What is welding flux made of

A disadvantage of fused fluxes is that the high temperature used during the manufacture process makes it difficult to add alloys and deoxidizers. The manufacture of bonded fluxes involves combining the dry ingredients, then using a liquid binder such as sodium silicate or potassium silicate to glue the ingredients together.

After the bonded mix is made into pellets, the pellets are baked at a low oven temperature. Once the drying of the pellets is complete, the pellets are broken up by using a sieve to attain the desired particle size. The particles are then packaged for shipping. Submerged Arc Welding SAW is a common welding process that is commonly used in the structural and vessel construction industries. Originally developed by the Linde - Union Carbide Company, it is commonly used in beam, boom, tractor, and multi-head type rigs.

Sub Arc welding requires a continuously-fed tubular or consumable solid electrode and may be fully automatic or semi-automatic. The arc is flat and is maintained between the end of a bare wire electrode and the weld. The electrode is constantly fed into the arc and as it is melted, a layer of granular flux provides a protective cover beneath which the welding occurs. The blanket is created as some of the flux becomes molten. This fusible flux may consist of lime, silica, manganese oxide, calcium fluoride, and other compounds.

In a molten or melted state, the flux becomes conductive. This allows it to supply a constant current between the electrode and the welding work. The remainder of the flux is recovered and reused, unless it has become contaminated. In the automatic version of SAW, the process is performed with a set of rollers driven by a controlled motor to ensure that the wire is fed into the arc at a speed rate that is equivalent to the rate at which the electrode is melted.

The arc length remains constant as a result. The SAW process is usually automated; however, there are semi-automated systems available, too.

Properly performed Sub Arc welding should consistently result in mechanical properties that are at least equal to that of the base metal. Ductility and impact resistance should be good, and bead appearance should be uniform. In automatic submerged arc welding, there are three types of guns that are generally used. These include the side flux delivery gun, the deep groove gun, and the concentrated flux delivery gun.

The concentrated flux delivery gun deposits the flux around the wire. SAW material applications include carbon steels, low alloy steels, stainless steels, nickel-based alloys, and surfacing applications wear-facing, buildup, and corrosion-resistant overlay of steels. SAW is frequently used in heavy structural construction. It is also used in the pressure vessel industry, chemical plants, and shipbuilding. The main function of weld flux is to oxidize the base and filler materials during the welding process.

Weld flux is a substance that is almost inert at average room temperature but can be intensely reducing when exposed to higher temperatures to prevent metal oxide formation.

Flux dissolves the metal surface oxides that facilitate the molten metal wetting and acts as a barrier to oxygen and minimizes oxidation. Fluxes are used to generate a surface for wetting the solder. However, flux can contain bromine and chlorine and can remain corrosive after the soldering process, subsequently causing corrosion to the surface throughout production or operation.

Therefore, testing and cleaning techniques have been developed to ensure that the surface remains noncorrosive after the process. The most common tests are designed to identify the flux residues' corrosive properties under extreme conditions.

During testing, a solder pellet is melted when it comes in contact with the flux over a metal sheet. Afterward, the solder is exposed to various humidity levels.

The corrosion generated is then evaluated visually. The oxide layer takes away the corrosion resistance of the metal. It also affects the strength of the weld. Hence, technicians and engineers look for ways to ensure that oxygen never reaches the weld seam during the welding process. The main condition for a flux to work is that it should be inert to the metals being joined.

In other words, no reaction should occur between the flux and the metals. Hence, the selection of flux material depends on the metals used. In addition to preventing the formation of oxides, weld flux also:. For welding, flux is not used as a separate application. They are almost always present with the electrode. Flux is coated on the electrode with a thickness of 1mm to 3mm. Some electrodes use flux within them in a hollow cavity.

In this case, the electrode covers the flux. In the arc weld landscape, flux-cored electrodes are broadly classified into four different types based on their properties. Rutile electrode coating is made from titanium oxide. They offer excellent arc control and slag control to the welder. Due to these properties, Rutile electrode coating is often known as the most welder-friendly flux types.

The amount of fumes produced from the electrode is also generally low for the Rutile electrode. The wires may be solid or metal cored. Strips may be rolled or sintered. Welding wires vary from 1. The wires for ferritic steels are generally copper coated to increase contact tip life, improve electrical conductivity and extend the shelf life.

Stainless steel and nickel alloy wires are bright drawn and uncoated. The wire is supplied on reels weighing 10 to 50kg and can also be obtained in large pay-off packs weighing up to kg. The strip used for surfacing is supplied in 15 to mm widths but the thickness is a standard 0.

As with the wire, strip is available in a range of coil weights. The functions of the flux are:. Fluxes may be categorised in two ways: by the method of manufacture fused or agglomerated or by its activity neutral, active or alloying.

Within these broad groupings the fluxes may be classified further by their constituents, silica, manganese oxide, calcium fluoride etc. Perhaps the most convenient method of classifying, however, is by reference to the 'basicity index' BI of the flux.

The index is calculated by dividing the sum of the percentages of the basic constituents by the sum of the acid constituents. Calcium, magnesium, sodium, potassium and manganese oxides, calcium carbonate and calcium fluoride are the basic constituents of a flux; silica and alumina the acid constituents.