Type 347 stainless steel has slightly improved corrosion resistance over type 321 stainless steel in strongly oxidizing environments. Type 347 is stabilized with columbium, it is preferable for aqueous and low temperature environments due to its good resistance to intergranular attack. Both 347 and 321 offer good resistance to polythionic acid stress corrosion cracking, encountered in oil refineries. The high temperature oxidation resistance of 347 is similar to that of 304 stainless steel. Useful to 1500°F. 
Often in many product forms, the grain size and carbon content can meet both the 347S and 347H requirements. Appropriate weld fillers are AWS ER347 bare wire and E347 covered electrodes.

Chemistry

Specifications

AMS 5512, AMS 5646, AMS 5680
ASME SA 240
ASTM A 269, ASTM A 479
ASTM A262 Practice E
MSRR 5632
PWA 300, PWA F17 LCS
UNS S34700, UNS S34709
W. Nr./EN 1.4550

Inventory

347 Coil, 347 Plate, 347 Round Bar, 347 Sheet, 347 Weld Wire

Common Trade Names

347H, 347 Stainless

Features

· Good creep strength up to 1500°F

· Maintains good corrosion resistance in applications where the temperature is between 800°F and 1500°F.

· Good resistance to intergranular corrosion in the as welded condition.

Applications

· Oil Refineries

· Fluid catalytic cracking units (FCC)

· Hanger rods

· Recuperator tube sheets, shell, supports

· Especially where temperatures exceed 550°F and resistance to sulfidation is needed

· Fired heater tubes

· Distributor trays and thermowells

· Equipment in and around reactors (good resistance to polythionic acid)

Physical Properties

Density: 0.286 lb/inch3 
Melting Point: 2550 - 2635°F

* 70°F to indicated temperature.

Mechanical Properties

Minimum Specified Properties, ASTM A 240
Typical Tensile and Impact Properties