I use welding rods every day. Do you know what function the flux coating serves?

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During the welding process, the flux coating undergoes complex metallurgical reactions as well as physical and chemical changes. It essentially overcomes the problems that occur when using bare electrodes. Therefore, the flux coating is also one of the main factors determining the quality of the weld metal. Welding rod coating: It refers to a coating layer made up of fine granular materials with different physical and chemical properties, which is evenly applied over the surface of the welding core through bonding. The function of the flux coating on welding electrodes is to form a slag during the welding process that possesses appropriate physico-chemical properties such as melting point, viscosity, density, and alkalinity. This ensures stable arc combustion, facilitates the transfer of molten metal, creates an atmosphere around the arc zone and weld pool to protect the welding area, and ultimately results in good weld formation and performance. It is also possible to meet the requirements regarding the performance of the weld metal or to improve the deposition efficiency by adding deoxidizers, alloying elements, or a certain amount of iron powder to the flux. Principles of shielded metal arc welding: 1. Flux 2. Welding core 3. Protective gas 4. Arc 5. Molten pool 6. Base material 7. Weld seam 8. Slag 9. Molten slag 10. Droplets. The various raw materials can be classified according to their function in the electrode flux as follows: (1) Arc stabilizers, whose main role is to facilitate arc initiation and maintain a stable arc during welding. The raw materials used as arc-stabilizing agents are mainly substances containing a certain amount of easily ionizable elements with low ionization potentials, such as feldspar, water glass, rutile, titanium dioxide, marble, mica, ilmenite, and reduced ilmenite. (2) Gas generant: It decomposes to produce gases under the high temperature of the arc, creating a protective atmosphere that shields the arc and the metal in the molten pool from the intrusion of oxygen and nitrogen from the surrounding air. Common gas generators include carbonates (such as marble, dolomite, trona, barium carbonate, etc.) and organic substances (such as wood powder, starch, cellulose, resins, etc.). (3) Deoxidizers (also known as reducing agents) reduce the oxygen content in weld metal and improve its properties through chemical metallurgical reactions during the welding process. Deoxidizers mainly consist of ferroalloys containing elements with high oxygen affinity, as well as their metal powders; common deoxidizers include ferromanganese, ferrosilicon, ferrotitanium, ferroaluminum, and silico-calcium alloys. (4) Plasticizers: Their main function is to improve the plasticity, elasticity, and flowability of the coating on the electrode during the coating process, thereby enhancing the quality of this coating and ensuring that the surface of the electrode coating remains smooth without cracks. Materials with certain elasticity, slipperiness, or the ability to expand when soaked in water are usually chosen, such as mica, white clay, titanium dioxide, talc, solid water glass, cellulose, etc. (5) Alloying agents are used to compensate for the loss of alloying elements during welding and to supply these elements to the weld, thereby ensuring the chemical composition and properties of the weld metal. Various ferroalloys (such as ferromanganese, ferrosilicon, ferrochrome, ferroalloy steel, ferrovanadium, ferroniobium, ferroboron, rare earth ferrosilicon, etc.) or pure metals (such as metallic manganese, metallic chromium, nickel powder, tungsten powder, etc.) can be used as needed. (6) Flux: During welding, it forms a slag with certain physical and chemical properties, which protects the welding droplets and molten pool metal while improving the formation of the weld. Raw materials used as flux include marble, fluorite, dolomite, magnesite, feldspar, kaolin, mica, quartz, rutile, titanium dioxide, ilmenite, etc. (7) Binder: It ensures that the coating material adheres firmly to the welding core, and gives the electrode coating a certain degree of strength after it is dried. It has no harmful effect on the molten pool and weld metal during the welding metallurgy process. Common binders are water glass (potassium, sodium, and their mixed water glasses) as well as phenolic resins, gums, etc.