Precision welded steel tubes are being widely used in automotives on account of its easy fabricability and lower cost. Thermal processing is very often used to modify the properties of steel tubes. Three grades of microalloyed steels are taken for the investigation. Three types of thermal processing namely, Induction hardening & tempering, Intercritical hardening and recovery annealing are independently carried out on these three steel grades. Microstructure and mechanical properties characterization are carried out. Three kind of microstructures ferrite - pearlite, martensite and dual phase are analyzed and linking these micro constituents with fatigue properties for these microalloyed welded steel tubes have been carried out. Thermal processing in welded steel tubes provide an opportunity to develop high strength steel tubes. Tensile strength ranges from 500 MPa to 1600 MPa with elongation of 10% to 30% are achieved through the three thermal processing methods.  The advantages of thermal processing in welded steel tubes with respect to designing light weight components are discussed in this paper.