Stainless Steel - Grade 309 (UNS S30900)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
     Machinability
     Welding
     Hot Working
     Cold Working
     Annealing
     Hardening
Applications

Introduction

Stainless steels are high-alloy steels which have higher corrosion resistance compared to other steels due to the presence of large amounts of chromium. Based on their crystalline structure, they are further divided into ferritic, austenitic, and martensitic steels.

Grade 309 stainless steel has high corrosion resistance and strength compared to 304 stainless steel. The following datasheet gives an overview of grade 309 stainless steel.

Chemical Composition

The following table shows the chemical composition of grade 309 stainless steel.

Element Content (%)
Iron, Fe 60
Chromium, Cr 23
Nickel, Ni 14
Manganese, Mn 2
Silicon, Si 1
Carbon, C 0.20
Phosphorous, P 0.045
Sulfur, S 0.030

Physical Properties

The physical properties of grade 309 stainless steel are given in the following table.

Properties Metric Imperial
Density 8 g/cm3 0.289 lb/in³
Melting point 1455°C 2650°F

Mechanical Properties

The following table outlines the mechanical properties of annealed grade 309 stainless steel.

Properties Metric Imperial
Tensile strength 620 MPa 89900 psi
Yield strength (@ strain 0.200%) 310 MPa 45000 psi
Izod impact 120 - 165 J 88.5 - 122 ft-lb
Shear modulus (typical for steel) 77 GPa 11200 ksi
Elastic modulus 200 GPa 29008 ksi
Poisson's ratio 0.27-0.30 0.27-0.30
Elongation at break (in 50 mm) 45% 45%
Hardness, Brinell 147 147
Hardness, Rockwell B 85 85
Hardness, Vickers (converted from Rockwell B hardness) 169 169

Thermal Properties

The thermal properties of grade 309 stainless steel are displayed in the following table.

Properties Metric Imperial
Thermal expansion co-efficient (@ 0-100°C/32-212°F) 14.9 µm/m°C 8.28 µin/in°F
Thermal conductivity (@ 0-100°C/32-212°F) 15.6 W/mK 108 BTU in/hr.ft².°F

Other Designations

Other designations equivalent to grade 309 stainless steel are included in the following table.

ASTM A167 ASME SA249 ASTM A314 ASTM A580
ASTM A249 ASME SA312 ASTM A358 FED QQ-S-763
ASTM A276 ASME SA358 ASTM A403 FED QQ-S-766
ASTM A473 ASME SA403 ASTM A409 MIL-S-862
ASTM A479 ASME SA409 ASTM A511 SAE J405 (30309)
DIN 1.4828 ASTM A312 ASTM A554 SAE 30309
       

Fabrication and Heat Treatment

Machinability

Grade 309 stainless steel can be machined similar to that of 304 stainless steel.

Welding

Grade 309 stainless steel can be welded using fusion or resistance welding methods. Oxyacetylene welding method is not preferred for welding this alloy.

Hot Working

Grade 309 stainless steel is hot worked at 1177°C (2150°F) followed by reheating at 982°C (1800°F). It can be then quenched rapidly. Post-work annealing can be done to restore its corrosion resistance property.

Cold Working

Grade 309 stainless steel can be headed, upset, drawn, and stamped even though it has high work hardening rate. Annealing is performed after cold working in order to reduce internal stress.

Annealing

Grade 309 stainless steel is annealed at 1038-1121°C (1900-2050°F) followed by quenching in water.

Hardening

Grade 309 stainless steel does not react to heat treatment. Strength and hardness of this alloy can be increased by cold working.

Applications

Grade 309 stainless steel is used in the following applications:

  • Boiler baffles
  • Furnace components
  • Oven linings
  • Fire box sheets
  • Other high temperature containers.

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