Abstract
During brazing of austenitic stainless steel with copper based brazing material a common failure occurs, namely that the brazing material solutes along grain boundaries, which looks like cracks. This unfortunate effect occurred when AISI 304 and 310 steels are brazing. To avoid this unwanted effect - since the cracks propagate mainly on high angle grain boundaries - our goal was to enhance the number of special coincident site lattice type grain boundaries with thermomechanical treatment. Experiments were performed for 1, 48 and 72 hour heat treatments on materials cold rolled at different levels. After the thermomechanical treatment significant decrease in the crack size was found in depth and width, respectively.
Highlights
Corrosion resistant and stainless steels are widely used in the industry
If AISI 304 steel is brazed with Boehler SG-CuSi3 brazing material, long intercrystalline cracks occur in the steel, full with copper (Fig. 1)
The grain boundaries which have a given fraction of atoms in the grain boundary plane which are coincident to both lattices separated by the grain boundary are characterized by the Coincident Site Lattice (CSL) model [5]
Summary
Corrosion resistant and stainless steels are widely used in the industry. Austenitic stainless steels, one group of such steels are often applied in the automotive industry [1]. Brazing is a fast and efficient way for joining such parts for low mechanical loads, for example in the case of exhaust systems of cars For such applications, AISI 304 stainless steel is widely used due to the combination of good mechanical properties and excellent corrosion resistance over a large temperature range. On the other hand there are so called special boundaries having values for specific parameter(s) which are very different from the values of the random boundaries. The grain boundaries which have a given fraction of atoms in the grain boundary plane which are coincident to both lattices separated by the grain boundary are characterized by the Coincident Site Lattice (CSL) model [5] These boundaries are classified in terms of values. The frequency of 3 and 3n type CSL-boundaries is much higher than that of other CSL-boundaries and they play an important role in the tun-
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