treated condition, SUS630 is prone to tool adhesion and exhibits moderate cutting resistance. Tool selection should therefore emphasize anti-adhesion performance and smooth chip evacuation. Tool Material:
Ultra-fine grain cemented carbide (e.g., WC–Co alloys with 6%–8% Co content) is recommended. Suitable ISO grades include P-class (P20, P30) or M-class (M20, M30), which provide a good balance between wear resistance and toughness and are suitable for continuous cutting.
For complex geometries or interrupted cutting, cermet tools (TiCN-based) may be used. These tools feature higher hardness (HRA 93–94) and better anti-adhesion performance than conventional cemented carbide, helping to reduce built-up edge formation.
Coating selection:
TiAlN coatings (high-temperature resistance and oxidation resistance) or AlCrN coatings (excellent anti-adhesion performance) are preferred. A coating thickness of 3–5 μm is recommended due to reduce friction and extend tool life.
Tool geometry parameters:
Rake angle: 8°–12° (to improve sharpness and reduce cutting forces) Relief angle: 6°–8° (to reduce flank wear) Edge honing (edge radius): 0.05–0.1 mm (to prevent edge chipping) Chip grooves: wide and smooth (to prevent chip clogging).

II. Machining in the aged condition (Hardness: 30–45 HRC; high strength)
In the aged condition, the material exhibits high hardness and high cutting resistance, so tool selection should emphasize wear resistance and impact resistance.
Tool Material: Ultra-fine grain cemented carbide with high cobalt content (Co content: 8%–12%) is recommended. Suitable ISO grades include K-class (K10, K20) or M-class (M40), providing a balance between hardness (HRA 90–92) and edge chipping resistance.
For higher hardness ranges (40–45 HRC) or precision machining, cubic boron nitride (CBN) tools (e.g., solid polycrystalline CBN) are recommended. These tools feature very high hardness (above HV 3000) and are suitable for high-speed cutting (cutting speed: 80–150 m/min), ensuring machining accuracy.
For interrupted cutting or large feed machining, ceramic tools (e.g., Al₂O₃ + TiC composite ceramics) may be used, but severe impact should be avoided (due to their high brittleness).
Coating Selection:
Thick TiAlN coatings (5–8 μm) or diamond coatings (PCD; primarily for non-ferrous materials but also effective for high-hardness stainless steel) are recommended to enhance wear resistance and surface lubricity.
Tool Geometry Parameters:
Rake angle: 5°–8° (to reduce impact load on the cutting edge) Relief angle: 8°–10° (to reduce wear) Edge honing (edge radius): 0.1–0.2 mm (to enhance edge strength) Negative rake angle design (to improve tool rigidity).

III. General machining recommendations cutting parameters:
Solution-treated condition: (Cutting speed: 80–120 m/min; feed rate: 0.1–0.2 mm/rev; depth of cut: 2–5 mm) Aged condition: (Cutting speed: 50–100 m/min for cemented carbide or 80–150 m/min for CBN; feed rate: 0.05–0.15 mm/rev; depth of cut: 1–3 mm)
Cooling and Lubrication:
Extreme-pressure emulsions or fully synthetic cutting fluids (used with high-pressure coolant supply at 3–5 MPa) ensuring sufficient cooling in the cutting zone and to reduce friction and tool adhesion are recommended.
Tool Types:
Turning: Indexable inserts (e.g., CNMG and WNMG types for easy and rapid replacement)
Milling and drilling: Fine-pitch end mills (number of flutes: 4–6 to reduce the load per tooth) and cemented carbide twist drills (with internal coolant channels to improve chip evacuation efficiency)
Machining in the solution-treated condition should focus on “anti-adhesion and smooth chip evacuation” (using ultra-fine grain cemented carbide tools in P/M classes with TiAlN coatings), while machining in the aged condition (especially at higher hardness levels) should prioritize “high wear resistance” (using high-cobalt cemented carbide tools in K/M classes or CBN tools, combined with appropriate cutting parameters and cooling strategies), which can effectively improve machining efficiency and tool life.