PSI - Issue 76

Vladimír Chmelko et al. / Procedia Structural Integrity 76 (2026) 131–137

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The internal structure is ferritic-pearlitic, influenced by the rolling process. The differences between the microstructures of the analyzed materials are practically imperceptible, whereas the mechanical properties show significant differences.

Yield stress Re (MPa)

Ultimate stress Rm (MPa)

Ductility A (%)

S355

468

544

25

S500

622

697

27

S700

719

823

23

Fig. 2. Tensile diagrams of steel plates and their strength properties.

Significant differences in strength are the result of rolling and crystallization processes. From the point of view of further analysis, the processes of dividing the test samples from the basic rolled sheet metal plate were important, as documented in Fig. 3.

a/

b/

c/

Fig. 3. Comparison of surfaces after material cutting: a/ S355 laser cutting; b/ S500 punching (cold cutting); S700 laser cutting.

3. Experimental results In the first steps of the investigation, the hardness and roughness of these surfaces were measured. The measured hardness values on the surfaces after cutting the material differed significantly, as can be seen in Table 2.