Patent ID: 6604016
Filing Date: 2003-08-05
Classification: C22C

Abstract:
A process for producing a compacted graphite iron casting, or spheroidal graphite cast iron, requiring a sampling device, means for monitoring temperature as a function of time and a means for administrating structure-modifying agents to a molten cast iron from which said casting is to be produced, said method comprising the steps of:a) for the chosen casting method carrying out the following calibrations: i) determining the amount of structure-modifying agent that has to be added to the melt in order to obtain compacted graphite cast iron, or spheroidal graphite cast iron, as a function of a first control coefficient &ggr;, where &kgr;=(TAmaxâˆ’TAmin)/(TBmaxâˆ’TBmin) â€ƒand wherein TAmax is the local maximum value of the cooling curve recorded at the centre of the sample vessel during solidification of a cast iron sample; TAmin is the local minimum value of the cooling curve recorded at the centre of the sample vessel during solidification of a cast iron sample; TBmax is the local maximum value of the cooling curve recorded at the sample vessel wall during solidification of a cast iron sample; TBmin is the local minimum value of the cooling curve recorded at the sample vessel wall during 'solidification of a cast iron sample; ii) determining the amount of structure-modifying agent that has to be added to the melt in order to obtain compacted graphite cast iron, or spheroidal graphite cast iron, as a function of a second control coefficient &phgr;, where &phgr;=(TAâ€²max)/(TBâ€²max) â€ƒwherein TAâ€²max is the maximum value of the first derivative of the cooling curve recorded at the centre of the sample vessel during solidification of a cast iron sample; and TBâ€²max is the maximum value of the first derivative of the cooling curve recorded at the sample vessel wall during solidification of a cast iron sample; iii) determining the amount of structure-modifying agent that has to be added to a molten cast iron in order to obtain compacted graphite cast iron, or spheroidal graphite cast iron, as a function of a third control coefficient (&sgr;B), which is the area under the first peak of the first derivative of a cooling curve recorded at the sample vessel wall during solidification of a cast iron sample; iv) determining the amount of structure-modifying agent that has to be added to the melt in order to obtain compacted graphite cast iron, or spheroidal cast iron as a function of a fourth control coefficient &kgr;, where: &kgr;=&sgr;A/&sgr;B â€ƒwherein &sgr;A is the area under the second peak of the first derivative of the cooling curve recorded in the centre of the sample vessel; and &sgr;B is the area under the second peak of the first derivative of the cooling curve recorded at the vessel wall; b) during solidification recording cooling curves at the centre of a sample vessel and at the sample vessel wall, respectively, for a particular sample of a molten cast iron; c) calculating control coefficients &ggr;, &phgr;, &rgr;B and &kgr; relating to the temperature time curves obtained in step b) and choosing one of these coefficients &ggr;, &phgr;, &rgr;B and &kgr; giving the most accurate result; d) calculating the amount of stucture modifying agent (Va) that has to be added to the melt; e) add the calculated amount of structure modifying agent; and f) carry out the casting operation in a per se known manner.