A general term for ductile iron mainly composed of iron, carbon and silicon. In these alloys, the carbon content exceeds the amount retained in the austenite solid solution at the eutectic temperature. A general term for an alloy of iron, carbon and silicon. In these alloys, the carbon content exceeds the amount retained in the austenite solid solution at the eutectic temperature.
Ductile iron has medium and high strength, medium toughness and plasticity, high comprehensive performance, good wear resistance and vibration damping, and good casting process performance. It can be changed by various heat treatments. Mainly used in various power machinery crankshafts, connecting shafts, connecting rods, gears, clutch plates, hydraulic cylinders and other components as well as ductile iron flower pot and ductile iron garden pole.
Ductile iron has good mechanical properties. As long as the ductile iron garden light poles control the manufacturing process during the casting process and controls the quality defects of the casting, the manufactured casting will have good machinery in use. Strength, wear resistance in use.
In the manufacturing process, the casting is a material having a certain shape, size and performance obtained by pouring, injecting, inhaling or other casting methods into a pre-prepared mold, cooling, and so on. Castings are mainly used as blanks for machine parts.
The spheroidal graphite cast iron resin sand casting process is a molding method that can cure the sand mold at normal temperature without baking or hardening gas. The casting has a smooth surface, sharp edges and corners, high dimensional accuracy, high molding efficiency, and resin sand type (core). High strength, good formability, low gas generation compared with other organic molds, good thermal stability, good gas permeability, can greatly reduce casting defects such as sand, sand, sand, pores, shrinkage, cracks, etc. Make complex pieces and key pieces.
Factors affecting ductile iron:
(1) pouring riser and cold iron: if the pouring system, riser and cold iron are improperly set, the molten metal cannot be solidified in sequence; in addition, the number and size of the riser and the connection with the casting will not affect the filling of the riser. Shrink effect.
(2) Phosphorus: The phosphorus content in the iron liquid is too high, so that the solidification range is expanded, and the low-melting-point phosphorus eutectic crystals are not replenished at the final solidification, and the casting shell is weakened, so that the shrinkage cavities and shrinkage are increased. The tendency to produce. The general plant control phosphorus content is less than 008%.
(3) Rare earth and magnesium: If the residual amount of rare earth is too high, the graphite shape will be deteriorated and the spheroidization rate will be lowered, so the rare earth content should not be too high. Magnesium, on the other hand, is a strongly stable carbide element that hinders graphitization. It can be seen that the amount of residual magnesium and the amount of residual rare earth increase the tendency of the white iron of the ductile iron to decrease the expansion of the graphite, so when their content is high, the tendency of shrinkage and shrinkage is also increased.
(4) Wall thickness: When the surface of the casting is formed into a hard shell, the higher the temperature of the internal molten metal, the larger the liquid shrinkage, and the volume of shrinkage and shrinkage not only increases the absolute value, but also increases the relative value. In addition, if the wall thickness changes too suddenly, the isolated thick section cannot be replenished, and the tendency to cause shrinkage shrinkage increases.
(5) Temperature: high pouring temperature is conducive to feeding, but too high will increase the amount of liquid shrinkage, which is unfavorable for eliminating shrinkage and shrinkage. Therefore, the pouring temperature should be reasonably selected according to the specific conditions, generally 1300~1350 °C is suitable. .
(6) The compactness of the sand type: If the compactness of the sand type is too low or uneven, the phenomenon of cavity expansion occurs under the action of metal static pressure or expansion force after casting, so that the original metal is not enough to be fed. This causes the casting to produce shrinkage and shrinkage.
(7) Carbon equivalent: increase the amount of carbon, increase the graphitization expansion, and reduce shrinkage and shrinkage. In addition, increasing the carbon equivalent can also increase the fluidity of the ductile iron and facilitate the feeding. The empirical formula for producing high quality castings is C% + 1/7 SI% > 39%. However, when increasing the carbon equivalent, the ductile iron should not cause other defects such as graphite floating.
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