17-4 PH (AISI 630) is a martensitic precipitation-hardening stainless steel delivering ultra-high yield strength (up to 1170 MPa) paired with excellent corrosion resistance comparable to 304.
Engineering Specifications & Parameters
Density
7.75 g/cm³
Hardness (H900)
40 - 45 Rockwell C (HRC)
Tensile Strength
1310 MPa (190,000 psi)
Thermal Expansion
10.8 μm/m·°C
Machinability Rating
48% (Condition A) / 35% (H900)
Yield Strength (H900)
1170 MPa (170,000 psi)
Material Overview & Heat Treatment States
17-4 PH contains 17% chromium, 4% nickel, and 4% copper. It is commonly machined in Condition A (Solution Annealed, ~30 HRC) and subsequently age-hardened to H900, H1025, or H1150 (up to 44 HRC) with minimal volumetric distortion.
Machining Feeds & Speeds
Condition A (Annealed): Cutting speed 80 – 130 m/min with TiAlN-coated carbide.
Coolant Protocol: High-pressure emulsion (8-10% oil concentration) to evacuate tough chips and prevent premature flank wear.
Frequently Asked Questions
Should 17-4 PH be machined before or after heat treatment?
Rough and semi-finish machining is typically performed in Condition A. Because age hardening involves minimal distortion (0.05%), final critical dimensions can often be machined prior to aging.
What tool coating is recommended for 17-4 PH milling?
Multi-layer AlTiN or AlCrN coatings provide high hot hardness and oxidation resistance up to 900°C.
