Subject of the thesis are manufacturing, microstructure and properties of thermally joined steel-aluminium hybrid tailored blanks. The joints were produced by using the Cold-Metal-Transfer arc welding process developed by Fronius International. The thickness of the intermetallic phases depends on the heat input rate and is a problem in thermal joining. Due to this problem the nowadays used processes have been designed to keep the formation of intermetallic phases within defined limits or even to prevent them. In this welding-process there is only the aluminium in fluid condition the steel base material is still in solid state. Therefore it is called weld-soldering. By mechanically pulsing the solder wire during the welding process it is, caused by low welding heat, suitable to join such material compounds. Investigations concerning the influence of various solder alloys on the thickness and morphology and the characterisation of the intermetallic layer which is formed in the welding zone were carried out. The determination of the intermetallic layer was made by nano-hardness-measurement and scanning-electron-microscopy as well by a validation with a thermodynamic model. The mechanical properties were tested in quasistatic tension tests.