Title

EVALUATING THE EFFECT OF TUNDISH FLOW MODIFIER ON THE CLEANLINESS OF A CARBURIZING STEEL FOR GEARS

EVALUATING THE EFFECT OF TUNDISH FLOW MODIFIER ON THE CLEANLINESS OF A CARBURIZING STEEL FOR GEARS

Authorship

SOUZA, ELIAS DE OLIVEIRA CAMPOS; SILVA, ANDRÉ LUIZ VASCONCELLOS DA COSTA E

SOUZA, ELIAS DE OLIVEIRA CAMPOS

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SILVA, ANDRÉ LUIZ VASCONCELLOS DA COSTA E

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DOI

10.5151/2594-5300-42340

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Abstract

The automotive industry demands increasingly longer fatigue lives, improved wear resistance, and good machinability for gears. This requires significant cleanliness improvements in steel melt shops. This study compares inclusion populations in the final product. We tested the use of a tundish flow modifier versus no modifier. While most efforts to achieve clean steel and engineer residual inclusions are made before the steel reaches the tundish, controlling flow conditions within the tundish has been identified as a measure that may still reduce, under certain conditions, the population of inclusions in the final product. Using automatic SEM procedures (ASPEX) and conventional metallography, the evolution of the inclusion population in the four casting conditions was characterized. The results indicate that a significant reduction of the amount of Al2O3.MgO in the size larger than 5µm, and Calcium Aluminates inclusions in all the size range was achieved for the heat H2. A large among of Al2O3 inclusions larger than 15µm was observed in heat H2. Notably, CaS inclusions were only observed in heat H2. The reasons for these results are discussed based on the possible thermodynamics effects. Some speculations on the possibilities of further improvements are discussed

THE AUTOMOTIVE INDUSTRY DEMANDS INCREASINGLY LONGER FATIGUE LIVES, IMPROVED WEAR RESISTANCE, AND GOOD MACHINABILITY FOR GEARS. THIS REQUIRES SIGNIFICANT CLEANLINESS IMPROVEMENTS IN STEEL MELT SHOPS. THIS STUDY COMPARES INCLUSION POPULATIONS IN THE FINAL PRODUCT. WE TESTED THE USE OF A TUNDISH FLOW MODIFIER VERSUS NO MODIFIER. WHILE MOST EFFORTS TO ACHIEVE CLEAN STEEL AND ENGINEER RESIDUAL INCLUSIONS ARE MADE BEFORE THE STEEL REACHES THE TUNDISH, CONTROLLING FLOW CONDITIONS WITHIN THE TUNDISH HAS BEEN IDENTIFIED AS A MEASURE THAT MAY STILL REDUCE, UNDER CERTAIN CONDITIONS, THE POPULATION OF INCLUSIONS IN THE FINAL PRODUCT. USING AUTOMATIC SEM PROCEDURES (ASPEX) AND CONVENTIONAL METALLOGRAPHY, THE EVOLUTION OF THE INCLUSION POPULATION IN THE FOUR CASTING CONDITIONS WAS CHARACTERIZED. THE RESULTS INDICATE THAT A SIGNIFICANT REDUCTION OF THE AMOUNT OF AL2O3.MGO IN THE SIZE LARGER THAN 5µM, AND CALCIUM ALUMINATES INCLUSIONS IN ALL THE SIZE RANGE WAS ACHIEVED FOR THE HEAT H2. A LARGE AMONG OF AL2O3 INCLUSIONS LARGER THAN 15µM WAS OBSERVED IN HEAT H2. NOTABLY, CAS INCLUSIONS WERE ONLY OBSERVED IN HEAT H2. THE REASONS FOR THESE RESULTS ARE DISCUSSED BASED ON THE POSSIBLE THERMODYNAMICS EFFECTS. SOME SPECULATIONS ON THE POSSIBILITIES OF FURTHER IMPROVEMENTS ARE DISCUSSED

Keywords

Steel cleanliness, Tundish flow modifier, Non-metallic inclusions, Carburizing steel.

Steel cleanliness, Tundish flow modifier, Non-metallic inclusions, Carburizing steel