General Properties

Alloy 17-4 is a chromium-copper precipitation hardening stainless steel that is used for applications requiring high strength and a moderate level of corrosion resistance. It is one of the most widely used precipitation hardening grades, as it has high strength hardness up to about 572°F while demonstrating good corrosion resistance in all heat treated conditions. Alloy 17-4 has adequate resistance to atmospheric corrosion or in diluted acid salts where its corrosion resistance is equivalent to Alloy 304 or 430. Alloy 17-4 can be heat treated to a variety of temperatures to develop a wide range of properties. Its mechanical properties can be optimized with heat treatment where very high yield strength up to 180 ksi can be achieved. Alloy 17-4 should not be used at temperatures above 572°F or at very low temperatures.

Specifications: UNS S17400

Applications:

Alloy 17-4 is commonly used for applications requiring high strength and a moderate level of corrosion resistance. Some applications that frequently use Alloy 17-4 include:

• Aircraft
• Nuclear waste casks
• Paper mills
• Oil fields
• Mechanical components
• Chemical process components
• Food industry
• Aerospace

Standards:

• ASTM/ASME: UNS S17400
• EURONORM: X5CrNiCuNb16.4
• AFNOR: Z6CNU17-04
• DIN: 1.4542

Corrosion Resistance:

• Withstands corrosive attacks better than any of the standard hardenable stainless steels.
• Comparable to Alloy 304 in most media.
• Corrosion resistant in some chemical, petroleum, dairy, and food process industries.
• Subject to crevice or pitting attack if exposed to stagnant sea water for any length of time.

Weldability:

• Successfully welded by most common fusion and resistance methods.
• Should not be joined by oxyacetylene welding.
• Generally no pre-heating required.
• Inter-pass temperature must be limited to 248°F.
• Better toughness is obtained in the weld after a complete heat treatment.

Elevated Temperature Use:

• Excellent resistance to oxidation to approximately 1100°F.
• Long-term exposure to elevated temperature can result in reduced toughness in the precipitation hardened conditions.

Processing – Hot Forming:

• To forge, heat uniformly to 2150 / 2200°F and hold for half hour per inch.
• Preferred temperature range for hot forming is at 650-900°F, while the steel is still austenitic.
• To ensure the best condition for the hardening operations, the forgings must be re-heat treated at 1875-1925°F.
• Cool forgings to below 90°F to ensure grain refinement.

Processing – Cold Forming:

• Alloy 17-4 is limited to mild operations since in the annealed (solution treated) condition the material is hard.
• For severe cold working the material should be heat treated to condition H1150. This will help prevent possible cracking.
• Bend radius in excess of 7T is often required.
• To improve stress corrosion resistance after cold forming, re-aging at the precipitation-hardening temperature is recommended.

Machinability:

• Can be machined in both solution-treated and precipitation-hardening conditions.
• Machining conditions may vary with hardness of material.
• High-speed tools or preferably carbide tools with standard lubrication are normally used.

Chemical Properties:

Mechanical Properties:

Physical Properties: