Abstract
Type, relative concentration and size of most characteristic non-metallic inclusions for the elements of rails (head, web) from electro-steel of E79KhF and E90KhАF grades were determined on the basis of metallographic (with a microscope “OLYMPUS GX-51”) and spectral (using spectrometer “ARL iSpark” method “Spark-DAT”) analyses. It was found that the highest relative concentration of manganese sulfides (MnS) is 30.8 – 43.4 ppm. At the same time, 60 – 100 % of inclusions of this type are of small sizes (less than 4 μm), and it does not allow them to be detected using standard metallographic analysis with 100-fold magnification. The revealed high relative concentration of sulfide inclusions directly correlates with the established positive sulfur liquation in considered rail elements, which is up to 40 %. Despite the high concentration of manganese sulfides, their influence on the quality of rails can be considered not dangerous, taking into account their high ductility during hot deformation and the established prevalence of inclusions of this type with small size (less than 4 μm). Among inclusions of a silicate type, SiO2 inclusions (3.4 – 14.9 ppm) have a significant concentration. All detected inclusions of this type have a size not exceeding 4 μm. It was found that the concentration of complex inclusions containing alumina (Al2O3 – CaO – MgO, Al2O3 – CaO – MgO – CaS, Al2O3 – CaO, Al2O3 – MgO) is insignificant: in total it does not exceed 3.1 ppm and 1.6 ppm for individual types. The concentration of corundum (Al2O3) is also insignificant and does not exceed 0.3 ppm. In this case, alumina inclusions of small size (less than 6 μm) prevail. Due to the low contamination (taking into account the relative concentration and size of inclusions) with non-plastic silicate and alumina non-metallic inclusions, their influence on the quality of the rails was not significant. It is confirmed by the absence of defects detected during ultrasonic testing.
Highlights
Relative concentration and size of most characteristic non-metallic inclusions for the elements of rails from electro-steel of E79KhF and E90KhАF grades were determined on the basis of metallographic and spectral analyses
The revealed high relative concentration of sulfide inclusions directly correlates with the established positive sulfur liquation in considered rail elements, which is up to 40 %
Экспериментальные исследования пластичности и сопротивления деформации хромистых рельсовых сталей // Изв
Summary
В качестве объекта исследований использованы пробы, отобранные от головки и шейки годных (прошедших ультразвуковой контроль) рельсов текущего производства плавок сталей Э76ХФ и Э90ХАФ. Исследования неметаллических включений проводили с использованием оптического микроскопа «OLYMPUS GX-51» методом стандартного полуколичественного анализа по ГОСТ 1778 – 70 и с использованием спектрометра «ARL iSpark» методом «Spark-DAT». Методика Spark-DAT (Spark Data Analysis and Treat ment) позволяет определить вид, концентрацию и распределение неметаллических включений по размерам. В рамках указанной методики на первом этапе применен метод «Стандартного анализа включений», в котором количество включений определяется как количество пиков отдельного элемента или как совпадение пиков различных элементов. Для определения концентрации некоторых специфических видов включений (таких как алюминаты, сульфиды и силикаты) использован метод «Расширенного анализа включений» в качестве предустановленной модели. Химический состав образцов определяли методами спектрального анализа с использованием спектрометра «ARL iSpark». Распределение неметаллических включений по элементам годных рельсов текущего производства Table 1. Distribution of nonmetallic inclusions by elements of suitable rails of the current production
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