Saarstahl AG (Völklingen, Germany):

R. Thome, Dr. Eng., R&D Manager, Vontinuous Casting Innovations, e-mail: ralf.thome@saarstahl.com
K.-G. Doppler, Dr. Nat. Sci., Director of Innovation Dept.
M. Bleymehl, Mag. Eng., Head of Quality Dept.
M. Zimmer, Mag. Eng., Technical Customer Service

This report highlights a number of examples showing the quality improvement from the cast billet and bloom to the finished product when using mechanical soft reduction (MSR) in comparison to the application of conventional processes. Regarding the bearing steel grade 100Cr6, the carbon segregation level was decreased by 62% and the center porosity was reduced by 94% in the as-cast condition. As a consequence the formation and distribution of carbides in wire and balls made from soft reduction material were equivalent to those made from ingot casting and those found in balls installed in wheel bearings of different passenger cars. In the case of the quenched and tempered steel grade 42CrMoS4, MSR led to a segregationless structure in the bloom center with distinctly lower and more uniform distribution of the alloying elements, especially carbon, sulgur and phosphorus. The size and fraction of sulfides were reduced and a more even sulfide distribution was found in the central fiber of forged components. For the cold forging steel grade C4C which is used for the manufacture of brake pistons, the application of soft reduction led to a significant decrease of center porosity in the as-cast billet and as a result to a decline of the average rejection rate in ultrasonic testing of the bars of approx. 82%. Sumarized, the improved quality and structure of the examined blooms, billets and final components produced via the MSR route and the more cost-eff ective way in production off ers the possibility to fulfil the increasing demands of the automotive and forging industry for better performance of the components and reduced costs.

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