2017-Sustainable Industrial Processing Summit
SIPS 2017 Volume 9. Iron and Steel, Metals and Alloys
| Editors: | Kongoli F, Conejo A, Gomez-Marroquin MC |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2017 |
| Pages: | 242 pages |
| ISBN: | 978-1-987820-77-5 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Research of Applying Rare-Earth Metals to Improve the Quality of Transport Steels
Leonid Smirnov1;1, Ekaterinburg, Russian Federation;
Type of Paper: Regular
Id Paper: 78
Topic: 2
Abstract:
Analysis of the non-metal inclusions forming in the case of the adding of rare-earth metals in high-carbon steels for transport applications and the evaluation of the treatment effect on their mechanical properties were performed.
Experimental high-carbon steels were produced under follow schedules:
I – EAF – LF – VD – continuous-cast-slab – rolled rails;
II – LD – LF – RH – round continuous-cast-slab – rolled steel for wheels.
Alloy (63,5-66,8 % Ce, 32,9-36,1 % La) was used for modification of steel during the ladle treatment before and after degassing. The specimens for determining of inclusions composition were collected from the ladle and from rolled rail and wheel before and after degassing. Scanning electron microscope JEOL JSM-5900 LV with X-ray spectrometer INCA Energy 250 with zooms from 100 to 4000 and MIRAZ TESCAN with zoom up to 15000 were applied for examination of the inclusions.
It has been established that the composition and quantity of inclusions in the case of steel modification with REM depend on the time point of the adding of REM and on the technology of deoxidizing and adding of carbon during the ladle treatment. If the deoxidizing of steel with aluminum and the treatment with silicocalcium was not applied then in the case of modification with REM Ce and La oxysulfides with variable composition was formed mainly. These inclusions may contain impurities of Ca and primary oxide inclusion elements or do not contain them. In the case of aluminum-alloying steel treatments with REM and with silicocalcium are combined, the Ca, Ce and La oxysulfides, Al, Ce and La complex oxides and Ca sulfides was main kinds of inclusions. The size of majority of inclusions did not exceed 5-6 micrometers. The modification of steel with REM decreased the quantity of oxide inclusions in the steel.
In case of the quantity of dispersed REM inclusions is increased, the narrowing of pouring nozzle may occurs without the inclusion deposition on the refractory, which obviously is related to that the temperature gape of the crystallization is decreased. Furthermore the declining of inhomogeneity level of cast slabs and structure refinement should be noted.
In the terms of the chemical composition the experimental rails may be referred to rails for general purpose. After heat treatment under schedule developed for rails for general purposes the experimental rails showed higher toughness at a temperature +20 C and higher cross section reduction after tensile test.
After the heat treatment under schedule developed for low-temperature rails the experimental rails meet the requirements for this type of rails. But the commercialized steel for low-temperature rails contains more nickel and fewer carbon to meet the toughness requirements.
The essential deference between the microstructure of rail steel modified with REM and current steel was not observed. The main structural constituent is dispersed lamellar perlite with scattered regions of ferrite in the borders of perlite fields. The modification of steel had not influenced on the structure parameters. It may be concluded that higher toughness and plasticity of experimental rails are caused by the lower quantity of non-metal inclusions.