Apr 03, 2019
Ductile pipe is a pipe device in a water pipe. Sometimes the ductile iron pipe will shrink and shrink. What is the reason? As a Ductile Iron Pipe Fittings Supplier, let's analyze it.
1. Carbon equivalent: increase the amount of carbon, increase the expansion of graphitization, and reduce shrinkage and shrinkage. In addition, increasing the carbon equivalent can also increase the fluidity of the ductile iron and facilitate the feeding.
2. Phosphorus: The phosphorus content in the molten iron is high, which makes the solidification range expand. At the same time, the low-melting-point phosphorus eutectic can not be replenished during the final solidification, and the casting shell is weakened, so the shrinkage and shrinkage are increased. Propensity.
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. Therefore, the rare earth content should not be too high. Magnesium, on the other hand, is a strongly stable carbide element that hinders graphitization.
4. Wall thickness: When the surface of the casting forms 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, is not good for eliminating shrinkage, shrinkage, so the casting temperature should be reasonably selected according to the specific circumstances, generally 1300 ~ 1350 °C is appropriate.
6. The compactness of the sand type: If the compactness of the sand type is too low or uneven, the phenomenon of cavity expansion will occur under the action of metal static pressure or expansion force after casting, resulting in insufficient shrinkage of the original metal. K Type Joint Ductile Iron Pipe produces shrinkage shrinkage.
7. Casting 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 feeding of the riser. effect.