High-amperage welding applications – those exceeding 300 amps – generate a large amount of reflective heat from the arc and, therefore, require durable equipment to provide the best welding performance and prevent consumable failure. The nozzles, contact tips and gas diffusers, in particular, must be able to withstand the demands of the job, whether the application requires semi-automatic or robotic welding.
Choosing the right consumables in high-amperage welding applications can help enhance the success of the process in many ways. Specifically, they minimize downtime due to premature failures, reduce inventory and replacement costs, prevent quality issues that require time-consuming and costly rework, and lower the risk of damage to the MIG gun that can be caused by heat buildup.
To obtain the best results, it’s important to know not only the factors that negatively impact consumables, but also the ways to extend consumable life and the product options available on the market. This article discusses a handful of best practices for gaining success in demanding high-amperage applications, such as those found in the heavy-equipment market where thicker materials and longer welds are prevalent.
Making a choice
Heavy-duty consumables have a greater mass than standard-duty ones, allowing them to resist higher heat levels for a longer period of time. The greater mass of these consumables pulls the arc’s heat away from the contact tip, nozzle and gas diffuser. This benefit often makes them a good choice for high-amperage welding applications.
Heavy-duty consumables come in various sizes and materials, each of which provides specific advantages. For example, brass nozzles tend to be more spatter-resistant, though they can deteriorate more quickly than copper if they come in contact with the molten weld pool. There are also heavy-duty contact tips, which are usually available in copper or chrome zirconium.
For high-amperage applications that require larger diameter welding wires, 0.052 in. and greater, extra heavy-duty consumables are another option. Contact tips in this category generally have an outside diameter of about 3/8 in. compared to heavy-duty contact tips that have an OD of approximately 5/16 in.
Conversely, for some high-amperage applications, standard-duty consumables may be suitable options. In applications with lower duty cycles, heat generation is also lower since less time is spent welding. In this situation, standard-duty consumables could also work even when welding at higher amperages because there would be more frequent pauses in the operation.
Also, for companies that require frequent consumable changeover as a matter of protocol, welding operators will likely change out these consumables before failure occurs from high heat levels. When considering standard-duty consumables in place of heavy-duty consumables, it’s important to test them for durability in the specific application before fully implementing them in the welding operation.
Connection is key
In high-amperage applications, it’s especially critical to have sound connections between consumables, which helps minimize resistive heat, ensure strong electrical conductivity and reduce the potential for premature failure. Look for high-quality consumables that seat precisely together and for a strong attachment between the nozzle, contact tip and gas diffuser. A strong connection helps pull heat way from the consumables by creating a greater amount of mass to manage the heat from the high-amperage welding arc.
Checking consumables regularly for tight connections and following the manufacturer’s instructions for installation are also important steps to gaining longer consumable life.
Invest in peripherals
There are additional tools and pieces of equipment that can help extend
consumable life in robotic welding applications, especially high-amperage ones. A nozzle cleaning station (or reamer) cleans spatter from the robotic gun and nozzle and also clears away any debris in the retaining head that may have accumulated during the welding operation. A sprayer that applies a water- or oil-based anti-spatter compound can also be added to these stations. This helps protect the nozzle, retaining head and workpiece from spatter after cleaning.
Because high-amperage applications generate higher heat levels, spatter can adhere more readily to the consumables. That makes it especially important to program the robot to go to the nozzle cleaning station more frequently than in a lower amperage job. Each application is different, but it’s a good idea to employ this peripheral as often as possible in high-amperage applications.
In addition, placing the nozzle cleaning station close to the robot makes it easily accessible for the robot. It also allows it to be used in between cycles, such as during part loading or tool transfer, minimizing interruptions to the welding operation.
Consider the welding mode
Some high-amperage applications use a pulsed welding mode, which can be particularly harsh on consumables. These welding programs have a unique waveform that causes the power source to pulse between low background currents and high peaks.
Mechanical wear on the contact tip is inevitable in any welding application due to the constant friction of the welding wire feeding through the tip. In high-amperage applications employing a pulsed welding mode, however, electrical wear can also be an issue. To help address this, heavy-duty or chrome zirconium contact tips are a good choice for this welding process, as they tend to be more durable.
Monitoring contact tip usage regularly in pulsed welding applications is also important. It allows welding operators the opportunity to change over contact tips before they experience problems, which can help prevent issues such as loss of electrical conductivity, burnbacks or excessive spatter, as well as poor weld quality, rework and downtime.
The impact of welding wire
In high-amperage applications, 500- to 1,000-lb. drums of wire are often used to minimize changeover and associated downtime. The wire in these drums tends to have less of a cast and helix than wire that feeds off a smaller spool and as a result, feeds through the contact tip in a relatively straight fashion, making little or no contact with the tip.
This lack of contact can cause the welding wire to arc back into the contact tip, leading to a burnback and creating downtime for contact tip changeover. It also minimizes the electrical conductivity necessary to create a good arc and a sound weld.
A good fix for this problem is to select undersized contact tips, especially in high-amperage applications that use solid wire. For example, a 0.040-in.-diameter (1-mm-diameter) contact tip can work for a 0.045-in. wire. Undersizing is not always an option in applications that require metal-cored wires, so check with a trusted welding distributor.
Wire type can also impact the longevity of contact tips. Non-copper-coated solid wires, for example, tend to wear contact tips more quickly than copper-coated ones in which the coating acts like a lubricant to improve feedability and extend contact tip life.
The higher heat generated by high-amperage applications can cause significant stress on consumables. In these applications, they are more prone to spatter accumulation as well as mechanical and electrical wear.
While there are numerous consumable types and options, selecting the right one for high-amperage applications is an important first step in gaining the best welding performance, quality and productivity. Consumable choice can also help minimize replacement or rework costs.
When considering consumables for high-amperage applications, a trusted welding distributor or welding consumable manufacturer can provide recommendations and information that makes the choice easier.