Gases for all types of stainless steel.

Gases for all types of stainless steel.
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Shielding gas.
Gases for all types
of stainless steel.
03
Stainless steel is usually defined as an iron-chromium alloy, containing at least 11 % chromium.
Often containing other elements such as silicon, manganese, nickel, molybdenum, titanium
and n
­ iobium, it is most widely used as corrosion resistant engineering material and it is used
in a
­ pplications where aggressive environments or elevated temperatures are prevalent.
Stainless steel is traditionally categorised into four main groups and each group is further
sub-divided into specific alloys. The main groups are: austenitic, ferritic, martensitic and duplex.
• Austenitic stainless steels are the most widely used group, accounting for around 70 %
of all ­stainless steels fabricated. They are used in applications such as chemical processing, ­
pharmaceutical manufacturing, food processing & brewing and liquid gas storage. The
weldability of these grades is usually very good.
• Ferritic stainless steels are not as corrosion resistant or as weldable as austenitic stainless
steels. They have high strength and good high temperature properties and are used for
products such as exhausts, catalytic converters, air ducting systems, and storage hoppers.
• Martensitic stainless steels are high strength but are more difficult to weld than other
types of ­stainless steels. They are used for products such as vehicle chassis, railway wagons,
­mineral h
­ andling equipment and paper and pulping equipment.
• Duplex stainless steels combine the high strength of ferritic steels and the resistance
of austenitic steels. They are used in corrosive environments such as offshore and
­petrochemical plants, where the integrity of the welded material is critical.
CRONIGON®, CORGON® and VARIGON® are registered trademarks of The Linde Group.
04
Perfect complements for MAG welding
Perfect complements for MAG welding.
Gases for all types of stainless steels
CRONIGON 2
CRONIGON 2He38
CRONIGON 2He55
Welding
speed
Spatter
­control
Reduced ­
Porosity
surface oxide ­control
Fusion
Penetration
Ease of use
Thickness
range (mm)
1 to 6
3 to 15+
1 to 12
The greater the number of dots, the better the gas performs.
MAG welding using solid wire with argon or argon/helium mixtures
is an important process for joining stainless steels. These gases also
contain small amounts of an oxidising gas such as carbon dioxide
to stabilise the arc. Carbon pick up can be a problem, and this l­imits
the amount of carbon dioxide that can be used. For low carbon
(“L”)-grade stainless steels this is l­imited to about 3 % but for other
grades up to 5 % can be used.
CRONIGON 2
A mixture of argon and 2.5 % carbon dioxide is a general purpose gas
mixture for MAG welding stainless steels. The mixture produces a smooth
weld with little or no spatter and with low surface oxidation, it reduces
the need to use aggressive chemical cleaning agents after welding,
avoiding a costly and time consuming process.
The gas performs in a similar way to gas mixtures used for welding steel,
so for users unfamiliar with welding stainless steel this can be a good
mixture to begin with.
This mixture is best suited to welding stainless steels below 6 mm in
thickness as it can begin to exhibit fusion and penetration problems
in thicker materials.
Some carbon pick up in the weld may occur, but levels in the weld metal
should not exceed those required for low carbon grades.
Perfect complements for MAG welding
05
CRONIGON
2He38
CRONIGON 2He38
CRONIGON 2He55
This three component shielding gas containing argon, helium and ­carbon
dioxide it is best suited for spray and pulse welding on thicker materials.
The welds produced have good fusion, low reinforcement and porosity
levels. This produces welds of the highest quality virtually eliminating the
need for rework or repair.
This argon, helium and carbon dioxide mixture produces welds with
very good low temperature toughness values, excellent corrosion
­resistance combined with good penetration as well as low levels of
porosity. This makes this mixture ideal for applications where weld
­quality is p
­ aramount and the cost of weld failure is high.
The welds also have good surface appearance with low surface
oxidation and excellent corrosion resistance. Reducing the need for
aggressive chemical cleaning agents, and minimizing cleaning times
keeping costs to a minimum.
This mixture is suitable for welding a wide range of material thicknesses
with excellent penetration and fusion properties, even on the thickest
materials or in multi-pass welds.
CRONIGON 2He38 is ideal for manual, mechanised and robotic welding.
The addition of helium into the gas means that welding speeds are
much higher than with CRONIGON 2, leading to significant improvements
in productivity. High welding speeds also have the advantage of keeping
distortion low, avoiding the need for costly rectification procedures.
The welding speeds achievable with this mixture are much higher
than with CRONIGON 2 and this can improve ­productivity and lower
the ­production cost per component.
CRONIGON 2He55 operates well in all transfer modes: dip, pulse
and spray, producing welds with very low surface oxidation and a
very r­ egular bead shape, reducing the need for post weld dressing
and aggressive cleaning, again reducing the cost of manufacture.
06
Benefits for flux and metal cored welding
Benefits for flux and metal cored welding.
Gases
of stainless
stainless steels
steels
Gases for all types of
Carbon dioxide
CORGON 25
CRONIGON 2
Welding
speed
Spatter ­
control
Porosity ­
control
Fusion
Penetration
Ease of use
Thickness
range (mm)
0 to > 25
0 to > 25
0 to > 25
The greater the number of dots, the better the gas performs.
Flux cored arc welding of stainless steels is becoming increasingly
popular as high quality tubular wires become available. As with
steel cored wires, check the wire manufacturer recommendations
when deciding which shielding gases are suitable.
Carbon dioxide
Stainless steel flux cored wires are often developed for use with carbon
dioxide because it is often seen as a low cost product. Carbon dioxide
gives good fusion and penetration characteristics, even in positional
work.
However, it produces a less stable welding arc, which increases the
amount of spatter and particulate fume generated. This can lead to
an increase in the cost of post weld cleaning.
Benefits for flux and metal cored welding
07
CRONIGON
2
CORGON 25
CRONIGON 2
When mixed gases are recommended for use with flux cored wires,
­CORGON 25 gives lower particulate fume and spatter levels than pure
carbon dioxide. These lower fume levels can improve the workplace
environment, as well as improve the well being of the workforce.
CRONIGON 2 is recommended by some wire manufacturers for use
with metal cored products, as its lower oxidation potential gives welds
with lower surface oxide making them easier to clean, lowering the
cost and shortening the production process.
08
The right gas mixtures for TIG and plasma welding
The right gas mixtures
for TIG and plasma welding.
TIG welding is one of the most popular processes for welding
stainless steels where high quality welds with good surface
finish are very important. Plasma welding is less commonly
used although it produces high quality welds especially if a
key hole technique is used.
There is a greater number of shielding gas mixtures that can be
used for TIG welding stainless steel than for steel, but not all
gas mixtures are suitable for all material types, i. e. hydrogen
­containing mixtures are suitable for welding only austenitic types
and nitrogen containing mixtures for duplex types of stainless steel.
Argon 4.6
Argon is the simplest gas for TIG welding stainless steels and nickel
alloys. It produces a stable welding arc and is suitable for all grades
of stainless steel. However, as the thickness of the material increases,
fusion and porosity problems can arise, due to the arc being more
­viscous and more difficult to manipulate.
Argon can also be used as a purging gas should this be required.
The right gas mixtures for TIG and plasma welding
09
VARIGON
H2
VARIGON H2
VARIGON H5
This two component argon and hydrogen mixture is the preferred gas
mixture for manual TIG welding of austenitic grades of stainless steels.
This gas mixture has a higher hydrogen content than VARIGON H2 and
is most commonly used for welding thicker sections. Although it can be
used manually, it is best suited to automatic and orbital TIG welding of
austenitic stainless steels.
The addition of hydrogen to the shielding gas helps to scavenge oxygen
close to the weld pool giving a very clean weld surface, minimising the
need for any post weld cleaning. This can be a significant cost saving
especially if chemical cleaning agents were previously required. It also
helps to speed up the manufacturing process by removing one task.
VARIGON H2 produces a more fluid weld pool which not only increases
the welding speed but also makes it easier for the welder to mani­pulate
the weld pool, giving a neater, more consistent weld appearance.
Increasing the welding speed reduces the time to manufacture a
­component, making it cheaper to produce.
By making it easier for the welder to use, it reduces the risk of w
­ elding
defects such as porosity and fusion problems. With high value raw
­materials such as stainless steel, the scrapping or repairing of welding
defects can be a significant cost and must be avoided.
The addition of hydrogen to argon has the benefit of reducing the amount
of ozone generated when welding. This is achieved by the chemical
reaction between ozone and hydrogen. The lower the ozone levels when
welding, the less the hygienic burden on the welder.
VARIGON H5 has a much more fluid weld pool, which can be used to
increase the welding speed. This is particularly useful in ­automatic
welding applications where the maximum speed the gas is capable
of delivering can be achieved. Higher welding speeds will reduce the
weld cost for any component produced.
In addition to increasing the welding speed, the more fluid weld pool
also gives good weld penetration and fusion. These characteristics ensure
that low defect levels occur, reducing weld repair and scrapping costs.
10
The right gas mixtures for TIG and plasma welding
VARIGON
H5
VARIGON H10
VARIGON N2.5
This argon and hydrogen mixture is used primarily for plasma welding
and automatic TIG welding of austenitic stainless steels.
This mixture of argon and nitrogen is specifically designed for welding
duplex stainless steels.
The fluid weld pool makes this mixture ideal for key hole plasma
welding. It can weld thicker materials with high welding speeds and
high production rates, but careful control of the welding process is
required to reduce the chance of losing the weld pool.
The nitrogen in the gas mixture helps to balance the weld metal
microstructure improving the in-service corrosion performance,
particularly pitting corrosion resistance. As duplex stainless steels
are used for their good corrosion resistance, a shielding gas which
can improve this property will help maintain the design life of a
­component, reducing scrapping rates and additional costs.
VARIGON H10 can also be used for automatic TIG welding where speed
is a priority, as it helps to control distortion. Fusion and penetration
­levels are increased, which is useful when welding thicker materials
but can be a problem for thinner sections. These features will help
reduce defect levels and scrapping costs.
The right gas mixtures for TIG and plasma welding
all types
types of
of stainless
stainlesssteels
steels
Gases for all
Argon 4.6
VARIGON H2
VARIGON H5
VARIGON H10
VARIGON N2.5
VARIGON He30
Types of
­stainless
steel suitable
all
austenitic
austenitic
austenitic
duplex
all
Welding
speed
Porosity ­
control
The greater the number of dots, the better the gas performs.
VARIGON He30
This argon and helium gas mixture is suitable for TIG welding all grades
of stainless steel.
The addition of helium to argon increases the available energy to the
weld pool making it more fluid. This in turn increases the penetration
profile and weld fusion characteristics. Both these features will help
reduce defect levels, reducing scrapping rates and rework, both of
which are expensive and must be carefully controlled.
Welding speeds are also higher than with pure argon and this helps
reduce production costs and improve productivity.
Fusion
Penetration
Ease of use
Thickness
range (mm)
0 to 3
0 to 10
1 to 10+
6 to 10+
0 to 10
0 to 10
11
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With its innovative concepts, Linde is playing a pioneering role in the global market. As a technology leader, it is our
task to constantly raise the bar. Traditionally driven by entrepreneurship, we are working steadily on new high-quality
products and ­innovative processes.
Linde offers more. We create added value, clearly discernible competitive advantages, and greater profitability.
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solutions. This applies to all industries and all companies regardless of their size.
If you want to keep pace with tomorrow’s competition, you need a partner by your side for whom top quality, process
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Linde – ideas become solutions.
Linde AG
Gases Division, Seitnerstrasse 70, 82049 Pullach, Germany
Phone +49.89.7446-0, Fax +49.89.7446-1216, www.linde-gas.com
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