Introduction

Type 309 is an austenitic chromium nickel stainless steel (.08% max carbon).Type 309is employed for parts requiring both corrosion and heat resistance and oxidation resistance up to 2000oF. Strength at elevated temperatures is similar to that of 18-8 Stainless Steels.This alloy posses excellent resistance to oxidation as well as high tensile and creep strengths at elevated temperatures. It is more resistant to marine atmospheres than Type 304.It is generally considered as a heat-resisting alloy.

Chemistry Typical

Carbon: 0.08 max
Manganese: 2.00 max
Silicon: 1.00 max
Chromium: 22.00- 24.00
Nickel: 12.00- 15.00
Molybdenum: 0.75 max
Phosphorus: 0.040 max .
Sulphur: 0.030 max
Copper: 0.75 max
Iron: Balance

Properties: Typical

Ultimate Tensile Strength: 75 KSI min (620 MPA min
Yield Strength (0.2% offset): 30 KSI min (205MPA min)
Elongation: 40% min
Hardness: Rb 95 max

Physical Properties

Density, 0.289 lbs/in3 9.01 g/cm3

Electrical Resistivity, microhm-in (microhm-cm)
68°F (20°C) – 30.7 (78.0)

Specific Heat, BTU/lb/°F
32-212°F (0-100°C): 0.12 (0.50)

Thermal Conductivity, BTU/hr/ft2/ft/°F
At 212°F (100°C): 9.0 (15.6)
At 932°F (500°C): 10.8 (18.7)

Mean Coefficient of Thermal Expansion: in/in/°F
32 – 212°F (0 -100°C): 8.3 x 10-6(14.9)
32 – 600°F (0 -315°C): 9.3 x 10-6(16.7)
32 -1000°F (0 -538°C): 9.6 x 10-6 (17.3)
32 -1200°F (0 -649°C): 10.0x 10-6 (18.0)

Modulus of Elasticity, ksi (MPa)
29.0 x 103 (200 x 103) in tension
11.2 x 103 ( 78 x 103) in torsion

Magnetic Permeability, H = 200 Oersteds, Annealed <1.02 max.

Melting Range, °F (°C) 2550 – 2590 (1399 – 1454)


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.

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.

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

Applications
Grade 309 stainless steel is used in the following applications:
Boiler baffles
Furnace components
Oven linings
Fire box sheets
Other high temperature containers