Abstract
The effect of hydrogen content of iron melt on pinholing in calcium-treated iron castings cast in green sand moulds has been investigated. The melt from a cupola was transferred into a ladle, where the melt was desulfurized by calcium carbide and sodium flouride. After inoculation and calcium treatment in a hand shark, the melt was poured into a test mould. In the mould, a disk and a riser were connected to a symmetrical gating system. The disk was 100mm in diameter and 6mm thick and was used as a pinhole test specimen. Samples for hydrogen determination were taken from the melt in the riser. Three types of test moulds were used. Each had a different shape of gating system and were designated as mould No.1, mould No.2, and mould No.3, respectively. The design of mould No.2 and mould No.3 were modeled after mould No.1. The gating system of mould No. 2 was designed to restrain the turbulence of the stream of the melt as much as possible. On the other hand, the gating system of mould No. 3 was designed to bring out the turbulence. When either mould No.1 or mould No.2 was used, the number of pinholes increased with the increase in the hydrogen content of the melt as shown in Fig. 1. In particular, an almost linear relation between the number of pinholes and the hydrogen content was obtained when mould No.2 was used. A large number of pinholes and blowholes were observed regardless of the hydrogen content when mould No.3 was used. The change in the hydrogen content of the melt during the previously mentioned treatment was examined, and the hydrogen content was found to increase by the addition of the desulferizer almost up to the same values as those in the riser.
