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In the field of welding, flux cored arc welding (FCAW-G) plays a significant role and is widely used in heavy manufacturing, construction, shipbuilding, offshore facilities and other industries for the welding of low-carbon steel, low-alloy steel and various alloy materials. The choice of shielding gas is crucial for the welding effect, and the commonly used ones are 100% pure CO₂ or a mixture of 75% - 80% Ar and 20% - 25% CO₂. This article will deeply explore the advantages and disadvantages of these two shielding gases to assist welding practitioners in making informed choices.   Shielding Gas Working Principle: The Invisible Shield in the Welding Area   The core function of the shielding gas is to block the air and prevent oxygen, nitrogen and water vapor from eroding the welding pool and electrode. During the welding process, the shielding gas is ejected from the welding torch nozzle, creating an isolated environment around the electrode to ensure the stable combustion of the arc and the normal solidification of the molten pool. Both CO₂ and Ar/CO₂ mixtures can effectively fulfill this responsibility and also participate in the construction of the arc plasma region, affecting the heat conduction of the arc and the force on the molten pool, although there are differences in their performance in these aspects. Shielding Gas Characteristics: Differences from a Microscopic Perspective   1. Ionization Potential and Arc Stability: The ionization potential determines the ease of gas conduction. The ionization potential of CO₂ is 14.4 eV, lower than that of Ar at 15.7 eV, which gives CO₂ an advantage in igniting and maintaining the arc and can quickly establish a stable welding arc. 2. Heat Conduction and Droplet Transfer: The high heat conduction ability of CO₂ makes it different from the Ar/CO₂ mixture in droplet transfer, arc shape, weld penetration and temperature distribution. The higher heat conductivity promotes the formation of large droplet transfer during droplet transfer, affecting the weld formation and penetration control. 3. Reactivity and Weld Composition: CO₂ is an inert gas at room temperature, but it decomposes into CO, O₂ and oxygen atoms under the high temperature of the arc and becomes an active gas, which is prone to oxidation reactions with metals. Ar is an inert gas, and the Ar/CO₂ mixture has relatively lower reactivity. This difference leads to changes in the content of alloy elements in the weld metal. For example, when using the Ar/CO₂ mixture, the deposition efficiency of the electrode alloy is higher because some alloy elements react with the oxygen decomposed from CO₂ to form oxides that enter the slag, increasing the content of deoxidizers such as Mn and Si in the weld, thereby increasing the weld strength but reducing the elongation and impact toughness. Inert Gases and Mixture Gases: Compatibility in Application   Although inert gases can protect the molten pool, when used alone for the welding of iron-based metals, problems may occur. For example, when using Ar to protect the welding of stainless steel, the arc will be elongated and the outer coating of the electrode will melt prematurely, resulting in poor weld formation. Therefore, Ar/CO₂ mixture gases are mostly used for the welding of iron-based metals. In North America, 75% Ar + 25% CO₂ or 80% Ar + 20% CO₂ mixtures are commonly used for stainless steel FCAW-G welding, and some welding wires require 90% Ar + 10% CO₂, and an Ar content lower than 75% will affect the arc performance. Factors in Shielding Gas Selection: Trade-offs between Cost, Welder and Quality   1. Cost Consideration: Choices behind the Economic Account: In welding costs, labor and management account for 80%, materials account for 20%, and shielding gas accounts for about 1/4 of the material cost. CO₂ has a wide range of sources and can be obtained at low cost through natural gas processing, air separation and other methods. However, Ar is scarce in the atmosphere, and its extraction requires complex equipment and high energy consumption, resulting in high costs. If only the gas cost is considered, CO₂ is the first choice, but the actual decision needs to be comprehensively weighed. 2. Welder Preference and Productivity: The Connection between Operating Experience and Efficiency: When using the same welding wire, the Ar/CO₂ mixture has a more stable arc, less spatter, and stable droplet transfer, which can maintain a good state of the molten pool, is beneficial to welding in special positions and improves productivity. However, its higher Ar content increases the heat radiation received by the welder, and the welding gun is prone to overheating, requiring a higher-power welding gun or more frequent replacement of wearing parts. 3. Welding Quality: The Key Guarantee of Weld Quality: The Ar/CO₂ mixture performs well in weld formation, reducing spatter and reducing post-weld cleaning costs, which is helpful for ultrasonic testing. However, it is more sensitive to gas marks. Because the fine droplets increase the gas dissolution amount, gas marks may affect the appearance and performance of the weld. Typical Application Scenarios: Selection Preferences in Industry Practice   In flat and horizontal high deposition welding, CO₂ is commonly used due to its cost advantage and meeting welding requirements; the shipbuilding industry favors CO₂ because its arc can effectively burn off the primer on the base metal; in the North American offshore construction industry, when welding specific groove welds, the Ar/CO₂ mixture is preferred due to the pursuit of weld appearance and low spatter. If multiple gas shielded welding processes are used in a workshop, the shielding gas is often standardized, and some manufacturers also choose the Ar/CO₂ mixture to optimize the GMAW welding effect. Conclusion: Comprehensive Consideration and Precise Decision-making   The selection of shielding gas for FCAW-G needs to balance cost, quality and productivity. Different manufacturers have different production requirements and cost considerations, and should be determined based on the impact of the gas on various aspects in actual welding operations. After selecting the shielding gas, it is necessary to select a suitable electrode to ensure the best balance of welding quality and efficiency.

In the field of modern welding technology, flux cored arc welding is an extremely important welding method. With its unique process and significant advantages, it has been widely used in many industries. Next, let's have an in-depth understanding of the relevant knowledge of flux cored arc welding. What is flux cored arc welding?   Flux cored arc welding, with the English name Flux Cored Arc Welding and the abbreviation FCAW, heats by using the arc between the flux cored wire and the workpiece. Under the high temperature of the arc, the wire metal and the joint part of the workpiece will melt, forming a molten pool. When the arc moves forward, the tail of the molten pool will gradually crystallize, and finally form a weld. What is flux cored wire? What are the characteristics of the flux core?   Flux cored wire is a welding wire formed by rolling thin steel strip into a steel pipe or special-shaped steel pipe, filling it with a certain composition of flux powder, and then drawing it. The composition of the flux core is similar to that of the electrode coating, mainly including arc stabilizer, slag forming agent, gas forming agent, alloying agent, deoxidizer, etc. These components play an important role in the welding process. What is the function of the flux in the flux cored wire?   1. Protective function: Some components in the flux will decompose and some will melt. The gas generated by decomposition can provide part or most of the protection. The melted flux forms slag, which covers the surface of the droplet and the molten pool to protect the liquid metal. 2. Arc stabilization: The arc stabilizer in the flux core helps to stabilize the arc and reduce spatter. 3. Alloying function: Some flux cores contain alloying elements, which can alloy the weld. 4. Deoxidizing function: The alloying elements in the slag react metallurgically with the liquid metal to improve the composition of the weld metal and enhance the mechanical properties. In addition, the slag can also reduce the cooling rate of the molten pool, prolong the existence time of the molten pool, reduce the content of harmful gases in the weld and prevent porosity.   What are the types of flux cored arc welding?   According to whether an external shielding gas is used, flux cored arc welding can be divided into flux cored wire gas shielded welding (FCAW - G) and self - shielded welding (FCAW - S). Flux cored wire gas shielded welding usually uses carbon dioxide or a mixture of carbon dioxide and argon as the shielding gas. The flux powder in the wire contains few gas forming agents and is similar to general gas shielded welding. Self - shielded welding does not require an external shielding gas and relies on the gas generated by the decomposition of a large amount of gas forming agent in the flux and the slag for protection. What are the advantages of flux cored arc welding?   1. High welding productivity: The deposition efficiency can reach 85% - 90%, and the deposition speed is fast. In flat welding, the deposition speed is 1.5 times that of manual arc welding; in other position welding, it is 3 - 5 times that of manual arc welding. 2. Low spatter and good weld formation: The arc stabilizer in the flux core makes the arc stable, with less spatter, and the weld surface formation is better than that of carbon dioxide welding. 3. High welding quality: The combined slag and gas protection can effectively prevent harmful gases from entering the welding area. The long existence time of the molten pool is conducive to the precipitation of gases, so the hydrogen content in the weld is low and the porosity resistance is good. 4. Strong adaptability: By adjusting the composition of the flux core of the wire, the requirements of different steels for the weld composition can be met. What are the disadvantages of flux cored arc welding?   1. Compared with gas shielded welding, the wire cost is higher and the manufacturing process is more complex. 2. Wire feeding is more difficult and requires a wire feeder with accurately adjustable clamping pressure. 3. The flux core is easy to absorb moisture, so the wire needs to be carefully stored. 4. Slag removal is required after welding. 5. More smoke and harmful gases are generated during the welding process, and enhanced ventilation is required. What shielding gases are usually used in flux cored arc welding? What are the characteristics of each?   Flux cored arc welding usually uses pure carbon dioxide gas or a mixture of carbon dioxide and argon as the shielding gas. The specific choice depends on the flux cored wire used. Argon is easy to ionize. When the argon content in the mixed gas is not less than 75%, stable spray transfer can be achieved in flux cored arc welding. As the argon content in the mixed gas decreases, the penetration depth increases, but the arc stability decreases and the spatter rate increases. The optimal mixed gas is 75%Ar + 25%CO₂, and Ar + 2%O₂ can also be used. When using pure CO₂ gas, because a large amount of oxygen atoms are generated by the decomposition of CO₂ gas under the action of arc heat, which will oxidize the manganese, silicon and other elements in the molten pool, resulting in the burning loss of alloy elements, it is necessary to use a wire with a high manganese and silicon content. Summary   As an important welding technology, flux cored arc welding occupies an important position in the welding field. It has unique process characteristics and many advantages, such as high productivity, good weld formation and high - quality welding, which make it widely used in many industries. However, we should not ignore its disadvantages, such as high cost and complex operation requirements. In practical applications, we should weigh the pros and cons according to specific needs, reasonably select the flux cored arc welding process and related parameters, so as to give full play to its advantages and ensure the efficient and high - quality completion of welding work. With the continuous development of technology, it is believed that the flux cored arc welding technology will also be continuously improved and perfected, and make greater contributions to the development of modern manufacturing industry.