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Fatigue tests on notched specimens of G20Mn5QT cast steel and life prediction by a new strain-based method

Han Qinghua, Wang Yaru, Yin Yue, Zhang Song

Archives of Civil and Mechanical Engineering

2020

Vol. 20, no. 4

221--236

Fatigue performance of notched specimens of G20Mn5QT cast steel was investigated experimentally and analytically. Fatigue tests on a total number of 22 semi-circular notched specimens were conducted with the load ratios of − 1 and 0.1. Nominal stress-fatigue life relationship was obtained, and mean stress correction rules were verified for the notched specimens based on the test results. A new strain-based approach, strain field intensity (SNFI) method, was proposed, in which fatigue life of materials is predicted based on the weighted average strain in the fatigue damage region. The fatigue lives of the test specimens were predicted using three strain-based approaches, modified Neuber’s rule, equivalent strain energy density (ESED) method and the proposed SNFI method. The fatigue life prediction by the SNFI method was in very good agreement with the test results, which verified the rationality and applicability of the proposed SNFI method and also the adopted fatigue properties of G20Mn5QT cast steel. Both the modified Neuber’s rule and the ESED method gave conservative prediction of the fatigue life of the notched specimens. The necessity of the 3-dimensional fatigue damage region was also discussed for the proposed SNFI method.

The Use of Barium and Calcium Alloys in the Ladle Furnace Treatment of Selected Grades of Continuously Cast Steels

Derda W., Lawenda P., Pardela P.

Archives of Metallurgy and Materials

2015

Vol. 60, iss. 1

281--288

The subject of the paper are the results of laboratory and industrial investigations into the use of Si - Ca - Ba alloys for modifying non-metallic inclusions. Based on laboratory tests, the morphology and chemical composition of non-metallic inclusions in carbon steel were examined before and after refining with the use of the above-mentioned alloy as a refining addition. In particular tests, variable additions of the alloy were used at a constant refining time and temperature. Comparison of the process of casting of a sequence of seven heats of the same steel grade using the stopper system in the tundish was made under industrial conditions. In these heats, additions of Si - Ca (three heats) and Si - Ca - Ba (four heats) were introduced as a non-metallic inclusion modifier in the form of core wires during the process in the ladle furnace. For the investigated heats, the contents of total oxygen and calcium were assayed in the finished steel. A significant effect of the simultaneous addition of barium and calcium on steel castability, and thus on the process of continuous casting of the investigated heats, was found.

Przedmiotem opracowania są wyniki badań laboratoryjnych oraz przemysłowych, dotyczących zastosowania stopów Si - Ca - Ba do modyfikacji wtrąceń niemetalicznych. Na podstawie badań laboratoryjnych zbadano morfologię i skład chemiczny wtrąceń niemetalicznych w stali węglowej przed i po rafinacji przy zastosowaniu ww. stopu w charakterze dodatku rafinacyjnego. W poszczególnych próbach zastosowano zmienne dodatki stopu przy stałym czasie i temperaturze rafinacji. W warunkach przemysłowych dokonano porównania przebiegu odlewania sekwencji siedmiu wytopów tego samego gatunku stali z zastosowaniem układu zatyczkowego w kadzi pośredniej. W wytopach tych podczas procesu w piecu kadziowym wprowadzono w charakterze modyfikatora wtrąceń niemetalicznych dodatki Si - Ca (trzy wytopy) oraz Si - Ca - Ba (cztery wytopy) w postaci drutów rdzeniowych. Dla badanych wytopów w gotowej stali oznaczono zawartości tlenu całkowitego oraz wapnia. Stwierdzono istotny wpływ jednoczesnego dodatku baru i wapnia na lejność stali, a tym samym na przebieg ciągłego odlewania badanych wytopów.