How to Prevent Ductile Iron Castings from Bursting in Winter
The quality of ductile iron castings is generally evaluated by the spheroidization rate.
The more rounded, finer, and evenly distributed graphite, the smaller the splitting effect on the metal matrix. And the smaller the stress concentration caused, the better the performance of ductile iron. Process quality control of ductile iron castings is very important. It is necessary to inoculate and spheroidize the molten iron, do a pre-furnace test, and strictly control the composition. Meanwhile, add appropriate inoculants and nodulizers according to the weight of the molten iron. At the same time, strictly control the pouring time of each ladle of molten iron. Thus in order to prevent graphite decay in the later stage of pouring.
Ductile iron castings are based on mechanical properties as the acceptance criteria. After pouring, sampling for performance tests can promptly find out whether the castings have quality problems. The problems include inoculation, poor spheroidization, or graphite decline. In addition, winter is the season where casting quality problems occur frequently. The low ambient temperature will cause the molten iron to cool too quickly. This will result in supercooled graphite or excessive pearlite. Therefore, we should pay attention to the heat preservation of the casting after casting the molten iron in winter.
Now, let me introduce how to prevent ductile iron from bursting in winter in detail.
The matrix structure of ductile iron parts is mainly included ferrite and pearlite, and a small amount of cementite and phosphorus eutectic as well. Castings with more ferrite content and less pearlite content have good toughness and low strength. Otherwise, the castings have high strength and poor toughness.
Many equipments and objects are also repellent to winter, and ductile iron castings are also a typical one. What is the threat to ductile iron castings in winter? In fact, the main problem is that ductile iron parts will explode in a low temperature environment. The temperature in winter will definitely be lower, but this will not affect the performance of ductile iron parts themselves. It is mainly because of the special composition of the object that it has both good toughness and steel strength. Therefore, it is also ideal in terms of elongation, and it can operate normally even at low temperatures.
However, the fluid medium in the ductile iron parts will not be able to withstand the threat of low temperature. And under this circumstances the castings may burst. In order to avoid such problems, if the critical point of the fluid is relatively low, we can add some antifreeze appropriately. Or take proper heat preservation treatment for ductile iron castings. Those preventions are effective.
If you want to solve the problem at the source, you can also choose a ductile iron material with a better low-temperature anti-freezing material from the beginning. However, the requirements and conditions for the technical process are very harsh. Yet the investment cost will be relatively high. Thus this must be carefully considered.