Recovery of degraded steel 15 128 (according to ČSN) using heat treatment

Kříž Antonín - University of West Bohemia in Pilsen (Czech Republic)

Czech steel, which was developed in the 1960´s, was used in Eastern European countries in the power industry of coal power plants mainly for steam pipelines. This low-alloy steel has a heat resistance of up to 560 °C. At this temperature, it has a service life of 200 000 operating hours. The problem with this refractory CrMoV steel is that its last creep stage shows severe instability and unpredictability in end-of-life behaviour.Therefore, these steels have not found application in power plants in Western Europe. This paper discusses the methodology of a thermal process that restores the degraded steel (operated for 180,000 hours) to its toughness. Due to the heat treatment carried out, the toughness of this steel was recovered. This heat treatment provides the possibility of using the used valves again in the energy industry, without the danger of premature damage and the need to shut down the thermal power plant. The paper discusses the heat treatment carried out, the mechanical properties and the structure obtained

Keywords:
Heat treatment, structure recovery, properties recovery, energy plants, steel 15 128 according to ČSN

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