Finding new ways to increase productivity and throughput in trailer fabrication is an everyday challenge on the shop floor. Getting the results needed may require an investment in new technologies or a change to the way things have always been done. In some shop welding applications, submerged arc welding (SAW) can deliver significant advantages for productivity, efficiency and operator comfort while maintaining necessary weld quality. With deposition rates that are much greater than other welding processes, SAW is especially beneficial for applications that require welding long, straight joints. This process can be mechanized by pairing it with a tractor to provide even greater benefits for productivity, quality and operator comfort in suitable welding applications. If you’re considering submerged arc welding, or if you’re already using SAW but would like to utilize the process for even greater benefits, a SAW process with a three-wheeled or four-wheeled tractor might be an option for your operation.
HOW SUBMERGED ARC WELDING IMPROVES EFFICIENCY
Submerged arc welding is a wire-fed process that is best performed using mechanical equipment that typically cannot leave the shop. SAW is often used with carbon steels, stainless steels and some nickel alloys, and is best suited for materials that are ½ in to 5 in thick or more. It can be used to weld material as thin as 1/8 in by accounting for travel speed and heat input to avoid burn-through. In SAW, a granular flux is used to protect the arc from the atmosphere; the process name refers to the fact that the arc itself is buried in the flux so that the arc is not visible when parameters are correctly set and the layer of flux is sufficient. The wire is fed through a torch that moves along the weld joint. The arc heat melts the wire, flux and base material to form a molten weld pool.
Depending on its design, the flux can also add alloying elements to the weld metal to alter the chemical and mechanical properties of the weld. Single wire SAW applications can achieve deposition rates of up to 35 lb per hour, depending on wire size, type and polarity. Besides welding trailer frames, typical SAW systems that may come to mind are a large manipulator arm and rollers for a pressure vessel, or a side beam for specific parts that might have a positioner to turn them. SAW requires a number of often bulky components to perform the process, which can make it difficult to complete the ideal weld using a hand-held SAW system. Using a SAW tractor accomplishes the task of getting the flux, wire, torch and process controls into a small compact tool that can be easily moved to the work.
Welding applications with long and straight weld joints on repetitive parts are well-suited to using a three-wheeled tractor accessory with the SAW process. Examples of these types of applications include T-joint or fillet welds that are at least 5 ft to 10 ft long, such as when fabricating structural boxes or trailer frames. When your part is large enough, the tractor can simply ride on the part. If the part is not large enough, something can be fabricated for the tractor to ride on, and the torch can be manipulated to the necessary location. This allows you to perform SAW where you may not have considered it possible. Because a SAW tractor is self-propelled, it mechanizes the process for even greater productivity and operator comfort. For welds on thicker materials that require multiple passes, using a three-wheeled tractor with SAW may allow you to eliminate multiple passes and complete the weld in one pass, saving time and money.
CHOOSING THE RIGHT TRACTOR
Here are some key factors to consider in choosing the right tractor for your SAW needs:
- A tractor that offers a compact size and can be configured into multiple positions, such as our three-wheeled tractor option that provides greater flexibility and setup options in SAW applications. When an accessory offers greater flexibility, it can be used in more applications that require a variety of weld positions.
- Tractors that use a digital interface help you monitor and regulate welding parameters, such as travel speed. For example, a tractor with greater digital programmability lets operators set a specific travel speed for the weld and get immediate feedback on that speed during the welding process to ensure that the set and actual speed are consistent for improved weld quality and repeatability.
- Look for an interface that allows all-in-one control so that you can control the tractor as well as the welding functions from the same panel. This results in greater ease of use and saves time.
THE IMPORTANCE OF FILLER METAL
Just as with all welding processes, selecting the right filler metal for the application is key to achieving the results you want in submerged arc welding. The filler metal and flux choice in SAW should match the requirements of the application. There are three main types of wires that can be used with SAW welding: solid wire, metal-cored wire and seamless metal-cored wires. A wide variety of fluxes are also available to meet specific requirements and needs.
Consider the demands of your specific applications and what each type of wire and flux can offer in making the choice. Solid wire is the most commonly used filler metal type in SAW applications, delivering good penetration and bead appearance. Metal-cored wires offer exceptional deposition rates and good mechanical properties, and many options are available for welding low-alloyed steels. Seamless metal-cored wires are a good option for some critical applications when it’s important to have low hydrogen levels and good mechanical properties. Keep in mind that it may require testing various combinations of flux and wire to find the right one for the job. Consulting with a filler metal manufacturer can help you in testing and choosing the best option.
INVESTING IN PRODUCTIVITY
While converting to SAW can mean a larger upfront investment, a shop can see a fast payback and return on that money thanks to the major productivity capabilities the process provides. An operation that switches to SAW can double or even triple productivity and make more efficient use of labor time – outcomes that help justify the initial investment. Utilizing a SAW tractor accessory can provide greater flexibility in a variety of SAW welding applications. A tractor allows you to take the process closer to the job and helps enhance productivity and quality gains from SAW, overcoming the barriers that may have kept you from considering SAW as an option in the past. Understanding the SAW process and the overall equipment needs — and selecting the proper accessories and wire and flux combination for the application — can help a trailer welding operation realize the full potential of the process, increasing productivity, weld quality and operator comfort compared to semi-automatic hand-held processes.
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