Crack problem of lost foam steel casting parts

ZHY casting’s senior engineer team was lucky to participate in the preparation of a new lost steam Steelcasting production line. In the later stage, as the main technical force of the permanent casting branch of Beijing coal machinery casting, it presided over and participated in the commissioning of the new casting. After more than half a year’s exploration and practice, the new casting is basically on the right track, although there are still some problems, But the future is still bright.

The causes of casting cracks, the practical ideas to solve the crack problem and the final solution are written out to discuss with you and make progress together.

Lost foam casting put the foam model with refractory layer in the sand box. The model is surrounded by dry sand or self hardening sand. The high temperature molten metal dissolves the foam pyrolysis when pouring, and occupies the space of the model exit, and finally the casting method of the casting is obtained. Compared with traditional casting, lost foam casting has the advantages of high casting precision, flexible design, good production environment and low operation cost. However, no process is perfect. At this stage, there are still various defects that affect the quality of castings.

The key to ensure the quality of lost steam casting is to avoid all kinds of casting defects. The new lost steam steel casting production line will inevitably have all kinds of quality problems. Often the quality problem of castings is affected by many factors. It is of little significance to discuss only one problem, which must be supplemented by multivariable comprehensive analysis of process conditions.

The causes of quenching and tempering cracks of castings are carburization, slag inclusion and porosity. The chemical composition of steel castings is the key to determine the material properties, and the carbon content has the most direct impact on the properties. Most of the lost foam models are flammable polyethylene foams. When molten steel is replaced by foam, the incomplete foam is left in the casting, which increases the carbon content and leads to carburizing.

Carburization will lead to the disqualification of the chemical composition of the casting. The specific performance is: the casting has high hardness and difficult processing; The uneven internal and external chemical composition of the casting leads to the increase of internal stress, and cracks are easy to appear in the quenching and tempering treatment of the casting. The industry generally believes that the lost foam casting production process is not suitable for cast steel, especially low carbon steel.

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