TPT March 2025

ARTICLE

Thermatool Corp

The latest trends in high frequency contact tube welding By Olexandra Tupalo, manager, Thermatool Labs

Energy costs are a significant concern worldwide and are expected to increase over time. The HF contact process is significantly more energy efficient than the HF induction process. As the power consumption increases with increasing pipe or tube diameter, this statement holds particularly true for the production of larger tube and pipe for structural, line pipe and piling applications. The chart (Figure 2) below compares the energy required to weld the same tube with a 0.5" wall thickness at 90ft per minute with both HF contact and induction processes. The tube diameters range from 6 to 16". The HF induction process requires more than double the energy compared to the HF contact process over this range of tube sizes. Significant power savings can be achieved when welding large diameter pipes using an HF contact welding process versus HF Induction welding.

High Frequency (HF) welding is a manufacturing process that uses high frequency electrical currents to heat and join metals. This technique involves applying an alternating current at a high frequency (100 to 900kHz) to the workpieces, which generates localised heat at the point of contact. The two edges to be joined are arranged in a “V” shape, with the weld point immediately following the apex of the Vee. As the edges pass through the weld rolls, the molten metal is ejected (“squeezed out”) and the forge weld is formed. There are two methods of HF welding: induction and contact mode (Figure 1) . HF induction welding utilises an encircling copper coil to induce high frequency currents that flow along the strip edges. In contrast, HF contact welding employs metal contacts, typically made from a copper alloy, which are in direct contact with the tube or pipe to deliver the HF current. High frequency contact welding is beneficial for welding heavy walls and large tube diameters as it utilises less power than induction welding. Both contact and induction welding methods produce a strong, high quality solid-state weld. There is a growing emphasis on energy-efficient HF welding systems. New developments focus on reducing power consumption and improving overall energy management. This trend aligns with broader industry goals of sustainability, as manufacturers seek to minimise their carbon footprint and operational costs.

Note: Welding Power is for 0.5" (12.5mm) Wall Pipe welded at 90ft per minute (27mpm) Figure 2: Graph depicting power consumption for induction and contact welding processes When to choose HF contact welding Every process has its advantages and disadvantages, and the HF contact welding method is no exception. One of the main benefits of this method is its lower power consumption compared to the induction method; the exact power savings will depend on the size of the tube and the length of the vee. In situations where energy efficiency is crucial, the contact welding method is the preferred option. Another advantage is that the same contact tips can be used across a full production range. In contrast, induction coils typically must be selected based on the tube outer diameter

Figure 1: HF contact welding

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MARCH 2025