• FCAW process produces a flat, smooth bead due to the slag system.welding image by glgec from Fotolia.com
  
  Flux-cored arc welding, or FCAW, uses a flux-cored wire consisting of a tubular metal wire filled with flux, minerals and alloy additions. A form of arc welding, the FCAW uses a wire-feed machine to produce a high-quality weld. While some applications require the use of CO2 shielding gas, several FCAW applications completely eliminate the need for gas shielding equipment through the shielding nature of the flux.
  
  

Selecting Wire Diameter

• The most common FCAW wire used is 0.045 inch, with available wires ranging from 0.035 to 1/8 inch diameter. According to the Fabricators and Manufacturers Association, many welders assume that the larger the wire, the higher the deposition rate. However, the deposition rate is controlled not by the wire diameter, but by the current's density. Larger wires do give the welder the ability to weld at a higher current level. Using the manufacturer's recommended electrode parameters results in the proper deposition rates.
  
  

Recommended Torch Angles

• Using a backhand or drag technique with FCAW allows for increased penetration. The arc force holds back the puddle and provides consistent coverage on the bead. Maintain an angle between 10 to 20 degrees off-center to create a supporting slag system. When using a forehand or push technique, using a 10- to 20-degree angle off-center provides a consistent weld with a slightly concave bead profile. Avoid using a sharp torch angle with either technique. Too large an angle reduces the effects of the shielding gas.
  
  

Proper Cleaning

• Properly cleaning the weld areas and removing all grease, rust, paint, coatings, oil and debris aids in porosity prevention. Porosity damages welds when gas becomes trapped in the metal. Flux-cored wire featuring deoxidizers help eliminate porosity when welding dirty metals.
  
  

Control of Heat Input

• The desired results of most weld procedures depend on heat input. The input is affected by the welding current, arc voltage and travel speed. For example, if the travel speed of the weld slows, but current and voltage remain constant, the heat input increases. Problems with the improper heat input may affect the weld's chemical compositions or the weld's structure. By keeping consistency in the traveling speed of the weld, current and the voltage, the welder maintains a consistent heat input.
  
  

Eliminating Slag Inclusions

• Slag inclusions occur in the weld when the slag becomes trapped inside of the weld. Slag is produced by the wire's molten flux core. Proper welding techniques help to eliminate slag inclusion. Proper bead placement on root passes or wide V-groove openings is essential. Allow ample space in the weld joint for all additional passes. The correct travel angle, heat input and travel speed usually corrects post-slag inclusion problems. Too low a heat input often causes slag inclusions. When welding multiple passes, remove all slag with a chipping hammer, wire brush or grinder between passes.