What is welding flux used for?

Submerged arc welding - modes, features

Anyone familiar with welding processes knows how negatively air affects the quality of the weld. That is why the highest quality connection is considered to be a process that is carried out in an environment of protective materials. Typically, inert gases or fluxes are used for this. Submerged arc welding is not used so often today, especially in domestic conditions.

But in industry, this type of metal welding is used much more often. Moreover, the quality of the seam with this technology is guaranteed to have high quality characteristics. Therefore, when talking about submerged arc welding, it is necessary to understand that this process is semi-automatic or automatic.

In some industrial production, robotic welding using fluxes is installed.

What is welding under protective fluxes

Essentially, this is the same welding process using non-consumable electrodes and filler wire. Only instead of gas, which covers the welding zone, flux is used - a powdery material poured over the junction of two metal workpieces.

At high welding temperatures, the flux melts and releases the same protective gas. In this case, a durable film is formed over the welding zone, protecting it from the negative effects of ambient air. The burnt powder turns into slag, which is easily removed from the welded seam. Remaining flux can be collected and used elsewhere.

But the most important thing is that all positions associated with connecting the joined parts are exactly the same as in the case of using other welding technologies. Namely:

• correct selection of welding mode, which depends on the structure of the metals being joined;
• correct choice of electrode;
• filler wire, which in its properties must correspond to the properties of the base metals;
• competent formation of edges;
• cleaning the ends of parts, degreasing them.

But there is one distinctive feature - the correct choice of flux.

Types of fluxes

As mentioned above, flux for welding is a powder with granule sizes of 0.2-4 mm. Its classification depends on many indicators. But there are basic characteristics that divide it into groups and classes.

According to the production method, welding fluxes are divided into:

• fused: their components are first melted, then granulated, calcined and separated into fractions;
• unfused or ceramic: these are dry ingredients that are mixed with liquid glass, dried, granulated, calcined and separated into fractions.

Manufacturers and experts note the fused version as the best of the two presented.

Separation by chemical composition.

• Oxide fluxes. The powder contains up to 90% metal oxides and the rest is fluoride compounds. This group has subgroups that determine the percentage of a particular oxide. For example, silicon oxide. If it is contained in the flux up to 1%, then such a powder is called silicon-free, if its content is 6-35% - low-silicon and more than 35% - high-silicon. Oxide fluxes are designed for welding low-carbon and fluoride steel workpieces.
• Saline. They do not contain metal oxides; they are based on salts: fluorides and chlorides. This powder is used for welding active metals, for example, titanium.
• Mixed fluxes (salt oxide). They contain both oxides and salts. They are used to join alloyed alloys.

Another characteristic is the activity of fluxes. Essentially, this is the rate of oxidation of the powder when it is heated. This indicator is measured from zero to one and divides fluxes into four categories:

1. Less than 0.1 are passive materials.
2. From 0.1 to 0.3 – inactive.
3. From 0.3 to 0.6 – active.
4. Above 0.6 – highly active.

And one last thing. This is a division based on the structure of the granules. There are three positions: vitreous, pumiceous and cemented. It should be noted that welding with a glassy flux produces a wider weld than with a pumice flux. If a powder with small particles is used, then the seam underneath is deep and narrow with high strength properties.

Useful tips

• The transition of metals (manganese and silicon) into the weld metal is of great importance in submerged arc welding technology. Manganese is transferred faster if the concentration of its oxide (MnO) is greater than that of silicon oxide (SiO2). The lower the flux activity, the faster the transition occurs.
• Pores form in the seams if the flux has not been well dried, if it does not match the properties of the metal of the workpieces being welded and the metal of the filler wire, if there is too much gap between the parts, if the flux layer is insufficient, if its qualities are low.
• Hydrogen has a negative effect on the welding seam. Therefore, it is bound into insoluble compounds using fluxes. This is best done by a powder with a high silicon content and a pumice-like granule shape.
• To prevent cracks from forming in the weld, fluxes with a high content of both silicon and manganese are needed.

Today, double or two-electrode welding is increasingly used in industry, in which the electrodes are located at a distance of less than 20 mm from each other and are powered by a single source of electrical energy. At the same time, they are welded in one zone, forming a single weld pool. The electrodes can be located both in a longitudinal and transverse position.

Double-arc welding is also used, in which consumables are powered from two different sources, and the current on the two rods can be alternating or constant. Or it may be different. The location of the electrodes can be perpendicular to the welding plane or at an angle. By varying the angle of inclination, you can increase or decrease the depth of welding. The width of the seam will change accordingly.

Submerged arc welding can also be carried out when the distance between consumables is increased. In this case, welding will be carried out in parallel in two baths. But the first electrode will serve as a heater for the welding zone, the second will weld it.

With this technology for joining metal workpieces, the electrodes are installed perpendicular to the welding plane.

This method is distinguished by the fact that during welding with two electrodes, hardening areas are not formed both in the weld itself and in the adjacent areas on the main parts.

Submerged Welding Modes

It should be noted that mechanized submerged arc welding differs from manual welding in that it becomes possible to use high-density welding current. It varies in the range of 25-100 A/mm². Accordingly, more current will be used. This is reflected in deep welding of the seam, the ability to weld thick-walled workpieces without forming edges, and increasing the speed of the process itself.

For example, when welding parts with a thickness of 20-40 mm using single-arc manual welding, the process speed is no more than 70 m/hour. Using double-arc welding, you can increase this figure to 300 m/hour. Of course, the current strength is selected mainly based on the diameter of the electrode used. The table shows their relationship with each other.

Electrode diameter, mm	Welding current strength, A
2	200-400
3	300-600
4	400-800
5	700-1000
6	700-1200

It should be added that flux-cored welding technology is also economical. The thing is that the consumption of materials is reduced due to less spattering of metal, for example, in manual welding this figure is 15%, in flux mechanized welding it is less than 3%.

The volume of waste is reduced, cinders and other unpleasant moments are not formed. Conserving heat under flux also makes it possible to save energy. It has already been proven that the reduction in electrical current consumption occurs by up to 40%.

Labor costs, which are usually spent on forming edges and cleaning the seam after welding from scale, splashes and slag, are also reduced.

The only negative is the restriction on the position of the weld pool. You can cook in the lower position using automatic or semi-automatic devices or with a slight tilt within 10-15°.

Be sure to watch the video, which shows how you can submerge weld two metal parts.

Source: https://svarkalegko.com/tehonology/svarka-pod-flyusom.html

Welding fluxes for quality welding

Fluxes for welding: what is it and how to use it? This question worries many novice craftsmen. In this article we will explain in detail what welding fluxes are, what their operating principle is, where and how they can be used.

During welding work, chemical activity begins to increase directly at the welding site. This applies to both arc and gas welding. For this reason, the metal quickly oxidizes, the welding wire loses some of its material, and overall melting efficiency decreases. The welder has to weld parts longer, which causes unnecessary slag to accumulate in the weld pool.

To avoid such problems, professionals use welding flux - a special material that ensures stable arc burning and removes unnecessary impurities.

What does flux look like? In most cases, it is loose granules of small diameter, sold in bags of various sizes (on average 20-25 kilograms), but there are materials in other designs.

We talk about this in detail in the Classification section. But first, let's look at the principle of operation of fluxes.

Operating principle

First, to understand the principle of flux action, you need to understand what a typical welding zone consists of:

• An area of ​​an arc column with an internal temperature of 4-5 thousand degrees Celsius.
• An area of ​​a gas bubble that is formed due to intense atomic evaporation of components in an oxygen environment.
• An area with molten slag located in the upper part of the gas cavity.
• A layer of molten metal at the bottom of the cavity.
• A slag crust that forms a hard boundary to the welding zone.

In addition to the areas mentioned above, the welding wire is no less important, it also affects the chemical reactivity.

Now that we understand what the welding zone consists of, we move on to flux. During welding, the surface of the part is actively oxidized and a slag crust is formed. These processes can be avoided if an easily melting inert material enters the welding zone. This type of material is welding flux. It will protect the part from oxidation and contribute to the formation of a high-quality seam.

To effectively use fluxes in your work, you must meet the following conditions:

• The material should stabilize the speed of work, not slow it down.
• It must not react chemically with the surface of the parts being welded or the welding wire.
• The gas bubble must be isolated from the environment throughout the entire operation.
• If all recommendations are followed, flux residues should be easily removed after welding. In this case, most of the removed material can be reused (after cleaning).

In practice, it turns out that meeting these requirements is not so easy. The flux may vary in composition, as well as the technology for feeding it into the welding zone, so you need to consider what kind of metals you are welding and what type of welding you use.

Classification

In order to classify welding fluxes in more detail, we divided them into conditional categories. So, materials may differ in the following categories:

• Appearance. At the beginning of the article, we mentioned that the material can be granular, but manufacturers also offer crystalline, paste and even gas flux. The choice depends on the work ahead. For electric welding, the material is often used in the form of granules or powder, while for gas welding, a paste or gas flux is used.
• Chemical composition. The composition of flux can vary greatly and consist of many components, but the base is often silica and manganese. A more detailed composition of the flux can be easily found on the Internet or read on the packaging. Let's just say one thing: the flux used must maintain its chemical inertness in operation even at very high temperatures. This is one of the main requirements for quality material.
• Purpose. As we discussed in the “Principle of Operation” section, you need to consider exactly what metals you are welding and what type of welding you are using. For example, using flux with alloyed wire will give a positive result by improving the strength of the metal. Of course, there are also universal fluxes, but we recommend using them for welding non-ferrous metals or alloys, and for welding we began to choose the flux more carefully.

More generally, fluxes are divided into melting and non-melting. Consumable ones are very effective if surfacing is required, while non-consumable ones improve the mechanical characteristics of the finished weld. For this reason, they are often used with high-carbon steels or non-ferrous metals, which cannot be welded well without flux.

The use of flux in welding work

To weld steel manually, flux is applied to the surface in a layer of about half a centimeter. Do not skimp on the amount of material used, since insufficient layer thickness can lead to poor welding of the metal, which subsequently leads to the formation of cracks. Flux is gradually added throughout the work in those places where the electrode moves.

In semi-automatic or fully automatic welding, flux is used in the following way: the material is fed through a special tube, and later the welding wire is fed, located next to the flux. During welding, the unused part of the material is removed using a pneumatic method. Subsequently, the slag crust is removed from the weld surface.


What positive effect does flux have:

• There is no need to cut the edges of the future weld, because the metal melts much more intensely, regardless of the welding method.
• There is no waste of metal in the weld area and its surface, which helps to improve the quality of the work done.
• Arc burning is much more stable.
• The efficiency of the power source increases because the loss of energy spent on heating the part is reduced.
• The welder receives comfortable working conditions because his flux shields most of the arc flame.

But there are also limitations. If you do not have the opportunity to first inspect the area where you are welding steel (or any other metal), then we do not recommend using fluxes. Their use requires training (both of the welder and the parts being welded). In addition, the material is expensive and is used in the same quantity as wire. So in an unprepared situation, using flux may not be advisable.

However, working with flux is quite effective. When welding, the metal does not spatter, the welding wire lasts longer, and overall the welder’s productivity increases. After all, using flux, you can safely set high current parameters, while the seam will remain of the same quality.

Instead of a conclusion

Welding fluxes are a great way to optimize your work and improve the quality of your work. Yes, its use requires preparation, and the cost of the material may seem overpriced. But we believe that the positive result more than offsets the few shortcomings. Try fluxes in your work and share your experience in the comments, perhaps it will be useful to other welders.

Source: https://svarkaed.ru/rashodnye-materialy/flyus-i-svarochnaya-provoloka/flyus_dlya_svarki.html

Application of welding flux, principle of operation, classification and production process

In the process of electric arc and gas welding, the high-temperature zone significantly increases chemical activity, as a result of which the metal is intensively oxidized, part of the welding wire material evaporates, and the intensity of metallurgical processes decreases, which is why melting is not particularly effective. As the welding time increases, more and more slag accumulates in the pool. Therefore, this zone must be isolated, which is achieved by using welding fluxes - non-metallic compositions with certain properties.

The welding zone during a steady process includes the following areas:

• Arc column zone with an internal temperature of 4000−5000 °C.
• A zone of a gas bubble formed as a result of intense evaporation of atoms in an oxygen environment.
• Melted slag, which is lighter than metal and is located at the top of the gas cavity.
• Molten metal is at the bottom of the cavity.
• A slag crust that forms the upper, hard boundary of the welding zone.

The behavior of the material being welded is also affected by the welding wire. Thus, any welding is a miniature metallurgical process.

The welded metal can be protected from slag crust and oxidation, which deteriorate the quality of the weld, by continuously supplying fusible and at the same time chemically inert components into the welding zone, which are welding fluxes. The materials can also be used for surface surfacing. Using flux reduces the amount of dust that inevitably forms during operation.

These materials must be used under the following conditions:

• The flux should not reduce productivity, but stabilize the process.
• There should be no chemical reaction of the flux with the base metal or welding wire.
• During the operating cycle, the welding bubble area must be isolated from the environment.
• At the end of the process, the residues, binding to the slag crust, should be easily removed from the working area. Moreover, up to 80% of waste material can be used again after cleaning.

Since these requirements can even be called contradictory, the optimal composition of the flux and the method of its supply is determined by the specific type of welding, the configuration of the parts being joined and the performance of the process.

Classification of welding fluxes

Varieties of fluxes are characterized by the following parameters:

• Appearance. They come in powdery, granular, gas, and paste form. For example, for surfacing or electric welding, powder or small granules are used (and the material must have appropriate electrical conductivity). For soldering or gas welding, it is better to take paste, powder or gas.
• Chemical composition. Chemical inertness at high temperatures and the ability to effectively diffuse a number of components into the weld metal are required.
• Method of receipt. Melting and non-melting. The former are effective in surfacing, when the metal surface must effectively complement other chemical elements. The second group serves to improve the mechanical properties of the finished seam, so they are used when welding high-carbon steels and non-ferrous metals, for example, aluminum, which is difficult to weld under normal conditions.
• Appointment. Alloyed flux welding wire, for example, can improve the chemical composition and increase the mechanical strength of the parent metal. Universal fluxes are highly valued and can be used for welding steel, non-ferrous metals and alloys.

Typical constituents are manganese and silica , but metals and ferroalloys may be included for alloying purposes.

Classification is often made by brand. It is determined by the manufacturer. For example, brands developed by the Institute of Electric Welding named after. Paton, the designation must have the letters AH. If the letters FC are present, it means that the flux was developed by the Central Research Institute of Transport Engineering. Although the recipe for making materials is standardized, there is no uniform marking.

The base of unfused fluxes is ceramic, and these materials are obtained by mechanically grinding the components in ball mills. Depending on the size of the fractions, fluxes are divided into fine (with a grain size of 0.25−1.0 mm) and normal (with a grain size up to 4 mm).

The former are used when welding with wire of small diameters, no more than 1.0−1.5 mm, the letter M is added to the designation.

If there are a significant number of components in the unfused flux, they are first bonded together by gluing, and then the particles are ground to the desired size.

In addition to silica, unmelted fluxes contain ferroalloys, manganese ore, oxides of a number of elements, and metal powders. Components are selected according to their ability to enhance the metallurgical process in the welding zone. As a result, the conditions for surface alloying and deoxidation of the metal are improved, the grain size of the weld becomes finer, and the amount of harmful impurities in it decreases. The alloying ability of unfused materials allows the use of cheaper welding wire.

The disadvantages of unfused fluxes include, for example, that their packaging must be denser, since the components are hygroscopic, and moisture degrades the quality of the material. Unfused fluxes are more demanding in terms of adherence to welding technology, since in this case the alloying conditions can change significantly.

Magnetic fluxes also belong to the unfused category. Their performance is similar to ceramic ones, but they additionally contain iron powder to increase performance.

Fused fluxes are mainly used in automatic welding . Their manufacturing technology includes the following steps:

1. Preparation and grinding of components, except for those used in unfused fluxes. This also includes fluorspar, chalk, alumina, etc.
2. Mixing a mechanical mixture in rotating mills.
3. Melting in gas-flame furnaces with a protective atmosphere or in electric arc furnaces.
4. Granulation to obtain the final fractions of the required grain size. For this purpose, the flux melt is released into water and hardens in it into spherical particles.
5. Drying in tumble dryers.
6. Sifting and packing.

Fused fluxes consist of silica SiO2 and manganese oxide. Manganese reduces iron oxides that are constantly formed during welding and binds sulfur in slag into sulfide, which is easily removed from the weld later. Silicon prevents the increase in carbon monoxide concentrations. The deoxidizing properties of the latter element increase the homogeneity of the chemical composition of the metal.

The color of fused fluxes is transparent or light yellow, and their density is no more than 1.6−1.8 g/cm3.

Effect of fluxes during welding

When manual welding, flux is poured in a 60-mm layer on the surface of the metal adjacent to the future joint. If the layer thickness is insufficient, lack of penetration and the formation of shells and cracks are possible. After this, during electric welding, a discharge is excited, and during gas-flame welding, the torch is ignited.

As the electrode moves, flux is added to new surfaces. Since the dimensions of the column in the arc are greater than the height of the flux, the discharge occurs in the liquid melt of the components acting on the metal melt with a specific pressure of up to 9 g/cm².

As a result, metal spattering is eliminated, less welding wire is consumed, and productivity increases. This is due to the flux's ability to handle higher operating currents without the risk of an intermittent weld.

A current of 450-500 A cannot be used during open welding, because the arc splashes the metal out of the pool.

In semi-automatic and automatic welding, fluxes are used as follows:

1. Flux is supplied from the hopper through a special tube.
2. Later, the electrode wire is fed from a coil located after the flux container.
3. As the working process progresses, part of the flux that is not used and bound by slag is sucked into a container by pneumatics.
4. The molten and cooled slag crust is mechanically removed from the seam.

Advantages of using fluxes:

• There is no need to pre-cut the edges of the future weld, since with high electric welding currents or increased oxygen concentrations during welding, gas metal melts much more intensely.
• No metal waste in the weld area and adjacent surfaces.
• More stable arc.
• Increasing the efficiency of the power source as a result of reducing energy losses that are spent on heating the metal, spattering it and increased consumption of flux and welding wire.
• Comfortable working conditions, because a significant part of the arc flame is shielded by flux.

Limitation of use is the impossibility of quickly inspecting the welded area. This circumstance requires more thorough preparatory work, especially when connecting parts with complex configurations. Fluxes also cost quite a lot, but they are consumed almost like welding wire.

Source: https://tokar.guru/svarka/izgotovlenie-i-ispolzovanie-svarochnogo-flyusa.html

Application of welding flux, principle of operation, classification and production process - Machine

Carrying out work involving the use of gas or electric arc welding is always associated with an increase in the chemical activity of the high-temperature zone in which the weld is formed.

As a result of chemical reactions, oxidation of the metal occurs with the formation of a characteristic film, evaporation of the additive, as well as a general decrease in the speed and quality of the metallurgical process. All this negatively affects the quality and efficiency of work as a whole.

An increase in the time of weld formation leads to the accumulation of slag in the weld pool. The solution to the problem is to isolate the area from atmospheric air.

To create protective conditions, special means are used that protect the heat-affected zone from oxygen and prevent the displacement of carbon from the molten metal. Such products are called fluxes. They can additionally strengthen the material with alloying elements.

Welding flux looks like small granules fed into the melting zone. Flux should be supplied precisely at the moment when a lit electric arc passes through the area. Different granules differ in color.

You can find coarse powder of yellow, black, white or transparent color.

How does it work

Regardless of the materials, when conducting arc welding, it is possible to identify the main elements of the working area in which the seam is formed.

Slag accumulates in the top layer, since it is lighter than molten metal. The metal itself is in the lower layer in a liquid state. The temperature inside the electric arc reaches 5000°C degrees.

Finally, as a result of the evaporation of the materials, a gas bubble is formed.

When welding is carried out in a semi-automatic mode, the picture changes somewhat due to the presence of wire, but the main elements remain unchanged. The slag crust and the oxidation process introduce negativity into the whole process.

As a result, cracks, pores and impurities form in the metal, which worsens the strength of the connection. To exclude the chemical activity of the material, it is necessary to use substances that provide protection in the form of a layer of inert gas.

To make work easier, flux is made from elements that have relatively low melting points.

Fluxes, in addition to protection from air, provide insulation of the weld pool from dust and foreign particles, and serve as a consumable material during surfacing. There are certain requirements for substances.

First of all, flux should not complicate the welding process. Its insulating properties cannot be partially demonstrated. If protection from atmospheric oxygen is provided, it must be reliable.

Flux residues should be easily removed from the solidified metal.

It is quite difficult to fulfill all the requirements, which is why there are many different brands of fluxes in which certain properties are most pronounced.

The operating principle of welding flux is quite simple. The powder is poured onto the surface of the parts. Under the influence of the temperature of the electric arc, it melts, resulting in the formation of gas. This gas protects the surface of the bath from oxygen penetration.

Functions of flux mixtures

Granular flux mixture can be used in manual arc welding. In MMA mode, welding is carried out with consumable coated electrodes. Flux acts as an additional consumable material.

When working in the MIG/MAG mode, flux is supplied to the contact area between the wire and metal, and can also be contained in the wire in the form of powder.

Protection is also used in gas welding, when non-ferrous metals or alloy steels are joined in a propane-oxygen flame.

• Arc stabilization. By choosing the correct flux mixture for a specific task, you can greatly simplify the welding procedure. The powder has a beneficial effect on the electric arc, increasing its stability. An arc is formed between the electrode and the surface to be welded. The approximate gap between the electrodes is about 5 mm. Current surges and difficulties in holding the electrode lead to disruption of stable arc burning, resulting in the formation of defects inside the seam. The presence of flux makes the arc less sensitive to these external factors. This not only makes it easier for beginners, but also allows you to weld with alternating current, and also increases the ability to work in other modes.
• Protective function. The gas cloud formed during melting of the flux should protect against the penetration of atmospheric oxygen into the weld formation zone. It is an impenetrable shell, otherwise an oxide film will form very quickly, because the metals begin to actively interact with oxygen. The welder is required to correctly calculate the dosage and composition of the powder so that the latter can successfully complete the task. It is important to be guided by two principles here. The first is that a finer structure allows for more reliable protection, but at the same time, an excessively high powder density negatively affects the quality of the seam. To calculate the mass of the powder, you need to use special tables. They are given in various reference books and reflect the quantitative composition of the powder, depending on the types of work performed.
• Alloying. The process of forming a weld begins after melting the base metal and the filler. Physical interaction of substances occurs, as a result of which, after crystallization, a seam and a heat-affected zone are formed. The chemical composition of this zone depends on the additive material. At high temperatures, some chemical elements burn out or are deposited in the slag. Without these elements, the metal can no longer have the properties that were taken into account when planning the work. It is possible to restore these properties by introducing substances from outside. Alloying elements are added to flux powders. During the welding process, metal enrichment occurs. Alloying additives prevent the settling of manganese and silicon in the slag masses. In cases where alloying is targeted, a special filler wire is used in parallel.
• Surface formation. When a metal crystallizes, a crystal lattice begins to form. Its structure affects the strength of the material, as well as its appearance. Any impact on the crystal can negatively affect the shape of the weld. That is why after welding work there is often no need to talk about aesthetics. By using fluxes, you can significantly improve the quality of the surface. Some flux elements have forming abilities. An example is the use of “long” powders. They are used when connecting parts of large thickness using electric arc welding at high current. The powder has a high viscosity, as a result of which the hardening process is somewhat delayed, allowing the edges to melt evenly. A crystal lattice with a characteristic structure is formed, which looks neat and aesthetically pleasing. If viscosity is not needed, then “short” powders are used. They freeze almost instantly.

Kinds

A variety of flux powders are subject to distribution into groups. Everything related to welding work using flux powders is regulated by GOST 8713-89. This document is a kind of “handbook” for a professional welder. To understand the general principle of classification of fluxes, you need to know what criteria are used for the division.

Classification by granule type

The appearance of the granules makes it possible to distinguish several types of fluxes, depending on the size of the grains and their appearance. The structure and consistency of flux powder implies the following types:

• granular;
• gaseous;
• powders;
• pasta.

Granules and powders are most often used in surfacing or arc welding. Pastes or gas fluxes are more suitable for gas welding. Depending on the appearance of the granules, fluxes are divided into glassy, ​​pumice-like and cemented.

By composition

The chemical composition of the flux is important in determining its inertness at high temperatures. In addition, do not forget about the alloying function, when the diffusion of individual elements into the base metal occurs.

With all the rich alternatives of various flux compositions, two essential constituent elements can be distinguished: manganese and silica. The remaining elements are additives and alloying elements.

Whether the flux belongs to one of three groups depends on the proportion and variety of additives.

The group of oxide fluxes is used for welding low-alloy fluorine alloys. The powder contains metal oxides and fluorine compounds. In silicon-free fluxes, the proportion of silicon does not exceed 5%.

There are also low-silica powders containing 6-35% silica, and high-silica powders. The gradation was also determined by manganese content. Manganese-free fluxes are considered to be powders containing less than 1% manganese.

High-manganese fluxes contain from 10% to 30% manganese.

Mixed fluxes do not contain many oxides. Salts take their place. Usually the proportion of silica and manganese is not so high, but such powders contain fluorine compounds, which facilitates working with alloy steels.

Salt fluxes are completely free of oxides. But the content of chlorine, fluorine, calcium, sodium and barium salts has been increased to the maximum. Such fluxes are used when working with chemically active metals. It is believed that salt fluxes are universal, as they can be used when welding non-ferrous metals, high-carbon and alloy steels.

An important indicator in the classification is the chemical activity of the flux (Af). This indicator directly depends on the oxidative abilities of the constituent elements. Active fluxes are substances with AF exceeding 0.6. If Af is below 0.1, then such a flux is considered passive.

According to mode of action and purpose

According to this criterion, fluxes differ in the same way as electrodes. They are divided into melting and non-melting powders. Melting fluxes are used in cases where diffusion of additional elements is necessary.

An example would be the formation of a seam surface or an increase in anti-corrosion qualities. Non-consumable fluxes are used when welding non-ferrous metals. It is known that this process is capricious and labor intensive.

The flux here is intended to form certain mechanical properties of the seam.

This type of classification (by purpose) looks the most natural, since the use of flux powders is dictated by certain purposes. Some substances are specifically designed for doping.

There are also universal fluxes that combine all functions. However, the separation of powders for specific metals is relevant.

Well known, for example, is aluminum flux made from sodium, potassium and lithium.

Source: https://regionvtormet.ru/stanki-i-oborudovanie/primenenie-svarochnogo-flyusa-printsip-raboty-klassifikatsiya-i-protsess-polucheniya.html

What is submerged arc welding: advantages of technology, varieties, pros and cons

It has long been known that the processes that occur in the weld pool are negatively affected by air. Nowadays, production uses technologies that can eliminate this factor.

Today, manual arc welding, gas-shielded or automatic submerged arc welding is mainly used. The latter option not only allows you to do the job much faster, but also improves the characteristics of the seam.

What is this method?

Flux Welding is a process in which an arc between the work material and the wire burns under granular powder . When exposed to high temperatures, the granules and electrode begin to melt. As a result, an elastic film forms around the weld pool. It protects the molten metal and the arc from adverse effects, and also prevents air from entering.

During cooling, the flux elements are converted into slag, covering the seam. At the end of welding, the deposited crust can be easily removed from the metal mechanically. The remains of the flux layer are collected and used in the future. You can make connections under a loose blanket using different equipment.

Semi-automatic welding

In this case, the master will have to guide the wire and control the protrusion of the electrode. The welding wire is fed automatically. The welder only needs to select the speed, arc voltage power and electrode angle.

Robotic automatic welding

This technology involves submerged arc welding of smooth surfaces and fillet welds. Moreover, the speed and direction of movement of the electrode is determined by the device. The robotic method makes it possible to achieve a strong connection; in addition, it is characterized by speed and high quality of seam application.

, tandem technology has become very common . In this method, two electrodes are parallel to each other in the same plane. Automatic submerged arc welding in tandem improves the quality of the seam. In addition, this method has a minimum weld pool size and instantaneous arc initiation.

Types of fluxes

They are divided into several groups, depending on the metal:

• High alloy steels;
• Non-ferrous alloys and metals;
• Alloy and carbon steels.

Moreover, depending on the production method, the flux can be ceramic or fused . In the first case, ceramic substances are presented that have alloying qualities and an improved seam, and in the second, they have a pumice-like or glassy structure.

Ceramic flux is created by grinding elements, mixing with extrusion, which helps to achieve a homogeneous mass and better grinding, as well as with liquid glass. A similar process using these mixtures is performed if additional alloying of the weld material is required.

Fused flux is produced by sintering the starting materials, with their further granulation.

In addition, fluxes for gas and electric welding are divided according to their chemical composition into the following categories:

• Saline. They contain only fluorides and chlorides. They are used for flux arc welding of slag remelting and active metals;
• Mixed. They are a combination of salt and oxide mixtures. With the help of such fluxes, alloy steels are welded;
• Oxide. Such mixtures are needed for welding low-alloy and fluoride steels. They contain metal oxides with a small content of fluoride compounds.

As you can see, there are quite a lot of different modifications of this material. But it should be remembered that automatic welding is considered successful if the appropriate flux is used.

Basic modes

The most important modes for automatic flux welding are values ​​such as polarity, type and strength of current , arc voltage, speed and size of the electrode wire.

Not so important, but also significant, are such modes as the angle of inclination of the welded edges and the electrode, the size of its extension, the composition of the flux, the preparation of the metal and the type of welded joint.

When selecting the parameters of submerged arc welding modes, the requirements for the size of the weld and geometric shape, the thickness of the edges and the width of the joint are also taken into account.

Before you start welding, you must first select the wire size. It is necessary to proceed from the welded thickness. Then the size of the welding current is selected, and the wire feed speed is determined.

Most often, solid wire with a size of 1–6 mm is used for submerged arc welding. In this case, the current should not exceed 150-2000 A , and the arc voltage - 22-55 V.

Pros and cons of submerged arc welding

In this technology, welding current is supplied to the wire through a mouthpiece. It is located at a short distance from its edge, usually less than 70 mm. Due to this, the electrode cannot overheat, so high currents are used. All this helps to achieve deep penetration and rapid deposition of metal. Moreover, in this way it is possible to weld thicker metal without separating the edges.

Arc welding, performed automatically using submerged arc welding, ensures the consistency of the shape and size of the seam, and also creates uniformity of its chemical composition . Thus, allowing you to obtain a high-quality connection with high stability of its qualities. This welding method allows you to avoid many defects, for example, the occurrence of areas where elements are not fused and undercuts.

During this welding process, metal spattering does not occur, since the weld pool and arc are protected from air. Thanks to this, there is no need to clean the surface of the material from splashes. Submerged arc welding allows you to save energy and welding materials by approximately 30-40%.

The welder performing the work does not have to use protection for the face and eyes, because the emission of harmful gases is much less than during manual welding.

True, automatic submerged arc welding has not only advantages, but also disadvantages. One of them is the fluidity of the flux and molten metal. That is why you can only cook in the lower position, and the deviation of the seam plane from the horizontal should be 10-15° .

If this rule is neglected, various defects may occur. It is because of this that submerged arc welding is not used to fasten rotary annular joints of pipes whose diameter is less than 150 mm. In addition, this method requires more careful assembly of the edges and the use of certain techniques.

Why is flux welding needed?

Works using flux were able at one time to produce a real revolution in the industrial sector. Initially, this technology was intended for processing low-carbon steel . However, nowadays the powder can be used for almost any material, including refractory metals and steels that are difficult to process.

The metallurgical processes occurring during flux welding have made it possible to use semi-automatic and mechanized equipment for the following work:

• Connecting vertical seams. It is carried out with free or forced formation of the seam. The best adhesion strength is achieved with metals 20-30 mm;
• Welding pipes of different diameters. At first they learned how to connect small-diameter pipes using automatic installations, but with the improvement of processing technology, they were able to master a method that allows them to weld large-sized materials;
• Welding circular seams. The difficulty of such work is that you need to hold the weld pool and try to avoid metal spreading. This kind of flux welding is performed on CNC machines. In some situations, manual welding may be necessary.

The implementation of all these works is regulated according to the welding flow chart . For any violations, heavy penalties are imposed.

Source: https://stanok.guru/metalloobrabotka/svarka/chto-eto-takoe-svarka-pod-flyusom.html

Automatic submerged arc welding: what it is, where and how it is used, features

Every welding master knows how the oxygen environment affects the seam - not in the most positive way. Once in the area of ​​the base metal that has reached the melting point, it oxidizes the solid metal and various alloys.

There are ways to get rid of this problem. You can treat the metal with antioxidant substances, or you can use auxiliary materials, such as fluxes.

Using flux in combination with automatic equipment is the primary method used by welders. Thanks to “this pair” the seams are smooth and resistant to oxidative corrosion.

Flux helps in welding even “difficult” metals, such as non-ferrous or stainless steel. Automatic equipment does not require much effort from the technician, and the flux itself provides protection for the connection.

In this article we will share the technique of automatic submerged arc welding, describe what it is, and also talk about the pros and cons of this method.

general information

The use of auxiliary material does not significantly change the automatic arc welding process. The device creates an electric arc. The arc creates conditions of high thermal stress.

Under the influence of high temperatures, the metal melts, so the parts are connected to each other.

The good thing about using automatic welding machines is that most processes do not require manual effort from the master. There are separate machines for them, each of which is designed for its own action.

Such machines can supply electrode material into the arc zone without intervention from the welder, and even stop when the weld overheats or the weld is completed.

In our case, all these processes remain intact, only flux is added to the surface of the metal being welded.

Where is it used?

Automation is used for various purposes. “Self-sufficient” equipment now has its place in every large production, where parts are manufactured in large batches on conveyors.

Automotive assembly, pipeline structures, beams, shipbuilding and other heavy industries thrive thanks to the operation of automatic welding machines and machines.

They are capable of making tight and reliable joints through automatic flux welding, which are highly valued in these fields.

Role

We learned about automatic welding. What is welding flux?

This is a material that protects both the finished product and the metal itself. Thanks to the flux, the heating of the arc becomes more stable, and the connection is protected from the “harmful” influence of atmospheric gases, especially oxygen.

These substances are usually based on fluorides, chlorides or boric acid in the form of granules, powder or even liquids. Substances in the composition must pass electric current, and this rule is the basis for its production.

"Pros and cons"

Submerged arc welding process

The main advantage of automatic submerged arc welding lies in its name. The master does not have to study the intricacies of welding to apply this method; it is only important to know how to select materials and set up the machine.

And the absence of “human” errors and incorrect movements in the process guarantees an even, correct seam on any metal.

But it will not always be possible to use such surfacing. Its use does not make it possible to make the upper seams - only the lower ones.

Additionally, the parts you “load” into the machine must be fitted with great precision because the machine is set up to deposit metal in one specified area.

If you miss something when joining elements, the result will be defective. Before fixing the element, you need to melt the base of the structure, fixing it on a horizontal plane. It is impossible to connect metal parts by weight.

The main disadvantage of automatic submerged arc welding is its cost. It is not profitable to buy it for household use only. In addition, these devices often take up a lot of space and use a large amount of electricity.

Welding technology

As with any other technique, parts must be processed and prepared before automatic submerged arc welding. Processing each metal is a separate story, but there are general rules for all.

First, the elements are cleaned of residual dust and dirt and examined for corrosion, deformation and irregularities. Then the metal surface is treated with a grinding machine or a simple metal brush with coarse teeth.

And only after these stages can the process itself begin.

Since welding will be performed automatically, you do not need to heat the arc, monitor the direction of the electrode, or control the speed at which the wire will be fed.

You just need to select the settings and welding mode and correctly load the flux material and parts.

For such installations, there are different types of filler wire. Its material should usually match the material from which the elements being processed are made. The spool of wire is loaded into the recess of the mechanism that will feed it.

The same goes for flux. It is poured (or poured) into a tank from which it will be supplied to the connection. Its amount is directly proportional to the thickness of the metal: if the parts are wide, then a lot of flux is needed.

Conclusion

At high temperatures, flux melts, just like metal. However, its melting will not affect the characteristics of the seam. The only thing it can do is improve them by providing resistance to oxygen and, as a result, oxidation.

However, it is important to remove any remaining substance so that its acid does not corrode the metal. You can use the remainder of the loaded substance again.

Now you know more about submerged arc welding. It is used not only in automatic production plants, but also for manual or semi-automatic welding.

However, each of them has its own characteristics, rules and precautions. We will talk about this in other articles on our website. And in the comments below you can share your knowledge on this topic. Good luck!

Source: https://prosvarku.info/tehnika-svarki/avtomaticheskaya-svarka-pod-flyusom

Types and functions of welding fluxes

When carrying out thermal and mechanical welding, high-quality joining of metals is often ensured by welding fluxes. They have been used for a long time.

The composition, appearance, and capabilities are constantly being improved as new scientific and technical information becomes available. There are many types of flux welding materials. Having an idea about everyone, you can wisely choose the composition for a specific situation.

Classification

Fluxes are a large group of multifunctional mixtures. They differ in a number of characteristics that form the basis of the classification. Classes are conditional.

According to the method of production, compositions are divided into mixtures obtained by fusion, mechanical mixing and gluing. The latter compositions are called ceramic.

Welding fluxes are transparent, similar to glass, and porous, opaque, similar to pumice. For obvious reasons, the density of the porous composition is less than that of the glassy one. Melting is carried out in furnaces at temperatures reaching 1500 °C.

Inorganic substances and their mixtures are subjected to fusion. Most often used:

• silicon oxides (silica);
• samples of manganese ores;
• fluorite (fluorspar);
• magnesium carbonate (caustic magnesite).

The melts are poured into the solution. After hardening, this welding flux forms granules. Hydrophilic substances that tend to absorb water are granulated dry according to a separate technological scheme.

Bonded welding fluxes, similar to ceramics, are used widely, much more often than mechanical powders. Ceramics does not react to rust residues, scale in the working area, or the presence of traces of water there. If the ceramic mixture is added to the vitreous mixture, you can get a perfect seam even on uncleaned metal.

Fluxes have different chemical natures. They consist of oxides, salts, mixtures of oxides and salts.

Designed for various metals and alloys

Flux for welding low-alloy steel is classified as oxide. Depending on the brand, it contains from 5% to 35% silicon oxide (silica).

The second component with a fixed mass fraction is manganese oxide. Its content varies from 1% to 30%. In practice, different combinations are used.

If the manganese oxide content in the welding flux is low, then use welding wire with a high manganese content. If there is a high content of manganese oxide in the flux, wire without alloying components is used.

Flux for active metals consists of a mixture of halides: fluorides, chlorides of calcium, sodium, barium, and other alkali and alkaline earth elements.

For high-alloy steels, mixed-type welding fluxes are used. They contain salts and oxides. The mass fraction of silica can be 15%, manganese oxide - from 1% to 9%, and calcium fluoride - up to 30%.

Activity

An important characteristic of flux composites is the conventional unit Af - the activity of the welding flux. Its values ​​fall within the range from 1 to 10. The higher the number, the more active the additive is. Fluxes with high activity are characterized by an indicator value from 0.6 to 1.

When flux components interact with slag, chemical displacement of some elements by others, mechanical mixing, or two processes simultaneously occur.

The intensity of flux penetration into the welding zone depends on the welding mode and flux activity. With a skillful combination of parameters and the correct selection of all materials, the task is accomplished.

Functions of flux additives

Most metals are highly reactive, so they are covered with a layer of oxides. The oxygen content in the air (21%) is quite enough for the oxidation reaction.

When working with metals, an oxide film inevitably gets into the contact area. Even if you removed it the day before using some method, it will form again very quickly.

Oxidation reactions occur especially easily on aluminum surfaces. It is almost impossible to weld them using conventional methods. It is necessary to use fluxes and an inert gas environment.

Oxides entering the weld pool disrupt the process of weld formation. Flux components can prevent metal contact with oxygen and remove a layer of oxidation products. The resulting cloud of gases reduces the consumption of the electrode and prevents splashing of the welding mass.

For high-quality welding you need a constant arc. Gases formed from fluxes stabilize the arc combustion process.

https://www.youtube.com/watch?v=vM06YYQQYT8

The weld seam is formed under normal conditions without defects. Flux components interact with the molten metals, improving the properties and external surface of the joint.

The choice of flux is determined by the composition of the metal and welding conditions in each production situation.

For gas welding

Some grades of thin sheet steel, tool steel alloys, and non-ferrous metals are welded in a gas atmosphere. Welding fluxes in the form of pastes, powders or gas in this process contribute:

• directly into the weld pool;
• on the welded rod;
• on the edges of the metal.

Gaseous fluxes for gas welding (for example BM-1) are supplied to the working area in certain portions using a flow meter. Paste-like additives are applied to the joint. Powders surrounded by gases are more difficult to use. They are evenly introduced into the melt, avoiding being blown up by the gas flow.

For automatic welding

Many metals are welded using automatic equipment. Select the appropriate electrodes, set the mode, select welding fluxes and solder.

The flux additive is placed on the working surface in a layer up to 80 mm thick and up to 100 mm wide. The molten mass consists of half metal, and the rest is flux. Excess flux is automatically sucked off and then reused. Typically, a silicate additive is used in a mixture with oxides of calcium, magnesium, and aluminum.

The welding flux marked AN 348a has proven itself well. It helps stabilize the arc and reduce the release of toxic gaseous products.

AN series fluxes have high electrical conductivity due to the presence of titanium oxide in them. The abbreviation AN indicates that the composition was developed at the Institute of the Academy of Sciences. There is marking based on the chemical composition of fluxes, but in practice it is rarely used.

When forging

The oldest type of welding is forging. Calling this process welding may be a stretch. However, the term “forge welding” refers specifically to the joining of two metals by forging. It is performed manually or using equipment. Forging usually involves types of steel alloys with low carbon content.

Flux for forge welding almost always contains potassium iron sulfide as a base. Its mass fraction is different, ranging from 1 part by weight to 27 parts by weight.

Other components may be borax, boric acid, sodium chloride. Before forging, the mixture is poured onto a metal billet brought to a temperature of 1000 °C.

Flux, together with scale, turns into a liquid mass of slag, envelops the working area, and protects it from further oxidation.

A competent choice of flux and welding mode guarantees the formation of a high-quality weld.

Source: https://svaring.com/welding/prinadlezhnosti/fljusy-svarochnye

Flux for welding: purpose, types of welding, flux composition, rules of use, GOST requirements, pros and cons of use

The quality of the weld is determined not only by the craftsman’s ability to properly organize the arc, but also by the special protection of the working area from external influences.

The main enemy on the way to creating a strong and durable metal connection is the natural air environment. Isolation of the seam from oxygen is provided by welding flux, but this is not its only task.

Different configurations of the composition of this additive with a combination of a protective gas environment make it possible to control the parameters of the seam joint in different ways.

Purpose of flux

A welding consumable of this type is directed into the combustion zone and, depending on the characteristics of its melt, has a protective and modifying effect on the area where the seam is formed. In particular, the material can perform the following functions:

• Creation of slag and gas insulation for the weld pool.
• Endowment of a welded joint with certain technical and physical properties.
• Maintaining arc stability.
• Transfer of electrode metal (or wire melt) to the welding zone.
• Elimination of unwanted impurities in the slag layer.

If we talk about the compatibility of different fluxes for welding with metals, the most common brands have the following purposes:

• FC-9 – steel carbon alloys with low alloying.
• AN-18 – high alloy steel alloys.
• AN-47 – low- and medium-alloy steels characterized by high strength properties.
• AN-60 – low alloy steel used in pipelines.
• FC-7 - used when welding low-carbon steel at high current.
• FC-17 – face-centered high-temperature iron.
• FC-19 – alloys with a high chromium content.
• FC-22 - used to perform fillet weld joints when working with alloy carbon steels.
• 48-OF-6 - used in welding techniques with the connection of high-alloy electrode wire.

The flux itself, as a rule, is produced in the form of granular powder with a fraction of about 0.2–4 mm. But the content and origin of a given product can be very different and not always uniform. In this regard, the following types of flux for welding are distinguished:

• Oxide. The majority of the content is made up of metal oxides and approximately 10% is the share of fluoride elements. This flux is used to work with low-alloy and fluoride steel alloys. Also, depending on the content, oxide flux compositions are divided into silicon-free, low-silicon and high-silicon.
• Salt oxide. Such powders are also called mixed, since the filling can be equally formed by oxides and salt compounds. This flux is used for processing alloy steel.
• Saline. The presence of oxides is completely excluded, and the basis of the composition is formed by fluorides and chlorides. The intended purpose of salt flux is electroslag remelting and welding of active metals.

Flux manufacturing technology

During the manufacturing process, the flux base (charge) is subjected to several processing procedures, including smelting, granulation, molding and quality testing. Before the production process, the raw materials of the charge are segmented into small, medium and large. Each batch undergoes thorough washing and drying, since the purity and accuracy of the parameters of the future flux are maintained from the very beginning.

Then weighing, dosing and mixing with other technological components are performed. Melting and granulation of flux for welding is carried out using special equipment - gas-flame or electric arc furnaces, pools for pouring cold water and metal trays are used. At the final stages of processing, drying and sifting are performed.

The flux that has passed the inspection is packaged in special bags or boxes with fire-resistant properties.

Regulatory requirements affect several areas for assessing the quality of flux, and also regulate safety rules when handling the material and methods for testing it. As for the main parameters, the following requirements apply to them:

• Grains whose size exceeds 1.6 mm are excluded from the flux powder. The percentage of their content should not be more than 3% of the total mass.
• It is allowed to produce flux with a fraction of up to 0.25 mm, if this condition was initially agreed upon with the consumer.
• Also, by agreement with the consumer, it is permissible to produce material with a grain fraction from 0.35 to 2.8 mm, but only in relation to the AN-348-A grade.
• The humidity of fluxes, depending on the brand, should not exceed a coefficient of 0.05 to 0.1%.

As for safety requirements, personal protection measures are the main subject of GOST regulation. Submerged arc welding must be carried out in accordance with fire safety measures. The concentration of the flux powder used, which by default is considered chemically hazardous and industrially hazardous, must be separately controlled.

Fused and unfused flux

melted powder is mainly formed by slag-forming components. They are produced by fusing the constituent elements, including quartz sand, manganese ore and chalk. By mixing them in certain proportions followed by melting in furnaces, it is possible to obtain a seam modifier with a certain set of characteristics.

Submerged arc welding produced by a non-fused method is more functional. This is a mixture of granular and powder materials, which, in addition to the slag-forming base, also include alloying elements and deoxidizers.

The absence of a melting operation makes it possible to introduce metal dust and ferroalloys into the flux, which will open up the possibility of improving compounds.

Types of submerged arc welding

Using flux, both manual and automatic welding can be performed - the fundamental difference will depend on the equipment chosen. Electric arc welding is performed in self-regulating mode or with the support of automatic voltage control. It is optimal to use inverter units supplemented with wire feed drums.

Welding with flux without gas is also common, which by default acts as a protective medium from oxygen and nitrogen. What is good about technology that eliminates this barrier to negative impact factors? Firstly, provided that a suitable flux is selected, it will be able to perform the entire list of protective and auxiliary tasks in relation to the seam being formed. Secondly, the absence of a gaseous environment facilitates the organization of the process itself.

There is no need to prepare a cylinder with an argon-carbon dioxide mixture, and also to protect the welding area from excessive thermal effects when using a torch.

Flux application technique

After igniting the arc, the operator must maintain it between the end of the electrode and the workpiece under the flux layer. The powder is poured in a layer of 55-60 mm, after which the arc should be literally drowned in this mass until it melts. With an average flux weight, its static pressure on the metal can be about 8-9 g/cm2. This value is sufficient to eliminate unwanted mechanical effects on the weld pool.

When using wire for welding with flux, you can achieve minimal melt spatter. This condition is met by ensuring stable contact of the melt zone with the melting wire and flux, as well as by regulating the current strength. Gas protection is also not required in this case, but power control will be especially important.

As a rule, a combination of wire and flux is used when welding with high-density current, therefore the machine must be selected taking into account maintaining a constant speed of direction of the electrode thread.

Advantages of using flux

The use of flux, of course, has the best effect on the formation of the seam, since the negative factors of the work process in open air conditions are minimized.

The obvious benefits include reduced defects in the joint area, minimized spatter and more efficient arc control with full automatic control capabilities. What is also very important is that the submerged arc welding area is always visible to the operator.

This allows you to make timely adjustments to the process if necessary, and in some cases even do without a special mask.

Disadvantages of using flux

The weaknesses of this technology are determined by higher requirements for equipment, since more power is required to effectively melt the flux.

Today, special modifications of machines for argon arc welding in a flux environment are produced, which have special equipment for its preparation and supply. It is logical that such models cost 15-20% more. Another disadvantage is associated with the increase in the melt zone.

Although it can be controlled within certain limits, it is problematic to spot-process small elements under such conditions.

Welding fluxes for aluminum, steel, stainless steel, flux brands

To optimize the seam formation process, a special welding flux is required. The main task of this participant in the welding process is to protect the weld zone from the external environment. In addition, welding flux facilitates the process of separating slag from the molten seam, optimizes the reduction of oxides and guarantees the production of surfacing of the required chemical purity.

Moreover, each welding technology is focused on the use of “its own” flux. And in this article we will describe the main types of fluxes, classifying these substances according to the type of welding technology.

Flux brands for electric arc welding

Fluxes for welding metals using the electric arc method are classified according to three criteria:

• According to the chemical composition.
• According to the degree of activity of the flux components.
• According to the type of metals connected during welding.

Based on the first characteristic - chemical composition - fluxes are divided into salt, oxide and mixed (salt oxide) varieties. Salt fluxes are based on iron fluorides and chlorides and some oxides of alloying materials. Oxide fluxes are based on oxides of manganese, silicon, titanium and other materials. Mixed materials contain up to 30 percent salts (fluorides and chlorides) and at least 15 percent silicon oxides.

Based on the degree of activity of the components, fluxes are divided into four groups: passive, low-active, active and highly active. Moreover, the activity of the components is indicated in the specification for the flux and measured on a special scale: from 0 (passive) to 1 (highly active).

Based on the type of metals being joined, fluxes are divided into four groups:

Compositions for low carbon steels . This category includes any flux for welding structural steel (with an alloying additive content of no more than one percent of the total mass).

Moreover, the basis of the flux composition is formed from silicon oxide, to which manganese oxide is mixed. The mass fraction of the last component (manganese oxide) depends on the manganese content in the welding wire.

That is, the more manganese in the filler material, the lower the content of its oxide in the flux. The chemical activity of the flux components, in this case, is high (up to 0.9).

Compositions for low alloy steels. Compositions for steels containing alloying components up to 5-7 percent are classified as active fluxes (up to 0.6). The reduced chemical activity of the components prevents the oxidation of alloying additives in the welding wire. In terms of their chemical composition, such fluxes tend to be of the oxide type (low content of silicon oxide, low content of manganese oxide and high content of CaF2).

Compositions for high-alloy steels. A typical example of such compositions is flux for welding stainless steel - an almost passive salt-type composition (with a high fluoride content and a minimal silicon oxide content).

Such steels contain a large volume of alloying additives (up to 25 percent of the total mass), so the chemical activity of the flux should tend to zero.

Moreover, the content of metal oxides in fluxes for high-alloy steels should be minimal, since all alloying components are already contained in the welding wire.

Compositions for active metals. These compositions are of the passive, salt type. oxides in such fluxes are simply unacceptable. After all, oxygen is the main catalyst for the formation of an oxide film that covers any part of the active metal. But such a flux contains at least 80 percent of metal salts (chlorides and fluorides).

In addition, electric arc fluxes are also classified according to production methods, dividing the compositions into:

• Melted compositions are made from materials softened in an oven.
• Ceramic compositions - made from a mixture based on a binder (liquid glass).

Fluxes for electroslag welding

Electroslag technology involves the use of completely different types of flux. After all, such a protector should not just seal the welding zone. Electroslag fluxes must conduct electric current and must have high viscosity, which prevents the penetration of substances into the joint zone.

Therefore, such fluxes are saturated with a large amount of manganese oxides, a certain amount of silicon oxide and a certain proportion of fluorides. A typical example of these compositions is any flux paste for welding, applied directly to the joint area. Moreover, the consumption of such paste is an order of magnitude greater than the volume of flux used in the electric arc welding process.

Moreover, according to their chemical composition, such fluxes are divided into: high-silicon and low-silicon; manganese and manganese-free; fluoride and containing a minimum of fluoride compounds. According to the degree of flux viscosity, these compositions are divided into: viscous, low-flow and fluid varieties.

Fluxes for gas welding

Gas shielded welding involves the use of a special flux. The basis of the protector, in this case, is an inert gas (most often argon or helium). However, an option is possible using carbon dioxide, which protects the welding zone and reduces the oxidation of the base and filler materials.

Gaseous flux is supplied to the welding zone under pressure from a special nozzle located under the infusible electrode. Another option is feeding from a nozzle, which has a built-in fitting for the filler wire transport system.

Therefore, almost all fluxes for automatic welding are gaseous.

According to the chemical composition, such fluxes can be divided into the following varieties: argon (the basis of the flux is technically pure argon), helium-argon (up to 30 percent helium in the composition), multicomponent (in addition to argon and helium, nitrogen, oxygen and other gases are also found in the flux ), carbon dioxide (flux consists of carbon dioxide).

The choice of a specific option depends on the depth of the weld, the type of electrode, filler wire and the type of base metal. Moreover, technically pure argon is suitable in any case. The helium-argon mixture has even better characteristics, but due to the high cost of helium, it is not often used. Carbon dioxide fluxes are mainly used in conjunction with graphite electrodes, which heat the weld pool up to 3500 degrees Celsius.

Moreover, it should be remembered that the supply of flux to the weld pool zone is interrupted only after the weld has cooled below a certain temperature. For example, a flux for welding aluminum - argon or a helium-argon mixture - must be “blown” into the seam until the metal cools to 400 degrees Celsius. Therefore, the costs of gaseous flux are simply incomparable with the costs of solid protectors of the weld pool.

Source: https://steelguide.ru/svarka/svarochnye-materialy/flyusy-dlya-avtomaticheskoj-svarki.html