Ultrasonic welding is a solid-state welding process that uses ultrasonic vibrations to weld pieces of metal together. The metals are welded together by heat generated by friction when applying high-frequency ultrasonic vibrational energy.
Stefan Mueller, head of R&D at Schunk Sonosystems, said: "Standard steel bolts simply cannot cope with the extreme pulling and bending forces of ultrasonic vibration, so we had to find a bolt that does. Of all the screws we tested, only Bumax met all our needs. Not only are Bumax consistent in how they perform and do not break, they last the lifetime of the sonotrode without problem, are not creating abrasion dust on the screw head and do not require rust protection.”
Schunk Sonosystems’s machines include a sonotrode or welding tip that transfers vibrational energy to the workpiece. Up to two high-strength bolts are required to fix the sonotrode, which is subject to levels of vibration due to the very high frequency used in ultrasonic welding.
The Bumax DX 129 (Duplex stainless steel) is said to offer high tensile strengths of min. 1,200 MPa and fatigue resistance properties. It is expected to deal with the extreme forces during the ultrasonic welding process, such as 20,000 vibrations per second.
The fatigue strength of the Bumax screws allows them to withstand a high number of cycles without fracture. All Bumax bolts are made with European steel and its advanced manufacturing processes further enhance the material’s fatigue resistance properties.
Fatigue fracture often begins with a stress concentration such as inclusions, slags or surface defects. The raw materials Bumax uses, together with the best metallurgical processes and good surface properties, guarantee excellent fatigue strength. Bumax also uses rolled threads rather than cut threads, which is said to further increase fatigue resistance.
