These grades are chromium-nickel stainless steels containing columbium and tantalum. The columbium serves to produce a stabilized type of stainless steel which is immune to chromium carbide precipitation. The grades are this recommended for parts fabricated by welding which cannot be subsequently annealed or for parts which must operate in service between 800-1600 degrees F. Type 348 has the lower tantalum and cobalt contents of the two steels, making it suitable for use where the steel is subjected to nuclear irradiation.

Corrosion Resistance:
Excellent. Equivalent to Type 304 and superior to Types 302 or 304 where unannealed weldments are involved or service temperatures in the 800 to 1600 degrees F range. Where service is both corrosive and at elevated temperatures, these grades are superior to Type 321.

Heat Resistance:
Good oxidation resistance in intermettent service to 1600 degrees F and in continuous service to 1700 degrees F. Best suited to service in the 800 to 1600 degrees F range.

Heat Treatment:
Annealing - Heat to 1850-2050 degrees F and cool rapidly for maximum corrosion resistance. Stabilizing - Heat to 1500 to 1650 degrees F for one hour per inch of thickness, then air cool. Stress Relief - After fabrication, hold for one to two hours at 1300 degrees F and air cool.

Welding:
Good characteristics suited to all standard methods. Use Types 347 or 348 filler rodor electrodes. Post-weld annealing is not required.

Typical Applications:
Radioactive systems
Jet engine parts
Furnace parts
Welding rods
Heat exchangers