Earlier this week a manufacturer ask if there were any true benefits of using pulse over CV in the MIG process. The short answer is “absolutely.” But before we can answer we need to ask: “what is the application?” To really appreciate the benefits of pulsed GMAW compared to traditional CV (short arc or globular) it is helpful to have fundamental knowledge on the different modes of metal transfer. In the next few days we will post an in-depth look at the different modes. For now, we’ll focus on listing the advantages and limitation of the pulse process.
Pulse welding is simply alternating between a peak (high) and a background (low) current. Metal is transferred through the arc during the peak current. It is also important to mention the difference between pulse and spray pulse. Many people use these terms interchangeably and it can create some confusion. When we say “pulse” we assume “spray pulse”. Spray transfer is achieved when the arc reaches an energy level at which the molten droplets are transferred through the arc. Below this energy level metal is transferred by creating a short with the base material and then separated by a blast of amperage. Pulsing is a feature of the power source. You can be pulsing (alternating between high and low current) but if you are not above the transition current you would not be in a true spray transfer. You would get some benefits of pulse welding, but not all. The advantages and limitations shown below assume you are spray pulse welding. The other variable in achieving spray transfer is the shielding gas. You need to have at least 83% Argon. Common blends suitable for pulse welding are: 90%Argon/10% CO2
Advantages of Pulse Welding
– Reduction in overall heat input (decreases distortion, decreases the heat affected zone)
– Reduction in spatter (reduces rework and secondary operations)
– Higher deposition rates out-of-position (product of rapid cooling of the puddle during background current of the cycle)
– More resistant to lack of fusion than other modes of transfer (most people assume pulse welding reduces penetration)
– Can reduce fume levels generated by the arc compared to other modes of transfer
Limitations of Pulse Welding
– Equipment is typically more expensive than conventional step-down transformer power sources
– Gas blends required are more expensive than the commonly used 100% CO2 or 75%Argon/25% CO2 gas.
– Higher arc energy produces higher levels of radiated heat and a brighter arc, this requires a darker shade for the welding lens and more protection for the welder (usually gloves with heat shield)
Do you have experience with pulse welding? What are your thoughts?