Stainless Steel Grade 17-4 (UNS S17400)

Stainless steel grade 17-4 is a widely used precipitation hardening grade. Although soft and pliable in the solution annealed condition, it possesses good properties with a single precipitation or aging treatment. This material has high harness, good corrosion resistance, toughness, strength, and high quality mechanical properties at temperatures up to 315°C (600°F). It is a preferred choice of engineers and designers due to all these qualities.

The grade 17-4 stainless steel bar is also known as 17-4 PH, UNS S17400, and Grade 630. It is an age-hardening martensitic alloy. Quick hardening can be achieved in a short-time using low-temperature treatment.

The following datasheet provides an overview of grade 17-4 stainless steel.

Chemical Composition

The chemical composition of grade 17-4 stainless steel is outlined in the following table.

Element Content (%)
Chromium, Cr 15-17.5
Nickel, Ni 3-5
Copper, Cu 3-5
Silicon, Si 1 max
Manganese, Mn 1 max
Niobium, Nb 0.15-0.45
Niobium+Tantalum 0.15-0.45
Carbon, C 0.07 max
Phosphorous, P 0.04 max
Sulfur, S 0.03 max
Iron, Fe Remainder

Mechanical Properties

The mechanical properties of grade 17-4 stainless steel are displayed in the following table.

Properties Metric Imperial
Tensile strength 1030 MPa 149000 psi
Yield strength (@strain 0.200 %) 760 MPa 110000 psi
Elongation at break 8% 8%
Hardness, Rockwell C 33 33

Other Designations

Equivalent materials to grade 17-4 stainless steel are given below.

AISI 630 AMS 5604 AMS 5622 AMS 5643 ASTM A564 (630)
ASTM A693 (630)
ASTM A705 (630)
MIL C-24111
MIL P-47183

Manufacturing Process

The machining of grade 17-4 stainless steel produces long, gummy chips. It can be machined in the annealed condition as well; however, before hardening takes place, it is recommended that post machining solution treatment of parts is performed. Grade 17-4 can only be mildly formed.

It can be welded using common fusion and resistance methods. It is advisable not to use the oxyacetylene welding method. The recommended filler metal is AWS E/ER630. Heat treatment requires this material to be soaked at 1038°C (1900°F) for 30 min and cooled below 16°C (60°F) for complete martensite transformation. For forging, the material has to be pre-soaked for 1 h at 1177° C (2150°F). Grade 17-4 should not be worked below 1010°C (1850°F). Post-work solution treatment has to be performed before the final hardening step.

Grade 17-4 PH can be easily hot worked and cold worked using the traditional methods. Similarly, hardening can also be done easily using the traditional methods; however, due to its stronger quality than many other steels, powerful machines are required. Annealing is performed at 1038°C (1900°F), then held for 1/2 h, and finally rapidly cooled.


Grade 17-4 stainless steel is applied in the following products.

  • Gate valves
  • Aircraft structures, accessories, engine parts
  • Chemical processing equipment
  • Food processing machinery
  • Valve stems, balls, bushings, seats
  • Pulp & paper mill equipment
  • Springs
  • Turbine blades
  • Valves
  • Propeller shafts
  • Aircraft and gas turbines
  • Nuclear reactor
  • Paper mill
  • Chemical process components
  • Castings
  • Air spray guns
  • Bearings
  • Boat fittings
  • Fasteners
  • Gears
  • Golf club heads
  • Molding dies
  • Nuclear waste casks
  • Precision rifle barrels
  • Pressure sensor diaphragm
  • Hardware
  • Load cells
  • Dental components
  • Pump impeller shafts
  • Sailboat self steering systems
  • Pump shafts, plungers


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  1. Ralph Kennedy Ralph Kennedy United States says:

    Will ss bolts hold their torque

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