Marine castings are easy to produce carburizing defects. At present, there is no good method to completely solve this defect in China. This is also a reason why many foundry manufacturers dare not go to EPC or go to EPC production line but can not mass produce. The reason for the carburization defect is mainly that the foam material contains carbon, and the foam combustion decomposes the free carbon during pouring, and the carbon invades the molten steel.

Through the test, it is found that there is a certain regularity in the carburization, that is, the surface of the casting is carburized, but the center is hardly carburized; There is no carburization near the ingate, but the farther away from the ingate, the more serious the carburization. The following corresponding measures can make the casting composition basically within the range of process requirements.

(1) It is the key to select foam materials with low carbon content. At present, there are three kinds of materials for EPC, and their carbon content decreases in turn. Among them, EPS is characterized by high carbon content, but its gas generation is small, it is not easy to re spray during pouring, and its price is low. It is widely used in iron castings and steel castings with low requirements.

The steel casting is characterized by low carbon content, large gas generation, easy to cause back spray, and high material price. It is generally used on low-alloy steel. The steel casting has the advantages of both, less gas generation and low carbon content, and is the preferred material for the production of steel castings by EPC.

(2) Taking advantage of the feature that the farther away from the ingate, the more serious the carburization is, a riser is set at the far end from the ingate or at the higher point of the casting, so that the molten steel with serious carburization pollution entering the casting first enters the riser, and the riser also plays the role of slag and gas collection. Using this process, the carbon content of the whole casting can be controlled within the process requirements.

(3) The density of lost foam pattern is very important. As long as the surface is smooth and the density is low, it can bring the benefits of low carbon addition and low gas generation.