17-4 PH Stainless Steel



17-4 PH Stainless Steel is a precipitation hardening martensitic stainless steel with Copper and Niobium. The grade combines high strength, hardness (up to 572°F / 300°C), and corrosion resistance. Mechanical properties can be optimized with heat treatment. Very high yield strength up to 1100-1300 MPa (160-190 ksi) can be achieved. The grade should not be used at temperatures above 572°F (300°C) or at very low temperatures. It has adequate resistance to atmospheric corrosion or in diluted acids or salts where its corrosion resistance is equivalent to Alloy 304 or 430.

    Chemical Composition:

  • Carbon 0.04%
  • Manganese 0.70%
  • Chromium 16.50%
  • Nickel 4.50%
  • Copper 3.30%
  • Niobium 0.30%

    Typical Applications:

  • Food Industry
  • Paper Industry
  • Aerospace Industry
  • Mechanical Components

Mechanical Properties

Room temperature properties (longitudinal direction)
Guaranteed values (ASTM A693 hot rolled plates); thickness from 3/16″ up to 3″.

Heat
treatment
YS 0.2%
N/mm
UTS
N/mm
YS 0.2%
ksi
UTS
ksi
El%
Min.Typ.Min.Typ.Min.Typ.Min.Typ.Min.Typ.
A1070120711701310155175170190814
B79093196510341151351401501017

A: hardening 925°F (496°C) – 4 hours – air cooling
B: hardening 1100°F (593°C) – 4 hours – air cooling
2 examples of heat treatments that may be applied.

Elevated temperature properties
Minimum guaranteed values following EN 10088 hot rolled plates. The EN guaranteed values are valid for a thickness from 3/16″ up to 3″.

Temperature °F
Temperature °C
212
100
302
150
392
200
482
250
572
300
YS 0.2%N/mm_730710690670650
ksi1061031009795

Heat treatment : hardening 1094°F (590°C) – 4 hours – air cooling. 1 example of heat treatments that may be applied.

Processing

Hot Forming

Hot forming should be carried out in a temperature range of 1742-2192°F (950-1200°C). A full heat treatment including solution annealing, cooling lower than 76°F (25°C) and aging at the required temperature must be made after hot forming (function of the requested mechanical properties).

Cold Forming

Cold forming can be performed only to a limited extent and only on plates in the fully softened condition. Stress corrosion resistance is improved by re-aging at the precipitation hardening temperature after cold working.

The following processes may be performed: rolling, bending, hydroforming, etc. (fully softened conditions).

Cutting
Thermal cutting (plasma, thermal sawing, etc.). Due to the HAZ, the grade requires a suited cutting process. After cutting, grinding is necessary to eliminate the oxide formed layer.

Mechanical cutting (shearing, stamping, cold sawing, etc).

Welding

Alloy 17-4 PH can be welded by the following welding processes: SMAW, GTAW, PAW and GMAW. SAW should not be used without preliminary testing (to check freedom of cracks and toughness of the weld metal).

Due to a ferrite delta primary type of solidification, the hot cracking risk of the weld metal or the HAZ is reduced.

Generally, no preheating must be done and interpass temperature must be limited to 248°F (120°C). The better toughness is obtained in the weld after a complete heat treatment (solution annealing + precipitation hardening).

Due to the martensitic microstructure, a low oxygen content in the weld metal is preferable to increase ductility and toughness. To avoid cold cracking, the introduction of hydrogen in the weld must be limited.

Alloy 17-4 PH can be welded with homogeneous filler metals such as E 630 (AWS A5.4) electrodes and ER 630 (AWS A5.9) wires.

Austenitic filler material can be used when the mechanical properties of 17-4 PH steel are not required in the weld and, in this case, no post-weld heat treatment must be applied.

Machining

Alloy 17-4 PH can be machined in both solution treated and precipitation hardened conditions. Machining condition may vary according to the hardness of the material. High speed steel tools or preferably carbide tools with standard lubrification are normally used. If very stringent tolerances are required, it is necessary to take into account the dimensional changes during heat treatment.