| 摘要 |
The invention relates to a method for production and forming of cast pieces of spheroidal graphite with improved mechanical properties, comprising the following steps: a) a liquid mixture is prepared with the following weight composition: 3 to 4 % C, 1.7 to 3 % Si, 0.1 to 0.7 % Mn, 0 to 4 % Ni, 0 to 1.5 % Cu, 0 to 0.5 % Mo, with a residual content of Mg according to the thickness of the pieces between 0.025 % and 0.080 % inclusive, the rest being iron and impurities arising during production, said impurities particularly being S, the content of which is less than 0.015 % and P, the content of which is less than 0.10 %; b) said mixture is cast in the liquid state at a temperature between 1350 DEG C and 1550 DEG C inclusive in a mould to give a form of the piece which is called the blank piece; c) said blank piece is extracted from the mould at a temperature Ts between the solid and AR3 temperatures. The solid and AR3 temperatures represent the limiting temperatures for the austenitic domain of said composition; d) the formation of the blank piece is carried out by hot plastic deformation directly in the hot mould to give the piece in the final dimensions and form thereof at a temperature Tf between 1050 DEG C and AR3 inclusive; e) said piece is quenched directly from the temperature of formation to a temperature Tb within the bainitic region and the above is maintained at said temperature Tb for a duration tb and f) said piece is recooled to ambient temperature. The invention further relates to a casting of spheroidal graphite with improved mechanical properties as produced according to the invention.
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