Alloy 20Cb-3

General Characteristics of Alloy 20Cb-3

This is a stabilized austenitic, high-nickel stainless steel with excellent resistance to hot sulfuric acid and many other aggressive environments that would do great damage to, say, type 316 stainless steel. The alloy has been found to be resistant to a whole range of media and is suitable for use in a wide range of industries.
The alloy has excellent mechanical properties.

Chemical Analysis
C Carbon
0.06 max
Mn Manganese
2.00 max
S and P Sulfur and Phosphorus
0.035 max
Si Silicon
1.00 max
Cr Chromium
19.00/21.00
Ni Nickel
32.50/35.00
Mo Molybdenum
2.00/3.00
Cu Copper
3.00/4.00
Cb + Ta Columbium + Tantalum
8 x min/1.00

Applications

The alloy is widely used in chemical and allied industries. Typical usage is in the processing of synthetic rubber, high-octane gasoline, solvents, explosives, plastics, synthetic fibers, heavy chemicals, organic chemicals etc.
Alloy 20Cb-3 is also used for pump shafts and rods, valve stems, bolts, nuts, washers, tie rods and continuous-line pickling equipment.

Forging

Forging feed stock should be heated uniformly to 2100/2250ºF (1150/1230ºC). No forging should take place below 1800ºF (980ºC). Parts should be heated to 1725/1850ºF (940/1010ºC) after forging for 30 minutes per inch of section thickness and water quenched to ensure optimum stabilization.

Heat treatment

Alloy 20Cb-3 cannot be hardened by heat treatment. Annealing is carried out at 1725/1850ºF (940/1010ºC) for 30 minutes per inch of section thickness followed by water quenching. This treatment will ensure optimum stabilization. If maximum softness is required, say for improved formability, the annealing temperature may be increased up to 2100ºF (1150ºC) but only if the part will not be welded or used in service above 1000ºF (540ºC).

Stress relieving may be used – up to 1000ºF (540ºC) – on welded structures of intricate design.

Machinability

Chips are not quite as stringy as those found on the 18-8 stainless steels, and resultant surface finishes tend to be somewhat better.

Weldability

The alloy may be welded by shielded fusion and resistance welding processes. Oxyacetylene welding is not recommended as carbon pickup in the weld may occur.
The alloy may be used in the as-welded condition, but for high-temperature service a stabilizing post-weld anneal is recommended.

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