Regularities of Cementite Decomposition in Hypereutectoid Steels

Comprehensive studies have been carried out and the main regularities of cementite decomposition during thermocyclic processing of carbon-based hypereutectoid steels have been established.

TRIBOLOGICAL PROPERTIES OF HIGH CARBON STEELS IN AN AS-CAST STATE AND AFTER PLASTIC DEFORMATION

The aim of the study was to conduct dry sliding tests on the designed hypereutectoid steels with the controlled contents increase of carbon, chromium, and manganese. Chromium and manganese were used to balance the changes related to the higher secondary carbides’ precipitation in the chemical composition of the matrix. Samples were investigated by the use of the block on disk friction method under the load of 100 N. The duration of each test was 2000 s with the wear track length approx. 500 m. The samples were investigated in the as-cast state and after hot plastic deformation. Two sets of four samples were prepared from the ingots and plastically deformed material. The heat treated (quenched and tempered) 100Cr6 steel was used as the counter-sample, with a new counter-sample used for each test. The obtained results show a decrease of the average friction coefficient for samples after plastic deformation. The phenomena that influenced this effect the most, observed in the alloy with the higher concentration of alloying elements, were grain boundary net defragmentation of secondary carbides and the elimination of Widmannstaten needles. The main wear mechanisms occurring during the tribological tests were sliding wear and material spalling.

Innovative Prozesskette zur UHC-Bauteilfertigung/Innovative process chain for manufacturing ultra-high-carbon component - High performance manufacturing process for an economical serial production of lightweight steel

Der Einsatz dichtereduzierter Leichtbau-Stahlwerkstoffe in bewegten Motorenkomponenten, wie Pleuel oder Kolbenbolzen, können zu einer signifikanten CO2-Einsparung beitragen. Dennoch fehlen innovative Fertigungsverfahren für eine wirtschaftliche Bauteilfertigung von hochfesten übereutektoiden Stählen. Mithilfe spezieller Herstellungsrouten kann der Werkstoff zielgerichtet für die Umformung und anschließende Zerspanung eingestellt werden. Angepasste Werkzeuge führen zur deutlichen Steigerung der Produktivität.   The use of density-reduced lightweight steel in moving engine components, like connecting rods or piston pins, could lead to a significant carbon dioxide reduction. Nevertheless innovative manufacturing technologies for the economical component production of high-strength hypereutectoid steels are not provided. With special production routes this material could purposively settle in the forming and cutting. Optimised cutting tool-systems induce to an extensive increase in productivity.