Double protection of FCW：What is “Dual Shielding”?
Double protection of FCW refers to the simultaneous provision of two forms of protection during flux-cored welding to prevent the molten metal from reacting with oxygen and nitrogen in the air:
① Double protection of FCW ——Gas Shielding: An external shielding gas (usually carbon dioxide or a mixture of argon and carbon dioxide) is ejected through the welding torch nozzle.
② Double protection of FCW ——Slag Shielding: The flux inside the flux-cored wire melts under the high arc temperature, forming a slag that coats the weld surface.
This combined “gas-slag” shielding mode gives dual-shield flux-cored wire a series of outstanding advantages.
① Double protection of FCW：Excellent Welding Quality
● Beautiful Weld Bead Formation: The presence of slag makes it easier to control the surface tension of the liquid metal, resulting in a fine, smooth weld ripple. The appearance quality is far superior to that of solid wire and approaches or even exceeds that of manual welding rods.
● Excellent Mechanical Properties: The flux core can be added with a variety of alloying elements (such as manganese, silicon, nickel, etc.), allowing precise adjustment of the weld metal’s chemical composition to achieve high strength, high toughness, and excellent impact resistance.
● Low Defect Rate: Double shielding significantly reduces the risk of nitrogen and oxygen from the air entering the weld pool, significantly reducing weld porosity and slag inclusions. The slag solidifies more slowly than the metal, facilitating gas escape and further reducing porosity.
② Double protection of FCW：Extremely High Welding Efficiency
● High Deposition Efficiency: Flux-cored wire boasts a high current density and rapid melting rate, resulting in a deposition efficiency (the ratio of deposited metal to melted wire) exceeding 90%, significantly exceeding that of manual welding rods (approximately 55%-65%).
● Continuous Welding: Supplied in coils, it eliminates the need for frequent rod changes, enabling long periods of continuous welding. This significantly reduces auxiliary time and improves overall production efficiency.
● Deep Penetration: The arc is concentrated and has strong penetrating power. For thicker plates, smaller or even no bevels can be made, reducing filler metal usage and the number of weld passes.
③Double protection of FCW：Excellent process adaptability
●Excellent all-position welding performance: The slag’s “lifting” effect helps control the weld pool in vertical and overhead welding positions, preventing it from dripping. This makes welding easier than solid wire and enables excellent weld formation in all positions.
●Insensitive to oil and rust: The gasifier and deoxidizer in the flux core effectively remove minor oil and rust on the workpiece surface, reducing pre-weld cleaning requirements and making it very practical on the jobsite.
●Stable arc and low spatter: The flux core composition helps stabilize the arc, especially when using low-cost shielding gases such as carbon dioxide. Its arc stability and spatter control are superior to solid wire.
④Double protection of FCW：Flexibility in alloy system design
●This is a core advantage of flux-cored wire. By varying the flux core formula, wires suitable for different steel types (such as carbon steel, low-alloy high-strength steel, stainless steel, and heat-resistant steel) can be manufactured without changing the rolling process. This makes the development of welding materials for specialized applications very economical and efficient.
⑤ Double protection of FCW：High Overall Economic Benefits
● Although the cost per unit weight of welding wire may be higher than that of solid wire, its extremely high deposition efficiency and welding speed make the total cost per unit length of weld (including labor, gas, electricity, etc.) more competitive.
Summary and Applicable Scenarios
In summary, double-shielded flux-cored wire combines the process-friendliness of manual welding rods with the high efficiency of solid wire, while achieving high-quality weld performance through combined “gas-slag” protection.
It is particularly suitable for:
① Applications requiring high weld quality and appearance, such as shipbuilding, pressure vessels, bridges, and high-rise steel structures.
② Heavy-duty manufacturing and construction sites requiring efficient operation.
③ All-position welding tasks.
④ Workpieces with slightly contaminated surfaces that are difficult to clean.
Of course, it also has some disadvantages, such as:
① Relatively high welding wire cost.
② The need to carry and protect gas cylinders increases the complexity of the equipment.
③ Slag is generated, requiring post-weld cleaning.
④ The flux core is susceptible to moisture absorption, requiring certain storage conditions.
Despite this, its comprehensive advantages have made double-shielded flux-cored welding wire occupy an extremely important position in the modern welding industry.