PSI - Issue 13

Milan Uhríčik et al. / Procedia Structural Integrity 13 (2018) 1571 – 1576 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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b

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Fig. 1. Microstructures of (a) AISI 304; (b) AISI 316L; (c) AISI 316Ti.

In the microstructures there are a lot of non-metallic inclusions based on MnS (Fig. 2), which have a spherical shape. Sulfur causes brittleness, reduces toughness and fatigue life of steel. Its adverse effect is reduced by addition of manganese, which has a greater affinity to sulfur and produces manganese sulfide. This sulfide is formed during the hot forming process, when it is plastically transformed in the process in the rolling direction and in the microstructure that creates a visible texture. To identity of the chemical composition of manganese sulfide a surface RTG microanalysis was used. A typical presence of annealing twins can be observed in the structure. In AISI 316Ti are present titanium carbides TiC, which are orange color and angular shape (Fig. 3).

Fig. 2. Surface RTG microanalysis of manganese sulfide, MnS – mapping.

Fig. 3. Surface RTG microanalysis of titanium carbide, TiC – mapping.

3. Measurement of internal damping

Measurement of internal damping dependence on temperature was performed on austenitic steels AISI 304, AISI 316L and AISI 316 Ti, in the initial state and after the deformation. The experimental equipment, used at Department of Materials E ngineering, University of Žilina, consists from mechanical and electronical part. The mechanical part (Fig. 4) consists of three basic parts: the transducer, this serves like the source and at the same time like the detector of ultrasonic waves, the rod, which is made of titanium and has a cylindrical shape with a diameter of 12 mm. Its function is to isolate the heat from the test specimen, which is heated in a furnace and the transducer then maintains at a constant room temperature. The last part of device is the specimen. Dimensions and shape of the test bar are