What is flux in welding

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: types, where and how they are used, classes and their characteristics, selection rules

Welding fluxes: what they are and how to use them. This interests many beginners in the brewing craft. In this review, we will consider what they are, their mechanism of action, and their scope of application.

During the cooking process, chemical activity increases directly on the cooking zone. This applies to both arc and gas welding. Therefore, the metal composition quickly undergoes oxidation.

The cooking wire loses particles of material, which entails a decrease in melting. The welder is forced to weld the elements of the product for a longer time. Because of this, foreign, harmful substances accumulate in the cooking bath.

To avoid such problems, professional welders use welding flux. This is a special material that ensures uninterrupted arc burning. Helps remove excess dirt. What does he look like.

Basically, these are loose granules of small cross-section. Sold in bags of various sizes up to 25 kg. Sometimes materials come in other variations. We describe this in detail in the next part of the text. But first let’s look at the mechanism of their operation.

Mechanism of operation

To understand the principle of operation, you should study what a regular cooking area is made of.

1. The area of ​​the arc column with an internal temperature of 5 thousand.
2. The gas bubble region appears due to the strong evaporation of atoms of materials in the oxygen-containing layer.
3. Area with melted slag. They are located on top of the gaseous cavity.
4. Melted metal is at the bottom.
5. A crust of domesi, which creates a dense edge to the cooking zone.
6. In addition to the listed areas, the welding wire is also important. It also affects the chemical activity of substances.

This explains what the cooking area is made of. Let's start looking at flux. When using the device, the top of the part is heavily oxidized. Because of this, a crust of slag appears.

This can be avoided if an inert material is introduced into the cooking area, which quickly melts. This material is cooking flux. It will protect the part from acidification and promote the formation of a good seam.

To make the most of them, follow the rules.

1. The material should regulate the speed of cooking, not make it slower.
2. It should not come into contact with the surface of objects or the welding wire.
3. The gas bubble should be protected from the external environment during operation.

If all requirements are met, the flux residue can be easily removed after cooking is completed. Half of the removed material can be used again, having previously cleaned it.

These tasks are not easy to complete. Flux varies in composition and how it is added to the welding zone. Find out what metals you use in your work, what type of cooking you use.

Classes

To classify them, we will divide them into subcategories.

• Appearance. The review previously stated that the material is in the form of granules, but sometimes manufacturers sell crystallized, paste and gaseous forms. It all depends on the type of work. For electric cooking, granular or powdered material is often used. For gas cooking, use a paste form or gaseous flux.
• Compound. Flux fillings vary greatly. They are made up of a large number of components. But the main ones are silica and manganese. Detailed content can be found on the Internet or studied on packaging. The flux that you will use should not lose its chemical properties during cooking. At high temperatures too. This is the main condition for good quality material.
• Purpose. You should consider what metals you work with and what type of welding you use. For example, using flux with alloyed wire will give good results. Improves the elasticity of the metal. There are universal fluxes. But we recommend using them when welding non-ferrous metals. When cooking steel, select your flux more carefully.

On a larger scale, fluxes are divided into meltable and non-meltable. Those that are melted are effective. If necessary, perform surfacing.

Non-melting ones improve the physical properties of the welding joint made. Because of this, they are constantly used with high-carbon steels and non-ferrous metals. They do not cook well without flux.

Using Flux

When welding steel by hand, flux is applied to the top with a thickness of approximately 0.5 centimeters. You should not skimp on the amount of material used.

A small thickness can cause poor welding of the metal, which can lead to the formation of cracking. Flux is gradually added during cooking to those places where the electrical conductor moves.

When cooking semi-automatically or automatically, the flux is used as follows. The working material is added through a special tube, followed by the addition of a welding wire placed near it.

During cooking, unused material is removed pneumatically. The slag crust is removed from the top of the seam.

The beneficial effect that flux has.

1. There is no loss of metal in the area of ​​the weld and its area. This creates a good result of the work done.
2. The arc is much more stable.
3. The efficiency of the supply voltage increases as a result of reduced energy losses that go into heating the part.
4. The welder has good working conditions, since the flux shields the greatest flow of arc fire.

But there are also limitations. If you do not have the opportunity to preview the welding zone of the metal that you plan to use in your work, we do not recommend using flux.

Their use involves preparatory work. In addition, the material is expensive and is consumed in the same volume as wire. Without preliminary preparation, the use of flux may be impractical.

But welding work using it is quite effective. When cooking, the metal does not splash. The cooking wire will last longer. The productivity of the craftsman will increase.

Using it, it is possible to work at high voltages without danger. In this case, the seam will be just as stable.

Summary

Cooking fluxes are an excellent option to optimize your own work and improve its quality. Its use involves preparatory work.

And the price may not seem low. We believe that successful work completely overshadows the minor disadvantages.

Apply it in your work and share your opinion in the comments. Your thoughts will be useful to all welding professionals.

Source: https://prosvarku.info/rashodnye-materialy/svarochnye-flyusy

Welding fluxes – Osvarke.Net

Welding fluxes are granular powder supplied to the welding zone, where, during melting, it performs the functions of protecting the weld pool and arc from exposure to air, stabilizing the combustion of the weld arc, high-quality formation of the weld, alloying the weld metal with the necessary components, etc. Fluxes are used for automatic and semi-automatic welding submerged arc, as well as for electroslag welding.

Welding fluxes used for gas welding and carbon electrode welding have a slightly different purpose. Fluxes of this classification are designed to remove solid non-metallic inclusions from the weld and protect the edges of welded parts and additives from oxidation.

Classification of welding fluxes

The main characteristics by which fluxes are divided are production method, chemical composition and intended purpose. Depending on the production method, there are fused and unfused fluxes.

Fused fluxes are produced by fusing all of its components and then crushing them into small grains of the required granulation. Fused fluxes can be glassy or pumice-like. The first have the form of transparent grains of different shades, which are obtained by pouring hot (1200°C) liquid flux into a tank of water.

Pumice fluxes are grains of foamy material obtained by pouring liquid flux heated to a temperature of 1600°C into a tank of water. When water vapor rises, a pumice-like flux is created. The grain size of penzoic flux is from 0.2 to 4 mm. When using such fluxes, better formation of the weld is observed.

Glassy fluxes provide more reliable protection for the welding zone.

Fused fluxes are cheaper to produce and provide reliable weld formation, arc protection, and easy slag separation. Fluxes should be stored in dry places in paper bags.

Unmelted flux is produced by mixing small granules of the components included in the flux mechanically without fusion. The most commonly used are ceramic fluxes.

Ceramic flux is obtained by mixing the components with liquid glass and then rubbing it through or using special granulators. After crushing, the flux is allowed to dry at a temperature of 150-200°C and fried at a temperature of 350°C.

Ceramic fluxes tend to absorb moisture, so they are stored in sealed packages and rigid containers due to the low strength of the granules. Their advantages are considered to be good ability to alloy the weld metal, low sensitivity to rust and scale.

Based on their chemical composition, oxide, salt and salt oxide fluxes are distinguished. Oxide fluxes consist of metal oxides with the addition of fluoride compounds. It is used for welding carbon and low-alloy steels. Salt fluxes consist of fluoride and chloride metal salts. These fluxes are used for welding active metals. Salt oxide fluxes, as you can understand, consist of metal oxides and fluorides. Designed for welding alloy steels of various classes.

Depending on their purpose, welding fluxes are divided into several groups:

• for arc welding of carbon and low-alloy steels;
• for arc welding of alloy steels;
• for electroslag welding;
• for welding non-ferrous metals and alloys;
• fluxes for surfacing.

Fluxes for welding steels

The following brands of domestically produced fluxes are intended for welding carbon and low-alloy steels: AN-348A, AN-348V, OSTS-45, AN-60, FC-6, ANK-35, AN-20S, AN-37P and others. The indices following the electrode brand mean: M - small, S - glassy, ​​P - pumice-like.

For arc welding of medium- and high-alloy steels, the following brands of domestically produced fluxes are used: AN-20P, AN-20S, AN-26, AV-4, AV-5, AN-30, OF-6, OF-10, FC-17 , FCK-S and others.

Electroslag welding is performed using flux brands: AN-8, AN-22, ANF-1, ANF-6, ANF-7, ANF-14U, AN-25, S-1.

• Mechanized welding of copper and its alloys is performed using submerged arc grades: AN-348-A, OSTS-45, AN-20S, AN-26S, AN-M1, AN-M13, AN-M15, AN-M10.
• Fluxes for mechanized welding of aluminum and its alloys: ZHA-64, ZHA-64A.
• Fluxes for electroslag welding of aluminum and its alloys: AN-301, AN-302, AN-304.
• Fluxes for arc welding of titanium and its alloys: ANT-1, ANT-3, ANT-7, ANT-23A.
• For electroslag welding of titanium and alloys: ANT-2, ANT-4, ANT-6.

Marko fluxes are used for surfacing: AN-70, AN-28, AN-20P and others.

Fluxes for gas welding

Separately, we can distinguish fluxes for gas welding and carbon electrode, which should dissolve oxides and non-metallic inclusions in the metal of the weld pool. When using these fluxes, low-melting mixtures raise the slag to the top of the weld pool. Fluxes are used in the form of powders or pastes. Welding of low-carbon steels with such fluxes is not performed due to the tendency to form low-melting iron oxides on the surface of the weld.

Using fluxes you can weld cast iron, non-ferrous metals, and high-alloy steels. Fluxes for gas welding, as well as for carbon electrode welding, must meet the following requirements:

• the flux must have a melting point below the base metal;
• the flux must have sufficient fluidity;
• flux should not contribute to corrosion of seams;
• the flux must deoxidize the oxides and transform them into fusible compounds or remove them from the seam;
• the formed slag should protect the weld pool from air;
• the slag should be well separated from the surface of the welded joint after welding;
• The density of the flux should be lower than the density of the metal so that the slag floats to the surface well and does not remain in the metal.

Flux is selected depending on the type and properties of the metal being welded. Basic and acidic oxides can form in the weld pool. If basic oxides are formed, then acidic fluxes are used and vice versa, if acidic, then basic fluxes are used. In any case, the reaction proceeds according to the following scheme:

basic oxide + acidic oxide = salt

Welding cast iron is accompanied by the formation of acidic oxides SiO2, for the dissolution of which basic oxides K2O Na2O are introduced. The main fluxes used are sodium carbonate Na2CO3, potassium carbonate K2CO3 and borax Na2B4O7.

When welding copper and brass, basic oxides (Cu2O, ZnO, FeO and others) are formed, so acidic fluxes (boron compounds) are used to dissolve them.

Source: http://osvarke.net/materialy/flyus/

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

Submerged arc welding: what is it, advantages

Submerged arc welding: what is it, advantages

Arc welding is primarily referred to as a process in which two pieces of metal are welded together using an electric arc. It is formed by a power source, which can be direct or alternating current.

An arc is created between the electrodes and the workpiece. One such type of welding is submerged arc welding (SAW), so named because the arc zone, electrode tip, and cast weld are hidden under a layer of granular fusible flux. This is done to protect against air pollution.

SPF can be performed automatically or manually. Some companies use semi-automatic pistols to do this job. Although SPF can work with full automation, people generally do not choose this option.

What are the advantages of submerged arc welding

The arc welding process produces spatter and sparks. And at the same time creates intense ultraviolet radiation and smoke. In the SPF process, such factors are eliminated, since the molten metal is completely covered with a thick layer of flux, which makes it environmentally friendly.

In addition, the suppression of radiation and smoke makes SPF safer than other types of welding. Operators supervising welding are not required to wear protective clothing, but rather wear normal work clothing.

Since submerged arc welding uses electricity, it does not need to be applied under pressure. Due to the high heat generated during the welding process, this method is well suited for welding thick profiles. Read about how to cook channel bars on the website mmasvarka.ru.

Submerged arc welding is particularly famous for its high rate of metal deposition. Thanks to this property, welding provides deep penetration into the weld. Submerged cored wire welding provides better deposition rates than solid wire.

In addition, the concentration of a huge amount of heat allows you to speed up this process. Speeds up to 5 m/min are achieved. The final weld product, the weld metal, is produced with superior quality in uniformity, toughness, corrosion resistance and durability. In addition, the weld shapes have a cleaner appearance and a smoother surface.

One of the biggest problems in welding processes is weld deformation. This occurs as a result of expansion and contraction of the weld metal and adjacent non-ferrous metals. Because SPF uses higher heat concentrations and faster welding times, it can significantly reduce such disturbances.

This welding process can be used both indoors and outdoors. Even in relatively windy areas, submerged arc welding meets absolutely all welding requirements.

Where is submerged arc welding used?

This process is suitable for welding low alloy steel with low tensile strength. It is widely used in the construction of railways, boilers and equipment used to move soil. Submerged arc welding is also commonly used to make cranes, bridge support beams, and the lowest supports for railroad cars and locomotives.

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

In conclusion, the fusible flux used in SPF remains solid granular throughout the welding process, allowing 50-90% of the flux to be reused.

Source: https://mmasvarka.ru/dugovaya-svarka-pod-flyusom.html

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.

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.

Conclusion

Flux as a consumable material that improves the quality of the welding process facilitates many production and construction activities in this range. But even in domestic conditions, it is often used in the country, in the garage, or simply in repair operations. When choosing this material for your own needs, it is very important not to make mistakes in assessing the quality.

As the same GOST notes, flux for welding should be supplied to the market in thick paper bags from 20 to 50 kg, indicating transport markings. By special order, small packaging can also be issued, but special containers must be provided for this.

Moreover, weighing should be carried out with a maximum error of 1% relative to the total weight of the container.

Source: https://FB.ru/article/418875/flyus-dlya-svarki-naznachenie-vidyi-svarki-sostav-flyusa-pravila-ispolzovaniya-trebovaniya-gost-plyusyi-i-minusyi-primeneniya

What flux is used for welding, the main types of flux mixtures

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://svarkoy.ru/rasxodniki/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.

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