What shielding gases are used in welding?

Welding gas mixtures - choosing a protective environment for arc welding

Welders often underestimate the contribution of the protective environment to the welding process. Some pure gases and welding gas mixtures can affect metal transfer, alloy composition, weld shape, smoke production and many other characteristics.

The correct selection of shielding gas for electric arc welding (MAG), submerged arc welding (FCAW), and tungsten arc welding (TIG) can significantly increase process intensity, quality, and deposition rates for a given weldment structure.

Impact of clean gases on quality and productivity

The pure gases used in welding are argon, helium and carbon dioxide. They can have both positive and negative effects on the arc.

Welding using argon

Argon (Ar) is a monatomic chemical element that is widely used in its pure form and as part of many welding gas mixtures. Argon is completely inert, which makes it suitable for working with refractory and chemically active materials. It has low thermal conductivity and ionization potential, thereby providing low heat transfer to the environment surrounding the arc.

This creates a narrow arc column, which in turn results in the usual penetration profile for argon - deep and relatively narrow. When working with argon, there is a slight tendency to undercut the fusion zone and enlarge the weld, which is due to the lack of heat at the outer edges of the weld pool in both TIG and MAG.

In MAG, pure Ar promotes jet transport of metal.

Read more about the features of this gas in the article: argon gas - chemical properties and scope of application.

Helium (He) is a monatomic inert gas most often used for welding non-ferrous metals with a non-consumable electrode. Unlike argon, helium has high conductivity and ionization potential, which contributes to the opposite results. Helium gives a wide profile, good wetting at the weld edges and higher temperatures than pure Ar.

High ionization potential can make it difficult to initiate an arc unless high-frequency or capacitive arc initiation methods are used to work with the tungsten electrode. In addition, a higher gas flow rate is recommended since helium tends to rise in the air.

Pure helium promotes large droplet transfer of the electrode material and is rarely used for GMAW, with the exception of pure copper.

Carbon dioxide (CO2) is a two-component gas used in MAG and FCAW. CO2 is a complex molecule with rather complex interactions in an arc. At arc temperatures, carbon dioxide breaks down into CO and O2. This creates the potential for oxidation of the base material and decomposition of the weld pool or weld alloy.

CO/O2 recombination gives a fairly broad penetration profile at the weld surface, while the low ionization potential and thermal conductivity creates a hot region in the center of the arc column. This gives the entire joint a well-balanced width-to-depth penetration profile.

In the case of electric arc welding, pure carbon dioxide cannot create a jet transfer of metal, but only large droplets, which can lead to a large amount of spatter.

How are welding gas mixtures supplemented?

Oxygen (O2) is a diatomic active component commonly used in gas mixtures for the electric arc welding process in concentrations below 10%. Oxygen has a heat input potential arising from both its ionization energy and its dissociation energy (the energy released by breaking a molecule into individual atoms in an arc).

The picture shows the name of the chemical element and its properties.

Oxygen creates a very wide and relatively shallow penetration profile with a high level of heat input at the surface.

Because the high level of heat reduces the surface tension of the molten metal, jet transfer is facilitated, as is moisture at the weld located at the edge of the outer surface of the weld.

O2/Ar mixtures exhibit a penetration profile at the nailhead level in electric arc welding of carbon steel, which is the most common application. O2 is also used in trimixes with CO2 and Ar, where it provides metal wetting and jetting benefits.

Hydrogen (H2) is a diatomic active gas that is often used in protective welding compounds in concentrations less than 10%. Hydrogen is primarily used in austenitic stainless steels to facilitate the removal of oxides or to increase heat input.

As with all diatomic molecules, the result is a hotter, wider weld. Hydrogen is not suitable for working with ferritic or martensitic steels due to cracking problems.

At higher concentrations (30-40%) H2 can be used to plasma cut stainless steels to increase power and reduce dross.

Nitrogen (N2) is the least commonly used additive for protective purposes. Nitrogen is mainly used to produce austenite and to improve corrosion resistance in duplex and super-duplex steels. For a more detailed introduction to this chemical element, read the article: technical nitrogen and its demand in the industrial sector.

Selecting shielding gas for a specific type of welding

In welding, different gas mixtures are used, the choice of which depends on the technology and material used.

MAG: carbon steel

The most commonly used mixtures for this material are Ar/CO2, Ar/O2, or all three.

The figure shows an example of a semi-automatic welding machine from Kaiser

• In Ar/CO2, the CO2 content varies from 5% to 25%. Low carbon dioxide formulations are typically used for metal jet transfer on large cross-sectional materials, or when low input temperatures and shallow penetration are required in thin materials.

The high content makes it possible to work in short circuit mode and provides additional cleaning action and deep penetration in large cross-section materials. However, an increase in carbon dioxide content also means an increased rate of consumption of alloying elements.

• In Ar/O2 mixtures, the O2 content varies from 2% to 5%. This protective environment is usually used when working on fairly clean materials. Many structural steel manufacturers use Ar/O2 because this shielding gas composition allows them to work on slightly oxidized base materials. Media containing oxygen must be assessed for depletion potential, which can be significant at high concentrations.

• O2 and CO2 in trimixes range from 2% to 8%. This type of compound works well in both jet and short-circuit transfer applications and can be used on materials of varying thicknesses.

Oxygen tends to promote metal jet transport at low voltages, while carbon dioxide promotes penetration.

 Trimixes containing Ar, CO2 and O2 make it possible to carry out metal transfer at lower voltages than many Ar/CO2 binary mixtures.

MAG: carbon steel

The most common gases for working with stainless steel are Ar/CO2 and He/Ar/CO2.

The figure shows a steel classification scheme

• Ar/CO2 mixtures typically have about 2% oxygen and perform well in metal jetting as long as slight discoloration of the weld is tolerated.

• Trimixes are available in two main types: Ar-saturated and He-saturated. Trimixes saturated with helium (about 90%) are used for operation in short circuit mode. They include a small amount of argon to stabilize the arc and a very small amount of carbon dioxide for penetration and cleaning.

Argon-saturated gases typically have about 80% Ar, 1-2% CO2, and He in the remainder.

They are traditionally used for metal jetting because the high argon content allows the process to be carried out at relatively low voltages, while the helium gives good wettability, a flat bead profile, and good color matching.

TIG: aluminum 

Electric arc welding of aluminum is usually performed with pure argon. However, when working with large sections, it is possible to increase the helium content to 75%. Helium allows for significantly better wettability compared to pure argon and a thinner weld pool, which allows more time for impurities that cause porosity to escape. Higher helium concentrations require significantly higher voltages for jet metal transfer than is the case with pure Ar.

You can also watch a short video about welding thin aluminum using the TIG method:

By the way, you will find more publications about welding mixtures in this section of our blog.

FCAW: Carbon and Stainless Steel

Flux technology is most often performed in a protective environment consisting of 20-25% carbon dioxide and balanced with argon.

This composition makes it possible to obtain good technical characteristics of the arc: CO2 improves penetration and gives good scale formation, while Ar reduces the release of by-product gases. Sometimes part of the carbon dioxide is replaced with helium in order to further reduce gas emissions.

Alloy depletion is not a concern when working with flux, since the elements susceptible to the effects of carbon dioxide are balanced by the flux content when producing the welding wire.

TIG: stainless steel and aluminum 

While most tungsten welding processes use pure argon, some mixtures are designed to facilitate penetration and wettability into aluminum and stainless steel. Most are Ar/He mixtures, with helium content ranging from 10% to 75%.

As with electric arc welding, this addition of helium facilitates wettability in large-grade aluminum and stainless steel, where low weld pool mobility is undesirable. For 300 series stainless steel, gas containing 2% to 5% hydrogen can be used.

This additive makes the finished seam look much better.

At the Promtekhgaz company you can buy protective welding gas mixtures at an affordable price and with the possibility of prompt delivery to the production facility.

Source: http://xn--80affkvlgiu5a.xn--p1ai/svarochnye-smesi-gazov-vybiraem-zashhi/

Gases used in gas welding

Gas welding is the melting of the edges of the parts to be joined in a high-temperature torch flame to form a seam. The choice of gas for welding depends on many factors:

• metal to be joined;
• desired seam shape;
• type of gas equipment;
• working conditions;
• properties of chemical composition;
• required melting temperature.

Let's list what gases are used in gas welding: it can be acetylene, MAF, propane, butane, benzene, kerosene, oxygen, coke and carbon dioxide and others. The most actively used is acetylene, which in the presence of oxygen gives a temperature of 3 thousand degrees.

Acetylene

Pure acetylene (C2H2) is colorless, with a pungent odor of garlic, leaving a sweetish taste in the mouth when inhaled. It is light (lighter than air) and quite harmful to humans. Acetylene can be obtained either on site (combining calcium carbide with water) or transporting it ready-made in gas cylinders.

Calcium carbide is a solid crystalline substance formed by melting lime and coke at a temperature of 19002300C. For large volumes of work, it is beneficial to use acetylene generators; in other cases, it is convenient to take acetylene from cylinders.

The advantages of this gas include a high combustion temperature, ease of production, and ease of regulation. The disadvantages include its explosiveness and considerable cost.

Acetylene substitutes

Substitute gases for C2H2 include propane and propane-butane mixture, hydrogen, coke oven gas, gasoline, and kerosene. They have fairly high calorific values. However, for high-quality work, more oxygen is required, and the flame t is still lower than that of acetylene. Therefore, propane, butane and other options are used more often in the manufacture of metal structures from non-ferrous, low-melting metals. It is difficult to join steel with them.

Oxygen

This is a combustion catalyst that must be used in gas welding regardless of the gas selected. The oxygen supplied to the burner should ideally be absolutely pure. The maximum temperature that develops during operation depends on this, which affects the quality of the seams. Technical oxygen has 3 grades of purity: from 99.7% to 99.2%. The better the quality, the higher the gas welding speed and the lower the consumption.

Oxygen gas is colorless and transparent, odorless and tasteless, heavier than air. It is obtained by deep cooling from air, or by electrolysis from water. It can be stored and used in gaseous form in cylinders or in tanks in liquid form. With an excess of O2, the metal seam oxidizes, which reduces the strength of the product. Therefore, it is important to control the percentage of gaseous substances.

Carbon dioxide

Carbon dioxide (CO2) has a strong odor and pronounced oxidizing properties. It dissolves well in water and weighs one and a half times more than air. There are 3 types of substances that are used to join cast iron, carbon metals and alloys, corrosive steels and low-alloy structures.

Protective elements

Gas welding also uses inert gases, which serve to protect the weld pool from air. They do not interact with metal and do not dissolve in it; they are colorless and odorless.

• Argon. Non-flammable, 1.5 times heavier than air. The highest grade is used for argon arc welding of active, rare metals and alloys. The first is suitable for aluminum and steel products.
• Helium. Lighter than air. Recommended for gas welding of pure and active metals, as well as aluminum and steel.
• Nitrogen. Suitable for copper and copper alloys. There are 4 types of nitrogen with different proportions of the substance.

Welding mixtures improve the process and quality of the weld in the manufacture of metal structures: helium with argon, argon with oxygen and/or carbon dioxide as an assistant, and others.

Source: http://kra-ber.ru/gazy-ispolzuemye-pri-gazovoj-svarke/

Shielding gases. Inert, active gases and mixtures. General technical requirements. | Welding and Control

Inert gases, active gases and their mixtures are used as shielding gases during fusion welding.

Noble gases

Inert welding gases

Inert gases are gases that are not capable of chemical reactions and are practically insoluble in metals. These are monatomic gases, the atoms of which have outer electron shells filled with electrons, which determines their chemical inertness. Among the inert gases used for welding are argon, helium and their mixtures.

Argon grade A is recommended for welding and melting active and rare metals (titanium, zirconium and niobium) and alloys based on them, as well as for welding particularly critical products from other materials at the final stages of manufacturing.

Argon grade B is intended for welding and melting with consumable and non-consumable tungsten electrodes of alloys based on aluminum and magnesium, as well as other alloys that are sensitive to impurities of gases soluble in the metal.

Argon grade B is recommended for welding and melting chromium-nickel corrosion-resistant and heat-resistant alloys, alloy steels of various grades and pure aluminum.

Helium , like argon, is chemically inert, but unlike it, it is much lighter. Helium is lighter than air, which complicates the protection of the weld pool and requires greater consumption of shielding gas. Compared to argon, helium provides more intense heating of the welding zone, which is caused by a large gradient of voltage drop in the arc. Helium is supplied according to MRTU 51-77-66 in two grades - high-purity helium and technical helium.

Inert gas mixtures:

Argon and helium. Having a higher density than helium, such mixtures better protect the metal of the weld pool from air. An inert gas mixture consisting of 70 vol.% argon and 30 vol.% helium has especially good protective properties. The density of such a mixture is close to the density of air.

For welding chemically active metals, an inert mixture containing 60-65 vol. is used. % helium, and the rest is argon. Inert gas mixtures, although noticeably more expensive than argon, surpass it in the intensity of heat release from the electric arc in the welding zone.

This is essential when welding metals with high thermal conductivity.

Mixtures of inert and active gases are increasingly used in consumable electrode welding of steels of various classes due to their technological advantages:

• lower intensity of chemical action on the metal of the weld pool compared to active gases;
• high stability of the arc process;
• favorable nature of the transfer of electrode metal through the arc.

Argon and oxygen (another oxidizing gas). significantly increases the stability of arc combustion and improves the quality of weld formation. The presence of oxygen in the arc atmosphere promotes finer droplet transfer of the electrode metal. This is due to the surface-active effect of oxygen on iron and its alloys.

By dissolving in liquid metal and accumulating mainly on the surface, oxygen significantly reduces its surface tension. As a result, the formation of individual metal droplets is facilitated and their size is reduced.

Therefore, for welding steel, not pure argon is used, but mixtures with oxygen and carbon dioxide Ar-O2, Ar-CO2, Ar-CO2-O2.

An argon-hydrogen mixture (up to 20 vol.%H2) is used for microplasma welding. The presence of hydrogen in the mixture ensures compression of the plasma column, making it sharper and more concentrated. In addition, hydrogen creates a reducing atmosphere necessary in some cases in the welding zone.

Active gases

Active shielding gases are gases that can protect the welding zone from air access and at the same time chemically react with the metal being welded or physically dissolve in it. When arc welding steel, carbon dioxide is used as a protective medium. Due to its chemical activity towards tungsten, welding in this gas is carried out only with a consumable electrode.

The use of carbon dioxide provides reliable protection of the welding zone from contact with air and prevents nitriding of the weld metal. Carbon dioxide has an oxidizing and also carburizing effect on the metal of the weld pool. Of the alloying elements in the bath, aluminum, titanium and zirconium are most strongly oxidized; silicon, manganese, chromium, vanadium, etc. are less intensely oxidized.

Previously, an obstacle to the use of carbon dioxide as a protective medium was the pores in the joints. The pores were caused by boiling of the solidifying metal of the weld pool due to the release of CO due to its insufficient deoxidation. The use of welding wires with a high silicon content eliminated this drawback, which made it possible to widely use carbon dioxide in welding production.

Finds industrial application in welding low-carbon and low-alloy structural steels.

General technical requirements for protective gases

Shielding gases (active, inert gases and their mixtures) for mechanized and automatic welding must comply with the requirements of GOST 10157 (argon gas of the highest grade), GOST 8050 (carbon dioxide gaseous and liquid of the highest grade), technical specifications and quality certificates.

The technical requirements for shielding gases are given in the table below.

Indicator name	Requirement
a) Argon gas must have: - a volume fraction of argon no less than - a volume fraction of nitrogen no more than - a volume fraction of oxygen no more than - a mass concentration of water vapor at 20 °C and a pressure of 760 mm. Hg Art. no more	99.9930% 0.0050% 0.0007% 0.01 g/cm3
b) Carbon dioxide, gaseous and liquid, must have: - the volume fraction of carbon dioxide is not less than - the dew point is not higher	99.6% -48 °C
c) A mixture of argon gas and carbon dioxide must have: - mass fraction of moisture no more than - volume fraction of nitrogen no more than - maximum deviations of the volume fraction of carbon dioxide depending on the composition of the mixture: - 15% CO2-85% Ar - 25% CO2-75 % Ar—50% CO2-50% Ar	0,008 % 0,010%     ± 1,5% ± 2,5 % ± 5,0 %

Source: https://svarkka.ru/%D0%B7%D0%B0%D1%89%D0%B8%D1%82%D0%BD%D1%8B%D0%B5-%D0%B3%D0% B0%D0%B7%D1%8B-%D0%B8%D0%BD%D0%B5%D1%80%D1%82%D0%BD%D1%8B%D0%B5-%D0%B3%D0% B0%D0%B7%D1%8B-%D0%B0%D0%BA%D1%82%D0%B8%D0%B2%D0%BD%D1%8B%D0%B5/

What gas is used in welding?

The possibility of semi-automatic welding of materials in a carbon dioxide environment was discussed in the mid-twentieth century. This technique was developed by N.M. Novozhilov. and Lyubavsky K.V. - Soviet researchers. This welding method, due to the low cost of carbon dioxide and its high degree of productivity, has become quite popular in the construction and manufacturing industries, and, of course, in everyday life.

The essence of gas welding technology

According to this technique, carbon dioxide, which provides protection in the area being connected, is divided into O2, carbon monoxide, under the influence of the high temperature of the arc. As a result, the flow of the resulting gas mixture protects the material welding zone from the negative effects of environmental air and interacts with carbon and iron.

To prevent the oxidation of CO2, manganese and silicon are introduced into the rod for gas welding, which are more chemically active than iron; they are oxidized first. Therefore, as long as Mn and Si are present at the junction of metal products, carbon and iron will not be oxidized.

To obtain high-quality welds when welding carbon steels, the manganese/silicon ratio is 1/2. The resulting oxides of manganese and silicon do not dissolve in the weld pool during work; they form a low-melting compound after reacting with each other. This compound is easily removed from metal in a liquid state.

Features of welding work in a carbon dioxide environment

Semi-automatic welding in a carbon dioxide environment is performed with direct current of reverse polarity, since direct polarity current negatively affects the stability of the arc (the weld will have defects).

Welding can also be done using alternating current, but then an oscillator must be used in the circuit.

Gases used for gas welding

There are several options for types of welding. They differ from each other in the technology of forming a weld pool, which has a high temperature, the purpose of which is joining, cutting metals and their alloys. This can be done with a gas flame, ultrasound or electric arc. The principle of joining metals is based on melting the edges of individual metal structures to further join them together, resulting in a weld.

Depending on the gas used for welding, the temperature will differ. For example, when interacting with calcium carbide H2O, acetylene is released. During the reaction of this element with oxygen, the flame temperature can reach more than 3000ºC.

Welding gases are all butanes, propanes, benzenes, MAF, kerosenes, etc. When using any gases for welding, the presence of oxygen is required - this is a combustion catalyst. O2 must be pure and high quality. The maximum temperature will depend on this.

Gas composition

The gas composition must contain pure oxygen, which makes it possible to obtain the maximum combustion temperature and important flame indicators. The completeness of combustion of combustible components will depend on the quality of this component, and the oxidation and reduction characteristics obtained by the flame will depend on its quantity.

There are special requirements for gas storage conditions. The use of special containers (cylinders) is mandatory because:  

• most welding gases are toxic;
• technical oxygen is a powerful catalyst.

If you use atmospheric oxygen, the welds will not be smooth. Moreover, after melting and subsequent joining, the metal will lose its original qualities. The use of standard oxygen, which is contained in the atmosphere, is not effective enough. It contains various impurities that significantly reduce the rate of combustion of the components, and this accordingly affects the temperature of the burner flame.

Gases for welding

Important! It is necessary to observe the proportions of gas mixtures when using any type of gas. The choice itself will depend on the material being welded. For example, to join steel samples, the gas composition must contain 18% carbon dioxide, and to join stainless steel materials, the mixture must consist of 98% argon.

Mechanized gas shielded welding involves the use of active, inert gases. They do not dissolve in metals and are not poisonous.

Types of gases:

• N2 is nitrogen, a colorless, odorless gas. Used for joining copper materials. There are four types of nitrogen with different contents of the substance.
• He – helium, a colorless, odorless gas, lighter than air. There are two types of helium: technical, high-frequency. Due to its high cost, this gas is less in demand on the market. Helium is intended for joining samples of aluminum, pure metals, and steel.
• Ar – argon, a colorless, odorless gas, weighs 1.5 times more than air, does not burn. There are two types of this gas: 1st grade (for samples made of aluminum, steel), premium grade (for semi-automatic welding in a shielded gas environment of samples from rare metal alloys).

Active gases protect the welding area from air. They react and dissolve in metals.

• Carbon dioxide (CO2) is characterized by increased oxidative characteristics and has a specific odor. Its mass is 1.5 times that of air, it dissolves in H2O. I distinguish three types of this gas, which are used for welding cast iron materials, low and medium carbon metal alloys, corrosive, low alloy steel samples. Important to remember! Gas shielded welding does not involve the use of carbon dioxide.
• Oxygen O2 is a fairly powerful catalyst, colorless, tasteless, odorless, does not burn, but supports combustion. Used in combination with inert components.

The most popular gas mixtures, which improve the quality of the seam, improve the joining process itself:

• carbon dioxide plus oxygen
• argon plus helium
• carbon dioxide plus argon
• carbon dioxide "plus" oxygen "plus" argon
• oxygen plus argon

Advantages and disadvantages of gas welding

Gas shielded welding is characterized by melting of the material. The process itself is based on the connection of individual elements of preheated metal until melting. To do this, a high-temperature burner flame is used, which is formed during the combustion of a gas composition with oxygen. The gap between the samples is filled with pre-melted metal wire.

• fairly simple welding technology;
• there is no need to purchase expensive, technically complex equipment;
• no need for a special power source;
• The welder has the ability to adjust the rate of heating and cooling of the material being joined by welding, changing the power and the position of the burner flame relative to the point being welded.

Source: https://electrod.biz/tehnologii/gaz-dlja-svarki.html

Advantages of gas shielded welding

One of the most common and frequently used methods of joining two metals is gas shielded welding. The gas used enters directly into the welding zone, preventing the formation of oxides, that is, it prevents oxygen from entering the seam. Thanks to this welding technique, the connections are sealed and clean and comply with state standards.

Manual welding method

Two types of manual electric arc welding are carried out on semi-automatic machines. It can be local or general in a chamber with controlled atmosphere. The first type is used more often and requires less cost. With local exposure, shielding gas is supplied to the welding area from the torch nozzle.

This method allows you to weld diverse products of any thickness and complexity, but does not ensure 100% weld quality. Where there is a laminar gas flow, the protection works unambiguously, but where the flow is mixed with other substances, the strength of the seam decreases.

Therefore, the welder’s skills also lie in the correct location of the weld pool so that it is located in the source of the flow.

With increased quality, a special camera is applied to the condition of the seam. It creates excessive pressure. Parts and a welding unit with automatic wire feed are placed there. Under such conditions, they work with metals with increased chemical activity, for example, molybdenum or titanium. Then we can guarantee that the joint will be monolithic and meet the required quality standards.

Welding in shielding gases is performed with consumable and non-consumable electrodes.

Pros and cons of semi-automatic welding

The undeniable advantages of manual local welding include:

• the strength of the connection is higher than with conventional electric arc welding;
• most gases used for welding are low in cost;
• for an experienced welder it will not be difficult to master this welding method;
• when using shielding gas, it is possible to connect thick and thin metals;
• the process speed is much faster;
• there are no difficulties in working with materials such as aluminum, non-ferrous and corrosion-resistant metals,
• The welding technology is compatible with mechanical and automatic processes.

Disadvantages exist, like any technological operation:

• for work carried out outdoors, an additional purchase of a protective screen is required to prevent air vortices from mixing with the gas stream;
• For interior work, powerful ventilation or long-term ventilation is required;
• When using argon, you will have to spend money on purchasing it. The price of this gas is an order of magnitude higher than the others.

But these disadvantages do not affect the quality of welding, but only require additional preparation.

What gases are used in welding

To protect products from interaction with air, inert and active gases are used. They are designated as MIG (metal inert gas) and MAG (metal active gas), respectively.

Helium and argon are inert gases; when they interact with metal, they form a kind of shell that prevents air from entering the weld pool. Gases do not react with metal and do not dissolve in it. They have proven themselves in working with aluminum, magnesium and titanium. Using a tungsten electrode, the semi-automatic welding process will be optimal for refractory steels, active metals or for welding critical structures.

Nitrogen, carbon dioxide, hydrogen and oxygen are active gases. Working with carbon dioxide has been widely used due to its low price.

Carbon dioxide welding

Inexpensive to produce, carbon dioxide reliably protects the metal from oxidation and is in greatest demand in semi-automatic welding in protective environments.

Due to a chemical reaction when heated, carbon dioxide breaks down into carbon monoxide and oxygen. As a result, three gases enter the weld pool at once, one of which has a negative effect on the metal. Therefore, silicon and manganese are added to the filler wire. They react earlier than oxygen, resulting in the formation of a protective environment that prevents oxidation.

The combination of silicon and manganese produces a light substance that forms slag, but it is easily cleaned off, but the functions of carbon dioxide are not impaired.

Water in a carbon dioxide cylinder is not acceptable. It is necessary to completely remove the remaining water, otherwise a small amount or remaining moisture will spoil the seam. The joint will be porous.

Welding using nitrogen

Nitrogen does not react with copper, so it is used when welding copper parts and some types of stainless steel. Carbon and graphite electrodes are used; it is not advisable to use an infusible tungsten rod, since there is a possibility of overuse.

The arc voltage should be in the range of 22-30 Volts, the welding current in the range of 150-500 Amps, the approximate gas consumption per minute is 10 liters. The nitrogen in the cylinder is stored under a pressure of 150 atmospheres.

The design of the device is the same as for other types of welding using shielding gases, with the exception of a special holder for carbon wire.

Welding equipment

The main parameters of equipment for welding in shielding gases are the following indicators:

• large range of welding current that can be adjusted;
• selection of voltage for stable arc burning;
• wire dispensing speed;
• additive thickness.

In most cases, welding inverters are used that are equipped with a current adjustment function with a large plug. Also, the convenience of work includes automatic wire feeding. If you are working with consumable electrodes, use direct or pulsed current.

There are many modes of semi-automatic welding; depending on the welding elements, all parameters change.

It is necessary to carry out all preparatory work before starting the welding process. Carefully remove edges from grease, paint, varnish, rust and other contaminants. Use metal scrapers, solvents and non-cloth rags.

There is a certain algorithm of actions when working with protective gases. First of all, gas is supplied, then the inverter is turned on, then the filler rod begins to flow and the arc is ignited. And only after all these steps do you begin the welding process.

After the arc goes out, gas is still supplied to the welding area for a few seconds. This is necessary to ensure that all air is removed from the metal area.

Based on the thickness and type of alloy, select the appropriate shielding gas. Argon provides a stable welding arc, and with the help of helium, the weld is welded deeper. Hydrogen is used in welding copper products. Argon is considered a universal gas for welding, but its high cost forces welders to replace it with more affordable gases.

Source: https://svarka-weld.ru/preimushchestva-svarki-v-srede-zashchitnyh-gazov

Welding gas: what it is, where it is used, features of use, pros and cons

Beginning welders usually try to use simple welding methods. Most people use manual arc welding.

For most repair work or the manufacture of simple parts, this is enough. However, sooner or later you will want to try something new and improve your skills.

The next step after manual welding can be welding using semi-automatic equipment. With this method, shielding gas is used to protect the surfaces being welded from oxidation.

Below you will find out which one and how to use it for welding work.

Welding gas

Semi-automatic welding uses inert gases such as argon, helium, carbon dioxide. Less commonly used are hydrogen, nitrogen and oxygen. It is served in cylinders of various sizes.

The most common volume is 40 liters. During welding, the gas forms a protective zone that protects the arc from exposure to the atmosphere, and the welded surfaces from oxidation and pores. When using it, the seam turns out smooth and of high quality.

Experienced welders know the recipes for mixtures, the use of which allows you to take advantage of the advantages of each of the gases that make up the mixture.

Characteristics

Let us dwell in more detail on the various types of gaseous substances used for welding work.

Most often used for these purposes. There is even a separate welding method that uses its name - argon arc. Inert, colorless and odorless, not chemically active towards metals and other substances. Much heavier than air, due to this it creates a reliably protected zone in the welding area.

It comes second in popularity. It is also inert, however, unlike argon, helium is lighter than air. Due to this, much more is consumed.

Considering that its cost is noticeably higher than that of argon, this is a significant drawback. However, this does not prevent its frequent use.

It is especially widely used when working with metals coated with an oxide film. These are metals such as stainless steel, aluminum, etc. When using helium, metals melt evenly, which is especially important when welding parts of large thickness.

In addition to pure helium and argon, mixtures are often used. The most common proportion is 60% helium and 40% argon.

The mixture is quite expensive, but it can be used to qualitatively weld materials with high thermal conductivity. The risk of burning through the metal is greatly reduced.

Colorless, heavier than air. Due to this, the welding area is reliably protected. There are two categories. The first category is recommended for use, however, due to its cost and scarcity, attention is often paid to the second category. The big minus of carbon dioxide of the second category is the presence of water vapor in the composition. When used, may cause the formation of pores in the metal. The problem can be avoided by adding some argon to the carbon dioxide.

It is not used in its pure form, as it causes oxidation of the surface, which negatively affects the quality of the seam. It is usually added to mixtures when it is necessary to obtain a wide and shallow joint.

It is colorless and odorless. Typically used for plasma cutting of stainless steel, achieving very good results. When welding other metals, it can cause the formation of defects, such as cracks. Requires increased attention to compliance with safety regulations due to increased flammability.

Also colorless and odorless, non-flammable. Used in liquid and gaseous form. The scope is also narrow; it is used mainly only when welding copper. When welding other metals, it can negatively affect the strength of the seam.

Choosing gas for welding

To make it easier for you to choose the right gas for welding work, we present you with a correspondence table.

Finally

Develop, experiment, try mixtures with different proportions, and you will see how the quality of the weld improves.

If you don’t want to experiment, use reference materials and select the appropriate gas or mixture for your work. We wish you success in your work!

Source: https://prosvarku.info/rashodnye-materialy/svarochnyj-gaz

Selection of welding shielding gas

Welders and welders often overlook the shielding gas they use and its contribution to the welding process.

Shielding gases affect the metal transfer mode, the properties and geometry of the weld, smoke and many other characteristics of the weld.

The correct choice of shielding gas for metal arc welding processes such as TIG welding and semi-automatic MIG MAG welding can dramatically improve weld speed, weld quality and penetration depth.

Clean welding gases

The clean gases used for welding are argon, helium, and carbon dioxide. These gases can have both positive and negative effects on the arc welding process and the appearance of defects in the weld.

• Argon 100% argon is commonly used for TIG welding of all materials and MIG welding of non-ferrous metals. Argon is chemically inert, making it suitable for welding reactive and refractory metals. This gas has low thermal conductivity and ionization potential, which results in low heat transfer to the outer region of the welding arc. As a result, a narrow arc column is formed, which in turn creates a welding seam profile traditional for welding in pure argon: deep and relatively narrow.
• Helium Helium is also a monatomic inert gas, and is most often used for TIG welding of non-ferrous metals. Unlike argon, helium has high thermal conductivity and ionization potential, which give the opposite effect than when welding in argon. Helium provides a wide weld profile, good edge wetting and higher heat input than pure argon.
• Carbon dioxide Carbon dioxide CO2, the active gas, is commonly used for semi-automatic MAG short arc welding and MAG cored wire welding. CO2 is the most common reactive gas used in MAG welding. And the only gas that can be used in its pure form without adding an inert gas. Carbon dioxide is one of the cheapest shielding gases, making it an attractive choice when material costs are a major priority in the welding process. CO2 provides very deep penetration, which is useful for welding thick metal, however, when welding in this gas, the welding arc is less stable, which leads to a lot of spatter. Also, its use is limited to short arc welding and makes jet transfer welding impossible.

Welding gases used as components of the welding gas mixture

• Oxygen Oxygen is a diatomic, active shielding gas usually used for MIG MAG welding as one of the components of the welding mixture, in a concentration of less than 10%. Oxygen provides a very wide weld profile with shallow penetration and high heat input to the metal surface. Oxygen-argon mixtures have a characteristic weld penetration profile in the form of a “nail head”. Oxygen is also used in ternary mixtures with CO2 and argon, where it provides good wettability and the benefits of jet transfer.
• Hydrogen Hydrogen is a diatomic, active component of the shielding gas, usually used in the welding mixture in a concentration of less than 10%. Hydrogen is used primarily in welding austenitic stainless steel to remove oxide and increase heat input. As with all gases made from diatomic molecules, the result is a wide weld seam on the surface. Penetration is increased. Hydrogen is not suitable for ferritic or martensitic steels due to cracking. Hydrogen can be used in higher concentrations (30 to 40%) for plasma cutting stainless steel - to increase power and reduce slag.
• Nitrogen Nitrogen is used least often for protective purposes. It is mainly used to improve corrosion resistance in duplex steels.

Welding gas mixtures

Depending on the welding process and welding materials, many different welding gases and their mixtures are used:

TIG welding	MIG MAG welding
Welding gas or mixture	Steel	Stainless steel	Aluminum	Steel	Stainless steel	Aluminum
Argon (Ar)	X	X	X	X
Helium (He)		X
Carbon dioxide (CO2)	X
Ar/CO2 mixture	X	X
Ar/O2 mixture	X	X
Ar/He mixture	X	X	X	X
Ar/CO2/O2 mixture	X
Ar/H2 mixture	X
Ar/He/CO2 mixture	X	X
He/Ar/CO2 mixture	X

The cost of welding gas against the background of the total cost of welding work

If you look at the distribution diagram of the cost of welding work, you can see that the cost of welding gas is only 2-5% of all welding costs. However, these costs should not be underestimated.

The choice of the correct gas and its quality significantly influence the consumption of welding materials, the geometry of the weld seam and the entire welding process as a whole. The choice of gas also affects the labor expended on correcting defects and processing the weld after welding.

We hope this article was useful to you. On this site you will find many other interesting and useful articles. Thank you

Smart Technics

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Read 62751 times Last modified Friday, 06 December 2013 06:37

Source: http://www.Smart2Tech.ru/vybor-svarochnogo-zashchitnogo-gaza

Which shielding gas to use when welding and cutting: choice and features | Tiberis

Auto repair shop workers, installers and other welding specialists often use natural gas and various gas mixtures during welding. You will learn about what types of gases there are, their features and properties from our article. We will also provide recommendations on the selection and use of one or another shielding gas for different welding methods and depending on the material being welded.

Why are shielding gases needed when welding and cutting?

Shielding gas is an important component that ensures productivity and decent quality of the welding process.

The name of the shielding gas speaks for itself; it is needed to protect the hardening molten weld seam from oxidation, as well as from moisture and impurities in the air that can reduce the resistance of the seam to corrosion processes, lead to the appearance of pores and weaken the strength of the seam, affecting the geometry of the weld connections. In addition, the shielding gas cools the welding gun.

What types of gases are used for welding and cutting: their properties and application features

Inert and active gases, as well as their mixtures, are used as shielding gases used for welding.

1. Inert gases for welding . Inert gases are gases that are not capable of chemical reactions and are practically insoluble in metals. The atoms of such gases are endowed with outer electron shells filled with electrons, which explains their chemical inertness. These include argon, helium and their mixtures.

Argon ( Ar ) is an inert gas that does not enter into chemical reactions with molten metal and other gases in the arc combustion zone.

The advantages of this inert gas include the fact that it is 38% heavier than air; argon displaces it from the welding zone and reliably isolates the weld pool from contact with the atmosphere.

Most often, Ar is used as a shielding gas in the process of argon arc TIG welding and MIG/MAG welding. Examples of metals welded using argon and application features are given below in Table 1.

Argon is in demand as a shielding gas:

• in construction and mechanical engineering (when welding parts made of high-alloy steel; rapid cutting of metals, including thick sheets of refractory metals);
• in the mining industry and metallurgy (metal smelting; removal of gas inclusions from liquid steel).

Helium ( He ), like Ar, is chemically inert, but differs from it in that it is much lighter than air, which makes protecting the weld pool a more complex process that requires large amounts of shielding gas.

Helium is used as an inert shielding gas during welding of stainless steels, non-ferrous metals and alloys, active and chemically pure materials. It provides increased penetration, and therefore is sometimes used to melt thick metal sheets or obtain a specially shaped weld.

But due to the increased consumption and high cost of helium compared to argon, its scope of application is quite limited.

Helium (He) is used as a shielding gas:

• when welding stainless steels, non-ferrous metals and alloys, chemically pure and active materials.

1.1. Inert gas mixtures usually include argon and helium. Having a higher density than helium, such mixtures provide more reliable protection of the weld pool metal from air.

If it is necessary to weld chemically active metals, an inert mixture containing 60-65 vol. is often used. % He, 40-35 vol. %Ar. Inert gas mixtures are noticeably more expensive than pure argon, but provide a more intense release of heat from the electric arc at the welding site. This is significant for semi-automatic welding of metals characterized by high thermal conductivity.

2. Active gases for welding . These are gases that protect welding from air access and at the same time enter into chemical reactions with the metal being welded or physically dissolve in it.

Carbon dioxide ( CO2 ) (carbon dioxide) is a colorless, non-poisonous gas, soluble in water, and heavier than air.

Carbon dioxide gas for welding should not contain mineral oils, glycerin, hydrogen sulfide, hydrochloric, sulfuric and nitric acid, alcohol, ethers, ammonia, organic acids and water. Due to the rarity of grade 1 welding carbon dioxide, grade 2 welding carbon dioxide and food grade carbon dioxide are used for welding.

But, an increased content of water vapor in such carbon dioxide during welding leads to the appearance of pores in the seams and a decrease in the plastic properties of the welded joint.

In the welding process, solid carbon dioxide can also be used, corresponding to GOST 12162-66 of two grades - food grade and technical grade. When welding low-carbon and low-alloy structural steels, a gas mixture of carbon dioxide and oxygen (CO2 + + O2) is also used. Use a mixture that includes 30 vol. % oxygen. The mixture of CO2 + O2 has a more intense oxidizing effect on liquid metal, in contrast to pure carbon dioxide.

Carbon dioxide is used as a protective agent:

• in construction and mechanical engineering (electric welding; fine sharpening processes, cold fitting of machine parts)

Oxygen ( O ) is included in the gas mixtures CO2 + O2 and Ar + O2. It is a colorless, odorless gas that supports combustion. In case of cooling to a temperature of -183 degrees. Celsius, oxygen turns into a mobile blue liquid, and at a temperature of -219 degrees.

Celsius freezes. Oxygen guarantees a very wide weld profile, characterized by shallow penetration, and also provides a high heat input to the metal surface.

Oxygen-argon mixtures are distinguished by a special weld penetration profile, reminiscent of a “nail head”.

Oxygen as a protective gas is sometimes necessary:

• in construction and mechanical engineering (oxygen-acetylene gas cutting and gas welding of metals, surfacing and spraying of metals, plasma cutting of metals)

Hydrogen ( H ) is colorless, odorless, and flammable. Hydrogen is not suitable for martensitic or ferritic steels due to cracking, but can be used in concentrations of 30 to 40% for plasma cutting stainless steel to increase power and reduce slag.

• Hydrogen has found application in atomic hydrogen welding.

Nitrogen ( N ) is a colorless and odorless gas that does not burn and does not support combustion. In accordance with GOST 9293-59, nitrogen comes in four grades: electric vacuum, gaseous gaseous 1st grade, gaseous 2nd grade and liquid. The inclusion of nitrogen in these varieties must be, respectively, no less than vol.%: 99.5; 99.9; 99 and 96. The main impurity in each of them is oxygen.

Nitrogen is most often used as a shielding gas:

2.1. Mixtures of inert and active gases are increasingly used in the process of consumable electrode welding of steels of various classes due to their technological advantages. These include:

• high arc stability, favorable character of electrode metal transfer through the arc,
• the degree of chemical action on the metal surface of the weld pool is lower when compared with active gases.

The addition of a small amount of oxygen or other oxidizing gas to argon significantly increases the stability of arc combustion and improves the quality of formation of welded joints. Oxygen in the arc atmosphere provides fine-droplet transfer of the electrode metal.

Selecting a gas for a specific type of metal being welded

What gas is used when welding a particular metal is one of the most frequently asked questions for beginners in welding on thematic forums. Examples of the use of various shielding gases and gas mixtures for welding various metals are given in the table.

Metal to be welded	Shielding gas used in welding	Features of the welding process
Carbon steel	75% Ar+25% CO2	High speed of the welding process without burning through metal up to 3 mm thick, minimum deformation and spatter formation
CO2	Deep penetration, high welding speed
Stainless steel	90% He,5% Ar+2.5% CO2	No oxidation of the welded metal and no burn-through, small heat-affected zone,
Low alloy steel	60-70% He+25-35% Ar+4.5% CO2	High impact strength, minimal reactivity,
75% Ar+25% CO2	Sufficient strength, small spatter along the contour of the welded joint, high arc stability.
Aluminum and its alloys	Ar	Stable arc and excellent transfer of electrode material during the welding process of thick parts. up to 25 mm
35% Ar+65% He	Greater heat input compared to welding with pure argon, improved fusion characteristics, used when welding thick metal. 25- 76 mm
25% Ar5% He	Maximum heat input, low porosity, used when welding metal over 76 mm
Magnesium alloys	Ar	Impeccable seam quality (cleanliness)
Stainless steel	Ar-1%O	Improved arc stability, good weld bead fusion, more fluid controllable weld pool, minimal burn-through when welding heavy stainless steels
Ar+2% O	Stable arc, fusion and welding speed than 1% oxygen, used for welding thin stainless steels
Carbon steel	Ar+1-5% O	Improved arc stability, excellent weld bead contour fusion, more fluid controlled weld pool, minimal burn-through, faster welding speed compared to pure argon welding
Ar +3-10%	Beautiful weld seam, welding only with electrode positioning, minimal spatter formation
Low alloy steels	Ar+2% O	Low risk of burn-through, weld strength
Titanium	Ar	Good arc stability
Copper, nickel and their alloys	Ar	It is characterized by good fusion, reduced metal fluidity, and is used for welding thick metal. up to 3 mm
Ar+80-75% He	Characterized by increased heat input
Copper, duplex steel
N	Demanded for protecting the root of the seam. Reduces the formation of oxide films at the root of the weld

By correctly determining the type of shielding gas, you will ensure the efficiency and quality of welding, as well as guarantee an excellent welded joint and penetration depth, increase the reliability of the created seam and the quality of the part. The selection of a suitable shielding gas and its quality significantly influence the consumption of welding consumables, the labor of the welder and the correction of defects and the final processing of the weld joint.

If you have any questions on the topic, we recommend that you find the most up-to-date information on our website, or directly contact Tiberis consultants.

Source: https://www.tiberis.ru/stati/vybor-zashhitnogo-gaza-dlja-svarki

Shielding gases for welding – Osvarke.Net

Shielding gases are inert and active gases that are used in several welding processes, primarily for mechanized welding and manual tungsten arc welding.

The purpose of the shielding gas is to protect the welding zone from exposure to oxygen and other elements in the air. Depending on the material being welded, the influence of atmospheric gases can complicate the welding process and lead to a decrease in the quality of the seam. Shielding gases are divided into two categories: inert and active.

Incorrect welding gas selection can result in weld porosity, weak arc and excessive metal spatter.

Inert protective gases

Inert gases are used for welding with a tungsten electrode, as well as for welding non-ferrous metals in a shielded gas environment. Among the noble gases, only two, argon and helium, are economical enough to be used in welding. In their pure form, argon and helium are used only for some non-ferrous metals.

Argon (Ar) is a colorless gas, odorless, non-flammable, 1.5 times heavier than air. Argon does not dissolve in metals. Recommended for welding steels and pure aluminum.

Helium (He) is a colorless gas, odorless, lighter than air, and therefore requires increased gas consumption. At the same current values, an arc in helium releases up to 2 times more energy than in argon. Helium is used for welding chemically pure and active materials, as well as aluminum and magnesium alloys.

Nitrogen (N2) does not react with copper, so when welding copper and its alloys, nitrogen can be considered an inert gas.

They are capable of protecting the welding zone from exposure to air, but they themselves dissolve in the liquid metal or enter into chemical interaction with it. Active shielding gases include carbon dioxide, oxygen, nitrogen and hydrogen. Most of these gases affect the quality of the weld and the welding process, but when used in controlled quantities they can improve the properties of the weld.

Oxygen (O2) is an odorless, tasteless and colorless gas. It is a non-flammable gas, but actively supports combustion. It is not used independently as a shielding gas, but is used for preparing welding mixtures with inert and active gases.

Carbon dioxide (CO2) is a colorless gas with a slight odor, with pronounced oxidizing properties. Carbon dioxide is 1.5 times heavier than air, suitable for welding cast iron, low- and medium-carbon steels, low-alloy corrosion-resistant steels.

Hydrogen (H) - Used to weld nickel and some stainless steels, especially thick parts. Improves metal flow and surface finish, but may cause brittleness when interacting with carbon steels, so its use is limited to some stainless steels.

Gas mixtures

Gas mixtures serve to improve the welding process and the quality of the weld by using the strengths of each gas.

A mixture of argon and carbon dioxide in a ratio of 75-80% and 20-25% reduces splashing of liquid metal, increases productivity and ensures good properties of the welding joint. Requires more thorough cleaning of welding edges before welding than when welding in pure carbon dioxide. Rational use for welding low-carbon and low-alloy steels.

A mixture of argon (50%) and helium (50%) is used for welding titanium and aluminum alloys.

A mixture of argon and oxygen (1-5%) helps stabilize the welding process, increases the fluidity of the liquid metal and causes small droplets of metal transfer. It is rational to use low-carbon steels and stainless steel for welding.

A mixture of carbon dioxide (60-80%) and oxygen (20-40%) increases the temperature of the molten metal and oxidizing properties. For welding in this mixture, wires with a high content of deoxidizing substances are used, for example, wire of the Sv-08G2STs brand. Rational use for welding carbon, alloy and some high-alloy steels.

A three-component mixture of argon (75%), carbon dioxide (20%) and oxygen (5%) gives the best effect when welding carbon steels, stainless and high-alloy steels. Stabilizes the welding process, reduces spatter, and avoids porosity of seams.

Source: http://osvarke.net/materialy/zashhitnye-gazy/

Choosing a welding shielding gas

Shielding gas plays a vital role in the process of creating a high-quality welded joint for the following types of welding:

• MIG - Metal Inert Gas. A method of arc welding in a protective atmosphere of inert gas using a consumable electrode in the form of steel or other wire, depending on the type of metal being joined.
• MAG - Metal Active Gas. The same method of semi-automatic welding, but in an active gas environment.
• TIG - Tungsten Inert Gas. Technology of arc welding in an inert gas environment with a non-consumable electrode.

Why is shielding gas needed in welding?

The weld pool is exposed to the negative influence of oxygen from the atmosphere, which can weaken the corrosion resistance of the weld, reduce its strength and lead to the formation of pores. The gas flow encloses the weld pool in a protective shell, protecting it from harmful external influences of atmospheric air, thereby protecting the solidifying molten weld from oxidation, as well as from impurities and moisture contained in the air.

Types of protective gases.

Inert. A type of gas that does not chemically interact with the heated metal and does not dissolve in it. Designed for welding aluminum, magnesium, titanium and their alloys, which when heated are prone to vigorous interaction with oxygen, nitrogen and hydrogen.

Example: Argon, Helium, Nitrogen (only when welding copper and copper alloys).

Active. They enter into a chemical interaction with the metal being welded and dissolve in it.

Example: Carbon dioxide, Hydrogen, Oxygen, Nitrogen.

Colorless, non-toxic, explosion-proof gas, tasteless and odorless. Typically used for TIG welding of all materials and MIG welding of non-ferrous metals such as aluminum. Argon is chemically inert, which makes it suitable for welding reactive and refractory metals. This gas has low thermal conductivity and ionization potential, resulting in low heat transfer to the outer region of the welding arc. As a result, a narrow arc column is formed, which in turn creates a welding seam profile traditional for welding in pure argon: deep and relatively narrow. Stored and transported in gray cylinders with green inscription.

Lighter than air, odorless, colorless, tasteless, non-toxic. It is a monatomic inert gas. Most often used for TIG welding of non-ferrous metals and for overhead position welding. Has high thermal conductivity and ionization potential. When welding with helium, the profile of the weld is wide, well wetted along the edge and with a fairly high heat input. Due to these features, it is most often used as an additive to argon and is used for welding chemically pure or active metals, aluminum or magnesium alloys, to ensure a large penetration depth. Stored and transported in brown cylinders with white lettering.

Carbon dioxide provides fairly deep penetration, so it is popular when welding thick metal. The disadvantages of welding in a carbon dioxide environment include a less stable welding arc, leading to large spatter formation. It can also only work on a short arc. Typically used for semi-automatic short arc MAG welding and MAG cored wire welding. Stored and transported in black cylinders with yellow inscription.

Welding gases used as components of the welding gas mixture:

Gas mixtures have higher technological performance than pure gases. When using them in the welding process, we get: fine-droplet transfer of liquid metal, the formation of a high-quality seam, and a reduction in losses due to spattering.

Oxygen is a diatomic, active protective gas. Typically used for MIG MAG welding as one of the components of the welding mixture, in a concentration of less than 10%. Oxygen provides a very wide weld profile with shallow penetration and high heat input to the metal surface. Oxygen-argon mixtures have a characteristic weld penetration profile in the form of a “nail head”. Oxygen is also used in ternary mixtures with CO2 and argon, where it provides good wettability and the benefits of jet transfer. Stored and transported in blue cylinders with black lettering.

Hydrogen is a diatomic, active gas. Used when welding austenitic stainless steel to remove oxide and increase heat input. The result is a wide weld with increased penetration. The concentration in the welding mixture is usually no more than 10%, and for plasma cutting of stainless steel from 30 to 40%. Stored and transported in green cylinders with red inscription.

Nitrogen is used least often for protective purposes of the weld pool. It is mainly used to improve corrosion resistance in duplex steels. Stored and transported in black cylinders with yellow inscription.

Welding gas mixtures:

They differ from chemically pure gases by higher technological indicators. They allow for fine-droplet transfer of liquid metal, form a better-quality seam and reduce losses due to spattering. Using a combination of welding gases, it is possible to increase the productivity of the welding process, increase the penetration depth, stabilize the electric arc, and improve the quality of the welded joint.

	Welding TIG	Welding MIG/MAG
Welding gas or mixture	steel	stainless steel steel	aluminum	steel	stainless steel steel	aluminum
Argon (Ar)	+	+	+	+
Helium (He)	+
Carbon dioxide (CO2)	+
Ar/CO2 mixture	+	+
Ar/O2 mixture	+	+
Ar/He mixture	+	+	+	+
Ar/CO2/O2 mixture	+
Ar/H2 mixture	+
He/Ar/CO2 mixture	+
Ar/He/CO2 mixture	+	+

The cost of welding gas compared to the overall cost of welding:
Do not underestimate welding gas by focusing solely on the equipment. If you carefully approach the issue of correctly selecting the required shielding gas, this will affect not only the quality of the welded joint and its geometry, but will also help avoid the costs of correcting defects and processing the final seam. Also, the choice of a suitable gas affects the consumption of welding materials by reducing spatter.

Source: https://www.svarbi.ru/articles/vybiraem-svarochnyy-zashchitnyy-gaz/