PSI - Issue 13

Ulewicz R. et al. / Procedia Structural Integrity 13 (2018) 2164–2169 Ulewicz R., Nový F. , Novák P., Palček P. / Structural Integrity Procedia 00 (2018) 000 – 000

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2. Experimental part 2.1. Material characterization

The Arc-spark OES was used to determine the chemical composition of the draw hook. The results are shown in Tab. 1. The results of the chemical analysis has shown that the examined draw hook was manufactured from the steel grade 47 Mn. the used material is in compliance with the valid national standard describing examined draw hook (TNŽ 28 2612), and detected chemical composition does not exhibit any inadmissible deviation from the standard steel 47 Mn.

Table 1 Chemical composition of the examined draw hook

Max. content of the alloying elements in wt.%

C

Si

Mn

P

S

Cr

Cu

Mo

Ni

V

P+S

Steel 47 Mn standard TNŽ 28 2612

0.60

0.60

1.50

0.050

0.050

0.50

0.25

0.10

0.50

0.10

0.090

Examined draw hook

0.519 1.02 0.999 0.0175 0.0124 0.199 0.0881 0.0157 0.0416 0.0041 0.0299

Basic mechanical properties were evaluated by the standard tensile tests. The tensile tests were performed according the EN 10002-1 standard and the round cross-section specimens were used. Due to the limited amount of the tested material, only two specimens were used. The results of the tensile tests are shown in Table 2. The mechanical properties prescribed in the standard concerning the railway draw hook are shown in Table 3. Comparison of these values with the real mechanical properties of the examined draw hook showed, that the draw hook met all the requirements for the mechanical properties given by the TNŽ 28 2612 standard. It should be pointed out, that the mentioned standard also prescribe the values of the impact toughness, where the minimum value at the +20 °C is K U = 29 J. This value is considerably low and implies the low ductility of the material used for the construction of the railway draw hooks. The microstructural observation revealed the pearlitic-ferritic microstructure of the examined materials (Fig. 1). The microstructure is classified as the fine-grained with the fine spherical inclusions of the Al 2 O 3 type and also a small amount of the small MnS particles was present in the microstructure. Observed microstructure corresponds with the requirements prescribed by the TNŽ 28 2612 standard and suggests that the examined draw hook was annealed after forging. Due to the normalization heat treatment steel shows uniform fine-grained microstructure.

Fig. 1 Fine-grained pearlitic-ferritic microstructure of the examined draw hook fully corresponds with the steel 47 Mn forging after annealing.

Table 2 Basic mechanical properties of the examined draw hook UTS [MPa] YS 0.2 offset [MPa]

Elongation [%]

Reduction of area [%]

Specimen No. 1 Specimen No. 2

784.6 788.1

471.6 482.7

15.08 16.35

45.24 48.34