Stainless Steel: A family of alloys that show marked resistance
to corrosion and chemical attack. (300 series contain
high chrome & nickel).
to Use Stainless:
A. Cleanliness is maintained in the product being transported.
B. Prevention of contamination of the product from small
particles or rust & scale.
C. Resists corrosive attack from hundreds of industrial
and chemical solutions or mixtures.
D. Greater strength at elevated temperatures.
Example: At 1000 deg. F, strength
for weld fittings or pipe is based on:
A234 Carbon Steel (WPB) has allowable stress
= 2,500 PSI
A403 Stainless (WP304) has allowable stress
= 13,750 PSI
A403 Stainless (WP316) has allowable stress
= 15,300 PSI
E. Cryogenic service (superior mechanical properties at
F. Retains lustrous appearance Indefinitely
Types of Stainless
There are several kinds of stainless and they are defined
below for your information. Generally when people talk
about stainless (particularly in the piping Industry)
they are talking about AUSTENITIC stainless - the 300
series - which Is the type of stainless stocked and sold
by Robert-James Sales.
1. Martensitic: 13% chrome,
.08-2% carbon. Can be hardened by heat treatment and is
Example: Type 410 - has good ductility & Corrosion
resistance. Used for trim on cast steel valves.
2. Ferritic: 17% chrome & same carbon
as martensitic. Higher chrome imparts increased resistance
at elevated temperatures. Lack of tensile strength and
poor machinability restricts its application.
3. Austenitic: (300 Series). Chrome 16-25%,
Nickel 8-20,.15% carbon max. can be modified by the addition
of molybdenum, titanium or tantalum. It is non-magnetic,
has superior corrosion resistance than straight chrome
stainless. Mechanical properties can be increased by cold
working. Has a wide range of mechanical and physical properties
making it highly desirable for piping applications.
4. Avesta 2205 is a Duplex Stainless
combination of Ferritic & Austenitic. It has higher
corrosion resistance than 316 (3% min. Moly vs 2% in 316),
highly resistant to stress corrosion & Chloride cracking.
It is cost effective because it has only 5% Nickel. Duplex
stainless has high strength, ductility, toughness and
5. AL-6XN ® is a superaustenitic
stainless steel which was developed by Allegheny Ludlum
Corporation. It exhibits far greater resistance to chloride
pitting, crevice corrosion and stress-corrosion cracking
than exhibited by the standard 300 series stainless steels,
and is less costly than the traditional nickel-base corrosion
The AL-6XN alloy has exhibited good performance in variety
of highly corrosive environments. The AL-6XN alloy is
available in a wide range of product forms including plate,
strip, sheet, bar, billet, tubing, pipe, and castings.
Its various product forms are covered by ASME and ASTM
specifications. The use of wrought AL-6XN products in
the ASME Boiler and Pressure Vessel is covered by Code
Case 1997 (latest revision) for Section VIII construction
and by Code Case N-438 (latest revision) for Section III
construction. The use of AL-6XN castings is covered by
Code Case 2106 (latest revision) for Section VIII and
Code Case 497 (latest revision) for Section III construction.
The alloy is approved for both welded and unwelded construction
under ANSI/ASME B31.1 Code Case 155. Use of AL-6XN alloy
in contact with hydrogen sulfide-containing petroleum
and natural gas is covered by NACE MR0175-92.
6. 254SMO is an austenitic stainless
steel designed for maximum resistance to pitting and crevice
corrosion. With high levels of chromium, molybdenum, and
nitrogen, 254SMO is especially suited for high chloride
environments such as brackish water, seawater, pulp mill
bleach plants and other high chloride process streams.
254SMO offers chloride resistance superior to that of
Alloy 904L, Alloy 20, Alloy 825 and Alloy G. 254SMO is
compatible with the common austenitic stainless steels.
It is often used as a replacement in critical components
of larger constructions where Type 316L or 317L has failed
by pitting, crevice attack, or chloride stress corrosion
cracking. In new construction, 254SMO has been found in
many cases to be a technically adequate and much less
costly substitute for nickel-based alloys and titanium.
254SMO is substantially stronger than the common austenitic
grades, but is also characterized by high ductility and
impact strength. 254SMO is readily fabricated and welded.