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What factors are easy to affect the performance of nodular cast iron
Spheroidal graphite is obtained by spheroidization and inoculation treatment, which effectively improves the mechanical properties of cast iron, especially the plasticity and toughness, so as to obtain higher strength than carbon steel.
Ductile iron castings are currently used in many major industrial sectors, which require high strength, plasticity, toughness, wear resistance, severe thermal and mechanical impact resistance, high or low temperature resistance, corrosion resistance and dimensional stability.
Do you know what factors will affect the performance characteristics of ductile iron? Now nodular iron manufacturers are coming to tell you:
1. Pouring riser and cold iron
If the pouring system, riser and chiller are not properly set, the metal liquid cannot be guaranteed to solidify in sequence; In addition, the number and size of the riser and the connection with the casting will affect the feeding effect of the riser.
2. Phosphorus
The high phosphorus content in liquid iron expands the solidification range, and the low melting point phosphorus eutectic can not be supplied during solidification, and makes the casting shell weaker, so there is a tendency to increase shrinkage cavity and porosity. General plant control phosphorus content is less than 0 08%.
3. Rare earths and magnesium
Too much residual rare earth will deteriorate the shape of graphite and reduce the nodulation rate, so the content of rare earth should not be too high. Magnesium, in turn, is a strongly stable carbide element that prevents graphitization. It can be seen that the amount of residual magnesium and residual rare earth will increase the white mouth tendency of ductile iron and reduce the expansion of graphite. Therefore, when their content is high, it will also increase the shrinkage porosity and porosity tendency.
4. Wall thickness
When a hard shell is formed on the surface of the casting, the higher the temperature of the metal liquid inside, the greater the liquid shrinkage, and the volume of shrinkage cavity and porosity not only increases in absolute value, but also increases in relative value. In addition, if the wall thickness changes too suddenly, the isolated thick section can not be filled, so that the shrinkage cavity and porosity tend to increase.
5. Temperature
High pouring temperature is conducive to feeding, but too high will increase the amount of liquid shrinkage, which is unfavorable to the elimination of shrinkage cavity and porosity, so the pouring temperature should be selected reasonably according to the specific situation, generally 1300 ~ 1350℃ is appropriate.
6. Compactness of sand mold
If the compactness of sand mold is too low or uneven, the cavity will expand after pouring under the action of metal static pressure or expansion force, resulting in insufficient reinforcement of the original metal and resulting in shrinkage and porosity of the casting.
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