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Why Stainless?
150,000 Litre Tanks...
3CR12, an Excellent Material for
Atmospheric Applications...
Tersainox and its New
Production Lines...
Super-Duplex Stainless Steel...
May 2011
Edition N° 55
English
Why Stainless?
The main reason for stainless steel’s
existence is its resistance to corrosion.
Chromium is the principal alloyed
element and stainless steel contains at
least 11%. Chromium is a reactive
element, however the alloys that
contain
Chromium
passivated,
demonstrating an excellent resistance
to many conditions.
Stainless steel refers to a great
number of alloys resistant to corrosion,
with specific mechanical properties and
the cost varies considerably. In our area,
despite the fact that the demand for
these
materials
has
increased
significantly, the domestic industry
continues to cover almost 90% of its
stainless steel need with barely two or
three types of these alloys, the most
common of which being AISI 304 and
AISI 316.
The stainless steel properties are
significantly influenced by their
chemical composition, which in turn
determines
these
alloys’
micro-structural characteristics. At
present, stainless steel can be generally
classified in four main families:
-
Ferritic stainless steel
Austenitic stainless steel
Martensitic stainless steel
Austenitic ferritic (Duplex)
In addition to these, there are other new types of stainless steel such as hardenable ferritic- martensitic
stainless steel.
Page N. 1
Why Stainless?
Ferritic Stainless Steel
This type of alloys contains between 12% and 29% Cromium and very low quantities of Ni [Nickel] (2%). Its
name is derived from its microstructure, entirely constituted of ferrite.
This type of stainless steel is more economic due to its low content of Ni. However, the economical advantages
derived from this are not able to fully utilise this value in these alloys, mainly due to the technological difficulties
associated with the greater probability of provoking secondary phases (difficulty in fabricating products of great
thickness and weldability problems). This aside, due to its good resistance to stress corrosion cracking (SCC), to
corrosion pitting and crevice in media containing chloride, it may be selected in particular applications, as an
alternative to austenitic stainless steel.
Ferritic stainless steel is magnetic, has
good ductility and is resistant to
corrosion and oxidation at high
temperatures. The stainless steel type
AISI 430 is the most common of this
group; it contains 17% Cr and is
considered as a multipurpose alloy for
applications where the corrosion
resistance demands, especially in the
welded joints, are not so important. The
stainless steel type AISI444 (18% Cr 2%
Mo) holds a better resistance to corrosion
from pitting and crevice equivalent to
austenitic stainless steel type AISI 316L.
In recent years ferritic stainless steel has being developed, specifically designed for their use in the manufacture
of sea water condensing units. Alloys for this type of application usually contain Cr > 26% and Mo > 3% and are
known as super-ferritic stainless steel.
Page N. 2
Why Stainless?
Austenitic Stainless Steel
This is the most popular group of the stainless steel family. It is made up of cold-rolled hardenable non-magnetic alloys
(when cold-rolled it is possible that they may become slightly magnetic) but not for heat treatment. Its microstructure is
fundamentally constituted of austenite grains. The presence of Ni in these steels allows the stabilisation of the austenitic
phase while the only addition is that of Cr, which would produce a ferritic microstructure at room temperature.
Austenitic stainless steel has an excellent resistance to corrosion, very good conformality and it is generally very easily
welded (better than ferritic stainless steel).
The stainless steel type AISI 304L (19% Cr – 10% Ni)
is the most represented of this alloy group. It has
good resistance to atmospheric corrosion and is
used to a large degree in the chemical, food and
medical industries. When the service conditions
demand greater resistance to pitting corrosion is
used the stainless steel type AISI 316 is used (17%
Cr – 12% Ni – 2% Mo) which is used mainly in
industrial processes such as paper manufacture
and the food industry.
The AOD process allows one to obtain stainless
steel with S (Sulphur) contents less than even
0.001%. This helped to reduce the problems of
fragility under heat and effectively initiated the
development of more and more alloyed stainless
steel.
Therefore new types of more resistant alloys such as the grade AISI 317 (18% Cr 13% Ni – 3.5 Mo) and “super austenitic”
stainless steels with further additions of Mo and N were introduced. In this last group the alloy types 20% Cr – 18$ Ni – 6% Mo
– 0.2% N (Avesta TM 654 SMO), considered as one of the most manufactured commercial austenitic stainless steel to date,
capable of competing in corrosions resistance with the majority of the Nickel-based super alloys.
These new alloys are used in chemical processes with the presence of very aggressive media (high concentrations of
chlorides and high temperatures). The typical applications are pulp mills, sea water piping systems, structural element
constructions for offshore platforms, etc. Tersainox has earned national as well as international reputation in the handling of
this family of noble materials: AISI 304L, AISI 316>, 3CR12, ACEROS DUPLES LDX 2101, SAF 2304, 2205, 254 SMP, 904-l, AL6 XN,
HASTELLOY.
We have an experienced group of experts who will be able to locate the type of stainless steel in the best way possible in
order to find the solution for your needs.
Patricio Campos Castro
Mining and Industry Division
Tersainox Group Inc.
Page N. 3
150,000 Litre Tanks
Tersainox S.A. manufactured 150,000 litre capacity tanks with great success in first quality steel, types 304-L
and 316-L. This manufacture was completed in a minimum timeframe, meeting the demands and sanitary
norms as well as the creation of these.
The tanks were built in our plant
and transported to the new client’s
plant; once in the plant heavy
machinery was required such as
cranes and others in order to install
and anchor the tanks, a task that
was carried out with great success
and satisfaction from the client.
Remarks from the commercial
manager, Mr.: Eric Miranda Lagos
Delay of the project was contemplated, given the demands of the tanks in terms of quality as well as the
commitments that would be taken up with our new clients, the time allocated was not sufficient.
To us this new plant had to meet the European quality standards; in other projects these were not met with
Chilean manufacturers. After visiting Tersainox with German engineers, we made the decision to handover
the manufacture of equipment to this company, being able to comply with the product manufacture
requirements.
Following various meetings with Tersainox executives we decided to commit to the project; a good
decision, as we successfully installed the equipment in order to be able to process and thus fulfil our contracts.
Remarks by the owner of the company.
Eric Miranda Lagos
Food Division
Tersainox Group Inc.
Page N. 4
3CR12, an Excellent Material for
Atmospheric Applications
The stainless steel type 3CR12 is an excellent material for more severe atmospheric applications. A study
prepared by BG Callaghan (CISR Science and Technology, Materials Division), produced an essay on
Atmospheric Corrosion in South Africa during a 20 year period in different atmospheric conditions and on
different types of steel, which demonstrated the following results.
3CR12 is very corrosive resistant in marine and highly corrosive environments, when compared with
galvanized steel which can last between one and five years and after the zinc is consumed the corrosion shall
be the same as that which common carbon steel reveals. 3CR12 has a performance similar to that of aluminium
in marine environments; with the coating application, it has proved very successful in highly corrosive
environments.
We know two examples of 3CR12 used in bridges in the
south of Africa:
The Millenium Bridge in Umshlanga Rocks in Natal , which is
made from tubular sections, and pedestrian bridges along
the south coast where reinforcement bars of 3CR12 were
used.
Cristian Lohse
Sales Executive
Tersainox Group Inc.
Page N. 5
Tersainox and its New
Production Lines
Last year, in our constant determination to improve our production plant, the expansion of the external
production area associated with workshops was undertaken and today we can show you the improvements
made in this area:
Reinforced concrete slabs with two external production lines plus their respective gates.
In the attached photo you can appreciate that one of the concrete slab production lines is already being
worked on, using the space and surface quality with the implementation of a new assembly line for road
tankers.
The other production line shall soon
be in operation and its plans are
already being programmed.
Tersainox S.A. is proud to be growing
and improving its production
capacity for its current and future
stainless steel projects. The problems
and inconveniences we experience
today in our daily work shall be
replaced with the largest installed
capacity in our plant that we offer
you all.
“When you think stainless steel, think Tersainox”.
Guillermo Rudolph
Sales Engineer
Tersainox Group Inc.
Page N. 6
Super-Duplex Stainless
Steel
The first generation Duplex stainless steel was developed in Sweden more than 70 years ago for use in the paper
industry. Duplex alloys were originally created to combat corrosion problems caused by chloride-bearing cooling waters
and other aggressive chemical process fluids. Called Duplex because of its mixed microstructure with about equal
proportions of ferrite and austenite, Duplex stainless steels are a family of grades, which range in corrosion performance
depending on their alloy content.
The term "Super-Duplex" was first used in the 1980's to denote highly alloyed, high-performance Duplex steel with a
pitting resistance equivalent of >40 (based on Cr% + 3.3Mo% + 16N%). With its high level of chromium, Super-Duplex
steel provides outstanding resistance to acids, acid chlorides, caustic solutions and other environments in the
chemical/petrochemical, pulp and paper industries, often replacing 300 series stainless steel, high nickel super-austenitic
steels and nickel-based alloys.
Recently, the production of high-strength, corrosion resistant
super-duplex coil has been implemented in the marine and chemical
industries, architecture and mast riggings, wire lines, lifting and pulley
equipment and well service strands. In fact, development of wire
processing techniques has enabled the production of steel wires down
to 1mm in diameter.
Modern Duplex stainless steel can be divided into four groups:
1. Lean Duplex such as 2304, which contains no deliberate Mo addition;
2. 2205, the work-horse grade accounting for more than 80% of duplex
usage;
3. 25 Cr duplex such as Alloy 255 and DP-3;
4. Super-Duplex; with 25-26 Cr and increased Mo and N compared with
25 Cr grades, including grades such as 2507, Zeron 100, UR 52N+, and
DP-3W
BENEFITS
• High strength,
• High resistance to pitting, crevice corrosion resistance.
• High resistance to stress corrosion cracking, corrosion
fatigue and erosion,
• Excellent resistance to chloride stress-corrosion cracking
• High thermal conductivity
• Low coefficient of thermal expansion
• Good sulphide stress corrosion resistance,
• Low thermal expansion and higher heat conductivity
than austenitic steels,
• Good workability and weldability,
• High energy absorption.
APPLICATIONS
• Heat exchanger tubes and pipes for production and
handling of gas and oil,
• Heat exchanger and pipes in desalination plants,
• Mechanical and structural components,
• Power industry FGD systems,
• Pipes in process industries handling solutions containing
chlorides,
• Utility and industrial systems, rotors, fans, shafts and
press rolls where the high corrosion fatigue strength can be
utilized,
• Cargo tanks, vessels, piping and welding consumables
for chemical tankers.
• High-strength, highly resistant wiring.
Marcelo Salas
Australia Tersainox Pty.Ltd
Page N. 7