Features of ladle desulfuration of pipe steel with low sulfur content

At the present time the sulfur content in pipe steel is strictly regulated. Under conditions of PJSC “Magnitogorsk Iron and Steel Works” the metal is smelted in BOF shop with preliminary desulfurization of molten iron, treatment of tapping steel by a solid slag-forming mixture and final desulfurization in the “Ladle-Furnace” unit (LP-unit). In order to increase the efficiency of the sulfur removal process, the influence of the covering slag composition on metal desulfurization is considered. Statistical processing of production data array consisting of 14 melts of steel grade 10Г2ФБЮ with K60 strength class was performed. The dependences of the sulfur content in the metal after desulfurization in the LP-unit on the oxidizing ability, covering slag basicity and the content of magnesium oxide was established: it is shown that the amount of sulfur removed during the ladle treatment process increases with the increase of the covering slag basicity and with the decrease of the magnesium oxide content in slag. For describing this dependence, a new parameter was proposed – the ratio of slag basicity to MgO content in it, %–1. A high content of magnesium oxide in the “white” slag was revealed. This fact indicates a significant amount of converter slag getting into the ladle due to its poor cut-off in the process of metal tapping from the unit. The study of the influence of the coating “white” slag composition on the metal desulfurization process in the LP-unit showed, that for the effective sulfur removal, it is necessary to provide not only welldeoxidized slag with a total content of iron and manganese oxides of less than 1%, but also to ensure the ratio of its basicity to the magnesium content in this slag not less than 0.60–0.65%–1.

Study of Inclusion’s Source and Character in Different T[O] Content

Inclusion’s source and character in different T[ content are studied in the paper, molten slag and refractory material that leave in steel are also calculated. Inclusion in steel are principally come from deoxidation, accompany with the decrease of T[ content, influence of molten slag and refractory materials to inclusions are getting more and more serials. Inclusions which come from molten slag and refractory material are 88.9%, 24.6% and 18.1% defenetly. Great influence on non steady large inclusions in T[ steel, when the mold level fluctuation is large, almost 100% of inclusions in steel have slag inclusion of covering slag. When tundish liquid level fluctuation is large, about 30%~60% inclusions in steel have tundish slag.

Study on Viscosity of Zr-Cu Alloys Based on Viscosity Measurement and Hirai Model

In this paper, the viscosity of molten Zr50Cu50 alloy was measured by using NaF-CaF2 covering slag protection combining rotating cylinder method firstly under non-vacuum melting condition. The curve of viscosity and temperature was acquired stably in the temperature range from 1370K to the liquidus temperature (1208K). According the Arrhenius equation form, the viscosity-temperature relation of molten Zr50Cu50 alloy can be fit as the following equation: （1208K50 alloy can be calculated by the above equation in the range of 1370 to 1208K. The viscosity values of molten Zr50Cu50 alloy calculated by Hirai model are relatively small, so the corrected Hirai model was obtained by the measured viscosity data. The viscosities of molten Zr-Cu alloys can be expressed by the following corrected Hirai model: The viscosities of typical molten Zr-Cu alloys were calculated by the above corrected model. The results showed that the viscosities of Zr-Cu alloys are larger at the respective liquidus temperature. The fundamental data were provided for researching the relationship between viscosities of molten Zr-Cu alloys and amorphous form ability.

New Method for Measuring the Viscosity of the Molten Amorphous Alloy

A new method, covering slag technology combining rotating cylinder method, has been proposed in this paper for measuring the viscosity of the molten amorphous alloy, and the viscosity of molten Zr50Cu50 alloy was measured. Furthermore, the changes of viscous activation energy Ev were analyzed. The measurement results showed: the viscosity of molten Zr50Cu50 alloy increases with decreasing temperature in the range of 1373 to 1208K and there is an overall exponential relationship. Two discontinuous points on the curve of lnη ~1/T have been found. After analyzing the changes of viscous activation energy Ev , the microstructure of molten alloy could be changed. The viscosity of molten Zr50Cu50 alloy is three orders of magnitude higher than that of some other alloys which is closely related with the excellent GFA of Zr50Cu50 alloy.