| 摘要 |
A process for producing castings from nodular graphite iron with an austenitic-bainitic mixed microstructure is proposed. A melt with the usual quantities of silicon, carbon, phosphorus, sulphur, magnesium, if appropriate copper and if appropriate nickel as well as additional quantities of less than 0.3% of manganese and 0.2 to 0.8% of molybdenum is used in this case. The casting is heated to an austenitisation temperature of 800 to 870@C and held at this temperature up to austenitisation. It is then brought, within less than 2 minutes, from the austenitisation temperature zone into the bainitisation temperature zone, cooled therein to a bainitisation temperature of 350 to 400@C and held at this temperature for a time corresponding to the desired bainite content. In order to achieve a high elongation and toughness while also ensuring a high yield strength required for reducing the weight of components, and a hardness which is particularly appropriate for machining, it is provided that the casting is held for preferably 60 to 120 minutes at the austenitisation temperature, brought from the austenitisation temperature limit into the bainitisation temperature zone within less than one minute and held for 60 to 120 minutes at the bainitisation temperature.
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