What is 1.4418 Stainless Steel?
Apr 02, 2026
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1.4418 stainless steel, commonly known as 17-4PH or UNS S17400, is a martensitic precipitation-hardening stainless steel that combines high strength, good corrosion resistance, and excellent toughness through a simple heat treatment process. It achieves its properties by precipitating copper-rich phases within a martensitic matrix, offering a unique combination of fabricability in the solution-treated condition and high strength after aging. This makes it one of the most widely used precipitation-hardening stainless steels across aerospace, chemical processing, nuclear, and high-performance mechanical applications.
This versatile high-strength grade is identified across global standards.
| Standard | Equivalent Grade |
|---|---|
| EN (Europe) | 1.4418 |
| ASTM/AISI (USA) | 17-4PH, UNS S17400 |
| JIS (Japan) | SUS630 |
| Common Name | 17-4PH, Grade 630 |
Its composition includes copper for precipitation hardening and niobium/tantalum for grain refinement and carbide stabilization.
| Element | C | Si | Mn | P | S | Cr | Ni | Cu | Nb+Ta |
|---|---|---|---|---|---|---|---|---|---|
| Content (%) | ≤ 0.07 | ≤ 1.0 | ≤ 1.0 | ≤ 0.04 | ≤ 0.03 | 15.0 - 17.5 | 3.0 - 5.0 | 3.0 - 5.0 | 0.15 - 0.45 |
Mechanical properties vary significantly with heat treatment condition (e.g., Condition A, H900, H1025, H1150).
| Condition | Yield Strength (Rp0.2) | Tensile Strength (Rm) | Elongation (A) | Hardness (HRC) |
|---|---|---|---|---|
| Solution Treated (A) | ~ 550 MPa | ~ 900 MPa | ~ 15% | ~ 32 HRC |
| H900 (480°C age) | ~ 1170 MPa | ~ 1310 MPa | ~ 10% | ~ 44 HRC |
| H1025 (550°C age) | ~ 1070 MPa | ~ 1170 MPa | ~ 12% | ~ 38 HRC |
| H1150 (620°C age) | ~ 790 MPa | ~ 1000 MPa | ~ 12% | ~ 33 HRC |
Key Characteristics and Applications of 1.4418 / 17-4PH
High Strength-to-Weight Ratio: Achieves tensile strengths over 1300 MPa after aging, far exceeding standard austenitic and martensitic stainless steels, allowing for lightweight, high-performance designs.
Good Corrosion Resistance: Offers corrosion resistance similar to Type 304 stainless steel in many environments, suitable for moderate corrosive conditions including marine atmospheres, chemical processing, and food handling.
Precipitation Hardening: Can be machined in the solution-treated (softer) condition and then aged to achieve high strength with minimal distortion, excellent for complex precision components.
Excellent Fatigue Properties: Good fatigue strength makes it suitable for rotating and reciprocating components in demanding applications.
Primary Applications:
Aerospace: Landing gear components, turbine blades, fasteners, actuators, and structural parts.
Chemical & Petrochemical: Valves, pump shafts, fittings, mixers, and reactor components.
Oil & Gas: Downhole tools, wellhead components, blowout preventers, and instrument housings.
Nuclear Industry: Control rod mechanisms, valve components, and structural parts.
Medical: Surgical instruments and dental tools.
Food Processing: Equipment requiring strength and cleanability.
Paper Industry: Doctor blades, cutter bars, and wear components.
How does the heat treatment process work for 17-4PH (1.4418)?
The process involves two main steps. First, the material is solution treated at around 1040°C and rapidly cooled (air or oil quench), resulting in a soft, low-strength, martensitic structure (Condition A) that is easy to machine. Second, it undergoes aging (precipitation hardening) at a lower temperature (e.g., 480°C for H900, 550°C for H1025, 620°C for H1150). This causes fine copper-rich precipitates to form within the martensitic matrix, dramatically increasing strength and hardness. Different aging temperatures produce different strength-toughness combinations: lower temperatures (H900) give maximum strength and hardness, intermediate temperatures (H1025, H1075) give a balanced combination, and higher temperatures (H1150) give optimum toughness and stress corrosion cracking resistance.
What are the machining considerations for 1.4418 stainless steel?
It is most commonly machined in the solution-treated (Condition A) state, where it has a machinability rating similar to Type 304 (approximately 45% of B1112 steel). After aging to higher strength conditions (like H900), machining becomes significantly more difficult and abrasive, requiring harder tool materials (carbide or ceramic), reduced speeds, and adjusted parameters. Good practice is to perform most machining prior to the final aging treatment, then finish grind if necessary after aging. For complex parts, rough machining in Condition A, stress relieving, finish machining, and final aging may be employed to maintain dimensional accuracy.
Looking for a Reliable Supplier of 1.4418 / 17-4PH Stainless Steel?
GNEE Steel supplies high-strength 17-4PH (1.4418) stainless steel in bar, plate, forging, wire, and precision ground forms, available in various heat-treated conditions (A, H900, H1025, H1150) to meet your specific design requirements. We provide full material certification (EN 10204 3.1) and processing support including cutting, machining, grinding, and heat treatment services. If you have any requirements, please feel free to contact us.
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