Stainless Steel - Grade 17-4 (UNS S17400)

Stainless steels are known as high-alloy steels. They contain about 4-30% of chromium. They are further divided into martensitic, austenitic, and ferritic steels. Another group of stainless steels are known as precipitation-hardened steels. They are a combination of austenitic and martensitic steels.

Grade 17-4 stainless steel is the most widely used steel of the precipitation hardening grade steels. It has high toughness, strength, and corrosion resistance.

Chemical Composition

The following table shows the chemical composition of grade 17-4 stainless steel.

Element Content (%)
Iron, Fe 73
Chromium, Cr 15.0 - 17.5
Nickel, Ni 3.0 - 5.0
Copper, Cu 3.0 - 5.0
Manganese, Mn 1.0
Silicon, Si 1.0
Tantalum, Ta 0.45
Niobium, Nb (Columbium, Cb) 0.45
Nb + Ta 0.15 - 0.45
Carbon, C 0.070
Phosphorous, P 0.040
Sulfur, S 0.030

Physical Properties

The physical properties of grade 17-4 stainless steel are given in the following table.

Properties Metric Imperial
Density 7.75 g/cm3 0.280 lb/in³

Mechanical Properties

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

Properties Metric Imperial
Shear modulus 77.4 GPa 11200 ksi
Elastic modulus 190-210 GPa 27557-30458 ksi
Poisson's ratio 0.27-0.30 0.27-0.30
Hardness, Brinell 352 352
Hardness, Knoop (estimated from Rockwell C) 363 363
Hardness, Rockwell C 36 36
Hardness, Vickers (estimated from Rockwell C) 349 349

Thermal Properties

The following table outlines the thermal properties of grade 17-4 stainless steel.

Properties Metric Imperial
Thermal expansion co-efficient (@ 21-93°C/69.8-199°F) 10.8 µm/m°C 6.00 µin/in°F
Thermal conductivity ( for condition H 900 at 149ºC. 22.6 W/mK for H 900 at 482ºC) 17.9 W/mK 124 BTU in/hr.ft².°F

Other Designations

Other designations that are equivalent to grade 17-4 stainless steel are listed in the following table.

AISI 630 ASTM A693 (630) AMS 5342 MIL-S-81506
AMS 5604 ASTM A705 (630) AMS 5343 SAE J467 (17-4PH)
AMS 5622 MIL C-24111 AMS 5344 ASME SA705
AMS 5643 MIL P-47183 AMS 5355 ASME SA564
ASTM A564 (630) MIL S-81591 AMS 5825

Fabrication and Heat Treatment

Machinability

Grade 17-4 stainless steel can be machined in the annealed condition. This alloy has long and gummy chips. Before final hardening, post machining solution treatment is needed if it is machined in the H1150M condition.

Forming

Grade 17-4 stainless steel can be formed mildly.

Welding

Grade 17-4 stainless steel can be welded using common fusion and resistance welding methods. Oxyacetylene welding method is not preferred for welding this alloy.

Heat Treatment

Grade 17-4 stainless steel is soaked at 1038°C (1900°F) for 30 min and cooled below 16°C (60°F) for complete martensite transformation in the condition A. The condition A material is treated at 482°C (900°F) for 1 h followed by cooling. Solution treated material is soaked for 4 h at specific temperature in H925, H1025, H1075, H1100, and H1150 conditions followed by cooling in air.

Solution treated material is soaked at 760°C (1400°F) for 2 h in the H1150M condition followed by cooling. It is again heated at 620°C (1150°F) for 4 h followed by cooling.

Forging

Grade 17-4 stainless steel is forged at 1010°C (1850°F). Before performing this process, it is soaked at 1177°C (2150°F). Post-work solution treatment should be performed before final hardening.

Hot Working

Grade 17-4 stainless steel can be hot worked using common processes. It is treated at 1038°C (1900°F). Post-work solution treatment should be performed before final hardening.

Cold Working

Grade 17-4 stainless steel can be cold worked using common techniques in spite of its high initial yield strength.

Annealing

Grade 17-4 stainless steel is annealed at 1038°C (1900°F) for 0.5 h followed by cooling rapidly.

Hardening

Grade 17-4 stainless steel has high ductility, and can be formed using all conventional techniques. Powerful equipments are required for forming this alloy because it is stronger than the regular steel. Heavy-duty lubricants are used during cold working.

Applications

Grade 17-4 stainless steel is used in the following applications:

  • Nuclear reactor
  • Aircraft and gas turbines
  • Oil field
  • Chemical process components
  • Paper mill

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