What are the factors that affect the shrinkage rate of casting parts?

Casting is a method to solve the shrinkage and loosening defects of castings, which plays an important role in the industry. The shrinkage rate of castings will affect the efficiency of metal hot working. What is shrinkage? The percentage of casting size shrinkage is called casting line shrinkage or casting shrinkage. When manufacturing the mold, the mold should be expanded according to the determined shrinkage rate of the casting to ensure that the size of the casting after cooling meets the requirements. So, what are the factors that affect the shrinkage rate of castings? Let's take a look.

1 Casting structure is complex, not easy to shrink, reduce the shrinkage of the casting. For example, cast steel structures with the same composition have different shapes and higher shrinkage rates when freely contracted.

2. Casting material. Different castings have different casting shrinkage rates. For example, the shrinkage rate of cast steel is greater than that of gray cast iron. When the sulfur content of gray cast iron is high, the shrinkage rate increases, and when the silicon content increases, the shrinkage rate decreases.

3. Casting parts franchising. Mold franchise is good, casting shrinkage rate increased. For example, the shrinkage of wet and sodium silicate sand castings is higher than that of dry castings. In addition, as the size of the casting increases, the mold degrades and changes, and the shrinkage rate of the casting decreases. Therefore, the shrinkage rate of the casting should be selected according to the actual situation. For castings that require accurate dimensions, the shrinkage rate of the test cast should be corrected.

For the same casting, due to structural reasons, its axis. Radial or length. The width. High shrinkage rates in the three directions may not be consistent. For castings that require more accurate dimensions, different shrinkage rates should be provided in each direction. In actual production, general castings, especially small castings, use the same shrinkage rate in all directions. Although it will cause some errors, the errors are usually not large, which is convenient for the processing and manufacturing of the mold.