What is gas welding

The essence of gas welding

Welding is the most reliable and popular method of fastening two metal parts into one. It can be produced in several ways, one of which is gas welding. Let us take a closer look at the advantages and disadvantages of this method, the scope of application of this type of connection and the materials that are needed for soldering using gas welding.

Definition of Gas Welding

Gas welding of metals is a method of joining them that uses gases to create high temperatures. The most commonly used are oxygen and acetylene, although other options are possible.

The leading role here is given to the flame, because it is on it that the temperature height and the possibility of melting different types of metals depend.

The flame consists of three zones: the core (where acetylene decomposes), the reduction zone (in which carbon and hydrogen are oxidized) and the torch (the area of ​​complete combustion of gases). There are three types of them (depending on the ratio of gases - acetylene and oxygen):

• normal flame, in which gases are supplied in equal proportions. It is characterized by the blue color of all three zones, with the recovery zone having a bright blue color;
• a carburizing flame indicates a lack of oxygen and is characterized by a bright yellow flame;
• oxidizing is the one that occurs when there is a lack of acetylene, in which the flame is pale and short.

To work with gas welding, the master regulates the supply of working gases depending on the flame, the indicator of which is their color. The type of flame determines the temperature that affects the metal. This is usually over 3000 degrees, which allows you to melt and cut various types of products.

Gas welding and cutting of metals is usually carried out using a normal flame, in which acetylene and oxygen are supplied in equal quantities. If the color of the fire changes, you need to adjust the settings.

Scope of gas welding

Gas welding of metals can be carried out in several ways:

• gas flame welding occurs with the help of filler wire, which melts along with the main parts and fills the gap between them;
• Gas press welding is characterized by the absence of filler wire, and bonding occurs through a tight connection of molten edges.

Gas flame welding is not used for all types of metal. It has found its primary application in the following:

• tin and sheet steel, no more than 5 mm thick;
• non-ferrous metals;
• cast iron;
• tool steel.

All these metals have one thing in common - they require soft and smooth heating, which is provided by gas welding.

Gas welding and metal cutting has found wide application in many industrial and domestic sectors. Thanks to the gradual heating of the part, it does not deform and this method is considered one of the best for thin metals.

The main thing is to correctly adjust the gas supply and establish the flame. This is done as follows: the oxygen and acetylene valves are fully opened and the burner is ignited (with a match/lighter).

The adjustment is made using an acetylene valve with oxygen fully turned off.

The essence of gas welding can be seen in the figure below:

Gases used and their characteristics

Most often, a specific gas, acetylene (C2H2), is used for flame welding. It is characterized by a pungent odor and is produced by the reaction of calcium carbide with water (in an industrial setting). At temperatures above 335 degrees it lights up. In combination with oxygen, the ignition temperature is lower - 297 degrees minimum.

The main gas for gas press welding is oxygen, which is mixed with C2H2 in equal proportions. It is always sold in blue cylinders. Using a hose, oxygen is connected to the burner and supplied at low pressure, no more than 4 atm. C2H2 is connected to the hole nearby. the torch has a special mechanism for mixing gases and the concentrate for the welding process comes out through the tip.

Gas welding and cutting of metals can be carried out not only with acetylene. Instead, it is permissible to use other gases in liquid and vapor form. The most popular acetylene substitutes:

• Kerosene vapors (acetylene replacement ratio – 1:1)
• Propane (acetylene replacement ratio – 1:0.6)
• Methane (acetylene replacement ratio – 1:1.6)
• Hydrogen (acetylene replacement ratio – 1:5.2)

Important: when flame welding steel products with methane or propane, you need to use wire with a high concentration of manganese and silicon.

For high-quality melting of metal, it is recommended that the exposure temperature be twice as high as the melting temperature of this metal.

Advantages and disadvantages

Cooking using the gas method is not difficult, but it, like electric arc, semi-automatic or argon welding, has its advantages and disadvantages.

Advantages of gas connection:

• This is an ideal way to weld copper, brass and cast iron;
• materials with different levels of melting can be processed due to the high temperature generated as a result of combustion;
• you can cook anywhere, since no special equipment or electrical outlet is required;
• when using high-quality additional wire and a correctly selected flame, high-quality and beautiful seams are obtained (widely used for connecting components in pipelines);
• the work product heats up slowly, which avoids deformation or loss, as is the case with semi-automatic welding or when using an electrode).

In addition to the positive aspects, the essence of gas welding also has several disadvantages:

• the heating zone is quite wide, that is, not only the seam zone is heated, but also a large area around it. This may damage the product;
• inability to work with parts whose thickness exceeds 5 mm;
• It is highly not recommended to perform gas-flame overlapping welding, this will lead to deformation of the fusion site;
• high operational hazard, since gases form a chemical mixture that tends to ignite.

Technique and technology of gas welding

In order for gas flame welding to produce a high-quality weld, you must adhere to all recommendations and strictly follow the work technology. First, you need to prepare the edges of the products in the area of ​​the future seam, that is, clean them of various impurities and contaminants. This can be done with sandpaper or a mechanical iron brush. The technology for gas welding and metal cutting is selected in advance, before the start of the process.

Gas welding technology is divided into two methods:

• The right-hand welding method is characterized by the movement of the torch from left to right. In this case, the fiery flame is directed to the welded area, and the additional material is followed after it.
• The left welding method, accordingly, is performed in reverse - from right to left. The wire moves ahead of the flame, which is directed at the not yet connected edges of the parts.

The right-hand welding method is less popular, since the left-hand method is easier to see for the master and provides high-quality heating. Although with the right one, the efficiency is 20% higher and the gas consumption is lower.

Gas welding methods

Particular attention must be paid to the choice of filler wire. It depends on the thickness of the metal that needs to be welded. With the left method, the diameter of the filler wire is d=S/2+1 mm, and with the right method dS/2 mm, where S is the thickness of the product being welded (in millimeters).

The technique and technology of gas welding is selected based on several factors:

• product thickness;
• position of the part and width of the seam;
• master's preferences;
• gases used.

Recommendations

When studying the essence of the gas welding process, it is necessary to understand that working with flammable gases requires increased caution and attention. It is recommended for a beginner to take into account the advice of experienced welders and apply them in practice:

• for study and training it is better to use oxygen and acetylene;
• for welding with propane it is better to use a GZU 3-02 torch and Sv08g2s wire;
• before cooking the product, it must be thoroughly cleaned;
• for gas pressure welding, it is better to use hydraulic equipment (press) for reliable bonding;
• The left and right methods have their advantages and disadvantages, so the choice is made by the master, depending on the situation.

We reviewed the basic concepts and materials for flame and gas press welding. For them, a standard mixture of oxygen and acetylene is predominantly used. In some cases, propane welding is used for replacement. This process is not easy and has many nuances that will be difficult for a beginner to take into account. In this regard, novice welders are not recommended to weld with propane. The quality of the seam and the ease of work are affected by preliminary preparation.

Source: https://svarkaed.ru/svarka/vidy-i-sposoby-svarki/gazovaya-i-gazozashhitnaya-svarka/sut-gazovoj-svarki.html

Gas welding: technology, where it is used, types, pros and cons, equipment

Welding is one of the methods of joining parts of a metal part into one element.

There are several methods of metal processing, among which is the gas type of metal welding.

This article will discuss in detail the application of this type of welding, its pros and cons, as well as the materials that will be needed for the work.

general information

In the gas method of metal processing, gaseous substances are used to create high temperatures. Welding is often done with oxygen, argon or acetylene.

Welding work is carried out using fire. It is combustion that creates high temperatures that can melt metal.

There are three zones in a gas flame:

• Core
• Recovery zone
• Torch.

The flame itself is classified into three types:

• Normal - different components of the mixture are supplied in equal proportions. Externally, it is determined by the color in blue tones with a brighter shade of the middle zone.
• Carburizing – reduced oxygen supply. The torch zone becomes bright yellow.
• Oxidative – reduced supply of acetylene. The saturation of the flame tone becomes pale, the length of the tongues shortens.

The mixture supply ratio is adjusted by determining the color of the tongue. In accordance with the type of flame, the temperature at which the metal will be processed changes.

Often the temperature norm exceeds 3000°C. This indicator is suitable for different types of metals.

A typical mode of gas welding using gas is working with a normal type of flame when supplying oxygen and acetylene in equal proportions. If the color changes and switches to another type of flame, the supply is reconfigured.

Application

Welding with gas occurs both with and without the use of a welding rod. In the first case, the seam is created by connecting the edges of the parts with the molten metal of the rod, in the second - by welding the edges of the parts themselves.

However, this type of welding is not suitable for every type of metal. It should be used for processing sheet metal, thin-walled steel parts (up to five millimeters), non-ferrous metals, cast iron or tool steel.

Working with these types of metal is characterized by smooth, soft heating of the surface.

The scope of application of gas processing of metal is quite wide. This type of welding can be used both on an industrial scale and for domestic work.

Smooth heating of the surface protects against deformation, which is important for welding thin-walled parts. The key point is the correct setting of the supply of the working mixture and the correct type of fire.

Ignition occurs using a match or lighter, with a full supply of the working mixture. The flame type is adjusted by the acetylene supply level.

Types of gases for welding

Gas welding is often carried out using acetylene. Its creation occurs through the reaction of calcium carbide and water, the chemical formula of the final result is C2H2.

It has a sharp, characteristic odor. The combustion temperature of pure acetylene is 335°C, when mixed with oxygen it is 227°C.

Gas-press type welding is carried out by mixing acetylene with oxygen in a 1:1 combination. The color marking of oxygen cylinders is blue. The cylinder is connected to the device using a hose.

Supply occurs at a pressure not exceeding four atmospheres. The acetylene supply is connected through the second hose.

The welding torch is equipped with a special mechanism, thanks to which acetylene and oxygen are mixed into the working substance.

If necessary, acetylene can be replaced with other substances, but the characteristics of the substitute and their relationship with the characteristics of acetylene should be taken into account.

Required gas to oxygen ratio for each type:

• Propane - 1:0.6.
• Methane - 1:1.6.
• Hydrogen - 1:5.2.
• Kerosene vapors - 1:1.

It is worth remembering that when using methane or propane processing of steel parts, electrodes with a high content of manganese and silicon are used.

The exposure temperature, which exceeds the melting level of the metal, increases the melting index. This makes the seam of better quality, but you should not increase the temperature too much. Double concentration is enough.

Advantages and disadvantages

The welding process using gas welding is not complicated. However, there are pros and cons to using this method.

The most suitable metals for this treatment are copper, brass and cast iron.

The high combustion temperature allows you to work with metals that have different melting rates. This is also facilitated by smooth heating, which protects thin-walled elements from deformation and burning.

Equipment for gas welding is self-sufficient. For its operation, a power supply with a socket outlet is sufficient. Therefore, welding operations can be carried out in an unlimited space.

A correctly selected electrode and type of fire creates smooth, high-quality connections. This facilitates applications in the machining of pipeline parts.

The disadvantages of using gas welding include the increased danger of work. The working mixture is highly flammable and explosive and requires careful handling.

During processing, not only the welding zone warms up, but also the surface next to it. This can lead to deformation, which makes it impossible to work with metals thicker than five millimeters. For the same reason, gas devices do not make overlap connections.

Methods and technology of gas type welding

Technical and technological compliance with the work is an important part of gas welding. Obtaining a reliable, even seam directly depends on how the metal was processed.

As with other types of welding work, the task begins with a preparatory phase. It includes cleaning the treatment area from dirt, excess inclusions, and unevenness.

This is done with sandpaper, a file, a wire brush or a sander. Next, the processing technology is selected.

There are two opposing methods:

1. The burner moves from left to right - first the flame is exposed, then the connection with the filler rod is made.
2. The burner moves from right to left - first a rod is applied, then a flame connecting the edges of the seam.

The second method is used more often. It is characterized by better heating of the seam. However, with the first method, less working mixture is consumed, and the useful coefficient is twenty percent higher.

Electrodes are selected according to the thickness of the part to be processed. Each gas welding method has its own formula for calculating the diameter of the rod.

For the left method – d=S/2+1, for the right – dS/2. S is an indicator of the thickness of the metal of the part. It is measured in millimeters.

The gas welding method depends on the thickness of the part, its position and the width of the required seam. The type of mixture used also matters. An experienced worker can set the settings at his own discretion.

Adviсe

When studying the essence and processes of gas welding with gas welding machines, you need to remember that this type of metal processing is carried out using highly flammable, explosive substances.

This requires the worker to be careful. He must be attentive to detail during welding operations, before and after them. Do not allow shocks, impacts of cylinders, or leave switched on equipment unattended.

A welder at the beginning of learning how to work with gas-powered machines should consider a couple of tips:

1. Carry out training work with oxygen and acetylene.
2. The GZUZ-02 torch is suitable for propane welding. Filler rods model Sv08g2s.
3. Don't ignore the preparatory stage.
4. Gas pressing processing requires reliable fastening of the part. Use a press or other hydraulics.

The choice of left-handed or right-handed gas welding method depends on the part and the preference of the welder.

Conclusion

For gas welding, flammable gases are used. Most often it is acetylene and oxygen. Acetylene has substitutes (methane, hydrogen and others).

The type of flame depends on the proportions in the working mixture. It is better for more experienced welders to work with propane. Beginners should use a mixture of oxygen and acetylene.

The preparatory stage of gas welding can play a key role in the quality and reliability of the connection.

Source: https://prosvarku.info/tehnika-svarki/gazovaya-svarka

Features of gas welding

There are different ways to connect metal parts. The most effective technology is heat treatment, which includes several methods. One of the most popular is gas welding.

Gas welding of metal pipe

The essence of the process

The essence of the gas welding method is that a hot gas stream is supplied through a special nozzle to the working surfaces. It heats the edges of parts to critical temperatures, melts the filler material, which is fixed to the nozzle or supplied to the heating site from the other side.

Gas displaces air from the heating site. Therefore, no oxide film is formed. Gradually the metal cools, the parts come together. Before carrying out work, you need to learn how to choose gases for welding:

1. The most popular mixture is oxygen with acetylene.
2. Propane with oxygen.
3. Hydrogen with oxygen.
4. Methane with oxygen.

To weld metal parts, you can use any flammable gas with the addition of oxygen. However, the best option is acetylene. This is due to the operating temperature that this gas can provide - up to 3400 degrees Celsius. For propane, this figure reaches 2800 degrees.

Advantages and disadvantages

Any technological process for joining metals has a number of strengths and weaknesses. A special feature of welding is that the welding gas slowly heats the working area. This cannot be called a clear plus or minus.

Advantages:

1. Smooth, uniform heating, which is needed for melting non-ferrous metals.
2. No powerful source of electricity is needed.
3. Ability to control the power of the hot jet.
4. Availability of additional controllers for switching operating modes.

Flaws:

1. Low efficiency due to large heat dissipation when heating metal with gas.
2. Large heating zone. It is impossible to carry out precise work.
3. The gas consumed is more expensive than the electricity consumed to carry out the same work.
4. Cylinders, cutters, connecting hoses are not convenient to transport.
5. It takes practice several times to learn how to make quality seams.

Most cutters are manual equipment that cannot be automated. Difficulties in automating the process can be considered a disadvantage.

Gas welding of metals has a number of nuances that relate to working with different materials:

1. Any gas can be used to join low-carbon steel parts. Additionally, it is important to use a filler material (steel wire) that contains a small amount of carbon.
2. To cook cast iron, you need to use a carburizing flame. It eliminates the formation of brittle particles of white cast iron, which negatively affect the strength and hardness of the material.
3. Before cooking alloy steels, you need to understand their composition. If these are heat-resistant materials, filler wire must be used. It must contain nickel and chromium. Some grades of alloy steels require the use of filler materials with molybdenum.
4. To connect copper parts, you need to use a high-power flame. It is important to consider that copper has a high fluidity rate. Because of this, it is necessary to set a minimum gap between the workpieces. Additionally, protective flux and copper wire are used as filler material.
5. Bronze workpieces must be welded using a reducing flame mode. It is important to use filler materials of similar composition.
6. When working with brass workpieces, it is important to add more oxygen to the combustion gas. This way you can avoid volatilization of tin from the material composition.

It is important to consider the composition of the materials being welded in order to make a high-quality seam.

Gas welding of copper pipe

Application area

To understand where the technology of thermal joining of metals is used, you need to understand what materials can be welded using this method:

1. Thin sheets of steel, tin (up to 5 mm).
2. Cast iron.
3. Non-ferrous metals.
4. Tool steel.

Technology and methods of gas welding

Before starting welding work, it is necessary to prepare the working surfaces. They are cleaned of rust, dirt, and plaque. Next, the master needs to choose a gas welding technology. Each of the individual methods has certain execution features. Gas welding methods:

1. Left way. Used when working with non-ferrous metals and low-melting alloys. The nozzle should move from right to left.
2. Right way. Used for low-melting metals. The filler wire must be moved following the flame.
3. Through roller. Initially, it is necessary to secure the sheets of metal vertically to the gap. Use a torch to melt the edges. Once you have a hole, melt it on all sides to create a seam.
4. Multilayer welding. To make a high-quality seam, you will need to spend a large amount of gas.
5. Connection by baths. This method is used to secure corners or join joints of metal sheets. It is important that the thickness of the workpieces does not exceed 3 mm.

It is important to be responsible when choosing a working mixture. It can be a mixture of oxygen with:

1. Methane.
2. Propane.
3. Acetylene.
4. Hydrogen.

To weld metal sheets with a thickness of more than 5 mm, you must use a double roller. The burner is fired in the right way.

Equipment

Types of equipment for gas welding:

1. Gasoline-oxygen.
2. Acetylene-oxygen.
3. Kerosene-oxygen.
4. Propane-oxygen.

Other key elements of a gas welding machine include:

1. Safety lock. This part ensures safety during operation.
2. Gas cylinders. According to GOST, they must be painted a certain color, depending on what is inside.
3. Valve installed on the cylinder. Must be made of brass.
4. The gearbox is a key element of the equipment. Provides reliable connection of the burner to the cylinder.
5. Burner for supplying the working mixture. There are two types - acetylene, propane. It is a working part of the equipment on which valves are located to regulate the supply of gases. They are mixed using a system of tubes that are located on the burner.

At the outlet of the cutter there is a nozzle through which the finished mixture is supplied to the working surface.

Pipe welding stages

After selecting a gas for welding, the welder must prepare the equipment and check the functionality of individual elements. Next, the work begins. The gas welding technique consists of several stages that must proceed sequentially:

1. Preparation of working surfaces. They are marked and cleaned of plaque, dirt, and rust.
2. To begin connecting individual metal elements, you need to grab them with a welding machine.
3. Align the workpieces relative to each other. Additionally, check the accuracy. Start uniform heating of the working part of the equipment. After heating the metal until it begins to melt, the cutter must be slowly moved along the boundaries of the future weld and filler material must be fed into the working area.

Using a cutter, you can separate metal workpieces into parts.

Cleaning a metal surface

Safety precautions

Before you start working, it is important to study the safety rules and adhere to them:

1. Do not use the equipment near flammable substances or liquids.
2. Work only in a well-ventilated area. If the building is not ventilated, take breaks during work so that the welder can get some fresh air. It is advisable to use a respirator.
3. It is important to check that the equipment elements are not stained with oil.
4. To cool the nozzle, there should be a container with cold water nearby.
5. Prepare the work area before welding begins. Interference during operation can lead to injuries and defective workpieces.
6. Use safety glasses, a special welding suit, and gloves.

Before starting work, check how securely the connecting hoses are connected. There should be no gas leak.

Gas welding is a popular method of thermal joining of metal parts.
Before starting welding work, you need to familiarize yourself with the features of the technological process, prepare the equipment and parts to be welded. In order not to harm the body, it is important to follow safety rules. Gas welding first steps - Welding territory
Gas welding for beginners (lower position of the seam)

Features of gas welding Link to main publication

Source: https://metalloy.ru/obrabotka/svarka/gazovaya

What is gas welding: work technology, equipment, types of cutters and safety precautions

Gas welding is a work in which, using high temperature, the product is heated and melted to a soft state. This type of welding is often used for structures made of thin carbon steel, for repairing cast iron products, as well as for welding damaged parts made of ferrous or non-ferrous metals.

Gases that burn well in air and do not reach high temperatures: acetylene; methane; propane; hydrogen; gasoline vapors.

To burn them, you need an oxygen stream. Welding is most often done using acetylene , which is produced by the reaction of calcium carbide and water. Combustion occurs at temperatures from 3200 to 3400 degrees Celsius.

The valuable qualities of gas welding include the following:

• availability;
• unnecessary availability of electricity;
• simplicity of welding equipment.

However, the process of such work cannot be called highly productive, since everything is done manually. And the operational and mechanical properties of the finished product do not always correspond to high quality.

When the welding machine is operating, oxygen is supplied from a special oxygen cylinder, which, according to GOST, is painted blue or dark blue. To ensure a continuous process, oxygen must be supplied to the burner at low pressure, evenly .

For such purposes, cylinders are equipped with reducers that control and regulate the oxygen supply. Hoses are supplied to the burner - oxygen and acetylene . Oxygen is supplied through the central channel: the jet discharges, sucks in acetylene, which enters the burner under low pressure. In the chamber, the gases are mixed and exit the tip to the outside.

Necessary equipment

Devices used for gas welding: acetylene-oxygen; propane-oxygen; gasoline-oxygen; kerosene-oxygen.

The ones most used for welding are propane and oxygen-acetylene machines , since they emit the highest temperatures when burning.

More commonly used are acetylene generators, which release acetylene when water and calcium carbide are mixed. This type of generator exists in five types, so it’s easy to choose the right option for a specific metal.

Safety valves play an important role . They provide safety and prevent the backlash of fire that occurs during welding. The valves also block the reverse flow of gas through rubber hoses.

A cylinder is a cylindrical container with a hole and a thread in the neck for screwing in a shut-off valve. Made from carbon or alloy steel. According to GOST, it is painted with a special color of paint, depending on the gas.

Valves for gas cylinders are made of brass (since steel is not resistant to corrosion), always with a left-hand thread, smaller in diameter compared to the valve of an oxygen cylinder (so that there is no possibility of mixing up the gearboxes).

Types of gearboxes

1. A gas reducer is a device for controlling gas pressure. For gas welding and cutting you will need different types of gearboxes.
2. Oxygen is used in metal welding and gas welding. It has a blue marking on it. Can be used in aggressive environments as it is not afraid of corrosion.
3. Acetylene reducers are attached to the cylinder with a snap-on clamp and are marked in white.

   This type of gearbox comes with two pressure gauges: one monitors the gas pressure in the cylinder, the second monitors the pressure in the working chamber.

4. Carbon dioxide reducers are widely used in the chemical and food industries. They are equipped with one or two pressure gauges and are connected to a vertical pressure gauge.
5. In argon arc welding, argon gearboxes are used that work with non-flammable gases.

6. Gas burners are used in all kinds of industries. All burners are similar in design. Each consists of a housing to which several parts are attached: a valve that controls the gas supply; lever controlling the height of the fire; tip.

Using a reducer, the connection to the cylinder is made.

The burner can be equipped with piezo ignition and wind protection .

The burner is safe when working with propane. Maintains a high fire temperature, which is sufficient for a large number of welding jobs. Some types of welding are carried out with acetylene torches using a mixture of oxygen and acetylene.

Gas cutters

The following types of gas cutters are distinguished:

• propane;
• acetylene

The product consists of a handle, a body, nipples (gas hoses are attached to them), an injector, a tube, a mixing chamber, a gas cutter head, a tube with a valve. Metal welding and its quality depend on how correctly the cutter was selected.

Principle: oxygen is supplied to the reducer, then into the hose and into the housing - the cutter is branched into two channels. One part of the oxygen moves through the valve into the injector. Gas comes out at great speed, while at the same time flammable gas is sucked in.

Combining with oxygen, a flammable mixture is formed , which moves between the mouthpieces and burns. A heating fire appears. Oxygen moving through the second channel passes into the tube, causing a cutting jet to appear. It is she who processes the area of ​​the material.

The metal is prepared, stripped, marked, pipes are cut and assembled. Cutting the round pipe section should be done with a thermal cutter.

Preparation takes most of the work. This includes measurements, markings, cutting and much more. The structure is assembled using gas tack welding , this will prevent displacement and deformation of pipe sections, which can affect the appearance of cracks.

As a result of unhurried heating, the impact zone during gas welding is larger than during arc welding. The layers of the base material directly adjacent to the weld pool are permanent and have a coarse-grained structure.

Very close to the weld boundary there is a zone of incomplete melting of the metal with a large structure typical of an unheated material. In this zone, the strength is lower than that of the weld metal, which is why the destruction of the welding joint occurs here.

Cutting is carried out using metals and alloys that can burn in a stream of pure oxygen. This type of cutting is done in two ways: superficial and dividing . You can cut out blanks, mark metal, and cut the edge of a future seam for welding.

Using surface cutting, surface metal is removed, grooves are filled, and defects are removed. This type of work is performed with special cutters

What you need to know about gas welding

Gas welding is the joining of metal parts by melting. Historically, this is one of the first types of welding to appear. The technology was developed at the end of the 19th century.

Subsequently, with the development of electric welding technologies (arc and resistance), the practical value of gas welding decreased somewhat, especially for joining high-strength steels. But it is still successfully used for joining cast iron, brass, bronze parts, for fusing techniques and in many other cases.

Essence of the process

The essence of the method is that a high-temperature welding gas flame heats the edges of the parts being welded and part of the filler material (electrode part).

The metal goes into a liquid state, forming a so-called weld pool - an area protected by a flame and a gaseous environment that displaces air. The molten metal slowly cools and solidifies. This is how the weld seam is formed.

A mixture of some flammable gas with pure oxygen, which plays the role of an oxidizing agent, is used. The highest temperature - from 3200 to 3400 degrees - is produced by acetylene gas, obtained directly during welding from the chemical reaction of calcium carbide with ordinary water. In second place is propane - its combustion temperature can reach 2800 °C.

Less commonly used:

• methane;
• hydrogen;
• kerosene vapor;
• bluegas.

All alternative gases and vapors have a flame temperature significantly lower than that of acetylene, so welding with alternative gases is practiced less frequently, and only for non-ferrous metals - copper, brass, bronze and others, with a low melting point.

Gas welding has features compared to electric welding, which form both its disadvantages and advantages.

Standards

GOST for gas welding is a special issue. Due to the fact that the quality of a weld in gas welding largely depends on the skill of the welder, it is determined subjectively.

The nature of the gas welding process is exclusively manual; there is no specific GOST for gas welding . But there is GOST 1460-2013 - for calcium carbide, from which gas for welding is produced.

In addition, various GOSTs define parameters such as types of filler wire, pressure in the gearbox and cylinder, and requirements for the acetylene generator. There are specific requirements for the types of hoses and burners used, related to operational safety.

Standard equipment set

Gas welding or cutting (a technologically simpler process) requires equipment. First of all, this is an acetylene generator or a source of other flammable gas (propane, hydrogen, methane). You will also need a cylinder with an oxidizer - oxygen, a burner, a compressed gas reducer (flow regulator) and connecting hoses.

Various auxiliary devices can be used, for example, a piezo ignition element, a safety water seal for protection against backfire (lately an almost mandatory element), and others.

A distinctive feature of this type of welding is that it does not require power supply, so work can be carried out practically in “field” conditions. Largely because of this advantage, gas welding is still actively used.

Types of flame

One of the advantages of gas welding is the ability to use fire with different chemical properties: oxidizing, reducing, with a high acetylene content.

A “normal” flame is considered to be a reducing flame, in which the metal is oxidized at the same rate as it is reduced. It is used in most cases. To join parts made of bronze and other alloys containing tin, only reducing fire is used.

An oxidizing flame is formed when the amount of oxygen in the gas mixture increases. In some cases it is preferable and even necessary, such as when joining brass and brazing.

A special property of the oxidizing flame is the ability to increase the speed of gas welding. But in this case it is necessary to use a special additive containing deoxidizing agents - manganese and silicon.

If you use the same material as a filler wire with an oxidizing flame as in the parts being welded (with the exception of brass), the weld will come out brittle, with a large number of pores and cavities.

A flame with an increased content of flammable gas is used for surfacing another part made of a harder alloy onto any part, as well as when welding parts made of cast iron and aluminum.

Technology and methods

The gas welding technique greatly depends on the specifics of the metals and alloys being welded, the shape of the parts, the direction of the seam and other factors.

The main purpose of gas welding is the processing of cast iron and non-ferrous metals, which lend themselves to it better than arc welding. It “takes” alloy steel worst of all - due to the low heat transfer coefficient, parts made from it warp greatly when cooked with gas.

There are “right” and “left” gas welding techniques. There are also technologies for welding with beads, baths and multi-layer welding.

The “right” method is when the welding nozzle is moved from left to right, and the additive is supplied following the movement of the fiery jet. The flame is directed at the end of the wire, so that the molten composition - the melting point of the additive is usually lower than that of the base material - lies evenly in the seam.

With the “left” method of gas welding - it is considered the main one - they do the opposite. The burner moves from right to left, the additive is fed towards it. This method is simpler, but is only suitable for thin sheets of metal. In addition, with it there is more consumption of filler wire and combustible gas than with the “right” one.

Roller welding is a more labor-intensive method, suitable only for sheet material. The seam is formed in the form of a roller, but the quality of the seam is very high, without the formation of slag, pores and air gaps.

Pool welding is a method that requires great skill from the welder. In this case, the filler wire is laid into the seam in a spiral manner, passing through different sections of the flame. Each new turn of the spiral slightly overlaps the previous one. The method is well suited for joining sheets of low-carbon steel.

Multilayer welding is the most technologically complex method. Its basics are like surfacing one layer on top of the next. In this case, ideal heating of all underlying layers is achieved. The main thing is to control that the joints of the seams of different layers are not located one under the other.

In each of these types of gas welding, different fluxes can be used, depending on the metal being processed. Their task is to protect the surface of the seam from the formation of oxides that impair its quality.

Source: https://svaring.com/welding/vidy/gazovaja-svarka

Gas welding and metal cutting

Gas welding is widely used in joining products made of cast iron alloys, repairing materials consisting of thin carbon steel, and welding casting defects in non-ferrous or ferrous metals. The process occurs by igniting the material with a high-temperature flame, which is formed by burning pure oxygen and a combustible mixture. Filler wire is used to set the edge gap with molten metal.

Gas welding

Features of gas welding

During the work process, it is possible to regulate the composition of the mixture, which the gearbox helps with. The flame power and temperature are adjusted depending on the type of work. There are several types of gas welding:

• Oxidative.
• Restorative, which is used for most compounds and materials.
• With an increased level of combustible mixture.

In the molten pool during welding processes, two main processes occur, reduction and oxidation. The structure of the adjacent metal is mainly coarse-grained, for a more durable connection.

For improved strength indicators, heating is performed to maximum temperatures, a kind of forging of the metal.

Several main features when working with gas equipment:

• Gas welding of low-carbon steel materials is carried out using various types of gas, the filler element consists of steel wire, with a small amount of carbon content.
• Alloy steels are welded with materials that react with the composition. For example, heat-resistant stainless steel parts are welded using nickel wire; some grades of material will require the use of molybdenum.
• Copper products are welded at elevated temperatures; the high fluidity of the metal will require minimal joint clearance. The filler material consists of copper wire and flux, which is used to deoxidize the weld.
• Brass connections are made by using an additive of identical material. Due to the volatility of zinc, more oxygen is supplied during welding to avoid the formation of pores.
• Bronze alloys are welded using a reduction flame without burning out the main components of the metal. For the additive, an identical material is used using silicon, which promotes deoxidation of the weld and metal.

Gas pipe welding

It is worth noting that when working with aluminum or magnesium, oxidation processes proceed faster. The processing area and the seam have different parameters and characteristics; the adjacent area located in close proximity is characterized by reduced strength and is prone to premature deformation.

Operating principle of gas welding

Oxygen and flammable gas are supplied to the device through pipes, ignition occurs through the nozzle, and the flame power is adjusted by valves. The flame consists of several main parts, the torch, the recovery process and the core. The highest temperature parameters are observed in the core; the process occurs as part of the flame between the core and reduction.

The impact of high temperatures on the surfaces of materials entails protection of the welding area from excess air, which contains impurities of heavy gases. High performance when cutting metals allows you to perform work with high precision and produce the necessary products. There are different types of gas welding.

Welding equipment

Welding gas plays a big role in the density and quality of the joint; the popular gas used is acetylene.

Gas welding technology

Gas welding technology uses an additive made of light alloy material, the main task of which is to fill the edges of materials. An acetylene torch is used to melt the edges by heating, after which the joint is made. The second method involves surfacing or spraying, depending on the type of metal and equipment. The difference between the methods is in the consumption of the gas mixture, the materials being processed, and the time spent on the operation.

Pollination of two metal compounds will require high temperatures, this will require an increased amount of combustible mixture. Heating the filler rods does not require high temperatures; the structure of the tool consists of low-melting materials. There is a special type of electrodes for connecting materials with inverter type equipment.

The gas welding technique using various additives is much stronger, more pleasant in appearance, the process is faster, and the consumption of the combustible mixture is several times lower.

Welding wire

This technology of welding work is used in various fields, connecting technological pipelines, spare parts of machines, welding rods, forging various fragments.

The gas welding process will require the following basic elements:

• In most cases, propane is used as gas. Various types of gas with inert fluidity are suitable.
• The catalyst for ignition is a cylinder of oxygen gas.
• Hoses for removing the gas mixture, nozzle, reducer on the cylinder and handle.

The calibration nozzle sprays the gas mixture under pressure, a silicon piezo lighter is used to ignite, after which the saturation of the mixture and the strength of the flame are adjusted.

Pros and cons of gas welding

Each type of work performed implies the presence of certain advantages and disadvantages. A welding connection is possible using various equipment and tools and depends on the properties of the material. The advantages and disadvantages of gas welding are determined by several points.

Main advantages:

• One of the most important advantages of gas welding is the availability of equipment and the lack of energy requirements. Welding work can be performed with two cylinders and a cutter. An excellent solution for remote locations without electricity.
• The connection of thin sheet metals is carried out very carefully, with high quality due to the possible adjustment of the flame distance and temperature conditions.
• Transportation does not require large expenses; there is no need to purchase special equipment for moving and storing.
• A reliable seam and high-quality work allow you not to worry about the durability of welding joints.

Weld

Disadvantages of gas welding:

• Welding products with high precision requires a highly qualified operator; products are produced slowly.
• Large circumferential range, high temperature.
• Increased consumption of components, welding gas and wires is required.

Materials for welding using gas

The technological process using gas materials depends on a number of reasons and factors. The main and unchangeable gas is oxygen in its technologically pure form.

The purpose is to activate the combustion processes of metal parts for connection at a later time. The gas is transported and kept under high pressure for long-term operation outside the gas station.

Storage and contact with technical oils is unacceptable, and it is also not recommended to use oxygen in direct sunlight.

Pure oxygen is obtained from ordinary air; special devices are used for purification. Oxygen is divided into categories: highest, first and second grade. Working with materials is impossible without the accompanying oxygen gas. In most cases, colorless acetylene is used. Acetylene is produced by combining water with calcium carbide and is explosive at certain temperatures.

Acetylene for welding

The use of acetylene is determined by high temperatures when welding joints; cheaper analogues do not make it possible to produce high-quality work due to insufficient combustion temperature.

Wire and flux for welding

The wire is used for gas welding and is necessary to replenish the cells of released compounds. The use of flux and wire makes it possible to create a correctly formed seam with the necessary characteristics.

Cleanliness and absence of signs of corrosion on the wire material makes it possible to produce a high-quality product; in some cases it is possible to use a piece of the same material that is being welded.

Flux provides protection from oxides and other influences surrounding the installed metal.

Welding flux

Neglecting the use of flux for welding is possible only when producing materials from carbon steel. Boric acid, used as a flux, is applied to parts made of copper, magnesium or aluminum.

Gas welding equipment

In addition to the gases and cylinders used, it is necessary to have other technological elements:

1. For gas welding, equipment is used, such as a water-type shutter, which provides protection against the backdraft of fire. The location occurs between a container with acetylene and a gas nozzle.
2. Reducers are used to control the gas level at the outlet of the cylinder. There are various models, reverse or direct acting. Modifications for working with liquefied gas imply the presence of scars inside the structure, which eliminates freezing.
3. A special type of hose is used to supply gas to the burner. Marking occurs in different colors depending on the maximum pressure.
4. The burner is necessary to mix the combustible mixture and subsequently ignite the gases. Various modifications are divided into injection and conventional types. The division also occurs according to the power required during operation.
5. Gas welding is performed on a equipped table. Equipped with a tabletop for convenient, productive work. The gas welding and cutting machine must comply with safety parameters. Exhaust ventilation helps the welder and allows processes to be carried out at maximum speed.

Gas-burner

Gas welding equipment includes a huge range of instruments and mechanisms. Taken together, the equipment allows work to be carried out at a location remote from energy sources. Each type of equipment is equipped for the type of gas used, with proper adherence to safety precautions.

How gas welding is performed in semi-automatic mode

Semi-automatic gas welding involves a hybrid method of joining metals. Applied using shielding gas and an electric arc, the process proceeds as follows:

• Starting mechanisms, preparing tools for work.
• A wire is threaded into a special hole in close proximity to the burner.
• The gearbox controls and sets the level of the combustible mixture.
• The wire feed speed is controlled by a special mechanism on the drum.
• The voltage and other parameters are set semi-automatically.
• Before starting the process, it is necessary to set the burner at the correct angle.

For a high-quality connection and uniform formation of a seam, when using this type of welding, parameters have been developed in accordance with GOST.

The pressure of the reducer must be at certain values, the type and parameters of the hoses. Cylinders containing gas must be pressurized and tested; burners and wire differ in parameters and must comply with established procedures. The check must be carried out before welding metals.

Precautions and rules for using a gas burner

The welding process can harm both the worker and others if basic safety rules are not followed. It is prohibited to carry out gas welding work in a confined space, or it must be equipped with good ventilation. Safety glasses prevent the influence of rays on the retina of the eyes, as well as metal splashes.

The welding station must be kept clean, the cylinders must be well secured in place and tested by pressure testing. Gas cylinders are transported on a specialized stretcher or trolley. During transportation, the operator must install a protective device on the top of the container. The work is carried out with a flame emanating in the other direction from the cylinders. If space is limited, a protective metal shield is installed and the temperature is controlled.

Source: https://stankiexpert.ru/spravochnik/svarka/gazovaya-svarka-rezka.html

Gas welding and metal cutting. Gas welding technology. Gas welding equipment:

Gas welding is a type of welding work where parts need to be heated to a molten state using a high-temperature flame. This method is widely used when creating structures based on thin carbon steel, when repairing cast iron products, as well as when it is necessary to weld defects in various products produced by casting from non-ferrous or ferrous metals.

What gases are used?

Gas welding uses flammable gases - natural, acetylene, gasoline vapor, hydrogen. These gases burn well in air without developing a high temperature; an oxygen stream is sufficient for combustion. Gas welding is most often carried out on the basis of acetylene, which is created on the basis of water and calcium carbide. It burns at a temperature of 3200-3400 degrees.

What are the features?

The advantages of gas welding include the following:

1. Simple technology.
2. No need for a welding power source.
3. Simplicity of the equipment on which gas welding is performed.

On the other hand, this process is not very productive. Welding is performed only by hand, and the mechanical and operational properties of the finished products are not always of high quality.

Oxygen reducer

When welding, oxygen comes from a special cylinder - it is painted blue or blue. To ensure normal operation, oxygen must enter the burner evenly and at low pressure. It is for these purposes that there is a reducer on the cylinders - it regulates the gas supply.

In this case, hoses for gas welding - acetylene and oxygen - are supplied to the torch. Oxygen is supplied to the central channel, where the jet is more discharged, sucking in acetylene, which enters the burner under low pressure.

The gases are mixed in the chamber and then released out of the tip.

Features of the technology

When performing gas welding, it is important to obtain a high-quality connection, so much attention is paid to careful preparation of the edges to be welded, choosing a method for joining the metal, installing the torch in the desired position and determining the required burner power parameters.

Gas welding technology requires that the edges must be thoroughly cleaned of various contaminants. The bevel is performed using a manual or pneumatic chisel, and sometimes special machines are used. Scale and slag can be removed with a wire brush.

Tacking the edges prevents their position from changing during welding.

Welding methods

Gas welding can be carried out in several ways. The first is left-hand welding, which is the most common. It is used when working with thin and low-melting metals.

The torch moves from right to left, and the filler wire is driven in front of the flame, aimed at the unwelded area of ​​the seam. In right-hand welding, the torch is moved from left to right, and the filler wire moves behind the torch.

With this method, the heat of the flame is dissipated to a lesser extent, therefore the opening angle of the seam is not 90 degrees, but less - 60-70.

It is advisable to use right-hand welding to join metal whose thickness is from 3 mm and above, as well as metals with a high level of thermal conductivity. It is recommended to use filler wire whose diameter is equal to half the thickness of the metal being welded.

Gas welding technology also involves a process that is carried out with a through bead. In this case, the sheets are installed vertically to the gap - its size is equal to half the thickness of the sheet. Using a torch, melt the edges to create a round hole. It is then melted on all sides until the seam is welded. This method is good because the sheets being welded have a tight seam without pores or slag inclusions.

Pool welding is good for welding joints and corners of metals that have a maximum thickness of 3 mm. As soon as a pool is formed on the seam, the end of the filler wire is inserted into it, which melts slightly, then the end of the wire is moved to another section of the seam. The peculiarity of this approach is that the weld is of excellent quality, especially if thin sheets and pipes of steel (low-carbon and low-alloy) were welded.

Gas welding and cutting can be carried out on the basis of multilayer welding. This method has a number of features:

• heating zone is small;
• When surfacing subsequent layers, the underlying layers are simply annealed;
• each seam can be hammered before the next one is placed on it.

This affects the improvement of seam quality. On the other hand, this method is characterized by low productivity and requires high gas consumption compared to single-layer welding, so it is used when it is necessary to create responsible and high-quality products.

Features of welding various seams

To work with horizontal seams, the right-hand method is used, which makes it possible to easily form a seam, and the metal of the bathtub itself does not drain. Welding of vertical and inclined seams is carried out using the left method, and if the metal thickness is above 5 mm, a double roller is used. Welding ceiling seams involves heating the edges until they melt, then inserting a filler wire into the pool - its end quickly melts. The process itself is carried out in the right way.

What equipment?

Gas welding equipment for gas welding is a wide selection of devices that allow you to carry out a range of work. This type of welding is considered simple, and the equipment itself is quite concise and easy to use.

Depending on the type of fuel, gas welding devices are propane-oxygen or acetylene-oxygen, gasoline or kerosene-oxygen.

Most often, welding is performed on the basis of propane-oxygen and acetylene-oxygen welding, since the flame of these gases has the highest temperature.

Gas welding equipment for gas welding is also a generator, which is supplemented with different types of gas. Also, when working, you will need an oxygen cylinder and reducers. The most common are acetylene generators for gas welding, which make it possible to obtain acetylene directly by mixing calcium carbide and water. This type of generator is available in five types, which allows you to choose the best option for a particular material.

Safety valves play an important role when working with welding; their task is to ensure safety during welding. With their help, the backlash of the flame that occurs during welding is prevented. In addition, thanks to check valves, the reverse flow of gas into rubber hoses is prevented when flame processing of metals and when working with compressed gases.

Gas cylinders

Equipment for gas welding includes cylinders and valves for them. A cylinder is a cylindrical vessel that has a threaded hole in the neck into which a shut-off valve is screwed. It is created from alloy or carbon steel, and each such product has its own color depending on the gas it contains. Valves for cylinders are made of brass, since steel is not resistant to corrosion.

Gearboxes: types and features

A gas reducer is a device that constantly reduces or maintains gas pressure at a certain level. Gas welding and metal cutting are carried out using different types of gearboxes:

1. Oxygen is used in gas welding and metal welding. This gearbox is made with blue markings. Can be used in aggressive environments because it is made of corrosion-resistant metals.
2. Acetylene gearboxes are widely used in gas welding. They are marked in white and are attached to the cylinder with a snap-on clamp. This type of reducer has two pressure gauges, one of which controls the gas pressure in the cylinder, the second – the gas pressure in the working chamber.
3. Carbon dioxide reducers are widely used in industry - food, chemical. They have one or two pressure gauges and can only be connected to a vertical pressure gauge.

In argon arc welding, argon gearboxes are widely used, which can also work with non-flammable gases.

Features of gas burners

Gas welding of steels is a process that requires the use of a variety of devices. Gas burners are an integral element of equipment used in various industries. The design of the products is approximately the same: each burner consists of a housing.

Several elements are attached to it at once: a tip, a valve that regulates the fuel supply, and a lever that regulates the height of the flame.

The connection to the cylinder is made by a reducer, while the burner itself can often be supplemented with piezo ignition, flame wind protection and other components.

A propane-based gas torch for welding is safe to operate, providing a high flame temperature: it is sufficient to perform a range of jobs. Many types of welding are carried out using acetylene torches, which operate on a mixture of acetylene and oxygen.

Types of gas cutters

Gas cutters come in different types: acetylene, propane, and operating on gas substitutes or liquid fuel. The design of the products includes a handle, nipples to which gas hoses are attached, a body, an injector, a mixing chamber, a tube, a gas cutter head and a tube with a valve. Gas welding of metals and its quality depend on how well the cutter is selected.

The essence of its work is as follows: oxygen flows from the cylinder into the reducer, sleeve, and then enters the body - here the cutter branches into two channels. Some of the oxygen passes through the valve and is directed to the injector. From here the gas comes out at high speed, and during this process flammable gas is sucked in.

When combined with oxygen, it forms a flammable mixture, which is directed into the space between the mouthpieces and burns. As a result, a heating flame appears. Oxygen, which was directed through the second channel, exits into the tube, due to which a cutting jet is formed. It is he who processes the metal section.

Features of pipe welding

Welding of gas pipes is carried out in several stages. First, the metal is prepared, that is, markings are carried out, pipes are cut and assembled. Due to the round cross-section of the pipes, cutting is performed with a thermal cutter.

Most of the welding work involves assembling parts for it, when it is necessary to take into account many details - from the series of products to their diameter and other factors.

Assembly is performed using welding tacks, which prevent possible displacement of pipe sections, which affects the appearance of cracks during cooling.

The arc is lit. This is done in different ways. Then the melting of metals - base and electrode - begins. For a quality seam, it is important to pay attention to the angle of inclination of the electrode.

Gas cutting technology

Oxygen gas cutting is carried out using metals and their alloys, which burn in a stream of technically pure oxygen. This type of cutting is performed in two ways - separation or surface. The first method allows you to cut out workpieces, cut metal, and cut seam edges for welding. Using surface cutting, surface metal is removed, grooves are cut, and surface defects are removed. This procedure is performed using special cutters.