An Introduction to Pulsed GMAW
By Erik Brown, a welding engineer and AWS CWI, industrial equipment, Miller Electric Mfg. Co., Appleton, Wis. Reprinted with permission: The AWS Welding Journal This process provides directional control over the weld pool, quick wire feed and travel speeds, and reduced spatter Companies are always looking for ways to become more productive, create higher quality parts, and generate greater profitability. In some cases, reaching these goals is a matter of improving operator training, implementing lean practices, or taking on other continuous improvement initiatives. Changing welding processes can make a significant difference.- Exceptional directional control over the weld pool makes it easier for new welding operators to learn the GMAW-P process and create welds with good bead appearance. In addition, most pulsed waveforms have a built-in “adaptive function” technology that allows more inexperienced welding operators with less steady hands to produce more consistent welds.
- Improved control over arc starts and stops helps reduce weld defects and improve appearance. When the welding operator initiates the arc, the process delivers higher energy, which offers good fusion. It then reduces the amount of energy going into the weld to prevent melt-through and provide greater control over the weld bead appearance. When stopping the arc, a GMAW-P process with a crater function is ideal, as it allows the operator to ramp down to a cooler welding parameter to fill in the crater at the end. This helps eliminate the potential for termination cracking that can easily occur when welding materials such as aluminum.
- Faster wire feed and travel speeds can occur in many applications with GMAW-P. This helps increase productivity while simultaneously reducing heat input, to decrease residual stress and reduce the opportunity for distortion or melt-through. Consider stainless steel. This material cannot handle too much heat or the welding operator may burn the chromium and nickel out of the base material. As a result, the weld metal and surrounding joint turn into mild steel, which lacks corrosion resistance and toughness. Pulsed GMAW is a good solution for welding this material and avoiding such pitfalls.
- Some GMAW-P power sources allow welding operators to adjust the width of the arc cone, which helps them tailor the bead profile to the application. This helps prevent overwelding and poor fusion. Wider beads help improve tie-in on both sides of a joint, while narrower beads provide good fusion at the joint’s root.
- Reduced spatter generated during the GMAW-P process results in reduced time and money spent on associated grinding and postweld cleanup.
- Simple process setup means the welding operator uses a single knob to set the wire feed speed. Because the arc length number or voltage automatically adjusts with GMAW-P, the arc becomes longer or shorter accordingly, for greater ease of use and productivity.