The quality of the weld is determined not only by the ability of the master to organize the arc correctly, but also by special protection of the working area from external influences. The main enemy on the way to creating a strong and durable metal compound is the natural air environment. The isolation of the weld from oxygen is provided by the flux for welding, but not only this is its task. Various configurations of the composition of this additive with a combination of a protective gas environment allow different control over the parameters of the suture joint.
Flux appointment
A welding consumable of this type is sent to the combustion zone and, depending on the characteristics of its melt, has a protective and modifying effect on the weld formation site. In particular, the material can perform the following functions:
- Creation of slag and gas insulation for a weld pool.
- The endowment of a welded joint with certain technical and physical properties.
- Maintaining arc burning stability.
- Transfer of electrode metal (or wire melt) to the weld zone.
- Elimination of unwanted impurities in the slag layer.
If we talk about the compatibility of different fluxes for welding with metals, then the most common brands have the following purposes:
- FTs-9 - low-alloy steel carbon alloys.
- AN-18 - high alloy steel alloys.
- AN-47 - low and medium alloy steels characterized by high strength indicators.
- AN-60 - low alloy steels used in pipelines.
- FTs-7 - is used for welding low-carbon steel at high current.
- FTs-17 - face-centered high-temperature iron.
- FTs-19 - alloys with a high content of chromium.
- FTs-22 - is used to make angular suture joints in work with alloyed carbon steels.
- 48-OF-6 - is used in welding techniques with the connection of a high-alloy electrode wire.
Flux Compositions
The flux itself, as a rule, is produced in the form of a granular powder with a fraction of the order of 0.2–4 mm. But the content and origin of this product can be very different and not always uniform. In this regard, the following types of flux for welding are distinguished:
- Oxide. Most of the content is made up of metal oxides and about 10% is the share of fluoride elements. This flux is used to work with low alloy and fluorine 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. Such a flux is used for processing alloy steel.
- Saline. The presence of oxides is completely ruled out, and fluorides and chlorides form the basis of the composition. The purpose of salt flux is electroslag remelting and welding of active metals.
Flux Technology
In the manufacturing process, the base for the flux (charge) is subjected to several processing procedures, including smelting, granulation, molding and quality control. The raw materials of the mixture before the production process is segmented into small, medium and large. Each batch is thoroughly washed and dried, since purity and accuracy in the parameters of the future flux are initially supported. Then weighing, dosing and mixing with other technological components. Smelting and granulation of flux for welding is carried out on special equipment - gas-flame or electric-arc furnaces, pools for dousing with cold water and metal pallets are used. In the final stages of the processing, drying with sieving is performed. The passed control flux is packed in special bags or boxes with refractory properties.
GOST requirements for flux
Regulatory requirements affect several areas of flux quality assessment, as well as regulate safety rules for handling material and methods for testing it. As for the main parameters, the following requirements are imposed on them:
- Excluded in flux powder grains whose size exceeds 1.6 mm. The percentage of their content should not be more than 3% of the total mass.
- Production of flux with a fraction of up to 0.25 mm is allowed, if this condition was originally agreed 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 with respect to the AN-348-A brand.
- The moisture content of fluxes, depending on the brand, should not exceed a coefficient of 0.05 to 0.1%.
As for safety requirements, personal protective measures are the main subject of GOST regulation. Submerged arc welding must be carried out in accordance with fire safety measures. Separately, the concentration of the flux powder used, which by default is considered chemically hazardous and industrial harmful, should be monitored.
Fused and non-fused flux
The content of the fused powder is mainly formed by slag-forming components. They are produced as a result of fusion of constituent elements, including quartz sand, manganese ore and chalk. By mixing them in certain proportions, followed by melting in furnaces, you can get a modifier for the weld with a certain set of characteristics. A more functional submerged arc welding is carried out in an unmelted manner. This is a mixture of granular and powder materials, which in addition to the slag-forming base also include alloying elements and deoxidizing agents. The absence of a melting operation makes it possible to introduce metal dust and ferroalloys into the flux composition, which will decipher the possibilities for improving the compounds.
Types of welding under a flux layer
With the use of flux, both manual and automatic welding can be performed - the fundamental difference will depend on the equipment selected. Arc welding is performed in self-regulation mode or with the support of automatic voltage control. It is optimal to use invertor units supplemented with wire reels. Non-gas flux welding is also common, which by default acts as a protective environment against oxygen and nitrogen. What is good technique that eliminates this barrier to negative impact factors? Firstly, subject to the selection of a suitable flux, he will be able to complete the entire list of protective and auxiliary tasks in relation to the weld being formed. Secondly, the absence of a gas medium facilitates the very organization of the process. It is not necessary to prepare a cylinder with an argon-carbon dioxide mixture, as well as to protect the welding zone from excessive heat exposure when using a torch.
Flux Application Technique
After ignition of the arc, the operator must maintain it between the end of the electrode and the workpiece precisely under the flux layer. The powder is poured with a layer of 55-60 mm, after which the arc should literally be drowned in this mass until it melts. With an average weight of the flux, 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 a wire for welding with flux, it is possible to achieve minimum indicators of spraying the melt. This condition is satisfied 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 at high density current, therefore, the machine should be selected taking into account the support of a constant speed of direction of the electrode filament.
The benefits of using flux
The use of flux, of course, affects the formation of the seam in the best way, since the negative factors of the working process in open air are minimized. Among the obvious advantages, it is possible to note the reduction of defects in the connection zone, minimization of spatter and more effective arc control with all the possibilities of automatic regulation. What is also very important, the submerged arc welding section is always visible to the operator. This allows, if necessary, to make timely adjustments to the process, and in some cases even dispense with a special mask.
Disadvantages of using flux
The weaknesses of this technology are caused by higher requirements for equipment, since effective flux melt requires a lot of power. Today, special modifications of devices for argon-arc welding in a flux medium are produced, which have special equipment for its preparation and supply. It is logical that such models are 15-20% more expensive. Another disadvantage is associated with an increase in the melt zone. Although it can be controlled within certain limits, it is problematic to fine-tune small elements in such conditions.
Conclusion
Flux as a consumable that improves the quality of the welding process facilitates many production and construction activities in this spectrum. But even in domestic conditions it is often used in the country, in the garage or just in repair operations. Choosing this material for your own needs, it is very important not to miscalculate in the assessment of quality. As noted by the same GOST, flux for welding should be supplied on the market in dense paper bags from 20 to 50 kg with an indication of the transport marking. By special order it is possible to fill out small packaging, but for this special containers must be provided. Moreover, weighing should be carried out with a maximum error of 1% relative to the total tare.