17-4 PH Precipitation Hardening Stainless Steel
Comprehensive technical specification for 17-4 PH (UNS S17400) precipitation hardening stainless steel, covering properties, sizing, machinability, defects, and handling for Canadian fabrication and machining operations.
Material Overview & Common Uses
17-4 PH (UNS S17400) is a martensitic precipitation-hardening stainless steel offering high strength (up to 200 ksi tensile in H900 condition), good corrosion resistance comparable to 304, and excellent toughness. It is supplied in the solution-annealed (Condition A) state and then age-hardened by the fabricator to achieve desired mechanical properties. Common Canadian applications include aerospace components (landing gear, brackets), oil & gas valve stems and seats, pump shafts, food processing equipment, medical instruments, and high-performance tooling. Its combination of strength, corrosion resistance, and moderate cost makes it a go-to for demanding industrial parts.
Core Technical Properties & Sizing
| Property / Parameter | Value | Notes |
|---|---|---|
| Chemical Composition – Cr | 15.0–17.5 wt% | Primary corrosion resistance |
| Chemical Composition – Ni | 3.0–5.0 wt% | Austenite stabilizer |
| Chemical Composition – Cu | 3.0–5.0 wt% | Precipitation hardening element |
| Chemical Composition – Nb+Ta | 0.15–0.45 wt% | Grain boundary strengthener |
| Chemical Composition – C | ≤0.07 wt% | Low carbon for weldability |
| Condition A – Tensile Strength | ≤130 ksi (896 MPa) | Solution annealed |
| Condition A – Yield Strength | ≤105 ksi (724 MPa) | Solution annealed |
| Condition A – Elongation | ≥6% | Solution annealed |
| Condition A – Hardness | ≤38 HRC | Solution annealed |
| H900 – Tensile Strength | ≥190 ksi (1310 MPa) | Aged at 900°F |
| H900 – Yield Strength | ≥170 ksi (1172 MPa) | Aged at 900°F |
| H900 – Elongation | ≥10% | Aged at 900°F |
| H900 – Hardness | 40–48 HRC | Aged at 900°F |
| Plate Thickness (Standard) | 0.125″ to 1.000″ | 3.18–25.4 mm |
| Plate Width (Standard) | 48″ or 60″ | 1219 or 1524 mm |
| Plate Length (Standard) | 96″ or 120″ | 2438 or 3048 mm |
| Bar/Round Diameters | 0.250″ to 12.000″ | 1/8″ increments, 12′ random |
| Hex Bar (across flats) | 0.375″ to 2.000″ | Various lengths |
| Sheet Thickness | 0.060″ to 0.187″ | 1.52–4.76 mm |
| Thickness Tolerance (sheet ≤0.060″) | ±0.005″ | Per ASTM A693 |
| Thickness Tolerance (0.061–0.125″) | ±0.007″ | Per ASTM A693 |
| Thickness Tolerance (0.126–0.250″) | ±0.010″ | Per ASTM A693 |
| Width Tolerance (sheared plate) | +0.125″/–0.000″ | Per ASTM A693 |
| Length Tolerance | +0.250″/–0.000″ | Per ASTM A693 |
| Flatness (annealed) | 0.005″ per foot | Per ASTM A693 |
| Heat Treatment Options | H900, H925, H1025, H1075, H1100, H1150 | Different strength/toughness balances |
Machinability, Tooling & Feeds
| Operation | Speed (SFM) | Feed | Notes |
|---|---|---|---|
| Turning – Condition A | 200–300 SFM | 0.005–0.015 IPR | Depth of cut 0.050–0.150″; carbide C2/C3, positive rake |
| Milling – Condition A | 150–250 SFM | 0.003–0.008 IPT | Carbide inserts; rigid setup required |
| Drilling – Condition A | 80–120 SFM | 0.002–0.005 IPR | Cobalt or carbide; 135° split point; high-pressure coolant |
| Turning – Hardened (H900–H1150) | 100–150 SFM | 0.003–0.008 IPR | Reduce speeds 30–50%; CBN or ceramic for finishing |
| Milling – Hardened (H900–H1150) | 80–125 SFM | 0.002–0.005 IPT | Use CBN inserts; light depths |
| Drilling – Hardened (H900–H1150) | 40–70 SFM | 0.001–0.003 IPR | Carbide drills; peck cycle recommended |
| Threading – Condition A | Single-point or thread milling | — | Avoid taps; work-hardening risk |
| Threading – Hardened | Single-point or thread milling | — | CBN or carbide tooling; reduced speeds |
| Grinding | 5500–6500 SFPM wheel speed | Light infeed | Aluminum oxide or CBN wheels; frequent dressing |
Machinability rating in Condition A is approximately 45–50% of AISI 1212. In hardened conditions, machinability drops to 25–35%. Use high-pressure coolant (1000+ psi) for all operations.
Common Defects & Quality Control
| Defect | Description | QC Method |
|---|---|---|
| Surface cracking | Improper heat treatment, especially H900 if not fully solution annealed | Dye penetrant inspection; verify heat treat cycle |
| Laps and seams | Linear surface discontinuities from hot rolling | Visual inspection; magnetic particle test |
| Decarburization | 0.005–0.015″ deep loss of carbon on bar surfaces | Microhardness traverse; metallographic etch |
| Centerline porosity | Voids in larger diameter bars (>6″) | Ultrasonic testing (UT) per ASTM A388 |
| Grain boundary carbide precipitation | Overaging or slow cooling from aging temperature | Metallographic examination; verify cooling rate |
| Distortion during aging | Non-uniform heating or residual stresses | Dimensional inspection; stress relief before aging |
Quality control checks: Rockwell C hardness on every heat lot, magnetic permeability test (17-4 PH is magnetic in all conditions), surface finish profilometer (Ra ≤ 63 μin), dye penetrant inspection on critical components. Always request mill test reports (MTR) per ASTM A693 and EN 10204 3.1.
Storage, Handling & Racking Guidelines
Store 17-4 PH in a dry, indoor environment (RH < 60%) to prevent surface oxidation. Do not store directly on concrete floors – use wooden pallets or steel racks with plastic or rubber separators to avoid galvanic corrosion. For plate, rack vertically on edge in A-frame racks with padded supports to prevent scratching and bending. Bar stock should be stored horizontally on cantilever racks with full-length support to avoid sagging (max unsupported span 4′ for 1″ diameter bar). Sheet material should be stored flat on shelves with interleaving paper or plastic film between sheets to prevent surface damage. Keep away from chlorinated solvents and acids. For long-term storage (>6 months), apply a light rust-preventive oil (e.g., LPS-3) and wrap in VCI paper. FIFO rotation is critical – label each bundle with heat number, condition, and date received. Do not stack plate bundles more than 3 high to avoid crushing bottom sheets.