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Abstract

In the paper the reasons for steam pipeline’s elbow material rupture, made of steel 13CrMo4-5 (15HM) that is being used in the energetics.

Based on the mechanical properties in the ambient temperature (Rm, Rp0,2 and elongation A5) and in the increased temperature (Rp0,2t

) it

was found, that the pipeline elbow’s material sampled from the ruptured area has lower Rp0,2 i Rp0,2t by around 2% than it is a requirement

for 13CrMo4-5 steel in it’s base state. The damage appeared as a result of complex stress state, that substantially exceeded the admissible

tensions, what was the consequence of considerable structure degradation level. As a result of the microstructure tests on HITACHI S4200

microscope, the considerable development of the creeping process associates were found. Also the advances progress of the microstructure

degradation was observed, which is substantial decomposition of bainite and multiple, with varied secretion size, and in most cases

forming the micro cracks chains. With the use of lateral micro sections the creeping voids were observed, that creates at some places the

shrinkage porosities clusters and micro pores.

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Authors and Affiliations

A. Mesjasz
J. Piątkowski
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Abstract

The results of tests and examinations of the microstructure and mechanical properties of cast steel used for large-size slag ladles are presented. Castings of this type (especially large-size ladles with a capacity of up to 16 m3) operate under very demanding conditions resulting from the repeated cycles of filling and emptying the ladle with liquid slag at a temperature exceeding even 1600°C. The changes in operating temperature cause faster degradation and wear of slag ladle castings, mainly due to thermal fatigue.
The tests carried out on samples taken from different parts/areas of the ladle (flange, bottom and half-height) showed significant differences in the microstructure of the flange and bottom part as compared to the microstructure obtained at half-height of the ladle wall. The flange and bottom were characterized by a ferritic-pearlitic microstructure, while the microstructure at the ladle half-height consisted of a ferritic matrix, cementite and graphite precipitates. Changes in microstructure affected the mechanical properties. Based on the test results it was found that both the flange and the bottom of the ladle had higher mechanical properties, i.e. UTS, YS, hardness, and impact energy than the centre of the ladle wall. Fractography showed the mixed character of fractures with the predominance of brittle fracture. Microporosity and clusters of non-metallic inclusions were also found in the fractures of samples characterized by low properties.
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Authors and Affiliations

Barbara Kalandyk
ORCID: ORCID
R. Zapała
1
ORCID: ORCID
S. Sobula
1
ORCID: ORCID
Grzegorz Tęcza
ORCID: ORCID
K. Piotrowski
2
ORCID: ORCID

  1. AGH University of Science and Technology, Department of Cast Alloys and Composite Engineering, Faculty of Foundry Engineering, 23 Reymonta Str., 30-059 Krakow, Poland
  2. Krakodlew S.A., 1 Ujastek Str., 30-969 Krakow, Poland

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