The requirements of suspension springs for the automotive industry are increasing with regard to cleanness and strength. In order to meet this high quality level a remarkable quality improvement was obtained within the last years due the introduction of a very strict ladle metallurgy together with a controlled stirring in ladle and an optimized steel flow pattern in the tundish. The production of Saarstahl is characterized by a very strict ladle metallurgy which includes also a RH degassing. In addition special attention was paid within this ongoing quality improvement programme to the removal of inclusions due to the optimization of steel flow pattern in ladle and tundish. A remarkable improvement of both castability and cleanness was obtained by the introduction of the Si deoxidation in stead of the Al one avoiding the detrimental effect of high melting Ca aluminates on the fatigue properties. Nowadays the Si killed SiCr steel fulfils all stringent requirements of the automotive industry. In such a way the production of spring steels and particularly of Si killed SiCr steels of Saarstahl AG could be raised from 5000 t/a in 1993 up to nearly 100000 t/a in 2004, at the same time it was possible to reduce the rejections to a very low level. A further improvement will be strived by the application of the soft reduction technique and an advanced equipment on the new billet continuous casting machine S0 with a strand size of 150 mm square. In addition the installation of the new modern walking beam furnace in the rolling mill in combination with a special heating, rolling and cooling programme will improve the fine internal structure of the wire rod.
Evaluation of the cleanness of SiCr-spring steels for suspension springs
Bewertung des Reinheitsgrads von SiCr-Federstählen für Aufhängungsfedern
2005
10 Seiten, 16 Bilder, 6 Quellen
Conference paper
English
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