The strength and quality of welds is one of the single most important aspects of safe, reliable industrial fabrication and construction. This makes choosing the best welding process for a given application of paramount importance. By far one of the most commonly used and valuable welding processes is gas metal arc welding (GMAW), especially the pulsed transfer mode (GMAW-P).
What Is GMAW-P?
Pulsed gas metal arc welding (GMAW-P) is a variation of the spray transfer mode of the process. Basic spray gas metal arc welding involves using a stable electric arc between the electrode and the metal being welded. It uses a high voltage and current, which results in the molten metal from the electrode vaporized into a steam. This eliminates spatter and creates a high-quality weld finish. However, the high amount of voltage and current also results in high heat output and a large weld pool that thus is not suitable for all weld positions and may also result in burn-through, especially on thinner work metals.
GMAW pulsed solves this problem by rapidly alternating electrical pulses between high and low currents, often as many as 30 to 400 times every second. Each time the current pulses, a small molten metal droplet falls from the electrode to the work surface, preventing the spatter without the need for the high heat required in basic spray GMAW that results in vaporizing. Since the heat is drastically reduced, the weld pool is also much smaller, and thus welding can be done in any position. The lower heat also makes it possible to weld even thin, non-ferrous pieces of metal or alloy.
To understand how GMAW Pulse compares to traditional Gas Metal Arc Welding (GMAW), check out our in-depth look at GMAW.
The Industrial Uses of GMAW-P
GMAW-P was originally developed for welding aluminum. Aluminum is very important in a wide range of industrial applications because it is lightweight yet strong, has high corrosion resistance, and is very thermally conductive. However, because it is so thermally conductive, it is challenging to weld with other welding processes. It would rapidly transfer heat away from the weld, making it difficult to establish a weld pool without very high temperatures. This, in turn, made it prone to burn-through and other defects. GMAW-P solves this problem by offering greater weld pool control, improving fusion, and preventing problems like warping and burn-through.
GMAW-P is also well suited to welding on stainless steel. Stainless steel is another commonly used metal in industrial applications because, like aluminum, it also offers high corrosion resistance. Additionally, stainless steel has a high tensile strength and is very ductile, able to withstand demanding conditions and temperatures. However, unlike aluminum, stainless steel is a very poor conductor of heat, creating its own set of challenges for welding since the weld pool is typically sluggish and doesn’t flow well. Likewise, stainless steel may be subject to thermal expansion during welding, which can lead to warping and distortion. Once again, GMAW-P solves these problems thanks to the excellent control it offers over the weld pool and its ability to offer good penetration.
Benefits of GMAW-P
- Enhanced Control and Precision: GMAW-P provides exceptional directional control over the weld pool, making it easier for operators, especially those new to welding, to achieve high-quality welds with good bead appearance. The pulsing current allows for meticulous management of heat input, resulting in reduced distortion and improved structural integrity of the welds.
- Reduced Spatter and Cleanup: Compared to conventional welding methods, GMAW-P significantly minimizes spatter formation. This reduction not only enhances the quality of the weld but also streamlines post-weld cleanup, improving overall efficiency in the welding process.
- Versatility Across Materials: GMAW-P is adaptable for welding a variety of materials, including aluminum, stainless steel, and carbon steel. Its ability to handle both thin and thick materials makes it suitable for diverse applications, from automotive to aerospace industries.
- Lower Heat Input: The process operates with a lower average current, which helps prevent issues such as melt-through and warping, particularly in thinner materials. This characteristic allows for faster welding speeds without compromising the integrity of the weld.
- Improved Weld Quality: GMAW-P helps reduce common welding defects like incomplete fusion and porosity. The controlled heat input and the ability to tailor arc characteristics to specific applications contribute to superior weld quality.
- Higher Deposition Rates: The technique allows for the use of larger diameter filler wires, which can increase deposition rates and productivity. This is particularly beneficial when welding thin-gauge materials, as larger wires are less prone to feeding problems.
- All-Position Welding: GMAW-P can be used effectively in all positions, making it a versatile choice for various welding scenarios.
- Training and Adaptability: While GMAW-P may require more initial training and investment, the quick return on investment through increased productivity and reduced downtime can be substantial. The process also features both synergic and nonsynergic systems, allowing operators to choose the method that best suits their needs.
GMAW-P vs. Standard GMAW
| Feature | Standard GMAW | GMAW-P |
|---|---|---|
| Process | Continuous wire feed with stable electric arc | Alternates between high peak and low background currents |
| Heat Input | Higher, leading to larger weld pools | Controlled, resulting in smaller weld pools |
| Spatter | More spatter due to droplet transfer | Reduced spatter for cleaner welds |
| Applications | Suitable for thicker materials; limited positional welding | Effective for thin materials and various positions; ideal for aluminum and stainless steel |
| Weld Quality | Prone to defects like porosity and incomplete fusion | Reduced defects and better fusion |
| Versatility | Limited to certain positions | Suitable for all positions |
| Productivity | Lower deposition rates | Higher deposition rates due to larger wire diameters |
| Customization | Limited adjustability | Adjustable parameters for specific applications |
| Equipment Cost | Lower | Higher due to more advanced equipment |
| Surface Cleanliness | Less sensitive | More sensitive, requiring clean surfaces |
| Operator Training | Basic training required | Additional training may be needed due to complexity |
Challenges Associated with GMAW-P
No welding process is perfect, however; as with other processes, some challenges are associated with GMAW-P. For example:
- GMAW-P utilizes more expensive, complicated equipment than many other welding processes.
- GMAW-P requires a shielding gas to function and is thus not well suited to welding outdoors or in other areas with a draft.
- GMAW-P requires either pure argon or high argon blends, which are more expensive than shielding gases such as carbon dioxide.
- GMAW-P is slightly more sensitive to surface contamination than non-pulsed GMAW, which is also more sensitive to contamination than other welding processes.
- GMAW-P is much less portable than SMAW.
- GMAW-P requires careful setup of welding parameters (speed, voltage, distance from welding surface, etc.) for best results.
STI Group is up to the challenges associated with GMAW-P and is pleased to offer this high-quality, dependable welding process to our industrial clients. In addition to GMAW-P, we also specialize in other welding processes, such as Gas Tungsten Arc Welding (GTAW), ensuring we can meet a wide range of fabrication needs.
We rigorously test all of our welds to ensure that only strong, defect-free welds end up out in the field. We also carefully consider which welding process is best for a given application and will always choose the one that yields the best results.
