Figure 1. Thermatool CFI HF welder. Source: Thermatool

With steadfast thermal properties and excellent processing standards, copper tubing has long dominated the market for thermally conductive small diameter tubing. However, as the price of copper increases, manufacturers have started exploring new materials for this application, most notably in the form of cladded aluminum. Clad aluminum alloys are continuously proving to be a reliable alternative; they feature improved corrosion resistance on the tubing’s outer layer, which enables the use of a less costly grade of aluminum when implementing an embossed inside diameter.

The intricacies of small diameter aluminum tube welding

Welding innovative new materials such as cladded aluminum can be a challenge for many high-frequency (HF) welders that simply do not have the frequency range or process control capabilities to develop this material at commercially viable quality levels. This is especially problematic when working with small diameter tubing, which can preclude the use of additional tools per miniscule space requirements.

Small diameter aluminum tubing is typically produced by forming a flat sheet of material into a circular shape, which comes together in the form of a “V” that is continuously welded together. This process creates a bead on the inner and outer tube diameters that may need to be removed with a scarfing knife. However, if the diameter is small enough, there is no room in which to fit a scarfing knife, or even an impeder to help control the flow of current, for that matter. In these cases, welding must be controlled so that tubing is produced without the need for bead removal.

Thermatool addressed this small diameter aluminum tubing challenge by introducing HF welders that provide the lowest weld heat input (a combination of power and frequency).

What makes Thermatool welders unique is the ThermaView control software that allows users to create a recipe for a given tube outer diameter, wall thickness and line speed. Once process parameters – like power, frequency and vee length – are validated, manufacturing personnel can then recall and reuse the same recipe for a given product. This combination of low heat input and advanced ThermaView controls means excellent weld quality and repeatability, even under extenuating constraints.

Figure 2. ThermaView Control software with recipe setup and database. Source: Thermatool

Thermatool can also help initialize process recipes for new materials by providing on-site training, or an in-house materials characterization lab capable of analyzing customer-provided samples (coupons). A trusted consultative partnership is especially beneficial when considering – or perfecting – the use of new materials; for instance, a transition from copper to aluminum.

Advanced HF welders for more than just aluminum

Thermatool’s entire range of HF welders work at controlled output power and frequency ranges, and all use current-fed inverter (CFI) technology to control power output to exacting specifications. Thermatool’s original CFI HF welder is the most reliable solid-state tube and pipe welder on the market and can be set up to weld at fixed frequencies of between 150 kHz and 900 kHz, with a power output of up to 1,200 kW.

These CFI welders feature a patented AutoMatch™ technology, which ensures full power output and stable welding frequencies over a wide range of product sizes and setups. CFI welder power set-points can be maintained to ±0.5%, while the fixed HF welding frequency output is maintained to ±1.0%. The low weld power output is incredibly stable and features short-circuit tolerance for operation through coil arc-overs and DC ripple of less than ±.5%.

Precise HF weld heat input control gives small diameter tube producers the promise of statistically reliable process control. This careful control is critical in extending the life of scarf tooling when used, and it is even more critical when such tooling cannot be used.

Other Thermatool HF welders include the MPACT™ welder, with an output of up to 100 kW and a welding frequency of 300 kHz. The Thermatool HAZControl™ and High Power models can each weld at a selectable 200 kHz to 400 kHz, with maximum power ratings of 1,400 kW and 2,000 kW respectively. Note that in each of these lines, Thermatool uses its characteristic CFI technology for stable power output control.

This superior CFI control methodology, combined with an industry-leading range of set and variable frequency devices, means that users can specify the exact process parameters to maximize throughput while achieving 6 sigma defect rates. Notably, Thermatool is the only company that can weld at frequencies up to 900 kHz. With the proper welding setup, small diameter tubing can be processed at rates exceeding 200 meters per minute (MPM), or more than 650 feet per minute (FPM).

Figure 3. Welding area setup. Source: Thermatool

When performance meets longevity

For over 70 years, Thermatool has woven efficiency and reliability into the fabric of their equipment. Remarkably, the company’s first solid-state welder – commissioned in 1995 – is still working today, nearly 30 years later. They are no stranger to proven performance and process control to maintain consistent tube and pipe manufacturing quality. In addition to delivering exceptional performance, Thermatool HF welders operate with zero greenhouse gas emissions, offering an environmentally friendly solution without compromising on efficiency or quality. As the leader in HF welding technology, they have vast experience with not only aluminum tubing, but a multitude of other applications as well.

Thermatool is the only global induction heating and welding manufacturer specializing in tube and pipe welders. HF induction welding can be used to weld carbon and stainless steel, brass, copper, aluminum and even exotic alloys such as boron steel, HSLA, AHSS and transformation induced plasticity (TRIP) steels.

Thermatool: Global expertise, individualized service

Every Thermatool HF welder is backed by world-leading weld process and materials knowledge, providing each customer with the best approach to meet their individual welding challenges. Thermatool products are manufactured around the world by the Inductotherm Group network of companies, providing localized manufacturing, service, and support in every region. Our advanced technology and expertise are global, delivering world-class solutions wherever they are needed. Get in touch today to see how Thermatool can help with your HF induction welding needs.