Analysing the HAZ Softening of S960M by Physical Simulation

The application of the modern high strength steels obtains an important role in automotive industry. In such cases, the thickness of the structural elements can be decreased together with the mass of the structure and the welded joints. In general, we can state that the increasing of the yield strength, the applied thickness decreases, so the amount of the filler material and the time of the welding decrease, as well. On the other hand, it is important to note, that the costs of these steels are two or three times higher than the average steels, furthermore the price of filler materials are even higher, and the weldability of these materials are more complex. At the same time, the typical manufacturing technology is the welding, which – because of the heat input – modifies the original microstructure of the base material. Therefore, different mechanical characteristics (e.g. strength, toughness, hardness distribution) can be achieved, which is not acceptable in many cases in terms of the construction. Consequently, there is great significance of testing the welded joints of these steels, and the development of the suitable manufacturing technology. Accordingly, the properties and the weldability of VOESTALPINE ALFORM 960M (S960M, no standard mark available yet) thermomechanically rolled high strength steel were investigated.