Stainless Steel - Grade 309S (UNS S30908)

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 called as high-alloy steels. Due to the presence of large amounts of chromium in the range of 4 to 30%, they have high corrosion resistance than other steels. Stainless steels are classified into martensitic, ferritic and austenitic based on their crystalline structure. However, stainless steels present in the form of a combination of martensitic and austenitic steels are known as precipitation-hardened steels.

The following datasheet will provide more details about grade 305 stainless steel, which has high resistance to heat and corrosion.

Chemical Composition

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

Element Content (%)
Iron, Fe 60
Chromium, Cr 23
Nickel, Ni 14
Manganese, Mn 2
Silicon, Si 1
Carbon, C 0.080
Phosphorous, P 0.045
Sulfur, S 0.030

Physical Properties

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

Properties Metric Imperial
Density 8 g/cm3 0.289 lb/in³
Melting point 1454°C 2650°F

Mechanical Properties

The mechanical properties of annealed grade 309S stainless steel are displayed in the following table.

Properties Metric Imperial
Tensile strength, ultimate 620 MPa 89900 psi
Tensile strength, yield (0.2%) 310 MPa 45000 psi
Izod impact 120 - 165 J 88.5 - 122 ft-lb
Modulus of elasticity 200 GPa 29000 ksi
Shear modulus 77 GPa 11200 ksi
Poissons ratio 0.3 0.3
Elongation at break (in 50 mm) 45% 45%
Hardness, Brinell (converted from Rockwell B hardness) 147 147
Hardness, Knoop (converted from Rockwell B hardness) 164 164
Hardness, Rockwell B 85 85
Hardness, Vickers (converted from Rockwell B hardness) 169 169

Thermal Properties

The following table outlines the thermal properties of grade 309S stainless steel.

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 that are equivalent to grade 309S stainless steel include the following:

  • AMS 5523
  • AMS 5574
  • AMS 5650
  • ASTM A167
  • ASTM A213
  • ASTM A240
  • ASTM A249
  • ASTM A276
  • ASTM A312
  • ASTM A314
  • ASTM A473
  • ASTM A479
  • ASTM A511
  • ASTM A554
  • ASTM A580
  • ASTM A813
  • ASTM A814
  • DIN 1.4833

Fabrication and Heat Treatment

Machinability

Machining of grade 309S stainless steel is similar to that of grade 304.

Welding

Grade 309S stainless steel can be welded using most of the resistance and fusion methods. Oxyacetylene welding is not preferred for this steel.

Hot Working

Hot working of grade 309S stainless steel can be done at 1177°C (2150°F) and reheated at 982°C (1800°F). This process is followed by rapid cooling to obtain maximum corrosion resistance.

Cold Working

Grade 309S stainless steel can be drawn, headed, upset and stamped, although this steel has high work hardening rate. However, it has be fully annealed after cold-working to reduce internal stress.

Annealing

Grade 309S stainless steel can be annealed at temperature ranging from 1038 to 1121°C (1900 to 2050°F) and then quenched with water.

Hardening

Grade 309S stainless steel is unresponsive to heat treatment. The hardness and strength of the steel can be increased through cold working.

Applications

The following are the major applications of grade 309S stainless steel:

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


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