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1. (WO2011157840) METHOD FOR MANUFACTURING MECHANICAL COMPONENTS MADE OF PARTICULARLY WEAR-RESISTANT AUSTEMPERED SPHEROIDAL CAST IRON

Pub. No.:    WO/2011/157840    International Application No.:    PCT/EP2011/060166
Publication Date: Dec 22, 2011 International Filing Date: Jun 17, 2011
IPC: C22C 33/08
C21D 5/00
Applicants: ZANARDI FONDERIE S.P.A.
ZANARDI, Franco
Inventors: ZANARDI, Franco
Title: METHOD FOR MANUFACTURING MECHANICAL COMPONENTS MADE OF PARTICULARLY WEAR-RESISTANT AUSTEMPERED SPHEROIDAL CAST IRON
Abstract:
A method for manufacturing mechanical components made of spheroidal cast iron, characterized in that it comprises the following steps: - providing a casting of a mechanical cast iron component with a percentage of pearlitic structure greater than 70%, having a carbon content comprised between 2.5% and 4.0%, a silicon content comprised between 1.5% and 3.5%, a manganese content comprised between 0.6% and 1.2%, a molybdenum content comprised between 0% and 1%, and a chromium content comprised between 0% and 0.5%; - bringing the cast iron casting with a percentage of pearlitic structure greater than 70% to a temperature that is higher than the upper austenitization temperature (Ac3) for the time required to obtain a fully austenitic structure; - performing a thermal treatment for interrupted quenching in a salt bath, comprising a step of cooling the mechanical components in a salt bath at a cooling rate that is higher than the critical rate and an isothermal holding step at a temperature comprised between 250 °C and 320 °C for a time comprised between 10 minutes and 60 minutes in order to obtain a matrix comprising metastable unsaturated austenite in a percentage comprised between 40% and 90% of the total.