Stephan Kallee was born in Tübingen in 1965 as son of the university professor Ekkehard Kallee and his wife Barbara Kallee, neé Weigmann. He learned Latin and Greek at the Uhland-Gymnasium in Tübingen, where he gained the abitur in 1985. He served as engine technician on the auxiliary ship Tender Main.
He studied mechanical engineering at the Technical University of Munich. After studies on elastohydrodynamic lubrication and laser-specific design of a car door, he wrote his diploma thesis about flexible and compliant systems in laser material processing. After obtaining his diploma, he became an International Welding Engineer at SLV Munich.
In May 1995, he started his career as Project Leader at TWI (The Welding Institute) in Cambridge, UK. He specialised in solid phase welding, i.e. welding without melting. He used proceses such as friction stir welding, rotary friction welding and linear friction welding. As Collaborative Project Manager he managed EC funded projects such as LinFric® (1.36 Mio €), EuroStir® (8.8 Mio €) and STEQ™[#]. As Sector Manager he worked until September 2008 in business development in the automotive, railway, ship building, heavy engineering and aerospace sectors.
Since November 2008, he worked as Senior Sales Manager for 7½ years at PSTproducts GmbH in Alzenau. He focussed on the industrial application of the electromagnetic pulse techncology for welding, forming, crimping and cutting of metals. He also provided consultancy to companies, which wanted to invest in robotic MIG/MAG welding cells.
Since 2016, he was CSO of Stirtec GmbH in Premstätten near Graz in Austria and managed the sales of friction stir welding machines, friction stir spot welding guns, manufacturing cells, tools and manufacturing services. The company offers complete solutions from application development and prototyping until industrial production, especially for joining dissimilar materials.
Since 2018 he is a self-employed technical consultant for welding technology and sales of welding machines and the transport industry.