Flux: a shielding agent between two materials

2021-11-11 08:36:28 By : Ms. Elyn Wheelsky

Understand the importance of flux, which is the main antioxidant used in arc welding.

Flux is a kind of flux that prevents the weld seam from interacting with the surrounding medium (such as air). The reason it is so important is that the base material and filling material interact with the atmosphere and cause the formation of oxides or other unwanted compounds.

During the welding process, the base metal and filler will undergo significant temperature changes in a short period of time. The heated metal may interact with the surrounding air and cause oxidation, thereby forming an oxide layer on the weld and reducing the strength of the weld.

Moreover, not only oxygen will produce infectious welds, but the formation of sulfides and nitrides will also damage the strength of welds.

Related: Friction welding: process, types and advantages

Due to the large amount of nitrogen and other gases in the atmosphere, metals are likely to be affected by inclusions. The oxide layer takes away the corrosion resistance of the metal.

It also affects the strength of the weld. Therefore, technicians and engineers try every means to ensure that oxygen never reaches the weld during the welding process.

The main condition for flux to work is that it is inert to the metal being joined. In other words, there should be no reaction between the flux and the metal.

Therefore, the choice of flux material depends on the metal used. In addition to preventing the formation of oxides, flux can also:

Flux can be used for shielded metal arc welding (SMAW), flux cored arc welding (FCAW) and submerged arc welding (SAW).

For soldering, flux is not used as a separate application. They are almost always present with the electrodes. The flux is applied to the electrode with a thickness of 1mm to 3mm.

Some electrodes use flux in the cavity. In this case, the electrode is covered with flux.

In the field of arc welding, flux-cored electrodes are roughly divided into four different types according to their characteristics.

The rutile electrode coating is made of titanium oxide. They provide excellent arc control and slag control for welders. Because of these characteristics, the rutile electrode coating is often referred to as the most friendly type of flux for welders.

For rutile electrodes, the amount of smoke generated by the electrodes is usually very low. Rutile electrode flux is the first choice for welding misaligned welds.

Alkaline flux is made of calcium carbonate, calcium fluoride, magnesium carbonate and some other shielding compounds. The advantage of using alkaline flux is that it will produce better mechanical properties and a lower level of hydrogen diffusion.

Alkaline flux is the first choice for high-strength steel. However, in terms of operational stability and ex-situ welding, the latitude of the basic flux is much lower.

When using basic flux, the arc is also less predictable.

The cellulose electrode coating uses a mixture of cellulose and other organic compounds. When cellulose is subjected to high temperatures during welding, it decomposes to produce carbon monoxide and hydrogen.

The production of these two gases protects the weld from atmospheric influences. They also provide better weld penetration.

However, the high hydrogen production rate may not be suitable for welding metals with hydrogen-containing characteristics.

The iron oxide coating is a mixture of metal oxides of iron, manganese, and silicon dioxide. Once they are heated, they will produce molten acid slag.

Due to the high amount of oxygen generated, the iron oxide coating is not suitable for welding metals that are easy to contain oxygen. One way to prevent oxidation of the weld is to add a deoxidizer to the weld core.

MIG welding or metal inert gas welding is a welding process in which an electrode gun is used to feed electrodes into the weld. Compared with flux welding, MIG welding does not require flux-coated electrodes because it uses shielding gas to protect the molten pool from external interference.

But the difference does not stop there.

MIG welding equipment is generally more expensive than arc welding setups. Therefore, the initial capital for MIG welding is not just arc welding.

Compared with MIG, flux-cored arc welding equipment is easy to transport. Since there is no need for any system to provide an air jet to the weld, there are fewer components that need to be moved​​.

Compared with flux welding, MIG welding is much easier for beginners. The ease of use stems from the fact that the welder only needs to handle one component at a time. Flux welding usually requires more skilled welders.

MIG welding is not feasible outdoors, because external factors such as wind or rain will significantly reduce the welding strength. Therefore, they are mostly reserved for indoor use.

There is no such limitation for flux welding. They can still operate even under less favorable conditions.

MIG welding can be used to weld thin to medium thickness metals. Flux welding has deep penetration, so it is very effective for thicker metals.

Due to its affordable price and inert chemistry, argon is one of the most popular MIG shielding gases in the industry.

Welding is not just a process of joining metals. Perfect welding is the result of many conscious decisions made by welders after considering all relevant details.

Related: Cold welding: joining metals without heating

Flux is an inevitable part of arc welding, and the choice of flux has a great influence on the final quality of the weld. Welders undergo detailed training to familiarize themselves with different welding practices and the components used for each welding method.

Flux core welding is probably one of the oldest arc welding methods. Nevertheless, it is still one of the most effective and widely used metal joining methods.

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