Minneapolis Oxygen Company offers a complete line of specialized shielding and cutting gases required for efficient and high-quality metal fabrication.

Shielding Gases
Argon and other shielding gas mixtures are used during the welding process to shield welds as they solidify, preventing oxidation. These gases significantly improve quality, reduce waste, boost productivity and decrease fumes.

Gases for Gas Metal Arc Welding (GMAW)
Gas Metal Arc Welding (GMAW) is used to weld all commercially important metals, including steel, aluminum, copper, and stainless steel. The process can be used to weld in any position, including flat, vertical, horizontal, and overhead. It is usually connected to use direct current electrode positive (DCEP). It is an arc welding process that incorporates the automatic feeding of a continuous, consumable electrode that is shielded by an externally supplied gas.

Argon
Argon (Ar) is used on nonferrous base metals such as aluminum, nickel, copper, magnesium alloys, and reactive metals, such as zirconium and titanium. Argon provides excellent arc welding stability, penetration, and bead profile on these base metals. When welding ferrous-based metals, argon is usually mixed with other gases, such as oxygen, helium, carbon dioxide, or hydrogen.

The low ionization potential of argon helps create an excellent current path and superior arc stability. Argon produces a constricted arc column with high current density which causes the arc energy to be concentrated over a small surface area.

Carbon Dioxide
Carbon dioxide (CO₂ ), a reactive gas, dissociates into carbon monoxide and free oxygen in the heat of the arc. Oxygen then combines with elements transferring across the arc to form oxides from the weld pool in the form of slag and scale, generating a great deal of smoke and fumes. Although carbon dioxide is an active gas and produces an oxidizing effect, sound welds can be consistently achieved with pure CO₂ .

Carbon dioxide is often used in its pure form with welding of carbon steel, because it is readily available and produces good welds at low cost. However, this may be a false economy as the low cost per unit of gas does not always translate to the lowest cost per foot of deposited weld. Other factors, such as lower deposition efficiency due to spatter loss, can influence the final weld cost and should be carefully considered.

Carbon dioxide will not support spray transfer. Metal transfer is restricted to the short circuiting and globular modes. A major disadvantage of carbon dioxide is harsh globular transfer with its characteristic spatter.

The weld surface resulting from carbon dioxide shielding is usually heavily oxidized. An electrode with higher amounts of deoxidizing elements is needed to compensate for the loss of alloying elements across the arc. This may cause problems when the completed part requires paint. The advantages of carbon dioxide are good width of fusion and the achievement of good mechanical properties.

Helium
Helium (He) is a chemically inert gas that is used for welding applications requiring higher heat inputs. It may improve wetting action, depth of fusion, and travel speeds. It does not produce the stable arc provided by argon. Helium has higher thermal conductivity than argon and produces a wider arc column. The higher voltage gradient provides a higher heat input than argon, promoting greater weld pool fluidity and better wetting action. This is an advantage when welding aluminum, magnesium, and copper alloys.

Argon-Oxygen Mixtures -- Minneapolis Oxygen Company's ArgoSheild Blends
The addition of small amounts of oxygen to argon greatly stabilizes the welding arc, increases the filler metal droplet rate, lowers the spray transition current, and influences bead shape. The weld pool is more fluid and stays molten longer, allowing the metal to flow out towards the weld toes.

StainSheild Gas Blend
This blend is primarily used for spray transfer on stainless steels. One percent oxygen is usually sufficient to stabilize the arc and improve the droplet rate and bead appearance.

ArgoSheild universal Gas Blend
This blend is used for spray arc welding of carbon steels, low-alloy steels and stainless steels. It provides greater wetting action than the 1% oxygen mixture. Weld mechanical properties and corrosion resistance of welds made with 1% and 2% oxygen additions are similar. However, bead appearance will be darker and more oxidized for the 2% blends with stainless steels.

ArgoSheild Gas Blend
This blend provides a more fluid but controllable weld pool. It is the most commonly used argon-oxygen mixture for general carbon steel welding. The additional oxygen also permits higher travel speeds.

Argon-Carbon Dioxide Mixtures -- Minneapolis Oxygen Company's ArgoSheild Blends
Argon-carbon dioxide blends are mainly used on carbon and low-alloy steels and have limited application on stainless steels. Carbon dioxide added to argon, at higher current levels, increases spatter.

In GMAW, a slightly higher current level must be reached when using argon-carbon dioxide in order to establish and maintain stable spray transfer. Above approximately 20% carbon dioxide, spray transfer becomes unstable and periodic short-circuiting and globular transfer occurs.

ArgoSheild C-5 Gas Blend
This blend is used for pulsed spray transfer and short-circuiting transfer on a variety of material thicknesses. A 5% mixture may be used for GMAW-P of low alloy steels for out-of-position welding. The arc forces that develop give this mixture more tolerance to mill scale and a more controllable puddle than an argon-oxygen blend.

ArgoSheild C-10 Gas Blend
This blend performs similarly to the ArgoSheild C-5, but with increased heat input providing a wider, more fluid weld puddle in either short-circuit or spray transfer.

ArgoSheild C-15 Gas Blend
This blend has been used for a variety of applications on carbon and low-alloy steels. In the short-circuit mode of transfer, maximum productivity on thin gauge metals can be achieved with this blend. This is done by minimizing the excessive melt-through tendency of higher carbon dioxide mixes, while increasing deposition rates and travel speeds. As the carbon dioxide percentages are lowered from the 20% range (maximum spray arc levels), improvements in deposition efficiency occur due to decreasing spatter loss. This blend will support the spray arc mode of transfer.

ArgoSheild C-20 Gas Blend
May be used for short circuiting or spray transfer welding of carbon steel.

ArgoSheild C-25 Gas Blend
This blend is commonly used for GMAW with short-circuiting transfer on low carbon steel. It was formulated to provide optimum droplet frequency on short-circuiting transfer using .035 and .045 diameter wire. Minneapolis Oxygen Company's ArgoSheild C-25 operates well in high current applications on heavy base metal. It promotes good arc stability, weld pool control, and weld bead appearance. This blend will not support the spray type mode of metal transfer.

Argon-Carbon Dioxide-Oxygen Mixtures -- Minneapolis Oxygen Company's StainSheild Blends

StainSheild Gas Blend
Mixtures containing these three components are versatile, due to their ability to operate using short-circuiting, globular, spray, pulsed, and high-density transfer modes. Several ternary compositions are available and their application depends on the desired metal transfer mode.

The advantage of this blend is its ability to shield carbon steel and low-alloy steel of all thicknesses using any metal transfer mode applicable. Minneapolis Oxygen Company's StainSheild produces good welding characteristics and mechanical properties on carbon low-alloy steels and some stainless steels. On thin gauge base metals, the oxygen constituent assists arc stability at very low current levels (30 to 60 amps) permitting the arc to be kept short and controllable. This helps minimize excessive melt-through and distortion by lowering the total heat input into the weld zone. StainSheild is generally used for spray arc welding, providing high deposition rates and often higher travel speeds than carbon dioxide.

SpecSheild Gas Blend
The carbon dioxide and oxygen levels in Minneapolis Oxygen Company's SpecSheild blend are balanced to produce excellent arc stability and arc performance in demanding automatic and robotic applications. High quality welds at higher levels of productivity are produced with this shielding gas mixture. The SpecSheild blend will help to develop excellent weld metal strength and toughness as well as improved fatigue strength in a number of application areas.

Argon-Helium Mixtures -- Minneapolis Oxygen Company's AlumSheild Blends
Helium is often mixed with argon to obtain the advantages of both gases. Argon provides good arc stability and cleaning action, while helium promotes wetting with a broad width of fusion.

Argon-helium blends are used primarily for nonferrous base metals, such as aluminum, copper, nickel alloys, magnesium alloys, and reactive metals. Helium additions to an argon-base gas will increase the heat input. Generally, the thicker the base metal, the higher the percentage of helium. Small percentages of helium, as low as 20%, will affect the arc. As helium percentages increase, the arc voltage, spatter, and weld width to depth ratio increase, while porosity is minimized in aluminum. The argon percentage must be at least 20% when mixed with helium to produce and maintain a stable spray transfer.

AlumSheild A-25 Gas Blend
This blend is used for welding nonferrous base metals when an increase in heat input is needed and weld bead appearance is of primary importance.

AlumSheild A-50 Gas Blend
This blend is used primarily for high-speed mechanized welding of nonferrous materials under 3/4 inch thick.

AlumSheild A-75 Gas Blend
This blend is used for mechanized welding of aluminum greater than one inch thick in the flat position. It increases heat input and reduces porosity of welds in copper.

Argon-Helium-Carbon Dioxide Mixtures -- Minneapolis Oxygen Company's SpecSheild Blends
Helium and carbon dioxide additions to argon increase the heat input to the weld, which improves wetting, fluidity, and weld bead profile. Patents and pending patents cover GMAW with such three-part blends.

SpecSheild Gas Blend
This blend has been developed for spray and pulsed spray arc welding of both carbon and low-alloy steels. It can be used on all thicknesses in any position. This high-speed blend will produce higher quality welds over rust, oil, and mill scale than conventional two-part mixtures. It produces good mechanical properties and weld puddle control.

SpecSheild Gas Blend
This blend is used for short arc, spray, and pulsed spray arc welding of stainless steel. It provides a higher welding speed, a broad weld with a flat crown and good color match, reduced porosity, and excellent alloy retention with good corrosion resistance.

SpecSheild A-1025 Gas Blend
This blend is widely used for short-circuiting transfer welding of stainless steel in all welding positions. The carbon dioxide content is kept low to minimize carbon absorption and assure good corrosion resistance, especially in multipass welds. The argon and carbon dioxide additions provide good arc stability and depth of fusion. The high helium content provides significant heat input to overcome the sluggish nature of the stainless steel weld pool.

Gases for Flux-Cored Arc Welding (FCAW)

Carbon Dioxide
The majority of flat-position large-diameter (> 1/16") flux-cored wires that use a secondary shielding gas use carbon dioxide. The arcs are generally quiet with high deposition rates and are good for welding over rust and mill scale on heavy plate.

Argon-Carbon Dioxide Mixtures -- Minneapolis Oxygen Company's ArgoSheild Blends
Most of the small-diameter (< 1/16") and all position cored wires use an argon-based shielding gas. These gas blends provide greater weld puddle control lower welding fume and are preferred by welders because of ease of use.

Argon-Oxygen Mixtures -- Minneapolis Oxygen Company's ArgoSheild Blends
Small amounts of oxygen may be added to argon for welding carbon steels; however, shielding gas blends, such as argon-2% oxygen, are used primarily for Gas Metal Arc Welding (GMAW) of stainless steels.

Gases for Gas Tungsten Arc Welding (GTAW)

Argon
Argon, an inert gas, is the most widely used (in its pure form) as a shielding gas for Gas Tungsten Arc Welding (GTAW). Its mild thermal conductivity produces a narrow, constricted arc column which allows greater variations in arc length with minimal influence on arc power and weld bead shape. This characteristic makes it the preferred choice for manual welding. In addition, argon provides good arc starting due to its low ionization potential. This property allows argon to carry electric current well when compared to other shielding gases.

For AC welding applications, argon is preferred over helium because of its superior cleaning action, arc stability, and weld appearance. When welding thicker aluminum alloys (> 1/4"), argon is mixed with helium to enhance the thermal conductivity of the shielding gas.

While pure argon may be used for mechanized applications, depending on the base material, thickness and composition, argon-helium or argon-hydrogen blends promote higher welding travel speeds. The hotter arc characteristics of argon-helium blends also make them more suitable for welding metals with high thermal conductivity, such as copper.

Helium
Helium, also an inert gas, has high thermal conductivity and high ionization potential, which produces higher arc voltages when compared to argon for a given current setting and arc length. This produces a "hotter" arc. The increased heat input affects depth of penetration and its wider, less constricted arc column increases weld bead width.

The use of helium is generally favored over argon at the higher current levels which are used for the welding of the thicker materials, especially those having high thermal conductivity or relatively high melting temperatures. It is often used for high-speed mechanized applications.

Although argon is widely used for AC welding of aluminum, pure helium has been successfully used for DCEN mechanized welding of this material. It produces greater penetration at higher travel speeds. However, surface oxides must be cleaned from the weld joint to obtain acceptable results, since the cleaning action of the AC arc is not present. Argon-helium mixtures are widely used with AC current when welding with aluminum alloys.

The physical properties of helium definitely offer advantages in some applications. However, due to it high ionization potential, it also produces a less stable arc and a less desirable arc starting characteristic than argon. Its higher cost and higher flow rates are also factors to be considered. In some cases, an argon mixture is used for igniting the arc and pure helium is used for welding. This technique is used for DC GTAW welding of heavy aluminum.

Argon-Helium Mixtures -- Minneapolis Oxygen Company's AlumSheild Blends
Each of these gases (argon and helium), as explained above, has specific advantages. Minneapolis Oxygen Company's AlumSheild blends (argon-helium blends) are basically used to increase the heat input to the base metal while maintaining the favorable characteristics of argon, such as arc stability and superior arc starting.

AlumSheild A-75 Gas Blend
This blend is sometimes used for DC welding when it is desirable to obtain higher heat input while maintaining the good arc starting behavior of argon.

AlumSheild A-50 Gas Blend
This blend is used primarily for high-speed mechanized and manual welding of nonferrous material (aluminum and copper) under 3/4 inch thick.

AlumSheild A-25 Gas Blend
The speed and quality of AC welding on aluminum can be improved with this blend. It is sometimes used for manual welding of aluminum pipe and mechanized welding of butt joints in aluminum sheet and plate. The AlumSheild A-25 gas blend is also used for many of the GTAW hot wire applications to increase the energy input while accommodating the high filler metal deposition rates of the process.

Argon-Hydrogen Mixtures -- Minneapolis Oxygen Company's SpecSheild Gas Blends

Hydrogen is often added to argon to enhance the thermal properties of argon. Its reducing effect improves weld surface color match with 300 series stainless alloys due to reduced surface oxidation.

The higher arc voltage associated with hydrogen increases the difficulty of starting the arc. For this reason, the lowest amount of hydrogen consistent with the desired result is recommended. Additions up to 5% for manual welding and up to 10% for mechanized welding are typical.

Argon-hydrogen blends are primarily used on austenitic stainless steel (300 series), nickel, and nickel alloys. Hydrogen enhanced mixtures are not recommended to weld carbon or low-alloy steel, or any of the copper, aluminum, or titanium alloys since cracking or porosity will occur due to the absorption of hydrogen.

Argon-hydrogen blends utilized as a purge gas are successfully applied to improve root appearance when TIG welding 300 series stainless pipe.

Warning
Special safety precautions are required when mixing argon and hydrogen. Do NOT attempt to mix argon and hydrogen from separate cylinders.

Minneapolis Oxygen Company's SpecSheild is a hydrogen-enhanced argon-based blend which is ideally suited for general purpose GTAW of most commercially available carbon, low alloy, and stainless steels. It may be substituted for pure argon in many applications.

SpecSheild H-2 and H-5 Gas Blends
These blends are used for manual welding applications. The HydroStar H-5 blend is preferred on material thicknesses above 1/16 inch. These blends are also suitable for use with GTAW when welding 300 series austenitic stainless steels and as a back purge gas on stainless steel materials.

SpecSheild H-10 Gas Blend
This blend is preferred for high-speed GTAW mechanized applications on austenitic stainless steel.

SpecSheild H-15 Gas Blend
This blend, which contains 15% hydrogen, is used most often for welding butt joints in stainless steel at speeds comparable to helium, and 50 percent faster than argon. The HydroStar H-15 blend is also used to increase the speed of welding 300 series stainless steel. It can be used on all thicknesses of stainless steel. Concentrations greater than 15% may cause weld metal porosity, with multi-pass applications.

SpecSheild H-35 Gas Blend
It is recommended as the plasma gas with plasma arc gauging, when cutting aluminum and stainless steel and when cut quality and face appearance are critical.

Note: Oxygen and carbon dioxide are chemically reactive and should not be used with GTAW. Their oxidation potential can cause severe erosion and degradation of the tungsten electrode at arc temperatures.

Gases for Plasma Arc Welding (PAW)
The physical configuration of PAW requires the use of two gases, a "plasma" or orifice gas and a shielding gas. The primary role of the plasma gas, which exits the torch through the center orifice, is to control arc characteristics and shield the electrode. The shielding gas, introduced around the periphery of the arc, shields or protects the weld. In many applications, the shielding gas is also partially ionized to enhance the plasma gas performance.

Low current (< 100 amps)
Argon is the preferred plasma gas because its low ionization potential ensures easy and reliable starting. Argon-helium mixtures are also used for applications requiring higher heat input.

The choice of shielding gas is dependent on the type and thickness of the base material. When welding aluminum, carbon steel, and copper, the gases commonly used are argon, helium, and argon-helium mixtures. It is generally recommended that the percentage of helium be increased as the base-plate thickness increases. When welding low alloy steels, stainless steels, and nickel alloys, the aforementioned gases in addition to argon-hydrogen mixtures are used.

High Current (> 100 amps)
The choice of gas used for high current plasma arc welding also depends on the material to be welded. In all but a few cases, the shielding gas is the same as the orifice gas.

Shielding Gases:

Argon
Argon is suitable as the orifice and shielding gas for welding all metals, but it does not necessarily produce optimum welding results. In the Melt-In mode, additions of hydrogen to argon produce a hotter arc and more efficient heat transfer to the work. Limits on the percentage of hydrogen are related to its potential to cause cracking and porosity. However, when using the Keyhole technique, a given material thickness can be welded with higher percentages of hydrogen. This may be associated with the Keyhole effect and the different solidification pattern it produces.

Argon is used for welding carbon steel, high strength steel, and reactive metals such as titanium and zirconium alloy. Even minute quantities of hydrogen in the gas used to weld these materials may result in porosity, cracking, or reduced mechanical properties.

Argon-Helium Mixtures -- Minneapolis Oxygen Company's SpecSheild Blends
Helium additions to argon produce a hotter arc for a given arc current. Argon-helium mixtures containing between 50% and 75% helium are generally used to make keyhole welds in heavier titanium sections and for fill and capping passes on all materials when the additional heat and wider heat pattern of these mixtures prove desirable.

Argon-Hydrogen Mixtures -- Minneapolis Oxygen Company's SpecSheild Blends
Argon-hydrogen mixtures are used as the plasma and shielding gases for making keyhole welds in stainless steel, Inconel, nickel, and copper-nickel alloys.

Permissible hydrogen percentages vary from 5% to 15%, used for highest welding speeds in stainless steel in tube mills. See Table 5 for high-current gas selection.

Cutting Gases

Gases for Oxyfuel Cutting
The principal flame cutting fuels are acetylene, methylacetylene-propadiene (MPS), natural gas, and propane

Acetylene (C₂H₂)
Acetylene has a high heat release in the primary flame and a low heat in the secondary flame. It has the hottest flame temperature of the commercially available fuel gases (6,300°F) and is an excellent choice for welding, brazing and cutting of steel alloys less than 2 inches in thickness.

Methylacetylene-propadiene (CH₃C:CH)
Methylacetylene-propadiene-stabilized fuel gas has a high heat release in its primary and secondary flames. The heat release in the primary cone is slightly lower than acetylene. The outer flame temperature is similar to propane and FG-2 gas.

Methylacetylene-propadiene-stabilized mixtures combine the qualities of an acetylene flame with a more even heat distribution. The mixture burns hotter than propane or natural gas.

Methylacetylene-propadiene-stabilized preheat flame (inner cones) are at least 1.5 times longer than acetylene preheat flame (inner cones) when used with one-piece tips. Gases of this type commonly use two-piece tips, which will help to lessen preheat times and have the same length cones as acetylene. Training is often required in order to use methylacetylene-propadiene-stabilized fuel gas to its best advantage.

Natural gas (Methane CH₄)
This product is usually supplied through low-pressure pipelines from a local utility. Injector torches are recommended in order to overcome the low delivery pressure. Preheat time is longer than the other commonly available fuel gases. One benefit is that cylinders and bulk storage vessels are not required.

The cost of natural gas is less than other fuel gases, but increased preheat times usually make this a false economy.

Propane (C₃H₈)
The flame temperature of the oxy-propane flame is lower than acetylene and Minneapolis Oxygen Company's FG-2 gas flames. The primary flame releases low Btu when compared to the FG-2 gas or acetylene, which increases preheat time. The heat distribution in the flame can be an advantage with thick material.

Propane is commonly used by scrap yards where cut quality is not critical. Where cut quality is not a concern, propane may be a cost-effective fuel gas.

Gases for Plasma Arc Cutting (PAC)

Virtually all plasma cutting of mild steel is done with one of three gas types:

The first two have become standard for high-speed mechanized applications. Argon-hydrogen and nitrogen-hydrogen (20% to 35% hydrogen) are occasionally used for manual cutting, but dross formation may be a problem with the argon blend. Dross is a tenacious deposit of re-solidified metal attached at the bottom of the cut. A possible explanation for the heavier, more tenacious dross formed in argon is the greater surface tension of the molten metal. The surface tension of liquid steel is 30 percent higher in an argon atmosphere than in nitrogen. Air cutting gives a dross similar to that formed in a nitrogen atmosphere.

Pure nitrogen is sometimes used to increase torch consumable life (up to 50% greater when compared to air) but it will reduce the cutting capacity of the plasma by approximately 25%. In other words, a plasma rated at cutting one inch with air can cut 3/4" with nitrogen. Surface oxidation with N2 is substantially reduced when compared to air. This is useful when cutting stainless and nickel alloys.

Oxygen is being more widely applied as a plasma gas with mechanized cutting. Rare earth consumables have been developed which help to maintain acceptable consumable life while enhancing cutting speed on mild steel. Note: Nitrogen may be required to initiate the arc.

The plasma jet tends to remove more metal from the upper part of the workpiece than from the lower part. This results in cuts with non-parallel cut surfaces which are generally wider at the top than at the bottom. The use of argon-hydrogen, because of its uniform heat pattern or the injection of water into the torch nozzle (mechanized only), can produce cuts that are square on one side and beveled on the other side. For base metal over three inches thick, argon-hydrogen is frequently used without water injection.

Lasing Gases
CO2 lasers utilizes a mixture of N2/CO2/He as the laser media which is typically supplied in a high purity grade in varying volumes depending on the equipment manufacturer. Moisture and hydrocarbon levels are critical, as poor attention to this property could result in poor lens life. Minneapolis Oxygen Company laser gases are recommended by several manufacturers.

Select a gas from the list of the below for more information about gas applications and supply options.