How to cook with gas welding

Gas welding

Scientific and technological progress does not stand still, and with the advent of compact inverter arc welding power supplies, life has become much simpler. It would seem that now you can forget about the good old gas welding! However, gas welding still enjoys great respect among welders, in particular in the gastrointestinal tract when laying pipes, as well as in workshops.

The thermal energy during gas welding, necessary for melting the metal, is obtained by burning fuel.
The following mixtures can be used: H2+O2; C2H2+02; gasoline + O2, etc. It is difficult not to notice the presence of oxygen in all the examples given; it is added to increase the temperature of the flame. In practice, of all of the above, C2H2 (oxygen-acetylene welding) or its cheap analog MAF is most often used.

Arc and gas welding in all physical manifestations are classified as fusion welding. But this is where the similarities end, and in essence, technologically, the two processes are very different. When gas welding, heating of the metal occurs slowly, at low speed. In certain cases this provides advantages, in others it completely complicates the welding process or makes it impossible.

Gas welding provides advantages when welding:

• Thin-walled metals from 0.2 to 5 mm; • Non-ferrous metals; • Steels requiring slow preheating and the same subsequent cooling;

• Cast iron, which becomes cracked due to temperature changes, and special steels.

It is also difficult to overestimate the quality and speed of work performed during hard soldering of corrosion-resistant steels, copper alloys and surfacing.

Gas welding is in demand for many repair and installation activities. But there are also negative sides. They are associated with low welding speed: slow heating slows down even more as the cross-section of the part increases. It is believed that when the thickness of a part is over 8-10 mm, gas welding is not economically feasible, although technologically the de jure possibility of welding thicknesses up to 40 mm remains.

Slow heating, among other things, can lead to unwanted metamorphoses in the metal. Overheating at the structural level manifests itself through grain enlargement, which reduces mechanical strength. Also, due to the rather large and long-term thermal effect on the product, another problem appears - its high warpage (when compared with MMA).

Therefore, the most simplified joints for welding are used, most often these are butt joints. T-bars, overlaps, corners, etc. connections are used extremely rarely, since they require intense heating, which is accompanied by extremely increased deformations.

There are no restrictions on the preparation of butt joints: flanging of edges, chamfering on one or both sides is used, and it is also possible to perform butt welding without mechanical preparation (sharp edges).

The gas burner is set to normal flame.
To obtain a normal flame, the ratio of O2 to combustible gas should be 1.1 -1.2 for C2H2. The flame is set so that the part falls under the action of the reduction zone (2-6 mm from the core). It is prohibited to touch the liquid metal of the weld pool with the core, as this causes the effect of carbon saturation.

With a change in the angle of inclination of the burner mouthpiece to the metal surface, the intensity of the thermal effect on the joint changes. The larger the angle, the more active the heating.

Accordingly, when welding non-ferrous metals, for example, copper, as well as when working with thick-walled products, the angle is increased. When working with thin sheets, the angle of inclination is reduced, and the thermal effect is reduced due to its dispersion over a larger area.

Gas welding is performed in all currently known positions. The most difficult of them is the ceiling, when moving metal needs to be held by the force of a flame.

In order to fill the gap or strengthen the seam, or, as it is also called, a rod or wire, is used The wire material should be close to the material of the part. Sometimes to improve fur. properties, niobium, tungsten, silicon, etc. are introduced into the additive. (see GOST 2246-70).

For welding ferrous metal with a low carbon level, St.-08 is used; St.-08A; St.-10GA and St.-15G. For cast iron - special rods (high carbon) with a large amount of Si. For wear-resistant surfacing, hard alloys obtained by casting are used.

Some features to consider:• Temp. the melting point of the wire should not be higher than that of the base metal; • Wire without visible contamination. The surface should be free of oil, traces of rust, pitting corrosion, and paint coatings;

• The nature of the melting of the rod is calm, without excessive splashing;

Protection

During the welding process, all metal parts are oxidized in the presence of O2. Oxide films have a temp. melting is an order of magnitude higher than that of ordinary metal, which creates difficulties. To protect the weld pool from the influence of the ambient air atmosphere and the dissolution of oxides, flux additives or pastes are used.

Pastes are usually viscous enough to be applied with a brush, but flux additives most often enter the weld zone at the tip of the rod. The additive destroys the oxide and becomes slagged. Fluxes are used for welding non-ferrous metals, high-alloy steels and cast iron. For gas welding of ferrous metal with low carbon content, fluxing is not used.

It should be noted that depending on the type of metal, two types of oxides are always formed: basic and acidic. Based on which one predominates, a flux additive is selected. The acidic oxide is removed with the main flux additive and vice versa. For example, when welding cast iron, the oxide with acidic properties SiO2 predominates, for the removal of which K20 and Na2O and borax are used.

When working with Cu and its alloys, the main oxides Cu2O, ZnO, etc. are obtained. They are effectively dissolved by acidic fluxes based on compounds with boron.

Where is gas welding in demand?

Gas welding is popular in many areas of production and human economic activity. For example, it is still relevant today in the construction of aircraft, especially where welding of black steels with a low carbon content with a thickness of 1-3 mm is required; Gas welding is used in the production of chemical units.

It is also popular in the public utilities sector; when carrying out repair and installation work (laying pipes of small diameter, up to 100 mm; repair of rolling stock in workshops, depots; agriculture, etc.). The quality of gas welding is higher than that of MMA welding with electrodes with a thin or stabilizing coating. Some electrode rods, strange as it may sound, are coated only with liquid glass consisting of potassium and sodium silicates.

Such electrodes are of the old type and are designed primitively, but are still actively burned by welders. However, gas welding is inferior to welding with high-quality (high-quality) electrodes coated with Fe alloys with Mn, Ti and Si. This is explained by the fact that a high-quality electrode acts not only as an additive, but also has an alloying effect on the weld pool. The strength of alloyed seams is much higher. Therefore fur.

the characteristics of seams obtained in gas protection, provided by the reduction zone of the gas torch, are inferior to the similar properties of seams obtained when working with a high-quality MMA electrode.

The high efficiency of gas welding drops sharply with increasing thickness of the product. With a thickness of 0.5-1.5 mm, gas welding can be more efficient than MMA.

However, this difference is actually leveled out when the thickness increases to 2-3 mm and further; with the addition of each millimeter of metal, the speed of MMA increases significantly. Also, when gas welding thin parts, gas consumption is small, but with an increase in wall thickness, its consumption increases significantly and the price tag for gas welding becomes higher than with MMA. Therefore, gas welding is advisable only when working with small thicknesses.

Gas welding torches

A torch is a tool that a gas welder cannot do without. It is constantly in his hands, so it should be as non-bulky as possible and fit comfortably in his hand.

The principle of operation of a gas burner is that the gases in it are mixed to a homogeneous composition, and the prepared mixture is ignited and produces the flame necessary to heat and transform the edges of the metal joint to be welded into a liquid state. The burner today performs non-trivial tasks:

• it must produce a high-temperature torch of a certain shape that is most effective for welding;
• precisely adjustable;
• the established operating mode must be maintained throughout the entire duration of the work;
• the burner must have high strength characteristics that ensure reliable operation and not require constant repairs;
• have little weight so as not to break the welder’s hands;
• equipment must comply with safety requirements, etc.

All these points can only be fulfilled if the burner has successful design features and is assembled from reliable, expensive materials that can withstand high temperatures, pressure, etc. These are mainly copper alloys and, in fact, Cu itself.

For the manufacture of the main part of the burner, an alloy of Cu with Zn (brass) is used; for the most heated part (mouthpiece), red copper is used, its temp. melting (about 1100 degrees) is sufficient so that the flame at the exit does not melt it.

  The temperature, of course, is not high, but the flame temperature at the base of the acetylene-oxygen torch does not exceed 700 °C and reaches 3200 °C only in the middle of the core.

There are different types of burners. There are even gasoline or kerosene that burn gasoline or kerosene in their bellies, but due to design differences, the most common burners are non-injector (high pressure) and injection (low pressure).

Injectorless burners

The principle that prevails here is: if the supplied gases have the same high pressure, then there is no need for additional injection (suction) of combustible gas. All you need to do is mix O2 and flammable gas in a special chamber until a homogeneous mixture is obtained - and everything is ready for welding activities. The burner has the simplest assembly.

It consists of hoses through which gas is supplied, a system of control wings, nipples, and a mixer. Injectorless burners are not very popular among craftsmen due to the fact that hydrogen and methane, the gases used in this technology, are not very in demand among the masses.

Acetylene is not used due to the fact that our production produces mainly low-pressure acetylene.

Injector burners

More complexly arranged. O2 enters the burner under high pressure of 4 atm. It creates a vacuum in the injector, the pressure drops below atmospheric pressure and thus flammable gas is sucked in.

Acetylene consumption increases as the mouthpiece warms up, and also due to the appearance of obstacles that complicate the exit of gases from the tip.

Therefore, during the work process, the welder is constantly forced to unscrew the acetylene wing on the torch, in other words, he constantly has to adjust the mode. At the same time, O2 consumption remains unchanged.

Source: http://svarka-master.ru/gazovaya-svarka/

Welding gas pipes with your own hands: how and what is done, methods, equipment and materials

The topic of pipe welding is very broad and complex. Mainly due to the fact that stores offer a large number of blanks. There are many types of pipes in diameter and material.

They can be wide, narrow, plastic, steel or alloys. Pipe material is only one of the parameters important for choosing a welding method and technique.

For gas supply, for example, pipes made of different steels are used. And in order to create a gas pipeline structure, you need to have experience and an understanding of the basic rules of the welding process.

Beginners will not be able to weld such pipes on their own; this is a task for experienced welders. If you have long mastered various methods of creating structures and several types of welding, you will be able to install a gas system in your home.

What techniques are needed in this case, and how to weld a gas pipeline yourself? We'll tell you in this article.

general information

Which technology to choose? Argon arc welding, inverter MIG/MAG and gas welding are suitable for gas pipes.

There are also production technologies that include large-scale automatic equipment and have high productivity on an industrial scale.

We are talking about home welding here, and we don’t need the features of conveyor production. The technologies that we listed before will just help you weld gas pipes in a residential area.

There is no ideal welding technique. Each of them can be viewed from both the “light” and “dark” sides. We will not recommend any of them by calling them “the best.”

It all depends on the thickness of the walls of your pipes, their diameter, and the type of steel from which the pipes are made. In some cases, work sites are difficult to reach, and this must also be taken into account when choosing a technology.

In any case, before soldering, free the edges of the pipes from paint, dust and rust. Afterwards you need to cut them if they are thicker than six millimeters.

The type of cutting is selected depending on where the pipe will be located in the structure.

The creation of a gas pipeline must be approached responsibly. If the seams oxidize, crack, or simply do not have sufficient sealing, a leak will occur on the first day of using the system.

This increases the risk of poisoning, fire or even explosion in the apartment. To avoid these consequences, you must first of all not skimp on consumables. But it is also important to study the welding method you need and its nuances.

Safety precautions

Welding work is dangerous, so read the safety rules before you begin. Processing gas systems is unsafe for the health of the welder, so the rules should not be neglected.

Rule #1. Do not open gas cylinders suddenly. They have built-in oxygen reducers, which easily ignite when gas is suddenly supplied. The cylinder is under high pressure, so any incorrect movement can cause it to explode.

Rule #2. Gas welding with a semi-automatic device is harmful to the respiratory system and eyes, so use a protective face mask and welding uniform during welding.

But the uniform, gloves and mask protect the master during any type of welding, so it is advisable to always use them.

Rule #3. There should be no tightly closed windows or turned off ventilation during welding! There should also be no materials (objects) that catch fire or could cause a fire on their own.

Rule #4. After you finish creating the structure, be sure to check each of the seams for defects and lack of fusion. If none of this exists, you can begin to use the gas pipeline for its intended purpose.

Argon arc welding

Argon arc welding (TIG) takes place in a gas environment. Its basis is a tungsten-coated electrode and an inert gas. Such electrode rods do not melt and do not take part in the formation of a connection between the elements.

They only accelerate the melting of the metal workpieces. The molten edges are connected to each other - this is the seam. Argon protects the welding zone from the influence of atmospheric gases (for example, oxygen) and prevents early oxidation.

TIG welding is good for welding pipes with thin walls. And to connect steel gas pipes, use direct current. The diameter of the rods you will need must match the cross-section of the pipe being welded.

MIG and MAG welding

The MIG/MAG method combines filler wire and a protective gas atmosphere.

The welder can feed the filler material into the weld pool manually, use a semi-automatic machine in which he controls only the feed rate, or use automatic equipment that controls the wire completely mechanized.

The first technology is the most economical option. Manual feeding of filler wire does not require expensive equipment with complex microcircuits and automation.

But this method is more difficult: manual application of the additive can be learned after months of practice.

Automatic equipment for MIG/MAG costs from five hundred dollars. This price did not come out of thin air. The machines handle most of the processes themselves.

The welder only lights the arc and leads it, creating a connection. Wire feeding and speed are fully automatic.

A semi-automatic welding machine is more versatile. It helps the welder deal with the additive, which makes the job easier. It costs less than an automatic one, but the quality of finished seams is not inferior to it.

In addition, the semi-automatic machine can be used for different steels: low-carbon, high-carbon, stainless steel and others.

The connection under such conditions is formed due to two factors: melting of the edges of the pipes and solder of the filler material. If you practice and learn how to use a semi-auto well, you will have a sealed gas design.

To do this, you also need to correctly install the supply from the gas cylinder. A gearbox will simplify the task. A little shielding gas is consumed, and no more should be consumed.

Source: https://prosvarku.info/tehnika-svarki/svarka-gazovyh-trub-svoimi-rukami

Gas pipe welding technology

Welding of gas pipes is carried out using various technologies: plasma, gas, argon, electric arc. Connections must be of high quality; novices are not allowed to install gas pipelines, only specialists with a personal stamp. The process is regulated by GOST 16037-80 and SNiP III-42-80. The choice of welding method depends on the alloy. Rolled steel and plastic are used for installation. Metal is traditionally used for domestic gas pipelines.

Welding methods

The installation technology depends on the pipe diameter and wall thickness:

1. Gas welding with acetylene or propane is used for pipes with a diameter of up to 150 mm and a wall of up to 6 mm. Joints up to 3 mm thick are welded without cutting; on the rest, the edges are pre-cut at an acute angle to form a strong joint.
2. Argon arc, MIG/MAG welding is used for steel gas pipelines.
3. Electric welding is carried out in small volumes, the number of penetrations depends on the thickness of the rolled product. For work, automatic, semi-automatic or manual welding equipment is used.
4. A semi-automatic machine usually makes the finishing layer, using fluxes or a protective atmosphere.
5. For intra-house wiring, electric welding is used in exceptional cases; gas equipment is usually used.

Each method has pros and cons. Much depends on the material being welded and access to the pipe in the areas being installed.

Electric arc welding

When welding gas pipes using electric welding, work begins with preparing the edges. They are leveled with a grinder at a right angle. Burrs are cleaned with a file. If the walls are thicker than 3 mm, the edges are cut at an angle of up to 60°. Rust and dirt are removed from the joints, then degreasing is carried out.

Before passing the seam, the parts are grabbed in several places with consumable electrodes in several passes:

• thin walls of 3 mm are boiled at a time;
• up to 6 mm – in two layers;
• more than 6 mm thick - three or more.

The rotary joint is passed completely in one step; special rotators are used for this work. If access is difficult, the seam is welded in fragments, filling the entire joint with molten metal. The finishing layer is made continuous, the joints of the welding joints are welded overlapping.

Electric arc welding is carried out in small volumes

MIG/MAG welding

Metal Inert/Active Gas technology provides for the creation of a protective atmosphere over the working area.

Welding of gas pipes using the MIG/MAG method is used for rolled carbon steels; it involves feeding filler wire and melting it under the influence of an electric arc. The protective atmosphere prevents oxidation of the melt.

In inverter semi-automatic machines, the filler wire acts as a conductive electrode. The gas supply is regulated by a reducer or flow meter. Welding methods:

• manual - the welder supplies the additive into the weld pool independently (the simplest and most cost-effective option for performing welding work);
• in semi-automatic mode, the additive is supplied through a gun at an adjustable speed (working with inverter equipment requires certain skills, the ability to control the seam);
• when using automatic machines, the filler wire feed speed is fixed (expensive equipment is used).

Source: https://svarkaprosto.ru/tehnologii/tehnologiya-svarki-gazovyh-trub

Gas metal welding technology: step-by-step instructions for effective technology for joining parts

Gas bonding or metal cutting was not possible until the Frenchman Devy realized in 1836 that acetylene (ethylene) based on calcium carbide could burn. Then they began to use it in street lamps and headlights of cars and steam locomotives. Much later, his fellow countrymen Fouche and Picard described a “welding pool” during gas-melting welding based on the same acetylene.

But it was in the Soviet Union that the industrial production of acetylene and its “packaging” in durable white steel cylinders was first started. This made it possible to increase the productivity of welders by 20 percent, without losing acetylene by the same amount. So gas welding of metals - steel, cast iron and non-ferrous - became available in any, even remote, area.

Gas welding - a universal solution

It is difficult to find an industry where gas welding is used - a method of firmly joining metals to each other in the melting stage with a flame of special temperatures. After all, acetylene burns at 3,200-3,400 degrees.

Gas welding technology is simple. This method can replace electric arc, but gas cannot. But still, the first one has priority on thin metals. The arc will simply melt them, as in open-hearth, and not hold them together.

How to "gas"?

Acetylene is still widely used today where small amounts of welding are needed, especially in emergency situations. Other flammable gases are also widely used: hydrogen and natural gas, propane (separately and mixed with butane) and petroleum, as well as gasoline and kerosene vapors.

But ethin is the king among them in terms of calorific value and thermal properties of the torch (this can be seen in the photo of gas welding) in its mixture with O2. And it is used more than other gases for these purposes.

Pros and cons of technology:

• no power supply required;
• inexpensive equipment and accessories;
• is carried out only manually;
• Not high quality of products in terms of mechanics and durability.

What is needed for gas welding/cutting

Gas welding equipment is simple and convenient to carry and transport. For any type of fuel, gas welding devices have an oxygen prefix. Because without it the process is practically impossible.

Main equipment for gas welding: cylinder or generator (gas holder), cutter. In the generator, calcium carbide produces acetylene (its formula is C2H2) mixed with water. They are mostly used by professional gas welders in their work, since this method is explosive. Therefore, in everyday life, at car service stations, in various workshops, and on sea vessels, only bottled acetylene is used.

Gas and oxygen cylinders. Oxygen does not burn, but it enhances combustion. When combined with various mineral or synthetic oils, including food grade ones, an explosion may occur.

Therefore, to service blue cylinders, almost medical sterility is required: clean gloves, well-washed or grease-free keys, gearboxes.

Each type of gas has its own valve and reducer so that there is no additional reaction with the metal. The valves for acetylene are steel, oxygen and propane/butane are brass. Reducers designed for a certain pressure are connected to them: acetylene - 2.5 MPa (5320 liters of gas in a cylinder), oxygen - 15 MPa (6000).

Porous material (charcoal) is poured into white cylinders and acetone is poured in, and only after that acetylene is pumped in. Another chemical reaction occurs inside and additional acetylene is produced.

How to cook with gas welding? Mixing oxygen with gases is the same. In the cutter, the flame amplifier is combined with ethyne and the vapor comes out of the burner nozzle after ignition with a blue fire.

Welding differences

Hot setting of metals is carried out using the following methods:

Burner step to the left. Suitable for thin and high-melting steel. The torch with the worker’s right hand moves to the left, and the welding wire is located slightly further than the flame along the line of the future connection;

Move to the right. The lever with the flame moves along the specified route, and the additive follows the burner. The flame energy is dissipated less, and the opening of the seam is not a right angle, but only 60-70 degrees.

Suitable for iron of 3 mm and above, as well as with high thermal conductivity. In both cases, the diameter of the additive is consistent with the thickness of the iron being fastened - half as much.

One practical subtlety of the Fouché and Picard method is melt baths. If you cook metal correctly, the bath constantly follows the burner. It is an indicator of quality welding.

At the place where the melting temperature arose, the metal seems to become liquid. It is at this moment that the filler wire enters the steel, also melts, and this “river” flows along the seam. In it, the melt of the additive plays an important role in strengthening the seam of the material. The bath firmly bonds thin strips and tubes of steel with low carbon content and alloying below five percent.

Differences between different seams:

• along the horizontal and ceilings, the right method is chosen, when metal does not flow from the “bath”;
• vertically and inclinations - using the left method;

This distinguishes the use of gas welding in various industries.

Photo of gas welding of metals

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Source: https://instrumentgid.ru/texnologiya-gazovoj-svarki-metallov/

How to cook with gas welding

Nowadays, questions often arise about how to weld using gas welding, what welding techniques and methods are optimal depending on the type of materials being welded. Precise recommendations will help those who are encountering gas welding for the first time and will help them avoid common mistakes.

Instructions

• Modern recommendations on how to cook with gas welding begin with the choice of equipment and familiarization with safety precautions when using a gas cylinder. After reading the instructions, first decide what exactly you are going to gas weld - steel pipes, a leaking tank or other surfaces, since welding techniques differ significantly in each of these cases. First, first prepare a gas cylinder for oxy-acetylene gas welding, suitable for welding various surfaces even in hard-to-reach places.
• Buy a torch with four tips, use the smallest one first to practice all the necessary movements and skills on it. Secondly, properly maintain the pressure in all hoses of the device, while setting it separately for both oxygen and acetylene. In this case, the oxygen pressure should not exceed 0.3 MPa, and for acetylene this figure should not be lower than 1 kPa. An oxygen hose belonging to class III is also suitable for gas welding work, since it can supply oxygen to the gas cylinder with optimal pressure, which is provided by the gas welding technique for small connections.
• If you want to get a beautiful seam on a product, you can use G3, but such a gas welding unit requires certain skills, and no less attention should be paid to safety precautions. When starting gas welding work, be sure to wear very thick pants and a jacket, and a hat on your head, as you risk burning your hair. Take care of your eyes, it is better to use not household sunglasses, but a special welding mask that covers your face almost completely.
• The full technology of gas welding will become available to novice welders after completing special courses. Only in this case will you learn how to choose a torch for gas welding, selecting it depending on the type of surface to be welded. Remember that you need to hold the device at the optimal angle, and the process of gas welding metal pipes, assemblies and components of a car, and patching holes in tanks is significantly different.
• In each case, the pressure in the hoses for oxygen and acetylene must be different, the burner will have to be held at different angles to make a beautiful, even seam. Subsequently, after performing gas welding work, clean off the scale correctly, giving the product the most attractive appearance.

Tip 2: How to learn to weld

Sooner or later, the need arises to connect two metal parts by welding, be it a garden tool or the installation of some kind of metal structure. It would seem that there is only one way out - contact a professional welder. But by purchasing a welding machine and the necessary equipment, you can learn this art yourself. The best teacher in learning is practice.

You will need

Welding machine, protective mask, jacket, trousers and gloves made of thick leather and canvas.

Tip 3: How to arc weld

Welding is a process of joining metals by establishing interatomic bonds between the parts being welded during heating or plastic deformation. Various energy sources are used to perform welding: laser radiation, gas flame, friction, ultrasound. One popular welding method is electric arc welding.

Technology of gas welding of metals: materials, equipment

This method of joining metal parts, such as gas welding, has been around for over a hundred years. During this time, this technology continues to be successfully improved, although other welding methods that use an electric arc are developing more actively and are replacing welding, which uses a gas torch.

Pros and cons of gas welding

This method of joining metals, such as gas welding, involves melting the materials being joined, resulting in the formation of a homogeneous structure. The combustion of gas, due to which the metal is heated and melted, is ensured by introducing pure oxygen into the gas mixture. This method of joining metals has a number of advantages.

• This welding method does not require the use of complex equipment (welding inverter or semi-automatic machine).
• All consumables for such welding are easy to purchase.
• Gas welding (and, accordingly, gas welding of pipes) can be performed even without a powerful energy source and sometimes without special protective equipment.
• The process of such welding can be easily regulated: you can set the required burner flame power and control the degree of heating of the metal.

This method also has disadvantages.

• The metal heats up very slowly, unlike using an electric arc.
• The heat zone that is formed by the gas burner is very wide.
• It is very difficult to concentrate the heat created by a gas burner; it is more dispersed compared to the electric arc method.
• Gas welding can be classified as a fairly expensive method of joining metals when compared with electric arc welding. The cost of oxygen and acetylene consumed significantly exceeds the cost of electricity spent to weld similar parts.
• When welding thick metal parts, the speed of the connection is significantly reduced. This is due to the fact that the heat concentration when using a gas burner is very low.
• Gas welding is difficult to automate. Only the process of gas welding of thin-walled pipes or tanks, which is performed using a multi-flame torch, can be mechanized.

Gas welding of a pipe from the bottom position

Materials for welding using gas

Gas welding technology involves the use of various types of gases, the choice of which depends on a number of factors.

One of the gases used for welding is oxygen. This gas is characterized by the absence of color and odor; it acts as a catalyst, activating the melting processes of the material being joined or cut.

In order to store and transport oxygen, special cylinders are used in which it is kept under constant pressure. Oxygen may ignite upon contact with industrial oil, so the possibility of such contact should be excluded. Cylinders containing oxygen must be stored indoors, protected from sources of heat and sunlight.

Welding oxygen is obtained by separating it from ordinary air, for which special devices are used. Depending on the degree of its purity, oxygen is of three types: the highest (99.5%), first (99.2%) and second (98.5%) grade.

For various manipulations with metals (welding and cutting), colorless acetylene gas C2H2 is also used. Under certain conditions (pressure exceeding 1.5 kg/cm2 and temperature exceeding 400 degrees), this gas can spontaneously explode. Acetylene is produced by the interaction of calcium carbide and water.

Acetylene gearbox design

The advantage of using acetylene when welding metals is that its combustion temperature allows this process to be carried out without problems. Meanwhile, the use of cheaper gases (hydrogen, methane, propane, kerosene vapor) does not make it possible to obtain such a high combustion temperature.

Wire and flux for welding

To weld metals, in addition to gas, you also need wire and flux. It is due to these materials that the welding seam is created and all its characteristics are formed. The wire used for welding must be clean, without signs of corrosion and paint on its surface. In some cases, a strip of the same metal that is being welded can be used as such wire.

In order to protect the weld pool from external factors, it is necessary to use a special flux. Boric acid and borax are often used as such flux, which are applied directly to the surface of the metal being welded or to the wire used for welding.

Gas welding of carbon steel can be performed without flux, and when joining parts made of aluminum, copper, magnesium and their alloys, such protection is necessary.

Gas welding equipment

Gas welding technology involves the use of certain equipment.

Equipment required for welding

Water seal

A water seal is necessary to ensure protection of all elements of equipment (acetylene generator, pipes) from the backdraft of fire from the burner. Such a valve, in which the water must be at a certain level, is placed between the gas burner and the acetylene generator.

A cylinder containing gas

Such cylinders are painted with different colors depending on what gas is planned to be stored in them. Meanwhile, the top part of the cylinder is not painted to prevent gas from contacting the paint components. It should also be borne in mind that cylinders in which acetylene is stored should not be fitted with copper valves, as this may lead to a gas explosion.

Gearbox

It is used to reduce the pressure of the gas leaving the cylinder. Gearboxes can be direct or reverse acting, and for liquefied gas, models with fins are used, which prevent it from freezing upon exit.

Special hoses

Gas welding cannot be performed without the use of special hoses, through which both gas and flammable liquids can be supplied. Such hoses are divided into three categories, marked with 1) a red stripe (operate at pressures up to 6 atmospheres), 2) a yellow stripe (for supplying flammable liquids), 3) a blue stripe (operate at pressures up to 20 atm).

Gas welding cutter device

Burner

Mixing of gases and their combustion is ensured through the use of a burner, which can be of an injection or non-injector type. Burners are also classified according to their power, which characterizes the amount of gas passed per unit of time. So, there are burners of high, medium, low and micro-low power.

Special table

Gas welding is carried out in a specially equipped place called a post. Essentially, such a place is a table, which can have a rotating or fixed top. This table, equipped with exhaust ventilation and everything necessary for storing auxiliary tools, greatly facilitates the work of the welder.

Features of gas welding

The flame parameters are adjusted using a gearbox, which allows you to change the composition of the gas mixture.

Using a reducer, you can produce three main types of flame: reducing (used for welding almost all metals), oxidizing and with an increased amount of combustible gas.

When welding metals in a molten pool, two processes occur simultaneously - oxidation and reduction. At the same time, when welding aluminum and magnesium, oxidative processes occur more actively.

The welding seam itself and the area adjacent to it are characterized by different parameters. Thus, the section of metal adjacent to the seam is characterized by minimal strength, and it is this area that is most prone to destruction. The metal adjacent to this zone has a structure with large grains.

To improve the quality of the seam and the area adjacent to it, additional heating or so-called thermal forging of the metal is performed.

Welding technologies for various metals have their own nuances.

• Gas welding of low-carbon steel parts is performed using any gas. When welding such steels, steel wire containing a small amount of carbon is used as a filler material.
• Welding methods for alloy steels are selected depending on their composition. Thus, stainless heat-resistant steels are welded using wire containing chromium and nickel, and certain grades require the use of filler material additionally containing molybdenum.
• Cast iron is cooked with a carburizing flame, which prevents pyrolysis of silicon and the formation of grains of brittle white cast iron.
• To weld copper, it is necessary to use a higher power flame. In addition, due to the increased fluidity of copper, parts made from it are welded with a minimum gap. Copper wire is used as a filler material, as well as flux, which promotes deoxidation of the weld metal.
• When welding brass, there is a risk of zinc evaporating from its composition, which can lead to increased porosity of the weld metal. To avoid this, more oxygen is supplied to the burner flame, and brass wire is used as an additive.
• Welding of bronze is carried out with a reducing flame, which does not burn out tin, aluminum and silicon from this alloy. Bronze wire of a similar composition is used as an additive, which additionally contains silicon, which promotes deoxidation of the weld metal.

How gas welding is performed in semi-automatic mode

Semi-automatic gas welding technology requires the use of an electric arc and shielding gas, which makes this method of joining metals a hybrid.

This technology, if we look at it in more detail, looks like this:

• turning on the device;
• threading the wire through a hole located in the burner;
• setting the required gas pressure using a reducer;
• setting the required wire feed speed;
• setting all other welding parameters (voltage and current);
• positioning the torch at the required angle before starting welding.

For each of the welding parameters performed semi-automatically, there are parameters that are specified by the relevant GOSTs:

• pressure generated by the reducer;
• acetylene generator parameters;
• type of hoses used;
• requirements for gas cylinders;
• type of torches used for welding;
• type of wire used for welding.

Source: http://met-all.org/obrabotka/svarka/tehnologiya-gazovoj-svarki-metallov-materialy-tehnika.html

How to use gas welding - Machine tools, welding, metalworking

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.

Advantages and disadvantages

Like any thing or phenomenon, the advantages of gas welding are a direct reflection of its disadvantages, and vice versa.

The main characteristic of gas welding is a lower heating rate of the melted zone and wider boundaries of this zone. In some cases this is a plus, in others it is a minus.

This is a plus if you need to weld parts made of tool steel, non-ferrous metals or cast iron. They require smooth heating and smooth cooling. There are also a number of steels for specialized purposes for which this particular processing mode is optimal.

Other advantages include:

• low complexity of the gas welding technological process;
• availability, adequate cost of equipment;
• availability of a gas mixture or calcium carbide;
• no need for a powerful energy source;
• flame power control;
• flame type control;
• possibility of mode control.

There are four main disadvantages of gas welding. The first is precisely the low heating rate and high heat dissipation (relatively low efficiency). Because of this, it is almost impossible to weld metal thicker than 5 mm.

The second is too wide a thermally affected zone, that is, a heating zone. The third is cost. The price of acetylene consumed during gas welding is higher than the price of electricity spent on the same amount of work.

Its fourth drawback is its weak mechanization potential. Due to its operating principle, only manual gas welding can actually be implemented.

A semi-automatic method is not possible; an automatic method can only be done using a multi-flame torch, and only when welding thin-walled pipes or other tanks. This method is complex and cost-effective only in the production of hollow tanks made of aluminum, cast iron or some of their alloys.

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.

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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://stanki-info.com/kak-polzovatsya-gazosvarkoy/

Gas welding technology - technique, modes, equipment

Gas welding is one of the types and methods of joining metals and their alloys under high temperature. Today we’ll talk about the basics, its technology, methods and techniques, advantages and disadvantages. This article will be useful for novice gas welders who want to master this difficult profession, as well as experienced craftsmen who want to strengthen their knowledge in this area.

Gas welding technology

This is a method of welding parts, during which the edges of parts and filler wire are melted using a gas torch. The flame is formed from the combustion of a mixture of oxygen and acetylene; by the way, it can be replaced with other gases. For this, butane, acetylene, gasoline, hydrogen and other substances are used. Depending on the technical gases used, it is customary to distinguish the following types of gas welding:

•  acetylene-oxygen;
•  kerosene-oxygen;
•  gasoline-oxygen;
• propane-butane-oxygen.

The essence of gas welding is the following: the heat generated during combustion of the gas mixture melts the edges of the workpiece and additive, thus forming a weld pool.

The flame used for welding can be divided into the following components:

• normal;
• oxidative;
• restorative.

Gas burner flame characteristics

The chemical composition of the additive for forming the future weld is selected based on what material is being welded, and its size depends on the thickness of the metal being welded.

The oxygen contained in the steel cylinder passes through a reducer, which reduces the gas pressure and through the hoses, it arrives at the place of work. The same path is repeated by flammable gas (acetylene or its analogues).

Equipment and materials used in gas welding

The mixture is mixed in the burner in the required proportion and ignited at the moment the mixture comes out of it. The flame in this case performs three functions at once:

1. Melts metal
2. Melts the material that acts as an additive;
3. Protects the place where the workpieces are joined from exposure to atmospheric oxygen.

The flow of oxygen and gas is regulated using valves installed on gas cylinders.

The combustion temperature reaches its maximum in the reducing part of the flame. This is where the additive and the edges of the parts to be welded should be located. If you replace acetylene, the flame temperature will be reduced.

Edge preparation

An important stage in the quality of a seam is the correct cutting of the edges, which depends on the thickness of the metal being prepared.

Metal thickness	Cutting form	Angle, °	Gap between the ends of the workpieces, mm	Additional events
0,5-2	not produced	–	–	Trimming or beading edges. Welding without additive, butt
1-5	not produced	–	0,5 – 2	Welding with filler
4-8	allowed not to produce	–	1 – 2	Double-sided seam
5-10	V-shaped	70-90	2-4	Edge blunting 1.5 -3mm
over 10	X-shaped	35-45	2-4	Dullness 2-4 mm

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It is necessary to clean an area of ​​20-30 mm from the surfaces to be welded from dirt, paint, and scale.

Gas welding modes

characteristic of gas welding is the power of the flame. It depends on the type of metal and a number of its other characteristics, for example, thermophysical properties. In other words, the thicker the metal, the higher the melting point of the metal, the higher the flame temperature should be.

The power of the flame determines the consumption of combustible gas and oxygen. For example, when processing steel or cast iron, the consumption of the amount of gas and the thickness of the metal is related by the following proportion:

Va (100–150)*S l/h, where Va is the consumption of combustible gas, S is the thickness of the metal.

This parameter is adjusted by selecting the burner tip number:

In addition, the angle of the burner and the size of the additive play an important role. Thus, the welding parameters and modes include:

1. The power of the flame and its character;
2. Filler wire diameter;
3. Welding speed, determined by the methods of making welds and the position of the nozzle relative to the plane of the workpiece.

Left way

With this method of welding parts, the welder moves the torch from right to left, the additive should be located in front of the torch. The flame is directed from the seam. This provides the welder with a good view of the seam and, as a result, he can ensure uniform width and height of the bead. This welding method is used when working with parts up to 5 mm.

Right way

This method involves the welder moving the torch from left to right. The wire should move behind the torch. The flame is directed towards the seam. With this method, the cooling of the seam takes longer and the quality of the seam improves, but its appearance leaves much to be desired, since the welder cannot really see its formation. This method is used for sheet thickness greater than 5 mm.

Filler wire diameter

The selection of the diameter of the additive (dп) is carried out depending on the thickness of the metal being welded (S), as well as on the welding method: left or right.

The main parameters of gas welding of common types and compositions of steels can be presented in the form of a table

Burner mouthpiece position

The speed of acetylene welding or metal melting is adjusted by changing the angle of the nozzle relative to the plane of the metal being welded. It is determined by the thermal conductivity, thickness and type of metal. Thick metal with high thermal conductivity requires a larger angle of inclination of the torch due to long heating times and the application of the greatest flame power to form a weld pool.

To understand the nature of the effect of flame on metal at different positions, just look at the figure below.

As you can see, maximum penetration occurs when the burner is in a vertical position. That is why at the beginning of welding, for better and faster heating, the mouthpiece is placed at an angle of 90 °, gradually reducing it in accordance with the thickness of the metal.

Important! The final stage of gas welding (crater formation) is performed at a minimum angle to prevent metal burning.

Torch movements

During work, the welder makes longitudinal and transverse movements with the torch. The main type is longitudinal, it is directed along the seam line, designed to fill a metal seam. The transverse movement is performed to uniformly heat the edges of the metal and is intended to form the required seam width.

In turn, the movements of the filler are carried out by the same oscillatory movements, but in the opposite direction to the movement of the end of the burner. To avoid defects in the weld, it is not recommended to remove the end of the filler from the weld pool, especially from the recovery zone of the flame.

The type of movement depends on the spatial position of the seam, its geometric dimensions, thickness and type of metal.

Down position

Welding in the lower position is the simplest; in this case it is easiest to control the process of seam formation. The likelihood of lack of penetration and the appearance of other defects is reduced. The technique used is, as a rule, spiral-shaped movements of the end of the autogen mouthpiece. The additive is lowered into the heated weld pool, a “loop” is made and the operation is repeated. Each subsequent turn should overlap the previous one by 1/3 of the diameter.

Thin sheets are butt welded by flanging the edges, i.e. the edges of the workpieces are bent and welded without the use of filler wire. You can use both right and left connection methods.

Lap seams

Work should be carried out, if possible, without interruptions. If you pause, before repeating the process, melt the metal that has crystallized in the crater. Welding is carried out using the left-hand method with filler material. When working with this type of connection, it is more advisable to use arc technologies, as they are less expensive and more productive. This will especially affect large volumes.

Vertical position

Possible options for making vertical seams both from top to bottom and from bottom to top. In the first case, the right method is used (used when the metal thickness is small), in the second method, both options are possible. A certain amount of skill is required to hold the weld pool and prevent it from flowing down. It is ensured by the correct position of the mouthpiece, as well as the pressure of the gas flame.

If the parts are significantly thick (up to 20 mm), filling the seam with metal should be done with a double roller. In this case, edge preparation is not required; the gap between the parts should be half the thickness of the workpieces being welded.

Ceiling position

Requires accuracy and maximum concentration. Before feeding the wire, the edges are heated. When they begin to melt, wire is introduced into the weld pool zones. The end of the filler melts quickly, forming a weld. The metal is held in the weld pool by flame pressure. Cook in the right way in several stages, making each layer small in thickness. To prevent the metal from flowing down the rod, it should be kept closer to the horizontal plane of the ceiling seam.

Economic component of gas welding

There are often cases when a process engineer makes a choice in favor of gas welding, sincerely believing that in this way he will achieve financial savings. But it's not that simple. Yes, electric arc welding consumes a large amount of energy, but by performing simple arithmetic calculations you can make sure that the costs of electric welding, for the same amount of work, are lower than gas ones. Therefore, before gas welding, it is important to calculate how much one meter of seam will cost.

Low heat concentration during gas welding has a negative impact on its performance. So, when working with sheet steel 1 mm thick, the average welding speed is 10 meters per hour, while with a sheet thickness of 10 mm, the speed will drop to 2 meters per hour. That is why gas welding is used when working with steel up to 5 mm thick. In other cases, electric welding is used.

Acetylene-oxygen welding is practically not mechanized. Automatic welding is used when working with thin-walled pipes. For this purpose, burners are used, on which several mouthpieces are installed.

Areas of use of welding

Welding of this type differs from electric arc welding in the gradual heating of the metal. Perhaps this determined the areas of its use. Gas welding shows maximum effect when working with steel up to five millimeters thick. This welding technology is successfully used in the processing of non-ferrous metals. Gas welding is used to work with materials that require preheating. When choosing gas welding, the designer must be guided by the requirements of GOST.

Gas welding is used for repair work and soldering. It is used to restore worn parts, such as crankshafts. To do this, a layer of metal is fused onto the worn surface. Subsequently, the overlay area will be polished and brought to the required size.

Source: https://svarkagid.ru/tehnologii/sushhnost-i-rezhimy-gazovoj-atsetilenovoj-svarki.html

How to cook with gas welding?

Gas welding is the most common type of welded surfaces when it comes to industry and domestic use. Professionals say that the gas welding method is the easiest to master. Creating a high-quality seam does not require a lot of experience.

On the website http://mos-weld.com/ you can find everything you need for gas welding: burners, cylinders, etc. This article will help you understand the technological process of welding using flammable gases.

Gases that can be used in gas welding

Below are the main types of gases used in practice:

• diacin;
• hydrogen;
• oxygen;
• acetylene;
• propane, etc.

However, only acetylene has gained the greatest popularity in practice. The fact is that a large amount of oxidizer is not required to ignite it and maintain combustion.

Do not forget that gas welding is a rather complex technological process.

It is strongly recommended to enroll in a specialized technical training institution, which will allow you to learn all the basics, as well as the technique of performing welding work.

Technical process of performing oxy-acetylene welding

You must first select the burner itself. It must have at least 4 tips. It is recommended to use the thinnest one. It is essential that there is a constant supply of oxygen.

To do this, its pressure must be stable. The recommended pressure for oxygen during the welding process is 0.3 MPa. Acetylene itself must be supplied at a pressure of 1 kPa

It must be remembered that to ensure high quality welds, it is recommended to hold the torch at a certain angle to the surfaces being welded. Only in this way can not only a beautiful, but also a high-quality, reliable seam be achieved.

Source: http://urokremonta.ru/stroisov/instr-stroisov/kak-varit-gazosvarkoy.html