1.4418 Stainless Steel — Specs & Applications

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.

Standard	Equivalent Grade
EN (Europe)	1.4418
ASTM/AISI (USA)	17-4PH, UNS S17400
JIS (Japan)	SUS630
Common Name	17-4PH, Grade 630

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

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

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.

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.

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.

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.

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.