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Why Size Matters When Friction Welding

January 26, 2011

My colleague, Tim Stotler, gave a very good overview of friction welding here. Go ahead, click the link… you know you want to!  Just don’t forget to come back and finish reading my blog. In his write-up, he touches on the variety of components that are commonly friction welded in industry (hydraulic cylinder rods, aircraft engine parts), the benefits to friction welding (fast, ability to join dissimilar materials), and the varieties of friction welding (linear, direct-drive, and inertia). One thing he artfully (and perhaps tastefully) dodges is the issue of size limitations when friction welding.

Machines are commonly defined by the force they can apply (i.e. tonnage). Inertia welders often have a rating based on the mild-steel bar diameter they are capable of welding. In general, the larger the area you want to join, the higher the force (and energy) required. The higher the force required, the larger the machine required. The larger the machine required, the more expensive the machine. The more expensive the machine, well… now we engineers have to go to the dark side and spend more time with an accountant or finance person.

Up until now, the majority of very large machines have been reserved for large diameter, tubular, aerospace applications. These machines are capable of weld forces in excess of 2,000 tons, and can cost several millions of dollars to build. The friction welding process is required for these parts due to the benefits of solid-state bonding – specifically, fusion welding of these components leads to unacceptable degradation in the material’s mechanical properties. These are the same advantageous that have been employed on smaller parts (1/4-in. to 6-in. diameter parts) for decades.

A host of manufacturing and in-service concerns are beginning to open the door for exploring large-scale friction welding for other applications. Consider oil drill rod as an example. There are aluminum alloys with great strength-to-weight ratios and excellent corrosion resistance – very good characteristics for sour-service drilling. The issue is that in the drilling process, these 40-ft “sticks” need assembled and disassembled on a regular basis – meaning they must be joined by some type of threaded connection. As you can imagine, threading aluminum has a number of significant concerns from a durability standpoint. What if one could friction weld a steel connector to the end of each aluminum drill rod?

We have a range of friction welding equipment available for development and pre-production prototype services. Our machines start at approximately 12,000 lbs weld force capacity and go up to our newest toy, which has a 425,000 lb capacity. If you don’t know how to apply friction welding to your application, give us a call. We’ll do our best to keep the finance folks at bay.