Control of welding wire work The slag acts as a model to force the metal water or weld to remain in the weld position. Liquid slag must have three balanced physical properties:
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1) The slag must be fluid enough to flow from the livinggossip bottom of the joint up to the top. so as not to form slag when the weld metal hardens.
2) Slag must not be too liquid. until it flows out of the weld surface. will not cover the welds thoroughly Therefore, the surface tension of the liquid slag should be increased.
3) Liquid slag will solidify quickly. To be able to support the metal water from flowing outside the joint
4) Control of Weld-Metal Composition
Advantages of welding with flux-cored welding wire (SMAW) can add alloys to the weld. by adding the desired element to the flux If ferromanganese is added to the flux it will transfer into the weld area. The actual amount of manganese in the weld depends on the manganese intensity and the flux mixture. The flux can add or reduce the elemental content to the weld by the flux mixture.
Control of the ingredients of the weld Three main elements must be considered.
- Mixed elements (Alloying)
- Oxygen removal (Deoxidation)
(6) Alloying: If a weld is required to contain the same element as the wire rod and to ensure that the alloy is not lost to the flux. Therefore, the flux used does not require the addition of elemental mixtures. It can be seen from non-ferrous metal and some stainless steel wires.
Welding wire Low-Carbon Steel , Carbon , Carbon-manganese and Low-alloy Steel wire cores are of the same type. where various elements are added to the flux which is more economical than using alloy wire core
6) Deoxidation (Deoxidation) if the melting pond of steel has a large amount of oxygen. Oxygen will react with carbon. It is carbon monoxide gas and is trapped in the weld in the form of pores as shown in the equation
FeO + C Fe + CO
Carbon monoxide is insoluble in steel. but will separate in the form of wasted carbon gas bubbles. will affect the strength of the weld. Therefore, it is necessary to add a Deoxidized element to the flux.
Deoxidized elements combine with oxygen to form oxides. and float above the weld Overall with Slag Flux cored welding wire for steel Ferro is generally added. Silicon is an oxidant. The oxidizing reaction in the welding melting pond is
2 FeO + Si 2 Fe + SiO
Other metal deoxidants are as follows: Copper welding adds phosphorus or zinc to bind oxygen. It will be added to the wire rod. do not fill through the flux
The use of flux will add elements to improve the quality of the weld. But keep in mind that flux may also introduce harmful elements into the weld.
Hydrogen will make metals brittle and break. The hydrogen in the weld is caused by the moisture in the flux covering the wire and the chemical reaction of the flux is mixed with water. in various quantities which depend on the type of flux There are several methods for measuring hydrogen content in welds. including AWS , JIS , DIN and BS methods etc.
The amount of hydrogen is measured in pstviewer milliliters. per 100 g of weld weight. Welding electrodes with low hydrogen content are wires containing a large amount of calcium.
Other impurities that pass through the welding flux This is usually due to inattention such as oil and grease. May get dirty during storage. unclean things will be absorbed through the flux and sent to the welding smelting pond Therefore, the storage and transportation of welding wires is important to take precautions for high-quality welding wires.
2.1.2 Function of the Slag
An important function of molten slag obtained from flux-clad welding wire. is to cover the weld to prevent contamination from the air and a chemical reaction to reduce the amount of gas in the weld. The main functions of slag enough can be summarized as follows.
- Prevents the weld metal from staining.
- Help draw oxygen and other impurities. out of the weld
- Control weld shape and provide a smooth, even weld line.
2.1.3 Properties of flux-covered materials for SMAW welding
already know the properties of flux covered wire Next, we will talk about the properties of each compound element. The materials used for fluxing include organic materials, ores, chemical compounds, kels, and ferroalloys.
- Cellulose (Cellulose) is a product obtained from wood pulp or residue from paper production. which cellulose when heated by an arc It gives carbon dioxide and hydrogen gas. Which serves to cover the weld and increase the properties of deep penetration as well.
- Calcium Carbonate, found in limestone, calcite, or marble, is an important ingredient of low-hydrogen welding rods. When heated by an arc Calcium carbonate provides a low-hydrogen carbon dioxide to cover the weld. And slag will help the weld to have low levels of oxygen. Welds have good properties.
- Fluorspar (Fluorspar) or fluorite derived from calcium fluorite is used to control the flow of slac and allow gas to escape from the weld. which applies to low hydrogen type electrodes The resulting weld has a low gas content.
- Rutile is a mineral composed of titanium oxides, including rutile and ilmenite. keeps the arc evenly It also helps the slacks to liquefy and harden faster. Consistently detailed welds
- Potassium Compound
Potassium contains potassium feldspar and potassium titanate. Potassium helps ionize and stabilize the arc. It also allows the arcing to occur easily.
- Mixed elements (Ferroalloys) adding elements or Deoxidizing into the weld. It is done in the form of Ferroalloys for elements that are usually originally in the weld, including Ferromanganese and Ferrosilicon, where the two elements are added together. It is used as an oxygen removal element. (Deoxidizing) with high efficiency. and can control the strength of the weld as well
- Sodium silicate – sodium silicate or glass glue. It is a liquid for mixing various ingredients. to stick together to form a flux and then used to cover the wire core
Iron Oxide (Iron Oxide) Iron oxide is in the form of ores such as magnetite and hematite. Iron oxide is mixed into the flux to form slac.
- Iron Powder: Some types of flux cover wires are mixed with different amounts of iron powder. The main purpose of mixing iron powder is to increase the weld fill rate. When the flux melts, the iron powder in the flux also melts, adding it to the weld. Iron powder also influences the weld shape. and the shape of the tip of the wire that is cup-shaped Therefore, the technique of welding “Drag” with iron powder-mixed wires can be used.
Main properties of mixed elements in flux There are approximately 6 to 12 elemental alloys in the flux of each electrode, but only 1 or 2 of the elements are mixed in the flux that predominates other types such as cellulose or rutile. etc.
Flux covered wire rod Influence on the characteristics of metal water feeding from the tip of the wire to the melting pond, such as acid type wire. Or iron oxide, the transmission of metal fuzzy water is finer than other types of welding wires.