From
Avesta: Stainless steel evaporators at Smurfit Kappa Kraftliner, Piteå.
The
world's best process for welding any all
position, thin or thick duplex application
is TIP TIG.
From
Avesta: Pulp Paper Industry Stainless Steels and Duplex:
In modern pulp and paper mills, nearly all key
equipment (digesters, bleaching systems, evaporators, storage tanks and paper
machines) are made from various types of stainless steels. Approximately 5,000
to 6,000 tonnes of stainless steel go into a large new pulp and paper mill. On
top of that, there is piping, welding consumables and auxiliary equipment. The
materials used are standard austenitic, duplex and high-alloy super-austenitic
stainless steels.
Currently, the high price of the alloying elements in
the raw materials is one of the reasons why manufacturers serving the pulp and
paper industry are showing increased interest in duplex steels. However, the most
important factor is that, even though the nickel and molybdenum content is generally
low, duplex steels have very good properties. “Previously, so-called ‘acid-resistant’
steels were used when the sulphite process (an acid process) was used in cooking
paper pulp. Now that the industry is increasingly switching to sulphate or other
alkaline solutions, such steels are no longer optimal,” says Lena Wegrelius.
Stress
corrosion presents the greatest risk in alkaline
cooking and stainless steels with a high
chromium content, low molybdenum content and duplex microstructure are
optimal for these environments. Furthermore, the strength of duplex steels is
"twice" that of standard steels. Consequently this allows pressure vessels
to be built with thinner walls. Duplex steels are more cost-efficient austenitic
steels.
Duplex stainless steel are becoming ever more popular with
equipment manufacturers. Avesta has a new duplex grade, LDX 2101®, which is
excellent for the paper industry. However, its a fact that the choice of materials
when building new plants or machinery is not determined solely by what is best
for the application. For example, in Latin America, mills are favoring their own
local producers and these producers do not always manufacture duplex steel. In
those cases, standard materials are being used. Its believed that Chinese manufacturers
will soon be producing duplex steels themselves.
Failure
of a super duplex stainless steel reaction vessel
V.
M. LintonCorresponding Author Contact Information, E-mail The Corresponding Author,
a, N. J. Laycockb, S. J. Thomsenb and A. Klumpersb
a University of Adelaide,
Adelaide, 5005, South, Australia
b Materials Performance Technologies, Industrial
Research Ltd, Lower Hutt, New Zealand
Received 1 July 2002; Available online
18 November 2003.
Abstract
Crevice
corrosion and stress corrosion cracking (SCC) were recently discovered in a vessel
used to strip vinyl chloride monomer from a water-based slurry of PVC granules. The vessel was manufactured from UNS S32750 super duplex
stainless steel and the welds were produced using matching welding consumables.
Although localised corrosion might have been expected, the occurrence
of SCC was inconsistent with the majority of the published literature: in particular,
the nominal operating temperature should have been too low for chloride-induced
SCC of super-duplex stainless steel. However, damage was found mainly in the vicinity
of the circumferential and longitudinal welds, and part
of the subsequent failure investigation was therefore focused on the possibility
of poor weld quality being the cause of failure.
This task was
approached primarily by measuring the influence of welding
parameters on the value of the critical pitting temperature (CPT), and
attempting to correlate the results with observed changes in the weld microstructure.
CPT values were determined by a potentiodynamic method, using samples cut from
the failed vessel and from a range of reference welds manufactured using known
welding parameters.
TIP TIG provides extensive duplex weld benefits
to the beverage and food industries.
TIP TIG Customer: ZIEMANN BAUER is a German company who is world market
leader in building breweries.
Ziemann is also one of the world's largest fabricators of duplex alloys.
For lean duplex tank and pipe welds, this company used to use Lean Duplex Flux Core wire from Avesta (DX 2201). Apart from the weld smoke issues, the company would have weld slag, porosity, fusion, spatter and smoke issues. The weld defects resulted in extensive back gouging and grinding. After years of trying SMAW, PULSED MIG and Flux Cored on there stainless and duplex applications, within a few hours of trying TIP TIG, this company made the decision to switch to TIP TIG and eventually purchased 27 TIP TIG units.
The welder on the left had never before welded with TIPTIG. The setup for this vertical up test weld on 3/8 plate job required only 5 minutes. On this open root vee groove welds. no back bars, no ceramic backing, no back gouging, no weld smoke, no spatter, no slag, no porosity, consistent weld fusion, the least distortion and the company figured out a way with the duplex and stainless weld how to avoid the costs associated with purging there tanks for the open root welds. At the end of the day the only concern for this German company was how fast TIP TIG could deliver the TIP TIG equipment. You can view these welds in the video sections.
TIP TIG AND TWO SIDE ROOT WELDS. On the above and right duplex plates,
TIP TIP enables two sided welds as seen in these photos and UTUBE videos welding the 3/8 lean duplex. Brewery vessels require unique ID root weld quality. With the open root TIP TIG method we do not have to purge the tank, we have no root back gouging, no root or groove grinding, no weld spatter, no backing bars or ceramics required. With this application as shown below in the video you can expect no weld defects, you will have the least possible weld distortion. Note also again the lack of weld fumes generated with TIP TIG.
When you are dealing with code quality welds,
weld rework, NDT costs, weld grinding, gouging weld cleaning and weld skills inconsistency, all have an impact on your companies profits and the TIP TIG process addresses those issues.
With alloy applications, TIP TIG will take
your weld quality and productivity to a level which you simply cannot obtain with any other weld process. Note how comfortable the welders are as they hold the light weight TIP TIG torches. Also note how instead of worrying about manual feeding a TIG wire length at a low
15 - 20 inches/min they are feeding 200 to 250 inch/min and using their other hand for improved stability of the TIP TIG torch.
Average manual traditional TIG weld speeds are 3 - 4 inch/min. TIP TIG manual or mechanized weld speeds are typically 10 to 20 inch/min. Examine
the minimum HAZ with the duplex welds. Note the remarkable weld cleanliness and the weld fluidity of
the sluggish duplex TIP TIG vee groove fill pass welds, you know this weld will not fail
any NDT tests.
These TIP TIG duplex welds enabled weld speeds that provided low weld heat input
resulting in excellent mechanical
properties. The weld was 100% free or pores. No spatter,
occasionally use a wire brush. For those interested in reducing costs, this duplex two sided open root did not require conventional purging or back gouging.
WHY STRUGGLE WITH FLUX CORED OR PULSED MIG
WHEN
YOU
CAN PRODUCE MANUAL TIP TIG DUPLEX OR STAINLESS
OVERHEAD UNTOUCHED WELDS THAT LOOK LIKE THIS?
Difficult alloys and difficult weld positions are no longer a concern with TIP TIG.
This 3/8 lean duplex, TIP TIG over head weld is welded with DX2101 MIG wire.
Note the large TIP TIG weld control, the weld cleanliness and continuity.
Manual
TIP TIG Horizontal Duplex Weld. Industry
Brewery / Chemical Tanks, Shipyards LNG Vessels or Refineries.
This plate is the weld qualification for a duplex brewery tank. The two sided
TIP TIG welds
eliminate vessel and tank purging and provide exceptional
control of the root profile which is important in this
industry.
This company purchased 24 TIP TIG units,
Do your untouched vertical up welds look like this manual TIP TIG
weld
and would your welds be free of weld defects?
This vert up TIP TIG weld was made by a a first
time user of the TIP TIG process.
ZIEMANN HAS TO PRODUCE 18 DUPLEX TANKS FROM 12 TO 17m DIAMETER AND THIS
COMPANY TURNED DOWN REGULAR TIG, PULSED MIG AND FLUX CORED AND SELECTED TIP TIG.
These duplex tanks will then be built into ships to transport orange juice or other
beverages.
For these types of containers exceptional weld quality is required.
Note the outstanding
all position full penetration weld quality, no weld
cleaning,
no weld spatter,
no distortion issues and no weld rework.
The duplex plate was protected
with a zinc rust inhibitor and the welder
wears a
ventilated hood,
yet note there are
no evident weld fumes from the TIP TIG process.
You will never see regular TIG used on a large fabrication such as this.
ONLY TIP TIG COULD PROVIDE THE QUALITY REQUIRED FOR THE DUPLEX 3/8 LARGE CONTAINERS THAT WILL BE BUILT INTO A SHIP TO TRANSPORT BEVERAGES..
At
Smurfit Kappa Kraftliner, Piteå, both the peroxide reactor and the oxygen
reactor,
behind it, are manufactured from 2205 duplex stainless steel.
From
Avesta: The commercial development of stainless steel occurred side by side with
that of the modern pulp and paper industry. This was a phenomenon of 1940’s
northern Europe. The unique collaborations between engineering companies (developers
of new and more efficient pulp and paper processes) and steel mills have led to
unsurpassed expertise in stainless steels for various pulp and paper applications.
They have also led to the development of new steel grades such as 254 SMO®
and LDX 2101®. To test how its steel grades stand up to various environments,
Outokumpu has a number of research and development collaborations with mills,
machine builders, research institutes and engineering companies. Amongst other
projects, Lena Wegrelius mentions that with an inspection company, Inspecta. In
this, field tests are being run in digester and evaporator environments at the
Smurfit Kappa Kraftliner pulp and paper mill in Piteå. “We are also
working with Chempolis Oy in Finland. The latter company is looking at processes
for cooking pulp from raw materials other than wood. This is of future interest
for the Asian market,” she declares. In China, for example, trials are being
conducted with the common reed and residual products from arable and rice farming.
New processes and steel grades may be necessary here. What else can be said about
developments in pulp and paper? “For environmental reasons, the industry
is using more and more recycled paper in its raw materials. It is often said that
fibres can be used seven times before they are finished. Recycling processes are
thus becoming increasingly more important in pulp production,” concludes
Lena Wegrelius.
AVESTA
NEW DUPLEX FLUX CORED WIRE:Avesta FCW-2D LDX 2101There is now a new and
improved version of Avesta Welding’s flux cored wire for welding Outokumpu’s
new duplex steel, the LDX 2101®.Avesta FCW-2D LDX 2101 gives a duplex weld
metal that combines excellent mechanical properties with good corrosion resistance.
In both the flat and the horizontal-vertical (PC) positions, weldability is very
good Positive direct current (DC+) is used for welding flux cored wires. Compared
with MIG welding, the flux cored wire parameter range is considerably wider. Avesta
FCW-2D is an 0.045 1.2 mm wire supplied in a layer wound on 15-kilo wire basket
spools. Avesta Welding’s range of filler metals for welding LDX 2101®
also includes covered electrodes and solid MIG, TIG and SAW wires. Best weld results come with TIP TIG and the duplex MIG wires.
AVESTA
2304
For welding storage tanks, recovery boiler
pipes, oxygen reactors, etc. in duplex stainless steel 2304 (EN 1.4362, Outokumpu
2304). Avesta Welding is the first supplier in the
world able to offer a complete
range of matching filler metals for this duplex grade. The range comprises covered
electrodes, flux cored wires and solid wires (MIG/TIG/SAW).
AVESTA
2205 For welding batch and continuous digesters,
oxygen delignification and pressurized peroxide reactors, press washers, pulp
towers and filters, etc. made of 2205 duplex stainless
steel (EN 1.4462, Outokumpu
2205). Giving excellent mechanical properties and corrosion resistance, Avesta
2205 has a long record of success in these applications.
AVESTA
2507/P100 For welding super duplex 2507 (EN 1.4410,
Outokumpu SAF 2507) and similar grades. Avesta’s 2507/P100 range of highly
alloyed super duplex consumables provides better
strength and corrosion resistance
than ordinary duplex fillers.
AVESTA
LDX 2101 Specially designed for welding Outokumpu
LDX 2101 (EN 1.4162), the new high-strength low-alloy duplex stainless steel.
Thanks to its superior strength and good corrosion resistance in alkaline environments,
this cost-efficient material is a maintenance-free option for railings, walkways,
storage tanks and even hydrogen peroxide reactors in pulp bleaching.
With Avesta
LDX 2101, it is easy to achieve a sound weld that, as regards corrosion resistance
and mechanical properties,“matches” the parent metal.
130
ton Brazilian urea reactor
.
Jaraguá of Brazil manufactured
and delivered a complete urea reactor to Petrobras/FAFEN in Camaçari (Brazil),
all the stainless steel plates and welding consumables came from, respectively,
Outokumpu and Avesta Welding in Sweden. The reactor, which was the first to be
produced in South America, weighs 130 tonnes. Besides conventional non-destructive
testing, the reactor was subjected to helium leakage tests and positive material
identification (PMI). Furthermore, all stainless steel (welded joints included
therein) were corrosion tested as per ASTM A262’s “practice C”
(Huey test). The special technique developed to measure the gap between shell
and lining (maximum permitted limit of 3.0 mm) is worthy of individual highlighting.
Compared with other assignments, one of the greatest differences for Jaraguá
was that, to guarantee perfect handling and cleaning of the stainless steel, manufacture
of the reactor was kept entirely separate from other production.
Realisation
and testing was in accordance with ASME Code Section IX. In addition, test coupons
for the qualification of welding procedures were tested as follows:
Article
From Avesta.
2009. Note from Ed This company
and Sanvik are an excellent source for duplex info, however both these companies are not aware of TIP TIG a seven year old process which without question is the best welding method for the majority of duplex applications.
High
productivity welding of the new lean duplex stainless steel,
LDX 2101® (S32101)
With their strengthening in the
mid 1980's, duplex steels increasingly provided an alternative to conventional
austenitic steels. They were then predominantly used for chemical tankers as well
as process vessels and storage tanks in the pulp and paper industry. It is the
good combination of strength and corrosion resistance that makes duplex stainless
steels so attractive. However, in the beginning, the duplex grades were primarily
seen as alternatives to high-performance austenitic grades (e.g. 904L and 254
SMO®) rather than as alternatives to conventional grades (e.g. 304 and 316).
This limited their use in general construction. Here, high strength is needed
rather than high corrosion resistance. Developed by Outokumpu Stainless, LDX 2101®,
the new "lean" duplex stainless steel, is now used in a very wide range
of applications. General
purpose and structural applicationsare just two examples. The high strength
and good corrosion resistance of LDX 2101® also make it extremely suitable
for a variety of storage tanks. This article focuses on examining how high productivity
welding methods using Avesta LDX 2101, can be optimised to maximise the good corrosion
resistance and mechanical properties of duplex LDX 2101 stainless steel. Strength
and corrosion resistance Of the duplex grades currently on the market, LDX 2101®
has the "least alloyed" chemical composition with a nickel content of
just 1.5% (balanced with 5% manganese and some 0.22% nitrogen), LDX 2101 offers
high mechanical strength and corrosion resistance at an advantageous price. Nickel
is an expensive metal. Furthermore, its price fluctuates widely over time. This
can present major difficulties when estimating the total cost of a construction.The
chemical composition of LDX 2101 is balanced to give a microstructure with approximately
equal amounts of ferrite and austenite. Thanks to the high nitrogen content, austenite
re-formation after welding is rapid. In general, corrosion properties are as good
as, or better than, those of the Cr-Ni grade EN 1.4301/ AISI 304. Furthermore,
the steel's duplex structure and high nitrogen content result in a mechanical
strength almost twice that of ordinary, austenitic steels.
The
high strength of LDX 2101 steel can be used to optimise the design of various
storage tanks. On top of this, the steel's cost efficiency can be fully exploited
by selecting the correct filler (Avesta LDX 2101) and welding method.Better properties
with matching filler metals Because it is optimised to ensure the best welding
characteristics and mechanical properties, the matching Avesta LDX 2101 filler
should be used to weld LDX 2101® duplex stainless steel. To obtain a suitable
ferrite/austenite balance in the weld metal, Avesta LDX 2101 is over-alloyed with
nickel.
The microstructure of metal arc welded LDX 2101 has a typical
duplex appearance with 30 - 65% ferrite.Testing of LDX 2101 welds has shown that
tensile strength is higher than 680 MPa / 99 ksi and that fracture most commonly
occurs in the parent metal. Bending tests to 180°
with a 3 x t mandrel
have shown no signs of cracking.
Duplex Welding
Methods and Weldability. Good results are obtained when welding LDX
2101 using all conventionalmethods - SMAW, FCAW, MIG, TIG and SAW. General recommendations
for the welding of storage tanks are given below. Please keep in mind that none of the processes listed below can provide on duplex the weld quality attained by TIP TIG.
TIP TIG will produce the best quality all position duplex welds at moderate MIG wire feed rates. No sluggisg issues and no internal weld defects. Check the TIP TIG section.
Aug
2008. A new lean duplex stainless steel grade EN 1.4062 (UNS S32202)
has been developed by Industeel and Ugitech by combining
low nickel content with a nitrogen addition but without an increase in manganese.
Nickel is reduced by a nitrogen addition to develop a microstructure containing
approximately 50% ferrite and 50% austenite. After a preliminary study with laboratory
heats, several industrial heats were produced with composition 22Cr, 2Ni, and
0.2%N.
Even tho they are seven years behind the times, another
great source of Duplex Weld Data / Electrodes is
Sanvik / ESAB. July 2008. Sandvik Materials Technology has launched
a hyper duplex stainless steel tube material which is designed to improve umbilical
performance in increasingly demanding subsea environments. Sandvik SAF
3207 HD is designed specifically for deepwater, high temperature, and extreme
pressure applications.
Sandvik SAF 3207 HD provides
a tensile strength of 980 to 1180MPa and a maximum operating temperature of up
to 90C. This compares with a tensile strength of 800-1100MPa and maximum water
temperature rating of 65C for the company’s standard super-duplex grade SAF
2507. SAF 2507 can be deployed in water depths greater than 2000m. However, as
the pressure at the seabed increases with depth, the wall thickness of the tube
eventually becomes so great that it can become uneconomical to purchase all the
material required.
Duplex
steels offer great mechanical properties and corrosion resistance. The primary
difference between austenitic stainless and duplex steels is the duplex offers
a balanced microstructure of approx. equivalent volumes of both ferrite and austenite.
Typically the duplex steel will have a weld ferrite content of 40 to 60% and the
weld 25 to 40 % ferrite. A 25% to 50% ferrite range is desirable.
In
comparison to traditional austenitic stainless, the duplex, two-phase microstructure
and high chrome / Mo can result in duplex applications that have;
[a]
higher resistance to stresses,
[b] higher resistance to pitting corrosion
cracking,
[c] improved intergranular corrosion resistance.
Note:
Be aware of too much or too little ferrite. Rapid quenching of the duplex weld
as found in arc strikes or small welds on large parts should be avoided as this
can result in very high ferrite content > 60%. The extra high ferrite welds
can result in low toughness or low corrosion resistance.
Ferrite in duplex
results in lower coefficient of thermal expansion in contrast to austenitic stainless
resulting in less weld distortion potential.
Corrosion
Potential Information from Sanvik..
This
data is from Sanvik: Materials used in oil and gas extraction are affected to
several different types of corrosion, often caused by seawater and spray. The
types of corrosion, which can occur on stainless steels in marine environment,
are pitting and crevice corrosion, and for standard austenitic grades also stress
corrosion cracking (SCC), if the material temperature is above 60°C (140°F).
These are all localised attacks – general corrosion need not be considered
for stainless steels in seawater. High temperatures, high chloride contents and
low pH values increase the risk of localised attacks in any chloride-containing
environment. Of these, temperature is usually the most influential factor.
However, there is a fourth important consideration: the electro-chemical corrosion
potential of the environment. In seawater, this potential is affected by biological
activities on the steel surface. Since seawater is, in a sense, a living corrosive
environment, it is sometimes difficult to define exactly what the service conditions
will be. At normal seawater temperatures, a biofilm will form on the steel surface
and result in a corrosion potential of +300 to +500 mV/SCE.
At
temperatures above ~40°C (100°F) the biological activity will cease and
the corrosion potential will drop. The use of continuous chlorination, to stop
marine growth, may increase the corrosion potential to values as high as +600
to +800 mV/SCE. This, however, can be avoided through the use of intermittent
rather than continuous chlorination.
Benefits
over Cu and CuNi-based alloys Stainless
steels are very resistant to erosion corrosion compared with Cu and CuNi-based
alloys, which are very sensitive to this form of attack. Water in harbours, around
offshore platforms, and near chemical plant sites is often contaminated e.g. with
ammonia (NH 3 ) and sulphides (S 2- ). These compounds, even in very small quantities,
cause localised attacks on copper-base alloys, while stainless steels are not
affected at the impurity levels involved.
Sour
corrosion: Wet and sour service: The corrosivity of an oil and
gas well is increased by the presence of chlorides in water solutions, carbon
dioxide, and hydrogen sulphide.
The
environment is considered sweet as long as no hydrogen sulphide is present. Carbon
dioxide alone can however cause high corrosion rates on carbon steel, since it
is acidifying the solution. This is further accelerated if chlorides are present.
Sour
environments are defined when the partial pressure of hydrogen sulphide is above
0.05 psi. At higher partial pressures, the corrosion rate on carbon steel is substantially
increased by means of making the water phase more acidic and by forming iron sulphide
scale. Sulphide Stress Cracking (SSC) is common in high strength steels containing
martensite. It can also occur in ferritic steels.
Stainless
steels are different. Sandvik Sanicro 28, Sanicro 29, SAF 2205 and SAF 2507 grades
are completely resistant to corrosion in wells rich in carbon dioxide with a high
amount of chlorides in the water phase. If hydrogen sulphide is present, there
is still no general corrosion, but the risk of localised corrosion increases,
especially with regard to SSC.
The
NACE TM-0177 test.
Experiments have been carried out at room temperature in
accordance with the NACE TM-0177 test (5% sodium chloride, 0.5% acetic acid, saturated
with hydrogen sulphide).
The
threshold stress for cold-worked Sandvik SAF 2205/22Cr is about 90% of the yield
strength, which is very good when compared to results for high strength, ferritic
stainless steels.
Sandvik
Sanicro 28, in the cold-worked condition, results in no failures up to very high
stress levels. The high alloy duplex stainless steel Sandvik SAF 2507 is also
resistant to cracking in the solution-annealed condition.
In
general terms, this test shows that Sandvik Sanicro 28 has a higher resistance
to sulphide stress cracking compared to SAF 2205/22Cr, which is much more resistant
than 13Cr. Sandvik Sanicro 29 has an ever higher resistance to localised corrosion
and sulphide stress cracking than Sandvik Sanicro 28.
It
should be remembered that the chemistry of the “NACE solution” is not
representative of the conditions in most sour oil and gas wells. This is especially
true for acidity, where the pH value is lower in the NACE test. Results from the
NACE TM-0177 test, therefore, should not be used for determining the suitability
of different grades, but more as a ranking test. Other tests, more representative
of actual service conditions, must be used to determine the suitability of different
grades. Practical experience of specific grades is, of course, extremely useful.
Visit Sanvik's web site for more excellent data on stainless and duplex
products, however if you want the best stainless MIG process control data visit
here,,
The
Metallurgy of Duplex Stainless Steels.
Most
duplex have an alloy range of,
Cr - 22 to 26%. Ni - 4 to 7%. Mo
- 0 to 3%. With 0.1 to 0.3 Nitrogen, (no nitrogen will be in filler metals)
Nitrogen plays an important role of present day duplex alloys. Nitrogen is a potent austenite
stabilizer. The addition of nitrogen to the duplex steel will promote structural
hardening by a solid solution mechanism. The nitrogen therefore will raise both
the yield strength and ultimate strengths of the duplex without impairing toughness.
Nitrogen cannot be added to the filler metal as
it can not transfer across the arc. When welding nitrogen can be added to the
weld through the shielding or purge gas.
and high chrome / Mo can result in duplex applications that have; 
