Stainless Steel 17-4PH

The alloy offers various attractive performance characteristics. The material possesses good stress corrosion resistance, high fatigue resistance and resistance to galling. 17-4PH is readily weldable by all conventional methods, and there is no requirement for pre or post-heating, which is usually the case for standard hardenable stainless steels. A single, low-temperature heat treatment will harden the alloy.

Alloy 17-4PH (UNS S17400), Type 630, is a chromium-nickel-copper precipitation-hardening martensitic stainless steel with an addition of niobium. 17-4PH combines high strength and hardness with good corrosion resistance. The alloy is furnished in the solution annealed condition (Condition A). It should not be used at temperatures above 572°F (300°C) or for cryogenic service. Optimal mechanical properties can be obtained by subjecting the alloy to age hardening heat treatments. Heat treatment in the 900°F (482°C) range produces the highest strength.

The corrosion resistance of Alloy 17-4PH is comparable to 304 stainless steel in most environments, and is generally superior to the 400 series stainless steels. It is used in applications where the combination of moderate corrosion resistance and unusually high strength are required.Alloy 17-4PH can be easily welded and processed by standard shop fabrication practices. It is magnetic.

Alloy 17-4PH Chemical Analysis

Alloy 17-4PH Physical Properties

Density:  0.280 Ibs/in3, 7.75 g/cm3

Specific Heat: 0.11 BTU/lb-°F @ 70°F, 460 J/kg-°C @ 20°C

Melting Range: 2560 – 2625°F, 1404 – 1440°C

Alloy 17-4PH Equivalent Grades

Alloy 17-4PH Mechanical Properties

Alloy 17-4PH ASTM Specification

Corrosion Resistance：

The corrosion resistance of Alloy 17-4PH is comparable to 304 stainless steel in most environments, and is generally superior to the 400 series stainless steels. It is used in applications where the combination of moderate corrosion resistance and unusually high strength are required. Alloy 17-4PH has corrosion resistance comparable to 304L in some chemical, dairy, food, paper and petroleum applications. 

Alloy 17-4PH in the solution-annealed condition (Condition A) should not generally be put in service. The alloy is subject to brittle fractures and more sensitive to chloride stress corrosion cracking than the aged material. If risks of chloride stress corrosion cracking are present the higher aging temperatures should be selected over 1022°F (550°C), preferably 1094°F(590°C). 1022°F (550°C) is the recommended tempering temperature in chloride service. 1094°F (590°C) is preferred in H2S media. Alloy 17-4PH is subject to crevice corrosion and pitting attack when exposed to stagnant seawater for a duration of time.

Hot Forming：

Heat uniformly at 1742 – 2192°F (950 – 1200°C). A full solution anneal, cooling lower than 76°F (25°C) and aging at the required temperature must occur after hot forming. The post forming heat treatment should be a function of the desired mechanical properties.

Cold Forming：

Alloy 17-4PH has limited cold forming properties. Cold forming can only be undertaken on plates in the fully annealed condition. Stress corrosion resistance is enhanced by re-aging at the precipitation hardening temperature after cold working.

Cutting：

Thermal cutting operations such as plasma cutting should be avoided. Mechanical cutting operations such as bandsaw, abrasive waterjet, shearing and machining are preferred.

Welding：

Alloy 17-4PH can be readily welded by most standard processes including SMAW, GTAW, PAW and GMAW.

Machining：

Alloy 17-4PH can be machined in both the solution treated and precipitation hardened conditions.  Machining characteristics may vary according to the hardness of the metal. High speed tools are acceptable, but carbide tools are preferred. Standard lubrication should be used. Dimensional changes as a result heat treatment  should be taken into account if very stringent tolerances are required.

Features：

High tensile strength and hardness to 600°F

Corrosion resistant

Excellent oxidation resistance to about 1100°F

Creep-rupture strength to 900°F

Stainless Steel 17-4PH Applications：

• Aerospace  —  structural  and  parts

• Biomedical  —  hand  tools

• Chemical Processing

• Food Process Equipment

• Mechanical Components

• Nuclear Waste Processing and Storage

• Oil  and  Gas  Production  —  foils, helicopter deck platforms, etc.

• Pulp  and  Paper  —  paper  mill equipment